| 摘要 |
PURPOSE:To obtain a protecting circuit of a simple configuration by setting the pulse width of a high frequency control pulse to zero by breaking means when the voltage of an auxiliary power source decreases to the prescribed value or lower, thereby shutting OFF the output voltage. CONSTITUTION:A switching regulator is composed of rectifying and smoothing circuits 1, 4 a switching transistor (Tr)2, and a ferrite transformer 3, and the Tr2 is driven by a control pulse pulse-width-modulated by a controller 6. A stator 7, and a protecting circuit 11 having chevron-shaped dropping characteristic are provided, and a protecting circuit 13 having shutting-off characteristic is provided. Thus, when a load malfunction occurs, the auxiliary power source voltage + or -Vs of an auxiliary winding 5 drops in response to the output voltage, the circuit 11 is operated to limit the output voltage in chevron-shaped drooping. When the drooping point arrives at a point A, the protecting circuit 13 of the shutting-off characteristic is operated to set the pulse width of the control pulse to zero by a shutting-off Tr17 to completely shut off the output current. |
