Feedback control circuit, switching power supply circuit and charger

Abstract

The utility model discloses a feedback control circuit, a switching power supply circuit and a charger. The feedback control circuit comprises a current acquisition circuit, a temperature detection circuit and an error amplification circuit. The current acquisition circuit is used for outputting sampling voltage to the error amplification circuit according to the output current of the current output circuit; the temperature detection circuit is used for outputting a first reference voltage to the error amplification circuit when the environment temperature is smaller than a preset temperature; the error amplification circuit is used for outputting a first feedback current to the current output circuit according to the sampling voltage and the first reference voltage. According to the feedback control circuit, the current output circuit can output low output current when the environment temperature is smaller than the preset temperature, the output load of the current output circuit at the low temperature is reduced, element characteristics of the current output circuit under the low-temperature condition are adapted, and the current output circuit is prevented from being restarted.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to a feedback control circuit, a switching power supply circuit and a charger. Background Art

[0002] In cold areas, the outdoor temperature is extremely low. When power products (such as chargers, etc.) are placed outdoors for charging, the internal components of some power products will have their component characteristics degraded due to the low temperature. For example, the electrolytic capacitors in the charger will have reduced capacity at low temperatures, affecting the output efficiency of the power product. This causes the power product to be unable to work at full load when it is just turned on, and causes a power restart. Utility Model Content

[0003] The embodiments of the utility model provide a feedback control circuit, a switching power supply circuit and a charger to solve the problem that the power supply may restart at low temperature.

[0004] The embodiment of the utility model provides a feedback control circuit, including a current acquisition circuit, a temperature detection circuit and an error amplification circuit;

[0005] The first end of the current acquisition circuit is used to be connected to the output end of the current output circuit, and the second end of the current acquisition circuit is connected to the first end of the error amplifier circuit, and is used to output a sampling voltage to the error amplifier circuit according to the output current of the current output circuit;

[0006] The temperature detection circuit is connected to the second end of the error amplifier circuit, and is used to output a first reference voltage to the error amplifier circuit when the ambient temperature is less than a preset temperature, or output a second reference voltage to the error amplifier circuit when the ambient temperature is not less than the preset temperature; the first reference voltage is less than the second reference voltage;

[0007] The third end of the error amplifier circuit is used to connect to the feedback end of the current output circuit, and is used to output a first feedback current to the current output circuit according to the sampling voltage and the first reference voltage, or to output a second feedback current to the current output circuit according to the sampling voltage and the second reference voltage.

[0008] Preferably, the temperature detection circuit includes a temperature sensing module and a voltage output module;

[0009] The temperature sensing module is used to output a first sensing signal when the ambient temperature is lower than a preset temperature, or to output a second sensing signal when the ambient temperature is not lower than a preset temperature;

[0010] The voltage output module is connected to the temperature sensing module and the error amplifier circuit, and is used to output a first reference voltage to the error amplifier circuit according to the first sensing signal, or to output a second reference voltage to the error amplifier circuit according to the second sensing signal.

[0011] Preferably, the temperature sensing module comprises a first resistor, a second resistor, a thermistor and a first voltage stabilizer;

[0012] The thermistor and the first resistor are connected in series between a voltage source and ground;

[0013] A first terminal of the first voltage stabilizer is connected to the voltage source via a second resistor, a second terminal of the first voltage stabilizer is connected to a connection node between the thermistor and the first resistor, and a third terminal of the first voltage stabilizer is grounded;

[0014] The voltage output module is connected to a connection node between the second resistor and the first voltage regulator, and the first voltage regulator is used to shut down when the ambient temperature is lower than a preset temperature and output a first sensing signal to the voltage output module, or to turn on when the ambient temperature is not lower than a preset temperature and output a second sensing signal to the voltage output module.

[0015] Preferably, the voltage output module includes a third resistor, a control tube and a voltage stabilizing circuit;

[0016] The first end of the third resistor is connected to the voltage source, and the second end of the third resistor is connected to the error amplifier circuit;

[0017] The first end of the control tube is connected to the connection node between the third resistor and the error amplifier circuit, the second end of the control tube is connected to the output end of the temperature sensing module, the third end of the control tube is connected to the first end of the voltage stabilizing circuit, and the second end of the voltage stabilizing circuit is grounded;

[0018] The control tube is used to be turned off under the control of the first sensing signal output by the temperature sensing module, so that the voltage input to the error amplifier circuit is the first reference voltage, or to be turned on under the control of the second sensing signal output by the temperature sensing module, so that the voltage input to the error amplifier circuit is the second reference voltage.

