TWI737533B - Overvoltage protection circuit and usb type-c connector - Google Patents

Abstract

An overvoltage protection circuit includes a first connection pin, a second connection pin a third connection pin, a fourth connection pin, a cable power connection pin, a first switch, a second switch and a detection unit. A first fixed terminal of the first switch is coupled to the first connection pin. A first switching terminal of the first switch is switched between the cable power connection pin and the third connection pin. A second fixed terminal of the second switch is coupled to the second connection pin. A second switching terminal of the second switch is switched between the cable power connection pin and the fourth connection pin. The detection unit is configured to open both the first switch and the second switch when detecting a first pin voltage on the first connection pin or a second pin voltage on the second connection pin is greater than a threshold voltage.

Description

Overvoltage protection circuit and C-type universal serial bus connector

The present invention relates to overvoltage protection technology, in particular to an overvoltage protection circuit suitable for a C-type universal serial bus (USB Type-C) connector and a C-type universal serial bus connector with overvoltage protection.

The connector can be used for signal and power transmission between two electronic devices and is a common electronic component on each electronic device. In recent years, C-type universal serial bus (USB Type-C) connectors have been widely used because they can provide ultra-high-speed data transmission rates, and have the advantages of being lighter, thinner, shorter, and symmetrical in the plug-in interface. Applied to various electronic devices.

However, because the distance between the terminals in the C-type universal serial bus connector is very small, it is easy to cause a short circuit between the terminals due to foreign objects such as liquid or dust or improper use of plugging and unplugging. Generally speaking, the bus power terminal in the C-type universal serial bus connector can support a voltage of up to 20 volts, but the configuration channel terminal adjacent to the bus power terminal is only used to support a voltage of about 5 volts. Therefore, once the bus power terminal is short-circuited to the configuration channel terminal, a high voltage will appear on the configuration channel terminal, and this high voltage may damage the downstream circuit coupled to the configuration channel terminal.

In one embodiment, an over-voltage protection circuit includes a first connection pin, a second connection pin, a third connection pin, a fourth connection pin, a cable power pin, a first switch, a second switch, and a detection unit. The cable power pin is used to receive cable power. The first fixed end of the first switch is coupled to the first connection pin, and the first switch end of the first switch is switched between the cable power pin and the third connection pin. The second fixed end of the second switch is coupled to the second connection pin, and the second switch end of the second switch is switched between the cable power pin and the fourth connection pin. The detecting unit is used for detecting the voltage of the first pin on the first connecting pin and the voltage of the second pin on the second connecting pin. Moreover, when detecting that the voltage of the first pin or the voltage of the second pin is greater than the threshold voltage, the detecting unit causes the first switch and the second switch to open.

In one embodiment, a C-type universal serial bus connector includes a C-type universal serial bus connection interface, a control chip, and an overvoltage protection circuit. The C-type universal serial bus connection interface has a first configuration channel terminal and a second configuration channel terminal. The over-voltage protection circuit is coupled between the C-type universal serial bus connection interface and the control chip. The over-voltage protection circuit includes a first connection pin, a second connection pin, a third connection pin, a fourth connection pin, a cable power supply pin, a first switch, a second switch, and a detection unit. The first connecting pin is used for connecting the first configuration channel terminal of the C-type universal serial bus connection interface through the first connecting wire. The second connecting pin is used for connecting the second configuration channel terminal of the C-type universal serial bus connection interface through the second connecting wire. The third connecting pin is used for connecting the control chip through the third connecting wire. The fourth connection pin is used for connecting the control chip through the fourth connection line. The cable power pin is used to receive cable power. The first fixed end of the first switch is coupled to the first connection pin, and the first switch end of the first switch is switched between the cable power pin and the third connection pin. The second fixed end of the second switch is coupled to the second connection pin, and the second switch end of the second switch is switched between the cable power pin and the fourth connection pin. The detecting unit is used for detecting the voltage of the first pin on the first connecting pin and the voltage of the second pin on the second connecting pin. Moreover, when detecting that the voltage of the first pin or the voltage of the second pin is greater than the threshold voltage, the detecting unit causes the first switch and the second switch to open.

In order to make the above-mentioned objects, features and advantages of the embodiments of the present invention more obvious and understandable, the following detailed descriptions will be made in conjunction with the accompanying drawings.

