Documents

Overview of Keysight's Advanced Power System family Video Demo

keysight — Tue, 09 Nov 2021 17:07:16 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:07:16 PM

The Advanced Power System (APS) family consists of 1 kW and 2 kW system DC power supplies that deliver a new level in power supply performance enabled by Keysight's exclusive VersaPower architecture. The APS family was designed to help you overcome your toughest power test challenges by delivering industry-leading specifications and innovative features in an integrated solution for advanced ATE power testing needs.

To view the demo video click the following link: https://www.youtube.com/watch?v=PJCUBDpzr3w&index=1&list=PL2XuMA5AwNUwePFCpNCrfeGJPPIG-SqKm

For more information on the Keysight's APS Product Family visit: www.keysight.com/find/APS

Tags: test, Data Sheets, current, keysight, n8900, systems, voltage, autoranging, n7900, n6900, supply, dc, power, ate

What happens if remote sense leads open?

keysight — Tue, 09 Nov 2021 17:06:26 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:26 PM

This post and other great tips and tricks for Keysight Power Products can be found on the Watt's Up? blog.

For more information on Keysight Power Products visit: www.keysight.com/find/power

Wednesday, October 31, 2012

What happens if remote sense leads open?

Remote sense is a feature on many power supplies that allows the power supply to regulate its output voltage right at your load (“remotely”) instead of at the power supply output terminals. Use remote sense when you want to compensate for load lead voltage drop caused by load current flowing in your load leads. This is accomplished by using a pair of remote sense leads that are in addition to your load leads. See an example in Figure 1. The power supply uses the voltage across the remote sense lead terminals to sense (measure) the voltage at the load terminals and regulate the voltage directly across the load by adjusting the output terminal voltage. Refer to this post I wrote last year on remote sense:
http://powersupply.blogs.keysight.com/2011/08/use-remote-sense-to-regulate-voltage-at.html

Remote sense leads could be accidentally left open, or once connected, one or both leads could inadvertently become open. I have had users of our power supplies testing very expensive devices under test (DUTs) ask me what would happen to the output voltage if a sense lead wired in a system opened; they were worried about subjecting their very expensive DUT to excessive voltage.

To understand why this is an important consideration, it is necessary to better understand the role of the sense leads. To regulate its output voltage, a power supply uses internal circuitry that acts as a feedback loop. The voltage is set to a particular value and the feedback loop monitors (measures) the voltage across the sense terminals and compares it to the setting. If it is too low, the loop circuitry increases the output voltage. If it is too high, the loop circuitry decreases the output voltage. So the actions of this loop result in the output voltage settling (being regulated) at a value such that the sense lead voltage equals the voltage set point.

If one or both of the sense leads is open, the feedback loop is broken and incorrect voltage information is sent to the loop. With an open sense lead, the sense voltage is typically near zero. The loop thinks the output voltage is too low and responds by increasing the output voltage. But this does not result in a corresponding increase in the sense lead voltage since the wire is broken so the loop increases the output voltage more. This continues until the value is increased to the maximum amount possible, which is usually somewhat higher than the maximum rated voltage of the power supply and very much beyond the desired set point. This could easily damage the DUT!

The scenario described in the previous paragraph is what would happen if no action was taken to prevent a runaway output voltage due to an open sense lead. Keysight power supplies have an internal circuit, called open sense protection, that prevents the output voltage from rising significantly above the set voltage if one or both of the remote sense leads is open. In fact, with one or both sense leads open, the output voltage of most Keysight power supplies will rise only 1 or 2 percent above the setting. Additionally, some Keysight power supplies can detect an open sense lead and respond by shutting down the output and alerting the user by changing a bit in a status register.

Note that this open sense protect circuitry is in addition to and independent from the over-voltage protection (OVP) circuitry common on most Keysight power supplies. OVP is a setting that is separate from the output voltage setting. If the actual output voltage exceeds the OVP setting, the OVP will shut down the output to protect the DUT.

Tags: current, keysight, remote_sense, voltage, power_supply, Application Notes, supplies, dc, power, n6700

What is a bipolar power supply?

keysight — Tue, 09 Nov 2021 17:06:26 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:26 PM

This blog post and other great tips and tricks for Agilent Power Products can be found on the Watt's Up? blog.

For more information on Keysight Power Products visit: www.keysight.com/find/power

Friday, October 26, 2012

What is a bipolar (four-quadrant) power supply?

To answer this question, I have to start with a basic definition of polarity conventions. Figure 1 shows a simple diagram of a power supply (a two-terminal device) with the standard polarity for voltage and current. A standard power supply typically is a source of power. To source power, current must flow out of the positive voltage terminal. Most power supplies source energy in this way by providing a positive output voltage and positive output current. This is known as a uni-polar power supply because it provides voltage with only one polarity. By convention, the “polarity” nomenclature typically refers to the polarity of the voltage (not the direction of current flow).

If current flows into the positive voltage terminal, the power supply is sinking current and is acting like an electronic load – it is absorbing and dissipating power instead of sourcing power. Most power supplies do not do this although many Agilent power supplies can sink some current to quickly pull down their output voltage when needed – this is known as a down-programmer capability – see this post for more info: http://powersupplyblog.tm.agilent.com/2012/03/if-you-need-fast-rise-and-fall-times.html.

To fully define power supply output voltage and current conventions, a Cartesian coordinate system is used. The Cartesian coordinate system simply shows two parameters on perpendicular axes. See Figure 2. By convention, the four quadrants of the coordinate system are defined as shown. Roman numerals are typically used to refer to the quadrants. For power supplies, voltage is normally shown on the vertical axis and current on the horizontal axis. This coordinate system is used to define the valid operating points for a given power supply. A graph of the boundary surrounding these valid operating points on the coordinate system is known as the power supply’s output characteristic.

