TWI414801B - Current detection circuit - Google Patents

Abstract

Provided is a current detecting circuit which reliably detects an excess current flowing in a load without making the circuit configuration complicated and increasing the circuit area in a differential voltage circuit. The current detecting circuit is provided with: an input circuit which is connected to the current detecting node of a circuit a current of which is to be detected and outputs a minus current flowing in the circuit as a plus voltage; and the differential voltage circuit which compares the plus voltage outputted from the input circuit with a reference voltage and outputs the comparison results as current detection signals.

Description

Current detection circuit

The present invention is a current detecting circuit for detecting a current flowing in a circuit such as a power source.

The ninth and tenth drawings are related descriptions of conventional current detecting circuits. The ninth diagram is a schematic diagram of a power supply circuit and a current detecting circuit for detecting a current flowing through the power supply circuit. The tenth diagram is a schematic diagram of the circuit structure of the differential voltage circuit used in the current detecting circuit.

In the ninth diagram, the power supply circuit 100 is composed of a switch SW, a diode D, a resistor R, a coil L, and a current collector C. One end of the switch SW is connected to the DC power supply Vcc and the other end is connected to the cathode terminal of the diode D. The anode terminal of the diode D is connected to one end of the resistor R, and the other end of the resistor R is grounded. The connection point of the diode D and the resistor R is connected to the node A. The resistance of the resistor R is set to r, the node A is connected to the current detecting circuit 300, one end of the coil L is connected to the cathode terminal of the diode D, and the other end is connected to one end of the output terminal OUT and the current collector C. The other end of the current collector C is grounded.

In the power supply circuit 100, when the switch SW is in the ON state, the DC voltage supplied from the DC power supply Vcc is supplied to the power supply (load) connected to the output terminal OUT by the predetermined power supply voltage through the coil L and the current collector C. Further, in the power supply circuit 100, the diode D and the resistor R are arranged in an overcurrent protection circuit 101A which can prevent a sudden applied voltage from flowing to the load side when the switch SW is switched ON. For example, when a short circuit is generated on the load side connected to the output terminal OUT, the overcurrent (negative current) IO flows to the overcurrent protection circuit as shown in FIG. 9, and the negative voltage corresponding to the overcurrent amount is input to the node connected to the node. A current detecting circuit 300 of A. The current detecting circuit 300 is provided with a differential circuit 301 whose non-inverting input terminal (+) is connected to the node A, the inverting input terminal (-) is grounded, and the output terminal is connected to the node B. The differential voltage circuit 301 outputs a current detection signal to the node B when the potential difference between the ground potential of the non-reverse input terminal (+) and the inverting input terminal (-) exceeds a predetermined level, that is, the differential voltage circuit 301 is compared. The circuit is used.

The circuit composition of the differential voltage circuit 301 is as shown in the tenth diagram. In the tenth diagram, the differential voltage circuit 301 is composed of a first current source I1, a second current source I2, PMOS transistors (TR1 to TR3), and NMOS transistors TR4 and TR5. The first current source I1 is simultaneously connected to the source terminal of the PMOS transistor TR1 and the gate terminal of the PMOS transistor TR2. The gate terminal of the PMOS transistor TR1 is connected to the non-inverting input terminal (+), and the gate terminal is grounded. The second current source I2 is connected to the respective source terminals of the PMOS transistors TR2, TR3, and the NMOS terminal of the PMOS transistor TR2 is connected to the source terminal of the NMOS transistor TR4. The gate terminal of the PMOS transistor TR3 is connected to the inverting input terminal (-), and the gate terminal is connected to the source terminal of the NMOS transistor TR5 and the output terminal OUT. The gate terminal of the NMOS transistor TR4 is connected to the gate terminal of the NMOS transistor TR5, and the gate terminal is grounded. The NMOS terminal of the NMOS transistor TR5 is grounded.

The PMOS transistor TR1 is turned on (ON) by a negative voltage that responds to an overcurrent amount input to the non-inverting input terminal (+), and a divided voltage corresponding to a constant current supplied from the first current source I1. (Positive voltage) is input to the gate terminal of the PMOS transistor TR2. The PMOS transistor TR1 and the first power supply stream I1 are arranged as a positive voltage input circuit 301A by inputting a negative voltage input to the non-inverting input terminal (+) as a positive voltage to the gate terminal of the PMOS transistor R2.

