CN218415845U

CN218415845U - Power supply circuit and electric energy receiving circuit

Info

Publication number: CN218415845U
Application number: CN202221622708.7U
Authority: CN
Inventors: 闫少鹏; 冯维一; 余峰
Original assignee: Ningbo Weie Electronics Technology Ltd
Current assignee: Ningbo Weie Electronics Technology Ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2023-01-31
Anticipated expiration: 2032-06-27

Abstract

The utility model belongs to the technical field of electronic equipment charging and specifically relates to a supply circuit and electric energy receiving circuit. The utility model discloses supply circuit and electric energy receiving circuit can be connected to connection port's change over switch with first power and current-limiting resistor forward or reversal through the setting, a control unit for detecting the voltage detection unit of connection port voltage and can be according to connection port's voltage control change over switch, can be when the contact polarity of treating charging equipment is opposite with the contact polarity in storehouse that charges, detect the low-voltage by voltage detection unit, and the polarity reversal of the first contact of supply circuit and second contact is put into by control unit automatic control change over switch, thereby realized need not to treat that charging equipment puts into the storehouse that charges with specific direction and just can normally charge for equipment, the convenience that the user used has improved greatly.

Description

Power supply circuit and electric energy receiving circuit

Technical Field

The utility model belongs to the technical field of electronic equipment charging and specifically relates to a supply circuit and electric energy receiving circuit.

Background

Currently, many portable electronic devices are charged by contact, such as bluetooth headsets, charge pal, etc., and generally, the devices are charged through a charging chamber having at least one set of contacts made of two metal spring pieces, which respectively output a positive voltage and a zero voltage (simultaneously, ground GND). When the electronic equipment is inserted into the charging bin, the metal contact at the bottom or the side of the electronic equipment is contacted with the metal spring piece in the charging bin, so that the battery in the electronic equipment can be charged. In the storehouse of charging that uses at present, the output polarity of two metal spring pieces is fixed, for example the positive voltage of left side metal spring piece output, zero voltage of right side metal spring piece output, and the two is decided by the storehouse internal circuit that charges, can't change. When the equipment needing charging is an earphone and other products with irregular shapes, the earphone can be placed into the charging bin only in a specific direction, and the charging can be normally carried out in the mode; however, when the device to be charged is a product with a symmetrical shape, such as a rectangular charger, the device can still be placed in the charging bin after rotating or turning 180 °, which may cause the polarity of the output contact in the charging bin to be opposite to the polarity of the receiving contact on the electronic device, and thus the user needs to carefully identify the direction of the device when placing the device, which may bring inconvenience to the user.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model aims at providing a supply circuit and electric energy receiving circuit for the polarity that makes the output contact in storehouse of charging can be according to electronic equipment's the direction of placing and is reversed automatically, thereby makes the equipment of waiting to charge need not to put into the storehouse of charging with specific direction, improves the convenience that the user used.

In a first aspect, an embodiment of the present invention provides a power supply circuit, which is used for supplying dc power to a powered device, the power supply circuit includes: a connection port having a first contact and a second contact, the connection port for connecting to a powered device in a forward or reverse direction; a first power supply; a current limiting resistor connected in series with the first power supply; a switch for connecting the first power source and the current limiting resistor to the connection port in a forward or reverse direction; a voltage detection unit for detecting a voltage of the connection port; and the control unit is respectively connected with the first power supply, the change-over switch and the voltage detection unit and is used for controlling the change-over switch to switch or keep the polarity of the connection port according to the voltage of the connection port.

Further, the control unit is configured to control the voltage detection unit to detect a first voltage of the connection port, control the switch to switch the connection state in response to the first voltage being less than a predetermined voltage value, and maintain the switch connection state in response to the first voltage being greater than the predetermined voltage value.

