| 摘要 |
The present invention provides an overvoltage protection circuitry for a switching mode power supply (SMPS) DC BUS of an electrical appliance which comprises a field-effect transistor (Q01) to function as a switch for controlling electric current and regulating voltage from a power input supply, a zener diode (TVS1), a resistor (R02) for resisting current into the transistor that will gradually turn on the transistor when a sudden input voltage is higher than a threshold voltage of the zener diode, wherein the transistor will conduct current across the drain to the source of the transistor. An electrolytic capacitor (E01) is added across the transistor's gate and source to form a gate charging circuit to allow the switching mode power supply DC Bus to be slowly charged up. |
