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UCC2808A-1Q1: weak output with load

Part Number: UCC2808A-1Q1

We use TI's UCC2808 device for an asymmetric half-bridge resonant power supply, as shown in the figure.

With 250 kRC frequency and 100 uH 1:1.008 turn ratio of TDK, the output load capacity of 40 mA is too weak, resulting in the output of ± 15V to 13V, and the secondary side voltage bootstrap rectifier capacitor voltage drops from 7V to 6.3V. Adjusting circuit parameters to raise RC oscillation frequency to 500k,  power frequency 250k, and increasing primary side resonant capacitance from 0.1uF to 1uF and secondary side voltage bootstrap rectifier capacitance are ineffective.

At present, the possible reason is that the transformer magnetic field is not enough, or the application of UCC2808AQDR has problems. Please help us to analyze the possible reasons for the problems.

TDK + IR AUIR2085STR Solutions is working

  • Hi

    Please check the voltage level at PWM_A and PWM_B, maybe the voltage is dropping with increasing load, try reducing the value of the gate drive resistor to see if the Vce decreases. Are the PWM_A & B voltage levels lower than PWM signal in AUIR circuit?

    Regards

    Peter