Power switching circuit and gas appliance

Abstract

The utility model discloses a power supply switching circuit and a gas appliance, the power supply switching circuit comprises a switch unit, a unidirectional conduction unit and a control unit, the switch unit comprises a first switch transistor and a second switch transistor, and the first switch transistor and the second switch transistor are reversely connected in series between a standby power supply and a main power supply; the first end of the unidirectional conduction unit is connected with the control end of the first switch transistor, the second end of the unidirectional conduction unit is connected with the control end of the second switch transistor, and the control unit is connected with the second end of the unidirectional conduction unit and the control end of the second switch transistor. Therefore, when the first switch transistor and the second switch transistor are switched off, the main power supply and the standby power supply cannot form an access through the control end of the first switch transistor and the control end of the second switch transistor, the short circuit of the main power supply and the standby power supply is avoided, and the safety is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to power supply technology especially relates to a power switching circuit and gas utensil. BACKGROUND

[0002] In order to guarantee the stable operation of equipment, some equipment is set to standby power supply, when the main power supply is powered off, starting standby power supply power supply.

[0003] At present, the power switching circuit is usually used to realize the automatic switching between main power supply and standby power supply. Figure 1 The structure diagram of the prior art power switching circuit is shown as Figure 1 The main power supply Vmain is directly connected to the load to supply power to the load, and the standby power supply Vbackup supplies power to the load after being controlled by the switching transistor Q1 and the switching transistor Q2, and the control ends of the switching transistor Q1 and the switching transistor Q2 are connected to the control circuit (not shown in the figure). When the main power supply Vmain is normal, the control circuit controls the switching transistor Q1 and the switching transistor Q2 to be turned off at the same time, and the main power supply Vmain supplies power to the load; when the main power supply Vmain is powered off, the control circuit controls the switching transistor Q1 and the switching transistor Q2 to be turned on at the same time, and the standby power supply Vbackup supplies power to the load through the switching transistor MOS. Among them, the switching transistor Q1 and the switching transistor Q2 are reversely connected in series, so as to ensure that the standby power supply Vbackup and the main power supply Vmain cannot form a path through the switching transistor Q1 and the switching transistor Q2 after the switching transistor Q1 and the switching transistor Q2 are turned off.

[0004] When the main power supply Vmain is normal, the switching transistor Q1 and the switching transistor Q2 are in the off state, but since the control ends of the switching transistor Q1 and the switching transistor Q2 are connected together, the main power supply Vmain forms a path with the standby power supply Vbackup through the control end of the switching transistor Q1 and the control end of the switching transistor Q2, which leads to short circuit and brings safety hazards. INVENTION CONTENTS

[0005] One of the technical problems solved by the utility model is to provide a power switching circuit, which can avoid the short circuit of the main power supply and the standby power supply, and improve the safety.

[0006] The second technical problem solved by the utility model is to provide a gas utensil, which can avoid the short circuit of the main power supply and the standby power supply, and improve the safety.

[0007] The first technical problem is solved by the following technical scheme:

[0008] A power switching circuit for switching between a main power supply and a backup power supply, the main power supply having a higher voltage than the backup power supply, comprising:

[0009] a switching unit comprising a first switching transistor and a second switching transistor, the first switching transistor and the second switching transistor being connected in reverse series between the backup power supply and the main power supply, an output terminal of the main power supply being connected to a load;

[0010] a unidirectional conduction unit, a first end of the unidirectional conduction unit being connected to a control terminal of the first switching transistor, a second end of the unidirectional conduction unit being connected to a control terminal of the second switching transistor, the unidirectional conduction unit having a characteristic of being cut off from the second end to the first end;

[0011] a control unit, the control unit being connected to the second end of the unidirectional conduction unit and the control terminal of the second switching transistor.