Further, the control unit is configured to control the voltage detection unit to detect a second voltage of the connection port in response to the switch switching completion, to report an error in response to the second voltage being less than the predetermined voltage value, and to keep the switch connection state unchanged in response to the second voltage being greater than the predetermined voltage value.

Further, the control unit is configured to control the switch to switch the connection state, and control the voltage detection unit to detect the voltage of the connection port before and after the switch is switched, and to set the voltage of the connection port before the switch is switched as a first voltage, and set the voltage of the connection port after the switch is switched as a second voltage.

Further, the control unit is configured to report an error in response to both the first voltage and the second voltage being less than the predetermined voltage value, maintain the connection state of the change-over switch in response to both the first voltage being less than the predetermined voltage value and the second voltage being greater than the predetermined voltage value, control the change-over switch to switch the connection state again in response to both the first voltage being greater than the predetermined voltage and the second voltage being less than the predetermined voltage, control the change-over switch to switch the connection state after a predetermined time interval in response to both the first voltage and the second voltage being greater than the predetermined voltage value, and control the voltage detection unit to detect the voltage of the connection port before and after the change-over switch is switched again.

Further, the predetermined time interval is 20 milliseconds.

Further, the predetermined voltage value is 0.7 volts.

Further, the power supply circuit further includes: the first switch is connected with the first power supply and the current-limiting resistor in series and used for connecting or disconnecting the first power supply and the current-limiting resistor with the change-over switch; and the power supply branch circuit is connected with the first power supply, the current-limiting resistor and the first switch in parallel and used for providing electric energy after the first switch is disconnected.

Further, the power supply branch includes: a second power supply; and a second switch connected in series with the second power supply for connecting or disconnecting the second power supply to or from the changeover switch.

Further, the control unit is configured to control the first switch to be opened and the second switch to be closed after keeping the connection state of the change-over switch unchanged.

In a second aspect, an embodiment of the present invention further provides an electric energy receiving circuit, where the electric energy receiving circuit is configured to receive electric energy provided by the power supply circuit; the power receiving circuit includes: a receiving port having a third contact and a fourth contact for connecting to the connection port; and a zener diode connected in series between the third contact and the fourth contact.

The utility model discloses supply circuit and electric energy receiving circuit can be connected to connection port's change over switch with first power and current-limiting resistor forward or reversal through the setting, a control unit for detecting the voltage detection unit of connection port voltage and can be according to connection port's voltage control change over switch, can be when the contact polarity of treating charging equipment is opposite with the contact polarity in storehouse that charges, detect the low-voltage by voltage detection unit, and the polarity reversal of the first contact of supply circuit and second contact is put into by control unit automatic control change over switch, thereby realized need not to treat that charging equipment puts into the storehouse that charges with specific direction and just can normally charge for equipment, the convenience that the user used has improved greatly.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of a usage mode of a power supply circuit and an electric energy receiving circuit according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a power supply circuit and an electric energy receiving circuit according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a power supply circuit and an electric energy receiving circuit according to another embodiment of the present invention;

fig. 4 is a power supply flow chart of the power supply circuit according to the embodiment of the present invention;

fig. 5 is a power supply flow chart of a power supply circuit according to another embodiment of the present invention;

fig. 6 is a power supply flow chart of the power supply branch according to the embodiment of the present invention.

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention.

Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Meanwhile, it should be understood that, in the following description, a "circuit" refers to a conductive loop constituted by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "connected to" another element or element/circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that there are no intervening elements present.

Unless the context clearly requires otherwise, throughout the description, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including but not limited to".

