JP2017203727A - Short circuit detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect various short-circuit states generated between a short-circuit detection target and a terminal. A short-circuit detection circuit 104 is connected to a conductive connector shell 111 with a connector shell wire 205, which detects a short circuit between the connector shell 111 and a power supply terminal 113a or a GND terminal 113b, and a predetermined voltage. And a resistor 201a, 201b of a voltage dividing circuit that changes the potential of the connector shell wire 205 based on the control of the supply of the power source B of the FET 203. A short circuit between the terminal 113a and the connector shell 111 is detected, and a short circuit between the GND terminal 113b and the connector shell 111 is detected with the potential of the connector shell wire 205 set to a predetermined potential. [Selection diagram] Figure 2

Description

  The present invention relates to a short detection circuit that detects a short between a shell and a terminal of a connector of an electronic device.

  In recent years, in mobile phones (electronic devices) such as smartphones that have been rapidly spread, charging connectors without caps have been increased to improve operability. However, foreign objects can easily enter the connectors with this capless connectors. Become. In the case of a conductive foreign material, the power source terminal and the conductive connector shell are short-circuited by the foreign material. When a voltage is applied to the power supply terminal by charging the electronic device in this short state, an excessive current flows from the power supply terminal to the board of the electronic device via the connector shell, which leads to burnout of the connector or burns to the user. May cause fever.

  As a countermeasure, it is considered that the conductive connector shell is not directly grounded to the GND of the board, thereby preventing a current from flowing to the board even if the power supply terminal and the conductive connector shell are short-circuited (for example, (See Non-Patent Document 1 below.)

  Further, voltage dividing resistors R1 and R2 are connected between the body of the automobile to be detected as a short circuit and the power supply line, and between the short detection object and the GND line, respectively, and the potential of the short detection object is compared with a reference value, and the power line Or the technique which determines a GND line and contact is proposed (for example, refer the following patent document 1). Moreover, in portable lighting equipment in which a charging terminal is exposed on the outer surface of the metal, a technique has been proposed in which a short-circuit protection circuit is connected to the charging terminal, and one charging terminal is disconnected from the battery by a short circuit between the charging terminals ( For example, see the following Patent Document 2.)

JP 2001-103652 A Special table 2008-523780

Search on April 20, 2016, URL: http: // www. mcpc-jp. org / press / pdf / TR-021_141008. pdf, “USB Charging Interface Safety Design Guidelines Version 1.00”, p10, “Appendix B. Half-short error between charging terminals and countermeasure examples, B.2 Countermeasure examples for charged devices”

  However, the conventional technology can only detect short-circuit between the short detection target (connector shell, body, etc.) and the power supply terminal (power supply line and GND), and between the short-circuit detection target and the power supply line and GND line to which the voltage is applied. A resistive short cannot be detected.

  For example, in the technique of Non-Patent Document 1, when conductive foreign matter enters between the connector shell and the GND terminal of the connector, a current flows from the power supply terminal to which voltage is applied by charging or power feeding to the GND via the connector shell. I can't prevent you from continuing.

  In the technique of Patent Document 1, since a short circuit is detected using a voltage dividing resistor, a resistor having the same resistance value ratio as R1 and R2 between the short detection target and the power supply line and between the short detection target and the GND line. When a sexual short occurs, the potential of the short detection target is the same before and after contact, and it is not possible to determine the presence or absence of the short. For example, it is impossible to detect when a power supply terminal and a GND terminal are short-circuited via a short detection target (for example, a connector shell). When R1 = R2, the short detection target, the power supply line, and the GND line are wet with the electrolyte solution (seawater, etc.), the resistance value r1 due to the resistive short between the short detection target and the power supply line, and between the short detection target and the GND line If the resistance value r2 due to the resistance short circuit is the same, the determination cannot be made.

  Furthermore, in Patent Document 1, since a pull-up voltage is constantly applied to the short detection target, there is a possibility that the short detection target may be corroded when it touches the electrolyte solution. Furthermore, since a current always flows from the power supply line to the GND line via a voltage dividing resistor even in the absence of a short circuit and consumes power, it is not suitable for application to an electronic device such as a portable terminal that requires power saving.

  Further, the technique of Patent Document 2 can only detect a short between two terminals, and cannot detect a short between a connector shell, a power supply line, and a GND line.

  In one aspect, an object of the present invention is to easily detect various short-circuit states that occur between a short detection target and a terminal.

  In one proposal, a short detection circuit is provided in an electronic device, and the connector shell includes a conductive connector shell, a power supply terminal, and a short detection circuit that detects a short state of an external terminal connector having a GND terminal. A connector shell wire that is electrically connected to the connector shell, a short detection element that detects a short circuit between the power supply terminal or the GND terminal, and control of whether or not a power supply of a predetermined voltage is supplied. A resistance voltage dividing circuit that changes the potential of the connector shell, and the short detection element detects a short circuit between the power supply terminal and the connector shell in a state where the shell potential of the connector shell wire is 0 V, and the connector A short circuit between the GND terminal and the connector shell is detected with the shell wire potential set to a predetermined potential. It is a requirement Rukoto.

