| 摘要 |
PURPOSE:To protect a circuit from overvoltage when the power supply is turned on by the use of a simple circuit configuration by furnishing a voltage absorbing circuit to decrease or remove the overvoltage component of a feedback signal to be fed into a switching transistor, wherein the overvoltage component signifies a one at the time when the power supply is turned on. CONSTITUTION:When a DC power is supplied to a circuit, which is composed of a switching transistor 1 and an inverter transformer 3, for ex. by the use of an AC adapter 23, a high voltage corresponding to the no-load voltage on an AC adapter 23 is impressed in the initial period of supplying the power. At first, therefore, a high high-frequency voltage tends to be generated in the primary coil N1 and secondary coils N2, N3 of the inverter transformer 3. However, the overvoltage component of a feedback signal taken out of the secondary coils N2, N3 of the inverter transformer 3 is absorbed by a voltage absorbing circuit 11 and damped. Thus high high-frequency voltage will not be impressed on the input end of the base of switching transistor 1. This provides protection of the circuit from overvoltage when power is supplied, which requires only simple circuit configuration. |