[0019] Preferably, the voltage stabilization circuit comprises a second voltage stabilizer and a first capacitor;

[0020] The first end of the first capacitor is connected to the third end of the control tube, and the second end of the first capacitor is grounded;

[0021] The first end of the second regulator is connected to the third end of the control tube, the second end of the second regulator is connected to the connection node between the first capacitor and the control tube, and the third end of the second regulator is grounded.

[0022] Preferably, the voltage output module further includes a fourth resistor and a fifth resistor;

[0023] The first end of the fourth resistor is connected to the connection node between the third resistor and the control tube, the second end of the fourth resistor is connected to the first end of the fifth resistor, the second end of the fifth resistor is grounded, and the second end of the fourth resistor is connected to the error amplifier circuit.

[0024] Preferably, the voltage output module further includes a second capacitor;

[0025] The second capacitor is connected in parallel across the fifth resistor.

[0026] Preferably, the feedback control circuit further includes an optocoupler feedback module;

[0027] The first end of the optocoupler feedback module is connected to the third end of the error amplifier circuit, and the second end of the optocoupler feedback module is used to be connected to the feedback end of the current output circuit, and is used to output the first feedback current or the second feedback current to the current output circuit under the control of the error amplifier circuit.

[0028] The embodiment of the utility model further provides a switching power supply circuit, comprising a current output circuit and any one of the feedback control circuits described above;

[0029] The current output circuit includes a primary rectification and filtering module, a primary chip, a transformer module, and a secondary rectification and filtering module;

[0030] The input end of the primary rectifier and filter module is used to connect to the mains circuit, the output end of the primary rectifier and filter module is connected to the primary end of the transformer module, the secondary end of the transformer module is connected to the input end of the secondary rectifier and filter module, and the output end of the secondary rectifier and filter module is used to connect to an external load;

[0031] The primary chip is connected to the primary end of the transformer module and is used to output a PWM signal to the transformer module;

[0032] In the feedback control circuit, the input end of the current acquisition circuit is connected to the negative output end of the secondary rectifier and filter module, and the third end of the error amplifier circuit is connected to the feedback end of the primary chip, and is used to output a first feedback current to the primary chip, so that the primary chip controls and adjusts the PWM signal according to the feedback current so that the transformer module outputs the rated current, or output a second feedback current to the primary chip, so that the primary chip controls and adjusts the PWM signal according to the second feedback current so that the current output by the transformer module is less than the rated current.

[0033] An embodiment of the utility model further provides a charger, comprising the above-mentioned switching power supply circuit.

[0034] In the feedback control circuit, the switching power supply circuit and the charger, the temperature detection circuit in the feedback control circuit can output different reference voltages according to different temperature ranges, so that the operational amplifier performs feedback control on the output current of the current output circuit according to the reference voltage, so that the current output circuit outputs a lower output current when the ambient temperature is lower than the preset temperature, reduces the output load of the current output circuit at low temperatures, adapts to the component characteristics of the current output circuit under low temperature conditions, and prevents the current output circuit from restarting; when the current output circuit runs for a period of time and the ambient temperature around the circuit rises and is no longer lower than the preset temperature, the current output circuit is controlled to output a higher output current again to ensure the output power of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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 of the utility model will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is a circuit diagram of a feedback control circuit in one embodiment of the utility model;

[0037] Figure 2 It is a block diagram schematic diagram of a switching power supply circuit in one embodiment of the utility model.

[0038] In the figure: 1. Current acquisition circuit; 2. Temperature detection circuit; 21. Temperature sensing module; 22. Voltage output module; 221. Voltage stabilization circuit; 3. Error amplification circuit; 4. Current output circuit; 41. Primary rectifier filter module; 42. Primary chip; 43. Transformer module; 44. Secondary rectifier filter module; 5. Optocoupler feedback module; DETAILED DESCRIPTION

[0039] 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.

