Current detection circuit

Abstract

To provide a voltage detection circuit that can detect current change due to a very small signal component with respect to a DC component included in an input signal.SOLUTION: A current detection circuit 1 includes a rectifying element 102, a current control circuit 103, a load element 104, a first transistor 105, which is a field effect transistor of a first conductivity type, and a voltage detection circuit 106 including a voltage detection terminal 115 and a detection result output terminal 116. The current control circuit 103 includes a first terminal 111 connected to a first power source terminal, and a second terminal 112 connected to an anode terminal of the rectifying element 102, a drain of the first transistor 105, and the voltage detection terminal 115 of the voltage detection circuit 106. A gate of the first transistor 105 is connected to an input terminal 101, a cathode terminal of the rectifying element 102, and a second power source terminal through the load element 104. An output terminal 107 is connected to the detection result output terminal 116 of the voltage detection circuit 106.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a current detection circuit. [Background technology]

[0002] A current detection circuit has been disclosed that is used in the light receiving circuit of an infrared remote controller (hereinafter referred to as "infrared remote control"), separates the DC component and signal component contained in the input current from the light receiving photodiode, and detects the signal component. The DC component contained in the input current is derived from ambient light such as sunlight or indoor lighting. The signal component contained in the input current is a signal component derived from the transmitter of the infrared remote control. (See, for example, Patent Document 1, Figures 1 and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-083452 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional current detection circuits detect signal components from the voltage change across a resistor that occurs when a current change due to a signal component flows through the resistor. When the amount of current change due to the signal component is very small, the amount of change in the voltage across the resistor is also very small. When the amount of current change due to the signal component is very small, conventional current detection circuits have the problem of being unable to detect the signal component.

[0005] An object of the present invention is to provide a voltage detection circuit capable of detecting a current change caused by a signal component that is very small in comparison with a DC component contained in an input signal. [Means for solving the problem]

[0006] A voltage detection circuit according to an embodiment of the present invention comprises an input terminal, an output terminal, a rectifying element, a current control circuit, a load element, a first transistor which is a field effect transistor of a first conductivity type, and a voltage detection circuit having a voltage detection terminal and a detection result output terminal, the current control circuit has a first terminal connected to a first power supply terminal, and a second terminal connected to an anode terminal of the rectifying element, a drain of the first transistor, and a voltage detection terminal of the voltage detection circuit, the gate of the first transistor is connected to the input terminal, the cathode terminal of the rectifying element, and a second power supply terminal via the load element, and the output terminal is connected to the detection result output terminal of the voltage detection circuit. Effect of the Invention

[0007] According to the present invention, it is possible to detect a current change caused by a signal component that is very small compared to the DC component contained in the input signal. [Brief description of the drawings]

[0008] [Figure 1] 1 is a circuit diagram illustrating an example of a current detection circuit according to a first embodiment of the present invention. [Diagram 2] 2 is a circuit diagram illustrating an example of a current control circuit of the voltage detection circuit according to the first embodiment. [Diagram 3] 2 is a circuit diagram illustrating an example of a load element of the current detection circuit according to the first embodiment. [Figure 4] 2 is a circuit diagram illustrating an example of a voltage detection circuit of the current detection circuit according to the first embodiment. [Diagram 5] FIG. 6 is a circuit diagram illustrating an example of a current detection circuit according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a circuit diagram illustrating an example of a current control circuit of a voltage detection circuit according to a second embodiment. [Figure 7] FIG. 11 is a circuit diagram illustrating an example of a load element of the current detection circuit according to the second embodiment. [Figure 8] FIG. 11 is a circuit diagram illustrating an example of a voltage detection circuit of a current detection circuit according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) Fig. 1 is a circuit diagram of a current detection circuit 1, which is an example of a current detection circuit according to a first embodiment of the present invention. Figs. 2 to 4 are circuit diagrams showing examples of a current control circuit 103, a load element 104, and a voltage detection circuit 106 of the current detection circuit 1, respectively. The current detection circuit according to the first embodiment will be described with reference to Figs. 1 to 4.

[0010] The overall configuration of a current detection circuit 1 will be described with reference to FIG.

[0011] The current detection circuit 1 includes an input terminal 101, a rectifying element 102, a current control circuit 103, a load element 104, an N-channel MOS transistor (hereinafter referred to as "NMOS transistor") 105 which is an example of a field effect transistor, a voltage detection circuit 106, and an output terminal 107. The current control circuit 103 has a power supply terminal 111 and a current output terminal 112. The load element 104 has a first terminal 113 and a second terminal 114. The voltage detection circuit 106 has a voltage detection terminal 115 and a detection result output terminal 116.