[0012] The power switching circuit provided by the utility model is used for switching between a main power supply and a backup power supply, the main power supply having a higher voltage than the backup power supply, comprising a switching unit, a unidirectional conduction unit and a control unit, the switching unit comprising a first switching transistor and a second switching transistor, the first switching transistor and the second switching transistor being connected in reverse series between the backup power supply and the main power supply, an output terminal of the main power supply being connected to a load, a first end of the unidirectional conduction unit being connected to a control terminal of the first switching transistor, a second end of the unidirectional conduction unit being connected to a control terminal of the second switching transistor, the unidirectional conduction unit having a characteristic of being cut off from the second end to the first end, the control unit being connected to the second end of the unidirectional conduction unit and the control terminal of the second switching transistor, since the unidirectional conduction unit has the characteristic of being cut off from the second end to the first end, it can be ensured that when the first switching transistor and the second switching transistor are turned off, the main power supply and the backup power supply cannot form a path through the control terminal of the first switching transistor and the control terminal of the second switching transistor, the situation of the main power supply and the backup power supply being short-circuited is avoided, and safety is improved.

[0013] In some embodiments of the utility model, the unidirectional conduction unit comprises a unidirectional diode, an anode of the unidirectional diode being connected to the control terminal of the first switching transistor, a cathode of the unidirectional diode being connected to the control terminal of the second switching transistor and the control unit respectively.

[0014] In some embodiments of the utility model, the first switch transistor and the second switch transistor are both P channel metal oxide semiconductor field effect transistor, the source of first switch transistor is connected with standby power supply, the drain of first switch transistor is connected with the drain of second switch transistor, the source of second switch transistor is connected with main power supply, the gate of first switch transistor is connected with the first end of unidirectional conduction unit, the second end of unidirectional conduction unit is connected with the gate of second switch transistor and control unit respectively.

[0015] The power switching circuit further comprises a voltage dividing unit, a first end of the voltage dividing unit is connected with the control unit, a second end of the voltage dividing unit is grounded, and a third end of the voltage dividing unit is connected with the second end of the unidirectional conduction unit and the control end of the second switch transistor respectively.

[0016] In some embodiments of the utility model, the voltage dividing unit comprises a first resistor and a second resistor, a first end of the first resistor is connected with the control unit, a second end of the first resistor is connected with the second end of the unidirectional conduction unit, the control end of the second switch transistor and a first end of the second resistor respectively, and a second end of the second resistor is grounded.

[0017] In some embodiments of the utility model, the power switching circuit further comprises a current limiting unit, a first end of the current limiting unit is connected with the third end of the voltage dividing unit, and a second end of the current limiting unit is connected with the second end of the unidirectional conduction unit and the control end of the second switch transistor respectively.

[0018] In some embodiments of the utility model, a voltage collection end of the control unit is connected with an output end of the main power supply, and the voltage of the main power supply is collected.

[0019] In some embodiments of the utility model, the power switching circuit further comprises a voltage collection unit, an input end of the voltage collection unit is connected with an output end of the main power supply, and an output end of the voltage collection unit is connected with a voltage collection end of the control unit.

[0020] In some embodiments of the utility model, the voltage collection unit comprises a third resistor and a fourth resistor, a first end of the third resistor is connected with an output end of the main power supply, a second end of the third resistor is connected with a first end of the fourth resistor and a voltage collection end of the control unit respectively, and a second end of the fourth resistor is grounded.

[0021] In some embodiments of the utility model, the power switching circuit further comprises an energy storage unit, a first end of the energy storage unit is grounded, and a second end of the energy storage unit is connected with a power supply input end of the control unit.

[0022] The second technical problem is solved by the following technical solution:

[0023] A gas appliance comprises the power switching circuit provided by any of the preceding embodiments of the present application.

[0024] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present application will be further described in detail below according to the drawings and embodiments.

[0026] Figure 1 is a structural schematic diagram of an existing power switching circuit;

[0027] Figure 2 is a structural schematic diagram of a power switching circuit provided by the present application;

[0028] Figure 3 is a structural schematic diagram of another power switching circuit provided by the present application;

[0029] Figure 4 is a structural schematic diagram of another power switching circuit provided by the present application.