  According to one embodiment, there is an effect that various short states occurring between the short detection target and the terminal can be easily detected.

FIG. 1 is a diagram illustrating a hardware configuration example of the electronic apparatus according to the first embodiment. FIG. 2 is a circuit diagram illustrating a configuration example of the short detection circuit according to the first embodiment. FIG. 3 is an operation diagram illustrating various short detection states of the short detection circuit according to the embodiment. (Part 1) FIG. 4 is an operation diagram illustrating various short detection states of the short detection circuit according to the embodiment. (Part 2) FIG. 5 is an operation diagram illustrating various short detection states of the short detection circuit according to the embodiment. (Part 3) FIG. 6 is a timing chart for explaining power control and short detection determination of the short detection circuit according to the first embodiment. FIG. 7 is a flowchart for explaining power control and short detection determination of the short detection circuit according to the first embodiment. FIG. 8 is a circuit diagram illustrating a configuration example of the short detection circuit according to the second embodiment. FIG. 9 is a circuit diagram showing a configuration example of the short detection circuit according to the third embodiment. FIG. 10 is a circuit diagram illustrating a configuration example of the short detection circuit according to the fourth embodiment. FIG. 11 is a circuit diagram showing a configuration example of the short detection circuit according to the fifth embodiment. (Part 1) FIG. 12 is a circuit diagram showing a configuration example of the short detection circuit according to the fifth embodiment. (Part 2)

(Embodiment 1)
FIG. 1 is a diagram illustrating a hardware configuration example of the electronic apparatus according to the first embodiment. In FIG. 1, a configuration mainly related to short circuit detection is described. When the electronic device 100 is a mobile phone such as a smartphone, a wireless communication unit, a touch panel, and the like are additionally provided.

  The electronic device 100 has an external terminal connector 110 on the outer surface of the housing, and the charging adapter 120 can be inserted into and removed from the external terminal connector 110. Only the power supply related to short circuit detection is illustrated for the external terminal connector 110, and the electronic device 100 may include a signal terminal for data communication with the external device.

  The external terminal connector 110 is, for example, a capless connector (receptacle), and a connector shell 111 as a short detection target is provided on the entire periphery of the opening. The connector shell 111 is connected to the GND of the electronic device 100, for example.

  A terminal board 112 is provided inside the connector shell 111, and a power terminal 113a and a GND terminal 113b are formed on the terminal board 112 in a film shape. The charging adapter 120 is provided with a power supply terminal that is electrically connected to the power supply terminal 113a and a GND terminal that is electrically connected to the GND terminal 113b when being attached to the connector shell 111.

  Inside the electronic device 100, a power supply IC 101 and a charging IC 102 are connected to a power supply terminal 113a of the external terminal connector 110, respectively. The power supply IC 101 operates when supplying power to an external device (such as a USB mouse) connected to the external connector 110 using the electronic device 100 as a power supply source. The charging IC 102 operates when the charging adapter 120 is attached to the external connector 110 and power is supplied from the charging adapter to the electronic device 100.

  The short detection circuit 104 is connected to the connector shell 111 of the external terminal connector 110, and outputs a detection signal corresponding to the following various short states (short mode) generated between the power supply terminal 113 a and the GND terminal 113 b with respect to the connector shell 111. Output to. The short detection circuit 104 operates based on the control of the control unit 105.

[1] Short circuit between the short detection target (connector shell 111) and the power supply terminal 113a to which voltage is applied [2] Short circuit between the short detection target (connector shell 111) and the GND terminal 113b [3] Above [1] Short detection target (connector Resistive short between the shell 111) and the power supply terminal 113a and [2] Resistive short between the short detection target (connector shell 111) and the GND terminal 113b The internal configuration of the short detection circuit 104 (connection configuration of the resistor R, etc.) Will be described later.

  The control unit 105 controls the power feeding IC 101 and the charging IC 102 during power feeding and charging. In addition, the control unit 105 controls power supply to the short detection circuit 104 in order to detect the various short states [1] to [3] in the short detection circuit 104, and the detection output from the short detection circuit 104. Control signal capture. Further, the control unit 105 performs control for notifying (notifying) that the user is in a short state when a short is detected.

  The control unit 105 can be configured using a processor such as a CPU. The control function of the control unit 105 can be realized by the CPU executing a program stored in a memory (not shown), for example, a ROM, and using the RAM as a work area.

  FIG. 2 is a circuit diagram illustrating a configuration example of the short detection circuit according to the first embodiment. The short detection circuit 104 of FIG. 2 includes a plurality of resistors 201, a diode 202, and a FET (Field Effect Transistor) 203 as a short detection element.

  The connector shell 111 that is a short detection target is connected to one end of the connector shell wire 205. The other end of the connector shell wire 205 is connected to the gate of the FET 203 through the middle point O of the voltage dividing circuit of the pair of resistors R1 (201a) and R2 (201a). The resistor R1 (201b) is connected to the power source B.

