JP2009180693A - Detection system of disconnection between current sensor and electronic control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect disconnection between a current sensor and an electronic control unit that supplies power to the current sensor, while the current to be measured flows. <P>SOLUTION: An N channel junction type FET (Field-Effect Transistor) 133 is disposed between a power supply input terminal 111 and a sensor output terminal 113, and a gate of the N channel junction type FET 133 is connected to the node between of a bias resistor R<SB>5</SB>and a second ground terminal 112. The anode of a positive-side diode D<SB>1</SB>is connected to a power supply input terminal 111, and the cathode thereof is connected to a positive-side power source terminal of an operational amplifier 118. A first constant current circuit 131 is disposed between the cathode of the positive-side diode D<SB>1</SB>and the second ground terminal 112. The anode of a negative-side diode D<SB>2</SB>is connected to a negative-side power source terminal of the operational amplifier 118, and the cathode thereof is connected to the second ground terminal 112. A second constant current circuit 132 is disposed between the power supply input terminal 111 and the anode of the negative-side diode D<SB>2</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a disconnection detection system between a current sensor that outputs a detection voltage corresponding to a current to be measured and an electronic control unit that supplies power to the current sensor.

  2. Description of the Related Art Conventionally, as a current sensor for detecting a current to be measured flowing through a conductive wire in a non-contact state, a magnetic proportional type or a magnetic balanced type is known.

As shown in FIG. 10A, the magnetic proportional current sensor is arranged in the gap G with a ring-shaped magnetic core 20 having a gap G (such as a silicon steel plate or a permalloy core having a high magnetic permeability and little residual magnetism). Hall element 116 (an example of a magnetic detection element). The magnetic core 20 is an arrangement in which the bus bar 10 of the flow of the current I _in the measurement through. Therefore, a magnetic field is generated in the gap G by the current I _{in to} be measured, and this is applied to the magnetic sensitive surface of the Hall element 116. Since the intensity of the magnetic field is proportional to the measured current I _in, the measured current I _in is determined from the output voltage of the Hall element 116.

In addition to the configuration of the magnetic proportional current sensor, the magnetic balanced current sensor has a negative feedback coil L _{FB in} which a winding is provided on the magnetic core 20 as illustrated in FIG. 10B. Then, a magnetic field (hereinafter also referred to as “first magnetic field”) is generated in the gap G by the measured current I _in , and this is applied to the magnetosensitive surface of the Hall element 116 to cancel the applied first magnetic field. A current is supplied to the negative feedback coil L _FB so as to generate a magnetic field (hereinafter also referred to as “second magnetic field”). The current to be measured I _in is obtained from the current supplied to the negative feedback coil L _FB to generate the second magnetic field.

  The current sensor as described above is, for example, measurement of driving current of an electric motor used in a machine tool or a brushless motor of an electric power steering device used in a general vehicle, or a battery charging / discharging current of a hybrid car or an electric vehicle. Used for measurement.

  By the way, the current sensor generally operates with power supplied from an electronic control unit (ECU). If a disconnection occurs in the path connecting the current sensor and the electronic control unit, the detection voltage output from the current sensor does not correspond to the current to be measured, and normal current detection cannot be performed. When the current sensor is used in, for example, an in-vehicle battery current monitoring system, if normal current detection cannot be performed by the current sensor, the battery may be overcharged or overdischarged to shorten the battery life. Furthermore, there is a possibility of falling into a dangerous state such as a battery flame. For this reason, it is required to detect a disconnection in the connection path between the current sensor and the electronic control unit.

A device described in Patent Document 1 below is known as a device for determining a failure of a current sensor.
JP 2006-145426 A (particularly FIG. 1)

  The device of Patent Document 1 is configured to pass a test current through a coil when a current to be measured is stopped, and to determine a failure of the current sensor based on a current value detected by a Hall element at this time.

  When the disconnection between the current sensor and the electronic control unit is to be detected using the apparatus of Patent Document 1, it is necessary to flow an inspection current to the coil when the current to be measured is stopped as described above. There is a problem that the disconnection cannot be detected during operation or operation of the machine tool.

  The present invention has been made in view of such a situation, and its purpose is to detect a disconnection between a current sensor and an electronic control unit that supplies power to the current sensor when a current to be measured flows. It is an object of the present invention to provide a disconnection detection system between a current sensor and an electronic control unit.

A first aspect of the present invention is a disconnection detection system between a current sensor and an electronic control unit. This disconnection detection system
A current sensor, and an electronic control unit that supplies power to the current sensor,
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and a current to be measured. A current detection unit that outputs a detection voltage according to the output, an output amplifier that amplifies the detection voltage and outputs the detection voltage to the sensor output terminal, and an N channel provided between the power input terminal and the sensor output terminal A junction-type FET, and a bias resistor provided between the power input terminal and the second ground terminal, and a connection point between the bias resistor and the second ground terminal of the N-channel junction FET. A power supply side step-down means for connecting a gate and making the voltage supplied to the positive power supply terminal of the output amplifier smaller than the voltage of the power supply input terminal comprises the power supply input terminal and the positive power supply terminal. It is provided between.