It must be understood that the words "include", "include" and other words used in this manual are used to indicate the existence of specific technical features, values, method steps, operations, elements, and/or components, but they do not exclude Add more technical features, values, method steps, job processing, components, components, or any combination of the above.

Words such as "first", "second", "third", and "fourth" are used to modify elements, not to indicate the order of priority or antecedent relationship between them, but only to distinguish elements with the same name.

Figure 1 is a schematic diagram of the terminal configuration on the C-type universal serial bus connection interface, and Figure 2 is a schematic diagram of an embodiment of the C-type universal serial bus connector. Please refer to Figure 1 and Figure 2. Type-C Universal Serial Bus (USB Type-C) connector 100 is a connector for Universal Serial Bus (USB), regardless of whether the cable (not shown) is plugged in. Or it can be plugged in reversely, and the device connected to one end of the cable can establish normal communication with the device equipped with the C-type universal serial bus connector 100. In some implementation aspects, the device equipped with the C-type universal serial bus connector 100 may be, but not limited to, electronic devices such as mobile phones, laptops, desktop computers, mobile power supplies, and displays.

The C-type universal serial bus connector 100 may include a C-type universal serial bus connection interface 110 and a control chip 120, and the control chip 120 is coupled to the C-type universal serial bus connection interface 110. The universal serial bus connection interface 110 is used to connect with a cable, and the control chip 120 is used to control the universal serial bus connection interface 110 according to the communication standard.

Under the specifications of the C-type universal serial bus, the C-type universal serial bus connection interface 110 generally has twenty-four terminals, the upper row of terminals A1-A12 and the lower row of terminals B1-B12, respectively. Among them, the terminal A1, the terminal A12, the terminal B1, and the terminal B12 are ground terminals. Terminal A2, terminal A3, terminal A10, terminal A11, terminal B2, terminal B3, terminal B10, and terminal B11 are ultra-high-speed differential signal terminals. Terminal A4, terminal A9, terminal B4 and terminal B9 are bus power terminals. Terminal A5 and terminal B5 are configuration channel terminals. Terminal A8 and terminal B8 are terminals for sidebands. In addition, the terminal A6, the terminal A7, the terminal B6, and the terminal B7 are differential signal terminals. Since the function of each terminal is already well known by those with ordinary knowledge in the technical field of the present invention, it will not be repeated here.

Here, the channel terminals (namely, the terminal A5 and the terminal B5) are arranged next to the busbar power terminals (namely, the terminal A4 and the terminal B4). Generally speaking, the bus power terminal can support a voltage of up to 20 volts (V), but the configuration channel terminals (namely, terminals A5 and B5) are only used to support a voltage of about 5 volts. Due to the very small spacing between the terminals, the C-type universal serial bus connector 100 is prone to short-circuit when connecting and disconnecting the cable, which causes high voltage to appear on the terminals of the configuration channel and damages the coupling in the control chip 120. To configure the downstream circuit of the channel terminal. In some embodiments, the downstream circuit may be a power distribution controller (PD controller).

Based on this, the present invention provides an overvoltage protection circuit 130 suitable for the C-type universal serial bus connector 100 and a C-type universal serial bus connector 100 equipped with the overvoltage protection circuit 130. The C-type universal serial bus connector 100 includes a C-type universal serial bus connection interface 110, a control chip 120 and an overvoltage protection circuit 130. The over-voltage protection circuit 130 is coupled between the C-type universal serial bus connection interface 110 and the control chip 120, and the over-voltage protection circuit 130 can be used when a high voltage appears on the configuration channel terminal of the C-type universal serial bus connection interface 110 The electrical connection between the configuration channel terminal and the control chip 120 is disconnected to prevent the high voltage on the configuration channel terminal from damaging the downstream circuit in the control chip 120 coupled to the configuration channel terminal.

In one embodiment, the overvoltage protection circuit 130 includes a first connection pin 131, a second connection pin 132, a third connection pin 133, a fourth connection pin 134, a cable power pin 135, a first switch 136, and a Two switch 137 and detection unit 138.

