Transformer switching circuit, switching power supply circuit and charger

Abstract

The utility model discloses a transformer switching circuit, a switching power supply circuit and a charger. The transformer switching circuit comprises a switching module and a detection control module, the switching module comprises a fixed end, a first contact, a second contact and a change-over switch, the fixed end is used for being connected with the output end of the transformer module, the first contact is used for being connected with an output terminal of a secondary winding of the transformer module, the second contact is used for being connected with a tap of the secondary winding of the transformer module, and the change-over switch is connected with the output terminal of the secondary winding of the transformer module. The first end of the change-over switch is connected with the fixed end, and the second end of the change-over switch is connected with the first contact or the second contact in a switching mode. The transformer switching circuit can control the change-over switch in the switching module to be connected with the first contact or the second contact in a switching manner so as to change the turn ratio of the primary side to the secondary side of the transformer module, so that the turn ratio of the primary side to the secondary side of the current transformer module adapts to the current circuit output state, and the working efficiency is improved.

Description

Technical Field

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

[0002] With the continuous development of fast charging power supplies, the voltage and power output range of the switching power supply circuit used in fast charging power supplies is constantly widening. Since the output voltage of fast charging power supplies is usually designed based on the maximum output voltage, the transformer module of the fast charging power supply will suffer losses when the voltage is low, resulting in reduced power efficiency. Utility Model Content

[0003] The embodiments of the utility model provide a transformer switching circuit, a switching power supply circuit and a charger to solve the problem that the transformer module will be lost when the voltage is low.

[0004] The embodiment of the utility model provides a transformer switching circuit, including a switching module and a detection control module;

[0005] The switching module includes a fixed end, a first contact, a second contact and a switching switch, wherein the fixed end is used to be connected to the output end of the transformer module, the first contact is used to be connected to the output terminal of the secondary winding of the transformer module, the second contact is used to be connected to the tap of the secondary winding of the transformer module, the first end of the switching switch is connected to the fixed end, and the second end of the switching switch is switched to be connected to the first contact or the second contact;

[0006] The input end of the detection control module is connected to the output end of the transformer module, and the output end of the detection control module is connected to the switching switch, which is used to output a switching signal according to the output end voltage of the transformer module to control the second end of the switching switch to switch the connection to the first contact or the second contact.

[0007] Preferably, the detection control module includes a detection unit and a control unit;

[0008] The first end of the detection unit is connected to the output end of the transformer module, and the second end of the detection unit is connected to the first end of the control unit, and is used to output a control voltage to the control unit according to the output end voltage of the transformer module;

[0009] The second end of the control unit is connected to the switch, and is used to output a switching signal to the switch according to the control voltage.

[0010] Preferably, the detection unit includes a sampling unit, a reference voltage generating unit and an operational amplifier;

[0011] The input end of the sampling unit is connected to the output end of the transformer module, and the output end of the sampling unit is connected to the inverting input end of the operational amplifier to output the sampling voltage to the operational amplifier;

[0012] The input end of the reference voltage generating unit is connected to the output end of the transformer module, and the output end of the reference voltage generating unit is connected to the in-phase input end of the operational amplifier to output the reference voltage to the operational amplifier;

[0013] The output end of the operational amplifier is connected to the control unit and is used to output a control voltage to the control unit according to the magnitudes of the sampling voltage and the reference voltage.

[0014] Preferably, the sampling unit comprises a first resistor and a second resistor;

[0015] The first resistor and the second resistor are connected in series between the output terminal of the transformer module and the ground;

[0016] The inverting input terminal of the operational amplifier is connected to a connection node between the first resistor and the second resistor.

[0017] Preferably, the reference voltage generating unit comprises a third resistor and a voltage stabilizing unit;

[0018] The third resistor and the voltage stabilizing unit are connected in series between the output end of the transformer module and the ground;

[0019] The inverting input terminal of the operational amplifier is connected to a connection node between the third resistor and the voltage stabilizing unit.

[0020] Preferably, the voltage stabilizing unit comprises a voltage stabilizing tube;

[0021] The first end and the second end of the voltage regulator tube are connected to the third resistor, and the third end of the voltage regulator tube is grounded.

[0022] Preferably, the control unit includes a switch tube;

[0023] The first end of the switch tube is connected to the output end of the transformer module, the second end of the switch tube is connected to the detection unit, and the third end of the switch tube is connected to the switching switch, and is used to output a switching signal to the switching switch according to the control voltage.

