LED driving power supply PTC over-temperature protection circuit

Abstract

The utility model relates to the technical field of LED power supplies, in particular to a PTC (Positive Temperature Coefficient) over-temperature protection circuit of an LED driving power supply, which comprises AC (Alternating Current) power supply input ends L and N, the AC power supply input ends L and N are respectively connected with a fuse F1 and a transformer T1, the transformer T1 is connected with a capacitor C1, one end of the capacitor C1 is connected with an inductor L1 and a resistor R1, the output end of the inductor L1 is connected with a diode D1 and a diode D3, one end of the capacitor C1 far away from the inductor L1 is connected with a diode D2 and a diode D4, and the other end of the capacitor C1 far away from the resistor R1 is connected with a diode D1. The output ends of the diode D2 and the diode D4 are connected in parallel with a resistor R2, a resistor R3, a voltage-regulator tube ZD2, a PTC thermistor R4, a capacitor C2 and a resistor R5, the resistor R2 is connected with the resistor R3, the voltage-regulator tube ZD2 is connected in parallel with the PTC thermistor R4, the capacitor C2 and the resistor R5, the resistor R5 is connected in parallel with the capacitor C2, the capacitor C2 is connected with the PTC thermistor R4 and a voltage-regulator tube ZD1, and the voltage-regulator tube ZD1 is connected with a COMP pin of the chip U1. According to the over-temperature protection circuit, when the temperature rises to be greater than the rated temperature of the PTC, the output current is reduced, the LED current and the LED lamp are protected, the service life of the product is prolonged, and the circuit is simple and practical.

Description

Technical Field

[0001] The utility model relates to the technical field of LED power supplies, in particular to a PTC over-temperature protection circuit for an LED driving power supply. Background Art

[0002] In recent years, with the rise of the LED power lighting market, according to statistics, there are more than 300 LED driver power manufacturers in China, of which more than 90% of the main products are low-power LED driver power. Among them, low-power LED driver power is mainly based on flyback LED driver. Since the main considerations of LED power are high PF, high efficiency and low cost, single-stage high PF flyback LED driver power occupies the vast majority of the low-power LED driver power market; flyback LED power can be further divided into primary feedback flyback LED power and secondary feedback flyback LED power. As the performance of optocouplers becomes more and more reliable, secondary feedback LED power relies on optocouplers to achieve high-precision and high-stability secondary feedback control. Secondary feedback LED power once occupied the main LED power market.

[0003] At present, with the intensification of competition in LED power supplies, the control technology performance of primary-side control flyback has been improved, and the current or voltage accuracy of the primary-side control circuit has become better and better. At this time, the advantages of primary-side control have been highlighted, and the primary-side control flyback LED driver power supply has gradually replaced the primary-side feedback LED power supply and occupied the main LED power supply market. However, the primary-side control flyback LED driver power supply does not implement the over-temperature power limit protection very well. Taking the constant current output power supply as an example, in order to achieve a wider temperature output constant current, at the normal working temperature, the CS detection resistor R8 will not achieve power limit protection; if the primary-side control flyback LED driver power supply works at an excessively high temperature, the output is still full power, which may cause the input current to be too large, the heat is serious, and the performance is reduced. In serious cases, the LED driver power supply may be damaged. Utility Model Content

[0004] The purpose of the utility model is to provide a PTC over-temperature protection circuit for an LED driving power supply, so as to solve the technical problems of inconvenience in use, reduction of output current when the temperature is too high, protection of the LED power supply and the LED lamp, and achieve the effect of reducing the heating temperature and extending the service life of the product.

[0005] The utility model discloses a PTC over-temperature protection circuit for an LED driving power supply, comprising AC power input terminals L and N, wherein the AC power input terminals L and N are respectively connected to a fuse F1 and a transformer T1, the transformer T1 is connected to a capacitor C1, one end of the capacitor C1 is connected to an inductor L1 and a resistor R1, the output end of the inductor L1 is connected to a diode D1 and a diode D3, the end of the capacitor C1 away from the inductor L1 is connected to a diode D2 and a diode D4, the output ends of the diodes D2 and D4 are connected in parallel with resistors R2, R3, and a stabilizer The voltage regulator ZD2, the PTC thermistor R4, the capacitor C2 and the resistor R5, the resistor R2 is connected to the resistor R3, the voltage regulator ZD2 is connected in parallel with the PTC thermistor R4, the capacitor C2 and the resistor R5, the resistor R5 is connected in parallel with the capacitor C2, the capacitor C2 is connected to the PTC thermistor R4 and the voltage regulator ZD1, the voltage regulator ZD1 is connected to the COMP pin of the chip U1, the chip U1 is connected to control the LED drive circuit, the output end of the LED drive circuit is connected to LED+ and LED- through a wire, and the LED+ and LED- are connected to an LED lamp.

[0006] Preferably, the LED driving circuit includes an AC input terminal, an output terminal, and an output voltage feedback terminal. According to the CS sampling resistor R8 and the primary-to-secondary turns ratio of the transformer, the COMP compensation voltage is adjusted through temperature changes to control the power tube switch and the output current.

