A fairly deep dive into the odd but very interesting circuitry of a 0.99 power factor LED driver, that uses clever minimalist circuitry that is not documented on the chip manufacturer's datasheet.

I'm wondering if this is a pin compatible drop-in replacement for another brand that offers other schematic options.

The most obvious electrical weakness of the design is the unfortunate extra winding tap on the primary, that violates electrical clearance on the PCB. The extra screening track used between the MOSFET and sense circuitry is also routed directly under a sense resistor.

The chip is an MT7938 if you want to look at the datasheet. It's in English, but has some oddities to the wording. But it does convey most of the useful information.

The slight shimmer from the LED is low level ripple being picked up by the camera due to the intensity of the light output.

This video is probably not going to be popular. It will only appeal to a tiny percentage of YouTube viewers, but it still needed to be made to cater for those who appreciate the data. That's the curse of technical channels. The more technical they are, the less views they get.


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