PFC control circuit and switching power supply circuit

Abstract

The utility model discloses a PFC (Power Factor Correction) control circuit and a switching power supply circuit. The PFC control circuit comprises a PFC circuit, a voltage division network and a main control circuit, the input end of the PFC circuit is used for being connected with a signal input end, and the output end of the PFC circuit is used for being connected with the voltage conversion circuit and used for receiving first voltage input by the signal input end and outputting second voltage to the voltage conversion circuit; the first input end of the voltage division network is connected with the input end of the PFC circuit, the second input end of the voltage division network is connected with the output end of the PFC circuit, and the output end of the voltage division network is used for outputting a target voltage division signal according to the first voltage and the second voltage; and the main control circuit is connected with the PFC circuit and the output end of the voltage division network, and is used for controlling the PFC circuit to adjust the output second voltage according to the target voltage division signal. According to the technical scheme, the second voltages with different magnitudes are output to the voltage conversion circuit according to the first voltages with different magnitudes, so that the loss of the PFC control circuit is reduced, and the working efficiency of the power supply is improved.

Description

Technical Field

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

[0002] With the continuous development of power supply technology, the output power of consumer power supplies is getting bigger and bigger, generally with 65W, 88W and 120W. However, power supplies with output power higher than 75W must meet the harmonic requirements, for example, they generally need to meet the harmonic Class-D standard. The existing technology generally adds a PFC circuit to the power supply to ensure that the power supply with output power higher than 75W meets the standard. However, the existing PFC power supply will increase the power loss and affect the working efficiency of the power supply. Utility Model Content

[0003] The embodiments of the utility model provide a PFC control circuit and a switching power supply circuit to solve the problem that the existing PFC circuit affects the power supply efficiency.

[0004] A PFC control circuit comprises a PFC circuit, a voltage dividing network and a main control circuit;

[0005] The input end of the PFC circuit is used to connect to the signal input end, and the output end of the PFC circuit is used to connect to the voltage conversion circuit, which is used to receive the first voltage input by the signal input end and output the second voltage to the voltage conversion circuit;

[0006] The first input end of the voltage divider network is connected to the input end of the PFC circuit, the second input end of the voltage divider network is connected to the output end of the PFC circuit, and the output end of the voltage divider network is used to output a target voltage divider signal according to the first voltage and the second voltage;

[0007] The main control circuit is connected to the PFC circuit and the output end of the voltage divider network, and is used to control the PFC circuit to adjust the output second voltage according to the target voltage divider signal.

[0008] Further, the voltage-dividing network includes a first voltage-dividing circuit and a voltage-dividing gating network;

[0009] A first end of the first voltage divider circuit is connected to an input end of the PFC circuit, a second end of the first voltage divider circuit is grounded, and an output end of the first voltage divider circuit is connected to a control end of the voltage divider gating network for outputting a first voltage divider signal;

[0010] A first end of the voltage divider gating network is connected to the output end of the PFC circuit, a second end of the voltage divider gating network is grounded, and a third end of the voltage divider gating network is connected to the main control circuit, and is used to output the target voltage divider signal according to the first voltage divider signal.

[0011] Further, the voltage-dividing gating network includes a main voltage-dividing circuit, a first voltage-dividing branch and a second voltage-dividing branch;

[0012] The main voltage-dividing circuit and the first voltage-dividing branch are arranged in series between the output end and the ground end of the PFC circuit, and the connection node between the main voltage-dividing circuit and the first voltage-dividing branch is connected to the main control circuit; the second voltage-dividing branch is connected in parallel with the first voltage-dividing branch and is connected to the output end of the first voltage-dividing circuit;

[0013] When the first voltage-dividing signal is less than a first threshold, the second voltage-dividing branch is open, and when the first voltage-dividing signal is not less than the first threshold, the second voltage-dividing branch is turned on.

