Light-emitting diode (LED) lighting for the unconventional, comfortable and customized open a new world. These design opportunities in the rapidly enhance the extent and speed of the application of LED in the car. When the led 1w in the car, front and rear lighting, there are several methods and design techniques to choose from.
Automotive LED, the relative vibration, long life, the characteristics of energy-efficient, and subtle control of light sources is a key factor. Compared to incandescent bulbs, the LED on the mechanical vibration is not sensitive, but requires driver circuit. In general, the vehicle's electrical power supply system for lead-acid battery power, the battery driven mechanically by the engine alternator / regulator charging. Such a system suitable for the old-fashioned incandescent bulbs, but not suitable for the LED. In order to enable the LED to achieve the best performance, need a precise constant current of current source.
The correct drive LEDs, we need to control current and voltage. The light output depends on the basic current rather than voltage. In theory, each electron is converted to photons, photons escape out of a fixed percentage of the LED to become what we see light.
If the voltage is constant, you only need a resistor to achieve a high quality program. It should be noted that the simple LED and resistor connected in series with the LED itself to a certain extent is self-regulation. If the temperature rises, the led 10w efficiency and brightness are reduced, and the former while reducing the forward voltage drop. Reduced forward voltage drop and the current increases, so little to make up the brightness due to the temperature rise caused by the decline. As long as the battery voltage is constant, the series resistance program sufficient to meet the requirements of the computer and instrumentation applications. Automotive industry, a mandatory requirement for equipment to be able to meet the changes of batteries from 8V to 18V, and also be able to tolerate the 80V peak. In addition, the bright LED will produce a lot of heat in the resistor. Thus makes thermal design more difficult.
A better but not the best alternative is to use a dc-dc voltage converter to generate a stable voltage is then combined with a resistor. If you already have a computer or other electronic devices powered dc-dc converter, the program is feasible; In addition, this approach may be the most commonly used method of driving the LED.
With a work has nothing to do with the voltage constant current to drive High Power LED 50W is a better program. Energy consumption and energy conversion are two basic types of constant current type.
The linear step-down constant current is an example of the energy consumption constant current. Energy consumption for a given current, constant-current control voltage drop represented consumed. Another situation is that the energy conversion constant current, it tries to store the energy difference between the different levels.
The equation used to describe this energy conversion is one of the basic thermodynamic laws of:
Input power = output power
W = V • I given (given), replaceable W:
Vin • Iin = to Vout Iout + (100 - X% efficiency) the W fever (fever)
If the led power 10w forward voltage Vout, the required current Iout will get the general equation describing the LED driver.
Although the circuit is simple, but with all the energy consumption LED driver, there is the energy consumption and the heat generated by the resistance. With the increase of the LED brightness, the fever will become increasingly serious. LED spot light, and more wasted energy.
Current is smaller, and strung together the LED forward voltage sum is slightly lower than the supply voltage, the steady flow of this type can be used. There are several LED driver IC manufacturers to use constant current method. However, when driving high-brightness led power 50w , does not recommend using this method.