Hello.
We are evaluating the operation of UCC28950.
(Do not connect to power section, operation check with control circuit only)
We plan to place UCC28950 on the primary side.
The voltage error amplifier shorts EA- and COMP and fixes it as unused.
Adjust the voltage of EA + with a variable resistor.
I confirmed the operation of OUTA ~ OUTD at this time.
Symptom
EA + voltage: About 0 to 1 V Result - output stopped
EA + voltage: around 1 V: Result The phase of OUTA, OUTD (OUTB, OUTC) deviates by approximately 180°and operates (Duty = 0), burst operation
EA + voltage: 1 V or more As a result, the phase of OUTA, OUTD (OUTB, OUTC) shifts by approximately 0°(Duty = MAX)
Assumed behavior
Increase the EA + voltage of UCC28950.
The phase shift of OUTA and OUTD gradually decreases gradually, and Duty spreads.
Current operation
At the moment when it rises above the voltage that can generate pulses, it is in motion to operate at full duty.
Because the power section is not connected, the voltage at the CS pin is low,
but will not you control the PWM even if changing the EA + voltage in this state?
If you can tell me your e-mail address, we will send you an operation circuit diagram.
Thank you.