  The resistor R1 (201a) is connected to the middle point O via a diode D1 (202) made of SBD (Schottky Barrier Diode). One end of the resistor R2 (201c) is connected to the middle point O, and the other end is grounded. D1 (202) has an anode connected to the resistor R1 (201b) and a cathode connected to the middle point O.

  The drain of the FET 203 is connected to the power source A through the resistor R3 (201c) and is input to the control unit (CPU) 105 as the detection signal A through the detection signal line 206. The source of the FET 203 is grounded.

  The power supply B is selectively switched ON / OFF under the control of the control unit (CPU) 105. The power source A is always energized (ON), and the power source B is temporarily energized (ON) controlled for short-circuit detection of [2] “Connector shell and GND short circuit” described above.

  The resistor R3 (201c) and the FET 203 function as the short detection unit 210. The short detection unit 210 includes [1] “connector shell and power terminal short”, [2] “connector shell and GND terminal short”, [3] “resistor short between connector shell and power terminal, And the state of “resistance short between connector shell and GND terminal” is detected.

  The resistor R1 (201a) and the diode D1 (202) function as the GND short detection unit 220. The GND short detection unit 220 operates when the power supply B is turned on, and detects the above-mentioned [2] “Connector shell and GND terminal short circuit”.

  To illustrate the numerical values of the respective parts in FIG. 2, the resistor R1 (201a) is 27 kΩ, the resistor R2 (201b) is 82 kΩ, and the resistor R3 (201c) is 10 kΩ. The FET 203 has a drain-source conduction (ON) when the Vg voltage is 1.2 V or more, and a drain-source conduction (OFF) when the Vg voltage is 0.3 V or less. The control unit (CPU) 105 detects H (High) when the voltage of the detection signal A is 1.2 V or higher, and detects L (Low) when the voltage is 0.6 V or lower.

(Detection operation of various short states)
3 to 5 are operation diagrams for explaining various short detection states of the short detection circuit according to the first embodiment. First, a detection example of the above [1] “connector shell and power supply terminal short-circuited” state will be described with reference to FIG. In the state of FIG. 3 (normal state), the CPU 105 turns on the power source A and operates only the short detection unit 210, and the power source B is turned off and does not operate the GND short detection unit 220 (non-operational state).

  It is assumed that (1) a short circuit occurs between the connector shell 111 and the power supply terminal 113a to which a predetermined voltage (5V) is applied due to, for example, conductive foreign matter N entering the external terminal connector 110. In this case, the connector shell 111 changes from (2) 0V to 5V. As a result, the shell potential of the connector shell wire 205 changes from (3) 0V to 5V.

  Then, the FET 203 changes from OFF to ON, and the voltage of the detection signal line 206 that is the output of the FET 203 changes from (4) 1.8 V to 0 V. Thereby, the input level of the detection signal A to the CPU 105 changes from (5) H → L.

  In the normal state in which only the power supply A is supplied (only the short detection unit 210 is operated), the CPU 105 selects [1] “Short of connector shell and power supply terminal based on (5) H → L change (interrupt) of the detection signal A. ”Is detected.

  Next, a detection example of the above [2] “connector shell and GND short-circuited” state will be described with reference to FIG. After the state where only the power source A is turned on (only the short detection unit 210 is operated) as shown in FIG. 3, the CPU 105 turns on the power source B for a short predetermined period as shown in FIG. That is, in the state of FIG. 4, the CPU 105 turns on the power source A to operate the short detection unit 210 and also turns on the power source B for a predetermined period to operate the GND short detection unit 220.

  Since the GND short detection unit 220 is in operation, the voltage of the connector shell line 205 is lower than the voltage of the power supply B by 1.8 V due to the voltage division by the resistors R1 and R2 and the voltage drop due to the forward voltage of the diode D1. It is about 1.3V.

  In the state of FIG. 4, it is assumed that (1) a short circuit occurs between the connector shell 111 and the GND terminal 113b due to the conductive foreign matter N entering the external terminal connector 110 or the like. In this case, the connector shell 111 changes from (2) about 1.3V to 0V. As a result, the connector shell wire 205 changes from (3) about 1.3V to 0V.

  Then, the FET 203 changes from ON to OFF, and the voltage of the detection signal line 206 that is the output of the FET 203 changes from (4) 0V to 1.8V. As a result, the input level of the detection signal A to the CPU 105 changes from (5) L to H.

  In a state where the power supplies A and B are supplied (both the short detection unit 210 and the GND short detection unit 220 operate), the CPU 105 selects [2] based on the change (interrupt) of (5) L → H of the detection signal A. ] Detects the occurrence of a “connector shell and GND short-circuit” state.

  Next, a detection example of the above-mentioned [3] “Resistive short between connector shell and power supply terminal and resistive short between connector shell and GND terminal” will be described with reference to FIG. 4, after the power supplies A and B are turned on (both the short detection unit 210 and the GND short detection unit 220 operate) as shown in FIG. 4, the CPU 105 has only the power supply A as shown in FIG. 5. Is turned ON to operate only the short detection unit 210. That is, the power supply B is turned off, and the GND short detection unit 220 is brought into a non-operating state.