[0024] Preferably, the switching switch comprises an armature and an electromagnetic mechanism;

[0025] The first end of the armature is connected to the fixed end, and the second end of the armature is switchably connected to the first contact or the second contact;

[0026] The electromagnetic mechanism is connected to the output end of the detection control module, and is used to control the second end of the armature to switch and connect to the first contact or the second contact according to the switching signal.

[0027] The embodiment of the utility model also provides a switching power supply circuit, including a primary rectifier filter module, a transformer module, a secondary rectifier filter module and the above-mentioned transformer switching circuit;

[0028] The input end of the primary rectifier and filter module is used to connect to the mains circuit, the output end of the primary rectifier and filter module is connected to the input end of the transformer module, the output end of the transformer module is connected to the input end of the secondary rectifier and filter module, and the output end of the secondary rectifier and filter module is used to connect to an external load and output a supply voltage to the external load;

[0029] The input end of the detection control module is connected to the output end of the transformer module through the secondary rectification and filtering module.

[0030] An embodiment of the utility model further provides a charger, comprising the above-mentioned switching power supply circuit.

[0031] In the transformer switching circuit, switching power supply circuit and charger provided by the embodiments of the utility model, the detection control module can control the switching switch in the switching module to switch the connection to the first contact or the second contact according to the output voltage of the transformer module, so as to change the primary-to-secondary turns ratio of the transformer module, so that the current primary-to-secondary turns ratio of the transformer module adapts to the current circuit output state, thereby improving the working efficiency of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] Figure 1 It is a block diagram of a switching power supply circuit in one embodiment of the utility model;

[0034] Figure 2 It is a circuit structure schematic diagram of a transformer switching circuit in one embodiment of the utility model.

[0035] In the figure: 1. switching module; 2. detection control module; 21. detection unit; 211. sampling unit; 212. reference voltage generating unit; 22. control unit 22; 3. transformer module; 4. primary rectifier and filter module; 5. secondary rectifier and filter module. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0041] 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.

[0042] An embodiment of the utility model provides a transformer switching circuit, including a switching module 1 and a detection and control module 2; the switching module 1 includes a fixed end A, a first contact B, a second contact C and a switching switch K1, the fixed end A is used to be connected to the output end of the transformer module 3, the first contact B is used to connect the output terminal of the secondary winding of the transformer module 3, the second contact C is used to connect the tap of the secondary winding of the transformer module 3, the first end of the switching switch K1 is connected to the fixed end A, and the second end of the switching switch K1 is switched to connect to the first contact B or the second contact C; the input end of the detection and control module 2 is connected to the output end of the transformer module 3, and the output end of the detection and control module 2 is connected to the switching switch K1, which is used to output a switching signal according to the output end voltage of the transformer module 3, and control the second end of the switching switch K1 to switch to connect to the first contact B or the second contact C.

[0043] As an example, the transformer switching circuit is used to connect with the transformer module 3, including a switching module 1 and a detection control module 2. The switching module 1 includes a fixed terminal A, a first contact B, a second contact C and a switch K1. In the transformer module 3, the positive output terminal of the secondary winding of the transformer module 3 is connected to the first contact B, the negative output terminal is grounded, and the tap between the positive output terminal and the negative output terminal is connected to the second contact C. The fixed terminal A of the switching module 1 is connected to the output end of the transformer module 3, the first end of the switch K1 is connected to the fixed terminal A, and the second end of the switch K1 can be switched to connect to the first contact B or the second contact C. The input end of the detection control module 2 is connected to the output end of the transformer module 3, and the output end of the detection control module 2 is connected to the switch K1.

[0044] During circuit operation, the detection control module 2 obtains the output voltage of the transformer module 3, and outputs a switching signal to the switch K1 according to the output voltage, so that the switch K1 switches to connect the first contact B or the second contact C under the action of the switching signal. Specifically, when the output voltage of the transformer module 3 is greater than the preset voltage, it means that the circuit is currently in a high output voltage state, and the detection control module 2 outputs a first switching signal to the switching switch K1, so that the switching switch K1 switches to connect the first contact B under the action of the first switching signal, so that the positive output terminal of the secondary winding of the transformer module 3 is connected to the output end of the transformer module 3, so that the primary-secondary turns ratio of the transformer module 3 adapts to the current high output voltage state; when the output voltage of the transformer module 3 is not greater than the preset voltage, it means that the voltage is currently in a low output voltage state, and the detection control module 2 outputs a second switching signal to the switching switch K1, so that the switching switch K1 switches to connect the second contact C under the action of the second switching signal, so that the tap of the secondary winding of the transformer module 3 is connected to the output end of the transformer module 3, so as to increase the primary-secondary turns ratio of the transformer module 3, so that the current primary-secondary turns ratio of the transformer module 3 adapts to the current low output voltage state.