The PMOS transistors TR2 and TR3 and the NMOS transistors TR4 and TR5 constitute a differential voltage circuit unit 301B. The differential voltage circuit unit 301B operates in response to a voltage difference between the positive voltage input from the positive voltage input circuit 301A and the ground potential of the inverting input terminal (-), and outputs a current detection signal from the output terminal OUT as Voltage signal. That is, when the PMOS transistor TR1 is turned on (ON) by the input of the negative voltage of the positive voltage input circuit 301A, the PMOS transistor TR2 is turned ON when the positive voltage exceeds the threshold Vth, and the positive voltage and the inverting input terminal (-) When the voltage difference of the ground potential is increased beyond the predetermined range and the operation is started, the differential voltage circuit unit 301B outputs the current detection signal Id as a voltage signal from the output terminal OUT.

Further, a method for detecting the operation in a circuit such as a power source is described in Japanese Laid-Open Patent Publication No. 2005-229563. In this power supply voltage monitoring circuit, the positive and negative power supply voltages supplied by the power amplifier when the power is turned on (ON) or turned off (OFF) are monitored, and when an abnormality is detected, the switching circuit is forcibly turned off to prevent abnormal applied voltage. Operation.

As shown in the ninth figure, when the overcurrent I ₀ as the load current flows through the current detecting circuit 300, the node A generates a negative voltage, so that it is required to be input in the differential voltage circuit 301 as shown in the tenth diagram. A positive voltage input circuit corresponding to a positive voltage of an overcurrent amount. For example, the resistance value of the resistor R in the power supply circuit 100 is 10 mΩ, and the potential of the node A becomes -100 mV when the overcurrent (negative current) I _{0 of} -10 A flows. That is to say, when the overcurrent I ₀ flows through the inside of the power supply circuit 100, a negative voltage is generated due to the resistor R, and this negative voltage constitutes a non-inverting input terminal (+) input from the node A to the differential voltage circuit 301. Circuit. Therefore, in order for the differential voltage circuit 301 to operate normally, a positive voltage input circuit 301A having a circuit configuration as shown in the tenth embodiment is required. This circuit configuration complicates the circuit configuration inside the differential voltage circuit 301 and increases the cost of the current detecting circuit. Further, in order to increase the range of the positive voltage input to the differential voltage circuit unit 301B, the positive voltage input circuit 301A is disposed in the differential voltage circuit unit 301B, and the MOS transistors TR2 to TR5 in the differential voltage circuit unit 301B are required to expand the circuit mode in response to the expansion of the operating voltage. The circuit area also increases.

In view of the above problems, it is an object of the present invention to provide a current detecting circuit that can accurately detect an overcurrent flowing through a load without complicating the circuit arrangement in the differential voltage circuit and without enlarging the circuit area.

A current detecting circuit according to an embodiment of the present invention is characterized in that it is connected to a current detecting node of a circuit as a current detecting object, and has an input which can be compared to a negative current flowing through the above circuit as a positive voltage output. The circuit and the positive voltage and the reference voltage output from the above circuit, and the comparison result thereof is used as a differential voltage circuit for outputting the current detection signal.

The present invention can provide a current detecting circuit that does not need to complicate the circuit configuration in the differential voltage circuit, and does not need to enlarge the circuit area, that is, can reliably detect an overcurrent flowing through the load.

An embodiment of the current detecting circuit of the present invention will be described in detail below with reference to the drawings. The current detecting circuit shown in this embodiment is for detecting an overcurrent flowing as a load through the power supply circuit, but the load to which the current detecting circuit can be applied is not limited to the power supply circuit.

First embodiment:

The first diagram shows a schematic configuration diagram of a current detecting circuit 200 connected to the power supply circuit (load circuit) 100 in the first embodiment. In addition, the power supply circuit 100 shown in the first figure is the same circuit configuration as the power supply circuit 100 shown in the ninth figure, and only the same reference numerals will be given, and the description of the arrangement will be omitted.

In the first figure, the current detecting circuit 200 is composed of an input circuit 201 and a differential voltage circuit 202. The input portion of the input circuit 201 is connected to the current detecting node A of the power supply circuit 100, and the output portion is connected to the differential voltage circuit 202 by the node C. The input circuit 201 outputs the negative current I ₀ flowing through the current detecting node A as a positive voltage to the node C. The differential input voltage reference circuit 202 based voltage of the positive voltage and a later-described output circuit 201 for comparison, a comparison result output current detection signal _d is as I B from the node.

