Voltage switching circuit

Abstract

The present application relates to the technical field of electric power systems. Disclosed is a voltage switching circuit. The voltage switching circuit comprises a voltage input module, a step-down module, a voltage sampling module, a first voltage comparison control module, a second voltage comparison control module, a switching module, and a transformer. After rectification and multiple step-downs are performed on an alternating-current voltage, a power supply voltage, a first reference voltage, a second reference voltage, a first voltage and a second voltage are obtained; the first voltage comparison control module outputs a first control signal on the basis of a comparison result between the second voltage and the second reference voltage; the second voltage comparison control module outputs a second control signal on the basis of the first control signal, and a comparison result between the second voltage and the first reference voltage; and the switching module controls, on the basis of the second control signal and by means of a relay, the transformer to match the magnitude of the input alternating-current voltage. The voltage switching circuit simplifies the operation process of controlling a transformer to perform voltage switching on different alternating-current voltages, and is safe and reliable.

Description

A voltage switching circuit

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 2024111728961, filed on August 26, 2024, entitled "A Voltage Switching Circuit", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of power system technology, and in particular to a voltage switching circuit. Background Technology

[0004] One of the core functions of a transformer is to transform voltage levels. After the primary winding of the transformer is connected to an AC power source of a certain voltage level, the voltage can be reduced to a lower voltage suitable for the user by selecting the connection state of the primary winding. Normally, switching between different taps of a transformer is done manually by using a toggle switch. The disadvantages of a manual toggle switch are: inconvenience, requiring the user to know the input voltage and the switch position to switch between low and high voltage; poor efficiency when the input voltage is low; and the risk of burning out the transformer or the load equipment when manually switching taps.

[0005] Application content

[0006] In view of this, the present application provides a voltage switching circuit that enables the voltage converter to switch between different voltages according to the magnitude of the input AC voltage, thereby solving the problems of inconvenience and low safety of manual operation.

[0007] In a first aspect, embodiments of this application provide a voltage switching circuit, including: a voltage input module, a step-down module, a voltage sampling module, a first voltage comparison control module, a second voltage comparison control module, and a switching module, wherein the switching module is configured to connect to a transformer;

[0008] The voltage input module is configured to receive an AC voltage and rectify the AC voltage to obtain a DC voltage;

[0009] The step-down module is configured to step down the DC voltage output by the voltage input module to obtain the circuit power supply voltage, and is also configured to step down the power supply voltage to obtain a first reference voltage.

[0010] The voltage sampling module is configured to sample the DC voltage and then divide it to obtain a first voltage;

[0011] The first voltage comparison control module and the second voltage comparison control module are respectively configured to step down the first voltage to obtain the second voltage;

[0012] The first voltage comparison control module is further configured to step down the first reference voltage to obtain a second reference voltage, and output a first control signal based on the comparison result between the second voltage and the second reference voltage;

[0013] The second voltage comparison control module is further configured to output a second control signal based on the level state of the first control signal and the comparison result between the second voltage and the first reference voltage;

[0014] The switching module includes a relay, and the switching module is configured to switch the connection state of the primary winding of the transformer according to the level state of the second control signal, so as to match the magnitude of the AC voltage input to the transformer.

[0015] Optionally, the first voltage comparison control module includes a first switching transistor;

[0016] The first voltage comparison control module is configured to turn on the first switch when the second voltage is greater than the second reference voltage, so as to output the first control signal in the first level state;

[0017] The first voltage comparison control module is further configured to turn off the first switch when the second voltage is less than the second reference voltage, so as to output the first control signal in the second level state;

[0018] The first voltage comparison control module is further configured to maintain the first switch in its current state when the second voltage is equal to the second reference voltage, so as to continuously output the first control signal in the first level state or the second level state.

[0019] Optionally, the second voltage comparison control module includes a second switching transistor;

[0020] The second voltage comparison control module is configured to turn off the second switch when the first switch is in the on state, or when the first switch is in the off state and the second voltage is greater than the first reference voltage, so as to output the second control signal in the first level state.

[0021] The second voltage comparison control module is further configured to turn on the second switch when the first switch is in the off state and the second voltage is less than the first reference voltage, so as to output the second control signal in the second level state.

[0022] The second voltage comparison control module is further configured to maintain the second switch in its current state when the first switch is in the off state and the second voltage is equal to the first reference voltage, so as to continuously output the second control signal of the first level state or the second level state.

