Hi,
I am using the ADP1055 for controlling a phase shifted full bridge converter.
I have a problem when the converter is running at maximum duty cycle due to low input voltage. The expected behaviour is that the converter is running continuously at maximum duty cycle with reduced output voltage. This should be 'stable' operation until the output voltage is below the output under-voltage warning threshold. My output under-voltage warning threshold is set to 0 V, hence I expect to see continuous operation independent of the input voltage.
What I see is that the duty cycle drops to 0 every ~100 ms for 1 switching cycle and then the control is slowly increasing it again to maximum duty cycle. Because of the short time where no power is transferred, the output voltage drops lower than it needs to be.
Picture below shows a measurement. Target output voltage is 45 V and due to low input voltage, the converter is achieving 44 V.
Yellow is the transformer current, blue is the full bridge voltage, orange the output voltage.
Configuration of PWM