[0030] In the drawings:

[0031] 110, switch unit; 120, unidirectional conduction unit; 130, control unit; 140, voltage division unit; 150, current limiting unit; 160, voltage acquisition unit; 170, energy storage unit. DETAILED DESCRIPTION

[0032] In order to make the technical problems solved by the present application, the technical solutions adopted and the technical effects achieved more clear, the technical solutions of the embodiments of the present application will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] In the description of the utility model, unless another definite provision and limitation, the term "link", "connection", "fix" should do broad sense understanding, for example, can be fixed connection, also can be detachable connection, or be integrated;Can be mechanical connection, also can be electrical connection;Can be directly connected, also can pass through the indirect connection of intermediate medium, can be two element internal communication or two element mutual action relation.For the ordinary skill in the art, the specific meaning of the above-mentioned terms in the utility model can be understood according to the specific circumstances.

[0034] In the utility model, unless another definite provision and limitation, the first feature is "on" or "under" the second feature can include the first and second features direct contact, also can include the first and second features are not direct contact but contact through the additional features between them.Moreover, the first feature is "on", "above" and "on" the second feature includes the first feature is directly above and obliquely above the second feature, or just indicates that the horizontal height of the first feature is higher than the second feature.The first feature is "under", "below" and "under" the second feature includes the first feature is directly below and obliquely below the second feature, or just indicates that the horizontal height of the first feature is less than the second feature.In addition, the terms "first", "second", are just used to distinguish in the description, and have no special meaning.

[0035] Figure 2 The structural diagram of the power switching circuit provided by the utility model is shown as Figure 2 The power switching circuit is used to switch between main power Vmain and backup power Vbackup, under normal circumstances, the voltage of main power Vmain is greater than the voltage of backup power Vbackup, and the power switching circuit comprises:

[0036] The switch unit 110 includes the first switch transistor Q1 and the second switch transistor Q2, the first switch transistor Q1 and the second switch transistor Q2 are reversely connected between the backup power Vbackup and the main power Vmain, and the output end Vload of the main power Vmain is connected with the load.

[0037] The unidirectional conduction unit 120 is connected with the control end of the first switch transistor Q1 at the first end, and is connected with the control end of the second switch transistor Q2 at the second end, and the unidirectional conduction unit 120 has the characteristic of cut-off from the second end to the first end, that is, the current can only flow from the first end to the second end of the unidirectional conduction unit 120, and cannot flow from the second end to the first end of the unidirectional conduction unit 120.

[0038] The control unit 130 is connected with the second end of the unidirectional conduction unit 120 and the control end of the second switch transistor Q2.

[0039] For example, the control unit 130 can directly or indirectly collect the voltage of the main power supply Vmain. When the voltage of the main power supply Vmain is greater than or equal to a preset value, it indicates that the main power supply Vmain is working normally, and the control unit 130 sends a turn-off signal to the first switch transistor Q1 and the second switch transistor Q2, so that the first switch transistor Q1 and the second switch transistor Q2 are turned off, ensuring that the main power supply Vmain and the backup power supply Vbackup cannot form a path through the switch transistor Q1 and the switch transistor Q2, and the load is powered by the main power supply Vmain. In addition, since the unidirectional conduction unit 120 has the characteristic of being cut off from the second end to the first end, it can be ensured that when the first switch transistor Q1 and the second switch transistor Q2 are turned off, the main power supply Vmain and the backup power supply Vbackup cannot form a path through the control end of the first switch transistor Q1 and the control end of the second switch transistor Q2, avoiding the short circuit of the main power supply Vmain and the backup power supply Vbackup, and improving the safety. When the voltage of the main power supply Vmain is less than the preset value, it indicates that the main power supply Vmain is under voltage or power failure, and the control unit 130 sends a turn-on signal to the first switch transistor Q1 and the second switch transistor Q2, so that the first switch transistor Q1 and the second switch transistor Q2 are turned on, and the load is powered by the backup power supply Vbackup.

[0040] The power supply switching circuit provided by the utility model, including switching unit, unidirectional conduction unit and control unit, switching unit includes first switch transistor and second switch transistor, first switch transistor and second switch transistor reverse series between backup power supply and main power supply, the output end of main power supply connects load, the first end of unidirectional conduction unit is connected with the control end of first switch transistor, the second end of unidirectional conduction unit is connected with the control end of second switch transistor, unidirectional conduction unit has the characteristic of being cut off from the second end to the first end, the second end of control unit and the control end of second switch transistor are connected, because unidirectional conduction unit has the characteristic of being cut off from the second end to the first end, can ensure that when first switch transistor and second switch transistor are turned off, the main power supply and the backup power supply cannot form a path through the control end of the first switch transistor and the control end of the second switch transistor, avoiding the short circuit of the main power supply and the backup power supply, and improving the safety.