[0023] Optionally, the relay includes a first common contact, a second common contact, a first normally open contact, a second normally open contact, a third normally open contact, and a fourth normally open contact, wherein the first normally open contact is connected to the second normally open contact;

[0024] When the first common contact is connected to the first normally open contact and the second common contact is connected to the second normally open contact, the transformer is in the first connection state;

[0025] When the first common contact is connected to the third normally open contact and the second common contact is connected to the fourth normally open contact, the transformer is in a second connection state.

[0026] Optionally, it also includes the transformer, wherein the transformer includes a first primary winding, a second primary winding, and a secondary winding;

[0027] The first end of the first primary winding is connected to an AC wire, which is connected to the fourth normally open contact. The second end of the first primary winding is connected to the first common contact. The first end of the second primary winding is connected to an AC neutral wire, which is connected to the third normally open contact. The second end of the second primary winding is connected to the second common contact.

[0028] Optionally, the switching module is further configured to control the relay to be in a normally open state according to the second control signal of the first level state, so that the first primary winding and the second primary winding of the transformer are in series to match the first AC voltage.

[0029] The switching module is further configured to control the relay to be in a closed state according to the second control signal of the second level state, so that the first primary winding and the second primary winding of the transformer are connected in parallel to match the second AC voltage, wherein the first AC voltage is greater than the second AC voltage.

[0030] Optionally, both the first voltage comparison control module and the second voltage comparison control module include a first diode, a first voltage divider resistor, and a second voltage divider resistor; the first voltage comparison control module further includes a first comparator, a first transistor, and a second diode, and the second voltage comparison control module further includes a second comparator and a second transistor;

[0031] The cathode of the first diode is connected to the non-inverting input of the first comparator and the inverting input of the second comparator. The inverting input of the first comparator is connected to the cathode of the second diode. The anode of the second diode is connected to the buck module. The non-inverting input of the second comparator is connected to the buck module.

[0032] The output terminals of the first comparator and the second comparator are both connected to the first terminal of the first voltage divider resistor. The second terminal of the first voltage divider resistor is connected to the first terminal of the second voltage divider resistor, the base of the first transistor, and the base of the second transistor, respectively. The negative power supply terminals of the first comparator, the second comparator, the second terminal of the second voltage divider resistor, the emitter of the first transistor, and the emitter of the second transistor are all grounded. The positive power supply terminals of the first comparator and the second comparator are both connected to the buck module.

[0033] The collector of the first transistor is connected to the base of the second transistor, and the collector of the second transistor is connected to the switching module.

[0034] Optionally, the voltage input module includes an AC power line, an AC neutral wire, a fuse, a varistor, and a bridge rectifier;

[0035] The first end of the AC wire is connected to the positive terminal of the AC power supply, and the first end of the AC neutral wire is connected to the negative terminal of the AC power supply.

[0036] The first end of the fuse is connected to the second end of the AC wire, the second end of the fuse is connected to the first end of the varistor, and the second end of the varistor is connected to the second end of the AC neutral wire.

[0037] The positive input terminal of the bridge rectifier is connected to the series node of the fuse and the varistor, the negative input terminal of the bridge rectifier is connected to the second end of the AC neutral line, the positive output terminal of the bridge rectifier is connected to the step-down module and the voltage sampling module, and the negative output terminal of the bridge rectifier is grounded.

[0038] Optionally, the voltage sampling module includes a voltage divider unit and a voltage follower unit;

[0039] The voltage divider unit includes a third voltage divider resistor, a fourth voltage divider resistor, a Zener diode, and a first capacitor; the voltage follower unit includes a follower.

[0040] The first end of the third voltage divider resistor is connected to the output end of the voltage input module, the second end of the third voltage divider resistor is connected to the first end of the fourth voltage divider resistor, the second end of the fourth voltage divider resistor is grounded, and the Zener diode and the first capacitor are connected in parallel with the fourth voltage divider resistor respectively.

[0041] The non-inverting input of the follower is connected to the series node of the third and fourth voltage divider resistors, the output of the follower is connected to the first voltage comparison control module and the second voltage comparison control module, and the inverting input of the follower is connected to the first voltage comparison control module.

[0042] Optionally, the step-down module includes a primary step-down unit and a secondary step-down unit;

[0043] The first-stage step-down unit includes a DC-DC converter chip and corresponding peripheral devices, and the second-stage step-down unit includes a fifth voltage divider resistor and a reference voltage chip.

