A control circuit with line voltage drop compensation and over-temperature protection

Abstract

The utility model embodiment discloses a control circuit with line voltage drop compensation and over-temperature protection, comprising a rectifier filter module, a transformer, a synchronous rectifier module, a protocol control module, a PWM control module, a power supply module and an optocoupler feedback voltage-dividing sampling module, wherein the input end of the rectifier filter module is connected to the mains, the output end of the rectifier filter module is connected to the opposite-name end of the primary winding of the transformer, the same-name end of the primary winding of the transformer is connected to the power supply module after passing through the PWM control module, the first secondary winding of the transformer is connected to the output interface, the same-name end of the first secondary winding of the transformer is connected to the optocoupler feedback voltage-dividing sampling module and the protocol control module, the first secondary winding of the transformer is connected to the opposite-name end of the synchronous rectifier module and the protocol control module, the protocol control module is connected to the synchronous rectifier module, the output interface and the optocoupler feedback voltage-dividing sampling module, and the optocoupler feedback voltage-dividing sampling module is connected to the power supply module through the PWM control module.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, and in particular to a control circuit with line voltage drop compensation and over-temperature protection. Background Art

[0002] The switching power supply generates a line voltage drop due to line loss during use. In order to keep the line voltage of the switching power supply consistent under no-load and full-load conditions, it is necessary to add a line voltage drop compensation circuit to the switching power supply. Usually, an alloy resistor is added to the output power circuit to adjust the feedback reference of the switching power supply by detecting the voltage on the alloy resistor, thereby increasing the output voltage to compensate for the line voltage drop when overloaded. However, the additional alloy resistor will increase the loss on the alloy resistor and increase the cost.

[0003] Moreover, due to the difference in mains power in different regions, the full voltage (100-240Vac) input is considered when designing the switching power supply. However, the conversion efficiency of the switching power supply is different when it is at low voltage (100Vac) input and high voltage (240Vac) input, which will cause the heating of the switching power supply to be very different. In order to make the switching power supply safer in use, an over-temperature protection circuit is designed. However, due to the different heating caused by different input voltages, the over-temperature protection is generally set according to the low-voltage input. For example, when the temperature of the thermistor is 100°C at full load in a 45°C environment with 100Vac input, the over-temperature protection will be set at 110°C. Similarly, when the temperature of the thermistor is only 80°C at full load in a 45°C environment with 240Vac input, the over-temperature protection will be triggered at 110°C. However, since the over-temperature protection will not be triggered until 110°C, the product may not trigger the over-temperature protection even at a higher ambient temperature, which poses a certain safety risk. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a control circuit with line voltage drop compensation and over-temperature protection, so that the output voltage can be adjusted according to the load condition without adding additional alloy resistors to the output power circuit, thereby realizing line voltage drop compensation, and the over-temperature protection threshold can be adjusted according to the actual input voltage to realize more accurate over-temperature protection.

[0005] To solve the above technical problems, the purpose of the utility model is achieved through the following technical solutions: providing a control circuit with line voltage drop compensation and over-temperature protection, including a rectifier filter module, a transformer, a synchronous rectifier module, a protocol control module, a PWM control module, a power supply module and an optocoupler feedback voltage-dividing sampling module, wherein the input end of the rectifier filter module is connected to the mains, the output end of the rectifier filter module is connected to the opposite-name end of the primary winding of the transformer, the same-name end of the primary winding of the transformer is connected to the power supply module through the PWM control module, the first secondary winding of the transformer is connected to the output interface, the same-name end of the first secondary winding of the transformer is connected to the optocoupler feedback voltage-dividing sampling module and the protocol control module, the first secondary winding of the transformer is connected to the synchronous rectifier module and the protocol control module, the protocol control module is connected to the synchronous rectifier module, the output interface and the optocoupler feedback voltage-dividing sampling module, and the optocoupler feedback voltage-dividing sampling module is connected to the power supply module through the PWM control module.

