PWM SG3525 (problems and strange behavior)

Discussion in 'General Electronics Chat' started by ajp, Sep 9, 2014.

  1. ajp

    Thread Starter New Member

    Aug 28, 2014
    Good! First of all I introduce myself and congratulate all the members of this community that nurtured and I both learned from this exciting world of electronics.
    I tell them: I'm doing a SG3525 PWM with which feed a think IR2110 and able to handle (or two) IRFP460 to control a DC motor.
    In reading, searching and trying different circuits, I get mixed results in terms of the output of the blessed SG3525

    1-I Using the circuit below get a nice square wave, in which various pot P1 and get the consequent variation of the duty cycle, like moving the pot P2 varies the frequency (a trial just connect the stage of 3525 and I measure with the oscilloscope on pin 13)
    Sin título2.png
    2- Because the previous circuit VC get a 5v output and the MOSFET Gate need at least 12v, I make the following changes to the circuit
    Sin título.jpg
    Getting the following waveforms at the output of the diodes:
    By varying the frequency:
    If I move the pot connected to pin 2 waveform does not change practically, unable to see something that resembles a variation of the duty cycle. As you will see a ramp, far from the desired square wave.

    Testing the following circuit:
    Connecting only pin 8 SSTART capacitor and measuring again at the outputs of the diodes ... Guess! Back to the blessed get out ramp :(
    Any help or suggestions are welcome. Apologize for my elementary English, without the google translator I am nothing ...