[0014] Further, the second voltage-dividing branch includes a switch circuit and a first voltage-dividing resistor circuit;

[0015] The switch circuit and the first voltage-dividing resistor circuit are arranged in series between the main voltage-dividing circuit and the ground terminal;

[0016] The switch circuit is connected to the output end of the first voltage divider circuit and is turned on or off according to the first voltage divider signal.

[0017] Furthermore, the switch circuit includes a first switch tube and a second switch tube;

[0018] A first end of the first switch tube is connected to a first power supply end, a second end of the first switch tube is grounded, and a third end of the first switch tube is connected to an output end of the first voltage divider circuit;

[0019] A first end of the second switch tube is connected to the first voltage-dividing resistor circuit, a second end of the second switch tube is grounded, and a third end of the second switch tube is connected to the second end of the first switch tube.

[0020] Furthermore, the switch circuit also includes a first diode and a first voltage regulator tube;

[0021] The anode of the first diode is connected to the second end of the first switch tube, the cathode of the first diode is connected to the cathode of the first voltage regulator tube, and the anode of the first voltage regulator tube is connected to the third end of the second switch tube.

[0022] Further, the PFC circuit includes an inductor, a second diode, a third diode, a capacitor circuit and a third transistor;

[0023] The first end of the inductor is connected to the anode of the second diode, the second end of the inductor is connected to the anode of the third diode, and the third and fourth ends of the inductor are grounded;

[0024] The cathode of the second diode and the cathode of the second diode are used to connect the voltage conversion circuit;

[0025] The capacitor circuit is arranged in series between the second end of the inductor and the ground end;

[0026] A first terminal of the third transistor is connected to the second terminal of the inductor, a second terminal of the third transistor is grounded, and a third terminal of the third transistor is connected to the main control circuit.

[0027] A switching power supply circuit comprises a voltage conversion circuit and the above-mentioned PFC control circuit.

[0028] Furthermore, the switching power supply circuit also includes a voltage stabilizing circuit; the voltage stabilizing circuit is arranged at the output end of the voltage conversion circuit and connected to the first power supply end of the PFC control circuit, and is used to provide a regulated voltage.

[0029] Furthermore, the switching power supply circuit also includes a PFC startup circuit, which is connected to the output end of the voltage conversion circuit and the main control circuit of the PFC control circuit, and is used to collect the output power of the voltage conversion circuit and control the main control circuit to start or shut down according to the output power.

[0030] The above-mentioned PFC control circuit and switching power supply circuit, the PFC control circuit, includes a PFC circuit, a voltage divider network and a main control circuit; the input end of the PFC circuit is used to connect to the signal input end, and the output end of the PFC circuit is used to connect to the voltage conversion circuit, which is used to receive the first voltage input by the signal input end and output the second voltage to the voltage conversion circuit; the first input end of the voltage divider network is connected to the input end of the PFC circuit, the second input end of the voltage divider network is connected to the output end of the PFC circuit, and the output end of the voltage divider network is used to output a target voltage divider signal according to the first voltage and the second voltage; the main control circuit is connected to the output end of the PFC circuit and the voltage divider network, which is used to control the PFC circuit to adjust the output second voltage according to the target voltage divider signal, so as to output different second voltages to the voltage conversion circuit according to different first voltages, thereby reducing the loss of the PFC control circuit and improving the working efficiency of the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 This is a circuit diagram of a PFC control circuit in one embodiment of the utility model;

[0033] Figure 2 This is another circuit diagram of a PFC control circuit in one embodiment of the utility model;

[0034] Figure 3 This is a circuit diagram of a PFC circuit in one embodiment of the utility model;

[0035] Figure 4 This is a circuit diagram of a voltage stabilizing circuit in one embodiment of the utility model;

[0036] Figure 5 It is a circuit diagram of a switching power supply circuit in one embodiment of the utility model.

[0037] In the figure: 1. PFC control circuit; 11. PFC circuit; 12. voltage divider network; 121. first voltage divider circuit; 122. main voltage divider circuit; 123. first voltage divider branch; 124. second voltage divider branch; 1241. switch circuit; 1242. first voltage divider resistor circuit; 13. main control circuit; 2. voltage conversion circuit; 3. voltage stabilizing circuit; 4. PFC start-up circuit. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 "a", "an" and " / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of 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.

