Patent ID: 8159799

Claim:
A protective device against abnormality for positive and negative dual power supply circuit, comprising: a dual power OCL power circuit including a positive power supply and a negative power supply; a series current negative feedback resistor located in a last stage output terminal load of the dual power OCL power circuit as a detection source; an integration circuit connected to the series current negative feedback resistor, the integration circuit including a resistor and a capacitor; a voltage dependent switching unit branch circuit connected to the integration circuit; a diode branch circuit connected to the integration circuit; and an overload shutdown device, the overload shutdown device being normally shut down and being conducting when the integration circuit determines that an overcurrent caused by abnormality of either the positive power supply or the negative power supply occurs, wherein the dual power OCL power circuit further includes: a transformer, a first diode, a first, positive-way rectifying capacitor connected to the first diode, and first light rays, wherein the first diode and the first capacitor filter a voltage generated by the transformer and output a first voltage between a positive terminal and a negative terminal of the first capacitor; a second diode, a second, positive-way rectifying capacitor connected to the second diode, and the first light rays, wherein the second diode and the second capacitor filter a voltage generated by the transformer, a positive terminal of the second capacitor being connected to the positive terminal of the first capacitor through the first light rays and constituting the positive power supply of the dual power OCL power circuit, a value of a voltage outputted by the positive power supply being one half of the first voltage; a third capacitor having a negative terminal being connected to the negative terminal of the first capacitor through a second light rays and constituting the negative power supply of the dual power OCL power circuit, a value of a voltage outputted by the negative power supply being one half of the first voltage; and a fourth capacitor having a negative terminal adjacent to and connected to a positive terminal of the third capacitor and being connected to ground, wherein when a load of the second capacitor and the third capacitor is overcurrent, a voltage drop is generated by the series current negative feedback resistor, thereby the integration circuit determines that an abnormality of the positive power supply occurs and renders the overload shutdown device conducting, and when a load of the fourth capacitor is overcurrent, a voltage rise is generated between the positive terminal and the negative terminal of each of the second and third capacitors, thereby the integration circuit determines that an abnormality of the negative power supply occurs and renders the overload shutdown device conducting through the voltage dependent switching unit.