JP2017041842A - Current detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detection circuit capable of detecting the current flowing in the load of the BTL amplifier with a simple and general-purpose configuration.SOLUTION: The current detection circuit comprises a first amplifier 121 for outputting a predetermined signal, a second amplifier 122 for outputting a signal having an opposite phase to the output signal of the first amplifier, voltage dividing resistors 13 and 14 for dividing a potential difference between both ends of a load connecting the output terminal of the first amplifier and the output terminal of the second amplifier, the voltage dividing resistors 13 and 14, at the connection point of the voltage dividing resistors, having resistance values determined so that the amplitude of the output signal of the first amplifier and the amplitude of the output signal of the second amplifier cancel each other, a load current detection resistor 16 connected in series with the load 15, and a difference detection unit 17 for detecting the current flowing in the load on the basis of a potential difference between a potential at a connection point of the first and second voltage dividing resistors, a reference potential which is a predetermined potential, the ratio of the resistance values of the first and second voltage dividing resistors, and a resistance value of the load current detecting resistor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current detection circuit that detects a current flowing through a load.

  Patent Document 1 discloses a BTL amplifier that can secure an output dynamic range even when a reference voltage that determines an operating point of an operational amplifier is shifted from ½ of a power supply voltage due to a sudden change in power supply voltage. ing. BTL is an abbreviation for Balanced Tied Load, Bridged Transformer Less, Balanced Transformer Less, and the like.

  Further, in Patent Document 2, the current is supplied to the load by driving the load BTL with the master amplifier and the slave amplifier and feeding back the generated voltage of the current detection resistor interposed in series with the load to the inverting input side of the master amplifier. Is disclosed as a constant current drive circuit that can be controlled in accordance with an input signal. According to the constant current drive circuit of Patent Document 2, the inverting input of the master amplifier to which the voltage generated by the current detection resistor is fed back is virtually short-circuited to the reference potential by the negative feedback operation of the master amplifier. Therefore, the common mode input voltage range of the amplifier is not limited.

JP 2013-038538 A JP-A-7-38351

  Patent Document 1 does not focus on executing various controls according to the current flowing through the load. On the other hand, Patent Document 2 focuses on keeping the inverting input of the master amplifier at a constant potential by feeding back the voltage generated in the current detection resistor to the inverting input side of the master amplifier. However, the constant current drive circuit disclosed in this document cannot be said to be a general-purpose configuration for performing various controls according to the current flowing through the load. Therefore, an object of the present invention is to provide a current detection circuit that can detect a current flowing through a load with a simple and general-purpose configuration using a BTL amplifier.

  The current detection circuit of the present invention includes a first amplifier, a second amplifier, first and second voltage dividing resistors, a load current detection resistor, and a difference detection unit.

  The first amplifier outputs a predetermined signal. The second amplifier outputs a signal having a phase opposite to that of the output signal of the first amplifier. The first and second voltage dividing resistors are voltage dividing resistors for dividing a potential difference between both ends of a load connecting the output terminal of the first amplifier and the output terminal of the second amplifier. Each resistance value is determined so that the amplitude of the output signal of the first amplifier and the amplitude of the output signal of the second amplifier cancel each other at the connection point of the two voltage dividing resistors. The load current detection resistor is connected in series with the load. The difference detection unit includes a potential difference between a potential at a connection point of the first and second voltage dividing resistors and a reference potential which is a predetermined potential, a ratio of resistance values of the first and second voltage dividing resistors, and a load. Based on the resistance value of the current detection resistor, the current flowing through the load is detected.

  According to the current detection circuit of the present invention, the current flowing through the load can be detected with a simple and general-purpose configuration using a BTL amplifier.

FIG. 3 is a circuit diagram illustrating a configuration of a current detection circuit according to the first embodiment. FIG. 6 is a circuit diagram illustrating a configuration of a current detection circuit according to a second embodiment. FIG. 6 is a circuit diagram illustrating a configuration of a current detection circuit according to a third embodiment. FIG. 6 is a circuit diagram illustrating a configuration of a current detection circuit according to a fourth embodiment. FIG. 10 is a circuit diagram illustrating a configuration of a current detection circuit according to a fifth embodiment. FIG. 10 is a circuit diagram illustrating a configuration of a current detection circuit according to a sixth embodiment. FIG. 3 is a circuit diagram for comparison of operation between a conventional example and Example 1. FIG. 4 is a waveform diagram for comparison of operation between a conventional example and Example 1.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted.

