| 摘要 |
An automatic input switching circuit for a power supply includes a transformer with two primary windings, normally connected in series and connectible in parallel by relay contacts for operation in a doubler mode. The secondary winding supplies a rectifier for developing a DC output voltage and a voltage doubler for developing a higher voltage than the output voltage. The voltage doubler charges a capacitor that stores energy for operating the relay when a transistor switch is closed. The transistor switch is normally held in a nonconductive state by an inhibit transistor driven from a comparator that switches states when the voltage across the capacitor reached a predetermined level. A voltage sensing arrangement compares the rectifier output voltage with a reference voltage and when it reaches a certain level, another comparator switches states to activate a disable transistor. The activated disable transistor prevents cutting off of the inhibit transistor, thus preventing operation of the transistor switch. The arrangement may be used above as an automatic voltage doubler power supply with line isolation or, by adding additional relay contacts, as a relay control device for controlling normal doubling mode switching in a high current, switched mode power supply.
|