[0044] The first end of the fifth voltage divider resistor is connected to the first-stage step-down unit, the second end of the fifth voltage divider resistor is connected to the input pin of the reference voltage chip, the output pin of the reference voltage chip is connected to the first voltage comparison control module and the second voltage comparison control module, and the ground pin of the reference voltage chip is grounded.

[0045] The embodiments of this application have the following beneficial effects:

[0046] A voltage switching circuit according to this embodiment includes: a voltage input module, a step-down module, a voltage sampling module, a first voltage comparison control module, a second voltage comparison control module, and a switching module. The switching module is configured to connect to a transformer. After rectification and multiple step-down operations, the AC voltage is used to obtain a supply voltage, a first reference voltage, a second reference voltage, a first voltage, and a second voltage. The first voltage comparison control module outputs a first control signal based on the comparison result between the second voltage and the second reference voltage. The second voltage comparison control module outputs a second control signal based on the first control signal and the comparison result between the second voltage and the first reference voltage. The switching module, based on the second control signal, controls the transformer via a relay to match the magnitude of the input AC voltage. Based on the above scheme, this voltage switching circuit uses dual-channel control relays to engage and disengage normally open contacts according to different input AC voltage magnitudes, thereby enabling the transformer to switch voltages for different input AC voltages. This method is simple to operate and protects both the transformer and the load equipment. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 shows a schematic diagram of a voltage switching circuit according to an embodiment of this application;

[0049] Figure 2 shows a circuit diagram of a switching module according to an embodiment of this application;

[0050] Figure 3 shows a circuit diagram of a first voltage comparison control module and a second voltage comparison control module according to an embodiment of this application;

[0051] Figure 4 shows a circuit diagram of a voltage input module, a voltage sampling module, and a buck module according to an embodiment of this application.

[0052] Explanation of reference numerals: 100 - Voltage switching circuit; 110 - Voltage input module; 120 - Step-down module; 130 - Voltage sampling module; 140 - First voltage comparison control module; 150 - Second voltage comparison control module; 160 - Switching module; 170 - Transformer. Detailed Implementation

[0053] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0054] The components of the embodiments of this application described and illustrated in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0055] In the following text, the terms "comprising," "having," and their cognates, which may be used in various embodiments of this application, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more combinations thereof. Furthermore, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0056] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. Terms (such as those defined in commonly used dictionaries) shall be interpreted as having the same meaning as in their contextual meaning in the relevant technical field and shall not be construed as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0057] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0058] Figure 1 shows a schematic diagram of a voltage switching circuit according to an embodiment of this application. Exemplarily, the voltage switching circuit 100 includes a voltage input module 110, a step-down module 120, a voltage sampling module 130, a first voltage comparison control module 140, a second voltage comparison control module 150, and a switching module 160. The switching module 160 is configured to connect to a transformer 170. Specifically, the voltage input module 110, step-down module 120, first voltage comparison control module 140, second voltage comparison control module 150, and switching module 160 are connected sequentially to rectify and step down the input AC voltage, providing the required voltage to the first voltage comparison control module 140, second voltage comparison control module 150, and switching module 160. The voltage input module 110, voltage sampling module 130, first voltage comparison control module 140, second voltage comparison control module 150 and switching module 160 are connected in sequence to rectify and divide the input AC voltage and compare it with the corresponding reference voltage to output the corresponding control signal to control the transformer 170 to switch between different input AC voltages.

[0059] In this embodiment, the voltage input module 110 is configured to receive an AC voltage and rectify the AC voltage to obtain a DC voltage; the step-down module 120 is configured to step down the DC voltage output by the voltage input module 110 to obtain a circuit power supply voltage V1, and is also configured to step down the circuit power supply voltage V1 to obtain a first reference voltage V2; wherein, the circuit power supply voltage V1 is configured to supply power to the first voltage comparison control module 140, the second voltage comparison control module 150, and the switching module 160; the voltage sampling module 130 is configured to sample the input voltage and then divide it to obtain the first voltage; the first voltage comparison control module 140 and the second voltage comparison control module 150 are respectively configured to... The first voltage is stepped down in pairs to obtain the second voltage; the first voltage comparison control module 140 is also configured to step down the first reference voltage V2 to obtain the second reference voltage, and output a first control signal according to the comparison result of the second voltage and the second reference voltage; the second voltage comparison control module is also configured to output a second control signal according to the level state of the first control signal and the comparison result of the second voltage and the first reference voltage V2; the switching module 160 includes a relay K1, and the switching module 160 is configured to switch the connection state of the primary winding of the transformer 170 through the relay K1 according to the level state of the second control signal, so as to match the magnitude of the AC voltage input to the transformer 170.