[0045] In this example, the detection control module 2 controls the switching switch K1 in the switching module 1 to switch the connection between the first contact B or the second contact C according to the output voltage of the transformer module 3, so as to change the primary-to-secondary turns ratio of the transformer module 3, so that the current primary-to-secondary turns ratio of the transformer module 3 adapts to the current circuit output state and improves work efficiency.

[0046] In one embodiment, the detection control module 2 includes a detection unit 21 and a control unit 22; the first end of the detection unit 21 is connected to the output end of the transformer module 3, and the second end of the detection unit 21 is connected to the first end of the control unit 22, and is used to output a control voltage to the control unit 22 according to the output end voltage of the transformer module 3; the second end of the control unit 22 is connected to the switching switch K1, and is used to control the second end of the switching switch K1 to switch the connection to the first contact B or the second contact according to the control voltage.

[0047] As an example, the detection control module 2 includes a detection unit 21 and a control unit 22. The first end of the detection unit 21 can be connected to the output end of the transformer module 3 through a secondary rectifier and filter module 5 to obtain the output end voltage of the transformer module 3. The second end of the detection unit 21 is connected to the first end of the control unit 22, and the second end of the control unit 22 is connected to the switching switch K1.

[0048] During the operation of the circuit, the detection unit 21 obtains the output terminal voltage of the transformer module 3 in real time, and outputs a control voltage to the control unit 22 according to the output terminal voltage, and the control unit 22 outputs a switching signal to the switch K1 according to the control voltage. Specifically, when the detection unit 21 detects that the output terminal voltage of the transformer module 3 is greater than the preset voltage, the first control voltage is output to the control unit 22, and the control unit 22 outputs a first switching signal to the switch K1 according to the first control voltage, so that the switch K1 switches to connect to the first contact B under the action of the first switching signal; when the detection unit 21 detects that the output terminal voltage of the transformer module 3 is not greater than the preset voltage, the second control voltage is output to the control unit 22, and the control unit 22 outputs a second switching signal to the switch K1 according to the second control voltage, so that the switch K1 switches to connect to the second contact C under the action of the second switching signal.

[0049] In one embodiment, the detection unit 21 includes a sampling unit 211, a reference voltage generating unit 212 and an operational amplifier U1; the input end of the sampling unit 211 is connected to the output end of the transformer module 3, the output end of the sampling unit 211 is connected to the inverting input end of the operational amplifier U1, and the sampling voltage is output to the operational amplifier U1; the input end of the reference voltage generating unit 212 is connected to the output end of the transformer module 3, the output end of the reference voltage generating unit 212 is connected to the non-inverting input end of the operational amplifier U1, and the reference voltage is output to the operational amplifier U1; the output end of the operational amplifier U1 is connected to the control unit 22, and is used to output a control voltage to the control unit 22 according to the size of the sampling voltage and the reference voltage.

[0050] As an example, the detection unit 21 includes a sampling unit 211, a reference voltage generating unit 212 and an operational amplifier U1. The input ends of the sampling unit 211 and the reference voltage generating unit 212 can be connected to the output end of the transformer module 3 through the same secondary rectifier filter module 5, the output end of the sampling unit 211 is connected to the inverting input end of the operational amplifier U1, the output end of the reference voltage generating unit 212 is connected to the non-inverting input end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected to the control unit 22.

[0051] During the circuit operation, the sampling unit 211 samples the output voltage of the transformer module 3, obtains the sampled voltage, and outputs it to the inverting input terminal of the operational amplifier U1. The output voltage of the transformer module 3 provides a voltage source for the reference voltage generating unit 212. The reference voltage generating unit 212 generates a reference voltage with a fixed voltage value and outputs it to the non-inverting input terminal of the operational amplifier U1. The operational amplifier U1 compares the sampled voltage with the reference voltage and outputs the corresponding control voltage to the control unit 22. Specifically, when the sampled voltage is greater than the reference voltage, it means that the output voltage currently output by the transformer module 3 is greater than the preset voltage, and the operational amplifier U1 outputs the first control voltage to the control unit 22; when the sampled voltage is not greater than the reference voltage, it means that the output voltage currently output by the transformer module 3 is not greater than the preset voltage, and the operational amplifier U1 outputs the second control voltage to the control unit 22.

