Active power factor correction circuit, switching power supply and electronic equipment

Abstract

The invention discloses an active power factor correction circuit, a switching power supply and electronic equipment. The active power factor correction circuit comprises an input filter rectifier module, a control main module, an input voltage detection module and an output voltage control module. The input voltage of the active power factor correction circuit is detected through the input voltage detection module, the output voltage control module can output a control signal to adjust the magnitude of the output voltage according to the magnitude of the input voltage, and when it is detected that the input voltage becomes low, the control signal is output to control the output voltage to be reduced. When it is detected that the input voltage is increased, the control signal is output to control the output voltage to be increased, so that the voltage difference between the output voltage and the input voltage is relatively stable, it is guaranteed that the M value of the active power factor correction circuit is relatively stable, and the problem that the circuit is unstable due to large-range change of the input voltage is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply circuits, and in particular to an active power factor correction circuit, a switching power supply and electronic equipment. Background Art

[0002] Active power factor correction refers to controlling the switching devices through active circuits to make the input current waveform follow the input voltage waveform, thereby achieving the purpose of improving the power factor and reducing current harmonics.

[0003] The basic circuit structure of active power factor is BOOST (chopper) converter, and its basic function is to boost voltage. Therefore, the boost ratio (gain) M is an important parameter of active power factor. The output voltage Vout of the existing mainstream active power factor correction circuit is fixed. When the power input voltage Vin changes over a wide range, the active power factor correction circuit works in a wide input voltage range, and there are the following two disadvantages: at the low voltage end of the input voltage, the power factor and harmonics are not ideal, there is a large loss, and the power is reduced; at the high voltage end of the input voltage, the power factor and harmonics are not ideal, and the voltage stress of the circuit is large at the high voltage end of the input voltage. In other words, different input voltages correspond to different M values ​​to maintain the output voltage unchanged, so that the range of variation of the M value exceeds the optimal working state of the circuit, resulting in unstable circuit operation.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an active power factor correction circuit, a switching power supply and an electronic device to solve the problem of circuit instability caused by a large range of gain changes when the input voltage changes over a large range in the existing active power factor correction circuit.

[0006] The technical solution of the present invention is as follows: In a first aspect, the present invention provides an active power factor correction circuit, which includes: an input filter rectifier module, a main control module, an input voltage detection module and an output voltage control module; wherein, The input filtering and rectifying module is used to filter and rectify the input voltage; The main control module is connected to the input filter and rectifier module to output a constant output voltage; The input voltage detection module is connected to the input filtering and rectifying module and the output voltage control module respectively, and is used to feed back the detected input voltage to the output voltage control module; The output voltage control module is connected to the main control module and is used to output a control signal to adjust the output voltage according to the input voltage.

[0007] According to a further configuration of the present invention, the input filter and rectifier module comprises: an EMI filter, a rectifier bridge and a first capacitor; wherein, The EMI filter is connected to the input voltage to filter the input voltage; The input end of the rectifier bridge is connected to the output end of the EMI filter, and the output end of the rectifier bridge is respectively connected to one end of the first capacitor and the control main module, and the rectifier bridge is used to rectify the input voltage; The other end of the first capacitor is grounded.

[0008] According to a further configuration of the present invention, the input voltage detection module includes: a first diode, a first resistor, a second resistor, a third resistor and a second capacitor; wherein, The anode of the first diode is connected to the rectifier bridge, and the cathode of the first diode is connected to one end of the first resistor; The other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is connected to one end of the third resistor, and the other end of the third resistor is grounded; The second capacitor is connected in parallel with the third resistor and is connected to the output voltage control module.

