Power supply with over-temperature derating protection function

Abstract

A power supply with an over-temperature derating protection function comprises a first rectification filter circuit, a power factor correction circuit, a power conversion circuit, a second rectification filter circuit, a power factor correction control circuit and a protection circuit. The temperature detection element of the protection circuit is configured to detect an operation temperature of the power supply. When the temperature detection element detects that the operating temperature of the power supply exceeds a predetermined temperature, the switch element is started to reduce the output voltage. The operating temperature of the power supply is reduced by adjusting the voltage in advance to reduce the output power, so that a protection function of stopping power supply due to over-temperature can be prevented from being triggered, the power supply can continuously supply power, and the overall circuit efficiency is effectively improved.

Description

Technical Field

[0001] The utility model relates to a power supply, in particular to a power supply with an over-temperature derating protection function. Background Art

[0002] The power supply may include a power factor correction circuit, a power conversion circuit, a protection circuit, and a control circuit. For example, when the temperature of the power supply is too high, the over temperature protection (OTP) function of the protection circuit will set the power supply to stop supplying power. However, although this over temperature protection mechanism ensures safety, it may bring many problems in certain application areas. For example, when the power supply is supplying power to a light emitting diode, this over temperature protection mechanism may cause the light emitting diode to be unable to provide lighting functions stably or cause problems such as light flickering.

[0003] Therefore, in order to overcome the shortcomings and deficiencies in the prior art, it is necessary to provide an improved power supply with an over-temperature protection function to solve the problems existing in the conventional technology. Utility Model Content

[0004] The main purpose of the utility model is to provide a power supply which can overcome the problem that the existing over-temperature protection circuit will cause the power supply to stop supplying power and cannot continuously supply power to the load.

[0005] To achieve the above-mentioned purpose, the utility model provides a power supply, which includes a first rectifier and filter circuit, a power factor correction circuit, a power conversion circuit, a second rectifier and filter circuit and a protection circuit; the first rectifier and filter circuit is configured to rectify and filter the AC voltage to generate a rectified voltage; the output end of the first rectifier and filter circuit is coupled to the input end of the power factor correction circuit, and the power factor correction circuit is configured to perform power factor correction on the rectified voltage to output a corrected voltage; the input end of the power conversion circuit is coupled to the output end of the power factor correction circuit, and the power conversion circuit is configured to adjust the corrected voltage to a conversion voltage; the input end of the second rectifier and filter circuit is coupled to the output end of the power conversion circuit, and the second rectifier and filter circuit is configured to rectify the conversion voltage to generate an output rectified voltage. voltage to supply power to a load; the protection circuit includes a control circuit, an impedance element and a switch element, the impedance element is coupled between a feedback pin of the control circuit and an output voltage; the temperature detection element is configured to detect an operating temperature of the power supply; the switch element includes a control end, the control end is coupled to the temperature detection element, and the switch element is connected in parallel with a resistor of the impedance element, wherein when the operating temperature of the power supply is higher than a predetermined temperature, a resistance value corresponding to the temperature detection element changes, so that a control voltage of the control end of the switch is greater than or equal to a set voltage to turn on the switch element, the resistor is short-circuited, so that the resistance value of the impedance element becomes smaller, and the control circuit sets at least one of the power factor correction circuit and the power conversion circuit to reduce the output rectified voltage due to an increase in a pin voltage value of the feedback pin.

[0006] In one embodiment of the present invention, the temperature detection element further includes a thermistor, a first resistor and a second resistor. The thermistor is connected in parallel with the first resistor, and the second resistor is coupled between the thermistor and the first filter element. When the thermistor detects that the operating temperature of the power supply is higher than the predetermined temperature, the resistance value of the thermistor decreases, so that the voltage of the first node rises to the set voltage.

[0007] In an embodiment of the present invention, the thermistor is disposed adjacent to at least one power transistor of the power supply and is used to detect the operating temperature of the power supply.

[0008] In an embodiment of the present invention, the impedance element comprises a plurality of voltage-dividing resistors connected in series, the impedance element is coupled between the output voltage and the feedback pin of the control circuit, and the switch element is connected in parallel to at least one of the voltage-dividing resistors.