[0040] It should be understood that the utility model can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and fully convey the scope of the utility model to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0041] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0042] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0043] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0044] In order to thoroughly understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0045] The utility model embodiment provides a feedback control circuit, such as Figure 1 As shown, it includes a current acquisition circuit 1, a temperature detection circuit 2 and an error amplifier circuit 3; the first end of the current acquisition circuit 1 is used to be connected to the output end of the current output circuit 4, and the second end of the current acquisition circuit 1 is connected to the first end of the error amplifier circuit 3, and is used to output a sampling voltage to the error amplifier circuit 3 according to the output current Io of the current output circuit 4; the temperature detection circuit 2 is connected to the second end of the error amplifier circuit 3, and is used to output a first reference voltage to the error amplifier circuit 3 when the ambient temperature is less than a preset temperature, or, when the ambient temperature is not less than a preset temperature, output a second reference voltage to the error amplifier circuit 3; the first reference voltage is less than the second reference voltage; the third end of the error amplifier circuit 3 is used to be connected to the feedback end of the current output circuit 4, and is used to output a first feedback current to the current output circuit 4 according to the sampling voltage and the first reference voltage, or, according to the sampling voltage and the second reference voltage, output a second feedback current to the current output circuit 4.

[0046] As an example, the feedback control circuit is used to provide feedback control for the output current of the current output circuit 4, and includes a current acquisition circuit 1, a temperature detection circuit 2 and an error amplifier circuit 3. Figure 2As shown, the error amplifier circuit 3 may include an operational amplifier U3, a first end of the error amplifier circuit 3 is also the non-inverting input end of the operational amplifier U3, a second end of the error amplifier circuit 3 is also the inverting input end of the operational amplifier U3, and a third end of the error amplifier circuit 3 is also the output end of the operational amplifier U3. The first end of the current acquisition circuit 1 is used to connect the output end of the current output circuit 4, and the second end of the current acquisition circuit 1 is connected to the non-inverting input end of the operational amplifier U3 in the error amplifier circuit 3. The temperature detection circuit 2 is connected to the inverting input end of the operational amplifier U3 in the error amplifier circuit 3. In the error amplifier circuit 3, the output end of the operational amplifier U3 is connected to the feedback end of the current output circuit 4.

[0047] During the operation of the circuit, the current acquisition circuit 1 acquires the output current Io of the current output circuit 4, and converts the current into a sampling voltage through a sampling resistor, and inputs it to the non-inverting input terminal of the operational amplifier U3. When the ambient temperature is less than the preset temperature, the temperature detection circuit 2 outputs a first reference voltage to the inverting input terminal of the operational amplifier U3, and the operational amplifier U3 compares the first reference voltage and the sampling voltage. When the sampling voltage is not equal to the first reference voltage, the error amplifier circuit 3 outputs a first feedback current to the current output circuit 4, and performs feedback control on the output current Io of the current output circuit 4. When the ambient temperature is not less than the preset temperature, the temperature detection circuit 2 outputs a second reference voltage to the inverting input terminal of the operational amplifier U3, and the operational amplifier U3 compares the second reference voltage and the sampling voltage. When the sampling voltage is not equal to the second reference voltage, the error amplifier circuit 3 outputs a second feedback current to the current output circuit 4, and performs feedback control on the output current Io of the current output circuit 4. Since the first reference voltage is less than the second reference voltage, when the ambient temperature is less than the preset temperature, the output current Io of the current output circuit 4 will be smaller than when the ambient temperature is greater than the preset temperature.

[0048] In this example, the temperature detection circuit 2 can output different reference voltages according to different temperature ranges, so that the operational amplifier U3 performs feedback control on the output current Io of the current output circuit 4 according to the reference voltage, so that the current output circuit 4 outputs a lower output current when the ambient temperature is lower than the preset temperature, thereby reducing the output load of the current output circuit 4 at low temperatures, adapting to the component characteristics of the current output circuit 4 under low temperature conditions, and preventing the current output circuit 4 from restarting; when the current output circuit 4 runs for a period of time and the ambient temperature around the circuit rises and is no longer lower than the preset temperature, the current output circuit 4 is controlled to re-output a higher output current to ensure the output power of the circuit.

[0049] In one embodiment, the temperature detection circuit 2 includes a temperature sensing module 21 and a voltage output module 22; the temperature sensing module 21 is used to output a first sensing signal when the ambient temperature is lower than a preset temperature, or to output a second sensing signal when the ambient temperature is not lower than a preset temperature; the voltage output module 22 is connected to the temperature sensing module 21 and the error amplifier circuit 3, and is used to output a first reference voltage to the error amplifier circuit 3 according to the first sensing signal, or to output a second reference voltage to the error amplifier circuit 3 according to the second sensing signal.

