Protection circuit and charging device

Abstract

The present disclosure simply secures safety with respect to a leakage current to a human body. A protection circuit is provided between an exposed contact positive electrode terminal, a first contact negative electrode terminal, and a second contact negative electrode terminal, and a positive electrode terminal of a power output unit and a ground terminal, and is provided with: a P-type MOSFET; a first circuit connecting the contact positive terminal with a drain terminal of the P-type MOSFET; a second circuit having a positive terminal connected to a source terminal of the P-type MOSFET; a first N type MOSFET; a third circuit connecting the second contact negative terminal to the drain terminal of the first N-type MOSFET and grounded; a fourth circuit connecting a ground terminal to a source terminal of the first N-type MOSFET; a fifth circuit connecting the first contact negative terminal and the fourth circuit via a resistor; a sixth circuit connecting the gate terminal of the P-type MOSFET and the fifth circuit between the first contact negative terminal and the resistor; and a seventh circuit connecting a gate terminal of the first N-type MOSFET and the fifth circuit between the sixth circuit and the resistor.

Description

Technical Field

[0001] The invention relates to a protection circuit and a charging device comprising the protection circuit. Background Art

[0002] Conventionally, when charging an electronic device having a built-in secondary battery, a configuration is adopted in which the state of the secondary battery is confirmed using three terminals and then charging is started.

[0003] In a charger for charging such a secondary battery, safety is ensured against leakage current from the exposed terminal portion to the human body as a result (see Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 11-178220 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] However, in such a configuration, components and circuits are required on the charger side for receiving information such as the voltage value and temperature of the secondary battery, resulting in a complicated configuration.

[0009] In view of the above-mentioned prior art, an object of the present invention is to provide a technology capable of ensuring safety against leakage current to the human body with a simple structure.

[0010] Solutions to the problem

[0011] In order to solve the above-mentioned problem, the present invention is a protection circuit, which connects a contact positive terminal, a first contact negative terminal, and a second contact negative terminal to a positive terminal and a ground terminal, wherein the contact positive terminal, the first contact negative terminal, and the second contact negative terminal are exposed to the outside in a connector portion for connecting to a device having a secondary battery, and the positive terminal and the ground terminal are provided in a power output portion, and the power output portion outputs power supplied to the secondary battery via the contact positive terminal, the first contact negative terminal, and the second contact negative terminal, and the protection circuit is characterized in that it has:

[0012] A P-type MOSFET connected between the contact positive terminal and the positive terminal;

[0013] A first circuit connects the contact positive terminal to the drain terminal of the P-type MOSFET;

[0014] a second circuit, connecting the positive terminal to the source terminal of the P-type MOSFET;

[0015] a first N-type MOSFET connected between the second contact negative terminal and the ground terminal;

[0016] A third circuit connects the second contact negative terminal to the drain terminal of the first N-type MOSFET and to ground;

[0017] a fourth circuit, connecting the ground terminal to a source terminal of the first N-type MOSFET;

[0018] a fifth circuit, connecting the first contact negative terminal to the fourth circuit or the second circuit via a resistor;

[0019] a sixth circuit connecting the gate terminal of the P-type MOSFET to the fifth circuit between the first contact negative terminal and the resistor; and

[0020] The seventh circuit connects the gate terminal of the first N-type MOSFET and the fifth circuit between the sixth circuit and the resistor.

[0021] Accordingly, even if a person contacts at least any two of the contact positive terminal, the first contact negative terminal, and the second contact negative terminal exposed to the outside, and at least any two of the contacted terminals are electrically connected via the human body, leakage current will not flow through the human body, or will be limited to only a weak leakage current. Therefore, safety can be ensured by using a simple structure that does not require a complex structure such as a control unit, a P-type MOSFET, a first N-type MOSFET, a second N-type MOSFET, and passive components.