[0009] In an embodiment of the present invention, the protection circuit is configured to stop supplying power to the load when the operating temperature of the power supply exceeds an over-temperature, wherein the predetermined temperature is lower than the over-temperature.

[0010] In an embodiment of the present invention, the output voltage is configured to be coupled to at least one of the output ends of the first rectifying and filtering circuit, the power factor correction circuit, the power conversion circuit, and the second rectifying and filtering circuit.

[0011] As described above, when the power supply is placed in an area where heat is not easily dissipated, such as a wooden platform, before the temperature at which the power supply to the load is stopped is reached, the operating temperature of the power supply is detected by the temperature detection element, and the switch element is activated to reduce the output voltage when the temperature exceeds the predetermined temperature. By pre-adjusting the voltage and reducing the output power to reduce the operating temperature of the power supply, the protection function of stopping power supply due to over-temperature can be avoided, so that the power supply can continue to supply power and effectively improve the overall circuit performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a power supply according to an embodiment of the utility model;

[0013] Figure 2 yes Figure 1 Schematic diagram of part of the power supply circuit.

[0014]

Explanation of symbols

[0015] 100: Power supply

[0016] 2: The first rectifier filter circuit

[0017] 3: Power factor correction circuit

[0018] 4: Power conversion circuit

[0019] 41: Pulse Width Modulation Converter

[0020] 42: Pulse Width Modulation Controller

[0021] 43: Transformer

[0022] 5: Second rectifier filter circuit

[0023] 6: Power factor correction control circuit

[0024] 7: Protection circuit

[0025] 71: Feedback unit

[0026] 711: Impedance element

[0027] 712: Second filter element

[0028] 72: Temperature detection element

[0029] 73: First filter element

[0030] 74: Switching element

[0031] 8: Control circuit

[0032] 9: Feedback controller

[0033] Rd1, Rd2, Rd3, Rd4, Rd5: voltage divider resistors

[0034] R1: The first resistor

[0035] R2: Second resistor

[0036] Rt: Thermistor

[0037] P1: Feedback pin

[0038] P2: Power pin

[0039] Vcc: supply voltage

[0040] Vo: Output voltage

[0041] Vin: Power supply

[0042] Vout: output rectified voltage

[0043] Vrec: rectified voltage

[0044] Vpfc: Correction voltage

[0045] Vcon: conversion voltage DETAILED DESCRIPTION

[0046] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following will specifically cite the preferred embodiments of the present invention and provide a detailed description in conjunction with the attached drawings. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, surrounding, center, horizontal, lateral, vertical, longitudinal, axial, radial, topmost or bottommost, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and understand the present invention, but not to limit the present invention.

[0047] Please refer to Figure 1The power supply 100 can be used to drive the light emitting diode LED according to the power supply Vin. In this embodiment, the power supply Vin is an AC power supply, and the power supply 100 includes a first rectifier filter circuit 2, a power factor correction circuit 3, a power conversion circuit 4, a second rectifier filter circuit 5, a power factor correction control circuit 6, a protection circuit 7, and a control circuit 8 (see Figure 2 ) and a feedback controller 9. In other embodiments, the above circuit function blocks can be implemented in an integrated or split manner according to different design considerations, and the power supply 100 can also reduce some of the above circuits or add additional circuits according to different design considerations. For example, the power factor correction control circuit 6 and the pulse width modulation controller 42 of the power conversion circuit 4 can be implemented by the same circuit or microcontroller.

[0048] The first rectifier and filter circuit 2 is configured to rectify and filter the input AC voltage to generate a rectified voltage Vrec, wherein the output end of the first rectifier and filter circuit 2 is coupled to the input end of the power factor correction circuit 3, and the power factor correction control circuit 6 is used to set the power factor correction circuit 3 to perform power factor correction on the rectified voltage Vrec to output a correction voltage Vpfc.

