LED tube lamp

• US 10,342,078 B2
• Filed: 07/03/2018
• Issued: 07/02/2019
• Est. Priority Date: 09/28/2014
• Status: Active Grant

• Current Assignee: Jiaxing Super Lighting Electric Appliance Co., Ltd.
• Original Assignee: Jiaxing Super Lighting Electric Appliance Co., Ltd.
• Inventors: Jiang, Tao, Ye, Qifeng, Zhang, Yueqiang
• Primary Examiner(s): Tan, Vibol
• Application Number:
  US16/026,331
• Publication Number:
  US 20180317291A1
• Time in Patent Office: 364 Days
• CPC Class Codes: F21K 9/27 Retrofit light sources for lighting devices with two fittings for each light source, e.g. for substitution of fluorescent tubes
• CPC Class Codes: F21K 9/278 Arrangement or mounting of circuit elements integrated in the light source
• CPC Class Codes: F21V 19/003 Fastening of light source holders, e.g. of circuit boards or substrates holding light sources
• CPC Class Codes: F21V 23/009 the casing being inside the housing of the lighting device
• CPC Class Codes: F21V 23/023 Power supplies in a casing F21V23/003 takes precedence
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/32 Pulse-control circuits
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/392 wherein the LEDs are placed as freewheeling diodes at the secondary side of an isolation transformer
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An LED tube lamp comprises a tube, an LED light strip inside the tube, a plurality of LED light sources on the LED light strip, a power supply, and a first and a second end caps. The power supply comprises a circuit board, a plurality of electronic components and a heat-dissipating element. The plurality of electronic components and the heat-dissipating element are on the circuit board. The first end cap and the second end cap are respectively attached at two ends of the tube. The first end cap comprises a lateral wall and an end wall having an opening. The lateral wall is substantially coaxial with the tube and connected to the tube. The end wall is substantially perpendicular to an axial direction of the lateral wall and connected to an end of the lateral wall away from the tube. At least some of the plurality of electronic components and the heat-dissipating element are disposed inside the first end cap. The heat-dissipating element is closer to the opening on the end wall of the first end cap than the electronic components in the end cap are.

Claims

1. An LED tube lamp, comprising:

a tube;

an LED light strip disposed inside the tube;

a plurality of LED light sources mounted on the LED light strip;

a power supply comprising a circuit board, a plurality of electronic components and a heat-dissipating element, wherein at least a part of the plurality of electronic components and the heat-dissipating element are on the circuit board; and

a first end cap and a second end cap respectively attached at two ends of the tube, each of the first and second end caps comprising a lateral wall and an end wall having an opening, the lateral wall substantially coaxial with the tube and connected to the tube, the end wall substantially perpendicular to an axial direction of the lateral wall and connected to an end of the lateral wall away from the tube,

wherein the circuit board is inside the first end cap, and the heat-dissipating element is disposed closer to the opening on the end wall of the first end cap than are the plurality of the electronic components disposed in the first end cap.

2. The LED tube lamp as claimed in claim 1, wherein all of the electronic components are disposed inside the first end cap.

3. The LED tube lamp as claimed in claim 1, wherein the circuit board is parallel to the axial direction of the lateral wall.

4. The LED tube lamp as claimed in claim 1, further comprising a first pin and a second pin coupled to the first end cap, wherein the first pin and the second pin are hollow conductive pins and the power supply electrically connects the first pin and the second pin.

5. The LED tube lamp as claimed in claim 4, wherein the heat-dissipating element extends between the circuit board and the end wall of the first end cap, and wherein a portion of the heat-dissipating element is mounted on the circuit board and another portion of the heat-dissipating element is disposed in the opening of the end wall of the first end cap.

6. The LED tube lamp as claimed in claim 5, wherein the heat-dissipating element is made of metal.

7. The LED tube lamp as claimed in claim 1, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap and wherein the power supply comprises:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are configured for rectifying an external driving signal to produce a rectified signal; and

a driving circuit coupled to the first and second rectifying circuits and the LED light sources, and configured to drive the LED light sources,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube; and

the LED tube lamp is configured such that when the external driving signal is a low frequency signal, the LED tube lamp causes the rectified signal to be used by the driving circuit for driving the LED light sources to emit light.

8. The LED tube lamp as claimed in claim 7, wherein the external driving signal is a low frequency signal having a frequency between 0 and 60 Hz.

9. The LED tube lamp as claimed in claim 7, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode of the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

10. The LED tube lamp as claimed in claim 9, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin, and further wherein a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.

11. The LED tube lamp as claimed in claim 7, wherein when the external driving signal provided by an electrical ballast is input through one of the first and second pins and the third pin across the two ends of the lamp tube, the driving circuit does not drive the LED light sources to emit light.