The configuration and operation of the current detection circuit according to the first embodiment will be described below with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a current detection circuit 1 of the present embodiment. As shown in the figure, the current detection circuit 1 of this embodiment includes a signal input unit 10, a feedback control unit 11, a BTL amplifier 12, a first voltage dividing resistor 13, and a second voltage dividing resistor 14. And a load 15, a load current detection resistor 16, and a difference detection unit 17. The BTL amplifier 12 includes a first amplifier 121 and a second amplifier 122. Note BTL amplifier 12 in the present embodiment, the positive supply voltage _{+ V cc,} a dual-supply amplifiers _ee negative supply voltage _-V.

The first amplifier 121 outputs a predetermined signal. Here, V (t) is a function representing the voltage of the amplifier output signal with time t as a variable, and the DC component (hereinafter also referred to as reference potential V _B ) of the signal output from the first amplifier 121 is zero. Assume that the output signal of the first amplifier 121 is represented as nV (t) +0. Here, n is an arbitrary positive number.

The second amplifier 122 outputs −V (t) +0, which is a signal having a phase opposite to that of the output signal of the first amplifier 121. The load 15 connects the output terminal of the first amplifier 121 and the output terminal of the second amplifier 122. The load current detection resistor 16 is connected to the load 15 in series. The resistance value of the first, and second voltage dividing resistors 13 and 14 will be described later is sufficiently large, the current I _L flowing through the load 15 and the load current detecting resistor 16 as causes deemed equal to approximately To do.

  The first and second voltage dividing resistors 13 and 14 are voltage dividing resistors that divide the potential difference between both ends of the load 15. Each resistance value is set so that the amplitude of the output signal of the first amplifier 121 and the amplitude of the output signal of the second amplifier 122 cancel each other at the connection point of the first and second voltage dividing resistors 13 and 14. Is stipulated. If the resistance value is defined using the value n in the example of the figure, when the resistance value of the first voltage dividing resistor 13 is nR, the resistance value of the second voltage dividing resistor 14 is R.

As shown in the figure, the potential at the connection point of the load current detection resistor 16 and the second voltage dividing resistor 14 is expressed as −V (t) + 0 + I _L R _S. However, R _S indicates the resistance value of the load current detection resistor 16 and is known. Further, as described above, the potential of the output terminal of the first amplifier is expressed as nV (t) +0. The potential V _{C at} the connection point of the first and second voltage dividing resistors 13 and 14 is:

It becomes. As shown in the above calculation formula, the amplitude ratio of the voltages of the output signals of the first and second amplifiers 121 and 122 is n: 1, and the resistance values of the first and second voltage dividing resistors 13 and 14 are as follows. Similarly, when the ratio of n is n: 1, the AC components of the output signals of the first and second amplifiers 121 and 122 cancel each other, and the term V (t) is cancelled. If n = 1, the amplitude ratio of the voltages of the output signals of the first and second amplifiers 121 and 122 is 1: 1, and the ratio of the resistance values of the first and second voltage dividing resistors 13 and 14 is 1: 1. Is 1: 1, that is, the resistance values of the two voltage dividing resistors are equal.

  As shown in the figure, the difference detector 17 is connected to the connection point of the first and second voltage dividing resistors 13 and 14 and the ground, and has a function of detecting a potential difference between the two points. The difference detection unit 17 is a potential at a connection point of the first and second voltage dividing resistors 13 and 14.

And the reference potential V _B (in this embodiment, V _B = 0, that is, the ground potential).

The basis, and the value n, based on the resistance value R _S of the load current detecting resistor to detect the current I _L flowing through the load. The difference detection unit 17 feeds back the detected current _IL to the feedback control unit 11. In the present embodiment, the difference detection unit 17 is represented as an independent component, but the difference detection unit 17 may be omitted depending on circumstances. For example, when using a current detection circuit 1 of this embodiment only as a voltage-current conversion circuit is omitted difference detection unit 17, just sufficient simply added to the input signal as the feedback voltage V _C of the above.

Feedback control unit 11 executes a predetermined control corresponding to the current I _L. Specifically, the feedback control unit 11 generates an original signal for driving a load (apparatus) according to the signal from the signal input unit 10 and the signal from the difference detection unit 17. The generated signal is converted into a normal phase signal and a reverse phase signal via a complementary signal output circuit, and drives a load (device).