The second figure is a schematic diagram showing an example of a circuit configuration diagram of the input circuit 201 and the differential voltage circuit 202 shown in the first figure. In the second diagram, the current detecting circuit 200 is composed of a first constant voltage source V1, a second constant voltage source V2, an input circuit 201, and a differential voltage circuit 202. The first constant voltage source V1 generates the first reference voltage VR1, and the second constant voltage source V2 generates the second reference voltage VR2.

In the second figure, the input circuit 201 is composed of resistors R1 and R2. One end portion (first end portion) of the resistor R1 (first resistor) is connected to the current detecting node A, the other end portion (second end portion) is connected to one end of the resistor R2, and the non-reverse of the differential voltage circuit 202 Phase input terminal (+) (first input terminal). One end portion (first end portion) of the resistor R2 (second resistor) is connected to the other end portion of the resistor R1 and the non-inverting input terminal (+) (first input terminal), and the other end portion (second end portion) The part is connected to the second constant voltage source V2. Further, the resistance value of the resistor R1 is set to r1, and the resistance value of the resistor R2 is set to r2. In the second figure, the connection point of the resistors R1 and R2 is taken as the node C. The input circuit 201 constitutes a negative current I ₀ flowing through the overcurrent protection circuit 101A and the resistor R is generated at the current detecting node A. The voltage difference between the negative voltage rI ₀ and the second reference voltage VR2 of the second constant voltage source V2 is a voltage dividing circuit that is divided and output as a positive voltage.

In the second figure, the differential voltage circuit 202 is constructed by an operational amplifier. The inverting input terminal (-) (second input terminal) of this operational amplifier is connected to the first constant voltage source V1. The differential voltage circuit 202 compares the positive voltage input from the input circuit 201 to the non-inverting input terminal (+) with the first reference voltage VR1 input from the first constant voltage source V1 to the inverting input terminal (-). The comparison result is output as a current detection signal I _d to the node B.

The third figure is a schematic diagram of the circuit configuration in the differential voltage circuit 202 shown in the second figure. In the third embodiment, the same portions as those in the differential voltage circuit portion 301B shown in the ninth diagram are denoted by the same reference numerals. In the third diagram, the differential voltage circuit 202 is composed of a second current source I2, PMOS transistors TR2 and TR3, and NMOS transistors TR4 and TR5.

The second current source I2 is commonly connected to the respective source terminals of the PMOS transistors TR2, TR3. The PMOS transistor TR2 is connected to the non-inverting input terminal (+) (node C) of the gate terminal, and the 汲 terminal is connected to the source terminal of the NMOS transistor TR4. The PMOS transistor TR3 is connected to the inverting input terminal (-) of the gate terminal, and the drain terminal is connected to the source terminal of the NMOS transistor TR5 and the output terminal OUTPUT. The gate terminal of the PMOS transistor TR4 is connected to the gate terminal of the NMOS transistor TR5, and the gate terminal is grounded. The NMOS terminal of the NMOS transistor TR5 is grounded.

Next, in the input circuit 201 shown in the second figure, the condition for generating a positive voltage from the node C will be described with reference to the fourth figure. In the fourth diagram, the current flowing through each portion of the input circuit 201 is set to I ₁ to I ₃ , and the voltage applied from both ends of the input circuit 201 is assumed to be VR2-rI ₀ . The condition for changing the voltage Vc of the node C to a positive voltage will be described below based on this figure.

As shown in the fourth figure, when the current flowing through the resistor R1 is I ₁ , the current of the resistor R2 is I ₂ , and the current flowing through the node C is I ₃ , the voltage Vc of the node C can be expressed by the following formula (1) ) said.

Vc=VR2-I ₂ ‧r2‧‧‧(1)

The current I ₁ can be expressed by the following formula (2).

I ₁ =(Vc-r‧I ₀ )/r1‧‧‧(2)

The current I ₁ can be expressed by the following formula (3).

I ₁ =I ₂ +I ₃ ‧‧‧(3)

At this time, since I ₃ =0, it becomes I ₁ =I ₂ .

I ₁ =I ₂ =(VR2-Vc)/r2‧‧‧(4)

If this mathematical formula (2) is applied, the voltage Vc can be expressed by the following formula (5).

Vc={r1(VR2-Vc)/r2}+r‧I ₀ ‧‧‧(5)

This formula (5) can be expressed by the following formula (6).

r2‧Vc=r1‧VR2-r1‧Vc+r‧r2‧I ₀ ‧‧‧(6)

This formula (6) can be expressed by the following formula (7).