[0012] The connections of the current detection circuit 1 will be described. The input terminal 101 is connected to the cathode terminal of the rectifier element 102, the gate of the NMOS transistor 105, and the first end 113 of the load element 104. The first node 110 is connected to the anode terminal of the rectifier element 102, the drain of the first NMOS transistor 105, the voltage detection terminal 115, and the current output terminal 112. The detection result output terminal 116 is connected to the output terminal 107. The power supply terminal 111 is connected to the positive power supply terminal VDD. The second end 114 of the load element 104 is connected to the negative power supply terminal VSS. The source of the NMOS transistor 105 is connected to the negative power supply terminal VSS.

[0013] The current control circuit 103 will be described with reference to FIG.

[0014] The current control circuit 103 has a constant current element 201 and P-channel MOS transistors (hereinafter referred to as "PMOS transistors") 202 and 203 in addition to a power supply terminal 111 and a current output terminal 112. The power supply terminal 111 is connected to the source of the PMOS transistor 202 and the source of the PMOS transistor 203. The gate of the PMOS transistor 202 is connected to the drain of the PMOS transistor 202 and the gate of the PMOS transistor 203. The gate and drain of the PMOS transistor 202 and the gate of the PMOS transistor 203 are further connected to a negative power supply terminal VSS via the constant current element 201. The drain of the PMOS transistor 203 is connected to the current output terminal 112.

[0015] In the current control circuit 103 , with the above-mentioned configuration, the constant current flowing through the constant current element 201 is mirrored to the drain current of the PMOS transistor 203 via the PMOS transistor 202 and is output from the current output terminal 112 .

[0016] The load element 104 will be described with reference to FIG.

[0017] The load element 104 has a so-called diode-connected NMOS transistor 301 having the same threshold voltage as the NMOS transistor 105 (FIG. 1) in addition to a first end 113 and a second end 114. More specifically, the first end 113 is connected to the drain and gate of the NMOS transistor 301. The second end 114 is connected to the source of the NMOS transistor 301.

[0018] The voltage detection circuit 106 will be described with reference to FIG.

[0019] The voltage detection circuit 106 has a constant current element 401 and an NMOS transistor 402 having the same threshold voltage as the NMOS transistor 105 (FIG. 1) in addition to a voltage detection terminal 115 and a detection result output terminal 116. The voltage detection terminal 115 is connected to the gate of the NMOS transistor 402. The drain of the NMOS transistor 402 is connected to a first terminal of the constant current element 401 and the detection result output terminal 116. The second terminal of the constant current element 401 is connected to the positive power supply terminal VDD. The source of the NMOS transistor 402 is connected to the negative power supply terminal VSS.

[0020] With the above-described configuration, the voltage detection circuit 106 switches the voltage level of the detection signal output from the detection result output terminal 116 depending on whether the voltage of the voltage detection terminal 115 is lower than the threshold voltage of the NMOS transistor 402. In the illustrated voltage detection circuit 106, when the voltage of the voltage detection terminal 115 is lower than the threshold voltage of the NMOS transistor 402, a detection signal having the voltage level of the positive power supply terminal VDD is output from the detection result output terminal 116.

[0021] Next, a description will be given of the operation of the current detection circuit 1. First, a description will be given of the case where the input current Iin input to the input terminal 101 of the current detection circuit 1 does not contain a signal component, that is, where the current value does not change.

[0022] The current control circuit 103 supplies a constant current to the first node 110. A part of the constant current supplied from the first current control circuit 103 to the first node 110 flows to the negative power supply terminal VSS via the rectifier element 102 and the load element 104, and the remaining current flows to the negative power supply terminal VSS via the NMOS transistor 105. The voltage generated in the load element 104 is input to the gate of the NMOS transistor 105. The NMOS transistor 105 controls the drain current so that the sum of the current flowing to the negative power supply terminal VSS via the rectifier element 102 and the load element 104 and the current flowing to the drain is equal to the constant current from the current control circuit 103. Since the sum of the drain current of the NMOS transistor 105 and the current flowing to the negative power supply terminal VSS via the rectifier element 102 and the load element 104 is controlled to be equal to the constant current from the current control circuit 103, the voltage of the first node 110 becomes the threshold voltage of the NMOS transistor 105 plus the forward voltage of the rectifier element 102.