  In the state shown in FIG. 5, it is assumed that a resistive short circuit occurs between the connector shell 111 and the power supply terminal 113a and the GND terminal 113b due to the conductive foreign matter N entering the external terminal connector 110.

  This resistive short means a state in which a short having the same resistance value ratio as the resistors R1 and R2 of the short detection circuit 104 (GND short detection unit 220) occurs in the external terminal connector 110. That is, when the conductive foreign matter N is an electrolyte solution such as seawater, (1) the connector shell 111 and the power supply terminal 113a are short-circuited with a resistance value r1 (27 kΩ), and (1) the connector shell 111 The GND terminal 113b is short-circuited with a resistance value r2 (82 kΩ). In this resistive short, R1: R2 = r1: r2. In this case, the connector shell 111 changes from (2) 0V to about 3.8V. As a result, the connector shell line 205 changes from (3) 0V to about 3.8V.

  Then, the FET 203 changes from OFF to ON, and the voltage of the detection signal line 206 that is the output of the FET 203 changes from (4) 1.8 V to 0 V. Thereby, the input level of the detection signal A to the CPU 105 changes from (5) H → L.

  In a state where only the power source A is supplied (only the short detection unit 210 is operated), the CPU 105 selects [3] “resistance of the connector shell and the power source terminal based on the change (interrupt) of (5) H → L of the detection signal A. The occurrence of a "short-circuit resistance and a short-circuit resistance between the connector shell and the GND terminal" state is detected.

  Note that (5) H → L changes in the detection signal A are [1] “short circuit between the connector shell and the power supply terminal”, [3] “resistance short circuit between the connector shell and the power supply terminal, and the connector shell and the GND terminal. It occurs in the same manner as “Resistive short of”. Therefore, the CPU 105 changes the detection signal A from (5) H → L when only the power source A is ON (the short detection unit 210 is operated), thereby generating the short circuit [1] or [3]. Is determined. Then, the CPU 105 notifies that the occurrence of [1] “Short-circuit between the connector shell and the power supply terminal” or [3] “Resistive short-circuit between the connector shell and the power-supply terminal and between the connector shell and the GND terminal” occurs. To do.

  FIG. 6 is a timing chart for explaining power control and short detection determination of the short detection circuit according to the first embodiment. As illustrated in FIG. 6, the CPU 105 continuously turns on the power source A and continues the operation of the short detection unit 210 during the operation of the electronic device 100. Then, the CPU 105 turns on the power supply B only for a predetermined period TB (for example, 1 second) within a predetermined period T measured by the timer, and temporarily operates the GND short detection unit 220.

  In the period TA, the CPU 105 turns on only the power supply A and [1] “shorts between the connector shell and the power supply terminal” or [3] “resistive shorts between the connector shell and the power supply terminal, and the resistance between the connector shell and the GND terminal. The occurrence of "Short-circuit short" is detected. Also, during the period TB, the power supplies A and B are turned on to detect the occurrence of [2] “connector shell and GND short-circuit”.

  In the period TA, the CPU 105 determines that no short circuit has occurred if the input detection signal A is H. That is, neither [1] “Short-circuit between connector shell and power supply terminal” nor [3] “Resistive short-circuit between connector shell and power supply terminal and resistive short-circuit between connector shell and GND terminal” occurs. judge.

  In the period TB, the CPU 105 determines that no short circuit has occurred if the input detection signal A is L. That is, it is determined that [2] “Connector shell and GND short-circuit” has not occurred.

  On the other hand, if the input detection signal A is L during the period TA, the CPU 105 determines that a short circuit has occurred. That is, either [1] “Short-circuit between connector shell and power supply terminal” or [3] “Resistive short-circuit between connector shell and power-supply terminal and resistive short-circuit between connector shell and GND terminal” occurs. judge.

  Further, the CPU 105 determines that a short circuit has occurred if the input detection signal A is H in the period TB. That is, it is determined that [2] “Connector shell and GND short-circuit” has occurred.

  FIG. 7 is a flowchart for explaining power control and short detection determination of the short detection circuit according to the first embodiment. The processing content of CPU105 which is a control part is demonstrated. The processing in FIG. 7 is continuously performed at predetermined intervals based on the clock of the CPU 105.

  First, the CPU 105 determines whether to monitor the short states (short mode) [1] and [3] among the various short states [1] to [3] (step S701). For example, if the current timing is the period TA shown in FIG. 6, the CPU 105 monitors the short modes [1] and [3] (step S701: Yes), and proceeds to step S702. On the other hand, if it is the timing of the period TB, the CPU 105 proceeds to step S707.

  In step S702, the CPU 105 starts monitoring the short mode [1] [3], sets the CPU interrupt setting (detection signal A) to the L (Low) level, and turns off the power supply B (the power supply A continues to be ON) ( Step S702). Then, it is determined whether there is a CPU interrupt (detection signal A is detected as L) within the period TA (step S703).

