LED drive over-temperature protection control method and circuit

Abstract

The present invention discloses an LED drive over-temperature protection control method and circuit. First, the circuit parameters of the over-temperature protection control circuit are designed so that the over-temperature protection control circuit outputs different preset voltages at different ambient temperatures; then, the over-temperature protection control circuit is connected to the current sampling pin of the driver chip of the LED driver circuit, and the output current of the driver chip is changed by the preset voltage. The method and circuit specifically include an external power supply, a voltage stabilizing module, a thermistor, a voltage divider resistor and a diode. The output end of the external power supply is connected to the input end of the voltage stabilizing module, the output end of the voltage stabilizing module is connected to one end of the thermistor, the other end of the thermistor is simultaneously connected to the positive pole of the diode and one end of the voltage divider resistor, the negative pole of the diode is connected to the current sampling pin of the driver chip in the LED driver circuit, and the other end of the voltage divider resistor is grounded. The present invention improves the temperature effect of the LED driver circuit while ensuring that the circuit is simple and has strong practicality.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to an LED drive over-temperature protection control method and circuit. Background Art

[0002] In the LED lighting industry, due to the working environment and climate change, lamps may work in unconventional environments, such as when the ambient temperature is higher than the rated maximum operating temperature of the lamp itself. If the lamp works in a high temperature environment for a long time, it will affect the life of the lamp or even damage the lamp. Therefore, some high-quality LED lighting lamps need to have a temperature protection function. At present, there are two ways to drive the temperature protection function of LED lamps:

[0003] 1. The driver IC (microelectronic chip) chip itself has temperature protection, which is characterized by a temperature protection node of 125°-150°; the disadvantage is that if the chip temperature really reaches 125-150 degrees before entering temperature protection, other components inside the driver are likely to be damaged. For example, capacitor products generally have an operating temperature of less than 105 degrees.

[0004] 2. By adjusting the PWM / DIM pin of the driver IC, the temperature control is achieved with the characteristic of complex peripheral NTC detection circuit and signal feedback circuit; the disadvantage is that the peripheral circuit is complex, there are many components and the cost is high.

[0005] It can be seen that the existing temperature protection method has poor protection effect, complex circuit and low practicality. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide an LED drive over-temperature protection control method and circuit, which can improve the temperature effect of the LED drive circuit while ensuring that the circuit is simple and practical.

[0007] In order to solve the above problems, the solution adopted by the present invention is:

[0008] A method for controlling over-temperature protection of LED driving comprises the following steps:

[0009] S1. Designing circuit parameters of an over-temperature protection control circuit so that the over-temperature protection control circuit outputs different preset voltages at different ambient temperatures;

[0010] S2. Connect the over-temperature protection control circuit to the current sampling pin of the driver chip of the LED driver circuit, and change the output current of the driver chip by the preset voltage.

[0011] In order to solve the above problem, another solution adopted by the present invention is:

[0012] An LED drive over-temperature protection control circuit, applied to the above-mentioned LED drive over-temperature protection control method, comprises an external power supply, a voltage stabilizing module, a thermistor, a voltage dividing resistor and a diode;

[0013] The output end of the external power supply is connected to the input end of the voltage stabilizing module, the output end of the voltage stabilizing module is connected to one end of the thermistor, the other end of the thermistor is simultaneously connected to the positive electrode of the diode and one end of the voltage divider resistor, the negative electrode of the diode is connected to the current sampling pin of the driving chip in the LED driving circuit, and the other end of the voltage divider resistor is grounded.

[0014] In summary, the beneficial effects of the present invention are: providing an LED driver over-temperature protection control method and circuit, by controlling the detection voltage of the current sampling pin of the driver chip to adjust the output current of the driver chip, thereby realizing temperature control, and being able to make different degrees of adjustment according to different ambient temperatures, with good protection effect, and the circuit only needs to use thermistors and voltage divider resistors as the main components to achieve different voltage divider outputs according to temperature changes, and the circuit structure is simple and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the steps of an LED drive over-temperature protection control method according to an embodiment of the present invention;

[0016] Figure 2 A circuit connection diagram of an over-temperature protection control circuit of an LED driving over-temperature protection control circuit according to an embodiment of the present invention connected to an LED driving circuit;

[0017] Figure 3 The present invention is a schematic diagram of an over-temperature protection control circuit of an LED driving over-temperature protection control circuit according to an embodiment of the present invention.

