Design of a low voltage and high current DC-DC converter

Question

Hi all,

I'm dealing with a quite strange design. I have a single 5V power source with few amps of current (about 3A) and I need to drive a load (about 0.8mOhm of resistance, but variable in function of voltage/current) with a current from -10A to 10A, at 100mV of maximum voltage.

I'm searching for an IC which can help me, but I don't found any suitable device, at this moment.

I would try a discrete configuration like the following schematic:

I can send an alternate (square wave) current with one or another direction in the transformer, using a PWM signal on CTRL1 or CTRL2, with 50% duty cycle.

If i use a 10:1 ratio transformer (for example), I will have a reduced maximum voltage, but with more current (about 10 times). Correct?

And then, with another PWM on CTRL3 or CTRL4, I can modulate the output from zero to positive maximum and to negative minimum voltage, measuring the voltage to the feedback point, or the current in series of the load (R1) with an hall effect sensor.

I probably don't even need two input windings, but I can send a single square wave in input and activate Q3 or Q4 to obtain a positive or negative output. And perhaps one of the two outgoing mosfets should be type P?

What do you think about this solution? Anyone have alternative ideas or suggestions?

rsc · Answer

If you kick up your input control voltage to about 20V, you could use an IGBT module.

I've used them to get hundreds of amps for solid state Tesla Coils.

They use them for arc welders also.

Look into induction heater circuits, you might find what you're looking for.

Scott

michaelkellett · Answer

How accurately must you control the voltage/current ? How much noise is acceptable on the output. What sort of signal will you drive the load with ? (AC, slowly varying DC etc) (Can you tell us what the load is ?) I'm thinking that the best bet would be a 5V to 1V switching converter and then a linear bridge type power amplifier. Alternatively you could re-purpose the LT1923 which is a switching Thermo electric cooler driver. Even if you don't use this chip it would be worth reading the data sheet and app note to get some background information. I've used this chip and it works quite well, (although it's very expensive). Since the power FETs and sense resistor are off chip you can tune it up for whatever you want. MK

Jan Cumps · Answer

Can I summarise it like this? - you need a device that can control a DC current between -10 A and + 10 A. That current has to be configurable and maintained by the circuit. - it's derived from the load that within these ranges, the output voltage will stay between -100 mV and 100 mV - The input voltage has to be 5 V DC. - a switch mode design.

Design of a low voltage and high current DC-DC converter

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