Complementary drive from microcontroller

[Prasad]

Hi,

I'm working on a project to construct a sine-wave inverter. The
switches on the output side are 4 IGBTs connected in H-Bridge
configuration. The IGBTs are right now driven by Mitsubishi M57962L
drivers. I've managed to acquire a microcontroller which gives the
required sine-wave PWM pulses at a switching frequency of 20kHz.

Now my problem is the interface the microcontroller to the IGBT
driver. How do i `split' the single PWM pulse in complementary pulses
to drive the high-side and low-side IGBTs??

I've heard there are ICs available that do the job. Someone suggested
UC3714. I've gone through the datasheet, and i feel its not the one
i'm looking for (or maybe i haven't understood the data properly?).

Can anyone suggest any solution??.

Reg.,
Prasad

 

[Anand Dhuru]

Hi Prasad,

Now my problem is the interface the microcontroller to the IGBT
driver. How do i `split' the single PWM pulse in complementary pulses
to drive the high-side and low-side IGBTs??

Why not just pass the signal through 2 inverters in series (like the
7404 / 7414, six inverters in a 14 pin dip)? The output of the first
would give you the complement of your original signal, and the output
of the second would be your signal again.

Or am I missing something here?

Regards,

Anand

 

[Rich Grise]

On Friday 24 September 2004 10:25 pm, Anand Dhuru did deign to grace us with
the following:

Hi Prasad,


Now my problem is the interface the microcontroller to the IGBT
driver. How do i `split' the single PWM pulse in complementary pulses
to drive the high-side and low-side IGBTs??


Why not just pass the signal through 2 inverters in series (like the
7404 / 7414, six inverters in a 14 pin dip)? The output of the first
would give you the complement of your original signal, and the output
of the second would be your signal again.

Or am I missing something here?

I think he's driving an H-bridge, and doesn't know about dead time yet.

You really need four waveforms:

__________ __________ __________
A ____| |________| |________| |_______
____ ________ ________ _______
B |__________| |__________| |__________|

________ ________ ________
C _____| |__________| |__________| |________
_____ __________ __________ ________
D |________| |________| |________|

Where A drives the left-hand high-side P-channel gate,
B drives the right-hand low-side N-channel gate,
C drives the left-hand low-side N-channel gate,
and D drives the right-hand high-side P-channel gate.
(or change "P-channel" to "PNP", "N-channel" to "NPN", and "gate" to
"base.")

The dead time ensures that you don't short out the supply.

Cheers!
Rich