  In step S703, if there is a CPU interrupt (step S703: Yes), the CPU 105 determines that the short circuit [1] or [3] has occurred (step S704). Then, the CPU 105 performs processing for prompting the user to be alerted (step S705), and ends the above processing.

  When a short circuit occurs, for example, the CPU 105 performs control to stop charging and power supply to the electronic device 100, and displays a short circuit notification on the display unit and outputs a sound so that a short state occurs for the user. Alert that you are. A screen display that prompts removal of the charging adapter 120 may be performed. In addition, the notification includes [1] “Connector shell and power supply terminal short circuit” or [3] “Connector shell and power supply terminal resistance short circuit, and connector shell and GND terminal resistive short circuit”. You may include what you are doing.

  On the other hand, if there is no CPU interrupt in step S703 (step S703: No), the CPU 105 determines that there is no short circuit [1] or [3] (step S706), and proceeds to step S707.

  In step S707, the CPU 105 determines whether to start monitoring the short mode [2] (step S707). If the current timing is the period TB shown in FIG. 6, it is determined that the monitoring of the short mode [2] is started (step S707: Yes), and the process proceeds to step S708. On the other hand, if it is not the timing of the period TB (step S707: No), the above process is terminated.

  In step S708, the CPU 105 starts monitoring the short mode [2], sets the CPU interrupt setting (detection signal A) to H (High) level, and turns on the power source B (power source A continues to be on) (step S708). . Then, it is determined whether there is a CPU interrupt (detection of H of the detection signal A) within the period TB (step S709).

  If there is a CPU interrupt in step S709 (step S709: Yes), the CPU 105 determines that the short circuit [2] has occurred (step S710). Then, the CPU 105 performs a process for prompting the user to call attention (step S711), and ends the above process.

  When a short circuit occurs, for example, the CPU 105 performs control to stop charging and power supply to the electronic device 100, and displays a short circuit notification on the display unit and outputs a sound so that a short state occurs for the user. Alert that you are. A screen display that prompts removal of the charging adapter 120 may be performed. This notification may include the occurrence of the state [2] “Connector shell and GND terminal shorted”.

  On the other hand, if there is no CPU interrupt in step S709 (step S709: No), the CPU 105 determines that the short circuit of [2] has not occurred (step S712) and ends the above processing.

  In the first embodiment described above, the potentials between the conductive connector shell such as metal of the connector and the power supply terminal, and between the connector shell and the GND terminal are measured. In order to measure the potential of the connector shell, the short-circuit between the power supply terminal and the connector shell is detected by setting the potential of the connector shell to 0V. Thereafter, the potential of the connector shell is switched to the power supply voltage side to detect a short circuit between the GND terminal and the connector shell. As a result, it is possible to accurately detect a short state between the connector shell, the power supply terminal, and the GND terminal.

  Moreover, corrosion of the metal shell can be prevented by shortening the high potential time at the time of detection under the control of the CPU. For example, even when the electronic device is submerged and all of the connector shell, the power supply terminal, and the GND terminal are in a low impedance state, each short state can be correctly determined.

  Furthermore, when an individual potential change is detected under the control of the CPU, it is possible to prevent the connector from being burned in advance by notifying the user of the electronic device or stopping the power supply. Various short-circuit states can be electrically detected, and when a short-circuit is detected, measures for preventing the current from continuing to flow, such as charging, stopping power feeding, and alerting the user, can be quickly implemented.

  Further, when detecting a short circuit between the connector shell and a power supply terminal to which a voltage is applied, it is not necessary to apply a voltage to the connector shell and it is not necessary to pass a current. In addition, when detecting a short circuit between the connector shell and the GND terminal, it is only necessary to apply a pull-up voltage to the connector shell intermittently for a short period of time at an arbitrary timing for detection, in order to prevent connector corrosion and to detect a short circuit. The current that flows through can be reduced.

  Further, by using an individual semiconductor (FET, diode) for short circuit detection, short circuit detection can be performed at a lower cost.

(Embodiment 2)
FIG. 8 is a circuit diagram illustrating a configuration example of the short detection circuit according to the second embodiment. The same components as those in FIG. 2 are denoted by the same reference numerals. Instead of the FET 203 used in the short detection unit 210 described in the first embodiment, as shown in FIG. 8, one or a plurality of comparators (comparators) may be used. In the configuration in which one comparator is provided, short detection based on one threshold voltage can be performed as in the first embodiment.

  In the configuration example of FIG. 8, the other end of the connector shell wire 205 is connected to comparators (comparators) 803 and 804 to detect short-circuit detection with a plurality of stages of voltages. Then, the midpoint of the resistors R11 (801a) and R12 (801b) that divide the voltage from the power supply C is connected to one input terminal of the comparator 803. Further, the midpoint of the resistors R13 (802a) and R14 (802b) for dividing the voltage from the power source C is connected to one input terminal of the comparator 804. As with the power source A, the power source C is continuously turned on while the electronic device 100 is activated.

  For example, the comparator 803 sets the resistance values of the resistors R11 (801a) and R12 (801b) (and the voltage value of the power supply C) so that V + = 1.0V. Thereby, when V + (1.0V) ≧ V, the output (detection signal A) of the comparator 803 becomes H, and when V + (1.0V) <V, the detection signal A becomes L.

