LED tube lamp with operating modes compatible with electrical ballasts

Patent metadata

Field	Value
Publication number	US-9775215-B2
Application number	US-201615258471-A
Country	US
Kind code	B2
Filing date	Sep 7, 2016
Priority date	Sep 28, 2014
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

An LED tube lamp having an LED unit is disclosed. The LED tube lamp includes a control circuit that selectively determines whether to perform a first mode or a second mode of lighting operation according to a state of a property of an external driving signal and a switching circuit coupled to the control circuit and the LED unit. When the control circuit determines to perform the first mode of lighting operation, the control circuit controls the second circuit in a manner such that the switching circuit maintains its on state to allow continual current to flow through the LED unit, until the external driving signal is disconnected from the LED tube lamp, and when the control circuit determines to perform the second mode of lighting operation, the control circuit controls the switching circuit in a manner to regulate the continuity of current to flow through the LED unit by alternately turning on and off the switching circuit.

First claim

What is claimed is:

1. A light emitting diode (LED) tube lamp configured to receive an external driving signal, comprising:
an LED module configured to emit light, the LED module comprising an LED unit comprising an LED;
a control circuit configured to selectively determine whether to perform a first mode or a second mode of lighting operation according to a state of a property of a received rectified signal produced by a rectifying circuit;
a switching circuit coupled to the control circuit and the LED unit; and
a protection circuit coupled in parallel with the switching circuit, configured to provide protection for the switching circuit;
wherein the control circuit is configured such that when the LED tube lamp performs the first mode of lighting operation, the control circuit allows continual current to flow through the LED unit by maintaining an on state of the switching circuit, until the external driving signal is disconnected from the LED tube lamp; and when the LED tube lamp performs the second mode of lighting operation, the control circuit regulates the continuity of current to flow through the LED unit by alternately turning on and off the switching circuit.

2. The LED tube lamp according to claim 1 , wherein the switching circuit comprises a first electronic switch, and the protection circuit is configured to provide overcurrent protection for the switching circuit and comprises a second electronic switch configured to divert current from flowing through the first electronic switch when a current through the first electronic switch reaches a predefined threshold value.

3. The LED tube lamp according to claim 2 , wherein the protection circuit further comprises a resistor, the first electronic switch comprises a field effect transistor (FET), and the second electronic switch comprises a bipolar junction transistor, wherein the bipolar junction transistor has an emitter, a collector connected to a first terminal of the FET and to the LED unit, and a base connected to a second terminal of the FET; and the resistor is connected between the base and the emitter, wherein the control circuit is configured to control a gate terminal of the FET.

4. The LED tube lamp according to claim 3 , wherein when the LED tube lamp receives the external driving signal, the bipolar junction transistor diverts current from flowing through the first electronic switch as soon as a voltage across the resistor is sufficient to cause the bipolar junction transistor to conduct current.

5. The LED tube lamp according to claim 1 , further comprising a voltage divider configured to produce a first fraction voltage of the rectified signal and a second fraction voltage of the rectified signal, wherein: the property is a voltage level of the rectified signal; the control circuit is configured to determine whether a voltage level of the first fraction voltage is in a first voltage range, and whether a voltage level of the second fraction voltage is in a second voltage range; when the first fraction voltage is in the first voltage range, the control circuit is configured to determine on performing the first mode of lighting operation; and when the second fraction voltage is in the second voltage range, the control circuit is configured to determine on performing the second mode of lighting operation.

6. The LED tube lamp according to claim 5 , wherein at least the control circuit and the voltage divider constitute a mode determination circuit configured to detect a state of the voltage level of the rectified signal.

7. The LED tube lamp according to claim 5 , wherein at least the control circuit and the voltage divider constitute a ballast interface circuit as an interface between the LED tube lamp and an electrical ballast used to supply the LED tube lamp.

8. The LED tube lamp according to claim 5 , wherein the rectifying circuit has a first output terminal and a second output terminal configured to output the rectified signal, and the voltage divider comprises:
a first voltage divider comprising a first resistor and a second resistor connected to each other between the first and second output terminals of the rectifying circuit, to produce the first fraction voltage; and
a second voltage divider comprising a third resistor and a fourth resistor connected to each other between the first and second output terminals of the rectifying circuit, to produce the second fraction voltage;
wherein the control circuit is coupled to a connection node between the first resistor and the second resistor, for receiving the first fraction voltage; and the control circuit is coupled to a connection node between the third resistor and the fourth resistor, for receiving the second fraction voltage.

9. The LED tube lamp according to claim 8 , wherein the second voltage divider further comprises an RC circuit comprising a resistor and a capacitor; one end of the resistor is connected to a connection node between the third resistor and the fourth resistor; another end of the resistor is connected to one end of the capacitor and the control circuit; another end of the capacitor is connected to the second output terminal; and the RC circuit is configured to receive the second fraction voltage and is configured to be charged and discharged repeatedly to alternately turn on and off the switching circuit.

10. The LED tube lamp according to claim 8 , wherein the second voltage divider further comprises a pulse width modulation circuit coupled between the switching circuit and a connection node between the third resistor and the fourth resistor, and the pulse width modulation circuit is configured to: receive the second fraction voltage; produce a pulse signal with a duty-cycle responsive to the second fraction voltage; and alternately turn on and off the switching circuit based on the pulse signal.

11. The LED tube lamp according to claim 8 , wherein the control circuit comprises a pulse width modulation circuit coupled between the switching circuit and a connection node between the third resistor and the fourth resistor, the pulse width modulation circuit is configured to: receive the second fraction voltage; produce a pulse signal with a duty-cycle responsive to the second fraction voltage; and alternately turn on and off the switching circuit based on the pulse signal.

12. The LED tube lamp according to claim 8 , wherein the first voltage range includes values less than a first voltage value or larger than a second voltage value which is larger than the first voltage value; and the voltage divider further comprises at least a diode coupled between the second resistor and the second output terminal, and a voltage drop of the at least a diode when electrically conducting is larger than the first voltage value.

13. The LED tube lamp according to claim 5 , wherein the first voltage range includes values less than a first voltage value or larger than a second voltage value which is larger than the first voltage value; and the second voltage range includes values larger than a third voltage value and less than a fourth voltage value which is larger than the third voltage value.

14. The LED tube lamp according to claim 1 , wherein the property is a voltage level or a frequency level of the rectified signal.

15. The LED tube lamp according to claim 1 , further comprising a noise suppressing circuit comprising an inductor coupled between the LED unit and the switching circuit.

16. The LED tube lamp according to claim 1 , wherein the first mode of lighting operation comprises two first modes of lighting operations, the LED tube lamp is configured to perform one of the

Assignees

• Jiaxing Super Lighting Electric Appliance Co Ltd
• Jiaxing Super Lighting Electric Appliance Co Ltd

Inventors

• Xiong Aiming
• Liu Xintong
• Wu Xiaojia
• Chen Junren

Classifications

• F21K9/278 Primary

  Arrangement or mounting of circuit elements integrated in the light source · CPC title

• F21K9/27

  Retrofit light sources for lighting devices with two fittings for each light source, e.g. for substitution of fluorescent tubes · CPC title

• H05B45/59

  for reducing or suppressing flicker or glow effects · CPC title

• H05B45/50

  responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits · CPC title

• H05B33/0887 Primary

  Electricity · mapped topic