[0022] In addition, in the present invention, it may also be provided with:

[0023] A second N-type MOSFET, connected between the second circuit and the fourth circuit;

[0024] an eighth circuit, connecting the drain terminal of the second N-type MOSFET to the second circuit;

[0025] a ninth circuit, connecting a source terminal of the second N-type MOSFET to the fourth circuit; and

[0026] The grounding circuit grounds the gate terminal of the second N-type MOSFET.

[0027] Furthermore, the present invention is a charging device, which includes the protection circuit described above, and is characterized in that:

[0028] In the connector portion, the contact positive electrode terminal, the first contact negative electrode terminal, and the second contact negative electrode terminal are arranged asymmetrically.

[0029] According to this, the contact positive terminal, the first contact negative terminal, and the second contact negative terminal are arranged asymmetrically, so that it is possible to prevent an electronic device having a corresponding terminal arrangement from being connected in an incorrect direction.

[0030] Furthermore, the present invention is a charging device, which includes the protection circuit described above, and is characterized in that:

[0031] In the connector portion, the first negative contact terminal and the second negative contact terminal are arranged symmetrically with respect to the positive contact terminal.

[0032] Accordingly, the first negative contact terminal and the second negative contact terminal are symmetrically arranged relative to the positive contact terminal. Therefore, for an electronic device having a terminal configuration corresponding thereto, even if the first negative contact terminal and the second negative contact terminal are connected in the opposite manner relative to the positive contact terminal, the charger and the electronic device can be properly electrically connected to charge the secondary battery.

[0033] Effects of the Invention

[0034] According to the present invention, safety against leakage current to a human body can be ensured with a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a circuit diagram of the charger of Example 1.

[0036] Figure 2 1 is a circuit diagram showing a normal connection state between the charger and the electronic device of the first embodiment.

[0037] Figure 3 1 is a diagram showing the electrical connection between the charger and a person according to the first embodiment.

[0038] Figure 4 1 is a diagram showing other electrical connections between the charger of Example 1 and a person.

[0039] Figure 5 1 is a diagram showing other electrical connections between the charger of Example 1 and a person.

[0040] Figure 6 1 is a diagram showing other electrical connections between the charger of Example 1 and a person.

[0041] Figure 7 This is a circuit diagram of a charger according to a variation of the first embodiment.

[0042] Figure 8 It is a diagram showing the arrangement of terminals in the charger according to the embodiment.

[0043] Fig. 9It is a diagram showing another arrangement of terminals in the charger according to the embodiment. DETAILED DESCRIPTION

[0044] Hereinafter, specific embodiments of the present invention will be described based on the drawings.

[0045] <Example 1>

[0046] Hereinafter, an example of an embodiment of the present invention will be described. However, unless otherwise specified, the size, material, shape, relative arrangement, etc. of the components described in this embodiment are not intended to limit the scope of the present invention to these.

[0047] (Charger structure)

[0048] Figure 1 1 is a circuit diagram of the charger 100 including the protection circuit 200 according to the first embodiment.

[0049] The charger 100 is connected to an electronic device 400 having a secondary battery, and supplies power to the secondary battery. The charger 100 has a connector portion 110 connected to the electronic device 400. Terminals T1, T2, and T3 are provided in the connector portion 110, which are exposed to the outside and are electrically connected to terminals T21, T22, and T23 on the electronic device 400 side, respectively. Here, the charger 100, the connector portion 110, and the protection circuit 200 are respectively equivalent to the charging device, the connector portion, and the protection circuit of the present invention. In addition, the electronic device 400 is equivalent to the device of the present invention. In addition, the terminal T1, the terminal T2, and the terminal T3 are respectively equivalent to the contact positive terminal, the first contact negative terminal, and the second contact negative terminal of the present invention.