The first connection pin 131 of the overvoltage protection circuit 130 can be connected to the first configuration channel terminal 111 of the C-type universal serial bus connection interface 110 through the first connection line 141, and the second connection pin 132 of the overvoltage protection circuit 130 can be It is connected to the second configuration channel terminal 112 of the C-type universal serial bus connection interface 110 through the second connection line 142. The first configuration channel terminal 111 and the second configuration channel terminal 112 are respectively one of the aforementioned terminals A5 and B5. For example, when the first configuration channel terminal 111 is the terminal A5, the second configuration channel terminal 112 is the terminal B5. Conversely, when the first configuration channel terminal 111 is the terminal B5, the second configuration channel terminal 112 is the terminal A5.

The third connection pin 133 of the overvoltage protection circuit 130 can be connected to the control chip 120 through the third connection line 143, and the fourth connection pin 134 of the overvoltage protection circuit 130 can be connected to the control chip 120 through the fourth connection line 144. In some embodiments, the over-voltage protection circuit 130 is a chip made by an integrated circuit process. The first connecting pin 131, the second connecting pin 132, the third connecting pin 133, the fourth connecting pin 134, and the cable power pin 135 are all chip pins. In addition, the first connection line 141, the second connection line 142, the third connection line 143, and the fourth connection line 144 may be printed circuit lines on a printed circuit board (PCB).

The cable power pin 135 of the overvoltage protection circuit 130 is used to receive the cable power Vconn. In one embodiment, the over-voltage protection circuit 130 may further include a cable power trace L1. The cable power trace L1 contains three ends. Wherein, the first terminal L1a is connected to the cable power pin 135, the second terminal L1b is used as one of the multiple switching connection points of the first switch 136, and the third terminal L1c is used as the second One of a plurality of switching connection points of the switch 137. In some embodiments, the cable power Vconn can be 5 volts or 3.3 volts. In addition, the cable power trace L1 can withstand at least 300 milliampere (mA) current.

The first switch 136 of the overvoltage protection circuit 130 has a first fixed terminal 136a and a first switch terminal 136b. The first fixed terminal 136 a of the first switch 136 is fixedly coupled to the first connection pin 131 of the overvoltage protection circuit 130. The first switching end 136b of the first switch 136 can be selectively switched between the cable power pin 135 (ie, the second end L1b of the cable power trace L1) and the third connecting pin 133.

Similarly, the second switch 137 of the overvoltage protection circuit 130 has a second fixed terminal 137a and a second switch terminal 137b. The second fixed terminal 137 a of the second switch 137 is fixedly coupled to the second connection pin 132 of the overvoltage protection circuit 130. The second switching end 137b of the second switch 137 can be selectively switched between the cable power pin 135 (ie, the third end L1c of the cable power trace L1) and the fourth connecting pin 134.

In an embodiment, the first switching switch 136 can selectively switch the first switching terminal 136 b to the cable power pin 135 or the third connecting pin 133 according to the first control signal output by the control chip 120. The second switch 137 can selectively switch the second switch terminal 137b to the cable power pin 135 or the fourth connection pin 134 according to the second control signal output by the control chip 120. For example, when the control chip 120 determines that it is a C-type universal serial bus connection interface 110, the first configuration channel terminal 111 is connected to the CC (Channel Configuration) end of the cable and the second configuration channel terminal 112 is connected to the electronics in the cable. In the case of a label chip (eMark IC), the first control signal output by the control chip 120 causes the first switching terminal 136b of the first switch 136 to be connected to the third connection pin 133, and the second control signal output by the control chip 120 This causes the second switching end 137b of the second switch 137 to be connected to the cable power pin 135, so that the cable power Vconn can be connected to the C-type universal serial bus via the second connection pin 132 of the overvoltage protection circuit 130 The connection path between the second configuration channel terminals 112 of the interface 110 supplies power to the electronic label chip in the cable. When the control chip 120 determines that the second configuration channel terminal 112 of the C-type universal serial bus connection interface 110 is connected to the CC end of the cable and the first configuration channel terminal 111 is connected to the electronic label chip in the cable, the control chip 120 The output second control signal will cause the second switching terminal 137b of the second switch 137 to be connected to the fourth connection pin 134, and the first control signal output by the control chip 120 will cause the first switch 136 of the first switch 136 The switching terminal 136b is connected to the cable power pin 135, so that the cable power Vconn can pass through the first connection pin 131 of the overvoltage protection circuit 130 to the first configuration channel terminal 111 of the C-type universal serial bus connection interface 110 The connection path of the cable supplies power to the electronic label chip in the cable. Here, since how the control chip 120 determines whether the first configuration channel terminal 111 or the second configuration channel terminal 112 is connected to the CC end of the cable is well known to those with ordinary knowledge in the art, it will not be repeated.