[0041] In order for those skilled in the art to more clearly understand the technical scheme of the utility model, the following will describe the scheme of the utility model through specific embodiments.

[0042] In some embodiments of the utility model, as Figure 2As shown, the one-way conducting unit 120 includes a one-way diode D1, the anode of the one-way diode D1 is connected with the control end of the first switch transistor Q1, the cathode of the one-way diode D1 is connected with the control end of the second switch transistor Q2 and the control unit 130 respectively. It should be noted that in other embodiments of the present application, the one-way conducting unit 120 can also include other components or multiple one-way diodes, as long as it has the characteristic of the second end to the first end cut-off, and the present application does not limit it here.

[0043] In some embodiments of the present application, as shown in Figure 2 As shown, the first switch transistor Q1 and the second switch transistor Q2 are both P-channel metal-oxide-semiconductor field-effect transistors (PMOS), the source S of the first switch transistor Q1 is connected with the backup power supply Vbackup, the drain D of the first switch transistor Q1 is connected with the drain D of the second switch transistor Q2, and the source S of the second switch transistor Q2 is connected with the main power supply Vmain, so that when the first switch transistor Q1 is turned off, the parasitic diode of the first switch transistor Q1 can ensure that the backup power supply Vbackup is turned off to the main power supply Vmain, and when the second switch transistor Q2 is turned off, the parasitic diode of the second switch transistor Q2 can ensure that the main power supply Vmain is turned off to the backup power supply Vbackup. The gate G of the first switch transistor Q1 is connected with the first end (anode of the one-way diode D1) of the one-way conducting unit 120, and the second end (cathode of the one-way diode D1) of the one-way conducting unit 120 is connected with the gate G of the second switch transistor Q2 and the control unit 130 respectively.

[0044] The withstand voltage value and current value of the first switch transistor Q1 and the second switch transistor Q2 need to be determined according to the voltage of the main power supply Vmain and the backup power supply Vbackup and the load characteristics, and it is recommended to reserve ≥50% margin for normal use, the first switch transistor Q1 and the second switch transistor Q2 use the same model, and exemplarily, TL3401A field effect transistor is selected.

[0045] It should be noted that in other embodiments of the present application, the first switch transistor Q1 and the second switch transistor Q2 are both N-channel metal-oxide-semiconductor field-effect transistors (NMOS), the drain D of the first switch transistor Q1 is connected with the backup power supply Vbackup, the source S of the first switch transistor Q1 is connected with the source S of the second switch transistor Q2, and the drain D of the second switch transistor Q2 is connected with the main power supply Vmain.

[0046] Figure 3 Another power supply switching circuit provided by the present application is shown in the structural schematic diagram, which further illustrates the technical scheme of the present application on the basis of the foregoing embodiment, as shown in Figure 3As shown, the power switching circuit further comprises a voltage dividing unit 140, a first end of the voltage dividing unit 140 is connected with the control unit 130, a second end of the voltage dividing unit 140 is grounded, and a third end of the voltage dividing unit 140 is connected with the second end of the unidirectional conduction unit 120 (i.e. the cathode of the unidirectional diode D1) and the control end of the second switch transistor Q2 respectively. For example, when the voltage of the main power supply Vmain is greater than or equal to a preset value, it indicates that the main power supply Vmain is working normally, the control unit 130 sends a high-level signal, the high-level signal is divided by the voltage dividing unit 140, and is transmitted to the control ends of the first switch transistor Q1 and the second switch transistor Q2, so that the first switch transistor Q1 and the second switch transistor Q2 are turned off, and the load is powered by the main power supply Vmain. When the voltage of the main power supply Vmain is less than the preset value, it indicates that the main power supply Vmain is under voltage or power failure, the control unit 130 sends a low-level signal (or no signal), so that the first switch transistor Q1 and the second switch transistor Q2 are turned on, and the load is powered by the backup power supply Vbackup.