[0043] 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.

[0044] This embodiment provides a PFC control circuit 1, such as Figure 1 As shown, it is applied in a switching power supply circuit. Exemplarily, the switching power supply circuit includes a voltage conversion circuit 2 and the PFC control circuit 1. The input end of the PFC control circuit 1 is used to connect to the signal input end, the output end of the PFC control circuit 1 is connected to the input end of the switching power supply circuit, and the output end of the switching power supply circuit is used to connect to the signal output end.

[0045] The signal input terminal is used to receive a DC signal, and illustratively, the signal input terminal is connected to a power supply grid via a rectifier circuit to convert the AC signal of the power supply grid into a DC signal. The signal output terminal is used to connect a load device.

[0046] The voltage conversion circuit 2 is used for power conversion. Exemplarily, the voltage conversion circuit 2 includes a transformer.

[0047] This embodiment provides a PFC control circuit 1, such as Figure 1 As shown, it includes a PFC circuit 11, a voltage divider network 12 and a main control circuit 13; the input end of the PFC circuit 11 is used to connect to the signal input end, and the output end of the PFC circuit 11 is used to connect to the voltage conversion circuit 2, which is used to receive a first voltage input from the signal input end and output a second voltage to the voltage conversion circuit 2; the first input end of the voltage divider network 12 is connected to the input end of the PFC circuit 11, the second input end of the voltage divider network 12 is connected to the output end of the PFC circuit 11, and the output end of the voltage divider network 12 is used to output a target voltage divider signal according to the first voltage and the second voltage; the main control circuit 13 is connected to the output end of the PFC circuit 11 and the voltage divider network 12, and is used to control the PFC circuit 11 to adjust the output second voltage according to the target voltage divider signal.

[0048] As an example, the PFC circuit 11 includes an active PFC circuit 11, such as a Boost circuit. The input end of the PFC circuit 11 is used to connect to the signal input end, and the output end of the PFC circuit 11 is used to connect to the voltage conversion circuit 2, for receiving a first voltage input from the signal input end, and outputting a second voltage to the voltage conversion circuit 2. In this example, the second voltage is greater than the first voltage.

[0049] In the related art, the voltage at the input end of the voltage conversion circuit 2 is generally designed to be 390 volts. However, the inventors have found that when the first voltage is low, if the voltage at the input end of the voltage conversion circuit 2 is still maintained at 390 volts, the loss of the PFC circuit 11 will increase, thereby affecting the working efficiency of the power supply.

[0050] Therefore, in this embodiment, the first input end of the voltage divider network 12 is connected to the input end of the PFC circuit 11, the second input end of the voltage divider network 12 is connected to the output end of the PFC circuit 11, and the output end of the voltage divider network 12 is used to output a target voltage divider signal according to the first voltage and the second voltage. Exemplarily, the voltage divider network 12 first divides the first voltage, and then divides the second voltage according to the result after the first voltage is divided, and outputs different target voltage divider signals. For example, when the result after the first voltage is divided is that the first voltage is smaller, the first target voltage divider signal is output by dividing the second voltage, and when the result after the first voltage is divided is that the first voltage is larger, the second target voltage divider signal is output by dividing the second voltage. The first target voltage divider signal and the second target voltage divider signal are different in size. It can be understood that the voltage threshold for judging whether the first voltage is larger or smaller can be set by configuring the hardware parameters of the voltage divider network 12.

[0051] As an example, the main control circuit 13 is connected to the output end of the PFC circuit 11 and the voltage divider network 12, and is used to control the PFC circuit 11 to adjust the output second voltage according to the target voltage divider signal. For example, when the target voltage divider signal is the first target voltage divider signal, the PFC circuit 11 is controlled to adjust the output smaller second voltage, and when the target voltage divider signal is the second target voltage divider signal, the PFC circuit 11 is controlled to adjust the output larger second voltage, so that when the first voltage is smaller, the smaller second voltage is input to the second voltage of the voltage conversion circuit 2, and when the second voltage is larger, the larger second voltage is input to the voltage conversion circuit 2, thereby reducing the loss of the PFC control circuit 1 to improve the working efficiency of the power supply.

