JP5989171B1 - CURRENT DETECTION CIRCUIT AND ELECTRIC CONTROL DEVICE FOR VEHICLE HAVING THE CIRCUIT - Google Patents

Abstract

A current detection circuit capable of automatically switching an amplification factor without a signal from another is obtained. A diode connected in series with a current detection resistor, a parallel resistor connected in parallel with a series body of the diode and the current detection resistor, and a series body of the diode and the current detection resistor. And voltage detectors a and b for detecting voltages at both ends of the circuit constituted by the parallel resistor 16. [Selection] Figure 1

Description

  The present invention relates to a current detection circuit that performs current detection using a current detection resistor, and a vehicle electronic control device including the circuit.

In products that use electricity, it is often used to detect current. In order to detect the current, generally, a current detection resistor is used, and the current is often detected by measuring the voltage at both ends thereof.
For example, in an electronic control device for a vehicle, an improvement in failure detection accuracy is required by regulation of OBD (On-board diagnostics), and current detection may be used as a response. As a specific example, an expensive IC including a current detection circuit is used.

  In measuring the voltage across the current detection resistor, the dynamic range is generally fixed. For example, when the current is detected by amplification by an amplifier, the amplification factor of the amplifier is constant. Therefore, when the amplification factor of the amplifier is set for a large current, it becomes difficult to detect a small current, and when the amplification factor of the amplifier is set for a small current, it is difficult to detect a large current. In this case, it is necessary to prepare a large current amplifier and a small current amplifier separately.

  For example, Japanese Patent Application Laid-Open No. 2008-271574 (Patent Document 1) discloses a technique in which a large current and a small current can be detected by one amplifier by switching a resistor for setting the amplification factor of the amplifier according to a current value. Has been.

JP 2008-271694 A

  In the technique disclosed in Patent Document 1, a switching signal from a microcomputer or the like is required to switch the amplification factor of the amplifier. Further, the amplifier is more expensive than the diode, and there is a problem that the size is increased.

  The present invention is for solving the above-described problem, and provides a current detection circuit capable of automatically switching an amplification factor without a signal from another, and a vehicle electronic control device including the circuit. The purpose is to provide.

Current detecting circuit according to the present invention, the current detection circuit which performs current detection, diode, a parallel resistor connected the diode and parallel, formed of the first resistor and the series connection of the second resistor, the A bias circuit for supplying a bias current to the parallel resistor; a microcomputer having a voltage detection unit for detecting a voltage at both ends of the parallel resistor;
A drive element controlled by the microcomputer,
The partial pressure between the first resistor, the second resistor, and the parallel resistor is set so that the state of the load can be identified in the driving / non-driving state of the driving element. is there.

According to the current detection circuit according to the present invention, supply and diode, a parallel resistor connected the diode and parallel, formed of the first resistor and the series connection of the second resistor, a bias current to said parallel resistor A bias circuit, a voltage detection unit for detecting a voltage across the parallel resistor, a microcomputer for detecting a current flowing through a load, and a drive element controlled by the microcomputer, And the second resistance and the parallel resistance are set so that the state of the load can be identified in the driving / non-driving state of the driving element. In a driving state, a disconnection, a ground fault, and a power fault can be detected, and in a non-driving state, a disconnection and a ground fault can be detected .

1 is a circuit diagram of a vehicle electronic control device including a current detection circuit according to Embodiment 1 of the present invention. FIG. It is a figure which shows the relationship between the electric potential difference in the electric current detection part of the microcomputer of FIG. 1, and the electric current value which flows into a drive element. It is a circuit diagram of the vehicle electronic control apparatus provided with the electric current detection circuit by Embodiment 2 of this invention. It is a figure which shows the relationship between the state of the terminal of ECU of FIG. 3, and the voltage which generate | occur | produces in the electric current detection part of a microcomputer. It is the figure which represented the change of the voltage in the circuit shown in FIG. 3 with the time chart. It is a circuit diagram of the vehicle electronic control apparatus provided with the electric current detection circuit by Embodiment 3 of this invention. It is a circuit diagram of the vehicle electronic control apparatus provided with the electric current detection circuit by Embodiment 4 of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a current detection circuit according to the present invention and a vehicle electronic control device including the circuit will be described with reference to the drawings. In the drawings, the same reference numerals denote the same or corresponding parts.

