LED tube lamp
An LED tube lamp including an LED module and a power supply module is provided. The LED module is configured to emit light in response to a driving current. The power supply module is electrically connected to the LED module to provide the driving current based on an external driving signal. The power supply module includes a rectifying circuit, a filtering circuit, a driving circuit, a flicker suppression circuit, and an installation detection circuit. The flicker suppression circuit is electrically connected to the LED module, and configured to control a conduction state of a current path passing through the LED module. The installation detection circuit is electrically connected to the flicker suppression circuit, and configured to detect whether a foreign external impedance is electrically connected to the LED tube lamp. When the foreign external impedance is detected, the installation detection circuit disables the flicker suppression circuit to restrict current from flowing through the current path. When the foreign external impedance is not detected, the installation detection circuit enables the flicker suppression circuit to smooth the driving current by controlling the conduction state based on the external driving signal.
1. An LED tube lamp comprising:
an LED module, configured to emit light in response to a driving current; and
a power supply module, electrically connected to the LED module to provide the driving current based on an external driving signal, wherein the power supply module comprises:
a rectifying circuit, configured to receive the external driving signal;
a filtering circuit, electrically connected to an output terminal of the rectifying circuit;
a driving circuit, electrically connected to an output terminal of the filtering circuit and the LED module, and configured to convert a signal received from the filtering circuit into the driving current and transmit the driving current to the LED module through a first driving output terminal and a second driving output terminal;
a flicker suppression circuit, electrically connected to the LED module, and configured to control a conduction state of a current path passing through the LED module; and
an installation detection circuit, electrically connected to the flicker suppression circuit, and configured to detect whether a foreign external impedance is electrically connected to the LED tube lamp,
wherein when the foreign external impedance is detected, the installation detection circuit disables the flicker suppression circuit to restrict current from flowing through the current path, and
wherein when the foreign external impedance is not detected, the installation detection circuit enables the flicker suppression circuit to smooth the driving current by controlling the conduction state based on the external driving signal.
2. The LED tube lamp according to claim 1 , wherein the flicker suppression circuit comprises:
a voltage generating circuit, configured to generate a reference voltage;
an operational amplifier, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the operational amplifier is electrically connected to the voltage generating circuit to receive the reference voltage;
a resistor, having a first end electrically connected to the second input terminal of the operational amplifier, and a second end electrically connected to the second driving output terminal of the driving circuit; and
a first transistor, having a first terminal electrically connected to the LED module, a second terminal electrically connected to the second input terminal of the operational amplifier and the first end of the resistor, and a control terminal electrically connected to the output terminal of the operational amplifier.
3. The LED tube lamp according to claim 2 , wherein the installation detection circuit transmits an installation state signal, indicating whether the foreign external impedance is electrically connected to the LED tube lamp, to the voltage generating circuit,
wherein when the installation state signal indicates the foreign external impedance is electrically connected to the LED tube lamp, the voltage generating circuit adjusts the reference voltage to a low level to cause the operational amplifier to output a disabling signal for turning off the first transistor.
4. The LED tube lamp according to claim 2 , wherein the installation detection circuit comprises a bias adjustment circuit, electrically connected to an enabling terminal of one of the voltage generating circuit and the operational amplifier,
wherein when the foreign external impedance is detected to be electrically connected to the LED tube lamp, the bias adjustment circuit pulls a voltage at the enabling terminal to a ground level.
5. The LED tube lamp according to claim 4 , wherein the bias adjustment circuit comprises:
a second transistor, having a first terminal electrically connected to the enabling terminal, a second terminal electrically connected to the ground level, and a control terminal configured to receive an installation state signal for indicating whether the foreign external impedance is electrically connected to the LED tube lamp.
6. The LED tube lamp according to claim 5 , wherein the power supply module further comprises:
a ballast detection module, electrically connected to the installation detection circuit, and configured to detect whether the external driving signal is provided from an electronic ballast,
wherein when the external driving signal is provided from the electronic ballast, the ballast detection module dominates the flicker suppression circuit to be enabled no matter whether the foreign external impedance is detected by the installation detection circuit.
7. The LED tube lamp according to claim 6 , wherein the ballast detection module comprises:
a first diode, having an anode and a cathode, wherein the anode of the first diode receives the external driving signal;
a second diode, having an anode and a cathode, wherein the anode of the second diode is electrically connected to the anode of the first diode;
a capacitor, electrically connected between the cathodes of the first and the second diodes; and
a zener diode, electrically connected to the capacitor in parallel.
8. An LED tube lamp, comprising:
an LED module, configured to emit light in response to a driving current; and
a power supply module, electrically connected to the LED module to provide the driving current based on an external driving signal, wherein the power supply module comprises:
an installation detection circuit, configured to detect whether a foreign external impedance is electrically connected to the LED tube lamp, wherein the installation detection circuit comprises a detection controller configured to issue a control signal and a current limiting circuit configured to affect magnitude of current on the power supply module in response to the control signal; and
a ballast detection circuit, electrically connected to the installation detection circuit, and configured to detect whether the external driving signal is provided from an electronic ballast,
wherein when the foreign external impedance is detected, the detection controller issues the control signal to cause the current limiting circuit to limit the current to less than a safety value,
wherein when the external driving signal is provided from the electronic ballast, the ballast detection circuit maintains the control signal at a level capable of causing the current limiting circuit to not limit the current on the power supply module no matter whether the foreign external impedance is detected.
9. The LED tube lamp according to claim 8 , wherein the ballast detection circuit comprises:
a first diode, having an anode for receiving the external driving signal and a cathode electrically connected to an output terminal of the detection controller;
a second diode, having an anode electrically connected to the anode of the first diode and a cathode electrically connected to a ground level;
a capacitor, electrically connected between the cathodes of the first and the second diodes; and
a zener diode, electrically connected to the capacitor in parallel.
10. The LED tube lamp according to claim 8 , wherein the current limiting circuit is further configured to smooth the current by controlling the magnitude of the current based on the external driving signal.
11. The LED tube lamp according to claim 10 , wherein the current limiting circuit comprises:
a voltage generating circuit, configured to generate a reference voltage;
an operational amplifier, having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the operational amplifier is electrically connected to the voltage generating circuit to receive the reference voltage;
a resistor, having a first end electrically connected to the second input terminal of the operational amplifier, and a second end electrically connected a driving output terminal of a driving circuit; and
a first transistor, having a first terminal electrically connected to the LED module, a second terminal electrically connected to the second input terminal of the operational amplifier and the first end of the resistor, and a control terminal electrically connected to the output terminal of the operational amplifier.
12. The LED tube lamp according to claim 11 , wherein when the foreign external impedance is electrically connected to the LED tube lamp, the voltage generating circuit adjusts, in response to the control signal, the reference voltage to a low level to cause the operational amplifier to output a disabling signal for turning off the first transistor.
13. The LED tube lamp according to claim 11 , wherein the current limiting circuit further comprises a bias adjustment circuit, electrically connected to an enabling terminal of one of the voltage generating circuit and the operational amplifier,
wherein when the foreign external impedance is detected to be electrically connected to the LED tube lamp, the bias adjustment circuit pulls a voltage at the enabling terminal to a ground level.
14. The LED tube lamp according to claim 13 , wherein the bias adjustment circuit comprises:
a second transistor, having a first terminal electrically connected to the enabling terminal, a second terminal electrically connected to the ground level, and a control terminal configured to receive the control signal.