[0006] The beneficial technical effect of the utility model is that the control circuit with line voltage drop compensation and over-temperature protection of the utility model is provided with a rectifier filter module, a transformer, a synchronous rectifier module, a protocol control module, a PWM control module, a power supply module and an optocoupler feedback voltage-dividing sampling module. After the mains is rectified into direct current by the rectifier filter module, the voltage on the first secondary winding of the transformer is detected through the transformer in cooperation with the protocol control module, and the input voltage corresponding to the mains is obtained according to the turns ratio of the transformer. The over-temperature protection voltage threshold is adjusted according to the input voltage corresponding to the mains obtained by conversion, so that the over-temperature protection threshold can be adjusted according to the actual input voltage, thereby achieving more accurate over-temperature protection, which is safer and more reliable. The protocol control module The synchronous rectification module, the output interface and the optocoupler feedback voltage-dividing sampling module are connected. The optocoupler feedback voltage-dividing sampling module is connected to the power supply module through the PWM control module. The protocol control module can control the operation of the power supply module through the optocoupler feedback voltage-dividing sampling module and the PWM control module to realize over-temperature protection control, and can judge the load condition according to the on-off and switching frequency of the synchronous rectification module, so as to adjust the output voltage according to the load condition to realize line voltage drop compensation. The feedback reference of the switching power supply can be adjusted without adding additional alloy resistors to the output power circuit, so as to increase the output voltage to compensate for the voltage drop on the line when overloaded, avoid increased losses due to the addition of additional alloy resistors, and avoid cost increase while realizing line voltage drop compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0008] Figure 1 A schematic diagram of a control circuit with line voltage drop compensation and over-temperature protection provided by an embodiment of the utility model;

[0009] Figure 2 A circuit schematic diagram of a control circuit with line voltage drop compensation and over-temperature protection provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0010] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0011] See also Figure 1 to Figure 2 , Figure 1 The framework schematic diagram of the control circuit with line voltage drop compensation and over-temperature protection provided in the embodiment of the utility model, the control circuit 10 with line voltage drop compensation and over-temperature protection includes a rectifier filter module 11, a transformer, a synchronous rectifier module 12, a protocol control module 13, a PWM control module 14, a power supply module 15 and an optocoupler feedback voltage-dividing sampling module 16, the input end of the rectifier filter module 11 is connected to the mains, the output end of the rectifier filter module 11 is connected to the opposite-name end of the primary winding of the transformer, and the same-name end of the primary winding of the transformer is connected to the power supply module through the PWM control module 14. The block 15 is connected, the first secondary winding of the transformer is connected to the output interface USB1, the same-name end of the first secondary winding of the transformer is connected to the optocoupler feedback voltage-dividing sampling module 16 and the protocol control module 13, the opposite-name end of the first secondary winding of the transformer is connected to the synchronous rectification module 12 and the protocol control module 13, the protocol control module 13 is connected to the synchronous rectification module 12, the output interface USB1 and the optocoupler feedback voltage-dividing sampling module 16, and the optocoupler feedback voltage-dividing sampling module 16 is connected to the power supply module 15 through the PWM control module 14.

[0012] Among them, PWM (Pulse-width modulation) control is an analog control method, which modulates the bias of the control end of the switch tube according to the change of the corresponding load to achieve the change of the conduction time of the switch tube, thereby achieving the change of the output of the switching regulated power supply. The control circuit 10 with line voltage drop compensation and over-temperature protection is provided by setting a rectifier filter module 11, a transformer, a synchronous rectifier module 12, a protocol control module 13, a PWM control module 14, a power supply module 15 and an optocoupler feedback voltage-dividing sampling module 16. After the mains is rectified into direct current by the rectifier filter module 11, the transformer cooperates with the protocol control module 13 to detect the voltage on the first secondary winding of the transformer and obtain the input voltage corresponding to the mains according to the turns ratio of the transformer. The over-temperature protection voltage threshold is adjusted according to the converted input voltage corresponding to the mains, so that the over-temperature protection threshold can be adjusted according to the actual input voltage, so as to achieve more accurate over-temperature protection, which is safer and more reliable; the protocol control module 13 and the synchronous rectifier module 12, the input The output interface USB1 is connected to the optocoupler feedback voltage-dividing sampling module 16, and the optocoupler feedback voltage-dividing sampling module 16 is connected to the power supply module 15 through the PWM control module 14. The protocol control module 13 can control the operation of the power supply module 15 through the optocoupler feedback voltage-dividing sampling module 16 and the PWM control module 14 to achieve over-temperature protection control, and can judge the load condition according to the on-off and switching frequency of the synchronous rectification module 12, so as to adjust the output voltage according to the load condition to achieve line voltage drop compensation. The feedback reference of the switching power supply can be adjusted without adding additional alloy resistors to the output power circuit, thereby increasing the output voltage to compensate for the voltage drop on the line when overloaded, avoiding increased losses due to the addition of additional alloy resistors, and avoiding cost increases while achieving line voltage drop compensation.

