LED driving power supply and over-temperature protection circuit thereof

Abstract

The utility model relates to an LED driving power supply and an over-temperature protection circuit thereof. The LED driving power supply comprises a power module, a driving module, a temperature detection module, a voltage maintaining module and an over-temperature control module. The temperature detection module is connected with the over-temperature control module and the power module, the voltage maintaining module is connected with the temperature detection module, and the driving module is connected with the over-temperature control module and the power module. The temperature detection module detects temperature and power in real time and generates a temperature detection signal; the driving module outputs a driving signal to the power module according to the control signal output by the over-temperature control module so as to adjust the real-time power; the voltage holding module carries out voltage holding on the temperature detection module; and the over-temperature control module provides a control signal for the driving module and executes over-temperature protection control. According to the over-temperature protection circuit, the ambient temperature can be detected, over-temperature protection control can be carried out, false triggering is avoided, a temperature detection circuit does not need to be additionally arranged, and the circuit is simple in structure and easy to implement.

Description

Technical Field

[0001] This utility model relates to the technical field of LED driver power supplies, and more specifically, to an LED driver power supply and its over-temperature protection circuit. Background Technology

[0002] LED lighting fixtures have become mainstream lighting products and are widely used in various industries. As product maturity increases, market competition becomes increasingly fierce, which places higher demands on their cost-effectiveness. With power density increasing and cost decreasing, reliable operation is required, and overheat protection needs to be set to shut down the output when the set temperature is exceeded to prevent permanent damage to the power supply.

[0003] Currently, most LED driver power supplies on the market have certain shortcomings. On the one hand, most small and medium power LED driver power supplies do not have over-temperature protection functions, which can easily damage the power supply when exposed to high ambient temperatures. On the other hand, although some LED driver power supplies have over-temperature detection, the temperature detection circuit is complex, costly, and difficult to implement in situations where circuit board space is limited. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide an LED driver power supply and its over-temperature protection circuit, addressing the problems existing in the prior art.

[0005] The technical solution adopted by this utility model to solve its technical problem is: to construct an over-temperature protection circuit for an LED driver power supply, including: a power module, a driver module, a temperature detection module, a voltage holding module, and an over-temperature control module;

[0006] The temperature detection module is connected to the over-temperature control module and the power module, the voltage holding module is connected to the temperature detection module, and the drive module is connected to both the over-temperature control module and the power module.

[0007] The temperature detection module is used to detect temperature and power in real time and generate a temperature detection signal based on the ambient temperature and the real-time power of the power module.

[0008] The drive module is used to output a drive signal to the power module according to the control signal output by the over-temperature control module, so as to adjust the real-time power;

[0009] The voltage holding module is used to maintain the voltage of the temperature detection module;

[0010] The over-temperature control module is used to provide the control signal to the drive module and to perform over-temperature protection control based on the temperature detection signal.

[0011] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the temperature detection module includes: a temperature sensing circuit and a power detection circuit;

[0012] The temperature sensing circuit is connected to the voltage holding module and the power detection circuit respectively, and the connection node between the temperature sensing circuit and the power detection circuit is also connected to the over-temperature control module.

[0013] The power detection circuit is used to detect the power of the power module and generate a detection voltage based on the real-time power.

[0014] The temperature sensing circuit is used to detect the temperature in real time and form a voltage divider circuit with the power detection circuit to divide the detection voltage and the input voltage of the temperature sensing circuit to obtain the temperature detection signal.

[0015] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the temperature sensing circuit includes: a first diode, a first resistor, a second resistor, and a thermistor.

[0016] The anode of the first diode is connected to the input voltage, the cathode of the first diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor and the input end of the voltage holding module, the second end of the second resistor is connected to the first end of the thermistor, and the second end of the thermistor is connected to the detection end of the over-temperature control module and the output end of the power detection circuit.

[0017] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the power detection circuit includes: a fifth resistor and a power detection resistor;

[0018] The first end of the fifth resistor is connected to the detection end of the over-temperature control module and the second end of the thermistor. The second end of the fifth resistor is connected to the first end of the power detection resistor. The first end of the power detection resistor is also connected to the power module. The second end of the power detection resistor is grounded.

[0019] The first end of the fifth resistor is the output end of the power detection circuit.