[0047] It should be noted that, in other embodiments of the present application, the first switch transistor Q1 and the second switch transistor Q2 can also be N-channel metal oxide semiconductor field effect transistors, and correspondingly, the voltage dividing unit can be modified, which is not limited in the embodiments of the present application.

[0048] In some embodiments of the present application, as shown in Figure 3 As shown, the voltage dividing unit 140 comprises a first resistor R1 and a second resistor R2, a first end of the first resistor R1 is connected with the control unit 130, a second end of the first resistor R1 is connected with the second end of the unidirectional conduction unit 120 (i.e. the cathode of the unidirectional diode D1), the control end of the second switch transistor Q2 and a first end of the second resistor R2 respectively, and a second end of the second resistor R2 is grounded. For example, when the voltage of the main power supply Vmain is greater than or equal to a preset value, it indicates that the main power supply Vmain is working normally, the control unit 130 sends a high-level signal, the high-level signal is divided by the first resistor R1 and the second resistor R2, and the voltage of the second resistor R2 is transmitted to the control ends of the first switch transistor Q1 and the second switch transistor Q2, so that the first switch transistor Q1 and the second switch transistor Q2 are turned off, and the load is powered by the main power supply Vmain. When the voltage of the main power supply Vmain is less than the preset value, it indicates that the main power supply Vmain is under voltage or power failure, the control unit 130 sends a low-level signal (or no signal), so that the first switch transistor Q1 and the second switch transistor Q2 are turned on, and the load is powered by the backup power supply Vbackup.

[0049] In some embodiments of the present application, as shown in Figure 3As shown, the power switching circuit further comprises a current limiting unit 150, a first end of the current limiting unit 150 is connected with a third end of the voltage dividing unit 140 (i.e. a first end of the second resistor R2), and a second end of the current limiting unit 150 is connected with a second end of the unidirectional conducting unit 120 (i.e. a cathode of the unidirectional diode D1) and a control end of the second switch transistor Q2 respectively. The current limiting unit 150 plays a role of current limiting, avoiding damage caused by excessive current at the control end of the first switch transistor Q1 and the second switch transistor Q2.

[0050] In some embodiments of the present application, as shown in Figure 3 As shown, the current limiting unit 150 comprises a current limiting resistor R5, a first end of the current limiting resistor R5 is connected with a third end of the voltage dividing unit 140 (i.e. a first end of the second resistor R2), and a second end of the current limiting resistor R5 is connected with a second end of the unidirectional conducting unit 120 (i.e. a cathode of the unidirectional diode D1) and a control end of the second switch transistor Q2 respectively. In other embodiments of the present application, the current limiting unit can also comprise other electronic elements or multiple resistors, as long as it can play a role of current limiting, which is not limited in the present application.

[0051] In some embodiments of the present application, as shown in Figure 3 As shown, the control unit 130 can be a control chip U1, which can adopt XC61CC series, XC61CN series chip, a voltage collection end ADC of the control unit 130 is connected with an output end Vload of the main power supply Vmain, for collecting voltage of the main power supply Vmain. The control unit 130 directly collects voltage of the power supply Vmain, a voltage detection module (ADC analog-digital conversion) is built in the control unit 130, by reading input voltage of the main power supply Vmain, compared with internal voltage reference, when detecting that the voltage of the main power supply Vmain is greater than or equal to a preset value, a high level is output from an output end Vout of the control unit 130, when detecting that the voltage of the main power supply Vmain is less than the preset value, a low level is output from the output end Out of the control unit 130 or no output. At the same time, the voltage collection end ADC of the control unit 130 can also be used as a power supply input end of the control unit 130, and the control unit 130 directly takes power from the main power supply Vmain.

[0052] Figure 4 Another power switching circuit provided by the present application has a structure schematic diagram as shown in Figure 4 As shown, the difference between this embodiment and the foregoing embodiment is that the voltage of the main power supply Vmain is collected by a voltage collection unit, and the rest of the circuit structure is the same as the foregoing embodiment, which will not be repeated here.