[0007] Compared with the prior art, the beneficial effects of the utility model are:

[0008] The utility model provides a PTC over-temperature protection circuit for an LED driving power supply. By combining a resistor R2, a resistor R3, a voltage regulator ZD1, a PTC thermistor R4, a resistor R5, a capacitor C2 and a voltage regulator ZD1, when the temperature is higher than the rated temperature of the PTC, the PTC resistance value will increase, and the voltage of the COMP pin of U1 will decrease. When the voltage of the COMP pin decreases, the DRV pin of U1 drives the PWM duty cycle to decrease or the PWM frequency to decrease, thereby controlling the output current to decrease, realizing over-temperature output current reduction protection, and achieving the effect of current stabilization. The utility model has a reasonable and simple structure, low cost, and is easy to use. The service life of the product is extended, and the product reliability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The utility model is further described below in conjunction with the accompanying drawings and embodiments:

[0010] Figure 1 The utility model is a schematic diagram of a PTC over-temperature protection circuit of an LED driving power supply. DETAILED DESCRIPTION

[0011] This section will describe in detail the specific embodiments of the utility model. The preferred embodiments of the utility model are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the utility model, but it cannot be understood as a limitation on the protection scope of the utility model.

[0012] like Figure 1 As shown, a PTC over-temperature protection circuit of an LED driving power supply of the utility model includes AC power input terminals L and N, the AC power input terminals L and N are respectively connected to a fuse F1 and a transformer T1, a capacitor C1 is connected to the transformer T1, one end of the capacitor C1 is connected to an inductor L1 and a resistor R1, an output end of the inductor L1 is connected to a diode D1 and a diode D3, an end of the capacitor C1 away from the inductor L1 is connected to a diode D2 and a diode D4, and the output ends of the diodes D2 and D4 are connected in parallel with resistors R2, R3, A voltage regulator tube ZD2, a PTC thermistor R4, a capacitor C2 and a resistor R5, the resistor R2 is connected to the resistor R3, the voltage regulator tube ZD2 is connected in parallel with the PTC thermistor R4, the capacitor C2 and the resistor R5, the resistor R5 is connected in parallel with the capacitor C2, the capacitor C2 is connected to the PTC thermistor R4 and the voltage regulator tube ZD1, the voltage regulator tube ZD1 is connected to the COMP pin of the chip U1, the chip U1 is connected to control the LED drive circuit, the output end of the LED drive circuit is connected to LED+ and LED- through a wire, and the LED+ and LED- are connected to an LED lamp.

[0013] The LED drive circuit includes an AC input terminal, an output terminal, and an output voltage feedback terminal. According to the CS sampling resistor R8 and the primary-to-secondary turns ratio of the transformer, the COMP compensation voltage is adjusted through temperature changes to control the power tube switch and the output current.

[0014] The utility model is a LED driving power supply PTC over-temperature protection circuit, through the combination of resistor R2, resistor R3, voltage regulator ZD1, PTC thermistor R4, resistor R5, capacitor C2, voltage regulator ZD1, when the temperature is higher than the PTC rated temperature, the PTC resistance value will increase, the voltage of the COMP pin of U1 will decrease, when the voltage of the COMP pin decreases, the DRV pin of U1 drives the PWM duty cycle to decrease or the PWM frequency to decrease, thereby controlling the output current to decrease, realizing over-temperature output current protection, the effect of current stabilization, reasonable and simple structure, low cost, easy to use, extending the product life, and improving product reliability. Among them, ZD1 selects a voltage regulator with small leakage current to achieve normal working voltage, high temperature or low temperature does not affect the output current.

[0015] For example: the following relationship between PTC protection current and temperature can be realized

[0016] Ambient temperature / ℃ Output current percentage 80 100％ 85 100％ 90 95％ 95 80％ 100 60％ 105 40％ 110 20％

[0017]

[0018] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A PTC over-temperature protection circuit for an LED driving power supply, comprising AC power input terminals L and N, characterized in that: The AC power input terminals L and N are connected to the fuse F1 and the transformer T1 respectively. The transformer T1 is connected to the capacitor C1. One end of the capacitor C1 is connected to the inductor L1 and the resistor R1. The output end of the inductor L1 is connected to the diode D1 and the diode D3. The end of the capacitor C1 away from the inductor L1 is connected to the diode D2 and the diode D4. The output ends of the diode D2 and the diode D4 are connected in parallel with the resistor R2, the resistor R3, the zener tube ZD2, the PTC thermistor R4, the capacitor C2 and the resistor R5. The resistor R2 is connected to the resistor R3. The zener tube ZD2 is connected in parallel with the PTC thermistor R4, the capacitor C2 and the resistor R5. The resistor R5 is connected in parallel with the capacitor C2. The capacitor C2 is connected to the PTC thermistor R4 and the zener tube ZD1. The zener tube ZD1 is connected to the COMP pin of the chip U1. The chip U1 is connected to control the LED drive circuit. The output end of the LED drive circuit is connected to LED+ and LED- through wires. The LED+ and LED- are connected to LED lamps.

2. The LED driving power supply PTC over-temperature protection circuit according to claim 1, characterized in that: The LED driving circuit includes an AC input terminal, an output terminal, and an output voltage feedback terminal. According to the CS sampling resistor R8 and the primary-to-secondary turns ratio of the transformer, the COMP compensation voltage is adjusted through temperature changes to control the power tube switch and the output current.

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