[0060] As an example, the first voltage comparison control module 140 is configured to compare the magnitudes of the second voltage and the second reference voltage, turn the first switch on or off, and output first control signals of different level states.

[0061] For example, in one embodiment, the first voltage comparison control module 140 includes a first switching transistor; the first voltage comparison control module 140 is configured to turn on the first switching transistor when the second voltage is greater than the second reference voltage, so as to output a first control signal in a first level state; the first voltage comparison control module 140 is further configured to turn off the first switching transistor when the second voltage is less than the second reference voltage, so as to output a first control signal in a second level state; the first voltage comparison control module 140 is further configured to maintain the first switching transistor in its current state when the second voltage is equal to the second reference voltage, so as to continuously output a first control signal in either the first level state or the second level state.

[0062] As an example, the second voltage comparison control module 150 is configured to turn on or off via a second switch based on the level state of the first control signal and by comparing the magnitudes of the second voltage and the second reference voltage, so as to output a second control signal with different level states.

[0063] For example, in one embodiment, the second voltage comparison control module 150 includes a second switching transistor; the second voltage comparison control module 150 is configured to turn off the second switching transistor when the first switching transistor is in an on state, or when the first switching transistor is in an off state and the second voltage is greater than the first reference voltage V2, so as to output a second control signal in a first level state; the second voltage comparison control module 150 is further configured to turn on the second switching transistor when the first switching transistor is in an off state and the second voltage is less than the first reference voltage V2, so as to output a second control signal in a second level state; the second voltage comparison control module 150 is further configured to maintain the second switching transistor in the current state when the first switching transistor is in an off state and the second voltage is equal to the first reference voltage V2, so as to continuously output a second control signal in a first level state or a second level state.

[0064] To better understand the voltage switching circuit 100, the various components of the voltage switching circuit 100 will be described in detail below.

[0065] As shown in Figure 2, in one embodiment, the switching module 160 includes a relay K1, which includes a first common contact a1, a second common contact a2, a first normally open contact b1, a second normally open contact b2, a third normally open contact b3, and a fourth normally open contact b4. The first normally open contact b1 is connected to the second normally open contact b2. When the first common contact a1 is connected to the first normally open contact b1 and the second common contact a2 is connected to the second normally open contact b2, the transformer 170 is in a first connection state. When the first common contact a1 is connected to the third normally open contact b3 and the second common contact a2 is connected to the fourth normally open contact b4, the transformer 170 is in a second connection state.

[0066] Optionally, the relay K1 also includes a trigger coil. When current is applied, the trigger coil generates a certain electromagnetic force, thereby attracting or pushing the first common contact a1 and the first normally open contact b1 or the third normally open contact b3, and the second common contact a2 and the second normally open contact b2 or the fourth normally open contact b4 to perform switching operations. The switching module 160 also includes a third diode D3. The cathode of the third diode D3 is connected to the step-down module 120, and the anode of the third diode D3 is connected to the second voltage comparison control module 150. The trigger coil is connected in parallel with the third diode D3.

[0067] As shown in Figure 2, in one embodiment, the voltage switching circuit 100 further includes a transformer 170, wherein the transformer 170 includes a first primary winding c1, a second primary winding c2, and a secondary winding c3; the first end of the first primary winding c1 is connected to an AC wire AC-L, the AC wire AC-L is connected to a fourth normally open contact b4, the second end of the first primary winding c1 is connected to a first common contact a1, the first end of the second primary winding c1 is connected to an AC neutral wire AC-N, the AC neutral wire AC-N is connected to a third normally open contact b3, and the second end of the second primary winding c2 is connected to a second common contact a2.

[0068] In this embodiment, the switching module 160 is further configured to control the relay K1 to be in a normally open state according to the second control signal of the first level state, so that the first primary winding c1 and the second primary winding c2 of the transformer 170 are in series to match the first AC voltage; the switching module 160 is further configured to control the relay K1 to be in a closed state according to the second control signal of the second level state, so that the first primary winding c1 and the second primary winding c2 of the transformer 170 are in parallel to match the second AC voltage, wherein the first AC voltage is greater than the second AC voltage.

[0069] Optionally, the range of the first AC voltage can be (170V-240V), and the range of the second AC voltage can be [100V-170V]. In some embodiments, the voltage regulator 170 further includes a filter resistor RL, which is connected in parallel with the secondary winding c3.