  In the disconnection detection system according to the first aspect, it is preferable that a voltage drop caused by the N-channel junction FET when the N-channel junction FET is turned on is smaller than a voltage drop caused by the power supply side step-down means.

  In the disconnection detection system according to the first aspect, when the disconnection detection unit detects a disconnection abnormality when a voltage larger than the voltage supplied to the positive power supply terminal of the output amplifier is input to the disconnection detection unit. Good.

  In this case, a voltage larger than the maximum voltage in the voltage range corresponding to the rated range of the current to be measured and smaller than the voltage supplied to the positive power supply terminal of the output amplifier is input to the disconnection detector. When this is done, the disconnection detection unit may detect an overcurrent abnormality.

In the disconnection detection system according to the first aspect,
The power supply side step-down means includes a positive side diode having an anode connected to the power supply input terminal and a cathode connected to the positive power supply terminal of the output amplifier,
A positive-side constant current circuit or a positive-side resistor may be provided between the cathode of the positive-side diode and the second ground terminal.

  In the disconnection detection system according to the first aspect, the amount of current flowing through the positive-side constant current circuit or the resistance value of the positive-side resistor may be variably adjustable.

  In the disconnection detection system according to the first aspect, the current sensor further includes a ground side step-down means for making the voltage supplied to the negative power supply terminal of the output amplifier larger than the voltage of the second ground terminal. It may be provided between the second ground terminal and the negative power supply terminal.

The second aspect of the present invention is also a disconnection detection system between the current sensor and the electronic control unit. This disconnection detection system
A current sensor, and an electronic control unit that supplies power to the current sensor,
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and a current to be measured. A current detection unit that outputs a detection voltage corresponding to the output voltage, an output amplifier that amplifies the detection voltage and outputs the detection voltage to the sensor output terminal, and a P provided between the sensor output terminal and the second ground terminal. A channel junction FET, and a bias resistor provided between the power input terminal and the second ground terminal, and a connection point between the power input terminal and the bias resistor is connected to the P channel junction FET. A ground side step-down means for connecting a gate and making the voltage supplied to the negative power supply terminal of the output amplifier larger than the voltage of the second ground terminal includes the negative power supply terminal and the second ground terminal. It is provided between.

  In the disconnection detection system according to the second aspect, it is preferable that a voltage drop caused by the P-channel junction FET when the P-channel junction FET is turned on is smaller than a voltage drop caused by the ground side step-down means.

  In the disconnection detection system of the second aspect, when the disconnection detection unit detects a disconnection abnormality when a voltage smaller than the voltage supplied to the negative power supply terminal of the output amplifier is input to the disconnection detection unit. Good.

In the disconnection detection system according to the second aspect,
The ground-side step-down means includes a negative diode having an anode connected to the negative power supply terminal of the output amplifier and a cathode connected to the second ground terminal;
A negative constant current circuit or a negative resistance may be provided between the power input terminal and the anode of the negative diode.

The third aspect of the present invention is also a disconnection detection system between the current sensor and the electronic control unit. This disconnection detection system
A current sensor that outputs a voltage corresponding to the current to be measured, and an electronic control unit that supplies power to the current sensor;
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and the sensor output. A P-channel junction FET provided between the terminal and the second ground terminal, and a bias resistor provided between the power input terminal and the second ground terminal, and the power input terminal A gate of the P-channel junction FET is connected to a connection point with the bias resistor.

  It should be noted that any combination of the above-described constituent elements and a representation obtained by converting the expression of the present invention between methods and apparatuses are also effective as an aspect of the present invention.

  According to the first aspect of the present invention, when the first ground terminal and the second ground terminal are disconnected, the N-channel junction FET is turned on, and the voltage at the detection voltage input terminal is set regardless of the current to be measured. Very close to the voltage at the power supply terminal. For this reason, the disconnection detection unit connected to the detection voltage input terminal can detect disconnection abnormality when the current to be measured flows.

  According to the second and third aspects of the present invention, when the power supply terminal and the power supply input terminal are disconnected, the P-channel junction FET is turned on, and the voltage of the detection voltage input terminal regardless of the current to be measured. Becomes very close to the voltage of the first ground terminal. For this reason, the disconnection detection unit connected to the detection voltage input terminal can detect disconnection abnormality when the current to be measured flows.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

(First embodiment)
FIG. 1 is an exemplary configuration diagram of a disconnection detection system 100 according to the first embodiment of the present invention. The disconnection detection system 100 includes a current sensor 110 and an electronic control unit 120. In this embodiment, the current sensor 110 is of the magnetic balance type illustrated in FIG. The electronic control unit 120 supplies power to the current sensor 110.

