Tuesday, August 28, 2012

PWM amplifier 1 - The PWM modulator design II.

I have successfully cleared the last design example of PWM modulator circuit. This PWM modulator will be used before TAS H-bridge chip. In this article, I don't really like the signal at the end, and I made mistakes about power sources (with Zener diodes) on the last simulation schematic. Not too much, but I modified the design, and I got better result. I deleted the dead-time logic, because for the TAS chip not required, the soft start only is easier. At the end of this newer design, I got nice signal from both TTL and CMOS outputs and comparator without dead-time logic. See images.

In this image the green is the triangle signal, the red is 10 kHz sinus, a yellow is the PWM output on the CMOS 4009 inverter.

I know, that not really important, but how I know about the quality of modulated PWM signal? I have to convert back to the original with RLC network. This is the blue line.
I changed the CMOS 4009 (15V power for comparator and CMOS circuit) to TTL 7414 (5V power for comparator and TTL circuit). The TTL output is the yellow line.

 The decoded result at the end of TTL circuit is the blue signal.

I made small modifications on the circuit around the comparator. I changed Z diodes DC power sources, the output of the comprator continued with only one TTL or CMOS gate (inverter). I analyzed the PWM signal after the TTL/CMOS chip, but the output of comparator is really good too with this schematic:

1 comment:

  1. Great post! It was very informative and helpful! You always offered fresh ideas to all readers like me. You've come so far health-journal.hu