[0070] As shown in Figure 3, in one embodiment, both the first voltage comparison control module 140 and the second voltage comparison control module 150 include a first diode D1, a first voltage divider resistor R1, and a second voltage divider resistor R2. The first voltage comparison control module 140 also includes a first comparator U2-A, a first transistor Q1, and a second diode D2. The second voltage comparison control module 150 also includes a second comparator U1-A and a second transistor Q2. The cathode of the first diode D1 is connected to the non-inverting input terminal of the first comparator U2-A and the inverting input terminal of the second comparator U2-A. The inverting input terminal of the first comparator U2-A is connected to the cathode of the second diode Q2. The anode of the second diode Q2 is connected to the step-down module 120. The non-inverting input terminal of the second comparator U1-A is connected to the cathode of the second diode Q2. The input terminals are connected to the step-down module 120; the output terminals of the first comparator U2-A and the second comparator U1-A are both connected to the first terminal of the first voltage divider resistor R1, the second terminal of the first voltage divider resistor R1 is connected to the first terminal of the second voltage divider resistor R2, the base of the first transistor Q1 and the base of the second transistor Q2, respectively; the negative power supply terminals of the first comparator U2-A, the negative power supply terminal of the second comparator U1-A, the second terminal of the second voltage divider resistor R2, the emitter of the first transistor Q1 and the emitter of the second transistor Q2 are all grounded; the positive power supply terminals of the first comparator U2-A and the second comparator U1-A are both connected to the step-down module; the collector of the first transistor Q1 is connected to the base of the second transistor Q2, and the collector of the second transistor Q2 is connected to the switching module 160.

[0071] In this embodiment, the first comparator U2-A controls the first transistor Q1 to turn on or off by comparing the voltages at its non-inverting and inverting input terminals, so that the first voltage comparison control module 140 outputs first control signals of different levels to the second transistor Q2. The second transistor Q2 is configured to turn off according to the first control signal of the first level, so that the second voltage comparison control module 150 outputs a second control signal of the first level; the second transistor Q2 is also configured to turn on or off according to the first control signal of the second level and the comparison result of the voltages at the non-inverting and inverting input terminals by the second controller U1-A, so that the second voltage comparison control module 150 outputs second control signals of different levels to the switching module 160.

[0072] As shown in Figure 4, in one embodiment, the voltage input module 110 includes an AC power line AC-L, an AC neutral line AC-N, a fuse FUSE, a varistor RV, and a bridge rectifier BD. The first end of the AC power line AC-L is connected to the positive terminal of the AC power supply, and the first end of the AC neutral line AC-N is connected to the negative terminal of the AC power supply. The first end of the fuse FUSE is connected to the second end of the AC power line AC-L, the second end of the fuse FUSE is connected to the first end of the varistor RV, and the second end of the varistor RV is connected to the second end of the AC neutral line AC-N. The positive input terminal of the bridge rectifier BD is connected to the series connection node of the fuse FUSE and the varistor RV, the negative input terminal of the bridge rectifier BD is connected to the second end of the AC neutral line AC-N, the positive output terminal of the bridge rectifier BD is connected to the step-down module 120 and the voltage sampling module 130, and the negative output terminal of the bridge rectifier BD is grounded.

[0073] In this embodiment, the fuse FUSE is configured to protect the voltage switching circuit from damage caused by abnormal conditions such as current overload and short circuit; the varistor RV is configured to provide overvoltage protection and grounding protection for the voltage switching circuit, as well as to protect the voltage switching circuit from high-frequency electromagnetic interference; and the bridge rectifier BD is configured to convert the input AC voltage into DC voltage.

[0074] As shown in Figure 4, in one embodiment, the voltage sampling module 130 includes a voltage divider unit 131 and a voltage follower unit 132. The voltage divider unit 131 includes a third voltage divider resistor R3, a fourth voltage divider resistor R4, a Zener diode D6, and a first capacitor C1. The voltage follower unit 132 includes a follower U1-B. The first end of the third voltage divider resistor R3 is connected to the output terminal of the voltage input module 110, the second end of the third voltage divider resistor R3 is connected to the first end of the fourth voltage divider resistor R4, the second end of the fourth voltage divider resistor R4 is grounded, and the Zener diode D6 and the first capacitor C1 are connected in parallel with the fourth voltage divider resistor R4. The positive input terminal of the follower U1-B is connected to the series node of the third voltage divider resistor R3 and the fourth voltage divider resistor R4, the output terminal of the follower U1-B is connected to the first voltage comparison control module 140 and the second voltage comparison control module 150, and the negative input terminal of the follower U1-B is connected to the first voltage comparison control module 140.