[0013] Specifically, in the present embodiment, the opposite-name end of the first secondary winding of the transformer is connected to ground via the third resistor R3 and the second capacitor C2 in sequence, the protocol control module 13 includes a protocol control chip U2 and a seventh resistor R7, one end of the seventh resistor R7 is connected to the opposite-name end of the first secondary winding of the transformer and the synchronous rectification module 12, the other end of the seventh resistor R7 is connected to the digital power pin of the protocol control chip U2, the timing resistor pin RT of the protocol control chip U2 is connected to the second thermistor RT2 with one end grounded, the optocoupler output pin OTPO of the protocol control chip U2 is connected to the optocoupler feedback voltage-dividing sampling module 16, the feedback pin FB of the protocol control chip U2 is connected to one end of the fifteenth resistor R15 and the optocoupler feedback voltage-dividing sampling module 16, and the other end of the fifteenth resistor R15 is connected to the optocoupler feedback voltage-dividing sampling module 16 via the ninth capacitor C9. Among them, the timing resistor pin RT of the protocol control chip U2 can output a current of 50uA. When the input voltage of the mains is 100V AC, the full-load operating temperature of the second thermistor RT2 is 100℃, and the over-temperature protection temperature at this time can be set to 110℃. The resistance value of the second thermistor RT2 at the temperature of 110℃ is 10KΩ. At this time, the voltage of the timing resistor pin RT of the protocol control chip U2 is 0.5V, and the over-temperature protection voltage threshold is 0.5V; when the input voltage of the mains is 240V AC, the full-load operating temperature of the second thermistor RT2 is 100℃. The temperature is 80℃, then the over-temperature protection temperature can be set to 90℃, and the resistance of the second thermistor RT2 is 17KΩ when the temperature is 90℃. The voltage of the timing resistor pin RT of the protocol control chip U2 is 0.85V, and the over-temperature protection voltage threshold is 0.85V, so that the over-temperature protection threshold can be adjusted according to the input voltage of the AC power, so as to achieve more accurate protection, safer and more reliable; and the protocol control chip U2 can use the resistance temperature information obtained by detecting the timing resistor pin RT connected to the second thermistor RT2, so as to perform over-temperature protection control.

[0014] Specifically, in this embodiment, the synchronous rectification module 12 includes a first switch chip U1, a high voltage pin HV of the first switch chip U1 is connected to one end of the seventh resistor R7 and the opposite end of the first secondary winding of the transformer through a sixth resistor R6, a drain of the first switch chip U1 is connected to one end of the seventh resistor R7 and the opposite end of the first secondary winding of the transformer, a power supply voltage pin VDD of the first switch chip U1 is connected to the ground, the ground pin GND of the protocol control chip U2 and one end of the fourth capacitor C4 through a third capacitor C3, and the other end of the fourth capacitor C4 is connected to the power supply voltage pin VCC of the protocol control chip U2 and an eighth resistor R8 having one end connected to the same end of the first secondary winding of the transformer. The protocol control chip U2 is used to detect the voltage drop of the first switch chip U1, thereby judging the load condition of the output, and adjusting the resistance according to the load condition, providing relatively large compensation when heavy load, relatively small compensation when light load, and no compensation when no load, so as to realize the line voltage drop compensation function. Among them, when the first switch tube chip U1 is turned on, it is judged to be loaded; when the first switch tube chip U1 is turned off but the switching frequency is high, it is also judged to be loaded; when the first switch tube chip U1 is turned off and the switching frequency is low, it is judged to be unloaded.

