| 摘要 |
PURPOSE:To stabilize a DC output voltage, to suppress heat generation, and to reduce parts in size by turning on and off an SCR by a control pulse and a fly-back pulse from a constant voltage power supply device. CONSTITUTION:An AC input is converted into an astable DC output by the rectifying circuit consisting of diodes D8-D11 and it is smoothed by a capacitor C6. Once the AC input is applied, the gate voltage of the SCR is biased more positively than the cathode voltage and the SCR turns on to enter a conductive state. Consequently, the circuit current flows from a ground side to the secondary winding Le of a fly-back transformer T2 to flow in the order of the anode and cathode of the SCR, the capacitor C6, the primary winding Lc of the transformer T2, the collector and emitter of a horizontal output transistor Q4, and the ground. When the horizontal output circuit starts operating, a fly-back pulse is generated in a horizontal fly-back period and this appears with the negative polarity at the secondary winding Ld of the transformer T2. This pulse allows the anode current of the SCR to decrease gradually and when it is ceased, the SCR turns off to enter a nonconductive state. |