[0053] As shown in Figure 4As shown, the power switching circuit also includes a voltage acquisition unit 160. The input terminal of the voltage acquisition unit 160 is connected to the output terminal Vload of the main power supply Vmain, and the output terminal of the voltage acquisition unit 160 is connected to the voltage acquisition terminal ADC of the control unit 130. The voltage acquisition unit 160 is used to acquire the voltage of the main power supply Vmain and convert it into a voltage that meets the operating voltage range of the control unit 130. The control unit 130 includes a control chip U2, which has a built-in voltage detection module (ADC analog-to-digital converter). By reading the voltage output by the voltage acquisition unit 160 and comparing it with an internal voltage reference, it determines whether the voltage of the main power supply Vmain is greater than or equal to a preset value. When the voltage of the main power supply Vmain is greater than or equal to the preset value, the output terminal Out of the control unit 130 outputs a high level; when the voltage of the main power supply Vmain is less than the preset value, the output terminal Vout of the control unit 130 outputs a low level or no output. The power input terminal Vin of the control unit 130 is connected to the power supply Vmcu. The power supply Vmcu can be obtained from the output terminal Vload of the main power supply Vmain and converted by the DC-DC conversion circuit. Alternatively, it can be an external power supply. This invention does not limit the power supply.

[0054] In some embodiments of this utility model, such as Figure 4 As shown, the voltage acquisition unit 160 includes a third resistor R3 and a fourth resistor R4. The first end of the third resistor R3 is connected to the output terminal Vload of the main power supply Vmain. The second end of the third resistor R3 is connected to the first end of the fourth resistor R4 and the voltage acquisition terminal ADC2 of the control unit 130. The second end of the fourth resistor R4 is grounded. The voltage acquisition unit 160 divides the acquired voltage of the main power supply Vmain and outputs the voltage of the fourth resistor R4 to the control unit 130.

[0055] In some embodiments of this utility model, such as Figure 3 , 4 As shown, the power switching circuit also includes an energy storage unit 170. The first terminal of the energy storage unit 170 is grounded, and the second terminal of the energy storage unit 170 is connected to the power supply input terminal of the control unit 130. Figure 3 ADC in Figure 4 The energy storage unit 170 is connected to the main power supply (Vmain) during the operation of the power switching circuit. For example, the energy storage unit 170 is charged and stores electrical energy during the operation of the power switching circuit. When the power switching circuit switches from being powered by the backup power supply Vbackup to being powered by the main power supply Vmain, the energy storage unit 170 releases electrical energy to maintain the operation of the control unit 130. The control unit 130 continues to output a conduction signal. During the switching process, the backup power supply Vbackup continuously supplies power to the load, avoiding the situation where the control unit 130 loses power during the switching process, which would cause the backup power supply Vbackup to shut down its output prematurely, thus improving the operating stability of the circuit.

[0056] In some embodiments of the utility model, as shown in Figure 3 、 4 Indicated, energy storage unit 170 includes energy storage capacitor C1 and pull-up resistor R6, the first end of energy storage capacitor C1 is grounded, the second end of energy storage capacitor C1 is connected with the first end of pull-up resistor R6, the second end of pull-up resistor R6 is connected with the input end (the ADC in Figure 3 Vin in Figure 4 Control unit 130) and the output end Vload of main power supply Vmain respectively.

[0057] The utility model also provides a gas appliance, the gas appliance includes the power supply switching circuit provided by any prior embodiment of the utility model, has the function and effect of the power supply switching circuit provided by any prior embodiment of the utility model.

[0058] In the description herein, it is to be understood that the terms "upper", "lower", "left", "right", and the like, orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model.

[0059] In the description of the present specification, the description referring to the terms "an embodiment", "an example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0060] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment only contains one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

[0061] The technical principles of the utility model are described above in conjunction with specific embodiments. These descriptions are only to explain the principles of the utility model, and cannot be interpreted in any way as a limitation on the protection scope of the utility model. Based on the explanation here, those skilled in the art do not need to pay creative labor to think of other specific embodiments of the utility model, and these ways will fall within the protection scope of the utility model.