[0009] In a further configuration of the present invention, the control main module includes: a dedicated integrated circuit, an inductor transformer, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a second diode, a third diode, a first switch tube, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor and a ninth capacitor; wherein, The first pin of the inductor transformer is connected to the input filter rectifier module, the second pin of the inductor transformer is connected to the drain of the first switch tube, the third pin of the inductor transformer is respectively connected to one end of the fourth resistor and one end of the fifth resistor, the other end of the fourth resistor is connected to one end of the third capacitor, and the other end of the fifth resistor is connected to the fifth pin of the ASIC; The other end of the third capacitor is connected to the anode of the second diode, and the cathode of the second diode is connected to the eighth pin of the ASIC; One end of the sixth resistor is connected to the first pin of the inductor transformer, the other end of the sixth resistor is connected to one end of the seventh resistor, and the other end of the seventh resistor is connected to the eighth pin of the ASIC; One end of the fifth capacitor is connected to the eighth pin of the ASIC, the other end of the fifth capacitor is grounded, and the sixth capacitor is connected in parallel with the fifth capacitor; The gate of the first switch tube is connected to one end of the eighth resistor, and the other end of the eighth resistor is connected to the fifth pin of the ASIC; One end of the ninth resistor is connected to the source of the first switch tube, and the other end of the ninth resistor is grounded; One end of the tenth resistor is connected to the source of the first switch tube, and the other end of the tenth resistor is connected to the fourth pin of the ASIC; The anode of the third diode is connected to the second pin of the inductor transformer, the cathode of the third diode is connected to the positive electrode of the fourth capacitor, and the negative electrode of the fourth capacitor is grounded; One end of the eleventh resistor is connected to the positive electrode of the seventh capacitor, the other end of the eleventh resistor is connected to one end of the twelfth resistor, the other end of the twelfth resistor is connected to one end of the thirteenth resistor, and the other end of the thirteenth resistor is grounded; One end of the fourteenth resistor is connected to the common end of the twelfth resistor and the thirteenth resistor, the other end of the fourteenth resistor is connected to one end of the seventh capacitor, and the other end of the seventh capacitor is connected to the second pin of the ASIC; The eighth capacitor is connected in parallel with the fourteenth resistor; One end of the fifteenth resistor is connected to the output end of the rectifier bridge, the other end of the fifteenth resistor is connected to one end of the sixteenth resistor, and the other end of the sixteenth resistor is connected to the third pin of the ASIC; One end of the ninth capacitor is connected to the third pin of the ASIC, the other end of the ninth capacitor is grounded, and the seventeenth resistor is connected in parallel to the ninth capacitor.

[0010] According to a further configuration of the present invention, the main control module further includes a voltage regulator diode; an anode of the voltage regulator diode is connected to the fourth leg of the inductor transformer, and a cathode of the voltage regulator diode is connected to the other end of the third capacitor.

[0011] According to a further configuration of the present invention, the output voltage control module includes: an operational amplifier, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor and a second switch tube; wherein, One end of the eighteenth resistor is connected to the common end of the thirteenth resistor and the fourteenth resistor, and the other end of the eighteenth resistor is connected to the drain of the second switch tube; The gate of the second switch tube is respectively connected to one end of the nineteenth resistor and one end of the twentieth resistor, the other end of the nineteenth resistor is grounded, and the other end of the twentieth resistor is connected to the seventh pin of the operational amplifier; One end of the twenty-first resistor is connected to the power supply terminal of the operational amplifier, and the other end of the twenty-first resistor is connected to the reference voltage terminal of the operational amplifier; One end of the 22nd resistor is connected to the input voltage detection module, and the other end of the 22nd resistor is connected to the non-inverting input end of the operational amplifier; The in-phase output terminal of the operational amplifier is connected to the gate of the second switch tube, the inverting input terminal of the operational amplifier is connected to the reference voltage terminal, and the source of the second switch tube is grounded.

[0012] According to a further configuration of the present invention, the output voltage control module further includes a fourth diode; an anode of the fourth diode is connected to the power supply terminal of the ASIC, and a cathode of the fourth diode is connected to the power supply terminal of the operational amplifier.

[0013] According to a further configuration of the present invention, the first switch tube is a MOS tube; and the second switch tube is a MOS tube.

[0014] In a second aspect, the present invention provides a switching power supply, which includes the active power factor correction circuit described above.

[0015] In a third aspect, the present invention provides an electronic device, comprising the switching power supply as described above.

[0016] The present invention provides an active power factor correction circuit, a switching power supply and an electronic device, wherein the active power factor correction circuit comprises: an input filter and rectifier module, a main control module, an input voltage detection module and an output voltage control module; wherein the input filter and rectifier module is used to filter and rectify the input voltage connected; the main control module is connected to the input filter and rectifier module, and is used to output a constant output voltage; the input voltage detection module is respectively connected to the input filter and rectifier module and the output voltage control module, and is used to feed back the detected input voltage to the output voltage control module; the output voltage control module is connected to the main control module, and is used to output a control signal according to the size of the input voltage to adjust the size of the output voltage. The present invention detects the input voltage of the active power factor correction circuit through an input voltage detection module, and the output voltage control module can output a control signal to adjust the output voltage according to the size of the input voltage. When it is detected that the input voltage becomes low, the output control signal controls the output voltage to decrease, and when it is detected that the input voltage increases, the output control signal controls the output voltage to increase, so that the voltage difference between the output voltage and the input voltage is relatively stable, ensuring that the M value of the active factor correction circuit is relatively stable, and avoiding the problem of circuit instability caused by a wide range of input voltage changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary personnel in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0018] Figure 1 It is the main circuit schematic diagram of the existing active power factor correction circuit.