(r1+r2)Vc=r1‧VR2+r‧r2‧I ₀ ‧‧‧(7)

The voltage Vc obtained by using this equation (7) can be expressed by the following formula (8).

_{Vc = (r1‧VR2 + r‧r2‧I 0)} / (r1 + r2) ‧‧‧ (8)

Therefore, the voltage Vc of the node C can be expressed by the respective resistance values r1 and r2 of the resistors R1 and R2 and the second reference voltage VR2 of the second constant voltage source V2.

In the first embodiment, the respective resistance values r1 and r2 of the resistors R1 and R2 and the second reference voltage VR2 of the second constant voltage source V2 are set such that the voltage Vc shown in the formula (8) becomes a positive voltage. The value of (Vc>0). In the first embodiment, the relationship between the first reference voltage VR1 of the first constant voltage source V1 and the second reference voltage VR2 of the second constant voltage source V2 is set to VR1 < VR2.

In the second diagram, the first reference voltage VR1 of the first constant voltage source V1 is set to 0.65 V, and the second reference voltage VR2 of the second constant voltage source V2 is set to 1.2 V, and the electric groupers R1 and R2 of the input circuit 201 are set. Each of the resistance values is r1 and r2 is set to 10 kΩ. The resistance value r of the power pack R of the power supply circuit 100 is set to 10 Mω, and the overcurrent (negative current) I ₀ flowing through the current protection circuit 101A is set to -10 A. The voltage of the lower node A becomes I ₀ ‧ r = 10 ^{- 2} × (-10) = -100 mV, and the voltage of the node C can be obtained from the above formula (8). At this time r1=r2,

Vc=(r1‧VR2+r‧r2‧I ₀ )/(r1+r2)=(1.1×10 ⁴ )/(2×10 ⁴ )=1.1/2=0.55V

As described above, it is connected to the input circuit 201. The node C generates a positive voltage corresponding to the overcurrent I ₀ , and the positive voltage corresponding to the overcurrent I ₀ is input to the non-inverting input terminal (+) of the differential voltage circuit 202. Therefore, the differential voltage circuit 202 shown in the second figure does not require the positive voltage input circuit 301A, and the circuit configuration can be simplified and made easy to design. Due to the connection of the input circuit 201, the voltage range of the load voltage input to the differential voltage circuit 202 corresponding to the amount of overcurrent is reduced. Therefore, it is not necessary to enlarge the operating voltages of the MOS transistors TR2 to TR5 constituting the differential voltage circuit 202, and it is not necessary to enlarge the circuit pattern, with the result that the cost of the current detecting circuit 200 is suppressed.

The operating voltage of the differential voltage circuit 202 in the first embodiment can be reduced to be smaller than the operating voltage of the differential voltage circuit 300 shown in the fourth figure, so that the circuit pattern can be reduced and the cost of the current detecting circuit 200 can be pursued. reduce. On the other hand, the differential voltage circuit 202 of the first embodiment only needs to add the resistors R1 and R2 as the input circuit 201. Therefore, not only the circuit configuration is simplistic, but also the cost increase of the current detecting circuit 200 is suppressed as compared with the positive voltage input circuit 301A. In the differential voltage circuit 202 of this embodiment, although the first constant voltage source V1 and the second constant voltage source V2 are connected, the constant voltage source can use the power source connected to the differential voltage circuit 202 (not shown). Therefore, the increase in cost can also be suppressed.

By applying the current detecting circuit 200 of the first embodiment to a load such as the power supply circuit 100, it is possible to reliably detect an overcurrent flowing through the load, and it is possible to prevent an abnormal situation caused by an overcurrent. As a result, the reliability of the load connected to the power supply circuit 100 of the current detecting circuit 200 or the like is also improved.

Second embodiment:

The second embodiment is an example in which the resistors R1 and R2 in the input circuit 201 shown in the second figure are changed by a variable resistor. The fifth diagram is a schematic diagram of the circuit configuration of the input circuit 201 in the second embodiment. The input circuit 201 in the fifth diagram is composed of a variable resistor R11 (first resistor) and a variable resistor R12 (second resistor).