As mentioned earlier, some power supplies are uni-polar (produce only a single polarity output voltage), but can source and sink current. These power supplies can operate in quadrants 1 and 2 and can therefore be called two-quadrant supplies. In quadrant 1, the power supply would be sourcing power with current flowing out of the more positive voltage terminal. In quadrant 2, the power supply would be consuming power (sinking current) with current flowing into the more positive voltage terminal.

Some power supplies can provide positive or negative voltages across their output terminals without having to switch the external wiring to the terminals. These supplies can typically operate in all four quadrants and are therefore known as four-quadrant power supplies. Another name for these is bipolar since they are able to produce either positive or negative voltage on their output terminals. In quadrants 1 and 3, a bipolar supply is sourcing power: current flows out of the more positive voltage terminal. In quadrants 2 and 4, a bipolar supply is consuming power: current flows into the more positive voltage terminal. See Figure 3.

Agilent’s N6784A is an example of a bipolar power supply. It can source or sink current and the output voltage across its output terminals can be set positive or negative. It is a 20 W Source/Measure Unit (SMU) with multiple output ranges. See Figure 4 for the output characteristic of the N6784A.

To summarize, a bipolar or four-quadrant power supply is a supply that can provide positive or negative output voltage, and can source or sink current. It can operate in any of the four quadrants of the voltage-current coordinate system.

Tags: sink, current, bipolar, voltage, power_supply, source, Application Notes, dc, power, n6700

Power Supply Resolution versus Accuracy

keysight — Tue, 09 Nov 2021 17:06:24 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:24 PM

This and other great tips and tricks on Power Products can be found on Keysight's Watt's Up? blog.

For more information on Keysight Power Products visit: www.keysight.com/find/power

Power Supply Resolution versus Accuracy

One of the questions that we have received on the support team quite a few times and something that confused me when I started at Keysight is the concept of our resolution supplemental characteristic versus our accuracy specification. I sat down with my colleague Russell and we wanted to do a simple explanation of the differences.

If you look at our power supply offering, there is always an accuracy specification and a resolution supplemental characteristic for both programming and measurement. For the purposes of this blog post, we are going to look at the programming accuracy (0.06% + 19 mV) and programming resolution (3.5 mV) of the N6752A High Performance DC Power Module. Please note that these same explanations apply to the measurement side as well but for the sake of brevity we will be sticking to programming in our example.

Let’s start by talking about resolution. Our power supplies use Digital to Analog Converters (DACs) to take the user inputted settings and convert them to analog signals that set a programming voltage that will interact with the control loop of the power supply to set the output. The resolution supplemental characteristic represents one single count of the DAC. This is also known as the Least Significant Bit (LSB). What this means for our end user is that the smallest step they can make between two settings on the unit is the programming resolution number. In our example, the N6752A can be set to 0.9975 V, 1.001 V, 1.0045 V, etc. These are all multiples of 3.5 mV and any setting that falls between two DAC counts will be put into the nearest count. If the user tried to set the N6752A to 1 V, the power supply will actually be set to 1.001 V since that is the nearest count. This is also known as quantization error.

The accuracy specification always includes an error term for the quantization error. This is typically half of the resolution supplemental characteristic. The accuracy specification also includes many other factors such as DAC accuracy, DAC linearity, offset error of operational amplifiers, gain errors of the feedback loops, and temperature drift of components. The accuracy will always be worse than the resolution since it includes all of the factors listed above as well as the term for the quantization error. You can definitely see this in the N6752A where the resolution is 3.5 mV and just the offset of the accuracy specification not including the gain term is 19 mV which is more than 5 times greater than the resolution.

Tags: current, keysight, selection, accuracy, resolution, tip, voltage, power_supply, Application Notes, dc, power, specifications, features

Tips to prevent voltage droop from tripping low voltage detection circuits

keysight — Tue, 09 Nov 2021 17:06:23 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:23 PM

This and other great tips and tricks can be found on Keysight's Watt's Up? Blog.

More information on Keysight Power Products can be found at: www.keysight.com/find/power

Thursday, January 31, 2013

Tips to prevent voltage droop from tripping low voltage detection circuits

There are many battery operated devices such as cell phones, hand-held two-way radios, and portable GPS’s that have low voltage detection circuits. These circuits are designed to prevent the device from trying to operate at battery voltages that are below a safe value for reliable operation of the internal circuitry. Voltage supplied by a battery located very close to the circuitry drawing current from it remains fairly rigid even when the device draws pulses of current which is often the case. However, during testing of the device, a power supply is frequently used to power the device instead of the battery. Voltage supplied by a power supply, typically located quite a distance from the circuitry drawing current, will often momentarily droop each time a positive edge of current is drawn. This momentary voltage droop can cause an undesired trip of the low voltage detection circuit in the device interrupting the test.

Here are some tips to reduce voltage droop caused by fast current changes on the output voltage of a power supply.

Shorten wires from power supply to DUT (device under test)

Wires have resistance (R) and inductance (L), both of which develop voltage across them when a current pulse flows through the wire. Shortening the length of wire will reduce the voltage drop developed across the R and L, reducing the droop at the DUT.