It should be noted that, in the embodiment of the present invention, the cable power Vconn can be output to the C-type universal serial bus connection interface 110 through only a switch. For example, the cable power Vconn can be output through the first switch 136. Output to the C-type universal serial bus connection interface 110, or output to the C-type universal serial bus connection interface 110 via the second switch 137. However, in the conventional C-type universal serial bus connector 200 including the universal serial bus connection interface 210, the control chip 220 and the overvoltage protection circuit 230, as shown in Figure 3, the cable power supply Vconn needs to pass through two The switch can be output to the C-type universal serial bus connection interface 210. For example, the cable power supply Vconn needs to pass through the switch 221 to the overvoltage protection circuit 230, and then output to the first configuration channel terminal 211 of the C-type universal serial bus connection interface 210 through the switch 231. For another example, it is necessary to first pass the switch 222 to the overvoltage protection circuit 230, and then output to the second configuration channel terminal 212 of the C-type universal serial bus connection interface 210 through the switch 232. Therefore, compared with the structure of the traditional C-type universal serial bus connector 200, the voltage drop of the cable power supply Vconn output by the present invention can be smaller.

The detection unit 138 of the overvoltage protection circuit 130 is coupled to the first connection pin 131 and the second connection pin 132, and the detection unit 138 can be used to detect the first pin voltage and the second connection on the first connection pin 131 The second pin voltage on pin 132. Moreover, when it is detected that the voltage of the first pin is greater than the threshold voltage or the voltage of the second pin is greater than the threshold voltage, the detection unit 138 will cause the first switch 136 and the second switch 137 to open, for example, causing the first switch 136 and the second switch 137 to open. The first switching terminal 136b of the switch 136 is neither connected to the cable power pin 135 nor connected to the third connection pin 133, so that the second switching terminal 137b of the second switch 137 is not connected to the cable power pin 135 It is also not connected to the fourth connecting pin 134, so as to prevent high voltage from damaging the downstream circuit. Therefore, the first switch 136 and the second switch 137 in the overvoltage protection circuit 130 not only provide a path switching function, but also provide an overvoltage protection function.

In some embodiments, the threshold voltage may be approximately 6 volts. However, the present invention is not limited to this. The threshold voltage may be determined by the maximum withstand voltage of the downstream circuit coupled to the third connection pin 133 and/or the fourth connection pin 134 of the overvoltage protection circuit 130.

In an embodiment, the control chip 120 may include a first configuration channel pin CC1, a second configuration channel pin CC2, a third switch 121, and a configuration channel logic control unit 122.

The first configuration channel pin CC1 of the control chip 120 can be used to couple to the third connection pin 133 of the overvoltage protection circuit 130, for example, through the third connection line 143. The second configuration channel pin CC2 of the control chip 120 can be used to couple to the fourth connection pin 134 of the overvoltage protection circuit 130, for example, through the fourth connection line 144.

The third switch 121 of the control chip 120 has a third fixed end 121a and a third switching end 121b. The third fixed terminal 121a of the third switch 121 is fixedly coupled to the configuration channel logic control unit 122, and the third switching terminal 121b of the third switch 121 can be selectively switched between the first configuration channel pin CC1 and the second configuration channel Between pins CC2.

The configuration channel logic control unit 122 can be used to control the switching of the third switching terminal 121b of the third switch 121 to utilize the first configuration channel pin CC1 and the second configuration channel pin CC2 by switching the third switch terminal 121b. Signal. For example, the configuration channel logic control unit 122 can know whether the cable is inserted into the C-type universal serial bus connector in a forward or reverse way according to the signal on the first configuration channel pin CC1 and/or the second configuration channel pin CC2 100. For another example, the configuration channel logic control unit 122 can transmit signals through the first configuration channel pin CC1 and/or the second configuration channel pin CC2. Herein, since the function of configuring the channel logic control unit 122 is already well known to those with ordinary knowledge in the art, it will not be repeated here.