As shown in FIG. 5, the input circuit 201 is constituted by a variable resistor R11 (first resistor) and a variable resistor R12 (second resistor), so that the respective resistance values can correspond to the differential voltage circuit 202. The specifications of the load side machine can be arbitrarily adjusted. That is, as described above, the respective resistance values of the variable resistors R11 and R12 can be adjusted such that the voltage difference between the negative voltage generated by the current detecting node A and the second reference voltage VR2 is a positive voltage.

As shown in FIG. 6, a resistance value adjusting unit 203 is provided to adjust the respective resistance values of the variable resistors R11 and R12 from the outside. The resistance value adjustment unit 203 is provided with an operation unit (not shown) that can externally adjust the resistance value, so that the resistance values of the variable resistors R11 and R12 can be easily adapted to the connected load device specifications. Wait for adjustment.

However, the fifth diagram shows an example in which the input circuit 201 is constituted by a variable resistor R11 (first resistor) and a variable resistor R12 (second resistor), but it is also possible to replace either one with a fixed resistor. And constitute. In this case, the arrangement of the resistance value adjusting unit 203 may be performed by adjusting the resistance value of one of the variable resistors.

Third embodiment:

In the third embodiment, the resistors R1 and R2 in the input circuit 201 shown in the second figure are formed by a plurality of resistors, and the connection of the plurality of resistors is switched by a resistor value switching unit provided outside. example. The seventh diagram is a circuit configuration diagram of the input circuit 201 and the resistance value switching unit 204 in the third embodiment. In the input circuit 201 in the seventh diagram, the resistor R1 (first resistor) is formed by a plurality of resistors R21A and R21B, and the resistor R2 (second resistor) is formed by a plurality of resistors R22A and R22B.

The respective connection nodes of the resistors R21A and R21B and the respective nodes of the resistors R22A and R22B are connected to the resistance value switching unit 204. The resistance value switching unit 204 activates one or both of the resistors R21A and R21B by short-circuiting or opening the connection nodes, and one or both of the resistors R22A and R22B are effective, and have a function of switching the resistance value. The resistance value switching unit is provided with an operation unit (not shown) that can externally adjust the resistance value, so that the resistance values of the resistors R21A and R21B and the resistors R22A and R22B are easily adapted to the connected load. The device specifications are switched.

As shown in the seventh figure, the input circuit 201 is composed of a resistor R1 (first resistor) composed of a plurality of resistors R21A and R21B, and a resistor R2 (second resistor) is composed of a plurality of resistors R22A and R22B. The connection of the plurality of resistors R21A, R21B, R22A, and R22B is switched by the resistance value switching unit 204 provided outside. With this arrangement, the respective resistance values can be arbitrarily adjusted in accordance with the specification changes of the differential voltage circuit 202 and the load side device. That is, as described above, the resistance values of the plurality of resistors R21A, R21B, R22A, and R22B can be switched such that the voltage difference between the negative voltage generated by the current detecting node A and the second reference voltage VR2 can be changed to a positive voltage.

Fourth embodiment:

The fourth embodiment shows an example in which the input circuit 201 is connected from the outside of the current detecting circuit 200. The eighth diagram is a schematic configuration diagram of the input circuit 201 and the current detecting circuit 200 connected to the power supply circuit (load circuit) 100 in the fourth embodiment. In addition, the power supply circuit 100 shown in FIG. 8 is the same as the power supply circuit 100 shown in the figure, and the same reference numerals are attached thereto, and the description of the configuration is omitted.

The current detecting circuit 200 in the eighth diagram is provided with a differential voltage circuit 202 as shown in the third figure. The input circuit 201 is connected between the current detecting node A on the load side and the node C on the side of the current detecting circuit 200. At this time, the input circuit 201 can be applied to the input circuit 201 shown in the second or fifth figure, and further connected to the input circuit 201 of the resistance value adjusting unit 203 shown in FIG. 6, or connected to the seventh figure. The input circuit 201 of the resistance value switching unit 204 can also be applied.

In the fourth embodiment, by connecting the input circuit 201 to the outside of the current detecting circuit 200, the current detecting circuit shown in the above-described first embodiment is used with respect to the current detecting circuit 200 constituted only by the differential voltage circuit 202. 200 becomes an overcurrent detection function. Therefore, the input circuit 201 is connected to the current detecting circuit 200 composed of the existing differential voltage circuit 202, and by adjusting the resistance value, the overcurrent detecting function on the load side can be easily added. Therefore, when the current detecting circuit 200 constituted by the differential voltage circuit 202 is wafer-formed, its application range to the load can be expanded.