[0052] As an example, when the first voltage is 100-160V, that is, the first voltage is relatively small, the PFC circuit 11 is controlled to adjust the output second voltage to 256V, and when the first voltage is 165V-240V, that is, the first voltage is relatively large, the PFC circuit 11 is controlled to adjust the output second voltage to 390V, so that the magnitude of the second voltage is adjusted according to different first voltages to reduce the loss of the PFC control circuit 1 and improve the working efficiency of the power supply. In this example, when the first voltage is 100-160V, the power supply efficiency with the second voltage of 265V is 0.5% higher than the power supply efficiency of the whole machine when the first voltage is 100-160V and the second voltage is 390V.

[0053] As an example, the main control circuit 13 includes a main control chip U1, a GATE terminal of the main control chip U1 is used to connect to the PFC circuit 11, and a GND terminal of the main control chip U1 is grounded. The FB terminal of the main control chip U1 is used to connect to the voltage divider network 12. The FB terminal of the main control chip U1 is also grounded through a capacitor C6.

[0054] In this embodiment, the PFC control circuit 1 includes a PFC circuit 11, a voltage divider network 12 and a main control circuit 13; the input end of the PFC circuit 11 is used to connect to the signal input end, and the output end of the PFC circuit 11 is used to connect to the voltage conversion circuit 2, which is used to receive a first voltage input from the signal input end and output a second voltage to the voltage conversion circuit 2; the first input end of the voltage divider network 12 is connected to the input end of the PFC circuit 11, the second input end of the voltage divider network 12 is connected to the output end of the PFC circuit 11, and the output end of the voltage divider network 12 is used to output a target voltage division signal according to the first voltage and the second voltage; the main control circuit 13 is connected to the output end of the PFC circuit 11 and the voltage divider network 12, and is used to control the PFC circuit 11 to adjust the output second voltage according to the target voltage division signal, so as to output second voltages of different magnitudes to the voltage conversion circuit 2 according to first voltages of different magnitudes, thereby reducing the loss of the PFC control circuit 1 to improve the working efficiency of the power supply.

[0055] In one embodiment, if Figure 2 As shown, the voltage-dividing network 12 includes a first voltage-dividing circuit 121 and a voltage-dividing gating network; a first end of the first voltage-dividing circuit 121 is connected to an input end of the PFC circuit 11, a second end of the first voltage-dividing circuit 121 is grounded, an output end of the first voltage-dividing circuit 121 is connected to a control end of the voltage-dividing gating network, and is used to output a first voltage-dividing signal; a first end of the voltage-dividing gating network is connected to an output end of the PFC circuit 11, a second end of the voltage-dividing gating network is grounded, and a third end of the voltage-dividing gating network is connected to a main control circuit 13, and is used to output a target voltage-dividing signal according to the first voltage-dividing signal.

[0056] As an example, the first voltage divider circuit 121 includes a first resistor circuit and a second resistor circuit, the first resistor circuit and the second resistor circuit are arranged in series between the input terminal of the PFC circuit 11 and the ground, and the connection node between the first resistor circuit and the second resistor circuit is connected to the control terminal of the voltage divider gating network. Exemplarily, the first resistor circuit includes at least one first resistor, such as Figure 2 The second resistor circuit includes at least one second resistor, for example Figure 2 The resistor R64 in series in the circuit. In this example, under the voltage division effect of the first resistor circuit and the second resistor circuit, a first voltage-divided signal is output according to the first voltage. The magnitude ratio relationship between the first voltage and the first voltage-divided signal can be adjusted by configuring the resistance values ​​of the first resistor circuit and the second resistor circuit. The second resistor circuit is also connected in parallel with the capacitor C30 to provide a stable first voltage-divided signal.