[0019] Figure 2 It is a principle block diagram of the active power factor correction circuit in the present invention.

[0020] Figure 3 It is a circuit schematic diagram of an active power factor correction circuit in one embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the active power factor correction circuit in the present invention.

[0022] Figure 5 It is the output characteristic diagram of the MOS tube.

[0023] The symbols in the accompanying drawings are: 100, input filter and rectifier module; 200, main control module; 300, input voltage detection module; 400, output voltage control module. DETAILED DESCRIPTION

[0024] The present invention provides an active power factor correction circuit, a switching power supply and an electronic device. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] In the embodiments and the scope of the patent application, unless the text specifically defines the article, "a", "an", "the" and "the" may also include plural forms. If there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0026] It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when an element is said to be "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can also be intermediate elements. In addition, the "connection" or "coupling" used herein can include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0027] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0028] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] The inventor has found that the main circuit of the boost type active power factor correction circuit is as follows: Figure 1As shown in the figure, its working process is as follows: when the switch tube Q is turned on, the current IL flows through the inductor LA. Before the inductor is not saturated, the current increases linearly, and the electric energy is stored in the inductor in the form of magnetic energy. At this time, the capacitor C discharges to provide energy for the load; when the switch tube Q is turned off, the self-induced electromotive force VL is generated at both ends of the inductor LA to keep the current direction unchanged. In this way, the self-induced electromotive force VL is connected in series with the power supply Vin to supply power to the capacitor and the load. The basic circuit structure of the active power factor is the BOOST converter, and its basic function is to boost the voltage. Therefore, the boost ratio (gain) M is an important parameter of the active power factor.

[0030] definition: ; In the formula, M: step-up ratio (gain), Vout: output voltage, Vin: input voltage, D: duty cycle of the switch tube Q.

[0031] ; Wherein, Vref represents the reference voltage provided by the control IC (Integrated Circuit); It can be seen from the above formula that, ideally, M can reach infinity or 1. However, due to the influence of circuit parameters, switching devices, etc., the maximum gain M of the Boost converter in actual work is difficult to reach 5, and it is impossible to be very close to 1 (that is, Vout is only slightly greater than Vin), and a large range of M value changes will cause the circuit to work unstable.

[0032] The output voltage Vout of the existing mainstream active power factor correction circuit is fixed. When the power input voltage Vin changes over a wide range, the active power factor correction circuit works in a wide input voltage range. The wide variation of the M value causes the circuit to be unstable. For example, when the power input voltage range is AC80V-AC300V, the output voltage Vout of the active power factor correction must be designed to be around DC450V to ensure that the circuit has a power factor correction function when the power input voltage is AC300V. At this time, the M value of the circuit is small. When the power input voltage is AC80V, because the output voltage Vout of the circuit is fixed, the M value of the circuit is large, resulting in unstable circuit operation. That is: different input voltages correspond to different M values ​​to maintain Vout unchanged, and the M value variation range exceeds the optimal working state of the circuit. Therefore, when the power input voltage Vin changes over a wide range, the active power factor correction circuit operates in a wide input voltage range, which has the following two disadvantages: at the low voltage end of the input voltage, the power factor and harmonics are not ideal, resulting in large losses and reduced power usage; at the high voltage end of the input voltage, the power factor and harmonics are not ideal, resulting in large voltage stress of the circuit at the high voltage end of the input voltage. In other words, different input voltages correspond to different M values ​​to maintain the output voltage unchanged, so that the range of M value changes exceeds the optimal working state of the circuit, resulting in unstable circuit operation.