[0015] Specifically, in this embodiment, the optocoupler feedback voltage-dividing sampling module 16 includes a photoelectric coupler, a tenth resistor R10, an eleventh resistor R11, a sixteenth resistor R16 and an eighteenth resistor R18, one end of the tenth resistor R10 and one end of the eleventh resistor R11 are connected to the same-name end of the first secondary winding of the transformer, the other end of the tenth resistor R10 is connected to the feedback pin FB of the protocol control chip U2, one end of the fifteenth resistor R15 and one end of the sixteenth resistor R16, the other end of the sixteenth resistor R16 is grounded, the other end of the eleventh resistor R11 is connected to the anode of the light-emitting diode U4A of the photoelectric coupler and one end of the eighteenth resistor R18, the cathode of the light-emitting diode U4A of the photoelectric coupler is connected to the other end of the eighteenth resistor R18, the optocoupler output pin OTPO of the protocol control chip U2 and the ninth capacitor C9, and the photoreceiver U4B of the photoelectric coupler is connected to the PWM control module 14 through the seventeenth resistor R17.

[0016] Specifically, in this embodiment, the PWM control module 14 includes a third switch tube chip U3, the light receiver U4B of the photocoupler adopts a phototransistor, the emitter of the phototransistor is grounded, the collector of the phototransistor is connected to one end of the seventeenth resistor R17, and the other end of the seventeenth resistor R17 is connected to the feedback pin FB of the third switch tube chip U3.

[0017] Specifically, in this embodiment, the drain of the third switch tube chip U3 is connected to the anode of the first diode D1 and the same-name end of the primary winding of the transformer, the cathode of the first diode D1 is connected to the output end of the rectifier and filter module 11 and the opposite-name end of the primary winding of the transformer, the power supply voltage pin VDD of the third switch tube chip U3 is connected to the power supply module 15, and the demagnetization detection pin DEM of the third switch tube is connected to the power supply module 15.

[0018] Specifically, in this embodiment, the power supply module 15 includes a second secondary winding of the transformer, a ninth resistor R9, a fifth capacitor C5, a second diode D2 and a fourth polarity capacitor EC4, the power supply voltage pin VDD of the third switch tube chip U3 is connected to one end of the ninth resistor R9 and the cathode of the second diode D2, the other end of the ninth resistor R9 is connected to one end of the fifth capacitor C5, the other end of the fifth capacitor C5 and the anode of the second diode D2 are connected to the same-name end of the second secondary winding of the transformer, the same-name end of the second secondary winding of the transformer is connected to the demagnetization detection pin DEM of the third switch tube chip U3 after passing through the twelfth resistor R12, the opposite-name end of the second secondary winding of the transformer is grounded, the anode of the fourth polarity capacitor EC4 is connected to the power supply voltage pin VDD of the third switch tube chip U3, and the cathode of the fourth polarity capacitor EC4 is connected to the opposite-name end of the second secondary winding of the transformer and ground.

[0019] Specifically, in this embodiment, the optocoupler pin OTP of the third switch tube chip U3 is electrically connected in sequence to a thirteenth resistor R13 and a third thermistor RT3 with one end being grounded.

[0020] Specifically, in this embodiment, the data pin of the protocol control chip U2 is connected to the data end of the output interface USB1. The output interface USB1 adopts a USB interface.

[0021] Specifically, in this embodiment, the rectification and filtering module 11 includes a rectifier bridge BD1, a first inductor L1, a second resistor R2 and a third inductor L3. The input end of the rectifier bridge BD1 is connected to the AC power, the positive DC output end of the rectifier bridge BD1 is connected to one end of the first inductor L1 and one end of the second resistor R2, the other end of the first inductor L1 and the other end of the second resistor R2 are connected to the opposite-name ends of the primary winding of the transformer, and the negative DC output end of the rectifier bridge BD1 is grounded after passing through the third inductor L3.