[0057] As an example, the first end of the voltage-dividing gating network is connected to the output end of the PFC circuit 11, the second end of the voltage-dividing gating network is grounded, and the third end of the voltage-dividing gating network is connected to the main control circuit 13, and is used to output a target voltage-dividing signal according to the first voltage-dividing signal. In this example, if the first voltage-dividing signal is small, the voltage-dividing gating network outputs a small first target voltage-dividing signal, and if the first voltage-dividing signal is large, the voltage-dividing gating network outputs a large first target voltage-dividing signal, thereby automatically identifying whether the first voltage is large or small according to the first voltage-dividing signal, so as to output different target voltage-dividing signals to the main control circuit 13.

[0058] In one embodiment, if Figure 2 As shown, the voltage-dividing gating network includes a main voltage-dividing circuit 122, a first voltage-dividing branch 123 and a second voltage-dividing branch 124; the main voltage-dividing circuit 122 and the first voltage-dividing branch 123 are arranged in series between the output end and the ground end of the PFC circuit 11, and the connection node between the main voltage-dividing circuit 122 and the first voltage-dividing branch 123 is connected to the main control circuit 13; the second voltage-dividing branch 124 is connected in parallel with the first voltage-dividing branch 123 and is connected to the output end of the first voltage-dividing circuit 121; wherein, when the first voltage-dividing signal is less than the first threshold value, the second voltage-dividing branch 124 is open, and when the first voltage-dividing signal is not less than the first threshold value, the second voltage-dividing branch 124 is turned on.

[0059] The first threshold is the threshold at which the second voltage-dividing branch 124 switches from open circuit to conduction. The circuit parameters of the second voltage-dividing branch 124 can be configured by the proportional relationship between the first voltage-dividing signal and the first voltage to determine the first threshold. It is ensured that when the first voltage-dividing signal is less than the first threshold, the second voltage-dividing branch 124 is open circuited, and when the first voltage-dividing signal is not less than the first threshold, the second voltage-dividing branch 124 is conducted.

[0060] As an example, the first voltage-dividing circuit 121 divides the first voltage to form a first voltage-dividing signal, and outputs the first voltage-dividing signal to the second voltage-dividing branch 124 through the output end of the first voltage-dividing circuit 121. When the first voltage-dividing signal is less than the first threshold value, the second voltage-dividing branch 124 is open, so that the second voltage is divided by the main voltage-dividing circuit 122 and the first voltage-dividing branch 123 to form a first target voltage-dividing signal. When the first voltage-dividing signal is not less than the first threshold value, the second voltage-dividing branch 124 is turned on, and the second voltage is divided by the main voltage-dividing circuit 122 and the second voltage-dividing branch 124 and the first voltage-dividing branch 123 connected in parallel to form a second target voltage-dividing signal, so that the main control circuit 13 is indicated by different target voltage-dividing signals to control the PFC circuit 11 to adjust the output of different second voltages, so that different second voltages are output to the voltage conversion circuit 2 according to different first voltages, thereby reducing the loss of the PFC control circuit 1 to improve the working efficiency of the power supply.

[0061] As an example, the main voltage divider circuit 122 includes at least one resistor, such as Figure 2 Resistor R5, resistor R6 and resistor R7 are shown.

[0062] In one embodiment, the second voltage-dividing branch 124 includes a switching circuit 1241 and a first voltage-dividing resistor circuit 1242; the switching circuit 1241 and the first voltage-dividing resistor circuit 1242 are arranged in series between the main voltage-dividing circuit 122 and the ground terminal; the switching circuit 1241 is connected to the output terminal of the first voltage-dividing circuit 121, and is turned on or off according to the first voltage-dividing signal.

[0063] As an example, Figure 2 As shown, the first voltage-dividing resistor circuit 1242 includes a resistor R65.

[0064] In this embodiment, by turning on or off the switch circuit 1241 , the voltage-dividing gating network can automatically output different target voltage-dividing signals to the main control circuit 13 according to different first voltage-dividing signals.