[0033] In view of the above technical problems, the present invention provides an active power factor correction circuit, a switching power supply and an electronic device. The active power factor correction circuit includes: an input filter and rectifier module, a control main module, an input voltage detection module and an output voltage control module; wherein the input filter and rectifier module is used to filter and rectify the input voltage connected; the control main module is connected to the input filter and rectifier module, and is used to output a constant output voltage; the input voltage detection module is respectively connected to the input filter and rectifier module and the output voltage control module, and is used to feed back the detected input voltage to the output voltage control module; the output voltage control module is connected to the control main module, and is used to output a control signal according to the size of the input voltage to adjust the size of the output voltage. The present invention detects the input voltage of the active power factor correction circuit through an input voltage detection module, and the output voltage control module can output a control signal to adjust the output voltage according to the size of the input voltage. When it is detected that the input voltage becomes low, the output control signal controls the output voltage to decrease, and when it is detected that the input voltage increases, the output control signal controls the output voltage to increase, so that the voltage difference between the output voltage and the input voltage is relatively stable, ensuring that the M value of the active power factor correction circuit is relatively stable, and avoiding the problem of circuit instability caused by a wide range of input voltage changes.

[0034] Please also see Figures 2 to 5The present invention provides a preferred embodiment of an active power factor correction circuit.

[0035] In some embodiments, Figure 2 As shown, an active power factor correction circuit provided by the present invention includes: an input filter and rectifier module 100, a main control module 200, an input voltage detection module 300 and an output voltage control module 400. The input filter and rectifier module 100 is used to filter and rectify the input voltage; the main control module 200 is connected to the input filter and rectifier module 100, and is used to output a constant output voltage; the input voltage detection module 300 is respectively connected to the input filter and rectifier module 100 and the output voltage control module 400, and is used to feed back the detected input voltage to the output voltage control module 400; the output voltage control module 400 is connected to the main control module 200, and is used to output a control signal to adjust the output voltage according to the input voltage.

[0036] Specifically, the input filter rectifier module 100 can rectify and filter the input voltage Vac, and output it to the main control module 200. After the main control module 200 is connected to the input voltage, it can output a constant output voltage. The input voltage detection module 300 can detect the input voltage at the front end of the input filter rectifier module 100 in real time, and feed back the detected input voltage to the output voltage control module 400. When it is detected that the input voltage is low, the output voltage control module 400 outputs a lower analog value to control the output voltage to decrease, and when it is detected that the input voltage increases, the output voltage control module 400 outputs a higher analog value to control the output voltage to increase. In this way, the present invention detects the input voltage of the active power factor correction circuit through the input voltage detection module 300, and the output voltage control module 400 can output a control signal to adjust the output voltage according to the size of the input voltage, so that the voltage difference between the output voltage and the input voltage is relatively stable, ensuring that the M value of the active factor correction circuit is relatively stable, and the circuit can operate in the best state to achieve the best power factor correction function, avoiding the problem of circuit instability caused by large-range changes in the input voltage, and also solving the problem of large loss when the input voltage is at the low voltage end, requiring power reduction, and large circuit stress when the input voltage is at the high voltage end.

[0037] In some embodiments, Figure 2 and Figure 3As shown, the input filter and rectifier module 100 includes: an EMI (ElectroMagnetic Interference) filter EMI, a rectifier bridge BD1 and a first capacitor C1. The EMI filter EMI is connected to the input voltage Vac to filter the input voltage Vac; the input end of the rectifier bridge BD1 is connected to the output end of the EMI filter EMI, and the output end of the rectifier bridge BD1 is respectively connected to one end of the first capacitor C1 and the control main module 200, and the rectifier bridge BD1 is used to rectify the input voltage Vac; the other end of the first capacitor C1 is grounded.

[0038] Specifically, the input AC input voltage is filtered by the EMI filter EMI and then input to the rectifier bridge BD1 for rectification. The rectified input voltage is input to the subsequent stage to power the control main module 200, wherein the first capacitor C1 is a filter capacitor.