[0050] As an example, the temperature detection circuit 2 includes a temperature sensing module 21 and a voltage output module 22. The temperature sensing module 21 is connected to the voltage output module 22, and the voltage output module 22 is connected to the inverting input terminal of the operational amplifier U3 in the error amplifier circuit 3.

[0051] During the operation of the circuit, when the temperature sensing module 21 senses that the ambient temperature is lower than the preset temperature, it outputs a first sensing signal to the voltage output module 22, and the voltage output module 22 outputs a first reference voltage to the inverting input terminal of the operational amplifier U3 according to the first sensing signal; when the temperature sensing module 21 senses that the ambient temperature is not lower than the preset temperature, it outputs a second sensing signal to the voltage output module 22, and the voltage output module 22 outputs a second reference voltage to the inverting input terminal of the operational amplifier U3 according to the second sensing signal.

[0052] In one embodiment, the temperature sensing module 21 includes a first resistor R1, a second resistor R2, a thermistor Rt and a first voltage regulator U1; the thermistor Rt and the first resistor R1 are connected in series between a voltage source and a ground; a first end of the first voltage regulator U1 is connected to the voltage source through the second resistor R2, a second end of the first voltage regulator U1 is connected to a connection node between the thermistor Rt and the first resistor R1, and a third end of the first voltage regulator U1 is grounded; a voltage output module 22 is connected to a connection node between the second resistor R2 and the first voltage regulator U1, and the first voltage regulator U1 is used to shut down when the ambient temperature is less than a preset temperature and output a first sensing signal to the voltage output module 22, or to turn on when the ambient temperature is not less than a preset temperature and output a second sensing signal to the voltage output module 22.

[0053] As an example, the temperature sensing module 21 includes a first resistor R1, a second resistor R2, a thermistor Rt and a first voltage regulator U1. The thermistor Rt and the first resistor R1 are connected in series between a voltage source and ground. The voltage source can be a given voltage source of +5V. The thermistor Rt can be a thermistor Rt with a negative temperature coefficient. When the temperature rises, the resistance of the thermistor Rt decreases. For example, the first voltage regulator U1 can be a TL431 type voltage regulator. The first end of the first voltage regulator U1 is the cathode of TL431, the second end of the first voltage regulator U1 is the control end of TL431, and the third end of the first voltage regulator U1 is the anode of TL431. The cathode of TL431 is connected to the voltage source through the second resistor R2, the control end of TL431 is connected to the connection node between the thermistor Rt and the first resistor R1, and the anode of TL431 is grounded. The voltage output module 22 is connected to the connection node of the second resistor R2 and TL431.

[0054] During the operation of the circuit, when the ambient temperature is lower than the preset temperature, the resistance of the thermistor Rt is relatively high, and the voltage divided to both ends of the first resistor R1 is relatively small, so the voltage input to the control end of TL431 is insufficient to reach the on-voltage of TL431, and TL431 is in the off state. Therefore, the voltage provided by the voltage source can be directly output to the voltage output module 22 after being divided by the second resistor R2, which is equivalent to outputting a high-level voltage to the voltage output module 22, and the first sensing signal is also a high-level voltage signal. When the ambient temperature is not lower than the preset temperature, the resistance of the thermistor Rt is smaller than that at a lower temperature, so the voltage divided to both ends of the first resistor R1 increases, so that the voltage input to the control end of TL431 reaches the on-voltage of TL431, and the cathode of TL431 is connected to the ground, so the voltage output to the voltage output module 22 is also pulled down to the ground, which is equivalent to outputting a low-level voltage to the voltage output module 22, and the second sensing signal is also a low-level voltage signal.

[0055] In one embodiment, the voltage output module 22 includes a third resistor R3, a control tube Q1 and a voltage stabilizing circuit 221; the first end of the third resistor R3 is connected to the voltage source, and the second end of the third resistor R3 is connected to the error amplifier circuit 3; the first end of the control tube Q1 is connected to the connection node between the third resistor R3 and the error amplifier circuit 3, the second end of the control tube Q1 is connected to the output end of the temperature sensing module 21, the third end of the control tube Q1 is connected to the first end of the voltage stabilizing circuit 221, and the second end of the voltage stabilizing circuit 221 is grounded; the control tube Q1 is used to be turned off under the control of the first sensing signal output by the temperature sensing module 21, so that the voltage input to the error amplifier circuit 3 is the first reference voltage, or to be turned on under the control of the second sensing signal output by the temperature sensing module 21, so that the voltage input to the error amplifier circuit 3 is the second reference voltage.