In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Fig. 1 is a schematic diagram of a usage mode of a power supply circuit and an electric energy receiving circuit according to an embodiment of the present invention. As shown in fig. 1, when the electronic device 02 is charged using the charging chamber 01, the electronic device 02 may be placed in the charging chamber 01 after rotating the electronic device 02 by 180 ° because the electronic device 02 has a rectangular shape. In the conventional charging chamber 01, the polarity of the power supply circuit is fixed, and the polarities of the outputs from the first contact C1 and the second contact C2 are also fixed, for example, the first contact C1 is a positive voltage, and the second contact C2 is a zero voltage. In the electronic device 02, the polarity of the power receiving circuit is also fixed, for example, the third contact C3 receives a positive voltage and the fourth contact C4 receives a zero voltage. When the electronic device 02 is placed in the charging chamber 01, the electronic device can be charged only by contacting the third contact C3 with the first contact C1 and contacting the fourth contact C4 with the second contact C2. If the electronic device 02 is rotated by 180 ° and placed in the charging chamber 01 such that the fourth contact C4 is in contact with the first contact C1 and the third contact C3 is in contact with the second contact C2, the electronic device 02 cannot be charged. Therefore, in the prior art, before the user uses the charging chamber 01 to charge the electronic device 02, the user needs to carefully identify the direction in which the electronic device 02 is placed, which brings much inconvenience to the user. In this embodiment, by using the power supply circuit of this embodiment, the polarities of the first contact C1 and the second contact C2 can be automatically reversed according to the placing direction of the electronic device 02, so that no matter the electronic device 02 is placed into the charging bin 01 in the forward direction or the reverse direction, the charging bin 01 can charge the electronic device 02, and the use of a user is more convenient.

Fig. 2 is a schematic structural diagram of a power supply circuit and an electric energy receiving circuit according to an embodiment of the present invention. As shown in fig. 2, the power supply circuit includes a connection port, a first power Vin1, a current limiting resistor R, a switch S0, a voltage detection unit 1, and a control unit 2. Wherein the connection port has a first contact C1 and a second contact C2 for forward or reverse connection to the powered device. The current limiting resistor R is connected in series with the first power source Vin 1. The switch S0 is used to connect the first power source Vin1 and the current limiting resistor R to the connection port voltage detection unit 1 in a forward or reverse direction for detecting the voltage of the connection port. The control unit 2 is connected to the first power source Vin1, the switch S0 and the voltage detection unit 1, respectively, and is configured to control the switch S0 to switch to the polarity of the connection port according to the voltage of the connection port.

The power receiving circuit 3 is used for receiving the power provided by the power supply circuit, and comprises a receiving port and a voltage stabilizing diode D. The receiving port is provided with a third contact C3 and a fourth contact C4 which are used for connecting the connecting port; a zener diode D is connected in series between the third contact C3 and the fourth contact C4. The voltage stabilizing diode D has the characteristics of forward conduction and reverse cut-off, and is arranged at the electric energy input end of the charged equipment to play the roles of preventing the input voltage from overshooting and protecting the reverse connection. In the charged device, when the zener diode D is in the reverse cut-off state, the power receiving circuit 3 can receive power to charge the device, and when the zener diode D is in the forward conduction state, it indicates that the charged device is reversely connected and cannot be charged. As shown in fig. 2, the charged device can be charged only when the third contact C3 is at a positive voltage and the fourth contact C4 is at zero voltage, and otherwise, the charged device cannot be charged. When the zener diode D is in the forward conducting state, the resistance thereof is very small, so that the voltage drop across the zener diode D is very small, and the first voltage of the connection port detected by the voltage detecting unit 1 is also very small. Conversely, when the zener diode D is in a reverse cut-off state, the reverse resistance of the zener diode D is large, the voltage drop across the zener diode D is also large, and the voltage detection unit 1 will detect a large voltage value. According to the principle, the control unit 2 is arranged to control the change-over switch S0 to change the connection state according to the voltage value detected by the voltage detection unit 1 by using the control unit 2, the polarity of the first contact C1 and the second contact C2 of the connection port can be automatically changed when the voltage value of the connection port detected by the voltage detection unit 1 is small, and when the voltage value of the connection port detected by the voltage detection unit 1 is high, the polarity of the first contact C1 and the second contact C2 is kept unchanged, so that the third contact C3 of the receiving port receives a positive voltage, and the fourth contact C4 receives a zero voltage, thereby ensuring that the normal charging can be performed no matter whether the charged device is in a positive or negative state. Specifically, the power supply circuit of the present embodiment may operate according to the steps in fig. 4 or fig. 5.

