| 摘要 |
PURPOSE: A power supply circuit for a power control integrated circuit in an off mode of a switching mode type power supply device is provided so that circuit damage due to heat generation can be prevented and a production cost can be remarkably cut down by using one transistor and one diode, instead of using two transistors. CONSTITUTION: An anode terminal of a diode(D11) is connected to a transformer(T1) of the switching mode type power supply device, and a cathode terminal of the diode(D11) is connected respectively to a base terminal and a collector terminal of an npn transistor(Q30) through resistances(R21, R22). The base terminal of the npn transistor(Q30) is grounded through a Zenor diode(ZD), and an emitter terminal of the npn transistor(Q30) is connected to a power terminal of the power control integrated circuit through a diode(D10) for preventing a mis-operation. Here, the diode(D10) for preventing the mis-operation has an operation voltage of 0.7V, and is a non-amplifying device. In a normal mode, the anode terminal of the diode(D11) has a voltage of about 80V, and the anode terminal of a diode(D12) has a voltage of about 16V. Thus, the npn transistor(Q30) is maintained off, and the power control integrated circuit receives power from the diode(D12). In an off mode, the power control integrated circuit receives power from the transformer(T1) through the diode(D11) and the npn transistor(Q30).
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