Embodiment 1.
FIG. 1 is a diagram for explaining a first embodiment of the present invention, and shows a circuit configuration of an ECU and an engine component.

  In FIG. 1, reference numeral 10 denotes an ECU, and reference numeral 11 denotes an engine component including a battery 12 and a motor 13. The ECU 10 is controlled by a series body of the diode 14 and the current detection resistor 15, a parallel resistor 16 connected in parallel to the series body of the diode 14 and the current detection resistor 15, a microcomputer (hereinafter referred to as a microcomputer) 17, and the microcomputer 17. The driving element 18 is provided. The microcomputer 17 includes voltage detection units a and b that monitor voltages at both ends of a circuit including a diode 14 and a current detection resistor 15 and a parallel resistor 16, and detects a current value flowing through the motor 13. It has a function. The microcomputer 17 performs an operation based on the monitored voltage, and detects a load state of the motor 13 and outputs a signal necessary for each engine control.

  The motor 13 is controlled by a driving element 18 that rotates with the battery 12 as a power source and operates in accordance with a driving signal from the microcomputer 17. The value of the current c flowing through the motor 13 varies greatly depending on the load state and the like. The relationship between the electric current c flowing through the motor 13 and the electric potential difference between a and b input to the microcomputer 17, that is, the potential difference generated between the voltage detectors a and b is as follows when the current c flowing through the motor 13 is a small current. Only the parallel resistor 16 flows, and a voltage calculated from the resistance value and current of the parallel resistor 16 is generated in proportion to the value of the current c.

Here, the value of the current c increases, and the potential difference between the voltage detection units a and b is applied to the forward voltage Vf (hereinafter referred to as Vf) of the diode 14 and the voltage generated across the current detection resistor 15 . When the value is exceeded, the diode 14 is turned on, and current begins to flow through the diode 14 and the current detection resistor 15. After the diode 14 is turned on, the voltage calculated from the resistance value of the current detection resistor 15 and the current is dominant in the voltage between the voltage detection units a and b.

  As a result, the resistance serving as a reference for current detection before and after the diode 14 is turned on is switched from the parallel resistance 16 to the current detection resistance 15, so that even when the load of the motor 13 fluctuates and the current value fluctuates greatly, Both large currents can be detected linearly without overrange. FIG. 2 shows the relationship between the potential difference in the voltage detectors a and b of the microcomputer 17 and the value of the current flowing through the drive element 18.

  As described above, in the vehicle electronic control device including the current detection circuit according to the first embodiment, when the value of the current c flowing through the motor 13 is small, the diode 14 is not turned on and is parallel to the diode 14. A current flows only in the connected parallel resistor 16, and a voltage determined by the current and the parallel resistor 16 connected in parallel with the diode 14 is generated in the voltage detection units a and b of the microcomputer 17. When a current of a predetermined value or more flows, the diode 14 is turned on, and the voltage generated in the voltage detection units a and b of the microcomputer 17 is equal to the Vf component of the diode 14 and the current detection resistor 15 connected in series with the diode 14. A sum of voltages determined by the current is generated.

Therefore, since the output ratio of the voltage and current generated in the voltage detectors a and b of the microcomputer 17 is switched between a large current and a small current, a large current and a small current can be detected simultaneously by one amplifier. In addition, as a response to OBD, by supplying a bias current and changing the current flowing in the circuit in each failure mode (disconnection, ground fault, power fault), it becomes possible to identify the fault, and it is expensive. An IC is also unnecessary, and costs can be reduced.

Embodiment 2.
Next, a vehicle electronic control device including a current detection circuit according to Embodiment 2 of the present invention will be described. In the following description, a circuit corresponding to the OBD of the O2 heater will be described as an example in the ECU that performs electronic control of the engine.