The electronic control unit 120 includes a power supply terminal 121, a first ground terminal 122, a detection voltage input terminal 123, a constant voltage source 125, a disconnection detection unit 126, and a pull-down resistor _{R 6.} A high potential side of the constant voltage source 125 is a power supply terminal 121, and a low potential side is a first ground terminal 122. Between the detection voltage input terminal 123 and the first ground terminal 122, a disconnection detecting section 126 and the pull-down resistor R ₆ is connected in parallel.

The current sensor 110 includes a power input terminal 111, a second ground terminal 112, a sensor output terminal 113, a current detection unit 114, an output differential amplifier 115, a reference voltage source 119, and an N-channel junction FET 133 ( FET: Field-Effect Transistor), bias resistor R ₅ , positive side diode D _{1 as} an example of the power source side step-down means, first constant current circuit 131 as a positive side constant current circuit, and ground side step-down means having a negative-side diode D ₂ is an illustration, and a second constant-current source 132 as the negative side constant current circuit. The current detection unit 114 includes a Hall element 116 that is an example of a magnetic detection element, a negative feedback differential amplifier 117, a negative feedback coil _LFB, and a detection resistor R _S that is an example of a current-voltage converter. . The output differential amplifier 115 includes an operational amplifier 118 and resistors R _{1 to} R ₄ .

The power input terminal 111 is connected to the power supply terminal 121, the second ground terminal 112 is connected to the first ground terminal 122, and the sensor output terminal 113 is connected to the detection voltage input terminal 123. The current detection unit 114 outputs a detection voltage V _S corresponding to the measured current I _in (see FIG. 10B). The output differential amplifier 115 amplifies the detection voltage V _S and outputs it to the sensor output terminal (denoted as V _{O in the} figure). An N-channel junction FET 133 is provided between the power input terminal 111 and the sensor output terminal 113, and a bias resistor R ₅ is provided between the power input terminal 111 and the second ground terminal 112. The gate of the N-channel junction FET 133 is connected to the connection point between the bias resistor R ₅ and the second ground terminal 112. As illustrated in FIG. 2, N-channel junction type FET is, when V _GS is 0 turned, V _GS is turned off when sufficiently smaller than _{0 (V GS ≦ V P)} . Here, the voltage drop V _DS by N-channel junction form FET133 when N-channel Junction Type FET133 is turned on is assumed to be smaller than the forward voltage drop V _F1 of the positive side diodes _{D 1.} Such a design is realized, for example, by setting the pull-down resistor R ₆ in FIG. 1 to a resistance value sufficiently larger than the ON resistance of the N-channel junction FET 133.

The positive diode D ₁ has an anode connected to the power input terminal 111 and a cathode connected to the positive power terminal of the operational amplifier 118 (that is, the positive power terminal of the output differential amplifier 115). The first constant current circuit 131 is provided between the cathode of the positive diode D ₁ and the second ground terminal 112. Preferably, the amount of current flowing through the first constant current circuit 131 is variably adjustable. The forward voltage drop V _F1 of the positive-side diodes D _1, the voltage supplied to the positive power supply terminal of the operational amplifier 118 is smaller than the voltage of the power supply input terminal 111 (that is, the voltage V _CC of the constant voltage source 125).

The negative diode D ₂ has an anode connected to the negative power supply terminal of the operational amplifier 118 (that is, the negative power supply terminal of the output differential amplifier 115) and a cathode connected to the second ground terminal 112. The second constant current circuit 132 is provided between the anode power supply terminal 111 and the negative-side diode D _2. Preferably, the amount of current flowing through the second constant current circuit 132 is variably adjustable. The forward voltage drop V _F2 of the negative-side diode D _2, the voltage supplied to the negative power supply terminal of the operational amplifier 118 is greater than the voltage of the second ground terminal 112 (i.e., ground potential).

The positive diode D ₁ and the negative-side diode D _2, for example a Schottky barrier diode is used. It illustrates the forward current versus forward voltage characteristics of the Schottky barrier diode (V _F -I _F characteristics) in FIG. Forward current I _F is the forward voltage V _F Increasing becomes large, the forward voltage V _F at low temperature if the same forward current I _F is large, the forward voltage V _F at high temperatures is small. In this example, if the forward current I _F and 0.01 A, the forward voltage V _F in a temperature range from -30 ° C. to 80 ° C. the 0.45V～0.2V. In this embodiment drives the positive side diodes D ₁ and the negative-side diode D ₂ in an illustrative manner this range.

FIG. 4 is a circuit diagram showing a specific configuration example of the first constant current circuit 131 and the second constant current circuit 132 shown in FIG. The first constant current circuit 131 includes a first Zener diode D _Z1 , a resistor R _Z1 , a first transistor Q _D1 (PNP type), and a first resistor R ₁₁ . The resistor R _Z1 limits the current flowing through the first Zener diode D _Z1 . Since the voltage across the first Zener diode D _Z1 is constant and the base-emitter voltage of the first transistor Q _D1 is also constant (about 0.6 V in the case of a silicon transistor), the power supply voltage V _CC varies. first voltage across the resistor R ₁₁ ends also a constant current flows is constant. If the resistance value of the first resistor R ₁₁ is variably adjustable, the amount of current flowing through the first constant current circuit 131 can be variably adjusted. The second constant current circuit 132 includes a second Zener diode D _Z2 , a resistor R _Z2 , a second transistor Q _D2 (NPN type), and a second resistor R ₂₂ . The same can be said for the second constant current circuit 132 as for the first constant current circuit 131. Since the current flowing through the operational amplifier 118 is negligibly small compared to the current flowing through the first constant current circuit 131 and the second constant current circuit 132, the current flowing through the positive-side diodes D ₁ and the negative-side diode D ₂ is The currents flowing through the first constant current circuit 131 and the second constant current circuit 132 substantially coincide with each other. Returning to FIG.