[0075] In this embodiment, the Zener diode D6 is configured to protect the input voltage of the follower U1-B from exceeding its rated voltage. Optionally, an operational amplifier can be used as the follower U1-B to achieve a one-to-one correspondence between the input voltage and the output voltage, i.e., the output voltage follows the input voltage.

[0076] As shown in Figure 4, in one embodiment, the step-down module 120 includes a first-stage step-down unit 121 and a second-stage step-down unit 122. The first-stage step-down unit 121 includes a DC-DC converter chip U3 and corresponding peripheral devices. The second-stage step-down unit 122 includes a fifth voltage divider resistor R5 and a reference voltage chip U4. The first end of the fifth voltage divider resistor R5 is connected to the first-stage step-down unit 121, and the second end of the fifth voltage divider resistor R5 is connected to the input pin of the reference voltage chip U4. The output pin of the reference voltage chip U4 is connected to the first voltage comparison control module 140 and the second voltage comparison control module 150. The ground pin of the reference voltage chip U4 is grounded.

[0077] Optionally, the peripheral components include a filter capacitor C5, a DC-DC converter chip U3, a sixth voltage divider resistor R6, a seventh voltage divider resistor R7, a fourth diode D4, a fifth diode D5, an inductor L1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4. The switching pin of DC-DC converter chip U3 is connected to the positive output terminal of bridge rectifier DB. The power supply voltage pin of DC-DC converter chip U3 is connected to the first terminal of the second capacitor C2 and the cathode of the fourth diode D4. The second terminal of the second capacitor C2 is connected to the series node of inductor L1 and sixth voltage divider resistor R6. The anode of the fourth diode D4 is connected to the first parallel node of the third capacitor C3, the fourth capacitor C4 and the seventh voltage divider resistor R7. The current sampling pin of DC-DC converter chip is configured to connect to the first terminal of the sixth voltage divider resistor R6. The second terminal of the sixth voltage divider resistor R6 is connected to the first terminal of inductor L1. The second terminal of inductor L1 is connected to the first parallel node. The ground pin of DC-DC converter chip U3 is connected to the cathode of the fourth diode D4. The anode of the fourth diode D4 is grounded. The second parallel node of the third capacitor C3, the fourth capacitor C4 and the seventh voltage divider resistor R7 is grounded. The first terminal of filter capacitor C5 is connected to the positive output terminal of bridge rectifier DB. The second terminal of filter capacitor C5 is grounded.

[0078] Optionally, assume the resistance of the first voltage divider resistor R1 is 1KΩ, the resistance of the second voltage divider resistor R2 is 10KΩ, the resistance of the third voltage divider resistor R3 is 3MΩ, the resistance of the fourth voltage divider resistor R4 is 31.6KΩ, and the voltage drop of the first diode D1 and the second diode D2 is 0.6V. When the input AC mains voltage is 220V, after rectification by the bridge rectifier BD and filtering by the filter capacitor C5, a relatively stable DC voltage of 310V is obtained. One path supplies power to the DC-DC converter chip U3. After being stepped down by the DC-DC converter chip U3, a stable +12V DC voltage is obtained, which supplies power to the comparator, relay K1, switching transistor, and reference voltage chip U4. Among them, the reference voltage chip U4 steps down the +12V circuit supply voltage V1 to obtain a first reference voltage V2 of 2.5V; the other path is sampled by voltage division by the third voltage divider resistor R3 and the fourth voltage divider resistor R4 to obtain a first voltage of 3.23V. The voltage is split into two paths by the first voltage follower U1-B. One path is stepped down by the first diode D1 to obtain a second voltage of 2.63V. This second voltage is compared with the first reference voltage V2 by the second comparator U1-A, and the second comparator U2-A outputs a low level. The other path is applied to the first comparator U2-A through the first diode D1. The first reference voltage V2 is stepped down by the second diode D2 to obtain a second reference voltage of 1.9V. This second voltage is compared with the second reference voltage, and the first comparator U2-A outputs a high level. The first transistor Q1 conducts, pulling down the base potential of the second transistor Q2, causing the second transistor Q2 to de-conduct. This prevents the control relay K1 from operating; at this time, relay K1 is in its first normally open state.