Fig. 4 is a power supply flow chart of the power supply circuit according to the embodiment of the present invention. In an optional implementation manner, the power supply circuit of this embodiment may supply power according to the steps shown in fig. 4, which specifically include the following steps:

s110, the voltage detection unit 1 detects a first voltage of the connection port.

The voltage detection unit 1 detects the first voltage of the connection port once at regular intervals, so that the power supply circuit can respond timely when equipment is connected to or disconnected from the connection port.

And S120, judging whether the first voltage is larger than a preset voltage value or not.

If the first voltage is greater than the predetermined voltage value, it indicates that there is no device to be charged connected, or the device to be charged is correctly connected, i.e. the zener diode D is in the reverse cut-off state, and the device can be directly charged, so step S130 is performed. If the first voltage is smaller than the predetermined voltage value, it indicates that the connection port is short-circuited, or the zener diode D of the device to be charged connected to the connection port is in a forward conduction state, that is, the connection polarity of the device to be charged is opposite to the output polarity of the current connection port, and the device cannot be normally charged, so that the process goes to step S140. Specifically, in this embodiment, when the zener diode D is turned on in the forward direction, the voltage drop across the zener diode D is less than 0.7V, so that the predetermined voltage value may be set to 0.7V, and when the voltage of the connection port is greater than 0.7V, it can be proved that the zener diode D of the device to be charged is not connected or the connected device to be charged is in the reverse blocking state.

And S130, keeping the connection state of the change-over switch S0 unchanged.

Further, it is also possible to determine whether the device to be charged is connected by determining whether the voltage value of the connection port detected by the voltage detection unit 1 is equal to the power supply voltage. If the voltage value of the connection port is equal to the power supply voltage, it is indicated that no equipment to be charged is accessed; if the voltage value of the connection port is smaller than the power voltage, the device to be charged is connected, and the connection polarity is correct.

S140, the control unit 2 controls the switch S0 to switch the connection state, so that the polarities of the first contact C1 and the second contact C2 are reversed.

S150, the voltage detecting unit 1 detects the second voltage of the connection port.

And S160, judging whether the second voltage is larger than a preset voltage value or not.

Since there may be two situations, that is, the zener diode D is turned on in the forward direction or the charged device is short-circuited when the first voltage is smaller than the predetermined voltage value, the control unit 2 needs to control the switch S0 to switch the connection state, so that the polarities of the first contact C1 and the second contact C2 are reversed, and then the second voltage of the connection port is detected again, and whether the second voltage is larger than the predetermined voltage value is determined. If the second voltage is greater than the predetermined voltage value, it indicates that after the polarities of the first contact C1 and the second contact C2 of the connection port are reversed, the zener diode D is in a reverse cut-off state, that is, the access polarity of the charged device is correct, and the charging can be performed normally, so step S170 is performed. If the second voltage is smaller than the predetermined voltage value, it indicates that the connection port is short-circuited, and therefore step S180 is executed.

And S170, keeping the connection state of the selector switch S0 unchanged.

S180, the control unit 2 reports errors.

Specifically, the error can be reported by controlling the flashing of the warning light or giving an alarm sound. When the short circuit is released, the control unit 2 responds to the increase of the voltage value of the connection port detected by the voltage detection unit 1 and automatically stops reporting errors.

Fig. 5 is a power supply flow chart of a power supply circuit according to another embodiment of the present invention. In an optional implementation manner, the power supply circuit of this embodiment may further perform power supply according to the steps shown in fig. 5, specifically including the following steps:

s210, the voltage detection unit 1 detects a first voltage of the connection port.