[0039] In some embodiments, Figure 2 and Figure 3As shown, the control main module 200 includes: a dedicated integrated circuit IC1, an inductor transformer L1, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a second diode D2, a third diode D3, a first switch tube V1, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8 and a ninth capacitor C9.Among them, the first pin of the inductor transformer L1 is connected to the input filter rectifier module 100, the second pin of the inductor transformer L1 is connected to the drain of the first switch tube V1, the third pin of the inductor transformer L1 is respectively connected to one end of the fourth resistor R4 and one end of the fifth resistor R5, the other end of the fourth resistor R4 is connected to one end of the third capacitor C3, and the other end of the fifth resistor R5 is connected to the fifth pin of the application-specific integrated circuit IC1; the other end of the third capacitor C3 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the eighth pin of the application-specific integrated circuit IC1; one end of the sixth resistor R6 is connected to the first pin of the inductor transformer L1 The other end of the sixth resistor R6 is connected to one end of the seventh resistor R7, and the other end of the seventh resistor R7 is connected to the eighth pin of the ASIC IC1; one end of the fifth capacitor C5 is connected to the eighth pin of the ASIC IC1, and the other end of the fifth capacitor C5 is grounded, and the sixth capacitor C6 is connected in parallel with the fifth capacitor C5; the gate of the first switch tube V1 is connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is connected to the fifth pin of the ASIC IC1; one end of the ninth resistor R9 is connected to the source of the first switch tube V1, and the other end of the ninth resistor R9 is grounded; one end of the tenth resistor R10 is connected to the source of the first switch tube V1 The anode of the third diode D3 is connected to the second pin of the inductor transformer L1, the cathode of the third diode D3 is connected to the positive electrode of the fourth capacitor C4, and the negative electrode of the fourth capacitor C4 is grounded; one end of the eleventh resistor R11 is connected to the positive electrode of the seventh capacitor C7, the other end of the eleventh resistor R11 is connected to one end of the twelfth resistor R12, the other end of the twelfth resistor R12 is connected to one end of the thirteenth resistor R13, and the other end of the thirteenth resistor R13 is grounded; one end of the fourteenth resistor R14 is connected to the twelfth resistor R12 and the thirteenth resistor R13 The common end of the fourteenth resistor R14 is connected, the other end of the fourteenth resistor R14 is connected to one end of the seventh capacitor C7, and the other end of the seventh capacitor C7 is connected to the second pin of the application-specific integrated circuit IC1; the eighth capacitor C8 is connected to the fourteenth resistor R14 in parallel; one end of the fifteenth resistor R15 is connected to the output end of the rectifier bridge BD1, the other end of the fifteenth resistor R15 is connected to one end of the sixteenth resistor R16, and the other end of the sixteenth resistor R16 is connected to the third pin of the application-specific integrated circuit IC1; one end of the ninth capacitor C9 is connected to the third pin of the application-specific integrated circuit IC1, the other end of the ninth capacitor C9 is grounded, and the seventeenth resistor R17 is connected to the ninth capacitor C9 in parallel.

[0040] Specifically, the dedicated integrated circuit IC1 is a control integrated circuit dedicated to power factor correction (Power Factor Correction, PFC), for example, it can be a dedicated integrated circuit of model L6562. The dedicated integrated circuit can provide a reference voltage Vref to facilitate the calculation of the output voltage, and can control the conduction and cutoff of the first switch tube V1. When the first switch tube V1 is turned on, the current flows through the inductor transformer L1. Before the inductor coil of the inductor transformer L1 is not saturated, the current increases linearly, and the electric energy is stored in the inductor coil of the inductor transformer in the form of magnetic energy. At this time, the fourth capacitor C4 discharges to provide energy for the load. When the first switch tube V1 is turned off, self-induced electromotive force is generated at both ends of the inductor transformer L1 to keep the current direction unchanged. In this way, the self-induced electromotive force is connected in series with the power supply Vin to supply power to the capacitor and the load, and the output end can output a constant output voltage.

[0041] Among them, the constant output voltage .

[0042] In some embodiments, Figure 2 and Figure 3 As shown, the control main module 200 also includes a Zener diode ZD1; the anode of the Zener diode ZD1 is connected to the fourth pin of the inductor transformer L1, and the cathode of the Zener diode ZD1 is connected to the other end of the third capacitor C3. The Zener diode ZD1 can stabilize the voltage output of the inductor transformer L1.

[0043] In some embodiments, Figure 1 and Figure 2 As shown, the input voltage detection module 300 includes: a first diode D1, a first resistor R1, a second resistor R2, a third resistor R3 and a second capacitor C2. The anode of the first diode D1 is connected to the rectifier bridge BD1, and the cathode of the first diode D1 is connected to one end of the first resistor R1; the other end of the first resistor R1 is connected to one end of the second resistor R2, the other end of the second resistor R2 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is grounded; the second capacitor C2 is connected in parallel with the third resistor R3, and is connected to the output voltage control module 400.