  In the simplest configuration, the feedback control unit 11 can be configured with only an adder circuit. If feedback is applied by adding the output of the difference detection unit 17 to the input signal, it operates as a voltage-current conversion circuit that allows current to flow through the load circuit in accordance with the input signal. As described above, when the BTL amplifier is a dual power supply, the reference potential is GND (ground), so the difference detection unit 17 does not have to be prepared as an independent circuit. When it is necessary to set the upper limit of the power applied to the load, the upper limit of the detected current value may be set and the waveform of the complementary signal may be controlled so that the difference from the upper limit value gradually approaches zero.

  According to the current detection circuit 1 of the present embodiment, since the AC component of the output signals of the two amplifiers of the BTL amplifier 12 is canceled at the connection point of the voltage dividing resistor, the difference detecting unit 17 has the voltage dividing resistor. The current flowing through the load can be detected by referring to the potential at the connection point. Since the above configuration is simple and versatile, it can be used for any product that requires detection of the current flowing through the load.

  Also, when driving the load with a signal having a pulse waveform, the conventional circuit configuration (configuration for measuring the potential difference between both ends of the load current detection resistor) handles a high-speed large-amplitude waveform, thus ensuring stable operation. It was difficult.

  FIG. 7 shows a potential difference detection circuit for comparing the conventional example and the present embodiment with voltage waveforms, and FIG. 8 shows voltage waveforms at each measurement point shown in FIG. The potential difference detection circuit 70 shown in FIG. 7 is a circuit example configured by using a first resistor 701, a second resistor 702, a third resistor 703, a fourth resistor 704, and an operational amplifier 705. Conventionally, a potential difference is measured. This is a commonly used circuit. The inverting input terminal and the non-inverting input terminal of the operational amplifier 705 are connected to both ends of the load current detection resistor 16 via the first resistor 701 and the second resistor 702. The inverting input terminal of the operational amplifier 705 is connected to the output terminal of the operational amplifier 705 via the third resistor 703. The non-inverting input terminal of the operational amplifier 705 is connected to the ground via the fourth resistor 704.

  The voltage dividing resistors 13 and 14 are provided in order to compare the effect of the method of this embodiment and the conventional method of measuring the potential difference between both ends of the load current detection resistor 16 in the same circuit. It is assumed that n = 1 and the resistance values of the voltage dividing resistors 13 and 14 are both R.

  E0 is a voltage at the connection point of the voltage dividing resistors 13 and 14, E1 is a voltage at the inverting input terminal of the operational amplifier 70, E2 is a measuring point provided for measuring the voltage at the non-inverting input terminal, and the voltage dividing resistor 13 14 are assumed to be R = 33 kΩ. For the waveform display, the resistance value of the load current detection resistor 16 is Rs = 2Ω, but it is desirable to use a lower resistance value.

  The waveform shown in FIG. 8 shows how the voltages of E0, E1, and E2 with respect to the GND potential (0 V) change according to the PWM waveform. In order to obtain these voltage waveforms, the speaker load 15 was driven with a PWM waveform corresponding to a sine wave signal input.

  It can be seen that in the method of measuring the potential difference between both ends of the load current detection resistor 16, a pulse waveform having a voltage higher than that of E0 is applied to the input terminals E1 and E2 of the operational amplifier 705.

  On the other hand, in the current detection circuit 1 of the present embodiment, the pulse component can be greatly reduced at the connection point of the voltage dividing resistor. Therefore, the current detection circuit 1 of the present embodiment is output from a digital power amplifier such as a PWM output. When used for control, it is not necessary to use a special operational amplifier for a pulse signal having a high slew rate and a large common mode rejection ratio for the difference detection unit 17, and the operational amplifier used for the difference detection unit 17 can be a normal operational amplifier. Contributes to cost reduction.

  When used for output control of a digital power amplifier such as PWM output, it is sufficient to drive with a positive / negative binary pulse waveform, so that the first and second amplifiers 121 and 122 include, for example, C-MOS inverters. Complementary outputs obtained by connecting circuits in series can also be used as BTL outputs.