[0065] In one embodiment, if Figure 2 As shown, the switch circuit 1241 includes a first switch tube Q9 and a second switch tube Q8; the first end of the first switch tube Q9 is connected to the first power supply end VCC1, the second end of the first switch tube Q9 is grounded, and the third end of the first switch tube Q9 is connected to the output end of the first voltage divider circuit 121; the first end of the second switch tube Q8 is connected to the first voltage divider resistor circuit 1242, the second end of the second switch tube Q8 is grounded, and the third end of the second switch tube Q8 is connected to the second end of the first switch tube Q9.

[0066] The first switch tube Q9 and the second switch tube Q8 may be switch tubes of different types or of the same type. Preferably, the first switch tube Q9 and the second switch tube Q8 are switch tubes of different types. Exemplarily, the first switch tube Q9 is a bipolar transistor, and the second switch tube Q8 is a field effect transistor.

[0067] As an example, the first end of the first switch tube Q9 is the collector, the second end of the first switch tube Q9 is the emitter, and the third end of the first switch tube Q9 is the base. The first end of the second switch tube Q8 is the source, the second end of the second switch tube Q8 is the drain, and the third end of the second switch tube Q8 is the gate. It should be noted that the first threshold in the above embodiment is the conduction threshold of the first switch tube Q9.

[0068] As an example, Figure 2 As shown, the second end of the first switch tube Q9 is also grounded through the capacitor C31. The third end of the second switch tube Q8 is grounded through the resistor R70 and the capacitor C32 connected in parallel, and the second end of the second switch tube Q8 is grounded through the resistor R60.

[0069] In this example, by configuring the circuit parameters of the first voltage divider circuit 121, it is ensured that when the first voltage is relatively small, the first voltage divider signal is smaller than the conduction threshold of the first switch tube Q9, so that the first switch tube Q9 and the second switch tube Q8 are both not turned on, and the switch circuit 1241 is in an open circuit. When the first voltage is relatively large, the first voltage divider signal is not smaller than the conduction threshold of the first switch tube Q9, so that the first switch tube Q9 and the second switch tube Q8 are both turned on, and the switch circuit 1241 is in a conducting state.

[0070] In one embodiment, the switch circuit 1241 also includes a first diode D2A and a first voltage regulator tube ZD2; the anode of the first diode D2A is connected to the second end of the first switch tube Q9, the cathode of the first diode D2A is connected to the cathode of the first voltage regulator tube ZD2, and the anode of the first voltage regulator tube ZD2 is connected to the third end of the second switch tube Q8.

[0071] In this embodiment, the first diode D2A can prevent current backflow. The first voltage regulator tube ZD2 can provide a stable driving voltage to the second switch tube Q8.

[0072] In one embodiment, if Figure 3 As shown, the PFC circuit 11 includes an inductor L2, a second diode D1, a third diode D2, a capacitor circuit and a third transistor Q1; the first end 1 of the inductor L2 is connected to the anode of the second diode D1, the second end of the inductor L2 is connected to the anode of the third diode D2, and the third end 2 and the fourth end 4 of the inductor L2 are grounded PGND; the cathode of the second diode D1 and the cathode of the second diode D1 are used to connect the voltage conversion circuit 2; the capacitor circuit is arranged in series between the second end of the inductor L2 and the ground end; the first end of the third transistor Q1 is connected to the second end of the inductor L2, the second end of the third transistor Q1 is grounded, and the third end of the third transistor Q1 is connected to the main control circuit 13.

[0073] The third transistor Q1 may be a bipolar transistor or a field effect transistor, wherein the first end of the third transistor Q1 is a collector or a source, the second end of the third transistor Q1 is an emitter or a drain, and the third end of the third transistor Q1 is a base or a gate.

[0074] As an example, Figure 3 As shown, the capacitor circuit includes capacitors EC1, EC2 and EC3 connected in parallel.

