Smps converter showing weird behavior !

[SM-Piyes90]

Hi everybody .

I have recently been busy trying to resolve a problem concerning a high current smps converter.

The problem is when I power the unit , I get :

1- no fan rotation.
2- over temp led that lights up fir 5 seconds and goes off as soon as a relay de-energizes ( RL001A) .


I checked the fan circuit witch mainly consists of a tip122 transistor , but every component around is good .

Here is a schematic , and thanks in advance .

[rievax_60]

Re: Smps converter showing weird behavior !

It looks like a welder. Not all of the schematic makes sense to me. U1PB is used as a timer. I would expect RL001A is turning on after the 5 seconds after mains is applied.
There is a control path from U1PB to U1PA via QR2 and QR3 that also causes the temperature LED to turn off at the same time.

[budm]

Re: Smps converter showing weird behavior !

Did you check all the DC regulated power supplies:The +15-HAUT, VCC-U2P, +13V?
Also the +HT for the main power supply section.

[paulstef]

Re: Smps converter showing weird behavior !

As budm said, what are the voltages when RL001A is on?

For the fan to run TR1 must be working, therefore the 8 power transistors to the right must be switching.

First, when RL001A closes you should get +HT (unless D1P is faulty of course).

The overtemp LED, is that the yellow LED to the left?
What is connected to MES-TEMP? Should be an NTC (heats up, lowers resistance, U1PAs' output goes high, activates LED.)

It looks (just had a quick look) to me that when the LED is on then:
- Q8P npn is off
- Q8P pnp is on (are those two complemenatry in the same package?)
- pin 2 VFB of U2P gets some voltage from REF-5V, should then cut or limit pulses (or width) to OUT pin 6
-U3P is a gate driver, should then disable its outputs, therefore power transistors are off
- no output voltage from TR1.

I would check first where the temperature sensor goes to, probably near the power transistors, check if any of them is shorted

The temperature sensor or circuit could also be faulty, ideally you would measure input current while RL001 is on.

[SM-Piyes90]

Re: Smps converter showing weird behavior !

Hi again everyone and thanks for your comments .

As a response to your previous questions , i was wrong about the relay , actually the relay turns on as soon as the temp led goes off but the relay seems to energize very slowly and not instantly .

I get 13 volts , 320 volts , but i don't know about the 15 v HAUT (?) (top left) , maybe used for IGBTs gate triggering ?

Anyways the conversation is still open for more ideas guys .

[SM-Piyes90]

Re: Smps converter showing weird behavior !

could the problem be the lm324 ?

[budm]

Re: Smps converter showing weird behavior !

I do not know what is going on with BADCAPS site, I cannot download the picture of the diagram on post 1.

[stj]

Re: Smps converter showing weird behavior !

I do not know what is going on with BADCAPS site, I cannot download the picture of the diagram on post 1.

it's not an attachement, he posted an inline image.
do a right-click save-as on it.

[budm]

Re: Smps converter showing weird behavior !

I did and never have problem download the inline or attachment pictures, and now I get server error.
The picture used to show right on the page before because I did downloaded before.
Right now you only see small icon instead of the in line picture.

[SM-Piyes90]

Re: Smps converter showing weird behavior !

OK here it is :

[budm]

Re: Smps converter showing weird behavior !

So you do not have +15V-HAUT output which is the bootstrap for driving the upper set of the Q1~4.

[SM-Piyes90]

Re: Smps converter showing weird behavior !

So you do not have +15V-HAUT output which is the bootstrap for driving the upper set of the Q1~4.

I will check the 15 v section as well as the part related to the gate driver .