In the current detection unit 114, the Hall element 116 is equivalently represented by a bridge connection of four resistors, and a constant Hall element drive current is allowed to flow between the terminals a and b so that the Hall element is connected between the output terminals c and d. A voltage proportional to the magnetic field applied to 116 (in other words, proportional to the measured current I _in ) is obtained. The output terminals c and d of the Hall element 116 are connected to the input terminal of the negative feedback differential amplifier 117, respectively. A negative feedback coil L _FB and a detection resistor R _S are connected to a path connecting the output terminal of the negative feedback differential amplifier 117 and the output terminal of the reference voltage source 119 (outputs a reference voltage V _ref of about 2.5 V). Connected in series. Both ends of the detection resistor _RS are connected to the input terminal of the output differential amplifier 115, and the output terminal of the output differential amplifier 115 is connected to the sensor output terminal 113. The detection resistor R _S is a very small resistor for converting the current supplied to the negative feedback coil L _FB into a voltage, and its resistance value is sufficiently smaller than the input impedance of the output differential amplifier 115.

The output voltage of the Hall element 116 is input to the negative feedback differential amplifier 117. The negative feedback differential amplifier 117 sucks or discharges current from the output terminal so that the potential difference between the terminals c and d is always zero, that is, the first magnetic field described above on the magnetic sensitive surface of the Hall element 116. The negative feedback current I _FB is supplied to the negative feedback coil L _FB so that the second magnetic field and the second magnetic field cancel each other (in the figure, the direction of I _FB is when the measured current I _in is positive). Here, for example, if the number of turns of the negative feedback coil L _FB is 4,000 turns and the measured current I _in is 200 A, the negative feedback current I _FB = 200 / 4,000 = It becomes 0.05A. Negative feedback current I _FB is converted to a detected voltage V _S by the detection resistor R _S, the detected voltage V _S is output after being amplified by the output differential amplifier 115 from the sensor output terminal 16. The detection voltage V _S is −I _FB × R _S. For example, if the detection resistance R _S is 4Ω, the detection voltage V _S is −0.05 A × 4Ω = −0.2V.

The resistors R _{1 to} R ₄ of the output differential amplifier 115 have resistance values R ₁ = R ₂ and R ₃ = R ₄ , and the amplification degree of the output differential amplifier 115 is R ₃ / R ₁ (= R ₄ / R ₂ ). The amplification degree is about 10, for example. The output voltage V _O of the output differential amplifier 115 (that is, the output voltage of the current sensor 110) is V _O = − (R ₃ / R ₁ ) V _S + V _ref [V] (Equation 1) where V _ref is about 2 .5V
When expressed using the measured current I _in , the output voltage V _O is V _O = − (R ₃ / R ₁ ) × (−I _in / 4000) × R _S + V _ref [V]
= −10 × (−I _in /4000)×4Ω+2.5V [V]
= I _in /100+2.5V[V] (Equation 2)
It becomes.

FIG. 5 is an exemplary output characteristic diagram showing a relationship between the output voltage V _O of the output differential amplifier 115 of FIG. 1 (that is, the output voltage of the current sensor 110) and the measured current I _in . Hereinafter, the description will be divided into five cases.

Case 1: the output voltage _{V O} varies linearly in the range of 0.5V~4.5V relative range -200A~ + 200A (rated current) of the normal operation current to be measured I _in. At this time, the V _GS of the N-channel junction FET 133 is sufficiently smaller than 0 due to the voltage drop in the bias resistor R _5, so the N-channel junction FET 133 is off.

・ Case 2: Overcurrent Due to the rail-to-rail characteristics of recent op amps, the output voltage swings to almost full power supply voltage, that is, in a range close to 0V to 5V (eg 0.05V to 4.95V). To do. For this reason, the output voltage V _O becomes larger than 4.5 V in the range where the measured current I _in exceeds 200 A. However, 0.2V than the voltage of the positive-side power source terminal voltage supplied to the power input terminal 111 of the forward voltage drop V _F1 operational amplifier 118 of the above as the positive side diode D ₁ in the present embodiment (+ 5V) Since it becomes about 0.45 V smaller, the upper limit of the output voltage V _O is 4.55 V to 4.8 V. Similarly, in the range where the measured current I _in is less than −200 A, the output voltage V _O is less than 0.5 V. However, in this embodiment, the operational amplifier is operated by the forward voltage drop V _F2 of the negative diode D ₂ as described above. Since the voltage supplied to the negative power supply terminal 118 is about 0.2 V to 0.45 V higher than the voltage of the second ground terminal 112 (that is, the ground potential), the lower limit of the output voltage V _O is 0.2 V. ~ 0.45V. At this time, like the case 1, the N-channel junction FET 133 is off.

