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Lighting of high power white LED is a new type of lighting energy saving as a major breakthrough for each, because the technology is not mature at present stage, its not ten points of energy saving effect is obvious. In this case, the LED drive circuit of the power conversion efficiency is a priority problem, for this choice as driving circuit switch power supply scheme.

Practical people designed a dedicated to drive in high power LED switching power supply, its principle as shown. It chooses to switch tube in series with load and the perceptual component, with the capacitive element in parallel type Buck switching converter as the main circuit configuration, the current feedback at the same time, realize the decompression, filtering, steady flow.

The electricity output of the circuit flows through the feedback resistance detection, sampling, and form the feedback signal, feedback signal input to produce a reference voltage of the error amplifier, a reference voltage to cut fixed cycle amplitude of sawtooth wave modulation, formed by the comparator PWM (pulse width modulation) signal. PWM signal amplifying, drive pipe load switch, pulse drive current is produced. Because the output is dc, so add the appropriate external components for filter rectifier load. Load current changes, negative feedback effect of the circuit will change the size of the output duty cycle to achieve the pulse width modulation. Power supply voltage to prevent accidental, fire load tube, also designed the over-voltage protection circuit in the circuit, the circuit when abnormal tube shut off the output load.

Figure principle block diagram

This kind of high power white LED for driving integrated circuit, with a few simple external components that can form a complete pulse modulation type switching power supply, dc constant current output. Integrated circuit can realize frequency is 83 kHz, range of 110 ~ 2720 mA (adjustable) constant current output, voltage ripple and temperature change effect is good.