It should be noted that since the switching of the output path of the cable power supply Vconn is already configured in the over-voltage protection circuit 130, there is no need to configure the cable power supply pins and the cable power supply wiring in the control chip 120 of the present invention. And a switch for switching the power path of the cable. In this way, the signal input to the configuration channel logic control unit 122 via the first configuration channel pin CC1 or the second configuration channel pin CC2, or the configuration channel logic control unit 122 outputs to the first configuration channel pin CC1 or the first configuration channel pin CC1 or The signals of the two configuration channel pins CC2 all only need to pass through one switch (ie, the third switch 121). However, in the conventional C-type universal serial bus connector 200, the signal input to the configuration channel logic control unit 224 via the pins of the control chip 220 needs to pass through two switches. For example, as shown in FIG. 3, it is necessary to pass through the switch 221 and the switch 223, or through the switch 222 and the switch 223.

In some embodiments, the over-voltage protection circuit 130 and the control chip 120 are chips manufactured through different integrated circuit manufacturing technologies. Here, since the cable power pin 135 for receiving the cable power Vconn and the cable power trace L1 are configured in the overvoltage protection circuit 130, the overvoltage protection circuit 130 can withstand the voltage of the cable power Vconn. Made by micron process technology. Since the control chip 120 does not need to be equipped with cable power pins and cable power traces, the control chip 120 can be manufactured by a more advanced manufacturing process, such as nano-process technology.

In some embodiments, the over-voltage protection circuit 130 can be made with 0.35 micron process technology. In addition, the control chip 120 can be made with 40nm process technology.

In summary, the embodiments of the present invention provide an overvoltage protection circuit and a C-type universal serial bus connector, which uses a detection unit to detect the voltage on the first pin or the voltage on the second pin The voltage of the second pin is used to open the first switch and the second switch when it is detected that the voltage of the first pin or the voltage of the second pin is greater than the threshold voltage, so as to prevent the high voltage from damaging the downstream circuit. In addition, in an embodiment of the present invention, the cable power pin is arranged in an overvoltage protection circuit made with micron process technology. Therefore, the control chip in this case does not need to be equipped with cable power pins and cable power traces, but can be made with a more advanced process, such as nano-process technology, so that the control chip has a smaller size. Large area and low production cost. Furthermore, the cable power supply in the embodiment of the present invention can be output to the C-type universal serial bus connection interface through a switch, so the voltage drop of the cable power supply can be smaller than that of the traditional architecture.

The embodiments of the present invention are disclosed as above, but they are not intended to limit the scope of the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the embodiments of the present invention. Therefore, the protection scope of the present invention shall be subject to those defined by the attached patent application scope.

100: C-type universal serial bus connector 111: First configuration channel terminal 112: Second configuration channel terminal 110: C-type universal serial bus connection interface 120: control chip 121: third switch 121a: third fixed end 121b: third switching terminal 122: Configure channel logic control unit 130: Overvoltage protection circuit 131: first connecting pin 132: second connecting pin 133: third connecting pin 134: Fourth connecting pin 135: Cable power pin 136: The first switch 136a: The first fixed end 136b: the first switching end 137: The second switch 137a: second fixed end 137b: second switching end 138: Detection Unit 141: The first connection line 142: Second connection line 143: Third connection line 144: Fourth connection line 200: Traditional C-type universal serial bus connector 210: C-type universal serial bus connection interface 211: First configuration channel terminal 212: Second configuration channel terminal 220: control chip 221: Toggle switch 222: Toggle switch 223: Toggle switch 224: Configure channel logic control unit 230: Overvoltage protection circuit 231: Switch 232: switch A1~A12: Terminal B1~B12: terminal CC1: The first configuration channel pin CC2: second configuration channel pin L1: Cable power routing L1a: first endpoint L1b: second endpoint L1c: third endpoint Vconn: cable power supply

Figure 1 is a schematic diagram of the terminal configuration on the C-type universal serial bus connection interface. Figure 2 is a schematic diagram of an embodiment of the C-type universal serial bus connector. Figure 3 is a schematic diagram of an embodiment of a conventional C-type universal serial bus connector.