[0075] In this embodiment, when the first voltage is relatively small, the main control circuit 13 outputs a first control signal to the third end of the third transistor Q1 to control the switching frequency of the third transistor Q1, thereby controlling the PFC circuit 11 to output a relatively small second voltage; when the first voltage is relatively large, the main control circuit 13 outputs a second control signal to the third end of the third transistor Q1 to control the switching frequency of the third transistor Q1, thereby controlling the PFC circuit 11 to output a relatively large second voltage, thereby reducing the loss of the PFC circuit 11 when the first voltage is relatively small, thereby improving the working efficiency of the power supply.

[0076] This embodiment provides a switching power supply circuit, including a voltage conversion circuit 2 and the PFC control circuit 1 in the above embodiment.

[0077] In this embodiment, an input end of the voltage conversion circuit 2 is connected to an output end of the PFC circuit 11 in the PFC control circuit 1 .

[0078] In one embodiment, if Figure 4 As shown, the switching power supply circuit further includes a voltage stabilizing circuit 3; the voltage stabilizing circuit 3 is arranged at the output end of the voltage conversion circuit 2 and connected to the first power supply end VCC1 of the PFC control circuit 1, for providing a regulated voltage.

[0079] In this embodiment, the voltage stabilizing circuit 3 is arranged at the output end of the voltage conversion circuit 2 and connected to the first power supply end VCC1 of the PFC control circuit 1, and is used to provide a regulated voltage to the first power supply end VCC1, so that the switch circuit 1241 in the voltage dividing network 12 can work stably. Exemplarily, the voltage stabilizing circuit 3 is connected to the output end of the voltage conversion circuit 2 through the VCC end.

[0080] As an example, Figure 4 As shown, the voltage stabilizing circuit 3 includes a transistor Q6, a diode D9, a voltage stabilizing tube ZD1, a resistor R38 and a capacitor C27. The specific connection relationship thereof is shown in FIG. Figure 4 It should be noted that other voltage stabilizing circuits 3 may also be used, as long as they can provide a regulated voltage to the first power supply terminal VCC1 so that the switch circuit 1241 in the voltage dividing network 12 can work stably, and there is no limitation here.

[0081] In one embodiment, the switching power supply circuit further includes a PFC startup circuit 4 , which is connected to the main control circuit 13 of the PFC control circuit 1 and is used to control the main control circuit 13 to start or shut down.

[0082] As an example, the PFC startup circuit 4 includes an optocoupler, a transistor Q3A, a resistor R44, a resistor R67 and a resistor R66. The specific connection relationship thereof is shown in FIG. Figure 2As shown, no limitation is made here. When the output power is relatively low, the PFCON / OFF port of the PFC startup circuit 4 is used to receive a high-level signal, the light-emitting diode U6A works, the phototransistor U6B is turned on, and the voltage-dividing effect of the resistor R66 and the resistor R67 on the output voltage of the first power supply terminal VCC1 causes the transistor Q3A to be turned on, thereby supplying power to the power supply terminal VCC of the main control chip U1 of the main control circuit 13 through the first power supply terminal VCC1 and the second power supply terminal VCC-PFC. The second power supply terminal VCC-PFC is used to connect the power supply terminal VCC of the main control chip U1. The second power supply terminal VCC-PFC is also grounded through the capacitor C4.

[0083] 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 PFC control circuit, characterized in that: Including PFC circuit, voltage divider network and main control circuit; The input end of the PFC circuit is used to connect to the signal input end, and the output end of the PFC circuit is used to connect to the voltage conversion circuit, which is used to receive the first voltage input by the signal input end and output the second voltage to the voltage conversion circuit; The first input end of the voltage divider network is connected to the input end of the PFC circuit, the second input end of the voltage divider network is connected to the output end of the PFC circuit, and the output end of the voltage divider network is used to output a target voltage divider signal according to the first voltage and the second voltage; The main control circuit is connected to the PFC circuit and the output end of the voltage divider network, and is used to control the PFC circuit to adjust the output second voltage according to the target voltage divider signal.