12. The LED tube lamp as claimed in claim 11, wherein when the external driving signal provided by an electrical ballast is input across the two ends of the lamp tube, the rectified signal bypasses at least a component of the driving circuit and the driving circuit drives the LED light sources to emit light.

13. The LED tube lamp as claimed in claim 1, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap, and wherein the power supply comprises:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are configured for rectifying an external driving signal to produce a rectified signal; and

a detection circuit coupled to the first and second rectifying circuits and the LED light sources, and configured for determining whether to cause the LED light sources to be driven by the rectified signal, or to prevent the LED light sources from being driven by the rectified signal,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube.

14. The LED tube lamp as claimed in claim 13, wherein the power supply further comprises a driving circuit coupled to the first and second rectifying circuits and the LED light sources and configured to drive the LED light sources.

15. The LED tube lamp as claimed in claim 14, wherein when the external driving signal is a low frequency signal from an AC powerline, the driving circuit is configured for driving the LED light sources to emit light.

16. The LED tube lamp as claimed in claim 14, wherein the detection circuit comprises a mode switching circuit coupled to the first and second rectifying circuits and the driving circuit, and configured to cause the rectified signal to be used by the driving circuit when the external driving signal is a low frequency signal from an AC powerline.

17. The LED tube lamp as claimed in claim 14, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

18. The LED tube lamp as claimed in claim 17, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin;

and a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.

19. The LED tube lamp as claimed in claim 1, wherein the power supply further comprises another circuit board, a plurality of another electronic components and another heat-dissipating element, at least a part of the plurality of another electronic components and the another heat-dissipating element are on the another circuit board, the another circuit board is inside the second end cap, and the another heat-dissipating element is closer to the opening on the end wall of the second end cap than are the part of the plurality of the another electronic components in the second end cap.

20. The LED tube lamp as claimed in claim 19, further comprising a first pin and a second pin coupled to the first end cap, wherein the first pin and the second pin are hollow conductive pins, and the first part of the plurality of electronic components are coupled to the first pin and the second pin.

21. The LED tube lamp as claimed in claim 20, further comprising a third pin and a fourth pin coupled to the second end cap, wherein the third pin and the fourth pin are hollow conductive pins, and the second part of the plurality of electronic components are coupled to the third pin and the fourth pin.

22. The LED tube lamp as claimed in claim 21, wherein the another heat-dissipating element extends between the another circuit board and the end wall of the second end cap, and wherein a portion of the another second heat-dissipating element is on the another circuit board and another portion of the another heat-dissipating element is in the opening of the end wall of the second end cap.

23. An LED tube lamp, comprising:

a tube;

an LED light strip disposed inside the tube;

a plurality of LED light sources mounted on the LED light strip;

a power supply comprising a first circuit board, a plurality of electronic components and a first heat-dissipating element, the first heat-dissipating element mounted on the circuit board; and

a first end cap and a second end cap respectively attached at two ends of the tube, each of the first and the second end caps comprising a lateral wall and an end wall having an opening, the lateral wall substantially coaxial with the tube and connected to the tube, the end wall substantially perpendicular to an axial direction of the lateral wall and connected to an end of the lateral wall away from the tube,

wherein the first circuit board is disposed inside the first end cap, the first heat-dissipating element extends between the first circuit board and the end wall of the first end cap, and further wherein a portion of the first heat-dissipating element is mounted on the first circuit board and another portion of the heat-dissipating element is disposed in the opening of the end wall of the first end cap.

24. The LED tube lamp as claimed in claim 23, the power supply further comprising a second circuit board and a second heat-dissipating element, wherein the second heat-dissipating element is mounted on the second circuit board.

25. The LED tube lamp as claimed in claim 24, wherein the second circuit board is disposed inside the second end cap, the second heat-dissipating element extends between the second circuit board and the end wall of the second end cap, and further wherein a portion of the second heat-dissipating element is mounted on the second circuit board and another portion of the heat-dissipating element is disposed in the opening of the end wall of the second end cap.

26. The LED tube lamp as claimed in claim 25, further comprising a first pin and a second pin coupled to the first end cap, wherein the first pin and the second pin are hollow conductive pins and the power supply is coupled to the first pin and the second pin.

27. The LED tube lamp as claimed in claim 26, further comprising a third pin and a fourth pin coupled to the second end cap, wherein the third pin and the fourth pin are hollow conductive pins and the power supply is coupled to the third pin and the fourth pin.

28. The LED tube lamp as claimed in claim 27, wherein the first and the second heat-dissipating elements are made of metal.

