How to use ADuM4223 in Full Bridge driver application?

Dear RSchnell,

Thanks. Will check it.

Thanks.

Best regards

NC

Hello NC,

1. There is a small mistake in the circuit, but it is probably just in the drawing, not the actual circuit:

This circuit looks good, if 112V_P, 2V_Q1, and 12V_Q3 are isolated power supplies. How often does the MOSFET fail, and which MOSFET is it?

2. The bootstrap diode will see the bus voltage + 12V + overshoot across it. For a 400V bus, I would guess a 500V rate diode should be good. A common choice for bootstrap diodes is the MUR series, such as the MUR150.

Another cause of the bootstrap capacitor failing could be from overcurrent. If the highside MOSFET fails and causes damage to the A channel of a driver, a short could be formed between VDDA and GNDA. Once that happens, if the lowside channel brings the midpoint voltage to GNDB, the bootstrap diode would see high current and fail.

The cause of the MOSFET failing could be many things. Here are a few:

1. Temperature overstress

2. Repeated peak voltage stress due to ringing

3. Timing error on input side of gate driver

4. Saturation of a load inductor

5. Short circuit on load being driven

Is there any noise on VIA and VIB? Sometimes with a resistor divider network VIA and VIB can be more susceptible to noise from high currents. This is because with a resistor there, a high impedance is seen from the input nodes.

RSchnell

Dear RSchnell,

There are still two questions need your helps.

1. Below is the full bridge circuit, sometiome, the MOSFET will be failed. Please kindly check the circuit is OK or not.

Thanks.

2. The booststrap diode will failed in the below application(Vbus is 400V), what is the max diode voltage?

Thanks.

Best regards

NC

Hello NC,

The bootstrap capacitor size is independent of the bus voltage. It depends on the switching frequency, duty-cycle, and quiescent current of the high-side driver. The circuit note http://www.analog.com/static/imported-files/circuit_notes/CN0196.pdf covers sizing the bootstrap capacitor.

Without know the minimum switching frequency and duty cycle of a particular design, I can't suggest a bootstrap capacitance. I suggest looking at the bootstrap capacitor sections in the circuit note first.

RSchnell

Dear RSchnell,

Thanks for your data.

And how to choose the bootstrap diode in the bootstrap circuit if the Vbus is 400V?

Thanks.

Best regards

NC