LED power supply not working

qrnuyangfu

LED power supply not working [Copy link]

 

Could you please help me check, the LED power supply has no output, and the input voltage of LD7535 is about 1.4V.

qwqwqw2088

This chip, VCC is only about 1.4V

LD7535

qwqwqw2088

The supply voltage of the main control chip

qwqwqw2088

Check the chip VCC pin, the connection to the bridge stack, and whether the startup resistors are connected correctly.

qrnuyangfu

qwqwqw2088 posted on 2019-8-16 11:29 Check the chip VCC pin, the connection to the bridge stack, and whether the connection of several startup resistors is correct

The usage of the copied board is slightly different from the typical circuit. C12 is charged first and then C12 supplies power to the chip, but the voltage value cannot be reached.

伟林电源

First check the waveform to see if it has entered protection mode.

伟林电源

Or disconnect the load first and then test it with no load. Is it normal?

伟林电源

If it is normal, it is estimated that the load is short-circuited or overcurrent.

伟林电源

If it is not normal even when no-load, first check whether the startup resistor and VCC capacitor are normal.

伟林电源

Or use a simple and rough method to re-solder all solder joints to avoid problems of cold solder joints and false solder joints.

qwqwqw2088

qrnuyangfu posted on 2019-8-16 16:29 The usage of the copied board is slightly different from the typical circuit. C12 is charged first and then C12 supplies power to the chip, but the voltage value cannot be reached

Did you copy it from a board?

This is hard to say, maybe I copied it wrong.

qwqwqw2088

The picture on the first floor, is this bridge stack connected correctly? No wonder there is a problem with the input voltage of the chip. Please check the original board carefully.

云中君

Are the transformer's like-named terminals correct?