[0020] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the voltage holding module includes: a clamping circuit;

[0021] The input terminal of the clamping circuit is connected to the temperature sensing circuit, and the output terminal of the clamping circuit is grounded.

[0022] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the clamping circuit includes: a first Zener diode;

[0023] The cathode of the first Zener diode is connected to the second end of the first resistor and the first end of the second resistor, and the anode of the first Zener diode is grounded.

[0024] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the thermistor is a negative temperature coefficient thermistor.

[0025] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the over-temperature control module includes: an over-temperature control chip;

[0026] The detection pin of the over-temperature control chip is connected to the second end of the thermistor and the first end of the fifth resistor, and the drive pin of the over-temperature control chip is connected to the input end of the drive module.

[0027] In the over-temperature protection circuit of the LED driver power supply described in this utility model, the driving module includes: a third resistor, a fourth resistor, and a second diode; the power module includes: a first capacitor, a transformer output winding, and a power transistor.

[0028] The first end of the third resistor and the first end of the fourth resistor are connected to the drive pin of the over-temperature control chip. The second end of the third resistor is connected to the first end of the power transistor. The second end of the power transistor is connected to the first end of the power detection resistor. The third end of the power transistor is connected to the output terminal of the transformer output winding. The second end of the fourth resistor is connected to the cathode of the second diode. The anode of the second diode is connected to the first end of the power transistor. The input terminal of the transformer output winding is connected to a high level and the first end of the first capacitor. The second end of the first capacitor is grounded.

[0029] This utility model also provides an LED driver power supply, including: the over-temperature protection circuit of the LED driver power supply described above.

[0030] The LED driver power supply and its over-temperature protection circuit of this utility model have the following beneficial effects: It includes a power module, a driver module, a temperature detection module, a voltage holding module, and an over-temperature control module; the temperature detection module is connected to the over-temperature control module and the power module, the voltage holding module is connected to the temperature detection module, and the driver module is connected to both the over-temperature control module and the power module; the temperature detection module detects the temperature and power in real time and generates a temperature detection signal; the driver module outputs a drive signal to the power module to adjust the real-time power according to the control signal output by the over-temperature control module; the voltage holding module holds the voltage of the temperature detection module; and the over-temperature control module provides a control signal to the driver module and executes over-temperature protection control. This utility model can detect the ambient temperature and perform over-temperature protection control without false triggering, does not require additional temperature detection circuitry, and has a simple and easy-to-implement circuit structure. Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0032] Figure 1 This is a schematic diagram of the over-temperature protection circuit for the LED driver power supply provided by this utility model.

[0033] Figure 2 This is a circuit diagram of the over-temperature protection circuit for the LED driver power supply provided by this utility model. Detailed Implementation

[0034] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0035] refer to Figure 1 , Figure 1 The schematic diagram of the over-temperature protection circuit for the LED driver power supply provided by this utility model.

[0036] Specifically, such as Figure 1As shown, the over-temperature protection circuit of the LED driver power supply includes: a power module 15, a driver module 14, a temperature detection module 11, a voltage holding module 12, and an over-temperature control module 13. The temperature detection module 11 is connected to the over-temperature control module 13 and the power module 15; the voltage holding module 12 is connected to the temperature detection module 11; and the driver module 14 is connected to both the over-temperature control module 13 and the power module 15. The temperature detection module 11 is used to detect temperature and power in real time and generate a temperature detection signal based on the ambient temperature and the real-time power of the power module 15. The driver module 14 is used to output a drive signal to the power module 15 according to the control signal output by the over-temperature control module 13 to adjust the real-time power. The voltage holding module 12 is used to hold the voltage of the temperature detection module 11. The over-temperature control module 13 is used to provide a control signal to the driver module 14 and to perform over-temperature protection control according to the temperature detection signal.

[0037] In this embodiment of the present invention, the voltage holding module 12 holds the voltage of the temperature detection module 11, so that the temperature detection module 11 is not affected by the output voltage. That is, when the output voltage changes, the voltage of the over-temperature detection module remains unchanged, so that the over-temperature detection module always detects within the specified detection range, effectively avoiding false triggering that leads to over-temperature protection, and accurately realizing over-temperature detection and over-temperature protection.