[0049] The input end of the power conversion circuit 4 is coupled to the output end of the power factor correction circuit 3, and the power conversion circuit 4 is configured to adjust the correction voltage Vpfc to the conversion voltage Vcon. In the present embodiment, the power conversion circuit 4 has a pulse width modulation converter 41, a pulse width modulation controller 42 and a transformer 43. The input end of the pulse width modulation converter 41 is coupled to the output end of the power factor correction circuit 3 to receive the correction voltage Vpfc. The amplitude modulation controller 42 is coupled to the pulse width modulation converter 41, and the amplitude modulation controller 42 can generate a pulse width modulation control signal to control the power switch and other components inside the pulse width modulation converter 41. The primary side of the transformer 43 is coupled to the pulse width modulation converter 41, and the secondary side of the transformer 43 is coupled to the input end of the second rectifier filter circuit 5 on the secondary side to provide the conversion voltage Vcon. In other embodiments, the power conversion circuit 4 can also adopt other suitable power conversion architectures, such as a boost conversion circuit and a buck conversion circuit.

[0050] The input end of the second rectifying and filtering circuit 5 is coupled to the output end of the transformer 43 of the power conversion circuit 4, and the second rectifying and filtering circuit 5 is configured to rectify the conversion voltage Vcon to generate an output rectified voltage Vout to provide to a load (such as a light emitting diode LED in this embodiment).

[0051] In this embodiment, the protection circuit 7 of the power supply 100 is coupled to the pulse width modulation controller 42, and the protection circuit 7 can provide at least one of the functions of over-voltage protection, over-current protection and over-temperature protection. In other embodiments, the protection circuit 7 can also be configured to be coupled to at least one of the power factor correction control circuit 6 and the pulse width modulation controller 42 to provide at least one of the functions of over-voltage protection, over-current protection and over-temperature protection.

[0052] Please refer to Figure 1 and Figure 2 , Figure 2 FIG. 1 is a schematic diagram of an embodiment of a partial circuit of the protection circuit 7. Figure 2 In the embodiment of the present invention, this part of the circuit mainly provides the over-temperature derating function. The control circuit 8 has a feedback pin P1 and a power pin P2, wherein the power pin P2 is coupled to a power supply voltage Vcc. The control circuit 8 can be arranged in the protection circuit 7, or can be integrated in the power factor correction control circuit 6 and / or the pulse width modulation controller 42.

[0053] The protection circuit 7 includes a feedback unit 71, a temperature detection element 72, a first filter element 73 and a switch element 74. In the present embodiment, a first end of the temperature detection element 72 is coupled to the supply voltage Vcc, a second end of the temperature detection element 72 is coupled to the control end of the switch element 74, and the temperature detection element 72 is configured to detect an operating temperature of the power supply 100. For example, the temperature detection element 72 can be disposed near a power switch of the power supply 100 or other elements that are prone to high temperature.

[0054] In the present embodiment, the feedback unit 71 has an impedance element 711 and a second filter element 712. The impedance element 711 is coupled between the feedback pin P1 of the control circuit 8 and an output voltage Vo. The impedance element 711 has a plurality of voltage-dividing resistors Rd1, Rd2, Rd3, Rd4, and Rd5 connected in series. The impedance element 711 is coupled between the output voltage Vo and the feedback pin P1 of the control circuit 8. The second filter element 712 is coupled between a ground potential and the feedback pin P1 of the control circuit 8. The switch element 74 is connected in parallel to one of the voltage-dividing resistors Rd1 of the impedance element 711. The second filter element 712 has a resistor and a capacitor connected in parallel to filter noise. In the present embodiment, the voltage-dividing resistor Rd1 of the impedance element 711, the resistor and the capacitor of the second filter element 712 are coupled to the feedback pin P1 of the control circuit 8. Figure 2The output voltage Vo can be set to be coupled to at least one of the output ends of the first rectifier and filter circuit 2, the power factor correction circuit 3, the power conversion circuit 4 and the second rectifier and filter circuit 5, so as to reference at least one of the rectified voltage Vrec, the correction voltage Vpfc, the conversion voltage Vcon and the output rectified voltage Vout. For example, the output voltage Vo can be set to the voltage or the divided voltage of the output rectified voltage Vout.

