A heating device, comprising a heating cable and a control circuit;
- wherein
- said heating cable has a core and said core is wound spirally by a heating wire;
- said core and said heating wire are clad in a NTC layer which is wound spirally by a PTC heating wire;
- said NTC layer and said PTC heating wire are clad in an insulating layer;
- a first end of said PTC heating wire is connected to an AC power source 1 via a fuse 3;
- a DC voltage circuit has a first terminal connected to said AC power source via said fuse and produces a DC voltage Vcc at a second terminal of said DC voltage circuit;
- a controller circuit comprises a microcontroller having terminals 6101 to 6118, whose terminals 6114 and 6105 are connected to said Vcc and ground, respectively;
- a first comparator and a second comparator have their power terminals connected to said Vcc, their ground terminals connected to ground, and their output terminals to said terminals 6106 and 6113 of said microcontroller, respectively;
- a synchronous signal input circuit has a first terminal and a second terminal connected to said AC power source via said fuse and said terminal 6103 of said microcontroller, respectively;
- a reference voltage circuit has a first terminal connected to said AC power source via said fuse, a second terminal connected to a positive terminal of said first comparator, a third terminal connected to a negative terminal of said second comparator, a fourth terminal connected to said terminal 6112 of said microcontroller, and a power terminal connected to said Vcc;
- an adjustment circuit has a first terminal connected to said terminal 6112 of said microcontroller, and a second terminal, a third terminal, a fourth terminal connected to said terminals 6111, 6110, and 6109 of said microcontroller, respectively;
- a NTC detection circuit has a first terminal connected to at least an end of said heating wire, a second terminal connected to a negative terminal of said first comparator;
- a PTC detection circuit has a second terminal connected to a positive terminal of said second comparator;
- a switch circuit has a second terminal connected to a first terminal of said PTC detection circuit, and a third terminal connected to said terminal 6117 of said microcontroller;
- a load detection circuit has a first terminal connected to the other end of said PTC heating wire, and a second terminal connected to said terminal 6118 of said microcontroller;
- a protection circuit has a power terminal connected to said Vcc, a first terminal connected to the other end of said PTC heating wire, a second terminal connected to said AC power source via said fuse, and a third terminal connected to a first terminal of said switch circuit;
- and
- a function selection circuit has a first terminal connected to said terminal 6108 of said microcontroller, and a second terminal connected to ground.