Pulse Width Modulation (PWM) circuit

[jackyhsu]

Dear Advancer:

I will be responsible for DC-DC converter .PWM circuit seems the most important circuit.I know one architecture is "op+ triangle wave" but I do not feel it is the best choice. Can anyone give me other circuit that have proved or other information about it ?

thanks.

 

[usernam]

In a DC-DC converter to control using PWM triangular waveform is the best option. Since then the increase in control voltage will be proportional to duty ratio.So control is easy.
The other control method is not related to PWM. Here both switching freq. and on-time of the switch are varied. This method utilizes force-commutated thyristors and the variation of switching freq makes it difficult to filter ripple components in the input and output waveforms of the converter.

 

[JuergFrefel]

Unless your goal is to try to learn how a DC/DC convert works I wouldn't build one from scratch. This problem has been solved many times and various vendors have dedicated DC/DC IC available.
Check the Linear Tech, Nation Semi, or TI website.

If you want to go ahead and build it yourself one option is to do a current mode amplifier. You ramp the current in an inductor up until you hit a certain threshold and then switch it to the output.

Going the PWM route can be done with a triangle generator / comparator or it's digital equivalent. Many processors have pwm units already build in.

 

[nand_gates]

Use IC 3524 this is waht we use extensively.