Voltage control and control of electric flow pattern are to show the sampling of pair of feedback signal is different, voltage control is feedback signal with the output voltage of power source, the deviation classics comparator of this feedback signal and set-point compares generation to control pulse with toothed wave after enlarge. And electric current control is with high frequency transformer electric current of former edge output is sampling feedback signal to comprise voltaic closed circuit, with voltage feedback signal comprises voltage outer shroud, the output deviation of voltage outer shroud regards electric current as core give, with electric current feedback signal produces control pulse quite, following plan institute show block diagram of two kinds of construction of system that control fashion:

 

 

Two kinds of implementation principle pictures that dominate means pursue as follows be shown:

 

 

Amplifier of the PI of classics of deviation signal E that voltage control will output voltage and Vref of VR reference voltage error and the toothed wave that the oscillator generates undertake comparative, generation PWM controls pulse, if the graph is shown 5 times,its output weaveform.

 

Electric current control has channel of two closed circuit, amplifier of the PI of classics of deviation signal E of voltage and Vref of VR referenced voltage error be able to voltage Ve, this voltage and switch are in charge of leakage pole to output electric current to undertake comparative, generation PWM controls pulse, if the graph is shown 6 times,its output weaveform.

 

 

Chip of voltage pilot model if: TL494, TOP system;

 

Chip of model of electric current pilot if: UC3842