Safe electric blanket

A safe electric blanket, comprising a main control circuit, a constant temperature circuit, a detection circuit, a heating wire, an overheat protection circuit for overheat detection and blowout, a power circuit for connecting mains electricity, and a fuse (F1) disposed between the mains electricity and the power circuit;

• the power circuit being connected to one end of the heating wire, the main control circuit, the detection circuit and the overheat protection circuit for supplying power;
• the main control circuit being connected to the detection circuit, the overheat protection circuit and the constant temperature circuit, the overheat protection circuit being connected to the fuse (F1) for controlling the fuse (F1) to blow, the constant temperature circuit being connected to another end of the heating wire for controlling a working state of the heating wire,
• wherein the overheat protection circuit includes a diode (D4), a diode (D3), a transistor (Q2), a resistor (R21), a resistor (R17), a resistor (R39), a resistor (R9), and a temperature detection unit;
• the diode (D4) has a first anode and a first cathode for connecting a null wire of the mains electricity, the diode (D3) has a second anode and a second cathode, the first anode and the second anode are commonly connected to the temperature detection unit through the resistor (R21), the temperature detection unit is connected to the main control circuit through the resistor (R39), the main control circuit is connected to an analog ground through the resistor (R9);
• the second cathode is connected to the analog ground, a base of the transistor (Q2) is connected to the analog ground, an emitter of the transistor (Q2) is connected to the main control circuit through the resistor (R17), and a collector of the transistor (Q2) is connected to the temperature detection unit, and
• wherein the main control circuit is operable to selectively conduct on the transistor (Q2) in response to a signal of temperature abnormality so as to feed a high current that flow, in sequence, through the resistor (21) and the diode (D4) to a null line, wherein the resistor (21) is a heat generation resistor that, through the high current flowing therethrough, generates a high heat that blows the fuse (F1).