Case 3: When the ground terminal is disconnected When the first ground terminal 122 and the second ground terminal 112 are disconnected (corresponding to the case where SW1 is turned off), the current sensor 110 becomes inactive. Also, no current flows through the bias resistor R ₅ , so that V _GS of the N-channel junction FET 133 becomes 0, and the N-channel junction FET 133 is turned on. Therefore, the output voltage V _O is very close to the voltage (5 V) of the constant voltage source 125 regardless of the current I _in to be measured. However, since there is a voltage drop due to the ON resistance of the N-channel junction FET 133, the output voltage V _O does not exactly match the voltage (5V) of the constant voltage source 125, and is about 4.9V, for example.

Case 4: (corresponds to a case where the SW3 is turned off) between the disconnection power supply terminal 121 and the power input terminal 111 between the power supply terminals when disconnected, the current current sensor 110 becomes inactive pull-down resistor R ₆ Does not flow. Therefore, the output voltage V _O becomes the ground potential (0 V).

Case 5: When the sensor output terminal is disconnected If the detection voltage input terminal 123 and the sensor output terminal 113 are disconnected (corresponding to the case where SW2 is turned off), the output voltage _VO is not transmitted to the electronic control unit 120 side. At this time, the detection voltage input terminal 123 is at the ground potential (0 V).

  The voltage input to the disconnection detection unit 126 matches the voltage of the sensor output terminal 113 in the above cases 1 to 4, and becomes the ground potential (0 V) in the case 5 regardless of the voltage of the sensor output terminal 113. Hereinafter, the function of the disconnection detection unit 126 will be described.

Function 1: Disconnection Detection Between Ground Terminals When a voltage larger than a voltage (for example, 4.55 V to 4.8 V) supplied to the positive power supply terminal of the output differential amplifier 115 is input, the disconnection detection unit 126 Detects that the first ground terminal 122 and the second ground terminal 112 are disconnected (case 3).

Function 2: Other disconnection detection When the voltage of the detection voltage input terminal 123 becomes the ground potential (0 V), the disconnection detection unit 126 disconnects between the power supply terminal 121 and the power input terminal 111 (case 4). Alternatively, it is detected that the detection voltage input terminal 123 and the sensor output terminal 113 are disconnected (case 5).

Function 3: Positive overcurrent detection Voltage that is larger than the maximum value of the rated output voltage (for example, 4.5 V) and supplied to the positive power supply terminal of the output differential amplifier 115 (for example, 4.55 V to 4.V). When a voltage smaller than 8V) is input, the disconnection detection unit 126 detects that the measured current Iin is an overcurrent _{in the} positive direction (for example, the battery discharge direction) (Case 2).

Function 4: Negative-direction overcurrent detection Voltage that is smaller than the minimum value of the rated output voltage (for example, 0.5 V) and that is supplied to the negative power supply terminal of the output differential amplifier 115 (for example, 0.2 V to. When a voltage greater than 45V is input, the disconnection detection unit 126 detects that the measured current Iin is an overcurrent _{in the} negative direction (for example, the charging direction of the battery) (case 2).

  When an abnormality is detected, the disconnection detection unit 126 outputs a predetermined display, voice, or the like, so that the user can know the abnormality. The disconnection detection unit 126 preferably outputs the distinction so that it can be understood which of the functions 1 to 3 has worked.

  According to the present embodiment, the following effects can be achieved.

(1) When the first ground terminal 122 and the second ground terminal 112 are disconnected, the N-channel junction FET 133 is turned on, and the output voltage V _O is the voltage of the constant voltage source 125 regardless of the measured current I _in. Very close to. For this reason, it is possible to detect a disconnection abnormality when the measured current I _in is flowing. Therefore, as compared with the case where the inspection current is supplied to the coil when the current to be measured is stopped as in the apparatus of Patent Document 1, for example, disconnection can be detected during operation of the hybrid car or operation of the machine tool. There are benefits.

(2) it is smaller than the positive diode voltage supplied to the positive power supply terminal of the D ₁ of the forward voltage drop V _F1 operational amplifier 118 the voltage of the power supply input terminal 111 (the voltage of the constant voltage source 125). Therefore, even when the measured current I _in is an overcurrent _{in the} positive direction, the upper limit of the output voltage V _O is smaller than the voltage of the constant voltage source 125, and the first ground terminal 122 and the second ground terminal 112 are disconnected. Output voltage V _O (which is very close to the voltage of the constant voltage source 125). Therefore, it is possible to detect and distinguish disconnection abnormality and the overcurrent abnormality of the measured current I _in between the first ground terminal 122 and the second ground terminal 112.

