LED tube lamp
A ballast-bypass light-emitting diode (LED) tube lamp includes at least a first and second external connection terminal, the first and second external connection terminals respectively connected to opposite sides of the ballast by-pass LED tube lamp. The tube lamp includes an LED module, configured to emit light in response to a driving current, and a power supply module, electrically connected to the first and second external connection terminals for receiving an AC driving signal and configured to provide the driving current to the LED module. The power supply module comprises a rectifying circuit, a filtering circuit, a driving circuit, and a circuit electrically connected to the driving circuit and configured to operate in response to whether a foreign external impedance is connected to the LED tube lamp. When part of the LED tube lamp is electrically connected to an external power source and the foreign external impedance is electrically connected to the LED tube lamp, the first circuit disables the driving circuit so as to limit the generation of the driving current to prevent the LED module from emitting light based on the driving current. When both ends of the LED tube lamp are electrically connected to an external power source and the foreign external impedance is not electrically connected to the LED tube lamp, the first circuit enables the driving circuit so as to not limit the generation of the driving current in order to allow the LED module to emitting light based on the driving current.
1. A method for driving a ballast-bypass light-emitting diode (LED) tube lamp, comprising:
providing a rectifying circuit for receiving an AC driving signal from a first rectifying input terminal and a second rectifying input terminal;
providing a filtering circuit electrically connected to the rectifying circuit via a first rectifying output terminal and a second rectifying output terminal;
providing a driving circuit electrically connected to the filtering circuit for supplying a driving current to an LED module;
detecting whether a foreign external impedance is electrically connected to the LED tube lamp;
disabling the driving circuit so as to limit generation of the driving current to prevent the LED module from emitting light when part of the LED tube lamp is electrically connected to an external power source and the foreign external impedance is electrically connected to the LED tube lamp; and
enabling the driving circuit so as to not limit the generation of the driving current in order to allow the LED module to emitting light when both ends of the LED tube lamp are electrically connected to the external power source and the foreign external impedance is not electrically connected to the LED tube lamp.
2. The method according to claim 1 , wherein the step of providing the driving circuit electrically connected to the filtering circuit for supply the driving current to the LED module comprises:
providing a controller having a power input terminal and configured to control the generation of the driving current.
3. The method according to claim 2 , wherein the step of detecting whether the foreign external impedance is electrically connected to the LED tube lamp comprises:
detecting a signal on a detection path, wherein the detection path is a branch circuit extending from a power loop of the LED tube lamp; and
determining whether the foreign external impedance is electrically connected to the LED tube lamp based on the signal detected on the detection path.
4. The method according to claim 3 , wherein the step of disabling the driving circuit so as to limit generation of the driving current to prevent the LED module from emitting light comprises:
generating an adjustment control signal with a first level when the signal detected on the detection path indicates the foreign external impedance is electrically connected to the LED tube lamp; and
adjusting, in response to the adjustment control signal with the first level, a signal level on the power input terminal to a level that is not capable of enabling the driving circuit.
5. The method according to claim 4 , wherein adjusting the signal level on the power input terminal to the level that is not capable of enabling the driving circuit comprises:
electrically connecting the power input terminal to a ground terminal by turning on a transistor connected to the power input terminal.
6. The method according to claim 4 , wherein the step of enabling the driving circuit so as to not limit the generation of the driving current in order to allow the LED module to emitting light comprises:
generating an adjustment control signal with a second level when the signal detected on the detection path indicates the foreign external impedance is not electrically connected to the LED tube lamp; and
allowing, in response to the adjustment control signal with the second level, a signal level on the power input terminal to be charged to a level that is capable of enabling the driving circuit.
7. The method according to claim 6 , wherein allowing the signal level on the power input terminal to be charged to the level that is capable of enabling the driving circuit comprises:
electrically disconnecting the power input terminal from a ground terminal by turning off a transistor connected to the power input terminal.
8. The method according to claim 3 , wherein the step of detecting the signal on the detection path comprises:
receiving a pulse signal by the detection path, so as to allow a current to flow through the detection path during a limited time frame.
9. The method according to claim 8 , further comprising:
providing a resistor and a transistor electrically connected to the resistor in series to form the detection path, wherein the transistor is configured to turn on or cut off in response to the pulse signal.
10. The method according to claim 9 , wherein the detection path is electrically connected to the first rectifying output terminal via a first detection connection terminal, and is electrically connected to the second rectifying output terminal via a second detection connection terminal.
11. The method according to claim 10 , further comprising:
providing a current limiting element electrically connected between the first rectifying output terminal and the filtering circuit, and configured to limit direction of current on the power loop.
12. The method according to claim 11 , wherein the step of providing the current limiting element electrically connected between the first rectifying output terminal and the filtering circuit comprises:
providing a diode having an anode electrically connected to the first rectifying output terminal and the resistor via the first detection connection terminal and a cathode electrically connected to the filtering circuit.
13. The method according to claim 11 , wherein the step of providing the current limiting element electrically connected between the first rectifying output terminal and the filtering circuit comprises:
providing a diode having an anode electrically connected to the first rectifying output terminal and the transistor via the first detection connection terminal and a cathode electrically connected to the filtering circuit.
14. The method according to claim 8 , further comprising:
providing a resistor, a transistor electrically connected to the resistor in series, a first diode, and a second diode to form the detection path, wherein the transistor is configured to turn on or cut off in response to the pulse signal,
wherein the first diode has an anode electrically connected to the first rectifying input terminal and a cathode electrically connected to the resistor via a first detection connection terminal, and
wherein the second diode has an anode electrically connected to the second rectifying input terminal and a cathode electrically connected to the resistor via a first detection connection terminal.
15. The method according to claim 3 , wherein the step of detecting the signal on the detection path comprises:
sampling the signal on the detection path according to a set time point and generating a plurality of sample signals, respectively corresponding to the signal on the detection path, at different time points.
16. The method according to claim 15 , wherein the step of determining whether the foreign external impedance is electrically connected to the LED tube lamp based on the signal detected on the detection path comprises:
comparing at least two sample signals with each other and generating a comparison result; and
generating an adjustment control signal according to the comparison result.
17. The method according to claim 3 , wherein the detection path is electrically connected to the first rectifying output terminal via a first detection connection terminal, and is electrically connected to the second rectifying output terminal via a second detection connection terminal.
18. The method according to claim 17 , further comprising:
providing a current limiting element electrically connected between the first rectifying output terminal and the filtering circuit, and configured to limit direction of current on the power loop.
19. The method according to claim 18 , wherein the step of providing the current limiting element electrically connected between the first rectifying output terminal and the filtering circuit comprises:
providing a diode having an anode electrically connected to the first rectifying output terminal and at least one of a resistor and a transistor included in the detection path via the first detection connection terminal and a cathode electrically connected to the filtering circuit.
20. The method according to claim 3 , further comprising:
providing a first diode having an anode electrically connected to the first rectifying input terminal;
providing a second diode having an anode electrically connected to the second rectifying input terminal;
providing a resistor having a first end electrically connected to cathodes of the first and the second diodes; and
providing a transistor electrically connected between a second end of the resistor and the second rectifying output terminal.