MOSFET switching failure

Question

I am working on a power electronic application. I am using push-pull converter topology.

I am using IRF630 power MOSFET to do switching. I also use primary side center tapped transformer Np/Ns = 1/13 ratio. I am using IR2113 MOSFET driver. This is my schematic. I am getting HIN and LIN from STM32F407VG.

These are the inputs which I am getting from STM32F407VG.

There is also dead time to prevent same time turn off/on for MOSFETs.

In this application my purpose was getting 230 V sine wave. This signal is what I got. By the way oscilloscope probe was in 10x. So I am assuming that signal was 316 V.

What could be the mistake?

Answer 1

IR2113 is a bootstrapped high and low side (half H-bridge) driver. Your MOSFETs are both low-side. Consider using low-side drivers instead. These are basically inexpensive high current buffers, to push enough current into the gate to switch quickly.

But it may still work.

Here's the internal schematic of the driver:

The top driver is normally bootstrapped, but it will probably work if it is used as a low side driver. However, to turn the top FET on, it uses the bootstrap cap (between VB and VS, C1 on your schematic) as power supply to push current into the gate. For this to work, pin VS must be connected to the FET source:

...otherwise the current has nowhere to go. But on your schematic, VS is not connected to the FET source, so it can't work.

If this driver can work with both channels low-side, you could replace D1 with a short, since the diode is only useful if you need a bootstrap supply for a high-side drive, which is not the case. So shorting the diode will power the driver directly. Then, connect pin VS to the source of the FET Q2, ie GND.

If this doesn't work, then you need a pair of low-side drivers.

Answer 2

IR2113 is used for a push-pull topology as an half bridge.

If you use digital level MOSFET, you can drive directly your switches. IRLZ44N (55v-47A) may be suitable or better STP40NF10L (100v-40A).

The output will be a DC voltage in your initial schematic.

Be careful with the connection to the earth.

Answer 3

can you please explain me why my circuit won't give sine wave ?

Your circuit is typical of circuits where MOSFETs are used as switches. In such circuits, the mosfet is either ON or OFF. When the upper mosfet is ON, current flows through the center tap of the transformer, through the upper turns, through the mosfet, then to ground. When the lower mosfet is ON, current flows through the center tap of the transformer, through the lower turns, through the mosfet, then to ground. The voltage across the respective transformer turns will be the better part of the supply voltage. The emf induced in the secondary is proportional to the back emf induced in the primary, which is close to the voltage applied to the primary. So, the output voltage at the secondary will be approximately a square wave.

A common way to get a sine wave power output is to use pulse-width modulation, where the pulses are at a much higher frequency than the desired sine wave, and the pulse widths vary according to the desired sine wave frequency. Then the high frequency component is filtered out leaving the sine wave.