JP2008026082A - Current sensing circuit, charge control circuit using it, charging circuit, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current sensing circuit which can surely sense a current even when voltage at both ends of a sense resistor changes. <P>SOLUTION: The current sensing circuit 10a senses a current Ichg passing through a predetermined route and outputs a sense voltage Vsense having a voltage value in accordance with the sensed current. The sense resistor Rsense is provided on the route and is provided with a first terminal T1 through which a current flows into and a second terminal T2 through which the current flows out. First and second voltage/current conversion circuits 14, 16 are two voltage/current conversion circuits which generate a current in accordance with the potential difference between the first terminal T1 and the second terminal T2 of the sense resistor Rsense and have different detection ranges. A conversion resistor R13 converts the sum current of output currents I1, I2' of the first and second voltage/current conversion circuits 14, 16 into a voltage and outputs it as a sense voltage Vsense. A comparator 18 switches between the first and second voltage/current conversion circuits 14, 16 in accordance with a voltage Vx2 of the second terminal T2 of the sense resistor Rsense. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a current detection technique.

  Various electronic devices such as recent cellular phones, PDAs (Personal Digital Assistants), and notebook personal computers include a CPU (Central Processing Unit) that performs digital signal processing, a DSP (Digital Signal Processor), a liquid crystal panel, Many other electronic circuits such as analog and digital circuits are installed. In a battery-driven electronic device in which a battery is mounted as a power source, each electronic circuit inside the device operates with a battery voltage from the battery.

  When the battery is a secondary battery such as a lithium ion battery, a charging circuit is built in the electronic device. The charging circuit receives a voltage supplied from an external AC adapter or the like and supplies a charging current to the battery. For example, Patent Documents 1 to 3 disclose related technologies.

Japanese Patent Laid-Open No. 9-219935 JP 2004-138482 A Japanese Patent Laid-Open No. 5-38193

  In such a charging circuit, a charging current flowing from an external power source toward the battery is monitored, and the battery is generally charged so that this current is maintained at a predetermined value. As a method for monitoring the charging current, a current detection circuit is used in which a resistance element for current detection (hereinafter also referred to as a detection resistor) is provided in the charging path, and a voltage drop generated in the detection resistor is monitored.

  The voltage drop generated in the detection resistor becomes a voltage proportional to the charging current, but the voltage appearing at both ends of the detection resistor changes according to the battery voltage to be charged. For example, when the object to be charged is a lithium ion battery, the battery voltage changes in a range of about 0 to 4.5 V, so the voltage at both ends of the detection resistor also changes according to the state of charge of the battery voltage. In order to control the charging current based on the voltage drop generated in the detection resistor, a conversion circuit that temporarily converts this voltage drop to a voltage based on the ground voltage is provided, and the charging current is converted based on the converted voltage. Need to be adjusted. However, since the voltage range that can be converted by this conversion circuit is limited to a certain range, conversion cannot be performed over the entire range of 0 to 4.5 V, and the charging current is detected when the battery voltage falls below a certain level. There was a problem that I could not.

  The present invention has been made in view of such problems, and a comprehensive object thereof is to provide a current detection circuit capable of reliably detecting a current even when the voltage across the detection resistor changes.

  According to an aspect of the present invention, there is provided a current detection circuit that detects a current flowing through a predetermined path and outputs a detection voltage having a voltage value corresponding to the detected current. The current detection circuit is provided on a path, and includes a detection resistor having a first terminal through which current flows in and a second terminal through which current flows out, and a current corresponding to a potential difference between the first terminal and the second terminal of the detection resistor. Two voltage-current conversion circuits to be generated, which convert the total current of the output currents of the first and second voltage-current conversion circuits having different detection ranges and the first and second current-voltage conversion circuits into a voltage and detect it A conversion resistor that outputs the voltage; and a selector circuit that switches between the first and second voltage-current conversion circuits according to the voltage of one of the first and second terminals of the detection resistor.

In this specification, “member A and member B are connected” means that member A and member B are physically directly connected, or member A and member B are in an electrically connected state. It includes the case where it is indirectly connected through another member that does not affect.
According to this aspect, since an appropriate voltage-current conversion circuit can be selected according to the voltage appearing at any terminal of the detection resistor, current detection can be performed in a wide voltage range.