[0044] Specifically, the first diode is connected to the 4th pin of the rectifier bridge BD1 of D1, that is, the input voltage detection module 300 detects the voltage at the front end of the rectifier bridge BD1, which can prevent interference from the subsequent circuit. The input voltage Vac charges the second capacitor C2 through the first resistor R1, the second resistor R2 and the third resistor R3, and the high or low of the input voltage Vac is reflected by the voltage across the second capacitor C2, and the voltage across the second capacitor C2 is fed back to the output voltage control module 400.

[0045] In some embodiments, Figure 2 and Figure 3 As shown, the output voltage control module 400 includes: an operational amplifier IC2, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a twenty-second resistor R22 and a second switch tube V2. Among them, one end of the eighteenth resistor R18 is connected to the common end of the thirteenth resistor R13 and the fourteenth resistor R14, and the other end of the eighteenth resistor R18 is connected to the drain of the second switch tube V2; the gate of the second switch tube V2 is respectively connected to one end of the nineteenth resistor R19 and one end of the twentieth resistor R20, the other end of the nineteenth resistor R19 is grounded, and the other end of the twentieth resistor R20 is connected to the seventh pin of the operational amplifier IC2; one end of the twenty-first resistor R21 is connected to the power supply end of the operational amplifier IC2, and the other end of the twenty-first resistor R21 is connected to the reference voltage end of the operational amplifier IC2; one end of the twenty-second resistor R22 is connected to the input voltage detection module 300, and the other end of the twenty-second resistor R22 is connected to the non-inverting input end of the operational amplifier IC2; the non-inverting output end of the operational amplifier IC2 is connected to the gate of the second switch tube V2, the inverting input end of the operational amplifier IC2 is connected to the reference voltage end Ref, and the source of the second switch tube V2 is grounded.

[0046] In this embodiment, the principle of adjusting the output voltage is to detect the input voltage and generate a corresponding control signal to control a variable resistor Radj, such as Figure 4 As shown, the parallel resistance of the variable resistor Radj and the thirteenth resistor R13 changes, and the parallel resistance of the variable resistor Radj and the thirteenth resistor R13 is recorded as Rc. Then, the output voltage can be expressed as: ; It can be seen from the above formula that when the parallel resistance Rc becomes smaller, the output voltage Vout increases; when the parallel resistance Rc becomes larger, the output voltage Vout decreases. Therefore, in order to achieve relative stability of the M value and ensure that the circuit is in the best working state, an operational amplifier is used to control the MOS tube to work in the variable resistance area to realize the change of the resistance value of the first foot (reference voltage Vref) of the special integrated circuit to the ground. When the input voltage becomes lower, the parallel resistance Rc increases, thereby reducing the output voltage Vout. When the input voltage increases, the parallel resistance Rc decreases, thereby increasing the output voltage Vout.

[0047] In this embodiment, the first switch tube V1 is a MOS tube, and the second switch tube V2 is a MOS tube.

[0048] like Figure 5 As shown, represents the drain current, Indicates the drain current of the MOS tube in the saturation state. represents the voltage between the gate and source, represents the voltage between drain and source, Represents the threshold voltage. When the MOS tube works in the amplification area, the drain-source resistance (Rds) of the MOS tube changes, that is, in the variable resistance area. Therefore, the second switch tube V2 can be used to replace the variable resistor Radj, where the variable resistance of the second switch tube V2 is recorded as Rdsa. Then, the expression of the output voltage can be expressed as: ; in, .

[0049] The 3rd pin of the operational amplifier IC2 is the reference voltage terminal Ref, and the 6th pin is the inverting input signal terminal, and the 6th pin is directly connected to the 3rd pin. The voltage of the second capacitor C2 is input to the non-inverting input terminal (5th pin) of the operational amplifier IC2 through the 22nd resistor R22 to realize integral feedback, and the control signal outputted from the output terminal (7th pin) of the operational amplifier controls the gate of the second switch tube V2 used for the variable resistor through the 20th resistor R20.