S220, the control unit 2 controls the switch S0 to switch the connection state, so that the polarities of the first contact C1 and the second contact C2 are reversed.

S230, the voltage detection unit 1 detects the second voltage of the connection port.

S240, judging whether the first voltage and the second voltage are both smaller than a preset voltage value.

If the first voltage and the second voltage are both less than the predetermined voltage value, it indicates that the connection port is short-circuited, and therefore step S250 is executed. If the first voltage and the second voltage are not both less than the predetermined voltage value, it indicates that the charged device is not short-circuited or the device to be charged is not connected to the connection port, and step S260 is executed.

S250, the control unit 2 reports an error.

Specifically, the error can be reported by controlling the flashing of the warning light or giving an alarm sound. When the short circuit is released, the control unit 2 will automatically stop reporting errors in response to the voltage value of the connection port detected by the voltage detection unit 1 rising, and control the voltage detection unit 1 and the switch S0 to re-execute the above steps S210-S240.

And S260, judging whether the second voltage is larger than a preset voltage value or not.

If the second voltage is greater than the predetermined voltage value, it indicates that the device to be charged is not connected to the current connection port, or the connection polarity of the device to be charged is correct, so step S270 is executed. If the second voltage is smaller than the predetermined voltage value, it indicates that the first voltage is larger than the predetermined voltage value, and the zener diode D in the current state is in a forward conduction state, that is, the polarity of the device to be charged accessed by the current connection port is opposite to the polarity of the connection port, and the device needs to be charged after the polarity of the connection port needs to be reversed again. Therefore, step S280 will be performed.

S270, judging whether the first voltage is larger than a preset voltage value or not.

If the first voltage is greater than the predetermined voltage value, that is, the first voltage and the second voltage are both greater than the predetermined voltage value, it indicates that no device to be charged is currently connected to the connection port, so step S271 is executed. If the first voltage is smaller than the predetermined voltage value, it indicates that the access polarity of the charging device is correct, and the charging operation can be performed, so step S272 is performed.

In some optional embodiments, in step S260, when the second voltage is greater than the predetermined voltage value, it may also be determined whether the device to be charged is connected by determining whether the second voltage is equal to the power supply voltage. If the second voltage is equal to the power voltage, it indicates that no device to be charged is connected, and step S271 is executed; if the second voltage is less than the power voltage, it indicates that the device to be charged is connected and the connection polarity is correct, and step S272 is executed.

S271, the control unit 2 controls the switch S0 to switch the connection state after a predetermined time interval, and controls the voltage detection unit 1 to detect the voltage of the connection port before and after the switch S0 is switched.

Specifically, the predetermined time interval may be 20ms. When no device to be charged is connected to the connection port, the power supply circuit is in a standby state, and the control unit 2 controls the voltage detection unit 1 and the switch S0 to periodically execute the above steps S210 to S240. Specifically, the control unit 2 may use the current second voltage as the first voltage of the next voltage detection period, then control the switch S0 to switch the connection state after 20ms, and then control the voltage detection unit 1 to detect the switched connection port voltage as the new second voltage. Then, step S240 is executed according to the first voltage and the second voltage of the present cycle. In some embodiments, the control unit 2 may also control the switch S0 to switch back to the initial state, and then re-execute the steps S210 to S240. The two modes can ensure that the power supply circuit continuously detects the connection port in the standby state, so that the connection port can be ensured to be timely responded to the access of the charging equipment.

And S272, keeping the connection state of the selector switch S0 unchanged.

S280, the control unit 2 controls the switch S0 to switch the connection state, so that the polarities of the first contact C1 and the second contact C2 are reversed. In the present embodiment, when the charged device is disconnected from the connection port after charging is finished, the control unit 2 responds to the voltage detection unit 1 detecting that the voltage value of the connection port increases, and the power supply circuit will resume the standby state, i.e. the control unit 2 controls the voltage detection unit 1 and the switch S0 to re-execute the above steps S210 to S240.