[0018] Description of labels:

[0019] 1. Over temperature protection control circuit;

[0020] C1, first filter capacitor; C2, second filter capacitor;

[0021] D1, diode;

[0022] R1, voltage-dividing resistor; R2, current-limiting resistor; RT1, thermistor;

[0023] VCC, external power supply;

[0024] U1, driver chip;

[0025] Z1, Zener diode. DETAILED DESCRIPTION

[0026] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0027] Please refer to Figure 1 , a LED driver over-temperature protection control method, comprising the following steps:

[0028] S1. Designing circuit parameters of the over-temperature protection control circuit 1 so that the over-temperature protection control circuit 1 outputs different preset voltages at different ambient temperatures;

[0029] S2. Connect the over-temperature protection control circuit 1 to the current sampling pin of the driver chip U1 of the LED driver circuit, and change the output current of the driver chip U1 through the preset voltage.

[0030] From the above description, it can be seen that the beneficial effects of the present invention are: by controlling the detection voltage of the current sampling pin of the driver chip U1, the output current of the driver chip U1 is adjusted to achieve temperature control, and different degrees of adjustment can be made according to different ambient temperatures, with good protection effect, and a more common over-temperature control circuit is used for regulation, and its circuit structure is simple and practical.

[0031] Furthermore, before step S1, the following steps are also included:

[0032] S0. Select multiple voltage values ​​within the magnitude range of the peak voltage of the current sampling pin of the driving chip U1 as the preset voltage.

[0033] From the above description, it can be seen that when designing the over-temperature protection control circuit 1, the size range of the peak voltage of the current sampling pin of the driver chip U1 is used as the data basis, and the value of the preset voltage value is refined to adapt to the actual situation of the driver chip U1, so as to achieve a better over-temperature control effect.

[0034] Furthermore, the output current of the driver chip U1 is changed by the preset voltage as follows:

[0035] The peak voltage of the current sampling pin of the driver chip U1 is changed by the preset voltage to change the output current of the driver chip U1. The expression is as follows:

[0036]

[0037] Among them, I OUT Represents the output current of the driver chip U1, V cspk represents the peak voltage of the current sampling pin of the driver chip U1, Rcs represents the resistance of the sampling resistor externally connected to the current sampling pin of the driver chip U1, T onIndicates the turn-on time of the driver chip U1, T demag represents the demagnetization time of the driving chip U1, and T represents the switching period of the driving chip U1.

[0038] From the above description, it can be seen that the peak voltage of the current sampling pin of the driver chip U1 is changed by a preset voltage to change the output current of the driver chip U1, that is, to change the output power of the driver chip U1. When the temperature of the LED driver circuit is too high, the output power of the driver chip U1 is gradually reduced according to the actual temperature change to protect the driver chip U1 and other components of the circuit.

[0039] Please refer to Figure 2 and Figure 3 , an LED drive over-temperature protection control circuit, applied to the above-mentioned LED drive over-temperature protection control method, including an external power supply VCC, a voltage regulator module, a thermistor RT1, a voltage divider resistor R1 and a diode D1;

[0040] The output end of the external power supply VCC is connected to the input end of the voltage stabilizing module, the output end of the voltage stabilizing module is connected to one end of the thermistor RT1, the other end of the thermistor RT1 is simultaneously connected to the positive electrode of the diode D1 and one end of the voltage divider resistor R1, the negative electrode of the diode D1 is connected to the current sampling pin of the driving chip U1 in the LED driving circuit, and the other end of the voltage divider resistor R1 is grounded.