  The first voltage-current converter circuit has a first resistor having one end connected to the first terminal of the detection resistor, a PNP bipolar transistor having an emitter connected to the other end of the first resistor, and a non-inverting input terminal detecting A first operational amplifier connected to the second terminal of the resistor, an inverting input terminal connected to the emitter of the PNP bipolar transistor, and an output terminal connected to the base of the PNP bipolar transistor. The second voltage-current converter circuit has a second resistor having one end connected to the second terminal of the detection resistor, an NPN bipolar transistor having an emitter connected to the other end of the second resistor, and a non-inverting input terminal detecting And a second operational amplifier connected to the first terminal of the resistor, having an inverting input terminal connected to the emitter of the NPN bipolar transistor, and having an output terminal connected to the base of the NPN bipolar transistor. The first and second voltage / current converter circuits may output currents flowing through the PNP bipolar transistor and the NPN bipolar transistor, respectively.

  The selector circuit includes a comparator that compares a predetermined voltage of either the first or second terminal with a predetermined threshold voltage, and makes the first and second operational amplifiers complementary according to an output signal of the comparator. May be turned on or off.

  The second voltage-current conversion circuit may further include a third operational amplifier having an output terminal and an inverting input terminal connected to one end of the second resistor, and a non-inverting input terminal connected to the second terminal of the detection resistor.

  According to another aspect of the present invention, a charge control circuit is provided. This charging control circuit is a charging control circuit that adjusts a charging current flowing from a power source to a battery to be charged, and includes a detection resistor provided on a charging path from the power source to the battery. And a charging current adjusting circuit that adjusts the charging current so that the voltage value of the detection voltage output from the current detecting circuit matches a predetermined reference voltage. The selector circuit of the current detection circuit switches between the first and second voltage-current conversion circuits based on the voltage appearing at the second terminal connected to the battery.

  According to yet another aspect of the invention, a charging circuit is provided. This charging circuit is a charging circuit that charges a battery based on a power supply voltage from a power source. The charging transistor provided on the path from the power source to the battery, and the on state of the charging transistor are adjusted to And a charge control circuit for adjusting a charging current to be supplied.

  Yet another embodiment of the present invention is an electronic device. This electronic device includes a battery, the above-described charging circuit that charges the battery based on a power supply voltage from the power supply, and a load circuit that is driven by the battery.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  According to the current detection circuit of the present invention, it is possible to reliably detect a current in a wide voltage range.

  Hereinafter, a charge control circuit according to an embodiment of the present invention will be described with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. Further, in the following description, reference numerals attached to voltage signals, current signals, resistors, capacitors, and the like are used to represent the respective voltage values, current values, resistance values, and capacitance values as necessary.

  FIG. 1 is a circuit diagram illustrating a configuration of an entire electronic apparatus 1000 including a charging circuit 200 according to an embodiment. The electronic device 1000 is a battery-driven information terminal device such as a mobile phone terminal, PDA, or notebook PC. The electronic device 1000 includes a charging circuit 200 and a battery 220. In addition to these, the electronic apparatus 1000 includes a power supply circuit (not shown), a DSP, a liquid crystal panel, and other analog and digital.

  The battery 220 is a secondary battery such as a lithium ion or NiCd (nickel cadmium) battery, and the battery voltage Vbat is supplied to other circuit blocks of the electronic device 1000.

  The external power source 210 is connected to the electronic device 1000 and is an AC adapter that converts commercial AC voltage into DC voltage, a DC / DC converter that steps down the voltage of a vehicle battery, and the like, and is connected to the electronic device 1000. The external power supply 210 supplies a DC power supply voltage Vdc to the charging circuit 200.

  Charging circuit 200 charges battery 220 based on power supply voltage Vdc from external power supply 210. The charging circuit 200 includes a charging transistor Tr1, a charging control circuit 100, and other circuit elements.

  The charging transistor Tr1 is provided on a charging path from the external power supply 210 to the battery 220. In the present embodiment, a path reaching the battery 220 via the charging transistor Tr1, a current input terminal 106 of the charging control circuit 100, a detection resistor Rsense described later, and the battery terminal 108 is a charging path. The charging transistor Tr1 is a PNP-type bipolar transistor, and an emitter is connected to the external power source 210. A resistor R1 is connected between the emitter and base of the charging transistor Tr1. In addition, a charging control transistor Tr2 is connected between the base of the charging transistor Tr1 and a ground terminal which is a fixed voltage terminal. The charge control transistor Tr2 is an NPN bipolar transistor, and has a collector connected to the base of the charge transistor Tr1 and an emitter connected to the ground terminal. The collector of the charging transistor Tr1 is connected to the charging control circuit 100.