Use larger diameter wire from the power supply to the DUT

Larger diameter wire will have lower R, reducing the voltage developed across it when current flows

Install multiple runs of the same wire in parallel

Parallel wires will have lower R and lower L, again reducing the voltage developed across them when current flows

Lower the inductance of the wire

Tightly twist the plus and minus power supply output wires together
Never allow the power supply plus and minus output wires to become separated. This will substantially increase the inductance, increasing voltage drop with current, especially if the current changes quickly (V = L * dI/dt). Simply placing the wires next to each other is much better than letting them fall freely, but twisting them together is highly recommended over tightly coupling them without twisting. See example results shown below.
Add multiple wires in parallel
As mentioned earlier, adding multiple wires in parallel reduces inductance. The best method to use here is to twist pairs of plus and minus wires together, and then run each twisted set separately to the DUT (bundling the twisted sets together is not as effective as keeping the sets separated).
Use a low inductance cable
Some cables are designed specifically to have low inductance. Goertz wire is one example. Also, Temp-Flex makes low inductance cable. These types of wire can drastically lower the inductance in the path between your power supply and your DUT, greatly reducing voltage droop that occurs with current transients. However, these cables tend to be expensive.

Eliminate connectors

Remove as many connectors as possible between the power supply output and DUT. When current flows through a connector, voltage is dropped across the connection points.

Use a power supply with a low output impedance

Some power supply vendors publish output impedance graphs. Try to use one with the lowest output impedance possible. Current pulses drawn from a power supply with lower output impedance will drop less voltage than a power supply with higher output impedance.

Add low ESR capacitors at the power supply output

You can reduce the effective output impedance of your power supply by adding a low ESR (equivalent series resistance) cap right at the output of your power supply. Many power supplies already have output caps and fairly low output impedance, so this will help only if the caps you choose actually help to lower the overall output impedance.

Add low ESR capacitors right at the DUT

When current is demanded by the DUT, having a local cap right at the DUT to provide the current will greatly reduce the voltage drop on the wire running to the DUT. This is because the required current comes from the cap and does not have to flow through the wire where it would drop voltage. It is important to choose caps with low ESR. Otherwise, when the current flows out of the cap, the voltage will again droop due to the current dropping voltage across the ESR.

If you are having trouble with voltage droop due to fast current changes, each of the above tips will help to contribute to reducing the droop. If the droop is large, it is unlikely you will be able to use just one technique from above to fix it. Most likely, you will have to implement many if not all of the methods above to get the best performance possible from your test setup.

Below is a simple example showing measured droop differences when using three different wiring techniques: free falling wire, loosely coupled wire, and twisted wire. An Keysight N6751A power supply with 10 feet of 10AWG wire running between it and an Keysight 6063B electronic load was used. The N6751A was set for 5 V with a current limit of 5 A, and the load was set to switch between 1 A and 3 A with a rise time of about 10 us. Remote sense was used on the power supply, sensing at the load input. A current probe captured the current (lower waveforms) and the voltage droop was measured (upper waveforms) at the load input which was at the end of the 10 feet of wire.

You can see the voltage droop was reduced as the wires became better coupled, lowering their inductance. The droop measured 1.7 V with the wires free falling. This droop was reduced significantly to 0.84 V with loosely coupled wire. Further reduction in droop was observed when the wires were twisted: the droop measured 0.69 V.

Many of the concepts presented here are explored further in a paper co-authored several years ago by one of our other Watt’s Up? blog authors, Ed Brorein. Here is a link to that paper: http://www.keysight.com/upload/cmc_upload/All/EPSG083914.pdf

Tags: keysight, tip, voltage, power_supply, Application Notes, supplies, dc, power, n6700

Can a standard DC power supply be used as a current source?

keysight — Tue, 09 Nov 2021 17:06:18 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:18 PM

This blog post and other great tips and tricks on Keysight's power products can be found on the Keysight Watt's Up? Blog.

For more information on Keysight Power Products visit: www.keysight.com/find/power

Friday, April 27, 2012

Can a standard DC power supply be used as a current source?

The quick answer to this question is, yes, most standard DC power supplies can be used as current sources. However, this question deserves more attention, so what follows is the longer answer.

Most DC power supplies can operate in constant voltage (CV) or constant current (CC) mode. CV mode means the power supply is regulating the output voltage and the output current is determined by the load connected across the output terminals. CC mode means the power supply is regulating the output current and the output voltage is determined by the load connected across the output terminals. When operating in CC mode, the power supply is acting like a current source. So any power supply that can operate in CC mode can be used as a current source (click here for more info about CV/CC operation).

Is a standard power supply a good current source?

An ideal current source would have infinite output impedance (an ideal voltage source would have zero output impedance). No power supply has infinite output impedance (or zero output impedance) regardless of the mode in which it is operating. In fact, most power supply designs are optimized for CV mode since most power supply applications require a constant voltage. The optimization includes putting an output capacitor across the output terminals of the power supply to help lower output voltage noise and also to lower the output impedance with frequency. So the effectiveness of a standard power supply as a current source will depend on your needs with frequency.

At DC, a power supply in CC mode does make a good current source. Typical CC load regulation specifications support this notion (click here for more info about load regulation). For example, an Keysight N6752A power supply (maximum ratings of 50 V, 10 A, 100 W) has a CC load regulation specification of 2 mA. This means that the output current will change by less than 2 mA for any load voltage change. So when operating in CC mode, a 50 V output load change will produce a current change of less than 2 mA. If we take the delta V over worst case delta I, we have 50 V / 2 mA = 25 kΩ. This means that the DC output impedance will always be 25 kΩ or more for this power supply. In fact, the current will likely change much less than 2 mA with a 50 V load change making the DC output impedance in CC mode much greater than 25 kΩ.

Of course, a power supply’s effectiveness as a current source should be judged by the output impedance beyond the DC impedance. See the figure below for a graph of the N6752A CC output impedance with frequency:

If the graph continued in the low frequency direction, the output impedance would continue to rise as a “good” current source should. At higher frequencies, the CC loop gain inside the product begins to fall. As the loop gain moves through unity and beyond, the output capacitor in the supply dominates the behavior of the output impedance, so at high frequencies, the output impedance is lower. So how good the power supply is as a current source depends on your needs with frequency. The higher the output impedance, the better the current source. The output impedance also correlates to the CC transient response (and to a much lesser extent, the output programming response time).