[0050] When the input voltage Vac is low, the 7th pin of the operational amplifier IC2 outputs a low analog quantity to drive the gate of the second switch tube V2 through the 20th resistor R20. The resistance of the second switch tube is high, and the equivalent resistance of the 18th resistor R18 connected in series with the second switch tube V2 is also high. The equivalent resistance of the 18th resistor R18 connected in series with the second switch tube V2 and then connected in parallel with the 13th resistor R13 is also high. Therefore, the output voltage Vout is low; when the input voltage Vac is high, the 7th pin of the operational amplifier outputs a high analog quantity to drive the gate of the second switch tube V2 through the 20th resistor R20. The resistance of the second switch tube V2 is low, and the equivalent resistance of the 18th resistor R18 connected in series with the second switch tube V2 is also low. The equivalent resistance of the 18th resistor R18 connected in series with the second switch tube V2 and then connected in parallel with the 13th resistor R13 is also low. Therefore, the output voltage Vout is high. In this way, by detecting the input voltage Vac and realizing the required analog quantity through the operational amplifier IC2, the gate of the second switch tube V2 can be controlled to function as a variable resistor, thereby reducing the output voltage when the input voltage decreases, and increasing the output voltage when the input voltage increases, thereby achieving relative stability of the M value and ensuring that the circuit can be in the best working state.

[0051] In one implementation, the operational amplifier may be a TSM103A.

[0052] In some embodiments, the output voltage control module 400 further includes a fourth diode D4; an anode of the fourth diode D4 is connected to the power supply terminal of the ASIC IC1, and a cathode of the fourth diode D4 is connected to the power supply terminal of the operational amplifier IC2.

[0053] Specifically, the operational amplifier IC2 is connected to the power pin Vcc of the ASIC IC1 through the fourth diode D4, and is powered by the ASIC IC1, which simplifies the power supply circuit of the operational amplifier IC2 and can reduce the mutual influence between the ASIC IC1 and the operational amplifier IC2.

[0054] In some embodiments, the present invention provides a switching power supply, which includes the active power factor correction circuit described above. The active power factor correction circuit is specifically as described in an embodiment of an active power factor correction circuit, which will not be repeated here.

[0055] In some embodiments, the present invention provides an electronic device, which includes the switching power supply as described above. The switching power supply is specifically as described in an embodiment of a switching power supply, which will not be described in detail here.

[0056] In summary, the active power factor correction circuit, switching power supply and electronic equipment provided by the present invention have the following beneficial effects: By detecting the input voltage of the active power factor correction circuit, the output voltage control module can output a control signal to adjust the output voltage according to the size of the input voltage. When it is detected that the input voltage is low, the output control signal controls the output voltage to decrease. When it is detected that the input voltage increases, the output control signal controls the output voltage to increase, thereby making the voltage difference between the output voltage and the input voltage relatively stable, ensuring that the M value of the active factor correction circuit is relatively stable, and avoiding the problem of circuit instability caused by a wide range of input voltage changes; The operational amplifier is powered by the power pin of the dedicated integrated circuit through a diode, which simplifies the power supply circuit of the operational amplifier and reduces the mutual influence between the two; The input voltage detection can prevent interference from the subsequent circuit by sampling from the front end of the rectifier bridge.

[0057] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An active power factor correction circuit, characterized in that: include: Input filter rectifier module, main control module, input voltage detection module and output voltage control module; among them, The input filtering and rectifying module is used to filter and rectify the input voltage; The main control module is connected to the input filter and rectifier module to output a constant output voltage; The input voltage detection module is connected to the input filtering and rectifying module and the output voltage control module respectively, and is used to feed back the detected input voltage to the output voltage control module; The output voltage control module is connected to the main control module and is used to output a control signal to adjust the output voltage according to the input voltage.

2. The active power factor correction circuit according to claim 1, characterized in that: The input filter and rectifier module includes: an EMI filter, a rectifier bridge and a first capacitor; wherein, The EMI filter is connected to the input voltage to filter the input voltage; The input end of the rectifier bridge is connected to the output end of the EMI filter, and the output end of the rectifier bridge is respectively connected to one end of the first capacitor and the control main module, and the rectifier bridge is used to rectify the input voltage; The other end of the first capacitor is grounded.

3. The active power factor correction circuit according to claim 2, characterized in that: The input voltage detection module includes: a first diode, a first resistor, a second resistor, a third resistor and a second capacitor; wherein, The anode of the first diode is connected to the rectifier bridge, and the cathode of the first diode is connected to one end of the first resistor; The other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is connected to one end of the third resistor, and the other end of the third resistor is grounded; The second capacitor is connected in parallel with the third resistor and is connected to the output voltage control module.

