Hello all,

I want to build the attached half bridge converter but not sure about what inductance the pulse transformer should be.

The lowest inductance product I found was a 260uH Wurth pulse transformer with some as high as 3.3mH.

I tried simulating the driver module with Simulink but when using a 1:1:1 transformer with real inductance and resistance values there was convergence issues that couldn't be resolved so I used an ideal transformer with a 260uH inductor in series with the primary and secondary coils.

Not sure if this is similar but looking at the waveforms, the output square wave of 15V, 100kHz had bad ringing on the low state.
Reducing the inductance showed little ringing.

Any one know how the inductance value is calculated?

 

You want the inductance high enough to give a magnetizing current that is small compared to the maximum load current for the operating frequency being used.
Since the inductive impedance is proportional to frequency, the higher the operating frequency, the lower the required inductance for a given magnetizing current.

 

You want the inductance high enough to give a magnetizing current that is small compared to the maximum load current for the operating frequency being used.
Since the inductive impedance is proportional to frequency, the higher the operating frequency, the lower the required inductance for a given magnetizing current.

I see. I'm not sure if this driver module is even needed. I wonder if I can connect the HG and LG outputs directly to the MOSFETS. The app notes says:

As shown in Figure 17, a cost-effective pulse transformer TR2 is used to transmit the driver signal to
MOSFETs for isolation purpose. The totem pole driver circuits (optional), including a NPN and a PNP
transistor is used to drive the pulse transformer.