[0050] The protection circuit 200 is provided between the terminal T1, the terminal T2, and the terminal T3 and the positive terminal T4 and the ground terminal T5 of the output unit 300. The output unit 300 is electrically connected via the protection circuit 200 and the terminal T1, the terminal T2, and the terminal T3, and outputs power to the secondary battery of the electronic device 400. The output unit 300 can be any component or circuit that can output power to the protection circuit 200 via the positive terminal T4, for example, it can be a power conversion device such as a converter connected to a commercial power system, or a connector connected thereto. Here, the output unit 300 is equivalent to the power output unit of the present invention.

[0051] The terminal T1 is connected to the drain terminal of a p-channel enhancement type metal oxide film field effect transistor (p-MOSFET) Tr1 through a circuit Ln1. In the circuit Ln1, a resistor R1 is connected in series between the terminal T1 and the drain terminal of the p-MOSFETTr1. In addition, the source terminal of the p-MOSFETTr1 is connected to the positive terminal T4 of the output unit 300 through a circuit Ln2. In the circuit Ln2, a fuse F is connected between the positive terminal T4 and the source terminal of the p-MOSFETTr1. Here, the p-MOSFETTr1 is equivalent to the P-type MOSFET of the present invention, and the circuit Ln1 and the circuit Ln2 are respectively equivalent to the first circuit and the second circuit of the present invention.

[0052] A diode D11 is connected in parallel between the source terminal and the drain terminal of the p-MOSFET Tr1 so as to be forward from the drain terminal to the source terminal. A bidirectional TVS (transient voltage suppression) diode D12 is connected in parallel between the gate terminal and the source terminal of the p-MOSFET Tr1.

[0053] The terminal T3 is connected to the drain terminal of the n-channel enhancement type MOSFET (n-MOSFET) Tr2 through the circuit Ln3. In the circuit Ln3, a resistor R2 is connected in series between the terminal T3 and the drain terminal of the n-MOSFETTr2. In addition, the source terminal of the n-MOSFETTr2 is connected to the ground terminal T5 of the output unit 300 through the circuit Ln4. Here, the n-MOSFETTr2 is equivalent to the first N-type MOSFET of the present invention. In addition, the circuit Ln3 and the circuit Ln4 are respectively equivalent to the third circuit and the fourth circuit of the present invention.

[0054] A diode D21 is connected in parallel between the source terminal and the drain terminal of the n-MOSFETTr2 so as to be forward from the source terminal to the drain terminal. A bidirectional TVS (transient voltage suppression) diode D22 is connected in parallel between the gate terminal and the source terminal of the n-MOSFETTr2.

[0055] Terminal T2 is connected to circuit Ln4 via circuit Ln5. For circuit Ln5 having one end connected to terminal T2, the other end of circuit Ln5 is connected to circuit Ln4 at connection point P5 via resistor R3 connected in series. In addition, circuit Ln6 having one end connected to the gate terminal of p-MOSFETTr1 is connected to circuit Ln5 at connection point P6 at the other end. In addition, circuit Ln7 having one end connected to the gate terminal of n-MOSFETTr2 is connected to circuit Ln5 at connection point P7 at the other end. At this time, connection point P6 and connection point P7 are arranged between terminal T2 and resistor R3. Here, circuit Ln5 is equivalent to the fifth circuit of the present invention, and resistor R3 is equivalent to the resistor of the present invention. In addition, circuit Ln6 and circuit Ln7 are respectively equivalent to the sixth circuit and seventh circuit of the present invention.

[0056] An n-MOSFETTr3 is connected between the circuit Ln2 and the circuit Ln4. The other end of the circuit Ln8 connected to the drain terminal of the n-MOSFETTr3 is connected to the circuit Ln2 at the connection point P8. The connection point P8 is arranged between the source terminal of the p-MOSFETTr1 and the fuse F on the circuit Ln2. In addition, the other end of the circuit Ln9 connected to the source terminal of the n-MOSFETTr3 is connected to the circuit Ln4 at the connection point P9. The gate terminal of the n-MOSFETTr3 is grounded through the circuit Ln10. Here, the n-MOSFETTr3 is equivalent to the second N-type MOSFET of the present invention. In addition, the circuit Ln8, the circuit Ln9 and the circuit Ln10 are respectively equivalent to the eighth circuit, the ninth circuit and the grounding circuit of the present invention.