In the first embodiment, a current detection circuit using a BTL amplifier with both power supplies is disclosed. In the second embodiment, a current detection circuit in the case of using a single power supply BTL amplifier will be described. Hereinafter, the configuration and operation of the current detection circuit of this embodiment will be described with reference to FIG. FIG. 2 is a circuit diagram showing a configuration of the current detection circuit 2 of the present embodiment. As shown in the figure, the current detection circuit 2 of this embodiment includes a signal input unit 10, a feedback control unit 21, a BTL amplifier 22, a first voltage dividing resistor 13, and a second voltage dividing resistor 14. And a third voltage dividing resistor 23, a fourth voltage dividing resistor 24, a load 15, a load current detecting resistor 16, and a difference detecting unit 27. The BTL amplifier 22 includes a first amplifier 221 and a second amplifier 222. In the present embodiment, the BTL amplifier 22 is a single power supply amplifier having a positive power supply voltage + _Vcc and a negative power supply voltage 0.

The first amplifier 221 outputs a predetermined signal. Using the function V (t) representing the voltage of the amplifier output signal with the time t as a variable and the amplitude ratio n, the direct current component of the signal output from the first amplifier 221 is V _B, and the output signal of the first amplifier 221 the assumed to represent the nV (t) + _{V B.}

The second amplifier 222 outputs a -V (t) + _{V B} is the signal of the output signal and the opposite phase of the first amplifier 221. The load 15 connects the output terminal of the first amplifier 221 and the output terminal of the second amplifier 222. The load current detection resistor 16 is connected in series to the load 15 as in the first embodiment. The resistance value of the first to fourth voltage dividing resistors 13 through 24 is sufficiently large, the current I _L flowing through the load 15 and the load current detecting resistor 16 is assumed to deemed equal to approximately.

The third and fourth voltage dividing resistors 23 and 24 are voltage dividing resistors that divide the potential difference between the output terminal of the first amplifier and the output terminal of the second amplifier at a predetermined ratio. When the resistance value of the third voltage dividing resistor is nR _X and the resistance value of the fourth voltage dividing resistor is R _X , the potential at the connection point of the third and fourth voltage dividing resistors 23 and 24 is the reference potential. Equals V _B. Specifically, the potential V _C ′ at the connection point of the third and fourth voltage dividing resistors 23 and 24 is

It becomes. On the other hand, the potential V _{C at} the connection point of the first and second voltage dividing resistors 13 and 14 is

It becomes. As shown in the above calculation formula, the amplitude ratio of the voltages of the output signals of the first and second amplifiers 221 and 222 is n: 1, and the resistance values of the first and second voltage dividing resistors 13 and 14 are as follows. Similarly, when the ratio of n is n: 1, the term V (t) is canceled as in the first embodiment. If n = 1, the amplitude ratio of the voltages of the output signals of the first and second amplifiers 121 and 122 is 1: 1, and the ratio of the resistance values of the first and second voltage dividing resistors 13 and 14 is also 1: The ratio of the resistance values of the first, third, and fourth voltage dividing resistors 23 and 24 is also 1: 1.

  As shown in the figure, the difference detection unit 27 is connected to the connection point of the first and second voltage dividing resistors 13 and 14 and the connection point of the third and fourth voltage dividing resistors 23 and 24. And a function of detecting a potential difference between two points. The difference detector 27 is a potential at the connection point of the first and second voltage dividing resistors 13 and 14.

And the potential difference of the potential V _B at the connection point of the third and fourth voltage dividing resistors 23 and 24, that is,

The basis, and the value n, based on the resistance value R _S of the load current detecting resistor to detect the current I _L flowing through the load. The difference detection unit 27 feeds back the detected current _IL to the feedback control unit 21. Feedback controller 21 performs a predetermined control corresponding to the current I _L.

  According to the current detection circuit 2 of the present embodiment, in addition to the configuration of the first embodiment, since the potential at the connection point of the third and fourth voltage dividing resistors becomes the reference potential, the single power source BTL amplifier is used. Even if it exists, there exists an effect similar to Example 1. FIG.

In the second embodiment, the potential at the connection point of the third and fourth voltage dividing resistors 23 and 24 that divides the potential difference between the output terminal of the first amplifier 221 and the output terminal of the second amplifier 222 is set as the reference potential V _B. A current detection circuit using a single power supply BTL amplifier was realized. This embodiment is constructed so as to acquire the potential of the fifth and dividing resistor connection point of the sixth dividing the potential difference between the positive power supply terminal and the negative electrode power terminal BTL amplifier at a predetermined ratio as a reference potential V _B It is a modification of Example 2. Hereinafter, the configuration and operation of the current detection circuit 3 of this embodiment will be described with reference to FIG. FIG. 3 is a circuit diagram showing a configuration of the current detection circuit 3 of the present embodiment. As shown in the figure, the current detection circuit 3 of this embodiment includes a signal input unit 10, a feedback control unit 21, a BTL amplifier 22, a first voltage dividing resistor 13, and a second voltage dividing resistor 14. A fifth voltage dividing resistor 33, a sixth voltage dividing resistor 34, a load 15, a load current detection resistor 16, and a difference detection unit 27. The components other than the sixth voltage dividing resistor 34 are the same as those in the second embodiment.