[0041] From the above description, it can be seen that the beneficial effects of the present invention are: the most basic voltage divider circuit is composed of the thermistor RT1 and the voltage divider resistor R1, the voltage stabilizing module outputs a stable voltage, and the voltage is then divided and transmitted to the current sampling pin of the driver chip U1 through the diode D1. According to the different ambient temperatures, the resistance value of the thermistor RT1 changes accordingly, thereby affecting the voltage division and changing the voltage output of the circuit. The circuit structure is simple and practical.

[0042] Furthermore, the voltage stabilizing module includes a current limiting resistor R2 and a voltage stabilizing diode Z1;

[0043] One end of the current limiting resistor R2 is connected to the output end of the external power supply VCC, the other end of the current limiting resistor R2 is connected to both the negative electrode of the voltage regulator tube and the end of the thermistor RT1 away from the voltage divider resistor R1, and the positive electrode of the voltage regulator tube is grounded.

[0044] From the above description, it can be seen that the voltage stabilizing circuit is composed of the current limiting resistor R2 and the voltage stabilizing diode Z1 to output a stable voltage to the thermistor RT1 to ensure that the over-temperature protection control circuit 1 has a stable voltage output, thereby ensuring that the output power regulation of the driver chip U1 is sufficiently accurate and the stable operation of the LED driver circuit is guaranteed.

[0045] Furthermore, the over-temperature protection control circuit 1 also includes a first filter capacitor C1;

[0046] One end of the first filter capacitor C1 is connected to the output end of the voltage stabilizing module and one end of the thermistor RT1 away from the voltage divider resistor R1 , and the other end of the first filter capacitor C1 is grounded.

[0047] From the above description, it can be seen that the first filter capacitor C1 is arranged at the output end of the voltage stabilizing module, which can reduce the AC ripple coefficient of the output voltage of the voltage stabilizing module and obtain a smoother and more stable output.

[0048] Furthermore, the over-temperature protection control circuit 1 also includes a second filter capacitor C2;

[0049] One end of the second filter capacitor C2 is connected to the anode of the diode D1 , and the other end of the second filter capacitor C2 is grounded.

[0050] From the above description, it can be seen that the second filter capacitor C2 is connected between the voltage-dividing resistor R1 and the diode D1, so that the voltage output of the circuit is smoother and more stable.

[0051] An LED drive over-temperature protection control method and circuit of the present invention are suitable for application scenarios in which an LED drive circuit performs over-temperature protection, and are specifically described below in conjunction with specific embodiments:

[0052] Please refer to Figure 1 , Embodiment 1 of the present invention is:

[0053] A LED driver over-temperature protection control method, such as Figure 1 As shown, the following steps are included:

[0054] S0. Take multiple voltage values ​​within the magnitude range of the peak voltage of the current sampling pin of the driver chip U1 as preset voltage values.

[0055] S1. Designing circuit parameters of the over-temperature protection control circuit 1 so that the over-temperature protection control circuit 1 outputs different preset voltages at different ambient temperatures;

[0056] S2. Connect the over-temperature protection control circuit 1 to the current sampling pin of the driver chip U1 of the LED driver circuit, and change the output current of the driver chip U1 through a preset voltage.

[0057] In this embodiment, the output current of the driver chip U1 is changed by the preset voltage as follows:

[0058] The peak voltage of the current sampling pin of the driver chip U1 is changed by a preset voltage to change the output current of the driver chip U1. The expression is as follows:

[0059]

[0060] Among them, I OUT Represents the output current of driver chip U1, V cspk represents the peak voltage of the current sampling pin of the driver chip U1, Rcs represents the resistance of the sampling resistor connected to the current sampling pin of the driver chip U1, T on Indicates the turn-on time of driver chip U1, T demag represents the demagnetization time of the driver chip U1, and T represents the switching cycle of the driver chip U1. The above formula mainly uses the constant current principle of the BUCK circuit inside the driver chip U1, and generates a reference signal to control the current sampling pin of the driver chip U1 through demagnetization time detection and switching cycle detection, thereby achieving the purpose of constant current output.