[0079] Optionally, when the input AC mains voltage is 169V, after rectification by the bridge rectifier BD and filtering by the filter capacitor C5, a relatively stable 239V DC voltage is obtained. One path supplies power to the DC-DC converter chip U3. After being stepped down by the DC-DC converter chip U3, a stable +12V DC voltage is obtained, which supplies power to the comparator, relay K1, switching transistor, and reference voltage chip U4. Among them, the reference voltage chip U4 steps down the +12V circuit supply voltage V1 to obtain a first reference voltage V2 of 2.5V. The other path is sampled by voltage division by the third voltage divider resistor R3 and the fourth voltage divider resistor R4 to obtain a first voltage of 2.49V. After passing through follower U1-B, the voltage is split into two paths. One path is stepped down by the first diode D1 to obtain a second voltage of 1.89V. This second voltage is compared with the first reference voltage V2 by the second comparator U1-A, and the second comparator U1-A outputs a high level. The other path is applied to the first comparator U2-A through the first diode D1. The first reference voltage V2 is stepped down by the second diode D2 to obtain a second reference voltage of 1.9V. This second voltage is compared with the second reference voltage, and the first comparator U2-A outputs a low level. The first transistor Q1 is cut off, and the second transistor Q2 is turned on, controlling the relay K1 to operate. At this time, the relay K1 is in the second normally open state.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Industrial applicability

[0081] Using the above scheme, the voltage switching circuit can switch the transformer to different input AC voltages by opening and closing the normally open contacts of the dual-channel control relays according to the magnitude of different input AC voltages. This makes the operation simple and protects the transformer and load equipment.

Claims

1. A voltage switching circuit, characterized in that, include: The system includes a voltage input module, a step-down module, a voltage sampling module, a first voltage comparison control module, a second voltage comparison control module, and a switching module, wherein the switching module is configured to connect to a transformer. The voltage input module is configured to receive an AC voltage and rectify the AC voltage to obtain a DC voltage; The step-down module is configured to step down the DC voltage output by the voltage input module to obtain the circuit power supply voltage, and is also configured to step down the power supply voltage to obtain a first reference voltage. The voltage sampling module is configured to sample the DC voltage and then divide it to obtain a first voltage; The first voltage comparison control module and the second voltage comparison control module are respectively configured to step down the first voltage to obtain the second voltage; The first voltage comparison control module is further configured to step down the first reference voltage to obtain a second reference voltage, and output a first control signal based on the comparison result between the second voltage and the second reference voltage; The second voltage comparison control module is further configured to output a second control signal based on the level state of the first control signal and the comparison result between the second voltage and the first reference voltage; The switching module includes a relay, and the switching module is configured to switch the connection state of the primary winding of the transformer according to the level state of the second control signal, so as to match the magnitude of the AC voltage input to the transformer.

2. The voltage switching circuit according to claim 1, characterized in that, The first voltage comparison control module includes a first switching transistor; The first voltage comparison control module is configured to turn on the first switch when the second voltage is greater than the second reference voltage, so as to output the first control signal in the first level state; The first voltage comparison control module is further configured to turn off the first switch when the second voltage is less than the second reference voltage, so as to output the first control signal in the second level state; The first voltage comparison control module is further configured to maintain the first switch in its current state when the second voltage is equal to the second reference voltage, so as to continuously output the first control signal in the first level state or the second level state.

3. The voltage switching circuit according to claim 2, characterized in that, The second voltage comparison control module includes a second switching transistor; The second voltage comparison control module is configured to turn off the second switch when the first switch is in the on state, or when the first switch is in the off state and the second voltage is greater than the first reference voltage, so as to output the second control signal in the first level state. The second voltage comparison control module is further configured to turn on the second switch when the first switch is in the off state and the second voltage is less than the first reference voltage, so as to output the second control signal in the second level state. The second voltage comparison control module is further configured to maintain the second switch in its current state when the first switch is in the off state and the second voltage is equal to the first reference voltage, so as to continuously output the second control signal of the first level state or the second level state.

4. The voltage switching circuit according to claim 1, characterized in that, The relay includes a first common contact, a second common contact, a first normally open contact, a second normally open contact, a third normally open contact, and a fourth normally open contact, wherein the first normally open contact is connected to the second normally open contact; When the first common contact is connected to the first normally open contact and the second common contact is connected to the second normally open contact, the transformer is in the first connection state; When the first common contact is connected to the third normally open contact and the second common contact is connected to the fourth normally open contact, the transformer is in a second connection state.