[0052] In one embodiment, the sampling unit 211 includes a first resistor R1 and a second resistor R2; the first resistor R1 and the second resistor R2 are connected in series between the output end of the transformer module 3 and the ground; the inverting input end of the operational amplifier U1 is connected to the connection node between the first resistor R1 and the second resistor R2.

[0053] As an example, the sampling unit 211 includes a first resistor R1 and a second resistor R2, the first end of the first resistor R1 can be connected to the output end of the transformer module 3 through a secondary rectifier filter module 5, the second end of the first resistor R1 is connected to the first end of the second resistor R2, and the second end of the second resistor R2 is grounded. The inverting input end of the operational amplifier U1 is connected to the connection node between the first resistor R1 and the second resistor R2. The first resistor R1 and the second resistor R2 divide the output voltage of the transformer module 3, and the sampling voltage input to the inverting input end of the operational amplifier U1 is the same as the voltage across the second resistor R2.

[0054] In one embodiment, the reference voltage generating unit 212 includes a third resistor R3 and a voltage stabilizing unit; the third resistor R3 and the voltage stabilizing unit are connected in series between the output end of the transformer module 3 and the ground; the inverting input end of the operational amplifier U1 is connected to the connection node between the third resistor R3 and the voltage stabilizing unit.

[0055] As an example, the reference voltage generating unit 212 includes a third resistor R3 and a voltage stabilizing unit, wherein the first end of the third resistor R3 is connected to the output end of the transformer module 3 through a secondary rectifier filter module 5, the second end of the third resistor R3 is connected to the first end of the voltage stabilizing unit, the second end of the voltage stabilizing unit is grounded, and the inverting input end of the operational amplifier U1 is connected to the connection node between the third resistor R3 and the voltage stabilizing unit. The third resistor R3 plays a voltage dividing role, and the voltage across the voltage stabilizing unit does not change with the voltage at the output end of the transformer module 3. The voltage input to the in-phase input end of the operational amplifier U1 is the same as the voltage across the voltage stabilizing unit, which is the reference voltage.

[0056] In one embodiment, the voltage stabilizing unit includes a voltage stabilizing tube U2; a first end and a second end of the voltage stabilizing tube U2 are connected to a third resistor R3, and a third end of the voltage stabilizing tube U2 is grounded.

[0057] As an example, the voltage stabilizing unit includes a voltage stabilizing tube U2, which can be a TL431 type three-terminal adjustable shunt regulator. The first end of the voltage stabilizing tube U2 is the cathode end of TL431, the second end of the voltage stabilizing tube U2 is the reference end of TL431, and the third end of the voltage stabilizing tube U2 is the anode end of TL431. The cathode end and the reference end of TL431 are connected to the third resistor R3, and the anode end of TL431 is grounded. The cathode end and the anode end voltage of TL431 do not change with the output end voltage of the transformer module 3, and the voltage input to the in-phase input end of the operational amplifier U1 is the same as the cathode end and the anode end voltage of TL431, that is, the reference voltage.

[0058] In one embodiment, the control unit 22 includes a switch tube Q1; the first end of the switch tube Q1 is connected to the output end of the transformer module 3, the second end of the switch tube Q1 is connected to the detection unit 21, and the third end of the switch tube Q1 is connected to the switching switch K1, which is used to output a switching signal to the switching switch K1 according to the control voltage.

[0059] As an example, the control unit 22 includes a switch tube Q1, which may be an NPN transistor, wherein the first end of the switch tube Q1 is the collector of the transistor, the second end of the switch tube Q1 is the base of the transistor, and the third end of the switch tube Q1 is the emitter of the transistor. The collector of the transistor is connected to the output end of the transformer module 3, the base of the transistor is connected to the detection unit 21, and the emitter of the transistor is connected to the switching switch K1.