The bottom line here is that in most applications, a standard DC power supply can be used in CC mode as a current source.

Tags: current, keysight, tips, voltage, Application Notes, dc, power, n6700

If you need fast rise and fall times for your DUT power, use a power supply with a downprogrammer

keysight — Tue, 09 Nov 2021 17:06:10 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:10 PM

This and other great power products tips and tricks can be found on the Watt's Up? Blog.

If you need fast rise and fall times for your DUT power, use a power supply with a downprogrammer

If you have to provide DC power to a device under test (DUT) and you want the voltage fall time to be just as fast as the rise time, use a power supply with a downprogrammer. A downprogrammer is a circuit built into the output of a power supply that actively pulls the output voltage down when the power supply is moving from a higher setting to a lower setting. Power supplies are good at forcing their output voltage up since that is what their internal circuitry is designed to do. This design results in fast rise times. However, when the supply’s output is changed to move down in voltage, the power supply’s output capacitor (and any additional external DUT capacitance) will need to be discharged. Without a downprogrammer, if there is a light load or no load on the output of the power supply, there is nowhere for the current from the output cap to flow to discharge it. This scenario causes the voltage to take a long time to come down resulting in slow fall times. And this behavior leads to longer test times since you will have to wait for the output voltage to settle to the lower value before you can proceed with your test.

The figures below show an example of the output voltage rise and fall times of a power supply without a downprogrammer under light load conditions. You can see the short rise time (tens of milliseconds) and longer fall time (several seconds).

One of my colleagues, Bob Zollo, wrote an article on this topic that appeared in Electronic Design on February 7, 2012. Here is a link to the article:

http://electronicdesign.com/article/test-and-measurement/If-Your-Power-Supply-Needs-Fast-Rise-And-Fall-Times-Try-A-Down-Programmer-64725

A power supply without an active downprogrammer can have fall times that are tens to hundreds of times longer than a power supply with a downprogrammer. If your test requires you to have fast fall times for your DUT power, or your test requires you to frequently change the voltage on your DUT (both up and down) and throughput is an issue for you, make sure the power supply you choose has a downprogrammer – you won’t have to wait as long for the voltage to move from a higher value to a lower value.

Tags: current, capabilities, application, tips, modular_power_supply, battery, voltage, modular, demo, demonstration, Application Notes, dc, power, n6700, agilent

What Is Going On When My Power Supply Displays “UNREG”?

keysight — Tue, 09 Nov 2021 17:06:09 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:09 PM

This and other great tips and tricks can be found on the Watt's Up? Blog.

What Is Going On When My Power Supply Displays “UNREG”?

Most everyone is familiar with the very traditional Constant Voltage (CV) and Constant Current (CC) operating modes incorporated in most any lab bench or system power supply. All but the most very basic power supplies provide display indicators or annunciators to indicate whether it is in CV or CC mode. However, moderately more sophisticated power supplies provide additional indicators or annunciators to provide increased insight and more information about their operating status. One annunciator you may encounter is seeing “UNREG” flash on, either momentarily or continuously. It’s fairly obvious that this means that the power supply is unregulated; it is failing to maintain a Constant Voltage or Constant Current. But what is really going on when the power supply displays UNREG and what things might cause this?

To gain better insight about CV, CC and UNREG operating modes it is helpful to visualize what is going on with an IV graph of the power supply output in combination with the load line of the external device being powered. I wrote a two part post about voltage and current levels and limits which you may find useful to review. If you like you can access it from these links levels and limits part 1 and levels and limits part 2. This posting builds nicely on these earlier postings. A conventional single quadrant power supply IV graph with resistive load line is depicted in Figure 1. As the load resistance varies from infinity to zero the power supply’s output goes through the full range of CV mode through CC mode operation. With a passive load like a resistor you are unlikely to encounter UNREG mode, unless perhaps something goes wrong in the power supply itself.

Figure 1: Single quadrant power supply IV characteristic with a resistive load

However, with active load devices you have a pretty high chance of encountering UNREG mode operation, depending where the actual voltage and current values end up at in comparison to the power supply’s voltage and current settings. One common application where UNREG can be easily encountered is charging a battery (our external active load device) with a power supply. Two different scenarios are depicted in Figure 2. For scenario 1, when the battery voltage is less than the power supply’s output, the point where the power supply’s IV characteristic curve and the battery’s load line (a CV characteristic) intersect, the power supply is in CC mode, happily supplying a regulated charge current into the battery. However, for scenario 2 the battery’s voltage is greater than the power supply’s CV setting (for example, you have your automobile battery charger set to 6 volts when you connect it to a 12 volt battery). Providing the power supply is not able to sink current the battery forces the power supply’s output voltage up along the graph’s voltage axis to the battery’s voltage level. Operating along this whole range of voltage greater than the power supply’s output voltage setting puts the power supply into its UNREG mode of operation.

Figure 2: Single quadrant power supply IV characteristic with a battery load

A danger here is more sophisticated power supplies usually incorporate Over Voltage Protection (OVP). One kind of OVP is a crowbar which is an SCR designed to short the output to quickly bring down the output voltage to protect the (possibly expensive) device being powered. When connected to a battery if an OVP crowbar is tripped, damage to the power supply or battery could occur due to batteries being able to deliver a fairly unlimited level of current. It is worth knowing what kind of OVP there is in a power supply before attempting to charge a battery with it. Better yet is to use a power supply or charger specifically designed to properly monitor and charge a given type of battery. The designers take these things into consideration so you don’t have to!