5. The voltage switching circuit according to claim 4, characterized in that, It also includes the transformer, wherein the transformer includes a first primary winding, a second primary winding, and a secondary winding; The first end of the first primary winding is connected to an AC wire, which is connected to the fourth normally open contact. The second end of the first primary winding is connected to the first common contact. The first end of the second primary winding is connected to an AC neutral wire, which is connected to the third normally open contact. The second end of the second primary winding is connected to the second common contact.

6. The voltage switching circuit according to claim 1, characterized in that, The switching module is further configured to control the relay to be in a normally open state according to the second control signal of the first level state, so that the first primary winding and the second primary winding of the transformer are in series to match the first AC voltage. The switching module is further configured to control the relay to be in a closed state according to the second control signal of the second level state, so that the first primary winding and the second primary winding of the transformer are connected in parallel to match the second AC voltage, wherein the first AC voltage is greater than the second AC voltage.

7. The voltage switching circuit according to claim 1, characterized in that, Both the first voltage comparison control module and the second voltage comparison control module include a first diode, a first voltage divider resistor, and a second voltage divider resistor; the first voltage comparison control module also includes a first comparator, a first transistor, and a second diode, and the second voltage comparison control module also includes a second comparator and a second transistor; The cathode of the first diode is connected to the non-inverting input of the first comparator and the inverting input of the second comparator. The inverting input of the first comparator is connected to the cathode of the second diode. The anode of the second diode is connected to the buck module. The non-inverting input of the second comparator is connected to the buck module. The output terminals of the first comparator and the second comparator are both connected to the first terminal of the first voltage divider resistor. The second terminal of the first voltage divider resistor is connected to the first terminal of the second voltage divider resistor, the base of the first transistor, and the base of the second transistor, respectively. The negative power supply terminals of the first comparator, the second comparator, the second terminal of the second voltage divider resistor, the emitter of the first transistor, and the emitter of the second transistor are all grounded. The positive power supply terminals of the first comparator and the second comparator are both connected to the buck module. The collector of the first transistor is connected to the base of the second transistor, and the collector of the second transistor is connected to the switching module.

8. The voltage switching circuit according to claim 1, characterized in that, The voltage input module includes an AC power line, an AC neutral wire, a fuse, a varistor, and a bridge rectifier; The first end of the AC wire is connected to the positive terminal of the AC power supply, and the first end of the AC neutral wire is connected to the negative terminal of the AC power supply. The first end of the fuse is connected to the second end of the AC wire, the second end of the fuse is connected to the first end of the varistor, and the second end of the varistor is connected to the second end of the AC neutral wire. The positive input terminal of the bridge rectifier is connected to the series node of the fuse and the varistor, the negative input terminal of the bridge rectifier is connected to the second end of the AC neutral line, the positive output terminal of the bridge rectifier is connected to the step-down module and the voltage sampling module, and the negative output terminal of the bridge rectifier is grounded.

9. The voltage switching circuit according to claim 1, characterized in that, The voltage sampling module includes a voltage divider unit and a voltage follower unit; The voltage divider unit includes a third voltage divider resistor, a fourth voltage divider resistor, a Zener diode, and a first capacitor; the voltage follower unit includes a follower. The first end of the third voltage divider resistor is connected to the output end of the voltage input module, the second end of the third voltage divider resistor is connected to the first end of the fourth voltage divider resistor, the second end of the fourth voltage divider resistor is grounded, and the Zener diode and the first capacitor are connected in parallel with the fourth voltage divider resistor respectively. The non-inverting input of the follower is connected to the series node of the third and fourth voltage divider resistors, the output of the follower is connected to the first voltage comparison control module and the second voltage comparison control module, and the inverting input of the follower is connected to the first voltage comparison control module.

10. The voltage switching circuit according to claim 1, characterized in that, The step-down module includes a primary step-down unit and a secondary step-down unit; The first-stage step-down unit includes a DC-DC converter chip and corresponding peripheral devices, and the second-stage step-down unit includes a fifth voltage divider resistor and a reference voltage chip. The first end of the fifth voltage divider resistor is connected to the first-stage step-down unit, the second end of the fifth voltage divider resistor is connected to the input pin of the reference voltage chip, the output pin of the reference voltage chip is connected to the first voltage comparison control module and the second voltage comparison control module, and the ground pin of the reference voltage chip is grounded.

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