  The charge control circuit 100 is integrated as a functional IC on the semiconductor substrate, and adjusts the ON state of the charge transistor Tr1 to adjust the charge current Ichg supplied to the battery 220. The charge control circuit 100 includes a power supply terminal 102, a charge control terminal 104, a current input terminal 106, and a battery terminal 108 as input / output terminals. Further, the current input terminal 106 and the battery terminal 108 function as terminals for measuring the resistance value of the detection resistor Rsense in the inspection process of the charge control circuit 100.

  A battery 220 is connected to the battery terminal 108, and a collector of the charging transistor Tr1 is connected to the current input terminal 106. From the charging control terminal 104, a control voltage Vcnt for controlling the degree of turning on of the charging transistor Tr1 is output. This control voltage Vcnt is input to the base of the charge control transistor Tr2. The power supply terminal 102 is a power supply terminal of the charging control circuit 100 itself, and is supplied with the power supply voltage Vdd from the external power supply 210. Circuit elements inside the charge control circuit 100 operate based on the power supply voltage Vdd.

  Hereinafter, the internal configuration of the charging control circuit 100 will be described. The charging control circuit 100 includes a detection resistor Rsense, a current detection circuit 10, an error voltage generation unit 20, and a current adjustment unit 30. The detection resistor Rsense is provided to monitor the charging current Ichg to the battery 220, and is provided between the current input terminal 106 and the battery terminal 108, that is, on the charging path from the external power supply 210 to the battery 220. . A voltage drop ΔV proportional to the resistance value Rsense and the charging current Ichg is generated at both ends of the detection resistor Rsense.

  The charging current adjustment circuit 40 including the current detection circuit 10, the error voltage generation unit 20, and the current adjustment unit 30 is based on the error voltage Verr between the voltage drop ΔV generated in the detection resistor Rsense and a predetermined reference voltage Vref. Adjust. That is, the charging current adjustment circuit 40 considers the voltage drop ΔV generated in the detection resistor Rsense as the charging current Ichg, and adjusts the degree of ON of the charging transistor Tr1. Specifically, the charging control circuit 100 adjusts the turn-on degree of the charging transistor Tr1 by feedback so that the voltage drop of the detection resistor Rsense approaches a predetermined voltage value.

  The current detection circuit 10 converts the voltage drop ΔV generated in the detection resistor Rsense into a detection voltage Vsense based on the ground voltage. The current detection circuit 10 includes a resistor R2, a resistor R3, a first bipolar transistor Q1, and an operational amplifier 12.

  The low voltage side terminal of the detection resistor Rsense is connected to the non-inverting input terminal of the operational amplifier 12. The resistor R2 is provided between the high voltage side terminal of the detection resistor Rsense and the non-inverting input terminal of the operational amplifier 12. The first bipolar transistor Q1 is a PNP bipolar transistor, and has an emitter connected to the resistor R2 and the inverting input terminal of the operational amplifier 12, and a base connected to the output terminal of the operational amplifier 12. The resistor R3 is provided between the ground terminal and the collector of the first bipolar transistor Q1.

  In the current detection circuit 10, assuming that an imaginary short circuit is established in the operational amplifier 12, it can be considered that the voltages at the non-inverting input terminal and the inverting input terminal of the operational amplifier 12 are equal. At this time, the voltage drop ΔV generated in the detection resistor Rsense is applied to the resistor R2, and the first current I1 = ΔV / R2 is generated. The first current I1 flows through the first bipolar transistor Q1 and the resistor R3, and the detection voltage Vsense given by I1 × R3 is generated in the resistor R3 with reference to the ground voltage. Here, Vsense = ΔV × R3 / R2 is established, and the detection voltage Vsense is a voltage proportional to the voltage drop ΔV generated in the detection resistor Rsense. The resistors R2 and R3 are preferably formed by pairing.

  The error voltage generator 20 receives the detection voltage Vsense generated by the current detection circuit 10, compares it with a predetermined reference voltage Vref, and generates an error voltage Verr obtained by amplifying the error between the two voltages. The error voltage generator 20 includes a variable voltage source 22, an operational amplifier 24, a first MOS transistor M1, and a resistor R4.