[0056] As an example, the voltage output module 22 includes a third resistor R3, a control tube Q1 and a voltage stabilizing circuit 221. The first end of the third resistor R3 is connected to the voltage source, and the second end of the third resistor R3 is connected to the inverting input end of the operational amplifier U3 in the error amplifier circuit 3. The control tube Q1 can be a PNP type MOS tube, the first end of the control tube Q1 is the source of the MOS tube, the second end of the control tube Q1 is the gate of the MOS tube, the third end of the control tube Q1 is the drain of the MOS tube, the source of the MOS tube is connected to the connection node between the third resistor R3 and the operational amplifier U3, the gate of the MOS tube is connected to the output end of the temperature sensing module 21, that is, connected to the connection node between the second resistor R2 and the first voltage stabilizer U1, the drain of the MOS tube is connected to the first end of the voltage stabilizing circuit 221, and the second end of the voltage stabilizing circuit 221 is grounded.

[0057] During the operation of the circuit, when the ambient temperature is less than the preset temperature, the first voltage regulator U1 is in the off state, and the first sensing signal input to the gate of the MOS tube is a high-level voltage signal. At this time, the MOS tube is in the off state, so that the voltage of the voltage source is divided by the third resistor R3 to obtain the first reference voltage and input it to the operational amplifier U3. When the ambient temperature is not less than the preset temperature, the first voltage regulator U1 is in the on state, and the second sensing signal input to the gate of the MOS tube is a low-level voltage signal. At this time, the MOS tube is in the on state, and the voltage stabilizing circuit 221 connected to the drain of the MOS tube clamps the drain voltage of the MOS tube to a fixed voltage value, such as 2.5V. Since the internal resistance of the MOS tube is small when it is turned on, the voltage drop can be ignored, so the second reference voltage input to the operational amplifier U3 can be approximated to the drain voltage of the MOS tube. By setting the resistance value of the third resistor R3, the first reference voltage can be made smaller than the drain voltage of the MOS tube at this time, so as to achieve the effect of making the first reference voltage smaller than the second reference voltage.

[0058] In one embodiment, the voltage stabilizing circuit 221 includes a second voltage stabilizer U2 and a first capacitor C1; the first end of the first capacitor C1 is connected to the third end of the control tube Q1, and the second end of the first capacitor C1 is grounded; the first end of the second voltage stabilizer U2 is connected to the third end of the control tube Q1, the second end of the second voltage stabilizer U2 is connected to the connection node between the first capacitor C1 and the control tube Q1, and the third end of the second voltage stabilizer U2 is grounded.

[0059] As an example, the voltage stabilizing circuit 221 includes a second voltage stabilizer U2 and a first capacitor C1. The second voltage stabilizer U2 can also be a TL431 type voltage stabilizer, the first end of the first voltage stabilizer U1 is the cathode of TL431, the second end of the first voltage stabilizer U1 is the control end of TL431, and the third end of the first voltage stabilizer U1 is the anode of TL431. The first end of the first capacitor C1 is connected to the third end of the control tube Q1, and the second end of the first capacitor C1 is grounded; the first end of the second voltage stabilizer U2 is connected to the drain of the MOS tube, the second end of the second voltage stabilizer U2 is connected to the connection node between the first capacitor C1 and the MOS tube, and the third end of the second voltage stabilizer U2 is grounded. By setting the second voltage stabilizer U2 and the first capacitor C1, when the MOS tube is turned on, a voltage stabilizing effect can be formed on the drain voltage of the MOS tube, and the drain voltage can be stabilized at a fixed voltage value, such as 2.5V. The first capacitor C1 plays a filtering role to make the voltage more stable.

[0060] In one embodiment, the voltage output module 22 also includes a fourth resistor R4 and a fifth resistor R5; the first end of the fourth resistor R4 is connected to the connection node between the third resistor R3 and the control tube Q1, the second end of the fourth resistor R4 is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is grounded, and the second end of the fourth resistor R4 is connected to the error amplifier circuit 3.