  The comparator 804 sets the resistance values of the resistors R13 (802a) and R14 (802b) (and the voltage value of the power supply C) so that V + = 0.4V. Thereby, when V + (0.4V) ≧ V, the output (detection signal B) of the comparator 804 becomes H, and when V + (0.4V) <V, the detection signal B becomes L.

  As described above, by providing a plurality of comparators, the number of voltage thresholds to be detected can be increased, and short-circuit detection can be performed with multi-stage voltages corresponding to the generated short-circuit state.

  In FIG. 8, the short detection circuit 104 may be additionally provided with a pull-down resistor 811 in the power supply line 810 connected to the power supply terminal 113a of the external terminal connector 110, as indicated by a dotted line. In addition, the resistor 811 can be provided in the same manner for the configuration of the FET of the short detection unit 210 (see FIG. 2). For example, the resistance value of the resistor 811 is 4.5 kΩ. Thus, even when no voltage is applied to the power supply terminal 113a, when the power supply B is turned ON, the operation similar to [2] “Connector shell and GND short-circuit” described above is performed, so that the connection between the connector shell 111 and the power supply terminal 113a. Can be detected.

  According to the second embodiment, the same effect as in the first embodiment can be obtained. Also, by providing a plurality of comparators, various short states can be detected in multiple stages (using the voltage as a threshold). Further, even if no voltage is applied to the power supply terminal, a short circuit between the connector shell and the power supply terminal can be detected.

(Embodiment 3)
FIG. 9 is a circuit diagram showing a configuration example of the short detection circuit according to the third embodiment. Instead of the FET 203 used in the short detection unit 210 described in Embodiment 1, an AD converter (ADC) 901 may be used as shown in FIG. The CPU 105 detects a short state using a predetermined threshold based on the digital output (detection signal A) of the ADC 901. According to the third embodiment, the ADC 901 can use the function of the CPU 105, and the circuit configuration of the short detection circuit 104 can be simplified.

(Embodiment 4)
FIG. 10 is a circuit diagram illustrating a configuration example of the short detection circuit according to the fourth embodiment. The fourth embodiment is a configuration example in which a short circuit is detected corresponding to another charging adapter 120 attached to the external terminal connector 110 of the electronic device 100. As the charging adapter 120, there is one in which a portion on the charging adapter 120 side that contacts the connector shell 111 when connected to the external terminal connector 110 is connected to the GND terminal on the charging adapter 120 inside the charging adapter 120. When such a charging adapter 120 is attached to the external terminal connector 110, the connector shell 111 is connected to the GND terminal 113b via the charging adapter 120.

  In such a charging adapter 120, the short detection circuit 104 detects only the short mode [1] [3]. In this case, the short detection circuit 104 does not need the configuration of the GND short detection unit 220 described above, and can be deleted. According to the fourth embodiment, the charging adapter 120 in which the portion that contacts the connector shell 111 of the charging adapter 120 is connected to the GND terminal on the charging adapter 120 side in the charging adapter 120 is the external terminal connector 110 of the electronic device 100. [1] “Connector shell and power supply terminal short circuit” and [3] “Connector shell and power supply terminal resistance short circuit, and connector shell and GND terminal resistive short circuit” are detected. be able to.

(Embodiment 5)
11 and 12 are circuit diagrams showing configuration examples of the short detection circuit according to the fifth embodiment. In the fifth embodiment, in addition to the configuration of the first embodiment, a function for protecting the short detection circuit 104 when a voltage of a rating (for example, 5 V) or higher is applied to a short detection target is added.

  As shown in FIG. 11, a voltage limiting circuit 1101 is provided between the connector shell 111 and the middle point O on the connector shell line 205. The voltage limiting circuit 1101 includes a resistor R2 (202b), a resistor R4 (1101a), and a switch (SW) 1101b. The resistance value of the resistor R4 (1101a) is, for example, 220 kΩ (when 24V is supported). The switch 1101b is switched to either the A or B position under the control of the CPU 105. When the switch 1101b is switched to the A side, the resistor R4 (1101a) is connected in series on the connector shell line 205. When the switch 1101b is switched to the B side, the resistor R4 (1101a) is removed from the connector shell line 205. Can do.

  Also in the fifth embodiment, as in the first embodiment, the FET 203 characteristics are such that the drain-source is conductive when the Vg voltage is 1.2 V or higher (ON), and the drain-source voltage is 0.3 V or lower. Non-conduction (OFF). The control unit (CPU) 105 detects H (High) when the voltage of the detection signal A is 1.2 V or more, and detects L (Low) when it is 0.6 V or less.

  Then, as shown in FIG. 11, it is assumed that the connector shell 111 and the power supply terminal 113a are short-circuited due to the conductive foreign matter N entering the external terminal connector 110 or the like. For example, assume that a charging adapter 120 with an unspecified power supply voltage (24V) is connected to the external terminal connector 110, and a voltage (for example, 24V) exceeding the rating is applied to the power supply terminal 113a. Thus, a voltage (24 V) exceeding the specified value is applied to the connector shell wire 205.