[0055] The temperature detection element 72 is coupled between the control terminal of the switch element 74 and the power supply voltage Vcc. The temperature detection element 72 has a thermistor Rt, a first resistor R1 and a second resistor R2. The thermistor Rt is connected in parallel with the first resistor R1 and is configured to detect the operating temperature of the power supply 100. The first end of the thermistor Rt is coupled to the power supply voltage Vcc, and the second end of the thermistor Rt is coupled to the second resistor R2. The second resistor R2 is coupled between the thermistor Rt and the control terminal of the switch element 74. In this embodiment, the thermistor Rt of the temperature detection element 72 changes its resistance value with the operating temperature of the power supply 100. For example, when the thermistor Rt is implemented with a negative temperature coefficient element, when the operating temperature of the power supply 100 is higher than a predetermined temperature, the resistance value of the thermistor Rt decreases, causing a voltage at the control end of the switch element 74 to rise to a value greater than or equal to a set voltage, thereby turning on the switch element 74. At this time, the resistance values ​​of the switch element 74 and the voltage-dividing resistor Rd1 connected in parallel decrease, causing the resistance value of the impedance element 711 to decrease, thereby increasing the voltage of the feedback pin P1 of the control circuit 8 divided by the output voltage Vo. When the voltage of the feedback pin P1 of the control circuit 8 increases, the control circuit 8 will correspondingly set the pulse width modulation controller 42 and / or the power factor correction control circuit 6 to reduce the correction voltage Vpfc and / or the conversion voltage Vcon to reduce the output rectified voltage Vout. Therefore, the output rectified voltage Vout output to the load decreases, and the operating temperature of the power supply 100 can be correspondingly reduced, maintained, or heated at a slower rate, but power can still be supplied to enable the load to operate.

[0056] In this embodiment, the thermistor Rt is disposed on one side of at least one power transistor of the power supply 100 to detect the operating temperature of the power transistor. When the thermistor Rt detects that the operating temperature of the power supply 100 is higher than a predetermined temperature, the resistance value of the thermistor Rt decreases, causing the control end of the switch element 74 to rise to a voltage greater than or equal to a set voltage to turn on the switch element 74.

[0057] In one embodiment, Figure 1The protection circuit 7 can also provide an over-temperature protection function to stop power supply, that is, when the operating temperature of the power supply 100 exceeds an over-temperature temperature, the power supply to the load is suspended, wherein the predetermined temperature is lower than the over-temperature temperature. When the operating temperature of the power supply 100 reaches the predetermined temperature, the protection circuit 7 first activates the over-temperature derating function to reduce the output rectified voltage Vout, and correspondingly reduces the power supplied to the load, so that the load can still operate. If the operating temperature of the power supply 100 still rises to the over-temperature temperature after using the over-temperature derating function, the protection circuit 7 sets the power supply 100 to suspend the power supply to the load, so as to avoid danger caused by over-temperature.

[0058] The switch element 74 can be connected in parallel to one or more of the voltage-dividing resistors Rd1, Rd2, Rd3, Rd4, and Rd5 of the impedance element 711. In the present embodiment, the switch element 74 is an N-channel enhanced metal oxide semiconductor field effect transistor (MOSFET), the control terminal of the switch element 74 is a gate, and the switch element 74 also has a source and a drain, which are respectively coupled to the two ends of the voltage-dividing resistor Rd1. When the control terminal of the switch element 74 is greater than or equal to a set voltage, the switch element 74 is in a conducting state, and when the control terminal of the switch element 74 is less than the set voltage, the switch element 74 is in a non-conducting state.

[0059] According to the above structure, a switch element 74 is connected in parallel next to the voltage-dividing resistor Rd1, and a thermistor Rt for detecting temperature is set at the same time. When the temperature of the thermistor Rt rises, the resistance value of the two ends of the first resistor R1 decreases, and then the voltage of the control end of the switch element 74 begins to rise. When the temperature of the thermistor Rt reaches a predetermined temperature, the voltage of the control end of the switch element 74 is greater than or equal to the set voltage, and the switch element 74 is turned on, which is equivalent to short-circuiting the voltage-dividing resistor Rd1. The resistance value of the impedance element 711 of the feedback unit 71 is reduced, thereby increasing the pin voltage of the feedback pin P1 of the control circuit 8. The control circuit 8 will correspondingly set the pulse width modulation controller 42 and / or the power factor correction control circuit 6 to reduce the output voltage Vo, so that the output power can be reduced and the power supply 100 can continue to supply power to the load.