29. The LED tube lamp as claimed in claim 25, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap and further wherein the power supply comprising:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are for rectifying an external driving signal to produce a rectified signal; and

a driving circuit coupled to the two rectifying circuits and the LED light sources, and configured to drive the LED light sources,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube; and

the LED tube lamp is configured such that when the external driving signal is a low frequency signal, the LED tube lamp causes the rectified signal to be used by the driving circuit for driving the LED light sources to emit light.

30. The LED tube lamp as claimed in claim 29, wherein the external driving signal is a low frequency signal having a frequency between 0 and 60 Hz.

31. The LED tube lamp as claimed in claim 29, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode of the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

32. The LED tube lamp as claimed in claim 31, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin, and further wherein a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.

33. The LED tube lamp as claimed in claim 29, wherein when the external driving signal provided by an electrical ballast is input through one of the first and second pins and the third pin across the two ends of the lamp tube, the driving circuit does not drive the LED light sources to emit light.

34. The LED tube lamp as claimed in claim 33, wherein when the external driving signal provided by an electrical ballast is input across the two ends of the lamp tube, the rectified signal bypasses at least a component of the driving circuit, and the driving circuit drives the LED light sources to emit light.

35. The LED tube lamp as claimed in claim 25, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap, and further wherein the power supply comprising:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are configured for rectifying an external driving signal to produce a rectified signal; and

a detection circuit coupled to the first and second rectifying circuits and the LED light sources, and configured for determining whether to cause the LED light sources to be driven by the rectified signal, or to prevent the LED light sources from being driven by the rectified signal,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube.

36. The LED tube lamp as claimed in claim 35, wherein the power supply further comprises a driving circuit coupled to the first and second rectifying circuits and the LED light sources, and configured to drive the LED light sources.

37. The LED tube lamp as claimed in claim 36, wherein when the external driving signal is a low frequency signal from an AC powerline the driving circuit is configured for driving the LED light sources to emit light.

38. The LED tube lamp as claimed in claim 36, wherein the detection circuit comprises a mode switching circuit coupled to the first and second rectifying circuits and the driving circuit, and configured to cause the rectified signal to be used by the driving circuit when the external driving signal is a low frequency signal from an AC powerline.

39. The LED tube lamp as claimed in claim 35, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

40. The LED tube lamp as claimed in claim 39, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin;

and a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.

41. An LED tube lamp, comprising:

a tube;

an LED light strip disposed inside the tube;

a plurality of LED light sources mounted on the LED light strip;

a first end cap and a second end cap respectively attached at two ends of the tube, each of the first end cap and the second end cap comprising a lateral wall and an end wall having an opening, the lateral wall substantially coaxial with the tube and connected to the tube, the end wall substantially perpendicular to an axial direction of the lateral wall and connected to an end of the lateral wall away from the tube; and

a power supply comprising a first electronic component, a second electronic component and a first heat-dissipating element, wherein the first electronic component generates more heat than the second electronic component, and the first electronic component, the second electronic component and the heat-dissipating element are disposed inside the first end cap;

wherein the first electronic component is disposed closer to the opening on the end well of the first end cap than the second electronic component is.

42. The LED tube lamp as claimed in claim 41, wherein the power supply further comprising a first circuit board, wherein the first electronic component, the second electronic component and the first heat-dissipating element are mounted on the first circuit board.

43. The LED tube lamp as claimed in claim 42, wherein the first electronic component is one of an inductor, a transistor, a resistor and an integrated circuit.

44. The LED tube lamp as claimed in claim 42, wherein the first heat-dissipating element extends between the first circuit board and the end wall of the first end cap, a portion of the first heat-dissipating element is mounted on the first circuit board and another portion of the first heat-dissipating element is in the opening of the end wall of the first end cap.

45. The LED tube lamp as claimed in claim 44, further comprising a first pin and a second pin coupled to the first end cap, wherein the first pin and the second pin are hollow conductive pins and the power supply is coupled to the first pin and the second pin.

46. The LED tube lamp as claimed in claim 45, the power supply further comprising a third electronic component, a fourth electronic component and a second heat-dissipating element, wherein the third electronic component generates more heat than the fourth electronic component, and the third electronic component, the fourth electronic component and the second heat-dissipating element are disposed inside the second end cap, further wherein the third electronic component is disposed closer to the opening on the end well of the second end cap than the fourth electronic component is.

47. The LED tube lamp as claimed in claim 46, wherein the power supply further comprising a second circuit board, wherein the third electronic component, the fourth electronic component and the second heat-dissipating element are mounted on the second circuit board.

48. The LED tube lamp as claimed in claim 47, wherein the third electronic component is one of an inductor, a transistor, a resistor and an integrated circuit.

49. The LED tube lamp as claimed in claim 47, wherein the second heat-dissipating element extends between the second circuit board and the end wall of the second end cap, a portion of the second heat-dissipating element is mounted on the second circuit board and another portion of the second heat-dissipating element is in the opening of the end wall of the second end cap.