(3) by a forward voltage drop V _F2 of the negative-side diode D _2, the voltage supplied to the negative power supply terminal of the operational amplifier 118 is greater than the voltage of the second ground terminal 112 (ground potential). For this reason, even when the measured current I _in is an overcurrent _{in the} negative direction, the lower limit of the output voltage V _O is larger than the ground potential, and the disconnection detector 126 disconnects between the power supply terminal 121 and the power input terminal 111. Or the output voltage V _O (corresponding to the ground potential) when the detection voltage input terminal 123 and the sensor output terminal 113 are disconnected. Therefore, it is easy to detect by distinguishing an over-current abnormality and their disconnection abnormality and the measured current I _in.

(4) When the amount of current flowing through the first constant current circuit 131 and the second constant current circuit 132 is variably adjustable, the forward voltage drop V _{F1 of the} positive diode D _{1 and} the forward voltage of the negative diode D ₂ The drop V _F2 can be determined to a desired value. Therefore, from the viewpoint of the design in which the voltage drop V _DS due to the N-channel junction FET 133 when the N-channel junction FET 133 is turned on as described above is smaller than the forward voltage drop V _F1 of the positive-side diode D ₁ , the positive-side diode Flexibility such as increasing the forward voltage drop V _F1 of D ₁ is obtained. Further, since also possible to change the forward voltage drop V _F2 of the order of the positive side diodes D ₁ direction voltage drop V _F1 and the negative-side diode D ₂ in accordance with the scope of the attached object and the rated voltage of the current sensor 110, It can be said that versatility is also high.

(Second Embodiment)
FIG. 6 is an exemplary configuration diagram of a disconnection detection system 200 according to the second embodiment of the present invention. The disconnection detection system 200 of the present embodiment is different from the disconnection detection system 100 of the first embodiment in that the first constant current circuit 131 is changed to the positive resistance R _D1 and the second constant current circuit. The difference is that 132 is changed to the negative resistance R _D2 , and the other points are the same. Again, although the more constant current circuit accuracy is not good, it is possible to supply a substantially constant current to the positive side diodes D ₁ and the negative-side diode D _2. The resistance values of the positive resistance R _D1 and the negative resistance R _D2 are preferably variably adjustable. This embodiment can also achieve the same effects as those of the first embodiment.

(Third embodiment)
FIG. 7 is an exemplary configuration diagram of a disconnection detection system 300 according to the third embodiment of the present invention. The disconnection detection system 300 of this embodiment is different from the disconnection detection system 100 of the first embodiment in that the N-channel junction FET 133 is changed to a P-channel junction FET 333 and the sensor output terminal 113 and the second ground terminal. and that provided between the 112, and that it is connected to the connection point between the power supply input terminal 111 and the bias resistor R ₅ gates of P channel junction forms FET 333, resistor R _{6 (in} the first embodiment The embodiment is different in that the pull-down resistor is connected between the power supply terminal 121 and the detection voltage input terminal 123 to form a pull-up resistor, and the other points are the same. Voltage drop due to P-channel junction form FET333 when P channel junction forms FET333 is turned V _DS is set to be smaller than the forward voltage drop V _F2 of the negative-side diode _{D 2.}

FIG. 8 is an exemplary output characteristic diagram showing a relationship between the output voltage V _O of the output differential amplifier 115 of FIG. 7 (that is, the output voltage of the current sensor 110) and the measured current I _in . The following description will focus on differences from the first embodiment.

If the first ground terminal 122 is between the second ground terminal 112 disconnected (corresponding to the case where SW1 is turned off), the current sensor 110 no current flows in the pull-up resistor R ₆ becomes inactive. Therefore, the output voltage V _O becomes the voltage (5 V) of the constant voltage source 125.

When the power supply terminal 121 and the power input terminal 111 are disconnected (corresponding to the case where SW3 is turned off), the current sensor 110 becomes inactive. Also, no current flows through the bias resistor R ₅ , the V _GS of the P-channel junction FET 333 becomes 0, and the P-channel junction FET 333 is turned on. Therefore, the output voltage V _O is very close to the ground potential (0 V) regardless of the current I _in to be measured. However, since there is a voltage drop due to the ON resistance of the P-channel junction FET 333, the output voltage V _O does not exactly match the ground potential (0V), and is about 0.1V, for example.

When the detection voltage input terminal 123 and the sensor output terminal 113 are disconnected (corresponding to the case where SW2 is turned off), the output voltage V _O is not transmitted to the electronic control unit 120 side. At this time, the detection voltage input terminal 123 becomes the voltage (5 V) of the constant voltage source 125.

  Hereinafter, the function of the disconnection detection unit 126 will be described.

Function 1: Disconnection Detection Between Power Supply Terminals When a voltage smaller than a voltage (for example, 0.2 V to 0.45 V) supplied to the negative power supply terminal of the output differential amplifier 115 is input, the disconnection detection unit 126 Detects that the power supply terminal 121 and the power input terminal 111 are disconnected.

