Help finding schematic for ITE UP30432

[badrianiulian]

Re: Help finding schematic for ITE UP30432

So, a recap for IC measurements, since I missed some answers:
Voltage Feedback (2) = 0v to 0,8V variable
Vcc (7) = 11,7 to 14V variable
Vref (8) = 0,3V to 1,4V

[fzabkar]

Re: Help finding schematic for ITE UP30432

The Vref voltage should be 5.0V. Could it be that the filter capacitor on pin #8 is dragging it down?

The IC requires 16V via the startup resistor before it can start. It then sends a pulse to the chopper, and this then generates an auxiliary supply via the secondary feedback winding and the 47uF and 100uF capacitors plus the 1N4935 rectifiers. These capacitors are often responsible for startup problems, as is the startup resistor.

If there is a problem on any of the secondaries, eg an overload or a leaky diode, then the IC does not receive sufficient voltage via the feedback winding and its supply drops below the undervoltage lockout threshold (UVLO-off = 10V), causing it to turn off. The supply then needs to rise above 16V via the startup resistor before it will turn on again.

https://cdn.badcaps-static.com/pdfs/...9eef16428b.pdf

[badrianiulian]

Re: Help finding schematic for ITE UP30432

I've been poking, replacing, measuring all components (including capcacitors with a 20000mF max capacimeter) and I'm begining to think my transformer may be bad.
I've compared some windings on at least four transformers from some dvd players smps I have laying arround for parts and I think that my primary may be the cause... maybe a short?
I've measured the AUX winding from all transformers and it's about 0,4 ohms to 0,8 ohms... The primary varies from 1 ohm (big transformer) to 2,2 ohms (smaller transformer)... As for my readings AUX=0,4 ohms and primary 0,6 ohms....
Could this cause the variations?

[fzabkar]

Re: Help finding schematic for ITE UP30432

I'm still bothered by the missing Vref voltage. I would test the circuit with a variable laboratory PSU.

Disconnect the PSU from the AC mains and connect the lab supply to pin 7 of the IC. The voltage needs to rise above 16V for the IC to start, but then it can be reduced to as low as 10V before the IC stops. When the IC is running, measure the Vref (pin 8) and feedback (pin 2) voltages. When pin 2 is below 2.5V, the output at pin 6 should be driving the gate of the chopper at the highest PWM duty cycle. Conversely, when pin 2 is above 2.5V, the output should be at the lowest duty cycle, or turned off completely.

BTW, because you will be using a lab supply, you can now safely connect an oscilloscope to the circuit. You can then monitor the peak AC voltages at each of the primary and secondary windings. This should tell you the turns ratios. The voltages will be small, however, because the chopper current will be small. To increase the current, you could add a resistor in parallel with the startup resistor.

[badrianiulian]

Re: Help finding schematic for ITE UP30432

I'm still bothered by the missing Vref voltage. I would test the circuit with a variable laboratory PSU.

Disconnect the PSU from the AC mains and connect the lab supply to pin 7 of the IC. The voltage needs to rise above 16V for the IC to start, but then it can be reduced to as low as 10V before the IC stops. When the IC is running, measure the Vref (pin 8) and feedback (pin 2) voltages. When pin 2 is below 2.5V, the output at pin 6 should be driving the gate of the chopper at the highest PWM duty cycle. Conversely, when pin 2 is above 2.5V, the output should be at the lowest duty cycle, or turned off completely.

BTW, because you will be using a lab supply, you can now safely connect an oscilloscope to the circuit. You can then monitor the peak AC voltages at each of the primary and secondary windings. This should tell you the turns ratios. The voltages will be small, however, because the chopper current will be small. To increase the current, you could add a resistor in parallel with the startup resistor.

It seems I misjudged the transistor on the heatsink... It is actually a NPN Transistor: TIPL760A

Measurement one:
pin 1:5,92v pin 2:2,49V
pin8: 5V pin7: 10,33V pin6:8,93V
BUZ71A Gate pin 7,57V

Measurement two:
pin 1:5,92v pin 2:2,49V
pin8: 5V pin7: 13,13V pin6:11,77V
BUZ71A Gate pin 9,98V

Measurement three:
pin 1:5,92v pin 2:2,49V
pin8: 5V pin7: 15,97V pin6:14,57V
BUZ71A Gate pin 12,92V

As for the osciloscope... I got one but it does not have any measurements on screen and never learned how to use one... I gotta get myself to do that sometimes... it's a must

[fzabkar]

Re: Help finding schematic for ITE UP30432

ISTM that the IC thinks that it is regulating correctly. That would explain why the feedback voltage is stable at 2.49V, even when the output is varying wildly. The reference is also stable at 5V.

I would be looking at the feedback resistors (18K and 4.7K), as well as the 100pF capacitor.

[badrianiulian]

Re: Help finding schematic for ITE UP30432

By now I've triple checked all the resistors, the active components and the capacitors are measured to their markings. I once had a case where some electrolytics leaked on the board and the smps went haywire with a variable output... After cleaning all was good. Could this be a cause?
I ask this becouse I don't have a history of this power source and to remove all components to clean the board will take forever

[fzabkar]

Re: Help finding schematic for ITE UP30432

This is the application circuit that I uploaded to the forum:

http://www.users.on.net/~fzabkar/tem...pp_circuit.gif

I don't know why the forum software shrank it.

Your measurements are saying that the voltage at the junction of the 18K/4.7K potential divider (pin 2) is remaining constant at 2.5V, yet the voltage at the top end of the divider (pin 7) is fluctuating between 10.33V and 15.97V. How can that be?

[badrianiulian]

Re: Help finding schematic for ITE UP30432

The voltage variation at pin 7 was done by me manually from the lab power supply and well, the schematic in fig 35 isn't the same as this power source... I'll try to build one and post it... I still was hoping someone had it

[fzabkar]

Re: Help finding schematic for ITE UP30432

Yes, it does look like your circuit is significantly different. I can see an optocoupler (?) which probably provides the feedback from the secondary side. That said, if you're using a lab supply, then you would be without an AC mains supply, in which case I can't see how the 2.5V feedback would be generated. Very strange ...

BTW, you should confirm that connecting a lab supply to your particular circuit is a safe thing to do. I was basing my judgment on the application circuit in the datasheet.

[badrianiulian]

Re: Help finding schematic for ITE UP30432

Yes, it does look like your circuit is significantly different. I can see an optocoupler (?) which probably provides the feedback from the secondary side. That said, if you're using a lab supply, then you would be without an AC mains supply, in which case I can't see how the 2.5V feedback would be generated. Very strange ...

BTW, you should confirm that connecting a lab supply to your particular circuit is a safe thing to do. I was basing my judgment on the application circuit in the datasheet.

Yes I can confirm that connecting a lab supply is safe... I used a DIY power supply I build a while ago https://www.facebook.com/media/set/?...1&l=8c07373402

[fzabkar]

Re: Help finding schematic for ITE UP30432

When you run your ITE PSU from a lab PSU, do you get any voltage on the DC outputs ???