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


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Last time we have already discussed about TNY266PN working in pulse power supply circuit. we studied an example of using TNY266PN. Today will study a case of using TNY267PN in pulse power supply circuit. TNY266PN and TNY267PN are same in electric pinout functions, but output power of TNY267PN is bigger than TNY266PN so you can replace TNY266PN by TNY267PN. 
You also know about TNY266PN details in previous article at here.

TNY267PN is very popular in using in pulse power supply circuit. There are so many Mitsubishi air conditioner series using TNY267PN in their air conditioners. authelectronic took a Mitsubishi air conditioner board, and drew a full circuit as you can see below

Before we look at Mitsubishi circuit, we will look at TNY267PN pinout.


Authelectronic has analysed many air conditioner circuits, but we see in Mitsubishi circuit has a good point that it has enough protect circuits. That's a good point of designing.

We first start with 220V AC input voltage, then current goes through F1 fuse, you can see CR symbol is over voltage protection capacitor. Then next you see L1 conductor and C1 capacitor are used to filter noise.

usually the circuit designer uses ACDET Circuit to protect 220V AC input voltage as you can see. In other article Authelectronic will explain more details about ACDET circuit. To supply power for ACDET circuit we use CT transformer provide input power for ACDET protection circuit.

Next you see that current goes through AC detector inductor , this AC detector is used to protect IPM ICs (Intelligent Power Module). You also can see X64 , it's a input short circuit protect circuit. next the current goes to bridge rectifier to change 220V AC input to 300V DC output, then we see before it goes to bridge rectifier it goes to a boost voltage circuit. In a case in put voltage is under 220V AC, then bridge rectifier output voltage is not enough 330V DC, this boost voltage is used to make sure output voltage is always 300V DC.

then both CG1 and CG2 capacitors are used to make output 300V DC flatter. After 300VDC becomes flatter, this 300VDC goes through F2 fuse to IPM IC. You can see they use OPV2 voltage distribution circuit to monitor input voltage of IPM IC. 300V DC also goes through F8 fuse then goes to the primary coil of CT1 transformer then to D pin of TNY267PN to supply power for TNY267PN IC. they also use OPV1 voltage distribution and MCU ( microprocessor ) to monitor this 300VDC voltage.

Let's look at CT1 transformer, It has 4 secondary coils. 2,4 coil, 5,6 coil, 6,7 coil and 7,8 coil. At secondary coil 2,4 , the output AC voltage is converted 15VDC voltage  by using D822 diode. This 15 VDC voltage is supply power for Boost voltage circuit as we have described before. At 5,6 secondary coil, the output AC voltage is converted to DC voltage by using D888 diode, and next using C887 capacitor, L888 coil  and C888 capacitor to make output DC voltage flat at 5VDC. This 5VDC voltage is used to supply power to sensors and MCU. At 6,7 secondary coil , the AC output voltage is converted to DC voltage by using D884 and D885 diodes, then using C884 capacitor to make this DC voltage flat at 12VDC. This 12VDC power to relays and other circuits. At 7,8 secondary coil, the AC output voltage is converted to DC output voltage by using D880 diode, then the C882 capacitor makes this DC output flat at 15VDC. This 15VDC supply power to IPM IC 


Inside TNY267PN it has a Mosfet , and a pulse generator. the pulse generator create pulse at a certain frequency to G pin of Mosfet inside TNY267PN. 300Vdc voltage go through primary coil of CT1 to D pin (5th pin of TN267PN) Mosfet, and go to S pin of Mosfet,by this way the induction currents  were created in 4 coils are 2,4 coil 5,6 coil 6,7 coil and 7,8 coil.

if you don't understand how TNY267PN work and how a pulse power supply work clearly, please click this article below.

How do tny263pn tny264pn tny265pn tny266 tny266pn tny267pn tny267gn tny268pn tny268gn work in power supply circuit?

Feedback system in pulse power supply 

As you can see in Mitsubishi pulse power supply circuit it has many output voltages 5VDC 12VDC . But in some cases those output voltages will not be 5Vdc or 12VDC Because of electric Loads. So that's why we need a feedback system to mornitor output voltages.Look at pin 4 of TNY27PN, it is call Feedback pin. The pin 4 of TNY267PN is connected to pin 4 of Opto PC801. We can see TL431 and voltage distribution circuit are also used for feedback system. Let's see how feedback system works.

Look at 5,6 secondary coil , In a case of output voltage upper than 5VDC, the Vr voltage of voltage distribution circuit (r802a, r802b, r802c) is also up,  it makes KA431 open, then PC801 works, then pin 4 (FB pin ) is connected to GND. The Voltage of pin 4 TNY267PN move from Vfb to 0V DC. this makes the pulse generator in TNY267PN change pulse frequency go down to make output voltage 5VDC stable.

In a case of output voltage lower than 5VDC, KA431 can not open so PC801 also does not open. So Voltage of pin 4 TNY267PN Vfb goes up, that makes pulse generator inside TNY267PN generate higher frequency, so that output voltage will be stable at 5VDC.

These are all basic knowledge of pulse power supply circuit in Mitsubishi air conditioner, if you have any questions or any ideas please comment below. See you in next article!

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