50. The LED tube lamp as claimed in claim 49, further comprising a third pin and a fourth pin coupled to the second end cap, wherein the third pin and the fourth pin are hollow conductive pins and the power supply is coupled to the third pin and the fourth pin.

51. The LED tube lamp as claimed in claim 49, wherein the first and second heat-dissipating elements are made of a metal material.

52. The LED tube lamp as claimed in claim 45, wherein the power supply comprises a driving module for driving the plurality of LED light sources, wherein the driving module comprises the first electronic component.

53. The LED tube lamp as claimed in claim 52, wherein the first electronic component is one of an inductor, a transistor, a resistor, an integrated circuit and a diode.

54. The LED tube lamp as claimed in claim 53, wherein the power supply further comprising a second circuit board disposed inside the second end cap, wherein a temperature-sensitive component is disposed on the second circuit board.

55. The LED tube lamp as claimed in claim 54, wherein the temperature-sensitive component is an electrolytic capacitor.

56. The LED tube lamp as claimed in claim 41, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap, and wherein the power supply comprising:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are configured for rectifying an external driving signal to produce a rectified signal; and

a driving circuit coupled to the two rectifying circuits and the LED light sources, and configured to drive the LED light sources,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is a low frequency signal input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube; and

the LED tube lamp is configured such that when the external driving signal is a low frequency signal, the LED tube lamp causes the rectified signal to be used by the driving circuit for driving the LED light sources to emit light.

57. The LED tube lamp as claimed in claim 56, wherein the external driving signal is a low frequency signal having a frequency between 0 and 60 Hz.

58. The LED tube lamp as claimed in claim 56, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode of the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

59. The LED tube lamp as claimed in claim 58, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin;

and a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.

60. The LED tube lamp as claimed in claim 56, wherein when the external driving signal provided by an electrical ballast is input through one of the first and second pins and the third pin across the two ends of the lamp tube, the driving circuit does not drive the LED light sources to emit light.

61. The LED tube lamp as claimed in claim 60, wherein when the external driving signal provided by an electrical ballast is input across the two ends of the lamp tube, the rectified signal bypasses at least a component of the driving circuit, and then drives the LED light sources to emit light.

62. The LED tube lamp as claimed in claim 41, further comprising a first pin and a second pin coupled to one of the first and second end caps, and a third pin coupled to the other end cap, and wherein the power supply comprising:

a first rectifying circuit connected to the first and second pins;

a second rectifying circuit connected to the third pin and an output terminal of the first rectifying circuit, wherein the first and second rectifying circuits are for rectifying an external driving signal to produce a rectified signal; and

a detection circuit coupled to the two rectifying circuits and the LED light sources, and configured for determining whether to cause the LED light sources to be driven by the rectified signal, or to prevent the LED light sources from being driven by the rectified signal,

wherein the LED tube lamp is configured to receive the external driving signal and emit light in each of two power supply arrangements, a first power supply arrangement being that the external driving signal is input and transmitted through the first and second pins, and a second power supply arrangement being that the external driving signal is input and transmitted through one of the first and second pins and through the third pin across the two ends of the lamp tube.

63. The LED tube lamp as claimed in claim 62, wherein the power supply further comprises a driving circuit coupled to the two rectifying circuits and the LED light sources, and configured to drive the LED light sources.

64. The LED tube lamp as claimed in claim 63, wherein when the external driving signal is a low frequency signal from an AC powerline, the LED tube lamp causes the rectified signal to be used by the driving circuit for driving the LED light sources to emit light.

65. The LED tube lamp as claimed in claim 63, wherein the detection circuit comprises a mode switching circuit coupled to the two rectifying circuits and the driving circuit, and configured to cause the rectified signal to be used by the driving circuit when the external driving signal is a low frequency signal from an AC powerline.

66. The LED tube lamp as claimed in claim 62, wherein the first rectifying circuit comprises a first diode, a second diode, a third diode and a fourth diode, the first pin is connected to a first common node connecting an anode of the first diode and a cathode the second diode, and the second pin is connected to a second common node connecting an anode of the third diode and a cathode of the fourth diode.

67. The LED tube lamp as claimed in claim 66, wherein the second rectifying circuit comprises a fifth diode and a sixth diode and has a third common node connecting an anode of the fifth diode and a cathode of the sixth diode of the second rectifying circuit, and the third common node is coupled to the third pin;

and a common anode of the second and the fourth diodes of the first rectifying circuit is coupled to an anode of one of the fifth and sixth diodes of the second rectifying circuit, and a common cathode of the first and third diodes of the first rectifying circuit is coupled to a cathode of the other one of the fifth and sixth diodes of the second rectifying circuit.