[0061] In this embodiment, the specific principle of realizing over-temperature protection is as follows: when the ambient temperature becomes high, after a preset voltage is input into the current sampling pin of the driver chip U1, the voltage difference value of the voltage originally collected on the current sampling pin of the driver chip U1 is reduced, thereby reducing the actual peak voltage of the current sampling pin of the driver chip U1, resulting in a reduction in the output current of the driver chip U1, thereby reducing the output power of the driver chip U1.

[0062] Please refer to Figure 2 and Figure 3 , Embodiment 2 of the present invention is:

[0063] An LED driver over-temperature protection control circuit is applied to an LED driver over-temperature protection control method of embodiment 1, such as Figure 2 and Figure 3 As shown, it includes an external power supply VCC, a voltage stabilizing module, a thermistor RT1, a voltage dividing resistor R1, a diode D1, a first filter capacitor C1 and a first filter capacitor C2. Among them, the output end of the external power supply VCC is connected to the input end of the voltage stabilizing module, the output end of the voltage stabilizing module is connected to one end of the thermistor RT1, the other end of the thermistor RT1 is simultaneously connected to the positive electrode of the diode D1 and one end of the voltage dividing resistor R1, the negative electrode of the diode D1 is connected to the current sampling pin of the driver chip U1 in the LED driver circuit, and the other end of the voltage dividing resistor R1 is grounded. One end of the first filter capacitor C1 is simultaneously connected to the output end of the voltage stabilizing module and the end of the thermistor RT1 away from the voltage dividing resistor R1, and the other end of the first filter capacitor C1 is grounded. One end of the second filter capacitor C2 is connected to the positive electrode of the diode D1, and the other end of the second filter capacitor C2 is grounded.

[0064] In this embodiment, the external power source VCC may be provided by a transformer-coupled feedback circuit in the LED driving circuit.

[0065] In this embodiment, as shown in the figure, the voltage stabilizing module includes a current limiting resistor R2 and a voltage stabilizing diode Z1. One end of the current limiting resistor R2 is connected to the output end of the external power supply VCC, the other end of the current limiting resistor R2 is connected to the negative electrode of the voltage stabilizing tube and the end of the thermistor RT1 away from the voltage dividing resistor R1, and the positive electrode of the voltage stabilizing tube is grounded.

[0066] In this embodiment, the operation process of an LED driving over-temperature protection control circuit is as follows:

[0067] First, the output of the external power supply VCC passes through the voltage stabilization module composed of the current limiting resistor R2 and the voltage stabilizing diode Z1 to obtain a stable output voltage and add it to the series circuit composed of the thermistor RT1 and the voltage divider resistor R1;

[0068] Then, when the temperature in the environment of the LED driving circuit changes, such as some components are seriously heated and the temperature rises, the resistance of the thermistor RT1 decreases accordingly, the voltage that the voltage divider resistor R1 can obtain becomes larger, and the output voltage of the over-temperature protection control circuit 1 increases; on the contrary, when the temperature in the circuit decreases, the resistance of the thermistor RT1 increases accordingly, the voltage that the voltage divider resistor R1 can obtain becomes smaller, and the output voltage of the over-temperature protection control circuit 1 decreases;

[0069] Finally, the output of the over-temperature protection control circuit 1 is fed into the current sampling pin of the driver chip U1, thereby changing the output current of the driver chip U1, thereby achieving the effect of changing the circuit temperature to protect various components from damage.

[0070] The following is an example of the parameter design of the circuit used to implement the above process:

[0071] Select the voltage divider resistor R1 as 4.7K, the second filter capacitor C2 as 100nF, and the thermistor RT1 as 25°100K resistance parameters. We can calculate that when the ambient temperature is within 60°, the voltage divided by the voltage divider resistor R1 and the thermistor RT1 is less than 0.7V, and the diode D1 conduction voltage drop is 0.7V, so there is no output at this time, that is, the current sampling pin of the driver chip U1 cannot detect the voltage input and does not enter the temperature protection state. When the ambient temperature is within 70°, the voltage divider resistor R1 and the thermistor RT1 output 1.0V, and the voltage given to the diode D1 is greater than 0.7V, and the output is 0.3V, so at this time the current sampling pin of the driver chip U1 detects the voltage input and enters the temperature protection state. Moreover, the higher the temperature, the greater the voltage divider output value of the voltage divider resistor R1 and the thermistor RT1, so the greater the depth of the temperature protection, that is, the smaller the output current of the driver chip U1.