The power supply circuit of this embodiment is through two kinds of flows above-mentioned, all can realize according to the polarity of the connection port of polarity automatic adjustment power supply circuit when being put into by battery charging outfit to realize no matter by battery charging outfit forward or reverse put into the storehouse of charging, power supply circuit in the storehouse of charging can all be for electronic equipment carries out normal charging, provides convenience for user's use.

Fig. 3 is a schematic structural diagram of a power supply circuit and an electric energy receiving circuit according to another embodiment of the present invention. In some alternative embodiments, as shown in fig. 3, the power supply circuit further comprises a first switch S1 and a power supply branch 4. The first switch S1 is connected in series with the first power source Vin1 and the current-limiting resistor R, and is used for connecting or disconnecting the first power source Vin1 and the current-limiting resistor R with the switch S0. The power supply branch 4 is connected in parallel with the first power source Vin1, the current limiting resistor R and the first switch S1, and is used for providing electric energy after the first switch S1 is turned off. Specifically, the power supply branch 4 includes a second power source Vin2 and a second switch S2. The second switch S2 is connected in series with the second power source Vin2, and is used for connecting or disconnecting the second power source Vin2 with the switch S0. The first switch S1 and the second switch S1 are connected to the control unit 2, and can be opened or closed under the control of the control unit 2. Since there are situations in which the device to be charged is placed in reverse, i.e. the zener diode is forward-conducting, and situations in which the device to be charged is short-circuited during use, a current limiting resistor R is provided in the power supply circuit in order to avoid a situation in which the current in the power supply circuit is too high and the circuit is damaged. However, when normal charging is performed, the current limiting resistor R in the power supply circuit will consume extra energy, resulting in a decrease in charging efficiency. Therefore, the charging branch 4 is additionally provided in this embodiment, and the first switch S1 is turned off after the normal charging is started, so that the current-limiting resistor R and the first power Vin1 are disconnected. And meanwhile, the second switch S2 is closed, the second power supply Vin2 is used for charging the equipment, and the charging branch is not provided with the current-limiting resistor R, so that extra energy consumption can be avoided, and the charging efficiency is improved. The initial state of the power supply circuit in this embodiment is that the first switch S1 is closed, the second switch S2 is opened, the power supply circuit shown in fig. 2 supplies power and adjusts the polarity of the connection port, and when the polarity of the device to be charged connected to the connection port is correct, the power supply branch 4 operates according to the steps shown in fig. 6.

Fig. 6 is a power supply flow chart of the power supply branch 4 according to the embodiment of the present invention. As shown in fig. 6, the specific steps of the power supply circuit using the charging branch 4 to supply power are as follows:

s310, the control unit 2 controls the first switch S1 to be disconnected, and the first power source Vin1 and the current limiting resistor R are disconnected with the switch S0.

S320, the control unit 2 controls the second switch S2 to be closed, and connects the second power source Vin2 to the switch S0.

The steps S310 and S320 may be performed sequentially or synchronously, so that the charging of the device by using the charging branch 4 without the current-limiting resistor R can be realized when the device is normally charged, thereby improving the charging efficiency.

In some alternative embodiments, the power supply circuit may not include the second power source Vin2, and the power supply branch 4 is composed of the first power source Vin1 and the second switch S2, that is, the second switch S2 is connected in parallel with the current limiting resistor R. The second switch S2 is in an initial state of off, and after the charged device is powered on, the second switch S2 is closed, so that the current-limiting resistor R can be in short circuit, and the effects of avoiding extra energy consumption of the current-limiting resistor R and improving the charging efficiency are achieved.

