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UCC28220: periodically shunt down

Howard Zou
Genius 12365 points
Part Number: UCC28220
Other Parts Discussed in Thread: LM5045

Hi, my customer is using UCC28220 to control a full bridge with an input inductor. Input voltage=48V, output voltage=500V, output power=100W.

They've observed periodically shut down of out1, out2 after the circuit works for a while. The waveform is as below:

After zoom in the waveform is shown as below:

Since the customer has shorted CS1, CS2 to ground, so it should not be caused by overcurrent protection. REF pin voltage is constant. Input voltage is constant.

So what would cause the device to shunt down it's output?

  • 0
    Guru 55913 points
    Hi Howard,

    My first thoughts would be transient latch up of U1 outputs or device over temperature shut down, though I'm unfamiliar with UCC28220. Transients being suspect 500v PWM flyback spike might cause odd latch up issues. Don't see a single MOV in circuit, especially at VCC side U1, is UCC28220? One suspect Opto control OT1-A at U1 may still effect pulse width PWM duty cycles?

    Schottky diodes added HB any gate driver often can prevent spikes to enter pin. Often FET dv/dt can be reduced by increase GateTon R value but adding HB diodes if not already diode (hard to see by schematic).
  • 0
    TI__Expert 3095 points

    Hi Howard Zou,

    Your customer should not use this part to control a half bridge.

    A half-bridge driver will ensure that the outgoing gate goes low, then wait for a short 'dead time', before raising the incoming gate signal.

    This dead time is very important to ensure that it is impossible for both MOSFETs in the same arm of the bridge to be turned ON at the same time.

    If both MOSFETs in the same arm are switched on together they effectively short circuit the input supply resulting in an un-controlled shoot-through current.

    This uncontrolled current is likely to upset operation of the controller and may also damage the power circuit.

    The part your customer is using is designed to control two single ended converters and therefore does not enforce a 'dead time' between the two output.

    I would like to propose to your customer that he uses a half-bridge controller such as LM5045 for example. Many other examples are present on ti.com

    Thanks

    Joe Leisten