Need help with voltage regulator control loop

Discussion in 'The Projects Forum' started by BigD61, Nov 10, 2014.

  1. BigD61

    Thread Starter New Member

    Nov 8, 2014
    Have developed a pre-regualor using a SCR to control voltage on output capacitor of the prereg. Circuit consists of a series of oneshots pulse generators that control when the SCR is turned on along the trailing edge of 120 Hz rectified waveform. The variable pulse is controlled by voltage control pin of 555 timer. My circuit will track the precision regulator voltage output. Problem is, this establishes a fixed point and as load current demand is increased the the output to the prereg capacitor drops, requiring move the SCR trigger to a earlier point along the rectified cycle. Experiments show the 555 VC pin must stay within limits or the it will not produce a pules and no SCR trigger is developed. Circuit goal is to track Precision PS output (+ 6Volts), maintain pre-regulator voltage around 5% would work, limit error control voltage (555 VC) to range of 1.2 to 6.2 Vdc.
    General voltage relationships: Vpre = 34V, Vout = 28V, VC = 1.2V and Vpre = 14V, Vout = 8, VC = 5.2. I need some ideas as to how to have the control loop have sufficient gain to move the VC as required without going outside of the VC limits of 1.0 - 6.2.
    Note can not attach PDF block diagram and schematic, error message "upload file is empty" I can open files with Adobe XI, what's wrong with my procedure?