  The variable voltage source 22 generates a predetermined reference voltage Vref. The variable voltage source 22 is configured such that the value of the reference voltage Vref can be adjusted by trimming. The reference voltage Vref generated by the variable voltage source 22 is input to the inverting input terminal of the operational amplifier 24. In the present embodiment, the reference voltage Vref that is the output of the variable voltage source 22 is configured to be monitored from the outside at least in the inspection process of the charge control circuit 100. In the charge control circuit 100 of FIG. 1, a voltage monitor terminal 110 is provided at the output of the variable voltage source 22. The voltage monitor terminal 110 only needs to be able to measure voltage from the outside by some method, and does not need to be formed as an electrode pad.

  The detection voltage Vsense output from the current detection circuit 10 is input to the non-inverting input terminal of the operational amplifier 24. The operational amplifier 24 amplifies an error between the detection voltage Vsense and the reference voltage Vref, and outputs an error voltage Verr '. The first MOS transistor M1 is an N-channel MOSFET, the source is grounded, and the output terminal of the operational amplifier 24 is connected to the gate. The resistor R4 has one end connected to the drain of the first MOS transistor M1, and outputs a voltage appearing at the other end as an error voltage Verr.

  The current adjustment unit 30 receives the error voltage Verr output from the error voltage generation unit 20, generates a control voltage Vcnt corresponding to the error voltage Verr, and supplies the base voltage of the charge control transistor Tr2 via the charge control terminal 104. Adjust. When the turn-on degree of the charge control transistor Tr2 is controlled by the control voltage Vcnt, the collector current of the charge control transistor Tr2 changes, and the voltage drop generated in the resistor R2 changes. As a result, the base-emitter voltage of the charging transistor Tr1 changes, and the degree of ON of the charging transistor Tr1 is adjusted.

  The current adjustment unit 30 includes a second MOS transistor M2, a resistor R5, a resistor R6, a resistor R7, and a first capacitor C1. The second MOS transistor M2 is an N-channel MOSFET, and the error voltage Verr from the error voltage generator 20 is input to its gate. A first capacitor C1 and a resistor R6 are provided in series between the gate and drain of the second MOS transistor M2 in order to stabilize the circuit. A resistor R6 is provided between the source of the second MOS transistor M2 and the ground terminal. The seventh resistor R 7 has one end connected to the source of the second MOS transistor M 2 and the other end connected to the charge control terminal 104.

  In the charging control circuit 100, a circuit element (not shown) such as a switch for cutting off the charging voltage may be provided on the charging path from the current input terminal 106 to the battery terminal 108.

  Next, a preferred configuration example of a current detection circuit that detects a charging current and outputs a detection voltage Vsense having a voltage value corresponding to the detected current will be described. In the circuit of FIG. 1, the voltage at the battery terminal 108 changes according to the state of charge of the battery 220. The current detection circuit 10 of FIG. 1 can convert the voltage drop ΔV into a detection voltage Vsense with respect to the ground voltage when the battery voltage Vbat is high to some extent. However, if the battery voltage Vbat becomes low to some extent, for example, 2V If the voltage drops below, the detection voltage Vsense may not be generated. That is, in the current detection circuit 10 of FIG. 1, when the battery voltage Vbat is low, the charging current Ichg may not be accurately adjusted.

FIG. 2 is a circuit diagram illustrating a configuration of the current detection circuit according to the embodiment. The current detection circuit 10a of FIG. 2 is a circuit that can generate the detection voltage Vsense in a wider voltage range than the current detection circuit 10 of FIG. Hereinafter, the current detection circuit 10a will be described.
The current detection circuit 10a includes a detection resistor Rsense, a first voltage / current conversion circuit 14, a second voltage / current conversion circuit 16, a comparator 18, and a conversion resistor R13.

  The detection resistor Rsense is provided on the charging path, and includes a first terminal T1 through which current flows and a second terminal T2 through which current flows out. The first voltage-current conversion circuit 14 and the second voltage-current conversion circuit 16 are voltage-current conversion circuits that generate currents according to the potential difference ΔV between the first terminal T1 and the second terminal T2 of the detection resistor Rsense, and have different detections. Has a range. “Detection range” refers to a range of input voltage levels in which voltage-current conversion can be accurately performed. When one of the first voltage current conversion circuit 14 and the second voltage current conversion circuit 16 is active, the other is inactive.

