Understanding how power supply IC TNY274GN works in household device circuit?

In your house there are many household devices, and some of them one day have fault, don’t work even you supply them input voltage. In this article I will explain to you why they don’t work and help you can fix your household devices basically, all you need is reading this article carefully and know some basic electronic knowledge. 

One of the most common fault of electronic household device is power supplic IC dead, broken. There are many reasons for dead , broken power supply IC , some reasons are wrong input voltage, continue working for long time, overvoltage, overload,.etc. The most basically way to fix this fault is replacing power supply IC. This article show you a very common power supply IC TNY274GN, helps you understanding basically how TNY274GN work in a household device like refrigerator, washing machine, tivi, ,etc.

  1. TNY274GN Pin Functional Description and Packet
Understanding how power supply IC TNY274GN works in household device circuit?
Understanding how power supply IC TNY274GN works in household device circuit?

D pin – This pin is the power MOSFET drain connection. It provides internal operating current for both startup and steady-state operation

S pin – This pin is internally connected to the output MOSFET source for high voltage power return and control circuit common.

BP/M pin – multiple function selector pin.

EN/UV pin –  enable input and line undervoltage sense pin.

  1. Explain TNY274GN works in 12 V, 1 A Universal Input Power Supply
Understanding how power supply IC TNY274GN works in household device circuit?

when you supply input voltage 85 VAC – 265VAC, the current goes through input protecting block include F1 fuse, RV1 varistor. Next the AC current goes to bridge rectifier include 4 diodes 1N4007 then it converts AC voltage to DC voltage. Many times in your household device circuit the Bridge rectifier ICs like D20XB80 , RBV2006, GBJ3510 broken so the machine can not work. You only need to replace the Bridge rectifier then it will work normaly. The DC voltage after bridge rectifier will be flattened by C1 C2 capacitors and L1 coil. Then the positive pole of DC voltage connects to 1th point of the primary coil of pulse transformer T1. The 2nd point of the primary coil connects to D pin of TNY274GN. Inside TNY274GN it has a Mosfet and this D pin is also the same as D pin of the Mosfet. So you can see this S pin of TNY274GN is also the same as S pin of the Mosfet. When the mosfet on of the current goes through mosfet is very high, so to protect mosfet inside TNY274GN it has a D pin protecting block including r1 r2 resistors and d1 diode. On the output secondary coil of T1 transformer, D7 diode converts 6,8 point voltage to DC voltage then flat this DC voltage by C10 C11 capacitors and L2 coil. 

The output will be 12VDC flat, to make this 12VDC stable it has a voltage feedback block including r4 r6 resistors, pc817 opto. the voltage divider circuit r4 r6 drop 12vdc voltage to lower voltage at r4 resistor. Voltage of r4 supply to PC817. When output voltage high or low, the voltage r4 also high or low, then PC817 opens or close, this signal goes to EN/UV pin, so the TNY274GN understand the output volatge is upper 12VDC or Lower than 12VDC, TNY24GN will change  it’s frequency to control Mosfet inside so that way can control output always 12VDC stable. 

If you want to understand more about TNY274GN , other TNY power supply ICs, read articles below

Studying example circuits using tny274 tny275 tny276 tny277 tny278 tny279 tny280

How to repair pulse power supply circuit using tny267pn in mitsubishi air conditioner