| 摘要 |
PURPOSE:To improve the stability of a power supply circuit by connecting a switching circuit in parallel to the secondary side of a current transformer to keep the output voltage of the power supply circuit at a fixed level. CONSTITUTION:A transistor (TR) T2 is connected in parallel to the output terminal of a rectifier 11 at the secondary side of a current transformer and opens and closes the output terminal of the rectifier 11 in response to the output signal of a control circuit 14. Then the collector of a TRT2 is connected to a positive polarity terminal at the output side of the rectifier 11 together with the emitter connected to a negative polarity terminal of the output side of the rectifier 11 respectively. In addition, the base of the TRT2 is connected to the output terminal of the circuit 14. The circuit 14 always monitors the output voltage +VDD of a smoothing circuit 17 consisting of a diode 2 and a capacitor C3. Then the circuit 14 makes the TRT2 conduct when the voltage +VDD exceeds a prescribed level and then puts the TRT2 under a nonconduction state when the +VDD is lower than the prescribed level by means of the control signal respectively. |