without

100: C-type universal serial bus connector

111: First configuration channel terminal

112: Second configuration channel terminal

110: C-type universal serial bus connection interface

120: control chip

121: third switch

121a: third fixed end

121b: third switching terminal

122: Configure channel logic control unit

130: Overvoltage protection circuit

131: first connecting pin

132: second connecting pin

133: third connecting pin

134: Fourth connecting pin

135: Cable power pin

136: The first switch

136a: The first fixed end

136b: the first switching end

137: The second switch

137a: second fixed end

137b: second switching end

138: Detection Unit

141: The first connection line

142: Second connection line

143: Third connection line

144: Fourth connection line

CC1: The first configuration channel pin

CC2: second configuration channel pin

L1: Cable power routing

L1a: first endpoint

L1b: second endpoint

L1c: third endpoint

Vconn: cable power supply

Claims (10)

An overvoltage protection circuit, including: A first connecting pin; A second connecting pin; A third connecting pin; A fourth connecting pin; A cable power pin for receiving a cable power; A first switch, the first fixed end of the first switch is coupled to the first connection pin, and the first switch end of the first switch is switched between the cable power pin and the third connection pin between; A second switch, the second fixed end of the second switch is coupled to the second connection pin, and the second switch end of the second switch is switched between the cable power pin and the fourth connection pin Between; and A detecting unit for detecting a first pin voltage on the first connecting pin and a second pin voltage on the second connecting pin, and detecting the first pin voltage or the When the voltage of the second pin is greater than a threshold voltage, the detection unit causes the first switch and the second switch to open. For the overvoltage protection circuit described in item 1 of the scope of patent application, when the first switching terminal is connected to the cable power pin, the second switching terminal is connected to the fourth connecting pin, and when the second When the switching end is connected to the cable power pin, the first switching end is connected to the third connecting pin. The overvoltage protection circuit described in item 1 of the scope of patent application, wherein the overvoltage protection circuit is suitable for a C-type universal serial bus connector, and the C-type universal serial bus connector includes a C-type universal serial bus Connection interface and a control chip, the first connection pin is used to connect a first configuration channel terminal of the C-type universal serial bus connection interface, and the second connection pin is used to connect the C-type universal serial bus connection interface A second configuration channel terminal, and the third connection pin and the fourth connection pin are used for connecting the control chip. The overvoltage protection circuit described in item 3 of the scope of patent application, wherein the control chip includes: A first configuration channel pin for coupling to the third connection pin; A first configuration channel pin for coupling to the fourth connection pin; A third switch, the third switch end of the third switch is switched between the first configuration channel pin and the first configuration channel pin; and A configuration channel logic control unit is coupled to the third fixed terminal of the third switch, and the configuration channel logic control unit is used to control the switching of the third switch terminal of the third switch. In the over-voltage protection circuit described in item 3 of the scope of patent application, the over-voltage protection circuit and the control chip are manufactured through different process technologies. The over-voltage protection circuit described in item 5 of the scope of patent application, wherein the over-voltage protection circuit is made through micron process technology, and the control chip is made through nano process technology. The over-voltage protection circuit as described in item 6 of the scope of patent application, wherein the over-voltage protection circuit is made through a 0.35 micron process technology. In the over-voltage protection circuit described in item 7 of the scope of patent application, the control chip is made by 40nm process technology. The overvoltage protection circuit according to any one of items 1 to 8 of the scope of patent application, wherein the cable power supply is a voltage of 5 volts or 3.3 volts, and the threshold voltage is 6 volts. A C-type universal serial bus connector, including: A C-type universal serial bus connection interface with a first configuration channel terminal and a second configuration channel terminal; A control chip; and An over-voltage protection circuit is coupled between the C-type universal serial bus connection interface and the control chip, and the over-voltage protection circuit includes: A first connecting pin connected to the first configuration channel terminal through a first connecting wire; A second connecting pin, connected to the second configuration channel terminal through a second connecting wire; A third connecting pin, connected to the control chip through a third connecting wire; A fourth connection pin, connected to the control chip through a fourth connection line; A cable power pin for receiving a cable power; A first switch, the first fixed end of the first switch is coupled to the first connection pin, and the first switch end of the first switch is switched between the cable power pin and the third connection pin between; A second switch, the second fixed end of the second switch is coupled to the second connecting pin, and the second switch end of the second switch is switched to the cable power pin according to a second control signal And the fourth connecting pin; and A detecting unit for detecting a first pin voltage on the first connecting pin and a second pin voltage on the second connecting pin, and detecting the first pin voltage or the first pin voltage When the voltage of the two pins is greater than a threshold voltage, the detection unit causes the first switch and the second switch to open.

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