4. The active power factor correction circuit according to claim 2, characterized in that: The control main module includes: a dedicated integrated circuit, an inductor transformer, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a second diode, a third diode, a first switch tube, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor and a ninth capacitor; wherein, The first pin of the inductor transformer is connected to the input filter rectifier module, the second pin of the inductor transformer is connected to the drain of the first switch tube, the third pin of the inductor transformer is respectively connected to one end of the fourth resistor and one end of the fifth resistor, the other end of the fourth resistor is connected to one end of the third capacitor, and the other end of the fifth resistor is connected to the fifth pin of the ASIC; The other end of the third capacitor is connected to the anode of the second diode, and the cathode of the second diode is connected to the eighth pin of the ASIC; One end of the sixth resistor is connected to the first pin of the inductor transformer, the other end of the sixth resistor is connected to one end of the seventh resistor, and the other end of the seventh resistor is connected to the eighth pin of the ASIC; One end of the fifth capacitor is connected to the eighth pin of the ASIC, the other end of the fifth capacitor is grounded, and the sixth capacitor is connected in parallel with the fifth capacitor; The gate of the first switch tube is connected to one end of the eighth resistor, and the other end of the eighth resistor is connected to the fifth pin of the ASIC; One end of the ninth resistor is connected to the source of the first switch tube, and the other end of the ninth resistor is grounded; One end of the tenth resistor is connected to the source of the first switch tube, and the other end of the tenth resistor is connected to the fourth pin of the ASIC; The anode of the third diode is connected to the second pin of the inductor transformer, the cathode of the third diode is connected to the positive electrode of the fourth capacitor, and the negative electrode of the fourth capacitor is grounded; One end of the eleventh resistor is connected to the positive electrode of the seventh capacitor, the other end of the eleventh resistor is connected to one end of the twelfth resistor, the other end of the twelfth resistor is connected to one end of the thirteenth resistor, and the other end of the thirteenth resistor is grounded; One end of the fourteenth resistor is connected to the common end of the twelfth resistor and the thirteenth resistor, the other end of the fourteenth resistor is connected to one end of the seventh capacitor, and the other end of the seventh capacitor is connected to the second pin of the ASIC; The eighth capacitor is connected in parallel with the fourteenth resistor; One end of the fifteenth resistor is connected to the output end of the rectifier bridge, the other end of the fifteenth resistor is connected to one end of the sixteenth resistor, and the other end of the sixteenth resistor is connected to the third pin of the ASIC; One end of the ninth capacitor is connected to the third pin of the ASIC, the other end of the ninth capacitor is grounded, and the seventeenth resistor is connected in parallel to the ninth capacitor.

5. The active power factor correction circuit according to claim 4, characterized in that: The control main module also includes a voltage-stabilizing diode; the anode of the voltage-stabilizing diode is connected to the fourth pin of the inductor transformer, and the cathode of the voltage-stabilizing diode is connected to the other end of the third capacitor.

6. The active power factor correction circuit according to claim 4, characterized in that: The output voltage control module includes: an operational amplifier, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, a twenty-first resistor, a twenty-second resistor and a second switch tube; wherein, One end of the eighteenth resistor is connected to the common end of the thirteenth resistor and the fourteenth resistor, and the other end of the eighteenth resistor is connected to the drain of the second switch tube; The gate of the second switch tube is respectively connected to one end of the nineteenth resistor and one end of the twentieth resistor, the other end of the nineteenth resistor is grounded, and the other end of the twentieth resistor is connected to the seventh pin of the operational amplifier; One end of the twenty-first resistor is connected to the power supply terminal of the operational amplifier, and the other end of the twenty-first resistor is connected to the reference voltage terminal of the operational amplifier; One end of the 22nd resistor is connected to the input voltage detection module, and the other end of the 22nd resistor is connected to the non-inverting input end of the operational amplifier; The in-phase output terminal of the operational amplifier is connected to the gate of the second switch tube, the inverting input terminal of the operational amplifier is connected to the reference voltage terminal, and the source of the second switch tube is grounded.

7. The active power factor correction circuit according to claim 6, characterized in that: The output voltage control module further includes a fourth diode; an anode of the fourth diode is connected to the power supply terminal of the ASIC, and a cathode of the fourth diode is connected to the power supply terminal of the operational amplifier.

8. The active power factor correction circuit according to claim 6, characterized in that: The first switch tube is a MOS tube; the second switch tube is a MOS tube.

9. A switching power supply, characterized in that: The invention comprises the active power factor correction circuit as described in any one of claims 1 to 8.

10. An electronic device, characterized in that: Comprising the switching power supply as claimed in claim 9.

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