Function 2: Other disconnection detection When the voltage of the detection voltage input terminal 123 becomes the voltage (5 V) of the constant voltage source 125, the disconnection detection unit 126 is connected between the first ground terminal 122 and the second ground terminal 112. It is detected that the circuit is disconnected or that the detection voltage input terminal 123 and the sensor output terminal 113 are disconnected.

Function 3: Positive overcurrent detection Voltage that is larger than the maximum value of the rated output voltage (for example, 4.5 V) and supplied to the positive power supply terminal of the output differential amplifier 115 (for example, 4.55 V to 4.V). When a voltage smaller than 8V) is input, the disconnection detection unit 126 detects that the measured current Iin is an overcurrent _{in the} positive direction (for example, the discharge direction of the battery).

Function 4: Negative-direction overcurrent detection Voltage that is smaller than the minimum value of the rated output voltage (for example, 0.5 V) and that is supplied to the negative power supply terminal of the output differential amplifier 115 (for example, 0.2 V to. When a voltage greater than 45V) is input, the disconnection detection unit 126 detects that the measured current Iin is an overcurrent _{in the} negative direction (for example, the charging direction of the battery).

  This embodiment can also achieve the same effects as those of the first embodiment. Also in this embodiment, it is possible to use a resistor instead of the constant current circuit as in the second embodiment, and in this case, the same effect can be obtained.

  The present invention has been described above by taking the embodiment as an example. However, it will be understood by those skilled in the art that various modifications can be made to each component of the embodiment within the scope of the claims. Hereinafter, modifications will be described.

In each embodiment, the case where the power supply side step-down unit and the ground side step-down unit are diodes has been described. However, in the modification, a transistor may be used instead of the diode. A circuit example in this case is shown in FIG. The positive side transistor Q ₁ (PNP type) is biased by the current flowing through the path of the power input terminal 111 → emitter → base → resistor R _Q1 → second ground terminal 112, for example, V _CE1 = 0. 2V. Similarly, the negative side transistor Q ₂ (NPN type) is biased (turned on) by current flowing through the path of the power input terminal 111 → resistor R _Q2 → base → emitter → second ground terminal 112, for example, V _CE2 = 0.2V.

  In each embodiment, both the power supply side step-down means and the ground side step-down means are provided, but in the modification, only one of them may be provided. In this case, it is preferable to provide only the power supply side step-down means in the first and second embodiments, and to provide only the ground side step-down means in the configuration of the third embodiment. This is because in the first and second embodiments, the disconnection abnormality between the first ground terminal 122 and the second ground terminal 112 is clearly distinguished from the overcurrent abnormality. In the third embodiment, This is to clearly distinguish a disconnection abnormality between the power supply terminal 121 and the power input terminal 111 from an overcurrent abnormality.

  In each embodiment, the power supply side step-down means and the ground side step-down means are provided in order to clearly distinguish between overcurrent abnormality and disconnection abnormality, but it is necessary to consider overcurrent abnormality when it is not necessary to distinguish between them. If not, the circuit configuration may be simplified by omitting the power supply side step-down means and the ground side step-down means.

In each embodiment, the case where the current sensor is a magnetic balance type has been described. However, in the modification, the current sensor may be a magnetic proportional type illustrated in FIG. In this case, in the current sensor 110 of FIGS. 1 and 7, the negative feedback differential amplifier 117, the negative feedback coil L _FB , and the detection resistor _RS are not required, and the output voltage of the Hall element 116 is directly output as the detection voltage V _S. What is necessary is just to input to the differential amplifier 115.

1 is an exemplary configuration diagram of a disconnection detection system according to a first embodiment of the present invention. FIG. 4 is an exemplary transfer characteristic diagram of an N-channel junction FET. FIG. 4 is an exemplary forward current vs. forward voltage characteristic diagram of a Schottky barrier diode. The circuit diagram which shows the specific structural example of the 1st constant current circuit and 2nd constant current circuit which are shown by FIG. FIG. 2 is an exemplary output characteristic diagram showing a relationship between an output voltage V _O of the output differential amplifier of FIG. 1 and a measured current I _in . The exemplary block diagram of the disconnection detection system which concerns on the 2nd Embodiment of this invention. Exemplary configuration diagram of a disconnection detection system according to a third embodiment of the present invention FIG. 8 is an exemplary output characteristic diagram showing a relationship between an output voltage V _O of the output differential amplifier of FIG. 7 and a measured current I _in . FIG. 3 is an exemplary circuit diagram in the case where a power supply side step-down unit and a ground side step-down unit are configured by transistors. (A) is a basic configuration diagram of a magnetic proportional current sensor, (B) is a basic configuration diagram of a magnetic balance type current sensor.