[0023] The voltage detection circuit 106 receives the voltage of the first node 110 at a voltage detection terminal 115. Since the voltage of the voltage detection terminal 115, i.e., the voltage supplied to the gate of the NMOS transistor 402 (FIG. 4), exceeds the threshold voltage of the NMOS transistor 402, a signal of the voltage level of the negative power supply terminal VSS is output from the detection result output terminal 116. The signal of the voltage level of the negative power supply terminal VSS output from the detection result output terminal 116 is transmitted to the output terminal 107 and output from the output terminal 107. The detection signal of the voltage level of the negative power supply terminal VSS corresponds to a state in which the input current Iin input to the input terminal 101 does not include a signal component.

[0024] Next, we will explain what happens when the input current Iin input to the input terminal 101 of the current detection circuit 1 transitions from a state not containing a signal component to a state containing a signal component, i.e., from a state in which the current value does not change to a state in which the current value changes.

[0025] When an input current Iin is input to the input terminal 101, the voltage generated in the load element 104 increases. When the voltage generated in the load element 104 increases, the voltage at the gate of the NMOS transistor 105 increases, and the current value of the drain current of the NMOS transistor 105 increases. When the current value of the drain current of the NMOS transistor 105 increases, it exceeds the constant current value from the current control circuit 103, and the voltage of the first node 110 becomes the voltage level of the negative power supply terminal VSS.

[0026] When the voltage of the first node 110 becomes equal to the voltage level of the negative power supply terminal VSS, the voltage of the voltage detection terminal 115 of the voltage detection circuit 106 falls below the threshold voltage of the NMOS transistor 402 (FIG. 4), and the voltage detection circuit 106 outputs a detection signal of the voltage level of the positive power supply terminal VDD from the detection result output terminal 116. The detection signal of the voltage level of the positive power supply terminal VDD output from the detection result output terminal 116 is transmitted to the output terminal 107 and output from the output terminal 107. The detection signal of the voltage level of the positive power supply terminal VDD corresponds to a state in which the input current Iin input to the input terminal 101 contains a signal component.

[0027] According to this embodiment, the current detection circuit 1 includes an NMOS transistor 105 connected to a negative power supply terminal VSS and a drain and gate connected to each other via a rectifier element 102, and a first end 113 of the load element 104 is connected to a cathode as one end of the rectifier element 102. A voltage generated when a constant current supplied to the drain of the NMOS transistor 105 is supplied to the load element 104 and flows is applied to the gate of the NMOS transistor 105. Therefore, the current detection circuit 1 can detect a change in the input current flowing from the input terminal 101 to the load element 104 by a voltage change at the drain of the NMOS transistor 105. Therefore, the current detection circuit 1 can detect a current change caused by a signal component that is very small compared to the DC component contained in the input current Iin input to the input terminal 101. Second embodiment Fig. 5 is a circuit diagram of a current detection circuit 2 which is an example of a current detection circuit according to a second embodiment of the present invention. Figs. 6 to 8 are circuit diagrams showing examples of a current control circuit 502, a load element 501, and a voltage detection circuit 504 of the current detection circuit 2, respectively. The current detection circuit according to the second embodiment will be described with reference to Figs. 5 to 8.

[0028] The current detection circuit 2 differs from the current detection circuit 1 in that the polarities of the power supply and the transistors are swapped, but there are no other substantial differences. Therefore, the components that are substantially the same as those in the current detection circuit 1 are given the same reference numerals and their description is omitted.

[0029] The overall configuration of the current detection circuit 2 will be described with reference to FIG.

[0030] The current detection circuit 2 includes an input terminal 101, a rectifying element 102, a load element 501, a current control circuit 502, a PMOS transistor 503 which is an example of a field effect transistor, a voltage detection circuit 504, and an output terminal 107. The load element 501 has a first terminal 511 and a second terminal 512. The current control circuit 502 has a current sink terminal 513 and a power supply terminal 514. The voltage detection circuit 504 has a voltage detection terminal 515 and a detection result output terminal 516.

[0031] The connections of the current detection circuit 2 will be described. The input terminal 101 is connected to the cathode terminal of the rectifier element 102, the drain of the PMOS transistor 503, the current draw terminal 513 of the current control circuit 502, and the voltage detection terminal 515 of the voltage detection circuit 504. The detection result output terminal 516 of the voltage detection circuit 504 is connected to the output terminal 107. The anode terminal of the rectifier element 102 is connected to the gate of the PMOS transistor 503 and the second terminal 512 of the load element 501. The first terminal 511 of the load element 501 and the source of the PMOS transistor 503 are connected to the positive power supply terminal VDD. The power supply terminal 514 of the current control circuit 502 is connected to the negative power supply terminal VSS.

[0032] The current control circuit 502 will be described with reference to FIG.