[0060] During the operation of the circuit, the transistor can be turned on or off under the control of the control voltage, thereby controlling the switching switch K1 to switch the connection between the first contact B and the second contact C. Specifically, when the sampling voltage is greater than the reference voltage, it means that the output terminal voltage currently output by the transformer module 3 is greater than the preset voltage, and the operational amplifier U1 outputs a first control voltage to the base of the transistor, and the first control voltage can be a low-level voltage. At this time, the transistor is in an off state, so that the switching switch K1 is connected to the first contact B; when the sampling voltage is not greater than the reference voltage, it means that the output terminal voltage currently output by the transformer module 3 is not greater than the preset voltage, and the operational amplifier U1 outputs a second control voltage to the control unit 22, and the second control voltage can be a high-level voltage. At this time, the transistor is in an on state, so that the switching switch K1 is connected to the second contact C.

[0061] In one embodiment, the switching switch K1 includes an armature and an electromagnetic mechanism; the first end of the armature is connected to the fixed end A, and the second end of the armature is switched to connect to the first contact B or the second contact C; the electromagnetic mechanism is connected to the output end of the detection control module 2, and is used to control the second end of the armature to switch to connect to the first contact B or the second contact C according to the switching signal.

[0062] As an example, the switching switch K1 includes an armature and an electromagnetic mechanism. The electromagnetic mechanism is connected to the output end of the detection control module 2 and can be powered on under the control of a switching signal to generate an adsorption force on the armature. The first end of the armature is connected to the fixed end A, and the second end of the armature is connected to the first contact B under normal conditions. If the electromagnetic mechanism is powered on to generate an adsorption force to adsorb the armature, the armature can switch from being connected to the first contact B to being connected to the second contact C. After the electromagnetic mechanism loses power and has no adsorption force, the second end of the armature can be restored from being connected to the second contact C to being connected to the first contact B. Specifically, when the sampling voltage is greater than the reference voltage, it means that the output terminal voltage currently output by the transformer module 3 is greater than the preset voltage, and the operational amplifier U1 outputs a first control voltage to the base of the transistor, and the first control voltage can be a low-level voltage. At this time, the transistor is in the off state, the electromagnetic mechanism loses power and has no adsorption force, and the second end of the armature is connected to the first contact B; when the sampling voltage is not greater than the reference voltage, it means that the output terminal voltage currently output by the transformer module 3 is not greater than the preset voltage, and the operational amplifier U1 outputs a second control voltage to the control unit 22, and the second control voltage can be a high-level voltage. At this time, the transistor is in the on state, and the electromagnetic mechanism is powered on to generate adsorption force on the armature, so that the second end of the armature is switched to be connected to the second contact C.

[0063] The embodiment of the utility model also provides a switching power supply circuit, including a primary rectifier and filter module 4, a transformer module 3, a secondary rectifier and filter module 5 and the transformer switching circuit in the above embodiment; the input end of the primary rectifier and filter module 4 is used to connect to the mains circuit, the output end of the primary rectifier and filter module 4 is connected to the input end of the transformer module 3, the output end of the transformer module 3 is connected to the input end of the secondary rectifier and filter module 5, and the output end of the secondary rectifier and filter module 5 is used to connect to an external load; the input end of the detection control module 2 is connected to the output end of the transformer module 3 through the secondary rectifier and filter module 5.

[0064] As an example, it includes a primary rectifier filter module 4, a transformer module 3, a secondary rectifier filter module 5 and the transformer switching circuit in the above example. The input end of the primary rectifier filter module 4 is used to connect to the mains circuit, the output end of the primary rectifier filter module 4 is connected to the input end of the transformer module 3, the output end of the transformer module 3 is connected to the input end of the secondary rectifier filter module 5, and the output end of the secondary rectifier filter module 5 is used to connect to an external load and output a power supply voltage to the external load. In the transformer switching circuit, the input end of the detection control module 2 is connected to the output end of the transformer module 3 through the secondary rectifier filter module 5, the output end voltage of the transformer module 3 is obtained, and according to the output end voltage, a switching signal is output to the switching switch K1, so that the switching switch K1 switches to connect the first contact B or the second contact C under the action of the switching signal.

[0065] In this example, the detection control module 2 in the transformer switching circuit can control the switching switch K1 in the switching module 1 to switch the connection between the first contact B or the second contact C according to the output voltage of the transformer module 3, so as to change the primary-to-secondary turns ratio of the transformer module 3, so that the current primary-to-secondary turns ratio of the transformer module 3 adapts to the output voltage state of the current switching power supply circuit, thereby improving the working efficiency of the switching power supply circuit.

[0066] An embodiment of the utility model further provides a charger, comprising the switching power supply circuit in the above embodiment.