As shown in FIG. 3, the fifth voltage-dividing resistor 33 and the sixth voltage-dividing resistor 34 have the potential difference between the positive power supply terminal and the negative power supply terminal of the first or second amplifiers 221 and 222 at a predetermined ratio. Divide pressure. The resistance ratio of the fifth voltage dividing resistor 33 and the sixth voltage dividing resistor 34 is m: 1. The value m is assumed to be adjusted so that the potential of the fifth voltage dividing resistors 33 connection point of the sixth voltage dividing resistor 34 becomes the reference potential V _B.

  According to the current detection circuit 3 of the present embodiment, in addition to the configuration of the first embodiment, since the potential at the connection point of the fifth and sixth voltage dividing resistors becomes the reference potential, the single power source BTL amplifier is used. Even if it exists, there exists an effect similar to Example 1. FIG.

In the current detection circuits of Examples 1 to 3, the load current detection resistor 16 was connected to the negative phase output terminal side. The fourth embodiment discloses a current detection circuit in which the load current detection resistor 16 is connected to the positive phase output terminal side. Hereinafter, the current detection circuit of this embodiment will be described with reference to FIG. FIG. 4 is a circuit diagram showing a configuration of the current detection circuit 4 of the present embodiment. As shown in the figure, in the BTL amplifier 12a of the current detection circuit 4 of the present embodiment, the first amplifier 121a has a negative phase output of −nV (t) +0 (reference potential V _B = 0), the second amplifier 122a is a positive phase output of V (t) +0. Other structural requirements of the current detection circuit 4 are the same as those in the first embodiment. Therefore, the load current detection resistor 16 is directly connected to the second amplifier 122a which is a positive phase output without passing through the load 15.

In this case, the potential V _{C at} the connection point of the first and second voltage dividing resistors 13 and 14 is

Thus, V _C has the same value as in the first embodiment. Note that the load current detection resistor may exist on both the positive phase side and the negative phase side. In this case, it is possible from the difference of potential and a reference potential V _B obtained a potential difference across the load if there is a difference in the resistance values divides and detects the load current I _L.

  According to the current detection circuit 4 of this embodiment, the load current detection resistor 16 is connected to the positive phase output terminal side, and the same effect as that of the first embodiment is obtained.

Hereinafter, the configuration and operation of the current detection circuit according to the fifth embodiment in which the difference detection unit 17 according to the first embodiment is configured by an addition circuit will be described with reference to FIG. FIG. 5 is a circuit diagram showing the configuration of the current detection circuit 5 of the present embodiment. As shown in the figure, the current detection circuit 5 of the present embodiment includes an operational amplifier 57, a seventh voltage dividing resistor 58, and an eighth voltage dividing resistor 59 instead of the difference detection unit 17 of the first embodiment. Including. Other configuration requirements are the same as those in the first embodiment. The connection point between the inverting input terminal of the operational amplifier 57 and the first and second voltage dividing resistors 13 and 14 is connected by an eighth voltage dividing resistor 59. The non-inverting input terminal of the operational amplifier 57 is connected to the ground. The inverting input terminal and the output terminal of the operational amplifier 57 are connected by a seventh voltage dividing resistor 58. The voltage at the output terminal of the operational amplifier 57 and V _O, and the resistance value of the seventh voltage dividing resistors 58 and R _Y, the resistance value of the dividing resistor 59 of the eighth and R _Z, to the inverting input terminal of the operational amplifier 57 Since the inflowing current is 0, the potential V ₋ of the inverting input terminal of the operational amplifier 57 is expressed by the following equation.

Since the potential V ₋ is an imaginary ground,

It becomes. As before,

Therefore, substituting this into the above formula,

Therefore,

Next, obtaining a voltage output proportional to the load current I _L.

According to the current detection circuit 5 of the present embodiment, an effect similar to that of the current detection circuit 1 of the first embodiment is obtained using the adder circuit. The same effect can be obtained even when the above-described _RZ is almost 0 and the eighth voltage dividing resistor 59 can be ignored.

