LED lamp and temperature control circuit applied thereto
The present invention provides an LED lamp and a temperature control circuit applied to the LED lamp. The LED lamp includes at least one LED unit, a magnetic ballast, and an LED drive circuit. The magnetic ballast is coupled to a power and configured to limit and stabilize a received alternating current. The LED drive circuit includes a temperature control circuit. The temperature control circuit is coupled to the magnetic ballast and connected in parallel with the LED unit, is configured to detect an internal temperature of the LED lamp and adjust an output power of the LED unit, and includes a thermal sensitive module having a negative temperature coefficient thermistor and a phase cut circuit. The phase cut circuit is coupled to the thermal sensitive module, and adjusts the output power of the LED unit by decreasing a resistance of the negative temperature coefficient thermistor when the negative temperature coefficient thermistor detects that the internal temperature of the LED lamp is higher than a specified temperature threshold.
1. A LED lamp, comprising:
at least one LED unit; a magnetic ballast, coupled to a power and configured to transfer a received first alternating current to a first direct current; and
a LED drive circuit, comprising a temperature control circuit coupled to the magnetic ballast and in parallel with the LED unit, configured to detect an internal temperature of the LED lamp and adjust an output power of the LED unit, wherein, the temperature control circuit comprises:
a thermal sensitive module, comprising a negative temperature coefficient thermistor; and
a phase cut circuit coupled to the thermal sensitive module, wherein when the internal temperature of the LED lamp detected by the thermal sensitive module is higher than a temperature threshold, a resistance of the negative temperature coefficient thermistor is decreased to adjust the output power of the LED unit, wherein the phase cut circuit is configured to cut off a portion of a half cycle of an output voltage of the LED unit when the internal temperature of the LED lamp is higher than the temperature threshold.
2. The LED lamp according to claim 1 , wherein the phase cut circuit is a lead phase cut circuit, comprising a first switch and a first capacitance, the first capacitance and the negative temperature coefficient thermistor are connected in series and coupled to two ends of the magnetic ballast, a control terminal of the first switch is connected to a common terminal of the first capacitance and the negative temperature coefficient thermistor.
3. The LED lamp according to claim 2 , wherein when the internal temperature of the LED lamp increases, the resistance of the negative temperature coefficient thermistor is decreased, a control terminal voltage of the first switch is increased; when the internal temperature of the LED lamp is higher than the temperature threshold, the first switch is on, the current transferred to the LED unit is decreased to lower the output power of the LED unit.
4. The LED lamp according to claim 2 , wherein the first switch is a thyristor, a trigger terminal of the thyristor is the control terminal of the first switch, and an anode and a cathode terminals of the thyristor are coupled to two ends of the LED unit, respectively.
5. The LED lamp according to claim 2 , wherein the phase cut circuit further comprises a first resistance connected in series with the negative temperature coefficient thermistor, and the first resistance is configured to control the temperature threshold or the range of the output power of the LED unit.
6. The LED lamp according to claim 1 , wherein the phase cut circuit is a trailing phase cut circuit, the trailing phase cut circuit and the negative temperature coefficient thermistor are connected in parallel and coupled to two ends of the magnetic ballast.
7. The LED lamp according to claim 6 , wherein when the internal temperature of the LED lamp is higher than the temperature threshold, the resistance of the negative temperature coefficient thermistor is decreased to make the trailing phase cut circuit on, the current transferred to the LED unit is decreased to lower the output power of the LED unit.
8. The LED lamp according to claim 1 , wherein the drive circuit further comprises a rectifier circuit and a filtration circuit connected in parallel and coupled between the temperature control circuit and the LED unit, the rectifier circuit and the filtration circuit are configured to transfer a second direct current to a second alternating current, the rectifier circuit and the filtration circuit comprise a rectifier bridge and an electrolytic capacitor connected in parallel.
9. A temperature control circuit, coupled between a magnetic ballast and at least one LED unit, wherein, the temperature control circuit comprises:
a thermal sensitive module, comprises a negative temperature coefficient thermistor; and
a phase cut circuit is coupled to the thermal sensitive module, when the internal temperature of a LED lamp detected by the thermal sensitive module is higher than a temperature threshold, a resistance of the negative temperature coefficient thermistor is decreased to adjust the output power of the LED unit, wherein the phase cut circuit is configured to cut off a portion of a half cycle of an output voltage of the LED unit when the internal temperature of the LED lamp is higher than the temperature threshold.
10. A LED lamp, comprising:
at least one LED unit; a magnetic ballast, coupled to a power and configured to transfer a received first alternating current to a first direct current; and
a LED drive circuit, comprising a temperature control circuit coupled to the magnetic ballast and in parallel with the LED unit, configured to detect an internal temperature of the LED lamp and adjust an output power of the LED unit, wherein, the temperature control circuit comprises:
a thermal sensitive module, comprising a negative temperature coefficient thermistor; and
a phase cut circuit coupled to the thermal sensitive module, wherein when the internal temperature of the LED lamp detected by the thermal sensitive module is higher than a temperature threshold, a resistance of the negative temperature coefficient thermistor is decreased to adjust the output power of the LED unit, wherein the phase cut circuit is a trailing phase cut circuit, the trailing phase cut circuit and the negative temperature coefficient thermistor are connected in parallel and coupled to two ends of the magnetic ballast.
11. The LED lamp according to claim 10 , wherein when the internal temperature of the LED lamp is higher than the temperature threshold, the resistance of the negative temperature coefficient thermistor is decreased to make the trailing phase cut circuit on, the current transferred to the LED unit is decreased to lower the output power of the LED unit.
12. The LED lamp according to claim 10 , wherein the drive circuit further comprises a rectifier circuit and a filtration circuit connected in parallel and coupled between the temperature control circuit and the LED unit, the rectifier circuit and the filtration circuit are configured to transfer a second direct current to a second alternating current, the rectifier circuit and the filtration circuit comprise a rectifier bridge and an electrolytic capacitor connected in parallel.