| 摘要 |
PURPOSE:To perform the overvoltage protecting function of a switching power source circuit by controlling the element of an output side by an overvoltage protecting circuit provided at the output side of an insulating converter transformer. CONSTITUTION:A switching power source circuit has a DC main power source circuit of a power source block substrate 6 side, a converter 1 of control block substrate 7 side, an insulating converter transformer PIT, a magnetic flux controlling saturable transformer PRT and an error detector 3 for controlling it, and an overvoltage protecting circuit 11 at the converter transformer PIT side. Thus, the output voltage E01 of the secondary winding N12 of the transformer PIT is compared by the error detector 3 with a reference voltage D32, the current Ic of the primary current N31 of the transformer PRT is controlled to maintain its output voltage E01 at the prescribed value. Further, when the circuit 11 detects an overvoltage, a transistor Q14 is turned OFF to turn the current Ic of the primary winding N31 OFF. |
