| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply which is available for different operational conditions with a simple constitution and more safety characteristics. SOLUTION: A power supply consists of a switching transformer 2 with a prescribed constitution, a PWM circuit 8, current detection circuits 4 and 6, a decision circuit 10, switch circuits 9, 11, 24, and 29 under the control of a switching signal generating circuit 12. In each operational state, one of the switching circuits 3 and 5 determined according to a selected output voltage is put under a PWM control linked with switching circuits 9, 11, 24, and 29 to obtain a desired stable output voltage on the secondary side of the switching transformer 2. When an abnormal operation is generated, a decision circuit 10 decides abnormality, on the basis of an output of a current detection circuit of a primary-side coil of the switching transformer 2 driven in this state. Then, the oscillation of the PWM circuit 8 is stopped automatically by the output of the decision circuit 8.
|