[0057] A diode D31 is connected in parallel between the source terminal and the drain terminal of the n-MOSFETTr3 so as to be forward from the source terminal to the drain terminal. In addition, a bidirectional TVS (transient voltage suppression) diode D32 is connected in parallel between the gate terminal and the source terminal of the n-MOSFETTr3.

[0058] The circuit Ln1 and the circuit Ln3 are connected via the circuit Ln10 to which the capacitor C1 is connected in series. One end of the circuit Ln10 is connected to the circuit Ln1 at a connection point P1 disposed between the terminal T1 and the resistor R1. Furthermore, the other end of the circuit Ln10 is connected to the circuit Ln3 at a connection point P2 disposed between the terminal T3 and the resistor R2. The circuit Ln3 is grounded between the connection point P2 and the terminal T3.

[0059] The circuit Ln2 and the circuit Ln4 are connected via the circuit Ln11 to which the capacitor C2 is connected in series. One end of the circuit Ln11 is connected to the circuit Ln2 at a connection point P3 disposed between the connection point P8 and the fuse F. In addition, the other end of the circuit Ln11 is connected to the circuit Ln4 at a connection point P4 disposed between the connection point P9 and the ground terminal T5.

[0060] Figure 2 1 is a circuit diagram showing a part of the structure of the electronic device 400 including the terminal T21, the terminal T22, and the terminal T23. The terminal T21 is connected to the charging terminal ChT through the circuit Ln21. In the circuit Ln21, the fuse F41 and the inductor L41 are connected in series in sequence from the terminal T21 side. The terminal T22 is connected to the circuit Ln21 via the circuit Ln22. On the circuit Ln22, the inductor L42, the inductor L43, and the resistor R41 are connected in series in sequence from the terminal T22 side. The circuit Ln22 is grounded via the bidirectional TVS diode D42 at the connection point P43 between the inductor L43 and the resistor R41. In addition, at the connection point P41 between the circuit Ln22 and the circuit Ln21 and the connection point P42 between the inductor L41, the circuit Ln21 is grounded via the bidirectional TVS diode D41. And, the terminal T23 is grounded through the circuit Ln23. In the circuit Ln23, an inductor L44 and an inductor L45 are connected in series in this order from the terminal T23 side.

[0061] first, Figure 3 1 shows a state where a person 500 contacts the terminal T1 and the terminal T2 of the charger 100. At this time, the potential of the circuit Ln2 is 5V, and the gate voltage VGS of the p-MOSFETTr1 is -5V, so the p-MOSFETTr1 is turned on. As a result, the current flows through the person 500 to the resistor R3 of the charger 100. However, by setting the resistance value of the resistor R3 to 100kΩ, for example, the current flowing through the person 500 becomes 5V / 100kΩ=50μA, and the leakage current can be suppressed to a level less than 100μA, which is the standard in medical equipment, so that no leakage current dangerous to the human body flows.

[0062] Figure 4 , a person 500 touches the terminal T1 and the terminal T3 of the charger 100. At this time, since a voltage drop such that the gate voltage VGS exceeds the threshold value does not occur in the p-MOSFET Tr1, the p-MOSFET Tr1 is in the off state, and no current flows to the person 500.

[0063] Figure 5 2 shows a state where a person 500 is in contact with the terminal T2 and the terminal T3 of the charger 100. At this time, no voltage is applied to the person 500 and no current flows through the person 500.