  Similar to the control of the first embodiment, the CPU 105 controls the power supply B to detect the short state of each short mode [1] [3] or [2]. At this time, the CPU 105 connects the SW 1101b to the B side when the short mode [2] is detected. As a result, when detecting [2] “connector shell and GND short” state, the resistor R4 (1101a) is removed from the connector shell wire 205, and the effect of voltage fluctuation due to the resistor R4 (1101a) is eliminated. it can.

  When detecting the short mode [1] [3], the CPU 105 connects the SW 1101b to the A side. Thus, even when the voltage applied to the connector shell 111 to be detected exceeds the absolute maximum rating of the gate of the FET 203, the voltage is divided by the resistor R4 (1101a) and the resistor R2 (202b) provided on the connector shell wire 205. As a result, application of an excessive voltage to the gate of the FET 203 can be prevented.

  As shown in FIG. 12, the voltage limiting circuit 1101 may be provided with a diode D2 (1202) such as SBD instead of the switch 1101b. The diode D2 (1202) has an anode connected to the middle point O side and a cathode connected to the connector shell 111 side. On the connector shell line 205, the diode D2 (1202) and the resistor R4 (1101a) are connected in parallel.

  In the case of the configuration of FIG. 12, the switch control by the CPU 105 is not necessary. D2 (1202) allows the current of the power supply B to flow to the GND terminal 113b when the connector shell 111 and the GND terminal 113b are short-circuited when the power supply B is ON (ie, when the short mode [2] is detected). , Prevents erroneous detection in the FET 203.

  The fifth embodiment has the same effect as the first embodiment. In addition, the short detection circuit can be protected even when a voltage exceeding the rating is applied to the short detection target.

  According to the embodiment described above, [1] “Short of connector shell and power supply terminal”, [2] “Short of connector shell and GND”, [3] “Resistive short of connector shell and power supply terminal” , And a resistance short circuit between the connector shell and the GND terminal can be detected. And by turning on the power supply B only at the time of detecting the short circuit of [2], the time during which the voltage is applied to the connector shell can be shortened, and corrosion of the connector can be suppressed. By turning on the power supply B only when the short circuit of [2] is detected, the time for the current to flow from the power supply to the GND via the voltage dividing resistor is shortened, the time average current can be reduced, and the current consumption of the electronic device is suppressed. it can.

  Further, by using an FET for short circuit detection, the occurrence of a short circuit can be detected at low cost and with low power consumption with a small current for detection. Furthermore, when various types of short-circuits are detected, charging and power supply can be stopped, and the user can be alerted. As a result, it is possible to take measures to prevent a large current from flowing due to a short circuit between the power supply terminal and the GND terminal via the connector shell, and to improve the safety when a short circuit occurs.

  Note that the control method for short detection described in the present embodiment can be realized by executing a control program prepared in advance on a computer (a processor such as a CPU) such as a target device (electronic device). This control program is recorded on a computer-readable recording medium such as a magnetic disk, an optical disk, or a USB (Universal Serial Bus) flash memory, and is executed by being read from the recording medium by the computer. The control program may be distributed via a network such as the Internet.

  The following additional notes are disclosed with respect to the embodiment described above.

(Supplementary note 1) In a short detection circuit that is provided in an electronic device and detects a short state of an external terminal connector having a conductive connector shell, a power supply terminal, and a GND terminal.
A connector shell wire connected to the connector shell is connected, and a short detection element for detecting a short circuit between the connector shell and the power supply terminal or the GND terminal,
A resistance voltage dividing circuit that changes the potential of the connector shell line based on the control of the presence or absence of power supply of a predetermined voltage, and
The short detection element detects a short circuit between the power supply terminal and the connector shell in a state where the shell potential of the connector shell line is 0V, and the GND terminal in a state where the potential of the connector shell line is a predetermined potential. A short detection circuit for detecting a short between the connector shells.

(Additional remark 2) Furthermore, it has a control part into which the detection signal which the above-mentioned short detection element outputs is inputted,
The controller is
In a state where the supply of power is stopped and the shell potential of the connector shell line is set to 0V, a short circuit between the power supply terminal and the connector shell is detected based on the detection signal, and the power supply is performed. 2. The short detection circuit according to claim 1, wherein control is performed to detect a short circuit between the GND terminal and the connector shell based on the detection signal in a state where the potential of the short circuit is a predetermined potential.

(Supplementary Note 3) When the detection signal is low level in a state where the supply of power is stopped and the shell potential of the connector shell wire is set to 0 V, the control unit short-circuits between the power supply terminal and the connector shell. And when the detection signal is at a high level in a state where the power supply is performed and the potential of the connector shell line is set to a predetermined potential, it is determined that the power supply terminal and the connector shell are short-circuited. The short detection circuit according to appendix 2.

(Additional remark 4) The said short detection element is FET, Short circuit as described in any one of Additional remark 1-3 characterized by the above-mentioned.

