Application of LM393 in LED drive power supply

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Application of LM393 in LED drive power supply

From: www.hzleddriver.com 

The LM393 comparator is a high-gain, wide-band device that, like most comparators, is prone to oscillations if coupled with parasitic capacitance from the output to the input. This phenomenon occurs only in the gap between the output voltage transitions when the comparator changes state. Power supply and bypass filtering cannot solve this problem, and the design of standard PCB boards helps to reduce input-output parasitic capacitive coupling. Reducing the input resistance to less than 10K will reduce the feedback signal, and increasing even a small amount of positive feedback (hysteresis 1.0~10mV) can lead to rapid conversion, making it impossible to generate oscillations due to stray capacitance. Unless hysteresis is utilized, inserting the IC directly and adding resistance to the pin will cause the input-output to oscillate over a very short transition period. If the input signal is an impulse waveform and the rise and fall time is fairly fast, hysteresis will not be required.
The specific working principle is as follows:
 When the input voltage at the IN+ end is greater than the input voltage at the IN- end, the OUT output high voltage (VCC voltage equal to IC); When IN+ end input voltage is less than IN- end input voltage, OUT output low voltage (equal to IC VSS voltage).
 In the picture, the reference voltage values of the upper and lower limits set by the 3 and 6 pins and the voltage values to be collected by the 2 and 5 pins are used to implement the condition principle when the set conditions are reached. Our company is often used for LED drive DC-DC overvoltage Undervoltage protection.




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Add: 12th Jinling Road, Zhongkai Hi-tech Zone, Huizhou City, Guangdong, China,516006

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Web:http://www.hzleddriver.com

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