[0022] In summary, the control circuit with line voltage drop compensation and over-temperature protection of the utility model is provided with a rectifier filter module, a transformer, a synchronous rectifier module, a protocol control module, a PWM control module, a power supply module and an optocoupler feedback voltage-dividing sampling module. After the AC power is rectified into DC power by the rectifier filter module, the voltage on the first secondary winding of the transformer is detected through the transformer in cooperation with the protocol control module, and the input voltage corresponding to the AC power is obtained according to the turns ratio of the transformer. The over-temperature protection voltage threshold is adjusted according to the input voltage corresponding to the AC power obtained by conversion, so that the over-temperature protection threshold can be adjusted according to the actual input voltage, thereby realizing more accurate over-temperature protection, which is safer and more reliable. The protocol control module and the synchronous rectifier The module, the output interface and the optocoupler feedback voltage-dividing sampling module are connected, and the optocoupler feedback voltage-dividing sampling module is connected to the power supply module through the PWM control module. The protocol control module can control the operation of the power supply module through the optocoupler feedback voltage-dividing sampling module and the PWM control module to realize over-temperature protection control, and can judge the load condition according to the on-off and switching frequency of the synchronous rectifier module, so as to adjust the output voltage according to the load condition to realize line voltage drop compensation, and the feedback reference of the switching power supply can be adjusted without adding additional alloy resistors to the output power circuit, so as to increase the output voltage to compensate for the voltage drop on the line when overloaded, avoid increasing losses due to adding additional alloy resistors, and avoid cost increase while realizing line voltage drop compensation.

[0023] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A control circuit with line voltage drop compensation and over-temperature protection, characterized in that: It includes a rectifier and filter module, a transformer, a synchronous rectifier module, a protocol control module, a PWM control module, a power supply module and an optocoupler feedback voltage-dividing sampling module, wherein the input end of the rectifier and filter module is connected to the mains, the output end of the rectifier and filter module is connected to the opposite-name end of the primary winding of the transformer, the same-name end of the primary winding of the transformer is connected to the power supply module through the PWM control module, the first secondary winding of the transformer is connected to the output interface, the same-name end of the first secondary winding of the transformer is connected to the optocoupler feedback voltage-dividing sampling module and the protocol control module, the opposite-name end of the first secondary winding of the transformer is connected to the synchronous rectifier module and the protocol control module, the protocol control module is connected to the synchronous rectifier module, the output interface and the optocoupler feedback voltage-dividing sampling module, and the optocoupler feedback voltage-dividing sampling module is connected to the power supply module through the PWM control module.

2. The control circuit with line voltage drop compensation and over-temperature protection according to claim 1, characterized in that: The opposite end of the first secondary winding of the transformer is connected to ground via a third resistor and a second capacitor in sequence; the protocol control module comprises a protocol control chip and a seventh resistor; one end of the seventh resistor is connected to the opposite end of the first secondary winding of the transformer and the synchronous rectification module; the other end of the seventh resistor is connected to a digital power pin of the protocol control chip; a timing resistor pin of the protocol control chip is connected to a second thermistor whose one end is grounded; an optocoupler output pin of the protocol control chip is connected to the optocoupler feedback voltage-dividing sampling module; a feedback pin of the protocol control chip is connected to one end of a fifteenth resistor and the optocoupler feedback voltage-dividing sampling module; and the other end of the fifteenth resistor is connected to the optocoupler feedback voltage-dividing sampling module via a ninth capacitor.