FIG. 3 is a diagram illustrating the second embodiment, and is a circuit configuration diagram illustrating a configuration of the engine component 11 including the ECU 10, the battery 12, and the O 2 heater 30.
The ECU 10 includes a diode 14, a parallel resistor 16 connected in parallel to the diode 14, a microcomputer 17, a drive element 18 controlled by the microcomputer 17, and a bias circuit 31. The microcomputer 17 has voltage detection units a and b that monitor voltages at both ends of a circuit constituted by the diode 14 and the parallel resistor 16, and has a function of detecting a current value flowing through the O 2 heater 30. The microcomputer 17 performs an operation based on the monitored voltage, and detects a current flowing through the O2 heater 30 and outputs a signal necessary for each engine control. The bias circuit 31 includes a series body of a first resistor 31a and a second resistor 31b, and supplies a stable bias current to the parallel resistor 16 connected in series.

  The O2 heater 30 is controlled by a drive element 18 that uses the battery 12 as a power source and operates in accordance with a drive signal from the microcomputer 17. Note that the potential difference between a and b input to the microcomputer 17, that is, the potential difference between the voltage detectors a and b changes depending on whether the drive element 18 is driven / not driven or normal / failure. The voltage division settings of the first resistor 31a, the second resistor 31b, and the resistor 16 are set in each load state (normal, disconnected, ground fault (terminal ground short (terminal ground short)) in the driving / non-driving state of the driving element 18. ), Skylight (terminal power supply short)).

The vehicle electronic control device including the current detection circuit according to the second embodiment is configured as described above, and the operation thereof will be described next.
First, the potential difference between the voltage detectors ab in each load state when the drive element 18 is in the drive state is as follows.
When the O2 heater 30 is normal, the divided voltages of the first resistor 31a, the second resistor 31b, and the resistor 16 are set so that current flows from the battery 12 through the O2 heater 30 and the driving element 18 to the diode 14. deep. Therefore, since a current flows through the diode 14, the potential difference between the voltage detection units a and b of the microcomputer 17 is equal to the Vf of the diode 14.

  Further, when the O2 heater 30 is disconnected, a current flows through the path of the first resistor 31a, the driving element 18, and the parallel resistor 16, and a potential difference is generated between the voltage detectors a and b. At this time, the first resistor 31a and the parallel resistor 16 are divided so that a potential difference of, for example, about half of Vf of the diode 14 occurs between the voltage detection units a and b so that no current flows in the diode 14. Is set in advance. Therefore, the potential difference between the voltage detectors a and b of the microcomputer 17 is about half of Vf of the diode 14.

  At the time of ground fault, the current of the bias circuit 31 flows directly from the first resistor 31a to the ground. Therefore, the potential difference between the voltage detection units a and b of the microcomputer 17 is 0V. Moreover, since it is assumed that the battery 12 is directly connected to the terminal d of the ECU 10 at the time of a power fault, an overcurrent exceeding the rating is generated in the diode 14 through the driving element 18 of the O2 heater 30. Therefore, since an overcurrent flows through the diode 14, the potential difference between the voltage detection units a and b of the microcomputer 17 is such that Vf of the diode 14 is larger than usual. Here, by providing a control or a circuit for stopping the driving of the driving element 18, the diode 14 and the driving element 18 can be protected.

Next, the potential difference between the voltage detectors a-b in each load state when the driving element 18 is stopped is as follows.
When the O2 heater 30 is normal, the partial pressure of the second resistor 31b and the parallel resistor 16 is set so that current flows from the battery 12 through the O2 heater 30 and the second resistor 31b to the diode 14. Therefore, since a current flows through the diode 14, the potential difference between the voltage detection units a and b of the microcomputer 17 is equal to the Vf of the diode 14.

  When the O2 heater 30 is disconnected, a current flows through the path of the first resistor 31a, the second resistor 31b, and the parallel resistor 16, and a potential difference is generated between the voltage detectors ab. At this time, the first resistor 31a, the second resistor 31b, and the parallel resistor 16 are generated so that a potential difference of, for example, about half of Vf occurs between the voltage detection units a and b so that no current flows through the diode 14. Set the partial pressure of. Therefore, the potential difference between the voltage detectors a and b of the microcomputer 17 is about half of Vf of the diode 14.