I have digressed here a little on yet another mode, OVP, but it’s all worth knowing when working with power supplies! Can you think of other scenarios that might drive a power supply into UNREG? (Hint: How about the other end of the power supply IV characteristic, where it meets the horizontal current axis?)

Tags: current, keysight, application, tips, modular_power_supply, voltage, modular, demo, low, demonstration, Application Notes, dc, power, n6700, 6030a

Protect your DUT with power supply features including a watchdog timer

keysight — Tue, 09 Nov 2021 17:06:09 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:09 PM

This and other great power products tips and tricks can be found on the Watt's Up? Blog.

Protect your DUT with power supply features including a watchdog timer

The two biggest threats of damage to your device under test (DUT) from a power supply perspective are excessive voltage and excessive current. There are various protection features built into quality power supplies that will protect your DUT from exposure to these destructive forces. There are also some other not-so-common features that can prove to be invaluable in certain applications.

Soft limits

The first line of defense against too much voltage or current can be using soft limits (when available). These are maximum values for voltage and current you can set that later prevent someone from setting output voltage or current values that exceed your soft limit settings. If someone attempts to set a higher value (either from the front panel or over the programming interface), the power supply will ignore the request and generate an error. While this feature is useful to prevent accidentally setting voltages or currents that are too high, it cannot protect the DUT if the voltage or current actually exceeds a value due to another reason. Over-voltage protection and over-current protection must be used for these cases.

Over-voltage protection

Over-voltage protection (OVP) is a feature that uses an OVP setting (separate from the output voltage setting). If the actual output voltage reaches or exceeds the OVP setting, the power supply shuts down its output, protecting the DUT from excessive voltage. The figure below shows a power supply output voltage heading toward 20 V with an OVP setting of 15 V. The output shuts down when the voltage reaches 15 V.

Some power supplies have an SCR (silicon-controlled rectifier) across their output that gets turned on when the OVP trips essentially shorting the output as quickly as possible. Again, the idea here is to protect the DUT from excessive voltage by limiting the voltage magnitude and exposure time as much as possible. The SCR circuit is sometimes called a “crowbar” circuit since it acts like taking a large piece of metal, such as a crowbar, and placing it across the power supply output terminals.

Over-current protection

Over-current protection (OCP) is a feature that uses the constant current (CC) setting. If the actual output current reaches or exceeds the constant current setting causing the power supply to go into CC mode, the power supply shuts down its output, protecting the DUT from excessive current. The figure below shows a power supply output current heading toward 3 A with a CC setting of 1 A and OCP turned on. The power supply takes just a few hundred microseconds to register the over-current condition and then shut down the output. The CC and OCP circuits are not perfect, so you can see the current exceed the CC setting of 1 A, but it does so for only a brief time.

The OCP feature can be turned on or off and works in conjunction with the CC setting. The CC setting prevents the output current from exceeding the setting, but it does not shut down the output if the CC value is reached. If OCP is turned off and CC occurs, the power supply will continue producing current at the CC value basically forever. This could damage some DUTs as the undesired current flows continuously through the DUT. If OCP is turned on and CC occurs, the power supply will shut down its output, eliminating the current flowing to the DUT.

Note that there are times when briefly entering CC mode is expected and an OCP shutdown would be a problem. For example, if the load on the power supply has a large input capacitor, and the output voltage is set to go from zero to the programmed value, the cap will draw a large inrush current that could temporarily cause the power supply to go into CC mode while charging the cap. This short time in CC mode may be expected and considered acceptable, so there is another feature associated with the OCP setting that is a delay time. Upon a programmed voltage change (such as from zero to the programmed value as mentioned above), the OCP circuit will temporarily ignore the CC status just for the delay time, therefore avoiding nuisance OCP tripping.

Remote inhibit

Remote inhibit (or remote shutdown) is a feature that allows an external signal, such as a switch opening or closing, to shutdown the output of the power supply. This can be used for protection in a variety of ways. For example, you might wire this input to an emergency shutdown switch in your test system that an operator would use if a dangerous condition was observed such as smoke coming from your DUT. Or, the remote inhibit could be used to protect the test system operator by being connected to a micro switch on a safety cover for the DUT. If dangerous voltages are present on the DUT when operating, the micro switch could disable DUT power when the cover is open.

Watchdog timer

The watchdog timer is a unique feature on some Keysight power supplies, such as the N6700 series. This feature looks for any interface bus activity (LAN, GPIB, or USB) and if no bus activity is detected by the power supply for a time that you set, the power supply output shuts down. This feature was inspired by one of our customers testing new chip designs. The engineer was running long-term reliability testing including heating and cooling of the chips. These tests would run for weeks or even months. A computer program was used to control the N6700 power supplies that were responsible for heating and cooling the chips. If the program hung up, it was possible to burn up the chips. So the engineer expressed an interest in having the power supply shut down its own outputs if no commands were received by the power supply for a length of time indicating that the program has stopped working properly. The watchdog timer allows you to set delay times from 1 to 3600 seconds.

Other protection features that protect the power supply itself

There are some protection features that indirectly protect your DUT by protecting the power supply itself, such as over-temperature (OT) protection. If the power supply detects an internal temperature that exceeds a predetermined limit, it will shut down its output. The temperature may rise due to an unusually high ambient temperature, or perhaps due to a blocked or incapacitated cooling fan. Shutting down the output in response to high temperature will prevent other power supply components from failing that could lead to a more catastrophic condition.

