Method for driving LED tube lamp
A method for driving an LED tube lamp includes providing a rectifying circuit for receiving an AC supply signal from a rectifying input side, wherein the AC supply signal has frequency of 50 Hz or 60 Hz when the LED tube lamp operates in a ballast-bypass mode, providing a filtering circuit electrically connected to the rectifying circuit, providing a driving circuit electrically connected to the filtering circuit and configured to generate a lamp driving signal to drive an LED module for emitting light, providing a circuit configured for forming a detection path between the rectifying input side and a ground terminal, causing a detection current with pulse waveform to flow through the detection path by turning on and cutting off the detection path, and generating a signal for indicating whether a foreign external impedance is electrically connected to the LED tube lamp in response to the detection current.
1. A method for driving a light-emitting diode (LED) tube lamp, comprising:
providing a rectifying circuit for receiving an AC supply signal from a rectifying input side, wherein the AC supply signal has frequency of 50 Hz or 60 Hz when the LED tube lamp operates in a ballast-bypass mode;
providing a filtering circuit electrically connected to the rectifying circuit;
providing a driving circuit electrically connected to the filtering circuit and configured to generate a lamp driving signal to drive an LED module for emitting light;
providing a circuit configured for forming a detection path between the rectifying input side and a ground terminal;
causing a detection current with pulse waveform to flow through the detection path by turning on and cutting off the detection path; and
generating a signal for indicating whether a foreign external impedance is electrically connected to the LED tube lamp in response to the detection current.
2. The method according to claim 1 , wherein the foreign external impedance is a human body impedance or simulated/test human body impedance.
3. The method according to claim 1 , further comprising:
generating a detection result signal according to the signal for indicating whether the foreign external impedance is electrically connected to the LED tube lamp; and
determining whether to disable the driving circuit according to the detection result signal.
4. The method according to claim 3 , wherein the step of determining whether to disable the driving circuit according to the detection result signal comprises:
disabling the driving circuit when receiving the detection result signal indicating the foreign external impedance is electrically connected to the LED tube lamp; and
not disabling the driving circuit when receiving the detection result signal indicating the foreign external impedance is not electrically connected to the LED tube lamp.
5. The method according to claim 4 , wherein the step of providing the driving circuit electrically connected to the filtering circuit and configured to generate the lamp driving signal to drive the LED module for emitting light comprises:
providing a controller having a power input terminal for receiving a bias voltage, wherein the power input terminal is electrically connected to a circuit configured to perform the step of determining whether to disable the driving circuit according to the detection result signal; and
providing a conversion circuit in the driving circuit, electrically connected to the filtering circuit and configured to perform power conversion, under control by the controller, to convert a signal received from the filtering circuit into the lamp driving signal.
6. The method according to claim 5 , wherein the step of disabling the driving circuit when receiving the detection result signal indicating the foreign external impedance is electrically connected to the LED tube lamp comprises:
adjusting the bias voltage to a level that is not capable of enabling the controller.
7. The method according to claim 6 , further comprising:
providing a transistor having a first terminal electrically connected to the power input terminal, a second terminal electrically connected to the ground terminal, and a control terminal receiving the detection result signal.
8. The method according to claim 7 , wherein the step of adjusting the bias voltage to the level that is not capable of enabling the controller comprises:
electrically connecting the power input terminal to the ground terminal, by turning on the transistor, when receiving the detection result signal in a first state.
9. The method according to claim 5 , wherein the step of not disabling the driving circuit when receiving the detection result signal indicating the foreign external impedance is not electrically connected to the LED tube lamp comprises:
not adjusting the bias voltage, so that the controller is capable of being enabled in response to the bias voltage.
10. The method according to claim 9 , further comprising:
providing a transistor having a first terminal electrically connected to the power input terminal, a second terminal electrically connected to the ground terminal, and a control terminal receiving the detection result signal.
11. The method according to claim 10 , wherein the step of not adjusting the bias voltage, so that the controller is capable of being enabled in response to the bias voltage comprises:
electrically disconnecting the power input terminal from the ground terminal, by turning off the transistor, when receiving the detection result signal in a second state.
12. The method according to claim 3 , wherein the step of providing the driving circuit electrically connected to the filtering circuit and configured to generate the lamp driving signal to drive the LED module for emitting light comprises:
providing a controller having a power input terminal for receiving a bias voltage, wherein the power input terminal is electrically connected to a circuit configured to perform the step of determining whether to disable the driving circuit according to the detection result signal; and
providing a conversion circuit in the driving circuit, electrically connected to the filtering circuit and configured to perform power conversion, under control by the controller, to convert a signal received from the filtering circuit into the lamp driving signal.
13. The method according to claim 12 , further comprising:
providing a transistor having a first terminal electrically connected to the power input terminal, a second terminal electrically connected to the ground terminal, and a control terminal receiving the detection result signal.
14. The method according to claim 13 , further comprising:
electrically connecting the power input terminal to the ground terminal, by turning on the transistor, when receiving the detection result signal in a first state; and
electrically disconnecting the power input terminal from the ground terminal, by turning off the transistor, when receiving the detection result signal in a second state.
15. The method according to claim 1 , further comprising:
generating a pulse signal to turn on and cut off the detection path.
16. The method according to claim 15 , wherein the rectifying input side comprises a first rectifying input terminal and a second rectifying input terminal, and the step of providing the circuit configured for forming the detection path between the rectifying input side and the ground terminal comprises:
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 and a cathode electrically connected to a cathode of the first diode; and
providing a transistor having a first terminal electrically connected to the cathodes of the first and the second diodes, a second terminal electrically connected to the ground terminal, and a control terminal electrically connected to a circuit configured for performing the step of generating the pulse signal to turn on and cut off the detection path.
17. The method according to claim 16 , further comprising:
providing a resistor electrically connected to the transistor in series, wherein the signal on the detection path is generated according to the detection current passing through the resistor.
18. The method according to claim 3 , wherein the step of generating the detection result signal according to the signal for indicating whether the foreign external impedance is electrically connected to the LED tube lamp comprises:
sampling the signal on the detection path according to set time points, and generating a plurality of sample signals, respectively corresponding to the signal on the detection path at different set time points; and
generating the detection result signal according to the sample signals.
19. The method according to claim 18 , wherein the step of sampling the signal on the detection path according to the set time points, and generating the sample signals, respectively corresponding to the signal on the detection path at different set time points comprises:
sampling the signal at a first time point to generate a first sample signal, wherein the first time point is inside of a pulse-on period of the detection current; and
sampling the signal at a second time point to generate a second sample signal, wherein the second time point is outside of the pulse-on period of the detection current.
20. The method according to claim 19 , wherein the step of generating the detection result signal according to the sample signals comprises:
comparing at least two sample signals with each other and generating a comparison result; and
generating the detection result signal according to the comparison result.
21. The method according to claim 20 , wherein the step of comparing at least two sample signals with each other and generating the comparison result comprises:
generating the comparison result having a first logic level when the levels of the first and the second sample signals are substantially equal to each other; and
generating the comparison result having a second logic level when the levels of the first and the second sample signals has a difference exceeding a preset value.
22. The method according to claim 18 , wherein the step of generating the detection result signal according to the sample signals comprises:
comparing at least two sample signals with each other and generating a comparison result; and
generating the detection result signal according to the comparison result.