[0064] Figure 6 The state in which a person 500 contacts the terminal T1, the terminal T2, and the terminal T3 of the charger 100 is shown in FIG. For example, if these three terminals are in contact with a part of the surface of the person 500 that is wetted by liquid, or if the three terminals of the charger 100 are accidentally immersed in water in a bathroom, etc., such a state will occur. At this time, since the gate voltage VGS of the p-MOSFETTr1 is -5V, the p-MOSFETTr1 is turned on. Then, the current flows through the resistor R3. Due to the voltage drop generated in the resistor R3, the gate voltage VGS of the n-MOSFETTr3 exceeds the threshold, and the n-MOSFETTr3 is turned on. Therefore, when the current flows through the circuit Ln2 via the n-MOSFETTr3, the fuse F becomes disconnected and the operation of the charger 100 stops. Therefore, the current will not continue to flow to the person 500. However, in order to achieve such an action, the threshold of the n-MOSFETTr3 is lower than the threshold of the n-MOSFETTr2, and a component with a fast switching speed needs to be selected.

[0065] As described above, according to the first embodiment, the protection circuit 200 having a simple structure composed of passive components and transistors can ensure safety against leakage current to the human body.

[0066] <Modification>

[0067] Figure 7 2 is a circuit diagram of a charger 101 according to a modified example including a protection circuit 201. The same reference numerals are used for the same configurations as those of the protection circuit 200 according to the first embodiment, and detailed descriptions thereof are omitted.

[0068] In the protection circuit 201, the other end of the circuit Ln5 connected to the terminal T2 is not connected to the circuit Ln4, but is connected to the circuit Ln2 connecting the source terminal of the p-MOSFETTr1 and the positive terminal T4 between the source terminal of the p-MOSFETTr1 and the connection point P8. Here, the circuit Ln5 corresponds to the fifth circuit of the present invention.

[0069] In the protection circuit 201 of such a structure, p-MOSFETTr1, n-MOSFETTr2, and n-MOSFETTr3 are also turned on and off by the same mechanism as the protection circuit 200 of the first embodiment, so the same effect can be obtained. Therefore, according to this variation, the safety against leakage current to the human body can be ensured by the protection circuit 201 of a simple structure composed of passive components and transistors.

[0070] Figure 8, an example of the configuration structure of the terminal T1, the terminal T2, and the terminal T3 in the connector part 110 of the charger 100 is shown. The charger 100 includes a flat, substantially rectangular housing 120 and a cable 130. One end of the cable 130 is connected to the housing 120, and the other end is connected to a power source such as an AC adapter. In the planar connector part 110 formed on one side of the housing 120, the terminal T2, the terminal T1, and the terminal T3 are sequentially arranged from the cable 130 side along the axis Ax1 in the long dimension direction of the connector part 110. Furthermore, the terminal T1, the terminal T2, and the terminal T3 are asymmetrically arranged with respect to the axis Ax1 in the long dimension direction of the connector part 110. That is, the terminal T1 is arranged on one side of the axis Ax1, and the terminal T2 and the terminal T3 are arranged on the other side of the axis Ax1. In order to contact the terminals T1, T2 and T3 on the charger 100 side, the terminals T21, T22 and T23 of the electronic device 400 are also arranged asymmetrically with respect to the axis of the arrangement direction. Therefore, even if you want to connect the connector part 110 of the electronic device 400 and the charger 100 in the opposite direction relative to the arrangement direction of their respective terminals, they cannot be properly connected, thereby preventing the electronic device 400 and the charger 100 from being connected in the wrong direction.

[0071] <Charger Structure>

[0072] Hereinafter, the arrangement structure of the terminal T1, the terminal T2, and the terminal T3 in the charger 100 including the protection circuit 200 will be described. The charger 101 including the protection circuit 201 can also adopt the following structure, so a separate description is omitted.