One other way in which a power supply protects itself is with an internal reverse protection diode across its output terminals. As part of the internal design, there is often a polarized electrolytic capacitor across the output terminals of a power supply. If a reverse voltage from an external power source was applied across the output terminals, the cap (or other internal circuitry) could easily be damaged. The design includes a diode across the output terminals with its cathode connected to the positive terminal and its anode connected to the negative terminal. The diode will conduct if a reverse voltage from an external source is applied across the output terminals, thereby preventing the reverse voltage from rising above a diode drop and damaging other internal components.

Tags: current, application, tips, modular_power_supply, battery, voltage, modular, demo, demonstration, Application Notes, dc, power, n6700, 6030a, agilent

Fine Tuning the FPGA Power-on Process

keysight — Tue, 09 Nov 2021 17:06:08 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:08 PM

This and other great measurement tips and tricks can be found on the General Purpose Electronics Test Equipment Blog

Monday, March 26, 2012

Fine Tuning the FPGA Power-on Process

Powering on an FPGA can be careful balancing act of proper sequencing and slew rate timing on multiple power supply inputs. Some of the reasons for this balancing act is to ensure the power-on-reset circuit is not tripped, to ensure proper operation of the PLL, and to minimize in-rush current which is especially important in low power applications. In this post we will look at how modern multiple output power supplies can be used for fine tuning the FPGA turn-on process with an emphasis on minimizing in-rush current.

Modern multiple output power supplies have three features that make them a valuable tool for tuning the FPGA turn-on process, they are:

Adjustable output sequencing feature that allows the users to setup the turn-on time for each of the power supply's outputs.
Slew rate adjustment to specify the rise time at turn-on for each power supply output.
Output current and voltage digitizers for capturing the in-rush current, spotting voltage sags, etc.

The modern multiple output power supply comes into the FPGA circuit design process before implementing the power distribution system for the circuit. Use the modern multiple output power supply to tune the sequencing turn-on timing and slew rate to find the ideal turn-on conditions for the FPGA circuit. While tuning the turn on timing, the power supply measurement digitizers are used to measure the resulting voltage and the resulting in-rush current at turn-on. After the tuning process, the power distribution system can be designed and setup to achieve the ideal sequence and slew rate timing established earlier with the modern multiple output power supply.

Let's look at a quick example using a low power FPGA circuit that is going into a portable battery powered device. The engineer designing the power distribution system for the FPGA circuit wants to keep power usage to a minimum, which includes tuning the power turn-on conditions such that in-rush current is kept to a minimum amount while ensuring proper turn-on of the circuit. To tune the power turn-on conditions the engineer is using Keysight's N6705B DC Power Analyzer as the modern multiple output power supply. The N6705B is a modular power supply that supports up to 4 outputs. The N6705B has output sequencing, slew rate control, and output measurement digitizers along with a scope like display to analyze the digitized measurements.

The FPGA circuit under test has four supply inputs. The engineer sets each of the N6705B outputs according to the specified ranges of the FPGA. A test run was done to verify the sequencing and slew rate of the power supply outputs. The result was captured on the N6705B's display and it can be seen in the below figure.

V1, V2, and V3 were all used for powering the FPGA. V4 was used for other components in the circuit. V1 is the FPGA's core supply and that is where we want to measure the in-rush current. Using the timing parameters shown in the above figure, the in-rush current on the core supply was captured and is shown in the figure below.

As you can see in the figure the in-rush current consists of two spikes. The first is just over 1 ms with a flat top and the second is a higher current shorter duration spike. After the in-rush current, the low power FPGA's standby static current settles to about 15 mA. The engineer then did a number of tuning iterations of the same test. At each iteration the sequencing or the slew rate time was adjusted with the goal of minimizing the in-rush current. After tuning the engineer was able to get the in-rush current down to essentially zero (see figure below) while still maintaining a proper turn-on of the circuit.

In this post we looked at how a modern power supply with features such as output sequencing, slew rate control, and measurement digitizers can be used to tune the power input turn-on characteristics of an FPGA or any other embedded circuit for designing the power distribution. This is valuable when trying to ensure proper turn-on every time and to minimize in-rush current for power optimization. Below is a link to get more information on Keysight's N6705B DC Power Analyzer and also a link to a good TI app note that discusses properly powering on an FPGA. If you have any questions just email me and if you have any comments use the "Comments" section below.

Click here for more information on the N6705B DC Power Analyzer

TI app note "Tips for successful power-up of today’s high-performance FPGAs"

Tags: keysight, capabilities, analyzer, application, tips, fpga, battery, demo, demonstration, Application Notes, dc, power, n6700

Simulating High Bandwidth Power Supply Transients

keysight — Tue, 09 Nov 2021 17:06:08 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:08 PM

This and other great measurement tips and tricks can be found on the General Purpose Electronics Test Equipment Blog

Monday, February 13, 2012

Simulating High Bandwidth Power Supply Transients

A power supply transient can be defined as an unintended variation of the supply’s amplitude or current. Example terms that refer to supply transients include power surge, spikes, dropouts, interrupts, etc. Power supply transients are caused by things like a sudden sharp load change or when external energy is coupled into the supply, such as when a lightening strike occurs near the supply.

Simulating power supply transients is needed to ensure the device will work to spec in its intended operating environment and ensure it is reliable. Example applications for power supply transient testing is in automotive, aircraft, and satellite electronics. In this blog post will look at a low cost solution for simulating high bandwidth power supply transients using general purpose test equipment and some simple analog circuitry.

With modern high performance power supplies, transients with rise or fall times as fast as ~ 1ms can be simulated. The below images show a captured 10 V transient pulse on top of a 12 VDC level created with Keysight's N6705B DC Power Analyzer. You can see the measured rise time of the pulse is ~ 300 us.

For more information on simulating power supply transients with a modern high performance power supply check out my video by clicking here.