[0038] Optionally, in this embodiment of the present invention, the temperature detection module 11 includes a temperature sensing circuit and a power detection circuit.

[0039] The temperature sensing circuit is connected to the voltage holding module 12 and the power detection circuit respectively, and the connection node between the temperature sensing circuit and the power detection circuit is also connected to the over-temperature control module 13. The power detection circuit is used to detect the power of the power module 15 and generate a detection voltage based on the real-time power. The temperature sensing circuit is used to detect the temperature in real time and form a voltage divider circuit with the power detection circuit to divide the detection voltage and the input voltage of the temperature sensing circuit to obtain a temperature detection signal.

[0040] Optionally, in this embodiment of the present invention, the voltage holding module 12 includes: a clamping circuit; the input terminal of the clamping circuit is connected to the temperature sensing circuit, and the output terminal of the clamping circuit is grounded.

[0041] Specifically, such as Figure 2 As shown, in a preferred embodiment, the temperature sensing circuit includes: a first diode D1, a first resistor R1, a second resistor R2, and a thermistor RT1.

[0042] In this circuit, the anode of the first diode D1 is connected to the input voltage, the cathode of the first diode D1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the first end of the second resistor R2 and the input end of the voltage holding module 12, the second end of the second resistor R2 is connected to the first end of the thermistor RT1, and the second end of the thermistor RT1 is connected to the detection end of the over-temperature control module 13 and the output end of the power detection circuit.

[0043] In this embodiment, the power detection circuit includes: a fifth resistor R5 and a power detection resistor RS1.

[0044] Among them, the first end of the fifth resistor R5 is connected to the detection end of the over-temperature control module 13 and the second end of the thermistor RT1. The second end of the fifth resistor R5 is connected to the first end of the power detection resistor RS1. The first end of the power detection resistor RS1 is also connected to the power module 15. The second end of the power detection resistor RS1 is grounded. The first end of the fifth resistor R5 is the output end of the power detection circuit.

[0045] In this embodiment, the clamping circuit includes a first Zener diode ZD1.

[0046] The cathode of the first Zener diode ZD1 is connected to the second end of the first resistor R1 and the first end of the second resistor R2, and the anode of the first Zener diode ZD1 is grounded.

[0047] Optionally, in this embodiment of the invention, the thermistor RT1 is a thermistor with a negative temperature coefficient.

[0048] In this embodiment, the over-temperature control module 13 includes an over-temperature control chip U1; the detection pin of the over-temperature control chip U1 is connected to the second end of the thermistor RT1 and the first end of the fifth resistor R5, and the drive pin of the over-temperature control chip U1 is connected to the input end of the drive module 14.

[0049] In this embodiment, the driving module 14 includes a third resistor R3, a fourth resistor R4, and a second diode D2; the power module 15 includes a first capacitor C1, a transformer output winding T1-B, and a power transistor Q1; the first ends of the third resistor R3 and the fourth resistor R4 are connected to the driving pin of the over-temperature control chip U1, the second end of the third resistor R3 is connected to the first end of the power transistor Q1, the second end of the power transistor Q1 is connected to the first end of the power detection resistor RS1, the third end of the power transistor Q1 is connected to the output end of the transformer output winding T1-B, the second end of the fourth resistor R4 is connected to the cathode of the second diode D2, the anode of the second diode D2 is connected to the first end of the power transistor Q1, the input end of the transformer output winding T1-B is connected to a high level (i.e., HV, where HV is the voltage output by the PFC module (i.e., power factor correction module) in the LED driver power supply) and the first end of the first capacitor C1, and the second end of the first capacitor C1 is grounded.

[0050] like Figure 2 As shown, the first capacitor C1 is a high-frequency filter capacitor, the transformer T1 is a flyback power transformer, which is a conventional flyback transformer used in LED driver power supplies, the power transistor Q1 is a MOSFET, and the over-temperature control chip U1 is a quasi-resonant control chip in the LED driver power supply (a conventional quasi-resonant control chip used in LED driver power supplies can be used). The over-temperature control chip U1 outputs a control signal (this control signal is a PWM signal) to the gate of the power transistor Q1 through its drive pin, realizing the periodic drive control of the power transistor Q1. That is, the over-temperature control chip U1 controls the switching state of the power transistor Q1 cycle by cycle, thereby achieving the purpose of adjusting the output power of the power module 15. Figure 2 As shown, the fifth resistor R5 and the second capacitor C2 can also form an RC filter to eliminate high-frequency interference and prevent IC malfunction. The third capacitor C3 is the power supply capacitor for the over-temperature control chip U1. The first winding T1-A of the transformer, together with the sixth resistor R6 and the seventh resistor R7, forms a demagnetizing circuit to bring the transformer's magnetic flux to zero during operation and prevent magnetic saturation.