[0033] The current control circuit 502 has a constant current element 201 and NMOS transistors 601 and 602 in addition to a current sink terminal 513 and a power supply terminal 514. A first terminal of the constant current element 201 is connected to the positive power supply terminal VDD. A second terminal of the constant current element 201 is connected to the drain and gate of the NMOS transistor 601 and the gate of the NMOS transistor 602. A drain of the NMOS transistor 602 is connected to the current sink terminal 513. A source of the NMOS transistor 602 is connected to the power supply terminal 514. A source of the NMOS transistor 601 is connected to the negative power supply terminal VSS.

[0034] In the current control circuit 502 , with the above-mentioned configuration, the constant current flowing through the constant current element 201 is mirrored to the drain current of the NMOS transistor 602 via the NMOS transistors 601 and 602 , and is drawn from the current draw terminal 513 .

[0035] The load element 501 will be described with reference to FIG.

[0036] The load element 501 has a so-called diode-connected PMOS transistor 701 having the same threshold voltage as a PMOS transistor (FIG. 5) in addition to a first end 511 and a second end 512. More specifically, the first end 511 is connected to the source of the PMOS transistor 701. The second end 512 is connected to the drain and gate of the PMOS transistor 701.

[0037] The voltage detection circuit 504 will be described with reference to FIG.

[0038] The voltage detection circuit 504 has a constant current element 401 and a PMOS transistor 801 having the same threshold voltage as the PMOS transistor 503 (FIG. 5) in addition to a voltage detection terminal 515 and a detection result output terminal 516. The voltage detection terminal 515 is connected to the gate of the PMOS transistor 801. The drain of the PMOS transistor 801 is connected to a first terminal of the constant current element 401 and the detection result output terminal 516. The second terminal of the constant current element 401 is connected to the negative power supply terminal VSS. The source of the PMOS transistor 801 is connected to the positive power supply terminal VDD.

[0039] In the voltage detection circuit 504, the voltage level of the detection signal output from the detection result output terminal 516 is switched depending on whether the voltage of the voltage detection terminal 515 is higher than the threshold voltage of the PMOS transistor 801. When the voltage of the voltage detection terminal 515 exceeds the threshold voltage of the PMOS transistor 801, a detection signal having the voltage level of the negative power supply terminal VSS is output from the detection result output terminal 516.

[0040] The current detection circuit 2 configured as described above operates in the same manner as the current detection circuit 1.

[0041] According to this embodiment, the current detection circuit 2 includes a PMOS transistor 503, the drain and gate of which are connected to each other via the rectifier element 102, and which is connected to the positive power supply terminal VDD, and the second end 512 of the load element 501 is connected to the anode, which is one end of the rectifier element 102. A voltage generated when a constant current supplied to the drain of the PMOS transistor 503 is supplied to the load element 501 and flows is applied to the gate of the PMOS transistor 503. Therefore, the current detection circuit 2 can detect a change in the input current flowing from the input terminal 101 to the load element 501 by a voltage change at the drain of the PMOS transistor 503. Therefore, the current detection circuit 2 can detect a current change caused by a very small signal component compared to the DC component contained in the input current Iin input to the input terminal 101.

[0042] The present invention is not limited to the above-mentioned embodiment, and can be implemented in various forms other than the above-mentioned embodiment at the implementation stage, and various omissions, additions, substitutions, or modifications can be made without departing from the gist of the invention. For example, in the above-mentioned embodiment, the current control circuits 103 (see FIG. 2) and 502 (see FIG. 6), the load elements 104 (see FIG. 3) and 501 (see FIG. 7), and the voltage detection circuits 106 (see FIG. 4) and 504 (see FIG. 8) are not limited to the illustrated configurations.

[0043] Current control circuit 103 may have any circuit configuration as long as it is a circuit capable of controlling the current supplied from current output terminal 112. The illustrated current control circuit 103 is an example in which a configuration is applied in which the voltage of current output terminal 112 can operate even when the voltage is close to the voltage of power supply terminal 111 and the parasitic capacitance of current output terminal 112 is small, but current control circuit 103 may be, for example, a circuit consisting of only a resistive element. Current control circuit 502 is similar to current control circuit 103, and may have any circuit configuration as long as it is a circuit capable of controlling the current supplied from current sink terminal 513.

[0044] The load elements 104 and 501 may be any elements that generate a voltage in response to a flowing current. The illustrated load element 104 is an NMOS transistor 301 (see FIG. 3), which is suitable for generating a voltage even when a small current flows through it, but the load element 104 can be a resistor, a diode, or a combination of these, etc., as appropriate. The illustrated load element 501 is a PMOS transistor 701 (see FIG. 7), which is suitable for generating a voltage even when a small current flows through it, but the load element 501 can be a resistor, a diode, or a combination of these, etc., as appropriate.