To simulate power supply transients or power arbitrary waveforms with rise and fall times less than 300 us you can use the below solution, which we will call the Active Variable Resistive solution or AVR for short.

From the above AVR schematic, the two DC sources and the waveform generator can be implemented with general purpose test equipment. The MOSFET Switches and Choke are implemented using basic circuit components and should be chosen based on power levels and other considerations that we will discuss.

To go through the AVR system’s theory of operation lets use a simple example transient. Lets say we have a 10 V nominal DC power supply level powering our DUT (load) and we want to create a 10 V transient pulse with a 1 ms pulse width on top of our power supply level.

To start we would set DC source 1 to a 10 V level to serve as our nominal DC power supply level. The waveform generator would be set to a negative voltage value, like -5V, to turn on the P-type MOSFET switch so it acts as a short. In turn the negative voltage from the waveform generator would ensure the N-type MOSFET switch is reversed bias or off. Since the waveform generator’s low is floating, it is tied to the same node as the high of the load so it is at the same potential as the sources of the MOSFETs which are also connected to the same node as the load high. The choke is added to increase the impedance to ground when a transient is generated since there is a small amount of capacitance between the waveform generator’s low and ground. DC source 2 is set to 20 V, but no current is flowing out of it because the N-type switch is off. The current condition of the AVR system is DC source 1 is supplying power to the DUT at 10 V. To create the transient pulse we program the waveform generator for a single 1 ms pulse. The amplitude of the pulse should be enough to fully turn on the N-type switch, for this example we will say 5 V. When the pulse is triggered it will turn the N-type switch on and the P-type switch off. DC source 2 will quickly pull the load node up to 20 V and DC source 1 is effectively removed from the DUT. After 1 ms the waveform generator’s output will go low again and turn off the N-type switch and turn on the P-type switch. This removes DC source 2 from the load and puts DC source 1 back in the load circuit. At this point we have generated our 10 V transient pulse on top of our 10 V power supply level and we are now back at our initial conditions.

To generate a negative pulse with the AVR we would set DC source 2 for the nominal DC level and set DC source 1 to the bottom level of the interrupt, which could be any level between 0 V and the nominal DC level. Set the waveform generator so that the initial condition of the N-type switch is on and the P-type switch is off. Then, using the waveform generator, send a negative pulse to toggle the switches to create the interrupt. To create more complex power waveforms you would use the MOSFETs as variable resistors instead of switches. In this case ensure you use high power MOSFETs and heat dissipation as needed. Also for more complex waveforms a two channel waveform generator would be ideal so the two MOSFETs are not tied to the same waveform.

I implemented the solution using the following test equipment and components:

•DC source 1: N6705B DC Power Analyzer with N6762A Module

•DC source 2: N6705B DC Power Analyzer with N6762A Module

•MOSFET Switches: multiProductLinkSi4410BDY and Si4925BDY

•Waveform Generator: 33522A Fg / Awg

Using the implemented AVR solution I created the below example 15 V 1 ms transient pulse on a 10 VDC level. The first scope shot shows the whole pulse and the second shows the rise time. Both rise and fall times were less than 6 us.

The pulse transient was generated into a 10 Ohm load with a 0.1 uF, 1 uF, and 10 uF capacitors in parallel. This was done to simulate a real world DUT supply input that presents a low impedance to ground for AC signals. Below is an interrupt created with the solution into the same load. The DC level is 25 V. The interrupt pulse is 20 V with a width of 500 us. The resulting fall and rise time of the interrupt is about 7 us.

Simulating power supply transients with a modern high performance power supply allows you to create waveforms with rise and fall times as fast as 300 us. To achieve higher bandwidths a high cost power system is typically employed by standards and quality labs. In this post we discussed and demonstrated a low cost alternative solution for creating higher bandwidth power supply transient waveforms right on the bench. If you have any questions, comments, or add-ons to this post please leave them in the "comments" section below.

Click here for more information on the N6705B DC Power Analyzer

Click here for more information on the 33522A Fg / Awg

Tags: current, keysight, application, tips, modular_power_supply, demo, demonstration, Application Notes, dc, power, n6700

When powering multiple DUTs, should I use multiple small power supplies or one big power supply?

keysight — Tue, 09 Nov 2021 17:06:03 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:06:03 PM

Visit the Keysight Watt's Up? Blog for tips on power products selection, usage, specifications, and design.

Click here to view the blog post on:

When powering multiple DUTs, should I use multiple small power supplies or one big power supply?

For more information on Keysight Power Products visit: www.keysight.com/find/power

Tags: current, keysight, dut, capabilities, tips, battery, voltage, demo, Application Notes, power, n6700

On DC Source Voltage and Current Levels and (Compliance) Limits Part 2: When levels and limits are not the same

keysight — Tue, 09 Nov 2021 17:05:55 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:05:55 PM

Visit the Keysight Watt's Up? Blog. for tips on power products selection, usage, specifications, and design.

Click here to view the blog post on:

On DC Source Voltage and Current Levels and (Compliance) Limits Part 2: When levels and limits are not the same

For more information on Keysight Power Products visit: www.keysight.com/find/power

Tags: current, keysight, application, tips, voltage, demo, Application Notes, dc, n6700

Testing Microinverters Using Keysight E4360 Solar Array Simulators

keysight — Tue, 09 Nov 2021 17:05:06 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:05:06 PM

The Keysight E4360 solar array simulator will provide controllable, consistent, stable, and wide-ranging solar module performance.

