Offset voltage eliminating circuit structure for protection mechanism of dimmer

An offset voltage eliminating circuit structure for a protection mechanism of a dimmer, comprising:

• a constant current source including an output for outputting a stable current, the output connected with a dimming signal input through a current-limiting resistor, the dimming signal input connected with an output of an external traditional dimmer;
• a subtractor formed by a third operational amplifier and second, third, fourth and fifth resistors that have the same resistances, the second and the third resistors connected in series, and the non-inverting input of the third operational amplifier connected between the second and the third resistors R2 and R3, the other end of the second resistor connected with the output, and the other end of the third resistor connected to ground, the fourth and the fifth resistors connected in series, and the inverting input of the third operational amplifier connected between the fourth and the fifth resistors, the other end of the fourth resistor connected between the output and the inverting input of the third operational amplifier, and the other end of the fifth resistor being input with an offset reference voltage;
• and
• a hysteresis comparator including a non-inverting input, an inverting input and an output capable of outputting a GD pulse signal, the non-inverting input connected to the output of the third operational amplifier, and the inverting input being input with a saw-tooth wave.