[0045] The current detection circuit 1 can be configured to detect even minute currents such as the photocurrent of a photodiode or the current received by radio waves, and there are no restrictions on the current to be detected. If the supply voltage of the current to be detected is low, the current to be detected can be input to the voltage detection terminal 115 via a capacitor, thereby making it possible to detect such a current with a low supply voltage. As with the current detection circuit 1, there are no restrictions on the current to be detected with the current detection circuit 2.

[0046] The MOS transistor in the above-described embodiment is not limited to a MOSFET. In addition to a MOSFET, other field effect transistors such as a junction field effect transistor (JFET) or a metal-insulator-semiconductor field effect transistor (MISFET) may also be used.

[0047] These embodiments and their variations are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0048] 1,2 Current detection circuit 101 Input terminal 102 Rectifier 103,502 Current control circuit 104,501 Load element 105 NMOS transistor 503 PMOS Transistor 106,504 Voltage detection circuit 107 Output terminal 111,514 Power terminal 112 Current output terminal 513 Current Intake Terminal 115,515 Voltage detection terminal 116,516 Detection result output terminal

Claims

1. An input terminal; An output terminal; A rectifying element; A current control circuit; A load element; a first transistor which is a field effect transistor of a first conductivity type; a voltage detection circuit having a voltage detection terminal and a detection result output terminal; The current control circuit includes: a first terminal connected to a first power supply terminal; a second terminal connected to an anode terminal of the rectifying element, a drain of the first transistor, and a voltage detection terminal of the voltage detection circuit; a gate of the first transistor is connected to the input terminal, a cathode terminal of the rectifier element, and a second power supply terminal via the load element; A current detection circuit, wherein the output terminal is connected to a detection result output terminal of the voltage detection circuit.

2. The current control circuit includes: second and third transistors, which are field effect transistors of a second conductivity type; A first constant current element, The first constant current element is a first end connected to the gate and drain of the second transistor and the gate of the third transistor; a second end connected to the second power terminal; a source of each of the second and third transistors is connected to the first terminal; The drain of the third transistor is connected to the second terminal.

2. The current sensing circuit of claim 1.

3. The load element is a fourth transistor being a field effect transistor of a first conductivity type; a first end connected to the gate and drain of the fourth transistor; a second end connected to the source of the fourth transistor; 2. The current sensing circuit of claim 1.

4. The voltage detection circuit includes: a fifth transistor, the fifth transistor being a field effect transistor of the first conductivity type; A second constant current element, a first end of the second constant current element is connected to the first power supply terminal; a source of the fifth transistor is connected to the second power supply terminal; a gate of the fifth transistor is connected to the voltage detection terminal; The drain of the fifth transistor is connected to the second terminal of the second constant current element and the detection result output terminal.

2. The current sensing circuit of claim 1.

5. An input terminal; An output terminal; A rectifying element; A current control circuit; A load element; a first transistor which is a field effect transistor of a first conductivity type; a voltage detection circuit having a voltage detection terminal and a detection result output terminal; The current control circuit includes: a first terminal connected to a first power supply terminal; a second terminal connected to the input terminal, the cathode terminal of the rectifying element, the drain of the first transistor, and a voltage detection terminal of the voltage detection circuit; a gate of the first transistor is connected to an anode terminal of the rectifier element and to a second power supply terminal via the load element; A current detection circuit, wherein the output terminal is connected to a detection result output terminal of the voltage detection circuit.

6. The current control circuit includes: second and third transistors, which are field effect transistors of a second conductivity type; A first constant current element, The first constant current element is a first end connected to the gate and drain of the second transistor and the gate of the third transistor; a second end connected to the second power terminal; a source of the second transistor is connected to the first power supply terminal; a source of the third transistor is connected to the first terminal; The drain of the third transistor is connected to the second terminal.

6. The current detection circuit according to claim 5.

7. The load element is a fourth transistor being a field effect transistor of a first conductivity type; a first terminal connected to the source of the fourth transistor; a second end connected to the gate and drain of the fourth transistor; 6. The current detection circuit according to claim 5.

8. The voltage detection circuit includes: a fifth transistor, the fifth transistor being a field effect transistor of the first conductivity type; A second constant current element, a first end of the second constant current element is connected to the first power supply terminal; a source of the fifth transistor is connected to the second power supply terminal; a gate of the fifth transistor is connected to the voltage detection terminal; The drain of the fifth transistor is connected to the second terminal of the second constant current element and the detection result output terminal.

6. The current detection circuit according to claim 5.

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