Extracting maximum energy

Terrestrial solar micro inverter designers and manufacturers must ensure their products are capable of extracting and delivering the maximum power that is available from the solar modules to which they are attached. Power available from a solar module is highly dependent on its illumination and temperature. The maximum available power is known as the maximum power point (MPP), and it changes with operating conditions. For inverter design, development and qualification, it is critical to test with a variety of MPPs. To obtain a full range of MPPs and other operating points from a solar module with which to test your inverter, it must be exposed to a predictable, repeatable and broad range of illumination and temperature conditions for extended periods. That is impractical to do in a test environment with a solar module. The Keysight E4360 solar array simulator will provide controllable, consistent, stable, and wide-ranging solar module performance.

Use the Keysight E4360 solar array simulator to:

Develop and verify performance of inverter peak power tracking circuits and algorithms
Measure and verify inverter efficiency
Verify the ability of the inverter to produce power grid level output from low to high voltage extremes
Perform qualification tests ― confirm inverter performance during or after exposure to environmental conditions
Perform accelerated lifecycle tests
Perform certification tests

Tags: photovoltaics, videos, solar_array_simulator, video, pv, curves, sas

Capture an IV Curve of a Solar Panel - Solar Module Test (Video)

keysight — Tue, 09 Nov 2021 17:05:05 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:05:05 PM

In Part 1 of this demonstration we will capture a family of IV curves using diferent levels of illuminations.

A simple program was created to control Agilent's N6784A general purpose SMU to capture an IV curve of a solar panel. The N6784A is a four quadrant PS and can be used to sweep through the IV curve of a solar panel. The N6784A module can be used in the N6700-series mainframe or the N6705B DC Power Analyzer.

To view Part 1 of video click here.

In Part 2 of this demonstration, we will capture a family of IV curves at different temperatures. We will use Agilent's N6784A general purpose SMU to capture an IV curve of a solar panel. The N6784A is a four quadrant PS and can be used to sweep through the IV curve of a solar panel. A simple program was created to step through the voltages and measure the current which is then plotted. In addition, we will use a 34972A Data Acquisition Unit to measure the temperature. We connect the 34972A to a pocket router so that readings are sent over a WiFi connection.

To view Part 2 of video click here.

To learn more about Agilent products for solar testing: http://www.agilent.com/find/solarcell

Tags: electronic, videos, current, video, analyzer, application, n3300, voltage, iv, smu, cell, source, load, dc, solar, agilent

N6700 DC Power System Promotion

keysight — Tue, 09 Nov 2021 17:04:46 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:04:46 PM

There’s more to a great power supply than just clean, reliable power.

That’s why the N6700 Modular Power System is designed to simplify difficult tasks and streamline setups
Gain insights with scope-like display, ARB and data logger
Ensure DUT safety with extensive built-in protections
Increase throughput with industry-leading processing speed

Buy three - get one FREE Now until March 31, 2012 buy any three N6700 modules and receive an additional basic N6700 module at no cost when you register your purchase online.

Details found at: http://www.agilent.com/find/PowerPromo. But hurry, quantities are limited. Only eligible for customers in the US and Canada.

Tags: Data Sheets, n6701a, testing, analyzer, n6705b, modular_power_supply, n6700b, voltage, n6702a, supply, promo, dc, power, n6700, promotion, n6705a, agilent

N8700 DC Power Supply Demonstration Video

keysight — Tue, 09 Nov 2021 17:04:45 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:04:45 PM

N8700 series programmable DC power supplies are designed for easy integration into a system. With multiple I/O interfaces and true 2U high, discover how you get just the right performance.

Click on the link below to download the demonstration video.

N8700 DC Power Supply Demonstration Video

Tags: videos, video, n8700, demo, demonstration, dc, agilent

Voltage Margin Testing, Determining Bias Voltage Range Using the N6700 DC Power Supply (Video)

keysight — Tue, 09 Nov 2021 17:04:42 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:04:42 PM

Operating voltages are typically specified as a range. The N6700 DC Power Supply provides fast output changes making it easier to test margins. Testing Bias voltages becomes much more complex when a device uses multiple voltages.

For more information visit: www.agilent.com/find/n6700

Click on the link below to view the video:

Voltage Margin Testing, Determining Bias Voltage Range Using the N6700 DC Power Supply

Tags: videos, current, testing, video, capabilities, analyzer, application, modular_power_supply, n6700b, voltage, modular, measurement, bias, demo, demonstration, margins, supply, dc, power, n6700, agilent

Sequencing DC Power Supply Outputs to Power a PC Motherboard using an N6700 Power Supply (Video)

keysight — Tue, 09 Nov 2021 17:04:42 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:04:42 PM

Some applications require multiple power supplies to turn on in a specific sequence. A PC motherboard requires different voltage supplies to turn on in a sequence. The N6700 series power supply makes it easy to setup timing and voltages. An N6700 mainframe can hold up to four separate modules (independent power supplies).

For more information visit: www.agilent.com/find/n6700

Click on the link below to view video:

Sequencing DC power Supply Outputs to Power a PC Motherboard using a N6700 Power Supply

Tags: videos, current, pc, testing, video, analyzer, output, application, n6700b, modular, Motherboard, demo, demonstration, supply, dc, power, n6700, sequencing, agilent

Create Custom DC Power Supply Waveforms using the Agilent N6700 Power Supply (Video)

keysight — Tue, 09 Nov 2021 17:04:41 GMT

Current Revision posted to Documents by keysight on 11/9/2021 5:04:41 PM

Automated test often require a change in voltage at a predetermine rate. The Agilent N6700 Power Supply makes it easy to create various voltage ramps. For example it can ramp from 0V to 5V in 2 milliseconds.

For more information visit: www.agilent.com/find/n6700

Click on the link below to view video:

Create Customer DC Power Supply Waveforms using the Agilent N6700 Power Supply

Tags: ramp, videos, testing, video, analyzer, voltage, modular, measurement, demo, demonstration, supply, dc, power, n6700, agilent