[0051] like Figure 2 As shown, the first diode D1, the first resistor R1, the second resistor R2, the thermistor RT1, the fifth resistor R5, and the power detection resistor RS1 constitute the over-temperature detection module. Since the thermistor RT1 is a negative temperature coefficient thermistor, its resistance can decrease as the temperature increases, that is, the higher the temperature, the smaller its resistance value.

[0052] like Figure 2As shown, since the first winding T1-A of the transformer is in phase with the output winding T1-B, the voltage at point Va is positively correlated with the voltage of the LED applied to the output terminal. Within the constant current range, when the LED voltage increases, the voltage coupled to the winding of T1-A also increases; when the LED voltage decreases, the voltage coupled to the winding of T1-A also decreases. Since the threshold voltage of the detection pin (CS pin) of the temperature control chip is fixed, when the LED voltage at the output terminal increases, the voltage at point Va also increases. Because the resistance values ​​of the first resistor R1, the second resistor R2, the fifth resistor R5, and the power detection resistor RS1 are all fixed, the voltage at point Vb is even higher. This causes the voltage at point Vb of the thermistor RT1 to reach the threshold voltage of the CS pin at lower temperatures (below 100 degrees Celsius), thus affecting the use of the product. When the output LED voltage decreases, the voltage at point Va also decreases. Since the resistance values ​​of the first resistor R1, the second resistor R2, the fifth resistor R5, and the power detection resistor RS1 are all fixed, the voltage at point Vb is even lower. This means that the thermistor RT1 only reaches the threshold voltage of the CS pin at higher temperatures (above 100 degrees Celsius), thus affecting product reliability. Therefore, to solve this problem, the voltage at point Va should be kept constant when the output LED voltage changes. Since the voltage of the T1-A winding cannot be directly clamped (as this would affect demagnetization detection), this invention adds a first Zener diode ZD1 at point Vc. The first Zener diode ZD1 clamps the voltage at point Vc, making it unaffected by the output voltage. When the output LED voltage changes, the voltage at point Vc remains constant. This ensures that when the thermistor RT1 detects the temperature, the voltage at point Vb always reaches the threshold voltage of the CS pin at around 100 degrees Celsius before triggering over-temperature protection, effectively preventing false triggering.

[0053] Among them, the voltage at the first end of the power detection resistor RS1 is the detection voltage generated by the power detection circuit, and the input voltage of the temperature sensing circuit is the voltage at point Va.

[0054] It should be noted that since the over-temperature control chip U1 controls the switching state of the power transistor Q1 cycle by cycle using a PWM signal, when the power transistor Q1 is on, the current through the transformer output winding T1-B is converted into a detection voltage on the CS pin via the power detection resistor RS1. Because the transformer input voltage and the power detection resistor RS1 are constant, the voltage on the CS pin of the over-temperature control chip U1 will not change with temperature. When the power transistor Q1 is off, the voltage at point Vc is divided by the second resistor R2, the thermistor RT1, the fifth resistor R5, and the power detection resistor RS1, and then sent to the CS pin as the over-temperature detection signal. As the temperature rises, the resistance of the thermistor RT1 decreases. When the Vc voltage remains constant, the voltage at point Vb rises. When the temperature reaches a preset value, the voltage at point Vb rises to the threshold voltage of the CS pin, triggering the over-temperature control chip U1 to perform over-temperature protection and stop working. That is, over-temperature protection control is performed in each cycle when the power transistor Q1 is off.

[0055] This utility model also provides an LED driver power supply, wherein the LED driver power supply includes: the over-temperature protection circuit of the LED driver power supply disclosed in the embodiments of this utility model.

[0056] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They do not limit the scope of protection of this utility model. All equivalent changes and modifications made within the scope of the claims of this utility model should fall within the scope of the claims of this utility model.