[0061] As an example, the voltage output module 22 also includes a fourth resistor R4 and a fifth resistor R5; the first end of the fourth resistor R4 is connected to the connection node between the third resistor R3 and the MOS tube, the second end of the fourth resistor R4 is connected to the first end of the fifth resistor R5, the second end of the fifth resistor R5 is grounded, and the second end of the fourth resistor R4 is also connected to the inverting input terminal of the operational amplifier U3. The fourth resistor R4 and the fifth resistor R5 form a voltage dividing effect on the voltage at the connection node between the third resistor R3 and the MOS tube, and the voltage input to the inverting input terminal of the operational amplifier U3 is the same as the voltage across the fifth resistor R5. By adjusting the voltage values ​​of the third resistor R3, the fourth resistor R4 and the fifth resistor R5, the voltage value of the first reference voltage input to the operational amplifier U3 can be adjusted to adjust the current output size of the current output circuit 4 at low temperature.

[0062] In one embodiment, the voltage output module 22 further includes a second capacitor C2; the second capacitor C2 is connected in parallel across the fifth resistor R5.

[0063] As an example, the voltage output module 22 further includes a second capacitor C2. The second capacitor C2 is connected in parallel to both ends of the fifth resistor R5, and plays a filtering role, so that the first reference voltage or the second reference voltage input to the inverting input terminal of the operational amplifier U3 is more stable.

[0064] In one embodiment, the feedback control circuit also includes an optocoupler feedback module 5; the first end of the optocoupler feedback module 5 is connected to the third end of the error amplifier circuit 3, and the second end of the optocoupler feedback module 5 is used to be connected to the feedback end of the current output circuit 4, and is used to output the first feedback current or the second feedback current to the current output circuit 4 under the control of the error amplifier circuit 3.

[0065] As an example, the feedback control circuit also includes an optocoupler feedback module 5. The first end of the optocoupler feedback module 5 is connected to the output end of the operational amplifier U3, and the second end of the optocoupler feedback module 5 is used to be connected to the feedback end of the current output circuit 4. During the operation of the circuit, when the ambient temperature is less than the preset temperature, the operational amplifier U3 compares the first reference voltage and the sampling voltage, and when the sampling voltage is not equal to the first reference voltage, controls the second end of the optocoupler feedback module 5 to output the first feedback current to the current output circuit 4, and performs feedback control on the output current Io of the current output circuit 4 based on the first reference voltage standard. When the ambient temperature is not less than the preset temperature, the operational amplifier U3 compares the second reference voltage and the sampling voltage, and when the sampling voltage is not equal to the second reference voltage, controls the second end of the optocoupler feedback module 5 to output the second feedback current to the current output circuit 4, and performs feedback control on the output current Io of the current output circuit 4 based on the second reference voltage standard.

[0066] The embodiment of the utility model also provides a switching power supply circuit, including a current output circuit 4 and the feedback control circuit in the above embodiment; the current output circuit 4 includes a primary rectifier filter module 41, a primary chip 42, a transformer module 43, and a secondary rectifier filter module 44; the input end of the primary rectifier filter module 41 is used to connect to the mains circuit, the output end of the primary rectifier filter module 41 is connected to the primary end of the transformer module 43, the secondary end of the transformer module 43 is connected to the input end of the secondary rectifier filter module 44, and the output end of the secondary rectifier filter module 44 is used to connect to an external load; the primary chip 42, and the transformer module 43 The primary end of the current acquisition circuit 1 is connected to the negative output end of the secondary rectifier and filter module 44, and the error amplifier circuit 3 is connected to the feedback end of the primary chip 42, and is used to output a first feedback current to the primary chip 42, so that the primary chip 42 controls and adjusts the PWM signal according to the feedback current, so that the transformer module 43 outputs the rated current, or outputs a second feedback current to the primary chip 42, so that the primary chip 42 controls and adjusts the PWM signal according to the second feedback current, so that the current output by the transformer module 43 is less than the rated current.