2. The PFC control circuit according to claim 1, characterized in that: The voltage-dividing network includes a first voltage-dividing circuit and a voltage-dividing gating network; A first end of the first voltage divider circuit is connected to an input end of the PFC circuit, a second end of the first voltage divider circuit is grounded, and an output end of the first voltage divider circuit is connected to a control end of the voltage divider gating network for outputting a first voltage divider signal; A first end of the voltage divider gating network is connected to the output end of the PFC circuit, a second end of the voltage divider gating network is grounded, and a third end of the voltage divider gating network is connected to the main control circuit, and is used to output the target voltage divider signal according to the first voltage divider signal.

3. The PFC control circuit according to claim 2, characterized in that: The voltage-dividing gating network includes a main voltage-dividing circuit, a first voltage-dividing branch and a second voltage-dividing branch; The main voltage-dividing circuit and the first voltage-dividing branch are arranged in series between the output end and the ground end of the PFC circuit, and the connection node between the main voltage-dividing circuit and the first voltage-dividing branch is connected to the main control circuit; the second voltage-dividing branch is connected in parallel with the first voltage-dividing branch and is connected to the output end of the first voltage-dividing circuit; When the first voltage-dividing signal is less than a first threshold, the second voltage-dividing branch is open, and when the first voltage-dividing signal is not less than the first threshold, the second voltage-dividing branch is turned on.

4. The PFC control circuit according to claim 3, characterized in that: The second voltage-dividing branch includes a switch circuit and a first voltage-dividing resistor circuit; The switch circuit and the first voltage-dividing resistor circuit are arranged in series between the main voltage-dividing circuit and the ground terminal; The switch circuit is connected to the output end of the first voltage divider circuit and is turned on or off according to the first voltage divider signal.

5. The PFC control circuit according to claim 4, characterized in that: The switch circuit includes a first switch tube and a second switch tube; A first end of the first switch tube is connected to a first power supply end, a second end of the first switch tube is grounded, and a third end of the first switch tube is connected to an output end of the first voltage divider circuit; A first end of the second switch tube is connected to the first voltage-dividing resistor circuit, a second end of the second switch tube is grounded, and a third end of the second switch tube is connected to the second end of the first switch tube.

6. The PFC control circuit according to claim 5, characterized in that: The switch circuit also includes a first diode and a first voltage regulator tube; The anode of the first diode is connected to the second end of the first switch tube, the cathode of the first diode is connected to the cathode of the first voltage regulator tube, and the anode of the first voltage regulator tube is connected to the third end of the second switch tube.

7. The PFC control circuit according to claim 1, characterized in that: The PFC circuit includes an inductor, a second diode, a third diode, a capacitor circuit and a third transistor; The first end of the inductor is connected to the anode of the second diode, the second end of the inductor is connected to the anode of the third diode, and the third and fourth ends of the inductor are grounded; The cathode of the second diode and the cathode of the second diode are used to connect the voltage conversion circuit; The capacitor circuit is arranged in series between the second end of the inductor and the ground end; A first terminal of the third transistor is connected to the second terminal of the inductor, a second terminal of the third transistor is grounded, and a third terminal of the third transistor is connected to the main control circuit.

8. A switching power supply circuit, characterized in that: The invention comprises a voltage conversion circuit and a PFC control circuit as claimed in any one of claims 1 to 6.

9. The switching power supply circuit according to claim 8, characterized in that: The switching power supply circuit also includes a voltage stabilizing circuit; the voltage stabilizing circuit is arranged at the output end of the voltage conversion circuit and connected to the first power supply end of the PFC control circuit, and is used to provide a regulated voltage.

10. The switching power supply circuit according to claim 8, characterized in that: The switching power supply circuit also includes a PFC startup circuit, which is connected to the output end of the voltage conversion circuit and the main control circuit of the PFC control circuit, and is used to collect the output power of the voltage conversion circuit and control the main control circuit to start or shut down according to the output power.

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