3. The control circuit with line voltage drop compensation and over-temperature protection according to claim 2, characterized in that: The synchronous rectification module includes a first switch tube chip, a high-voltage pin of the first switch tube chip is connected to one end of the seventh resistor and the opposite-name end of the first secondary winding of the transformer through a sixth resistor, a drain of the first switch tube chip is connected to one end of the seventh resistor and the opposite-name end of the first secondary winding of the transformer, a power supply voltage pin of the first switch tube chip is connected to the ground, the ground pin of the protocol control chip and one end of the fourth capacitor through a third capacitor, and the other end of the fourth capacitor is connected to the power supply voltage pin of the protocol control chip and an eighth resistor having one end connected to the same-name end of the first secondary winding of the transformer.

4. The control circuit with line voltage drop compensation and over-temperature protection according to claim 3, characterized in that: The optocoupler feedback voltage-dividing sampling module includes a photocoupler, a tenth resistor, an eleventh resistor, a sixteenth resistor and an eighteenth resistor, one end of the tenth resistor and one end of the eleventh resistor are connected to the same-name end of the first secondary winding of the transformer, the other end of the tenth resistor is connected to the feedback pin of the protocol control chip, one end of the fifteenth resistor and one end of the sixteenth resistor, the other end of the sixteenth resistor is grounded, the other end of the eleventh resistor is connected to the anode of the light-emitting diode of the photocoupler and one end of the eighteenth resistor, the cathode of the light-emitting diode of the photocoupler is connected to the other end of the eighteenth resistor, the optocoupler output pin of the protocol control chip and the ninth capacitor, and the light receiver of the photocoupler is connected to the PWM control module through the seventeenth resistor.

5. The control circuit with line voltage drop compensation and over-temperature protection according to claim 4, characterized in that: The PWM control module includes a third switch tube chip, the light receiver of the photocoupler adopts a phototransistor, the emitter of the phototransistor is grounded, the collector of the phototransistor is connected to one end of the seventeenth resistor, and the other end of the seventeenth resistor is connected to the feedback pin of the third switch tube chip.

6. The control circuit with line voltage drop compensation and over-temperature protection according to claim 5, characterized in that: The drain of the third switch tube chip is connected to the anode of the first diode and the same-name end of the primary winding of the transformer, the cathode of the first diode is connected to the output end of the rectifier and filter module and the opposite-name end of the primary winding of the transformer, the power supply voltage pin of the third switch tube chip is connected to the power supply module, and the demagnetization detection pin of the third switch tube is connected to the power supply module.

7. The control circuit with line voltage drop compensation and over-temperature protection according to claim 6, characterized in that: The power supply module includes a second secondary winding of the transformer, a ninth resistor, a fifth capacitor, a second diode and a fourth polarity capacitor. The power supply voltage pin of the third switch tube chip is connected to one end of the ninth resistor and the cathode of the second diode, the other end of the ninth resistor is connected to one end of the fifth capacitor, the other end of the fifth capacitor and the anode of the second diode are connected to the same-name end of the second secondary winding of the transformer, the same-name end of the second secondary winding of the transformer is connected to the demagnetization detection pin of the third switch tube chip after passing through a twelfth resistor, the opposite-name end of the second secondary winding of the transformer is grounded, the anode of the fourth polarity capacitor is connected to the power supply voltage pin of the third switch tube chip, and the cathode of the fourth polarity capacitor is connected to the opposite-name end of the second secondary winding of the transformer and ground.

8. The control circuit with line voltage drop compensation and over-temperature protection according to claim 5, characterized in that: The optocoupler pin of the third switch tube chip is electrically connected in sequence to a thirteenth resistor and a third thermistor with one end grounded.

9. The control circuit with line voltage drop compensation and over-temperature protection according to claim 2, characterized in that: The data pin of the protocol control chip is connected to the data end of the output interface.

10. The control circuit with line voltage drop compensation and over-temperature protection according to claim 1, characterized in that: The rectifier and filter module includes a rectifier bridge, a first inductor, a second resistor and a third inductor. The input end of the rectifier bridge is connected to the mains, the positive DC output end of the rectifier bridge is connected to one end of the first inductor and one end of the second resistor, the other end of the first inductor and the other end of the second resistor are connected to the opposite-name ends of the primary winding of the transformer, and the negative DC output end of the rectifier bridge is grounded after passing through the third inductor.

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