Generating Signal for H-bridge control

[jean12]

Hello there ,can anyone please help me to generate a signal which I can use for controlling my H-bridge made by IRFP460Z at 440VDC;I want to get 220VAC/50Hz;please help.

I tried to use the technics of Tahmid blog with SPWM but I failed I am getting nothing at the output.
Thanks.

 

[BradtheRad]

Are you certain your mosfets/transistors are turning on and off fully? Because if your supply is high voltage, then you must bias them with high voltage. This is how you must turn a P-device off. It is also to turn an N-device On if it is located at the high side.

The exception is N-devices located near zero ground... they can be turned on with low voltage.

It is not difficult to generate a low-voltage pulse train. Then to turn it into high voltage, this schematic illustrates a simple way to drive devices located in the upper half (high side) of an H-bridge.



Notice the clock pulses are 5V.

Square waves are easiest to handle, while experimenting.
The load is resistive... also easy to handle.

Normally the lower mosfets should turn on fully. (However the simulator apparently uses unusual parameters for mosfets, and they do not conduct as much current as they ought to.)

 

[Tahmid]

Hello there ,can anyone please help me to generate a signal which I can use for controlling my H-bridge made by IRFP460Z at 440VDC;I want to get 220VAC/50Hz;please help.

I tried to use the technics of Tahmid blog with SPWM but I failed I am getting nothing at the output.
Thanks.

Do you get nothing at the microcontroller output or at the H-bridge output?

Are you certain your mosfets/transistors are turning on and off fully? Because if your supply is high voltage, then you must bias them with high voltage. This is how you must turn a P-device off. It is also to turn an N-device On if it is located at the high side.

The exception is N-devices located near zero ground... they can be turned on with low voltage.

It is not difficult to generate a low-voltage pulse train. Then to turn it into high voltage, this schematic illustrates a simple way to drive devices located in the upper half (high side) of an H-bridge.



Notice the clock pulses are 5V.

Square waves are easiest to handle, while experimenting.
The load is resistive... also easy to handle.

Normally the lower mosfets should turn on fully. (However the simulator apparently uses unusual parameters for mosfets, and they do not conduct as much current as they ought to.)

Pulling the gate of a P-channel MOSFET to ground while it is pulled-up to 311V will blow the MOSFET gate. It should be pulled down to no lower than (usually) 20V below its source to avoid damaging the gate. You would need a level shifter. A zener diode across the gate-to-source resistor along with a current-limiting resistor between the gate and driving transistor's collector/gate should suffice for low frequencies.

Hope this helps.
Tahmid.

 

[jean12]

Hello Tahmid,I am getting nothing at the output of the H-bridge,I am using the oscillator of PIC16F1827 with SPWM generation using your techniques in your blogs.

Please help.

Thanks.

 

[BradtheRad]

Pulling the gate of a P-channel MOSFET to ground while it is pulled-up to 311V will blow the MOSFET gate. It should be pulled down to no lower than (usually) 20V below its source to avoid damaging the gate. You would need a level shifter. A zener diode across the gate-to-source resistor along with a current-limiting resistor between the gate and driving transistor's collector/gate should suffice for low frequencies.

Hope this helps.
Tahmid.

I believe you are correct. I have revised my schematic along the lines you recommend. (However I cannot be sure which resistor values will work best in all cases.)

Using mosfets in this simulator requires extra finagling. I find that even as high as 20V differential does not fully turn on the simulated mosfet gates. However real mosfets operate at less voltage.

 

[Tahmid]

Hello Tahmid,I am getting nothing at the output of the H-bridge,I am using the oscillator of PIC16F1827 with SPWM generation using your techniques in your blogs.

Please help.

Thanks.

Have you used a proper H-bridge driver circuit? Provide the schematic of your circuit setup.

 

[jean12]

Providing the circuit is highly difficult because the driver I have are the TLP250 (I have 3 of them the 4th has had the problems on the pins),previosly I used the ICL7667 then on the forum here I have been told that those are not used for driving the MOSFET in H-bridge configuration (Note:Those ICL7667 I have used them for driving the push pull which I used for stepping up 12VDC to 440VDC and I succeeded with this).

When I used the ICL7667 on the H-bridge I have get 8VAC and a high DC component on the H-bridge;when applying 150VDC on the H-bridge.
I am asking if I can use (2) of those TLP250 so that I can connect two MOSFET in parallel?

Can you please help me to think more on that?Those TLP250are the ones which were used on the same DC_AC Converter I am repairing but its control block has crached so I need to replace it.

Here is the snap for the controlling signal I am using with PIC16F1827

Thanks,please help.