  The first voltage-current conversion circuit 14 includes a first resistor R11, a first transistor Q11, and a first operational amplifier AMP1. One end of the first resistor R11 is connected to the first terminal T1 of the detection resistor Rsense. The first transistor Q11 is a PNP-type bipolar transistor, and the emitter is connected to the other end of the first resistor R11. The non-inverting input terminal of the first operational amplifier AMP1 is connected to the second terminal T2 of the detection resistor Rsense, the inverting input terminal is connected to the emitter of the first transistor Q11, and the output terminal is connected to the base of the first transistor Q11. Is done. The first voltage-current conversion circuit 14 and the conversion resistor R13 in FIG. 2 correspond to the current detection circuit 10 in FIG. The first voltage-current conversion circuit 14 outputs a current I1 that flows through the first transistor Q11. The current I1 output from the first voltage-current conversion circuit 14 is given by I1 = Ichg × Rsense / R11.

  The second voltage-current conversion circuit 16 includes a second resistor R12, a second operational amplifier AMP2, a third operational amplifier AMP3, a second transistor Q12, a third transistor Q13, and a fourth transistor Q14. One end of the second resistor R12 is connected to the second terminal T2 of the detection resistor Rsense via the third operational amplifier AMP3. The second transistor Q12 is an NPN-type bipolar transistor, and the emitter is connected to the other end of the second resistor R12. The second operational amplifier AMP2 has a non-inverting input terminal connected to the first terminal T1 of the detection resistor Rsense, an inverting input terminal connected to the emitter of the second transistor Q12, and an output terminal connected to the base of the second transistor Q12. The The third transistor Q13 and the fourth transistor Q14 constitute a current mirror circuit (mirror ratio 1: 1), and outputs a current I2 'corresponding to the second current I2 flowing through the second transistor Q12. The current I2 'output from the second voltage-current conversion circuit 16 is given by I2 = Ichg × Rsense / R12.

  The third operational amplifier AMP3 has an output terminal and an inverting input terminal connected to one end of the second resistor R12, and a non-inverting input terminal connected to the second terminal T2 of the detection resistor Rsense. The third operational amplifier AMP3 is a voltage follower, and sets the voltage at one end of the second resistor R12 equal to the voltage Vx2 at the second terminal T2 of the detection resistor Rsense. A current I2 flowing through the second transistor Q12 and the second resistor R12 flows as a sink current of the third operational amplifier AMP3. By providing the third operational amplifier AMP3, it is possible to prevent the current I2 from flowing out of the current detection circuit 10a from the battery terminal 108.

  The conversion resistor R13 converts the total current of the output currents I1 and I2 'of the first voltage-current conversion circuit 14 and the second voltage-current conversion circuit 16 into a voltage and outputs it as a detection voltage Vsense.

  The comparator 18 functions as a selector circuit that switches between the first voltage-current conversion circuit 14 and the second voltage-current conversion circuit 16 in accordance with the second terminal T2 of the detection resistor Rsense, that is, the voltage Vx2 of the battery terminal 108. The comparator 18 compares the voltage Vx2 (= Vbat) of the second terminal T2 with a predetermined threshold voltage Vth, and complements the first operational amplifier AMP1 and the second operational amplifier AMP2 according to the output signal. Turn on and off. Specifically, when Vx2> Vth, the first operational amplifier AMP1 is turned on and the second operational amplifier AMP2 is turned off. When Vx2 <Vth, the second operational amplifier AMP2 is turned on and the first operational amplifier AMP1 is turned off. Become. The threshold voltage Vth is preferably set near the boundary of the detection range of the first voltage-current conversion circuit 14 and the second voltage-current conversion circuit 16, and is set to about 2 V, for example.

  The operation of the current detection circuit 10a of FIG. 2 configured as described above will be described. When the voltage at the second terminal T2 of the detection resistor Rsense, that is, the battery voltage Vbat is higher than the threshold voltage Vth, the comparator 18 activates the first voltage-current conversion circuit 14. At this time, the current I1 flows through the conversion resistor R13, and the current detection circuit 10a in FIG. 2 is equivalent to the circuit in FIG. When the battery voltage Vbat falls below the threshold voltage Vth, the first voltage-current conversion circuit 14 cannot perform current conversion. At this time, the comparator 18 deactivates the first voltage-current conversion circuit 14 and activates the second voltage-current conversion circuit 16. At this time, the conversion resistor R13 generates the detection voltage Vsense by converting the current I2 'into a voltage.

  As described above, according to the current detection circuit 10a of FIG. 2, it is possible to detect current in a voltage range that cannot be detected by the current detection circuit 10 of FIG.