Claims

1. A power switching circuit for enabling switching between a main power supply (Vmain) and a backup power supply (Vbackup), the voltage of the main power supply (Vmain) being greater than the voltage of the backup power supply (Vbackup), characterized in that, The power supply switching circuit comprises: a switching unit (110) comprising a first switching transistor (Q1) and a second switching transistor (Q2), the first switching transistor (Q1) and the second switching transistor (Q2) being connected in anti-series between a backup power supply (Vbackup) and a main power supply (Vmain), an output end of the main power supply (Vmain) being connected to a load; a unidirectional conduction unit (120), a first end of the unidirectional conduction unit (120) being connected to a control end of the first switching transistor (Q1), a second end of the unidirectional conduction unit (120) being connected to a control end of the second switching transistor (Q2), the unidirectional conduction unit (120) having a characteristic of being cut off from the second end to the first end; a control unit (130), the control unit (130) being connected to the second end of the unidirectional conduction unit (120) and the control end of the second switching transistor (Q2).

2. The power switching circuit of claim 1, wherein, The unidirectional conduction unit (120) comprises a unidirectional diode (D1), an anode of the unidirectional diode (D1) being connected to the control end of the first switching transistor (Q1), a cathode of the unidirectional diode (D1) being connected to the control end of the second switching transistor (Q2) and the control unit (130) respectively.

3. The power switching circuit according to claim 1 or 2, characterized in that The first switching transistor (Q1) and the second switching transistor (Q2) are both P-channel metal oxide semiconductor field effect transistors, a source of the first switching transistor (Q1) being connected to the backup power supply (Vbackup), a drain of the first switching transistor (Q1) being connected to a drain of the second switching transistor (Q2), a source of the second switching transistor (Q2) being connected to the main power supply (Vmain), a gate of the first switching transistor (Q1) being connected to the first end of the unidirectional conduction unit (120), the second end of the unidirectional conduction unit (120) being connected to the gate of the second switching transistor (Q2) and the control unit (130) respectively; The power supply switching circuit further comprises a voltage dividing unit (140), a first end of the voltage dividing unit (140) being connected to the control unit (130), a second end of the voltage dividing unit (140) being grounded, a third end of the voltage dividing unit (140) being connected to the second end of the unidirectional conduction unit (120) and the control end of the second switching transistor (Q2) respectively.

4. The power switching circuit of claim 3, wherein, The voltage dividing unit (140) comprises a first resistor (R1) and a second resistor (R2), a first end of the first resistor (R1) being connected to the control unit (130), a second end of the first resistor (R1) being connected to the second end of the unidirectional conduction unit (120), the control end of the second switching transistor (Q2) and a first end of the second resistor (R2) respectively, a second end of the second resistor (R2) being grounded.

5. The power switching circuit of claim 3, wherein, The power switching circuit further comprises a current limiting unit (150), a first end of the current limiting unit (150) is connected with a third end of the voltage dividing unit (140), and a second end of the current limiting unit (150) is connected with a second end of the unidirectional conducting unit (120) and a control end of the second switch transistor (Q2) respectively.

6. The power switching circuit according to claim 1, 2, 4 or 5, characterized in that, A voltage collecting end of the control unit (130) is connected with an output end of the main power supply (Vmain) for collecting a voltage of the main power supply (Vmain).

7. The power switching circuit of claim 6, wherein, Further comprising a voltage collecting unit (160), an input end of the voltage collecting unit (160) is connected with the output end of the main power supply (Vmain), and an output end of the voltage collecting unit (160) is connected with the voltage collecting end of the control unit (130).

8. The power switching circuit of claim 7, wherein, The voltage collecting unit (160) comprises a third resistor (R3) and a fourth resistor (R4), a first end of the third resistor (R3) is connected with the output end of the main power supply (Vmain), a second end of the third resistor (R3) is connected with a first end of the fourth resistor (R4) and the voltage collecting end of the control unit (130) respectively, and a second end of the fourth resistor (R4) is grounded.

9. The power switching circuit of claim 6, wherein, Further comprising an energy storage unit (170), a first end of the energy storage unit (170) is grounded, and a second end of the energy storage unit (170) is connected with a power supply input end of the control unit (130).

10. A gas appliance characterised in that, The power switching circuit comprises the power switching circuit according to any one of claims 1-9.

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