[0073] Fig. 9 FIG. 2 shows an example of the configuration of the terminal T1, the terminal T2, and the terminal T3 in the connector portion 110 of the charger 100. Figure 8Similarly, it includes a flat, roughly rectangular housing 120 and a cable 130. One end of the cable 130 is connected to the housing 120, and the other end is connected to a power source such as an AC adapter. In the planar connector portion 110 formed on one side of the housing 120, the terminal T2, the terminal T1, and the terminal T3 are arranged in sequence from the cable 130 side along the axis Ax1 in the long dimension direction of the connector portion 110. Moreover, the terminal T1 and the terminal T2 and the terminal T3 are arranged symmetrically with respect to the axis Ax1 in the long dimension direction of the connector portion 110. In addition, at this time, the terminal T1 is set as the positive electrode, and the terminal T2 and the terminal T3 are both set as the negative electrode, so that the terminal T1 as the positive electrode and the terminal T2 and the terminal T3 as the negative electrode are arranged symmetrically with respect to the axis Ax2 in the direction orthogonal to the long dimension direction. Therefore, in order to contact the terminals T1, T2, and T3 on the charger 100 side, the terminals T21, T22, and T23 of the electronic device 400 are also symmetrically arranged with respect to the axis Ax1 of the arrangement direction, and the terminals T21, T22, and T23 are symmetrically arranged with respect to the axis Ax2 in the direction orthogonal to the arrangement direction. With such an arrangement, even if the connectors 110 of the electronic device 400 and the charger 100 are connected in the opposite direction with respect to the arrangement direction of their respective terminals, they can be properly connected, so that the electronic device 400 and the charger 100 can be connected without paying attention to the orientation, and the situation that the connection in the wrong orientation and the inability to properly connect will not occur.

[0074] Description of Reference Numerals

[0075] 100, 101: charger;

[0076] 110: connector part;

[0077] 200, 201: protection circuit;

[0078] 300: output unit;

[0079] 400: Electronic equipment;

[0080] T1, T2, T3: terminals.

Claims

1. A protection circuit, connecting a contact positive terminal, a first contact negative terminal and a second contact negative terminal to a positive terminal and a ground terminal, wherein: The contact positive terminal, the first contact negative terminal, and the second contact negative terminal are exposed to the outside in a connector portion for connecting to a device having a secondary battery, the positive terminal and the ground terminal are provided in a power output portion, and the power output portion outputs power supplied to the secondary battery via the contact positive terminal, the first contact negative terminal, and the second contact negative terminal, and the protection circuit is characterized in that it comprises: A P-type MOSFET connected between the contact positive terminal and the positive terminal; A first circuit connects the contact positive terminal to the drain terminal of the P-type MOSFET; a second circuit, connecting the positive terminal to the source terminal of the P-type MOSFET; a first N-type MOSFET connected between the second contact negative terminal and the ground terminal; A third circuit connects the second contact negative terminal to the drain terminal of the first N-type MOSFET and to ground; a fourth circuit, connecting the ground terminal to a source terminal of the first N-type MOSFET; a fifth circuit, connecting the first contact negative terminal to the fourth circuit or the second circuit via a resistor; a sixth circuit, connecting the gate terminal of the P-type MOSFET to the fifth circuit between the first contact negative terminal and the resistor; and The seventh circuit connects the gate terminal of the first N-type MOSFET and the fifth circuit between the sixth circuit and the resistor.

2. The protection circuit according to claim 1, characterized in that: The protection circuit comprises: A second N-type MOSFET, connected between the second circuit and the fourth circuit; an eighth circuit, connecting the drain terminal of the second N-type MOSFET to the second circuit; a ninth circuit, connecting a source terminal of the second N-type MOSFET to the fourth circuit; and The grounding circuit grounds the gate terminal of the second N-type MOSFET.

3. A charging device, comprising the protection circuit according to claim 1 or 2, characterized in that: In the connector portion, the contact positive electrode terminal, the first contact negative electrode terminal, and the second contact negative electrode terminal are arranged asymmetrically.

4. A charging device, comprising the protection circuit according to claim 1 or 2, characterized in that: In the connector portion, the first negative contact terminal and the second negative contact terminal are arranged symmetrically with respect to the positive contact terminal.

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