Circuit explanation needed please.

Discussion in 'General Electronics Chat' started by TapOut64, Mar 17, 2011.

  1. TapOut64

    Thread Starter New Member

    Mar 17, 2011
    I had my electronics training back in 1984 and I seem to of forgotten more than I remember. In the following circuit, how is the +11V perm produced starting from U4 working to the left?[​IMG]

    Any help greatly appreciated.
  2. billbehen

    Active Member

    May 10, 2006
    U4 flip-flops, u6 inverters boost level, xfmr blocked by C58, diodes rectifiy signal (smoothed by e'lytic,) r41 prevents core wandering, turns ratio set to put out +11volts. Maybe indicator maybe small amount of DC for something on another board:)
  3. TapOut64

    Thread Starter New Member

    Mar 17, 2011
    OK, don't laugh. So the output of U4 are pulses that trick the transformer into thinking it's seeing AC?
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
    The transformer is not being "tricked". The square-wave output from U6A U6B effectively is an alternating voltage, just not a sinusoidal one. The use of transformers to couple square or pulse waveforms is not all that unusual.

    Whatever else the +11V may be used for, it feeds the input LED of an opto-coupler in what seems like some kind of start-up circuit.
    If -PWR ON is joined to GND, the 11V will drive the input of OP1, so that Q12 will turn on, powering up +15VS and so the PWR ON LED, and in turn U7, and so +5V.

    What is this circuit - some kind of remote control?