Explanation of symbols

100 Disconnection Detection System 110 Current Sensor 111 Power Supply Input Terminal 112 Second Ground Terminal 113 Sensor Output Terminal 114 Current Detection Unit 115 Output Differential Amplifier 116 Hall Element 117 Negative Feedback Differential Amplifier 119 Reference Voltage Source 120 Electronic Control Unit (ECU) )
121 power supply terminal 122 first ground terminal 123 detection voltage input terminal 125 constant voltage source 126 disconnection detector

Claims (12)

A current sensor, and an electronic control unit that supplies power to the current sensor,
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and a current to be measured. A current detection unit that outputs a detection voltage according to the output, an output amplifier that amplifies the detection voltage and outputs the detection voltage to the sensor output terminal, and an N channel provided between the power input terminal and the sensor output terminal A junction-type FET, and a bias resistor provided between the power input terminal and the second ground terminal, and a connection point between the bias resistor and the second ground terminal of the N-channel junction FET. A power supply side step-down means for connecting a gate and making the voltage supplied to the positive power supply terminal of the output amplifier smaller than the voltage of the power supply input terminal comprises the power supply input terminal and the positive power supply terminal. Disconnection detection system between the provided and has a current sensor and an electronic control unit during.   2. The disconnection detection system according to claim 1, wherein a voltage drop caused by the N-channel junction FET when the N-channel junction FET is turned on is smaller than a voltage drop caused by the power supply side step-down means. Disconnection detection system between sensor and electronic control unit.   3. The disconnection detection system according to claim 1 or 2, wherein the disconnection detection unit is abnormal when a voltage larger than a voltage supplied to the positive power supply terminal of the output amplifier is input to the disconnection detection unit. A disconnection detection system between the current sensor and the electronic control unit.   4. The disconnection detecting device according to claim 3, wherein the disconnection detecting device is larger than a maximum voltage in a voltage range corresponding to a rated range of the current to be measured and smaller than a voltage supplied to the positive power supply terminal of the output amplifier. A disconnection detection system between a current sensor and an electronic control unit, wherein the disconnection detection unit detects an overcurrent abnormality when a voltage is input to the disconnection detection unit. In the disconnection detection system according to any one of claims 1 to 4,
The power supply side step-down means includes a positive side diode having an anode connected to the power supply input terminal and a cathode connected to the positive power supply terminal of the output amplifier,
A disconnection detection system between a current sensor and an electronic control unit, wherein a positive constant current circuit or a positive resistance is provided between the cathode of the positive diode and the second ground terminal.   6. The disconnection detection system according to claim 5, wherein the amount of current flowing through the positive-side constant current circuit or the resistance value of the positive-side resistance is variably adjustable.   The disconnection detection system according to any one of claims 1 to 6, wherein the current sensor further makes a voltage supplied to a negative power supply terminal of the output amplifier larger than a voltage of the second ground terminal. A disconnection detection system between a current sensor and an electronic control unit, wherein a ground side step-down means is provided between the second ground terminal and the negative power supply terminal. A current sensor, and an electronic control unit that supplies power to the current sensor,
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and a current to be measured. A current detection unit that outputs a detection voltage corresponding to the output voltage, an output amplifier that amplifies the detection voltage and outputs the detection voltage to the sensor output terminal, and a P provided between the sensor output terminal and the second ground terminal. A channel junction FET, and a bias resistor provided between the power input terminal and the second ground terminal, and a connection point between the power input terminal and the bias resistor is connected to the P channel junction FET. A ground side step-down means for connecting a gate and making the voltage supplied to the negative power supply terminal of the output amplifier larger than the voltage of the second ground terminal includes the negative power supply terminal and the second ground terminal. Disconnection detection system between the provided and has a current sensor and an electronic control unit during.   9. The disconnection detection system according to claim 8, wherein a voltage drop caused by the P-channel junction FET when the P-channel junction FET is turned on is smaller than a voltage drop caused by the ground-side step-down means. Disconnection detection system between sensor and electronic control unit.   The disconnection detection system according to claim 8 or 9, wherein the disconnection detection unit is abnormal when a voltage smaller than a voltage supplied to the negative power supply terminal of the output amplifier is input to the disconnection detection unit. A disconnection detection system between the current sensor and the electronic control unit. In the disconnection detection system according to any one of claims 7 to 10,
The ground-side step-down means includes a negative diode having an anode connected to the negative power supply terminal of the output amplifier and a cathode connected to the second ground terminal;
A disconnection detection system between a current sensor and an electronic control unit, wherein a negative constant current circuit or a negative resistance is provided between the power input terminal and the anode of the negative diode. A current sensor that outputs a voltage corresponding to the current to be measured, and an electronic control unit that supplies power to the current sensor;
The electronic control unit includes a power supply terminal, a first ground terminal, a detection voltage input terminal, and a disconnection detection unit connected to the detection voltage input terminal,
The current sensor includes a power input terminal connected to the power supply terminal, a second ground terminal connected to the first ground terminal, a sensor output terminal connected to the detection voltage input terminal, and the sensor output. A P-channel junction FET provided between the terminal and the second ground terminal, and a bias resistor provided between the power input terminal and the second ground terminal, and the power input terminal A disconnection detection system between a current sensor and an electronic control unit, wherein a gate of the P-channel junction FET is connected to a connection point with the bias resistor.

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