[0067] As an example, the switching power supply circuit includes a current output circuit 4 and the feedback control circuit in the above example. The current output circuit 4 includes a primary rectifier filter module 41, a primary chip 42, a transformer module 43, and a secondary rectifier filter module 44. The input end of the primary rectifier filter module 41 is used to connect the mains circuit, the output end of the primary rectifier filter module 41 is connected to the primary end of the transformer module 43, the secondary end of the transformer module 43 is connected to the input end of the secondary rectifier filter module 44, and the output end of the secondary rectifier filter module 44 is used to connect the external load. The current output circuit 4 is used to rectify and filter the alternating current input from the mains circuit, and perform DC-DC voltage conversion via the transformer module 43, and then rectify and filter again via the secondary rectifier filter module 44, and convert it into direct current available to the external load. The primary chip 42 is connected to the primary end of the transformer module 43, and is used to output a PWM signal to the transformer module 43. The primary chip 42 can adjust the output current of the transformer module 43 by adjusting the duty cycle of the PWM signal. In the feedback control circuit, the input end of the current acquisition circuit 1 is connected to the negative output end of the secondary rectifier filter module 44, and the output current Io of the current output circuit 4 can be acquired through a sampling resistor. The error amplifier circuit 3 is connected to the feedback end of the primary chip 42. When the ambient temperature is lower than the preset temperature, the first feedback current can be output to the primary chip 42, so that the primary chip 42 controls and adjusts the PWM signal according to the feedback current so that the current output by the transformer module 43 is lower than the rated current. Alternatively, when the ambient temperature is not lower than the preset temperature, the second feedback current can be output to the primary chip 42, so that the primary chip 42 controls and adjusts the PWM signal according to the second feedback current so that the transformer module 43 outputs the rated current.

[0068] In this example, the temperature detection circuit 2 in the feedback control circuit can output different reference voltages according to different temperature ranges, so that the operational amplifier U3 performs feedback control on the output current Io of the current output circuit 4 according to the reference voltage, so that the current output circuit 4 outputs a lower output current when the ambient temperature is lower than the preset temperature, reduces the output load of the current output circuit 4 at low temperatures, adapts to the component characteristics of the current output circuit 4 under low temperature conditions, and prevents the current output circuit 4 from restarting. When the current output circuit 4 runs for a period of time and the ambient temperature around the circuit rises and is no longer lower than the preset temperature, the current output circuit 4 is controlled to output a higher output current again to ensure the output power of the circuit.

[0069] An embodiment of the utility model further provides a charger, comprising the switching power supply circuit in the above embodiment.

[0070] As an example, the charger includes the switching power supply circuit in the above example. The switching power supply circuit detects the ambient temperature, and when the ambient temperature is less than the preset temperature, the first reference voltage is used in the feedback control circuit to feedback control the current output circuit 4, and when the ambient temperature is not greater than the preset temperature, the larger second reference voltage is used to feedback control the current output circuit 4, so that when the ambient temperature is less than the preset temperature, the current output circuit 4 outputs a lower output current, which reduces the output load of the current output circuit 4 at low temperatures, can adapt to the component characteristics of the current output circuit 4 under low temperature conditions, and prevent the current output circuit 4 from restarting. When the current output circuit 4 runs for a period of time and the ambient temperature around the circuit rises and is no longer less than the preset temperature, the current output circuit 4 is controlled to output a higher output current again to ensure the output power of the circuit.

[0071] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A feedback control circuit, characterized in that: It includes a current acquisition circuit, a temperature detection circuit and an error amplification circuit; The first end of the current acquisition circuit is used to be connected to the output end of the current output circuit, and the second end of the current acquisition circuit is connected to the first end of the error amplifier circuit, and is used to output a sampling voltage to the error amplifier circuit according to the output current of the current output circuit; The temperature detection circuit is connected to the second end of the error amplifier circuit, and is used to output a first reference voltage to the error amplifier circuit when the ambient temperature is less than a preset temperature, or output a second reference voltage to the error amplifier circuit when the ambient temperature is not less than the preset temperature; the first reference voltage is less than the second reference voltage; The third end of the error amplifier circuit is used to connect to the feedback end of the current output circuit, and is used to output a first feedback current to the current output circuit according to the sampling voltage and the first reference voltage, or to output a second feedback current to the current output circuit according to the sampling voltage and the second reference voltage.

2. The feedback control circuit according to claim 1, characterized in that: The temperature detection circuit includes a temperature sensing module and a voltage output module; The temperature sensing module is used to output a first sensing signal when the ambient temperature is lower than a preset temperature, or to output a second sensing signal when the ambient temperature is not lower than a preset temperature; The voltage output module is connected to the temperature sensing module and the error amplifier circuit, and is used to output a first reference voltage to the error amplifier circuit according to the first sensing signal, or to output a second reference voltage to the error amplifier circuit according to the second sensing signal.

