driving a Half-bridge driver

[beefalo]

555 dead time half-bridge

Hello,

I am using an LT1160 half-bridge driver from Linear Technology to drive a couple of MOSFETS in a power supply I am working on. Right now I have the setup working properly on the bench; I am using a pulse generator with a built in digital delay as the PWM input on the LT1160.

What I am wondering however is how to drive the LT1160 with an IC that will put out pulses like the pulse generator does. I am confused by PWM control ICs....is this what they do, put out square wave pulses for this type of application? If not, what can I use? I have looked around some and found that Maxim makes a chip that functions as a waveform generator on a chip, but it seems like overkill.

What I need is user-programmable frequency (800 Hz.) and variable duty cycle, as well as a way to have the two pulse streams completely out of phase with each other (for the upper mosfet and lower mosfet), as well as adjustable dead-time.

Please help if you can, I sincerely appreciate any help!

 

[IanP]

half-bridge 555 pwm with dead time

Try PWM circuit based on the very popular 555 timer (see picture below) ..
Insted of Q1 (leave R4 and R5) connect CD4049 CMOS inverter gate, then cascade second inverter for 180° wave ..
For 800Hz C1 should be ≈22nF ..

Regards,
IanP

 

[beefalo]

Thank you very much for the reply and the circuit! Can this circuit be pulse-width adjusted? What about PWM chips, do you know anything about these? Thanks!

 

[IanP]

This circuit can have the width of pulses adjusted from, say, 5% to 95% (adjustable by R1 ratio), at pre-selected frequecy (with R1=100kΩ and C1=22nF it will be ≈800Hz) ..
Other option would be to employ a microcontroller with built-in PWM block and program it accordingly to your needs ..
Here is an example:
**broken link removed**
.. or just use any microcontroller and generate PWM in software; example at: https://www.iguanalabs.com/pwm.htm ..

Regards,
IanP

 

[beefalo]

IanP,

Just wanted to let you know I built the circuit like you recommended (using 555 timers) and it works great! I actually cascaded three of them and I am able to generate variable duty cycle and frequency pulses for high and low side mosfet drivers, and I can also vary the phasing between the two signals.

I am having other problems now with my design (which I will ask for help with shortly) but thanks again!