100. . . Power circuit

200. . . Current detection circuit

201. . . Input circuit

202. . . Differential voltage circuit

203. . . Resistance value adjustment unit

204. . . Resistance value switching unit

R1, R2, R21A, R21B, R22A, R22B. . . Resistor

R11, R12. . . Variable resistor

V1. . . 1st constant voltage source

V2. . . 2nd constant voltage source

VR1. . . First reference voltage

VR2. . . Second reference voltage

The first diagram is a schematic configuration diagram of a current detecting circuit according to a first embodiment of the present invention.

The second drawing is a circuit configuration diagram of the current detecting circuit of the first embodiment of the present invention.

The third figure is a circuit configuration diagram of the differential voltage circuit of the second diagram of the present invention.

The fourth figure is a diagram showing the relationship between voltage and current of each part in the input circuit of the second diagram of the present invention.

Fig. 5 is a circuit configuration diagram of an input circuit of a second embodiment of the present invention.

Fig. 6 is a view showing the configuration of a resistance value adjusting portion connected to an input circuit in the fifth diagram of the present invention.

The seventh diagram is a circuit configuration diagram in which the resistance value switching portion of the third embodiment of the present invention is connected to an input circuit.

The eighth diagram is a circuit configuration diagram of the external connection input circuit of the current detecting circuit of the fourth embodiment of the present invention.

The ninth diagram is a schematic diagram of the circuit configuration of a conventional current detecting circuit.

The tenth diagram is a circuit configuration diagram of the differential voltage circuit of the ninth diagram.

100. . . Power circuit

200. . . Current detection circuit

201. . . Input circuit

202. . . Differential voltage circuit

R1, R2. . . Resistor

V1. . . 1st constant voltage source

V2. . . 2nd constant voltage source

VR1. . . First reference voltage

VR2. . . Second reference voltage

Claims (11)

A current detecting circuit is connected to a current detecting node of a circuit to be used as a current detecting object, the current detecting circuit comprising at least: an input circuit for outputting a negative current flowing through the circuit as a positive voltage; a voltage circuit for comparing a positive voltage outputted by the input circuit with a reference voltage, and outputting the comparison result as a current detection signal; wherein the reference voltage includes a first constant voltage source for outputting the first reference voltage, a second constant voltage source for outputting a second reference voltage; a first end of the input circuit is connected to the current detecting node, and a second end is connected to the second constant voltage source, and is output from the third end a positive voltage corresponding to a negative current flowing through the circuit; the differential voltage circuit having a first input terminal connected to the third end and a second input terminal connected to the first constant voltage source Comparing the positive voltage input to the first input terminal with the first reference voltage input to the second input terminal, and comparing the result as a current detection signal Output. The current detecting circuit according to claim 2, wherein the overcurrent detecting signal is output when the positive voltage of the differential voltage circuit is higher than the first reference voltage. The current detecting circuit according to claim 1, wherein the input circuit has a voltage dividing circuit, and the negative voltage generated at the current detecting node and the voltage of the second reference voltage corresponding to the amount of the negative current are The difference is output as a positive voltage. The current detecting circuit according to the fourth aspect of the invention, wherein the voltage dividing circuit has a first resistor and a second resistor, and the first end of the first resistor is connected to the first of the input circuit The second end of the first resistor is connected to the third end of the input circuit, and the first end of the second resistor is connected to the third end of the input circuit, the second resistor The second end is connected to the second end of the input circuit. The current detecting circuit according to Item 5, wherein at least one of the first resistor and the second resistor is a variable resistor. The current detecting circuit according to claim 6, wherein the variable resistor has a resistance value adjusting portion that can adjust the resistance value. According to the current detecting circuit of the fifth aspect of the invention, at least one of the first resistor and the second resistor may be replaced by a plurality of resistors. The current detecting circuit according to Item 8 of the patent scope, wherein the circuit has a switchable complex A resistor value switching portion that adjusts a resistance value by a connection point of a plurality of resistors. The current detecting circuit according to the second aspect of the invention, wherein each of the resistance values of the first resistor and the second resistor, the first reference voltage value of the first constant voltage source, and the second reference of the second constant voltage source The voltage values can each be individually set such that a positive voltage is output. The current detecting circuit according to claim 10, wherein the second reference voltage value is set to be higher than the first reference voltage value. The current detecting circuit of claim 1, wherein the input circuit is disposed to be connected to the outside of the current detecting circuit.