UC3846: Constant Current and Constant Voltage Problem in Primary Stage

Hi,

I cannot open your schematics file. Can you please resend it?

uc3846 pwm child card.pdf900W power.pdf

Hi,

I assume PT1 are half-bridge driver, and CT1 E13 is the transformer which secondary circuit is not shown.

I will just check the UC3846 portion.

Thanks for the reply.  PT1 is the gate drive transformer for driving the Half bridge mosfets.  CT1 is current transformer for measuring the switching current and CT1 secondary circuit is available in UC3846 PWM Child Card.pdf file. Also please find the attached file. 

Observation :

At present we are facing problems in the testing.  The charger is going into overload at 150W load itself.  We are suspecting a problem in the Gate Driver circuit.  Please go through the circuit and help us to identify the root cause. 

4478.uc3846 pwm child card.pdf

What do you mean the charger going into overload at 150W load itself? If you suspect the gate drive, can you capture the waveform to check? Your attachment only shows the IC porion which looks normal so not able to see the issue. Please provide the waveforms you suspect something wrong to help analysis.

We have made the below review but your circuit does not have change. Can you reply why not?

A-OUT, C3 needs a resistor in parallel

B-OUT, R16 needs a capacitor in parallel

check your VIN and Vc and compare to Fig 5, I am not sure what you want to do but their connections seem strange.

Between EA- and comp, R9 should be in series with a capacitor

SD has to be low in order to enable operation, it looks SD in your design is not low so your circuit cannot be Enabled.