| 摘要 |
A power supply having power efficient improved by constant-voltage control, which has a transformer 1 for dropping voltage, a rectification filter 4 and a voltage output 6 for supplying uniform output voltage all the time without regard to voltage variation is provided. When the AC voltage at HI port of the transformer 1 is applied to the anode of a diode D2, the AC voltage is rectified and smoothed to be sent to a regulator 16. The AC voltage is supplied as the bias voltage of first and second schmitt triggers 11 and 12 and bias voltage of first and second reference voltage ports 9 and 10. The first and second schmitt trigger compare the reference voltage with the voltage, and apply a high-level signal to the base of a transistor Q1 through a resistor R5 when the compared voltage does not reach voltage currently set, thereby turning on the transistor Q1. This flows bias current to the induction coil of a first relay 13 to switch a node contact NC to a node contact NO. Here, excessive voltage is not applied to a power transistor 15 because the second schmitt trigger 12 does not operate, generating no unnecessary heat. Accordingly, the power efficient is improved and heat sink size is reduced.
|