3. The feedback control circuit according to claim 2, characterized in that: The temperature sensing module includes a first resistor, a second resistor, a thermistor and a first voltage stabilizer; The thermistor and the first resistor are connected in series between a voltage source and ground; A first terminal of the first voltage stabilizer is connected to the voltage source via a second resistor, a second terminal of the first voltage stabilizer is connected to a connection node between the thermistor and the first resistor, and a third terminal of the first voltage stabilizer is grounded; The voltage output module is connected to a connection node between the second resistor and the first voltage regulator, and the first voltage regulator is used to shut down when the ambient temperature is lower than a preset temperature and output a first sensing signal to the voltage output module, or to turn on when the ambient temperature is not lower than a preset temperature and output a second sensing signal to the voltage output module.

4. The feedback control circuit according to claim 2, characterized in that: The voltage output module includes a third resistor, a control tube and a voltage stabilizing circuit; The first end of the third resistor is connected to the voltage source, and the second end of the third resistor is connected to the error amplifier circuit; The first end of the control tube is connected to the connection node between the third resistor and the error amplifier circuit, the second end of the control tube is connected to the output end of the temperature sensing module, the third end of the control tube is connected to the first end of the voltage stabilizing circuit, and the second end of the voltage stabilizing circuit is grounded; The control tube is used to be turned off under the control of the first sensing signal output by the temperature sensing module, so that the voltage input to the error amplifier circuit is the first reference voltage, or to be turned on under the control of the second sensing signal output by the temperature sensing module, so that the voltage input to the error amplifier circuit is the second reference voltage.

5. The feedback control circuit according to claim 4, characterized in that: The voltage stabilizing circuit includes a second voltage stabilizer and a first capacitor; The first end of the first capacitor is connected to the third end of the control tube, and the second end of the first capacitor is grounded; The first end of the second regulator is connected to the third end of the control tube, the second end of the second regulator is connected to the connection node between the first capacitor and the control tube, and the third end of the second regulator is grounded.

6. The feedback control circuit according to claim 4, characterized in that: The voltage output module also includes a fourth resistor and a fifth resistor; The first end of the fourth resistor is connected to the connection node between the third resistor and the control tube, the second end of the fourth resistor is connected to the first end of the fifth resistor, the second end of the fifth resistor is grounded, and the second end of the fourth resistor is connected to the error amplifier circuit.

7. The feedback control circuit according to claim 6, characterized in that: The voltage output module also includes a second capacitor; The second capacitor is connected in parallel across the fifth resistor.

8. The feedback control circuit according to claim 1, characterized in that: The feedback control circuit also includes an optocoupler feedback module; The first end of the optocoupler feedback module is connected to the third end of the error amplifier circuit, and the second end of the optocoupler feedback module is used to be connected to the feedback end of the current output circuit, and is used to output the first feedback current or the second feedback current to the current output circuit under the control of the error amplifier circuit.

9. A switching power supply circuit, characterized in that: comprising a current output circuit and a feedback control circuit according to any one of claims 1 to 8; The current output circuit includes a primary rectification and filtering module, a primary chip, a transformer module, and a secondary rectification and filtering module; The input end of the primary rectifier and filter module is used to connect to the mains circuit, the output end of the primary rectifier and filter module is connected to the primary end of the transformer module, the secondary end of the transformer module is connected to the input end of the secondary rectifier and filter module, and the output end of the secondary rectifier and filter module is used to connect to an external load; The primary chip is connected to the primary end of the transformer module and is used to output a PWM signal to the transformer module; In the feedback control circuit, the input end of the current acquisition circuit is connected to the negative output end of the secondary rectifier and filter module, and the third end of the error amplifier circuit is connected to the feedback end of the primary chip, and is used to output a first feedback current to the primary chip, so that the primary chip controls and adjusts the PWM signal according to the feedback current so that the transformer module outputs the rated current, or output a second feedback current to the primary chip, so that the primary chip controls and adjusts the PWM signal according to the second feedback current so that the current output by the transformer module is less than the rated current.

10. A charger, characterized in that: Includes the switching power supply circuit as claimed in claim 9.

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