[0060] As described above, when the power supply 100 is placed in an area where heat is not easily dissipated, such as a wooden platform, the power transistor of the power supply 100 detects the operating temperature of the power supply 100 through the temperature detection element 72 before reaching the over-temperature temperature. When the temperature exceeds the predetermined temperature, the switch element 74 is activated to reduce the output rectified voltage Vout supplied to the load. By reducing the output power to reduce, maintain or slow down the increase in the operating temperature of the power supply 100, the protection function of stopping power supply due to over-temperature is avoided to be triggered, so that the power supply 100 can continue to supply power and effectively improve the overall circuit performance.

[0061] Although the present invention has been disclosed in terms of preferred embodiments, this is not intended to limit the present invention. Anyone familiar with the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the attached claims.

Claims

1. A power supply with over-temperature derating protection function, characterized in that: Include: a first rectifying and filtering circuit configured to rectify and filter the AC voltage to generate a rectified voltage; a power factor correction circuit, wherein the output end of the first rectifier and filter circuit is coupled to the input end of the power factor correction circuit, and the power factor correction circuit is configured to perform power factor correction on the rectified voltage to output a correction voltage; a power conversion circuit, wherein an input terminal of the power conversion circuit is coupled to an output terminal of the power factor correction circuit, and the power conversion circuit is configured to adjust the correction voltage to a conversion voltage; a second rectifying and filtering circuit, wherein an input terminal of the second rectifying and filtering circuit is coupled to an output terminal of the power conversion circuit, and the second rectifying and filtering circuit is configured to rectify the conversion voltage to generate an output rectified voltage to supply power to a load; A protection circuit comprising: a control circuit; An impedance element coupled between a feedback pin of the control circuit and an output voltage; a temperature detection element configured to detect an operating temperature of the power supply; and A switch element comprises a control terminal, the control terminal is coupled to the temperature detection element, and the switch element is connected in parallel with a resistor of the impedance element; When the operating temperature of the power supply is higher than a predetermined temperature, a resistance value of the corresponding temperature detection element changes, so that a control voltage of the control end of the switch element is greater than or equal to a set voltage, so that the switch element is turned on, the resistor is short-circuited, and the resistance value of the impedance element becomes smaller. The control circuit sets at least one of the power factor correction circuit and the power conversion circuit to reduce the output rectified voltage due to an increase in a pin voltage value of the feedback pin.

2. The power supply with over-temperature derating protection function according to claim 1, characterized in that: The temperature detection element further includes a thermistor, a first resistor and a second resistor. The thermistor is connected in parallel with the first resistor, and the second resistor is coupled between the thermistor and the control end of the switch element. When the thermistor detects that the operating temperature of the power supply is higher than the predetermined temperature, the resistance value of the thermistor decreases, so that the control voltage of the control end of the switch element rises to the set voltage.

3. The power supply with over-temperature derating protection function according to claim 2, characterized in that: The thermistor is disposed adjacent to at least one power transistor of the power supply and is used for detecting the operating temperature of the power supply.

4. The power supply with over-temperature derating protection function according to claim 1, characterized in that: The impedance element includes a plurality of voltage-dividing resistors connected in series. The impedance element is coupled between the output voltage and the feedback pin of the control circuit. The switch element is connected in parallel to at least one of the plurality of voltage-dividing resistors.

5. The power supply with over-temperature derating protection function according to claim 1, characterized in that: The protection circuit is configured to stop supplying power to the load when the operating temperature of the power supply exceeds an over-temperature, wherein the predetermined temperature is lower than the over-temperature.

6. The power supply with over-temperature derating protection function according to claim 1, characterized in that: The output voltage is configured to be coupled to at least one of the output ends of the first rectifying and filtering circuit, the power factor correction circuit, the power conversion circuit, and the second rectifying and filtering circuit.

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