  Those skilled in the art will understand that the above-described embodiment is an exemplification, and that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the embodiment, the case where the charging transistor Tr1, the charging control transistor Tr2, the resistor R1, and the like are provided outside the charging control circuit 100 has been described. However, the present invention is not limited to this, and these elements are A part or all of them may be integrated in the charging control circuit 100.

  In the current detection circuit 10a of FIG. 2, the first voltage-current conversion circuit 14 and the second voltage-current conversion circuit 16 are configured using bipolar transistors, but may be configured using MOSFETs. Moreover, although the current detection circuit 10a of FIG. 2 can be used suitably for the charge control circuit 100, the application is not limited thereto. The current detection circuit 10a of FIG. 2 can be widely used for applications in which the voltage across the detection resistor Rsense shifts depending on the state of the circuit.

It is a circuit diagram which shows the structure of the whole electronic device provided with the charging circuit which concerns on embodiment. It is a circuit diagram which shows the structure of the current detection circuit which concerns on embodiment.

Explanation of symbols

  Rsense detection resistor, R11 first resistor, R12 second resistor, R13 conversion resistor, 10 current detection circuit, 14 first voltage current conversion circuit, 16 second voltage current conversion circuit, 18 comparator, AMP1 first operational amplifier, AMP2 first 2 operational amplifier, AMP3 3rd operational amplifier, Q11 1st transistor, Q12 2nd transistor, Q13 3rd transistor, Q14 4th transistor.

Claims (7)

A current detection circuit that detects a current flowing through a predetermined path and outputs a detection voltage having a voltage value corresponding to the detected current;
A detection resistor provided on the path, comprising a first terminal through which the current flows and a second terminal through which the current flows;
Two voltage-current converters that generate currents according to a potential difference between the first terminal and the second terminal of the detection resistor, the first and second voltage-current converters having different detection ranges;
A conversion resistor for converting a total current of output currents of the first and second current-voltage conversion circuits into a voltage and outputting the voltage as the detection voltage;
A selector circuit that switches between the first and second voltage-current conversion circuits according to the voltage of one of the first and second terminals of the detection resistor;
A current detection circuit comprising: The first voltage-current conversion circuit includes:
A first resistor having one end connected to the first terminal of the detection resistor;
A PNP-type bipolar transistor having an emitter connected to the other end of the first resistor;
A first operational amplifier having a non-inverting input terminal connected to the second terminal of the detection resistor, an inverting input terminal connected to the emitter of the PNP bipolar transistor, and an output terminal connected to the base of the PNP bipolar transistor When,
Including
The second voltage-current conversion circuit includes:
A second resistor having one end connected to the second terminal of the detection resistor;
An NPN bipolar transistor having an emitter connected to the other end of the second resistor;
A second operational amplifier having a non-inverting input terminal connected to the first terminal of the detection resistor, an inverting input terminal connected to the emitter of the NPN bipolar transistor, and an output terminal connected to the base of the NPN bipolar transistor When,
Including
2. The current detection circuit according to claim 1, wherein the first and second voltage-current conversion circuits output currents flowing through the PNP bipolar transistor and the NPN bipolar transistor, respectively. The selector circuit is
It includes a comparator that compares a predetermined voltage at either the first or second terminal with a predetermined threshold voltage, and the first and second operational amplifiers are complementarily turned on according to the output signal of the comparator. The current detection circuit according to claim 2, wherein the current detection circuit is turned off. The second voltage-current conversion circuit includes:
The output terminal and the inverting input terminal are further connected to one end of the second resistor, and further include a third operational amplifier having a non-inverting input terminal connected to the second terminal of the detection resistor. The current detection circuit described. A charge control circuit for adjusting a charging current flowing from a power source to a battery to be charged,
A current detection circuit according to any one of claims 1 to 4, including a detection resistor provided on a charging path from the power source to the battery;
A charging current adjustment circuit that adjusts the charging current so that a voltage value of the detection voltage output from the current detection circuit matches a predetermined reference voltage;
With
The charge control circuit, wherein the selector circuit of the current detection circuit switches between the first and second voltage-current conversion circuits based on a voltage appearing at the second terminal connected to the battery. A charging circuit for charging a battery based on a power supply voltage from a power supply,
A charging transistor provided on a path from the power source to the battery;
The charge control circuit according to claim 5, wherein an on state of the charging transistor is adjusted to adjust a charging current supplied to the battery.
A charging circuit comprising: Battery,
The charging circuit according to claim 6, wherein the battery is charged based on a power supply voltage from a power supply;
A load circuit driven by the battery;
An electronic device comprising:

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