[0072] In summary, the present invention discloses an LED drive over-temperature protection control method and circuit, which adjusts the output current of the driver chip by controlling the detection voltage of the current sampling pin of the driver chip, thereby realizing temperature control, and can make adjustments of different magnitudes according to different ambient temperatures, and has a good protection effect. The most basic voltage divider circuit is composed of a thermistor and a voltage divider resistor. A stable voltage is output by a voltage stabilizing module, and then the voltage is divided and transmitted to the current sampling pin of the driver chip through a diode. According to different ambient temperatures, the resistance value of the thermistor changes accordingly, thereby affecting the voltage division and changing the voltage output of the circuit. The circuit structure is simple and practical.

[0073] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for controlling over-temperature protection of LED driving, characterized in that: The steps include: S1. Designing circuit parameters of an over-temperature protection control circuit so that the over-temperature protection control circuit outputs different preset voltages at different ambient temperatures; S2, connecting the over-temperature protection control circuit to the current sampling pin of the driver chip of the LED driver circuit, and changing the output current of the driver chip by the preset voltage; Before step S1, the following steps are also included: S0, taking multiple voltage values ​​within the magnitude range of the peak voltage of the current sampling pin of the driving chip as the preset voltage; The step of changing the output current of the driver chip by using the preset voltage is specifically as follows: The peak voltage of the current sampling pin of the driver chip is changed by the preset voltage to change the output current of the driver chip, and the expression is as follows: Wherein, IOUT represents the output current of the driver chip, Vcspk represents the peak voltage of the current sampling pin of the driver chip, Rcs represents the resistance of the sampling resistor externally connected to the current sampling pin of the driver chip, Ton represents the turn-on time of the driver chip, Tdemag represents the demagnetization time of the driver chip, and T represents the switching cycle of the driver chip; The method of changing the peak voltage of the current sampling pin of the driver chip by the preset voltage to change the output current of the driver chip is specifically as follows: The preset voltage is injected into the current sampling pin of the driver chip, so that the voltage difference value originally collected on the current sampling pin of the driver chip is reduced, so that the peak voltage of the current sampling pin of the driver chip is reduced, resulting in a reduction in the output current of the driver chip.

2. An LED driver over-temperature protection control circuit, applied to an LED driver over-temperature protection control method according to claim 1, characterized in that: Including external power supply, voltage regulator module, thermistor, voltage divider resistor and diode; The output end of the external power supply is connected to the input end of the voltage stabilizing module, the output end of the voltage stabilizing module is connected to one end of the thermistor, the other end of the thermistor is simultaneously connected to the positive electrode of the diode and one end of the voltage divider resistor, the negative electrode of the diode is connected to the current sampling pin of the driving chip in the LED driving circuit, and the other end of the voltage divider resistor is grounded.

3. The LED driving over-temperature protection control circuit according to claim 2, characterized in that: The voltage stabilizing module includes a current limiting resistor and a voltage stabilizing diode; One end of the current limiting resistor is connected to the output end of the external power supply, the other end of the current limiting resistor is connected to both the cathode of the voltage zener diode and an end of the thermistor away from the voltage divider resistor, and the anode of the voltage zener diode is grounded.

4. The LED driving over-temperature protection control circuit according to claim 2, characterized in that: The over-temperature protection control circuit also includes a first filter capacitor; One end of the first filter capacitor is connected to the output end of the voltage stabilizing module and one end of the thermistor away from the voltage divider resistor, and the other end of the first filter capacitor is grounded.

5. The LED driving over-temperature protection control circuit according to claim 2, characterized in that: The over-temperature protection control circuit also includes a second filter capacitor; One end of the second filter capacitor is connected to the anode of the diode, and the other end of the second filter capacitor is grounded.

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