Claims

1. An over-temperature protection circuit for an LED driver power supply, characterized in that, include: Power module, drive module, temperature detection module, voltage holding module, and over-temperature control module; The temperature detection module is connected to the over-temperature control module and the power module, the voltage holding module is connected to the temperature detection module, and the drive module is connected to both the over-temperature control module and the power module. The temperature detection module is used to detect temperature and power in real time and generate a temperature detection signal based on the ambient temperature and the real-time power of the power module. The drive module is used to output a drive signal to the power module according to the control signal output by the over-temperature control module, so as to adjust the real-time power; The voltage holding module is used to maintain the voltage of the temperature detection module; The over-temperature control module is used to provide the control signal to the drive module and to perform over-temperature protection control based on the temperature detection signal.

2. The over-temperature protection circuit for the LED driver power supply according to claim 1, characterized in that, The temperature detection module includes: a temperature sensing circuit and a power detection circuit; The temperature sensing circuit is connected to the voltage holding module and the power detection circuit respectively, and the connection node between the temperature sensing circuit and the power detection circuit is also connected to the over-temperature control module. The power detection circuit is used to detect the power of the power module and generate a detection voltage based on the real-time power. The temperature sensing circuit is used to detect the temperature in real time and form a voltage divider circuit with the power detection circuit to divide the detection voltage and the input voltage of the temperature sensing circuit to obtain the temperature detection signal.

3. The over-temperature protection circuit for the LED driver power supply according to claim 2, characterized in that, The temperature sensing circuit includes: a first diode, a first resistor, a second resistor, and a thermistor; The anode of the first diode is connected to the input voltage, the cathode of the first diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor and the input end of the voltage holding module, the second end of the second resistor is connected to the first end of the thermistor, and the second end of the thermistor is connected to the detection end of the over-temperature control module and the output end of the power detection circuit.

4. The over-temperature protection circuit for the LED driver power supply according to claim 3, characterized in that, The power detection circuit includes: a fifth resistor and a power detection resistor; The first end of the fifth resistor is connected to the detection end of the over-temperature control module and the second end of the thermistor. The second end of the fifth resistor is connected to the first end of the power detection resistor. The first end of the power detection resistor is also connected to the power module. The second end of the power detection resistor is grounded. The first end of the fifth resistor is the output end of the power detection circuit.

5. The over-temperature protection circuit for the LED driver power supply according to claim 3, characterized in that, The voltage holding module includes: a clamping circuit; The input terminal of the clamping circuit is connected to the temperature sensing circuit, and the output terminal of the clamping circuit is grounded.

6. The over-temperature protection circuit for the LED driver power supply according to claim 5, characterized in that, The clamping circuit includes: a first Zener diode; The cathode of the first Zener diode is connected to the second end of the first resistor and the first end of the second resistor, and the anode of the first Zener diode is grounded.

7. The over-temperature protection circuit for the LED driver power supply according to claim 3, characterized in that, The thermistor is a negative temperature coefficient thermistor.

8. The over-temperature protection circuit for the LED driver power supply according to claim 4, characterized in that, The over-temperature control module includes: an over-temperature control chip; The detection pin of the over-temperature control chip is connected to the second end of the thermistor and the first end of the fifth resistor, and the drive pin of the over-temperature control chip is connected to the input end of the drive module.

9. The over-temperature protection circuit for the LED driver power supply according to claim 8, characterized in that, The drive module includes: a third resistor, a fourth resistor, and a second diode; the power module includes: a first capacitor, a transformer output winding, and a power transistor. The first end of the third resistor and the first end of the fourth resistor are connected to the drive pin of the over-temperature control chip. The second end of the third resistor is connected to the first end of the power transistor. The second end of the power transistor is connected to the first end of the power detection resistor. The third end of the power transistor is connected to the output terminal of the transformer output winding. The second end of the fourth resistor is connected to the cathode of the second diode. The anode of the second diode is connected to the first end of the power transistor. The input terminal of the transformer output winding is connected to a high level and the first end of the first capacitor. The second end of the first capacitor is grounded.

10. An LED driver power supply, characterized in that, include: The over-temperature protection circuit for the LED driver power supply according to any one of claims 1-9.

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