  At the time of ground fault, the current of the bias circuit 31 flows directly from the first resistor 31a to the ground. Therefore, the potential difference between the voltage detection units a and b of the microcomputer 17 is 0V. In addition, the voltage division of the second resistor 31b and the parallel resistor 16 is set so that a current flows through the diode 14 through the second resistor 31b during a power fault. Therefore, since a current flows through the diode 14, the potential difference between the voltage detection parts a and b of the microcomputer 17 is equal to the Vf of the diode 2. In addition, although it is not possible to detect a fault with respect to a power fault at the time of non-driving, the fault detection defined by OBD is “that two or more of a disconnection, a ground fault, and a power fault can be detected”, which is a request of OBD. Can be satisfied.

  A bias circuit 31 composed of a series body of a first resistor 31a and a second resistor 31b is connected in series to the parallel resistor 16 of the first embodiment, and a stable bias current is supplied to the parallel resistor 16. It is also possible.

  As described above, the vehicle electronic control device including the current detection circuit according to the second embodiment can satisfy the OBD requirement in each of the driving / non-driving states.

  4 shows the relationship between the potential difference between the voltage detectors a and b of the microcomputer 17 and the state (normal / failure) of the terminal d of the ECU 10. FIG. 5 shows the change in voltage in the circuit shown in FIG. Is represented by a time chart.

Embodiment 3.
Next, a vehicle electronic control device including a current detection circuit according to Embodiment 3 of the present invention will be described.
FIG. 6 is a diagram illustrating a vehicle electronic control device including a current detection circuit according to the third embodiment. In the first or second embodiment, the potential difference between the voltage detection units a and b of the microcomputer 17 is directly detected by the microcomputer 17, but as shown in FIG. You may detect by amplifying by inputting into the operational amplifier 60 grade | etc.,. Other configurations are the same as those in the second embodiment, and the detailed description is omitted by giving the same reference numerals.
According to the third embodiment, the potential difference between the voltage detection units a and b of the microcomputer 17 can be measured and identified more accurately.

Embodiment 4.
Next, a vehicle electronic control device including a current detection circuit according to Embodiment 4 of the present invention will be described.
FIG. 7 is a diagram illustrating a vehicle electronic control device including a current detection circuit according to the fourth embodiment. In the first to third embodiments, the potential difference between both ends of the diode 14 is detected. However, as shown in FIG. 7, it is possible to cope with the problem by measuring only the voltage on the anode side of the diode 14 with reference to the ground. is there. Other configurations are the same as those in the second embodiment, and the detailed description is omitted by giving the same reference numerals.

  As described above, the first to fourth embodiments have been described. However, the present invention is not limited to this, and within a range that does not depart from the gist of the present invention, these configurations are appropriately combined, or some modifications are made to the configurations. It is possible to add or partially omit the configuration.

DESCRIPTION OF SYMBOLS 10 ECU, 11 Engine structure, 12 Battery, 13 Motor, 14 Diode, 15 Current detection resistance, 16 Parallel resistance, 17 Microcomputer (microcomputer), 18 Drive element, 30 O2 heater, 31 Bias circuit, 31a 1st resistance , 31b Second resistor, 60 Amplifier (op-amp), a, b Voltage detector

Claims (4)

In the current detection circuit that performs current detection,
A diode,
A parallel resistor connected in parallel with the diode;
A bias circuit configured by a series body of a first resistor and a second resistor, and supplying a bias current to the parallel resistor;
A microcomputer having a voltage detector for detecting the voltage across the parallel resistor, and detecting a current flowing through the load;
A drive element controlled by the microcomputer ,
The partial pressure between the first resistor, the second resistor, and the parallel resistor is set so that the state of the load can be identified in the driving / non-driving state of the driving element. A characteristic current detection circuit. The current detection circuit according to claim 1 , further comprising an amplification device that amplifies a voltage detected by the voltage detection unit. With connecting one of the connection portion with the parallel resistor and the diode to ground, connect one detector of said voltage detecting unit to the ground, or claim 1, characterized in that detected by the voltage of the ground reference 3. The current detection circuit according to 2. Vehicle electronic control apparatus characterized by comprising a current detecting circuit according to any one of claims 1 to 3.