(Supplementary note 5) The short detection circuit according to any one of supplementary notes 1 to 3, wherein the short detection element is a comparator.

(Additional remark 6) The said short detection element is ADC, The short detection circuit as described in any one of Additional remark 1-3 characterized by the above-mentioned.

(Supplementary note 7) The short detection circuit according to any one of supplementary notes 1 to 6, wherein a voltage limiting circuit for preventing an overvoltage input is provided in the connector shell line preceding the short detection element.

(Appendix 8) The voltage limiting circuit has a resistor and a switch,
When detecting a short circuit between the power supply terminal and the connector shell, the control unit switches the switch to prevent overvoltage by the resistor, and when detecting a short circuit between the GND terminal and the connector shell. 8. The short detection circuit according to appendix 7, wherein the short circuit is detected without switching through the resistor.

(Supplementary note 9) The short detection circuit according to supplementary note 7, wherein the voltage limiting circuit includes a resistor and a diode connected in parallel on the connector shell line.

(Supplementary Note 10) A short-circuit between the GND terminal and the connector shell in a state where the power supply of the predetermined voltage is supplied for a predetermined period in a short period within a predetermined period, and the potential of the connector shell line is set to a predetermined potential at the time of the supply. 10. The short detection circuit according to any one of appendices 1 to 9, wherein the short detection circuit is detected.

(Additional remark 11) The said control part stops the electric power feeding or charge which is performed via the said external terminal connector at the time of the said short circuit detection, The short detection circuit as described in any one of Additional remark 2-10 characterized by the above-mentioned .

(Supplementary note 12) The short detection circuit according to any one of supplementary notes 2 to 11, wherein the control unit displays on the display unit of the electronic device that a short has been detected when the short is detected.

100 Electronic Device 104 Short Detection Circuit 105 Control Unit (CPU)
DESCRIPTION OF SYMBOLS 110 External terminal connector 111 Connector shell 112 Terminal board 113a Power supply terminal 113b GND terminal 120 Charge adapter 201a-201c Resistance 202 Diode 203 FET
205 connector shell line 206 detection signal line 210 short detection unit 220 GND short detection unit 801a, 801b, 802a, 802b, 811 resistor 803, 804 comparator 810 power supply line 1101 voltage limit circuit 1101a resistor 1101b switch 1202 diode N conductive foreign matter

Claims (11)

In a short detection circuit that is provided in an electronic device and detects a short state of an external terminal connector having a conductive connector shell, a power supply terminal, and a GND terminal,
A connector shell wire connected to the connector shell is connected, and a short detection element for detecting a short circuit between the connector shell and the power supply terminal or the GND terminal,
A resistance voltage dividing circuit that changes the potential of the connector shell line based on the control of the presence or absence of power supply of a predetermined voltage, and
The short detection element detects a short circuit between the power supply terminal and the connector shell in a state where the shell potential of the connector shell line is 0V, and the GND terminal in a state where the potential of the connector shell line is a predetermined potential. A short detection circuit for detecting a short between the connector shells. And a control unit to which a detection signal output by the short detection element is input.
The controller is
In a state where the supply of power is stopped and the shell potential of the connector shell line is set to 0V, a short circuit between the power supply terminal and the connector shell is detected based on the detection signal, and the power supply is performed. 2. The short detection circuit according to claim 1, wherein a short circuit between the GND terminal and the connector shell is detected based on the detection signal in a state where the potential of the short circuit is a predetermined potential.   The control unit determines that the power supply terminal and the connector shell are short-circuited when the detection signal is at a low level in a state where the supply of power is stopped and the shell potential of the connector shell line is set to 0V, 3. The power supply terminal and the connector shell are determined to be short-circuited when the detection signal is at a high level in a state where the power is supplied and the potential of the connector shell line is set to a predetermined potential. The short detection circuit described in 1.   The short detection circuit according to claim 1, wherein the short detection element is an FET.   The short detection circuit according to claim 1, wherein the short detection element is a comparator.   The short detection circuit according to claim 1, wherein the short detection element is an ADC.   The short detection circuit according to claim 1, further comprising a voltage limiting circuit that prevents an overvoltage input in the connector shell line in front of the short detection element. The voltage limiting circuit has a resistor and a switch,
When detecting a short circuit between the power supply terminal and the connector shell, the control unit switches the switch to prevent overvoltage by the resistor, and when detecting a short circuit between the GND terminal and the connector shell. The short detection circuit according to claim 7, wherein the short circuit is detected without switching through the resistor by switching the switch.   8. The short detection circuit according to claim 7, wherein the voltage limiting circuit includes a resistor and a diode connected in parallel on the connector shell line.   Supplying the power of the predetermined voltage for a predetermined period within a short period and detecting a short circuit between the GND terminal and the connector shell in a state where the potential of the connector shell line is set to a predetermined potential during the supply. The short detection circuit according to any one of claims 1 to 9.   11. The short detection circuit according to claim 2, wherein when the short circuit is detected, the control unit stops power feeding or charging performed through the external terminal connector.

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