Hereinafter, the configuration and operation of the current detection circuit according to the sixth embodiment, which is a modification of the current detection circuit using the single power supply BTL amplifier disclosed in the second and third embodiments, will be described with reference to FIG. FIG. 6 is a circuit diagram showing the configuration of the current detection circuit 6 of this embodiment. In this embodiment, instead of the third to sixth voltage dividing resistors 23 to 34 that are configured to take out the reference potential V _B in the second and third embodiments, a power source that is another power source that supplies the reference potential V _B is used. 69. As shown in the figure, the difference detection unit 27, first, a connection point of the second voltage dividing resistors 13 and 14, power supply 69 based on the difference between the reference potential V _B supplies a current flowing through the load 15 _IL is detected.

  According to the current detection circuit 6 of the present embodiment, a current detection circuit using a single power source BTL can be realized using the power source 69 which is a separate power source, as in the second and third embodiments.

DESCRIPTION OF SYMBOLS 1 Current detection circuit 10 Signal input part 11 Feedback control part 12 BTL amplifier 121 1st amplifier 122 2nd amplifier 13 1st voltage dividing resistor 14 2nd voltage dividing resistor 15 Load 16 Load current detection resistance 17 Difference detection part 2 Current detection circuit 21 Feedback control unit 22 BTL amplifier 221 1st amplifier 222 2nd amplifier 23 3rd voltage dividing resistor 24 4th voltage dividing resistor 27 Difference detection unit 3 Current detection circuit 33 5th voltage dividing resistor 34 sixth voltage dividing resistor 4 current detection circuit 12a BTL amplifier 121a first amplifier 122a second amplifier 5 current detection circuit 57 operational amplifier 58 seventh voltage dividing resistor 59 eighth voltage dividing resistor 6 current detection circuit 69 power supply 7 Current detection circuit 70 Potential difference detection circuit 701 First resistor 702 Second resistor 703 Third resistor 704 Fourth resistor 705 Operational amplifier

Claims (6)

A first amplifier that outputs a predetermined signal;
A second amplifier for outputting a signal having a phase opposite to that of the output signal of the first amplifier;
First and second voltage dividing resistors for dividing a potential difference between both ends of a load connecting an output terminal of the first amplifier and an output terminal of the second amplifier, wherein the first and second voltage dividing resistors The first and second resistance values are determined such that the amplitude of the output signal of the first amplifier and the amplitude of the output signal of the second amplifier cancel each other at the connection point of the voltage dividing resistor. And the partial pressure resistance of
A load current detection resistor connected in series to the load;
The potential difference between the potential at the connection point of the first and second voltage dividing resistors and a reference potential which is a predetermined potential, the ratio of the resistance values of the first and second voltage dividing resistors, and the load current detection A difference detection unit that detects a current flowing through the load based on a resistance value of the resistor;
Including current detection circuit. Let n be any positive number,
A first amplifier that outputs a signal having a predetermined reference potential;
A second amplifier that outputs a signal having the predetermined reference potential, the signal having a phase opposite to that of the output signal of the first amplifier and an amplitude ratio of n: 1 with respect to the signal of the first amplifier;
First and second voltage dividing resistors for dividing a potential difference between both ends of a load connecting the output terminal of the first amplifier and the output terminal of the second amplifier to n: 1;
A load current detection resistor connected in series to the load;
Difference detection for detecting a current flowing through the load based on a potential difference between a connection point of the first and second voltage dividing resistors and the reference potential, the n, and a resistance value of the load current detection resistor. And
Including current detection circuit. The current detection circuit according to claim 1 or 2,
A current detection circuit using the reference potential as a ground. The current detection circuit according to claim 1 or 2,
Including third and fourth voltage dividing resistors for dividing the potential difference between the output terminal of the first amplifier and the output terminal of the second amplifier at a predetermined ratio;
A current detection circuit in which the reference potential is a potential at a connection point of the third and fourth voltage dividing resistors. The current detection circuit according to claim 1 or 2,
Including fifth and sixth voltage dividing resistors for dividing the potential difference between the positive power supply terminal and the negative power supply terminal of the first or second amplifier at a predetermined ratio;
A current detection circuit in which the reference potential is a potential at a connection point of the fifth and sixth voltage dividing resistors. The current detection circuit according to claim 1 or 2,
A current detection circuit including a power supply for supplying the reference potential;

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