[0067] As an example, the charger includes the switching power supply circuit in the above example, in which the detection control module 2 in the transformer switching circuit can control the switching switch K1 in the switching module 1 to switch the connection between the first contact B or the second contact C according to the output voltage of the transformer module 3, so as to change the primary-to-secondary turns ratio of the transformer module 3, so that the current primary-to-secondary turns ratio of the transformer module 3 adapts to the output voltage state of the current switching power supply circuit, thereby improving the working efficiency of the switching power supply circuit.

[0068] 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 transformer switching circuit, characterized in that: It includes a switching module and a detection control module; The switching module includes a fixed end, a first contact, a second contact and a switching switch, wherein the fixed end is used to be connected to the output end of the transformer module, the first contact is used to be connected to the output terminal of the secondary winding of the transformer module, the second contact is used to be connected to the tap of the secondary winding of the transformer module, the first end of the switching switch is connected to the fixed end, and the second end of the switching switch is switched to be connected to the first contact or the second contact; The input end of the detection control module is connected to the output end of the transformer module, and the output end of the detection control module is connected to the switching switch, which is used to output a switching signal according to the output end voltage of the transformer module to control the second end of the switching switch to switch the connection to the first contact or the second contact.

2. The transformer switching circuit according to claim 1, characterized in that: The detection control module includes a detection unit and a control unit; The first end of the detection unit is connected to the output end of the transformer module, and the second end of the detection unit is connected to the first end of the control unit, and is used to output a control voltage to the control unit according to the output end voltage of the transformer module; The second end of the control unit is connected to the switch, and is used to output a switching signal to the switch according to the control voltage.

3. The transformer switching circuit according to claim 2, characterized in that: The detection unit includes a sampling unit, a reference voltage generating unit and an operational amplifier; The input end of the sampling unit is connected to the output end of the transformer module, and the output end of the sampling unit is connected to the inverting input end of the operational amplifier to output the sampling voltage to the operational amplifier; The input end of the reference voltage generating unit is connected to the output end of the transformer module, and the output end of the reference voltage generating unit is connected to the in-phase input end of the operational amplifier to output the reference voltage to the operational amplifier; The output end of the operational amplifier is connected to the control unit and is used to output a control voltage to the control unit according to the magnitudes of the sampling voltage and the reference voltage.

4. The transformer switching circuit according to claim 3, characterized in that: The sampling unit includes a first resistor and a second resistor; The first resistor and the second resistor are connected in series between the output terminal of the transformer module and the ground; The inverting input terminal of the operational amplifier is connected to a connection node between the first resistor and the second resistor.

5. The transformer switching circuit according to claim 3, characterized in that: The reference voltage generating unit includes a third resistor and a voltage stabilizing unit; The third resistor and the voltage stabilizing unit are connected in series between the output end of the transformer module and the ground; The inverting input terminal of the operational amplifier is connected to a connection node between the third resistor and the voltage stabilizing unit.

6. The transformer switching circuit according to claim 5, characterized in that: The voltage stabilizing unit includes a voltage stabilizing tube; The first and second ends of the voltage regulator tube are connected to the third resistor, and the third end of the voltage regulator tube is grounded.

7. The transformer switching circuit according to claim 2, characterized in that: The control unit includes a switch tube; The first end of the switch tube is connected to the output end of the transformer module, the second end of the switch tube is connected to the detection unit, and the third end of the switch tube is connected to the switching switch, and is used to output a switching signal to the switching switch according to the control voltage.

8. The transformer switching circuit according to claim 1, characterized in that: The switching switch comprises an armature and an electromagnetic mechanism; The first end of the armature is connected to the fixed end, and the second end of the armature is switchably connected to the first contact or the second contact; The electromagnetic mechanism is connected to the output end of the detection control module, and is used to control the second end of the armature to switch and connect to the first contact or the second contact according to the switching signal.

9. A switching power supply circuit, characterized in that: It comprises a primary rectifier and filter module, a transformer module, a secondary rectifier and filter module and a transformer switching circuit as claimed in any one of claims 1 to 8; The input end of the primary rectifier and filter module is used to connect to the mains circuit, the output end of the primary rectifier and filter module is connected to the input end of the transformer module, the output end of the transformer module is connected to the input end of the secondary rectifier and filter module, and the output end of the secondary rectifier and filter module is used to connect to an external load and output a supply voltage to the external load; The input end of the detection control module is connected to the output end of the transformer module through the secondary rectification and filtering module.

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

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