other end a 2 of the alternating current module the negative half cycle rectifying branch includes a third rectifying tube d 3 a fourth rectifying tube d 4 and a fifth rectifying tube d 5 not shown in the drawing wherein a negative terminal of the third rectifying tube d 3 is connected with the one end a 1 of the alternating current module and a positive terminal of the third rectifying tube d 3 is connected with the output terminal of the external led module a positive terminal of the fifth rectifying tube d 5 is connected with the other end a 2 of the alternating current module and a negative terminal of the fifth rectifying tube d 5 is connected with a positive terminal of the fourth rectifying tube d 4 a negative terminal of the fourth rectifying tube d 4 is connected with the input terminal of the external led module the positive half cycle feeding branch includes a first capacitor c 1 and a fourth capacitor c 4 not shown in the drawing wherein one end of the first capacitor c 1 is connected with the positive terminal of the fourth rectifying tube d 4 and the other end of the first capacitor c 1 is connected with the one end a 1 of the alternating current module and one end of the fourth capacitor c 4 is connected with the other end a 2 of the alternating current module and the.