To sum up, the utility model discloses supply circuit and electric energy receiving circuit can be connected to first power Vin1 and current-limiting resistor R forward or reverse through the setting and connect port 'S change over switch S0, a control unit 2 that is used for detecting the voltage detection unit 1 of connection port voltage and can be according to connection port' S voltage control change over switch S0, can be when the contact polarity of treating charging equipment and the contact polarity in charging storehouse are opposite, detect the low-voltage by voltage detection unit 1, and the polarity reversal of first contact C1 and second contact C2 with supply circuit by control unit 2 automatic control change over switch S0, thereby realized need not to treat that charging equipment puts into the charging storehouse with specific direction and just can normally charge for equipment, the convenience that the user used has improved greatly.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A power supply circuit for dc supplying a powered device, the power supply circuit comprising:

a connection port having a first contact and a second contact, the connection port for connecting to a powered device in a forward or reverse direction;

a first power supply;

a current limiting resistor connected in series with the first power supply;

a switch for connecting the first power source and the current limiting resistor to the connection port in a forward or reverse direction;

a voltage detection unit for detecting a voltage of the connection port; and

and the control unit is respectively connected with the first power supply, the change-over switch and the voltage detection unit and is used for controlling the change-over switch to switch over or keep the polarity of the connection port according to the voltage of the connection port.

2. The power supply circuit according to claim 1, wherein the control unit is configured to control the voltage detection unit to detect a first voltage of the connection port, control the switch to switch the connection state in response to the first voltage being less than a predetermined voltage value, and maintain the switch connection state in response to the first voltage being greater than the predetermined voltage value.

3. The power supply circuit according to claim 2, wherein the control unit is configured to control the voltage detection unit to detect a second voltage of the connection port in response to completion of switching of the switch, to report an error in response to the second voltage being less than the predetermined voltage value, and to maintain the connection state of the switch in response to the second voltage being greater than the predetermined voltage value.

4. The power supply circuit according to claim 1, wherein the control unit is configured to control the switch to switch the connection state, and control the voltage detection unit to detect the voltage of the connection port before and after the switch is switched, and to set the voltage of the connection port before the switch is switched as the first voltage, and set the voltage of the connection port after the switch is switched as the second voltage.

5. The power supply circuit according to claim 4, wherein the control unit is configured to report an error in response to both the first voltage and the second voltage being less than a predetermined voltage value, to keep the connection state of the changeover switch unchanged in response to both the first voltage being less than the predetermined voltage value and the second voltage being greater than the predetermined voltage value, to control the changeover switch to again switch the connection state in response to both the first voltage being greater than the predetermined voltage and the second voltage being less than the predetermined voltage, to control the changeover switch to switch the connection state after a predetermined time interval in response to both the first voltage and the second voltage being greater than the predetermined voltage value, and to control the voltage detection unit to re-detect the voltage of the connection port before and after the changeover of the changeover switch.

6. The power supply circuit of claim 5, wherein the predetermined time interval is 20 milliseconds.

7. Supply circuit according to claim 2 or 3 or 5, characterized in that the predetermined voltage value is 0.7 volt.

8. The power supply circuit of claim 1, further comprising:

the first switch is connected with the first power supply and the current-limiting resistor in series and used for connecting or disconnecting the first power supply and the current-limiting resistor with the change-over switch;

and the power supply branch circuit is connected with the first power supply, the current-limiting resistor and the first switch in parallel and is used for providing electric energy after the first switch is disconnected.

9. The power supply circuit of claim 8, wherein the power supply branch comprises:

a second power supply; and

and the second switch is connected with the second power supply in series and is used for connecting or disconnecting the second power supply with the change-over switch.

10. The power supply circuit according to claim 9, wherein the control unit is configured to control the first switch to be opened and control the second switch to be closed after keeping the connection state of the change-over switch unchanged.

11. A power receiving circuit, wherein the power receiving circuit is configured to receive power provided by the power supply circuit according to any one of claims 1-10; the power receiving circuit includes:

a receiving port having a third contact and a fourth contact for connecting to the connection port; and

a zener diode connected in series between the third contact and the fourth contact.