JP2000245054A - Judging device for imperfect current application - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge layer short and current leakage which are not complete disconnection and short, as imperfect current application, when imperfect current application of a current applying means or a load is judged. SOLUTION: A first and a second reference MOSFET's QB, QB' are connected in parallel with a power MOSFET QA interposing in a power supplying line from a battery 1 to a running sensor S. Two reference resistors Rr1, Rr2 whose resistance values are so adjusted that a current of the maximum value and a current of the minimum value of an ordinary current in the sensor S flow are connected in series with the first and the second reference MOSFET's QB and QB', respectively. A voltage between the drain and the source of the power MOSFET QA which corresponds to a current actually flowing in the sensor S is compared with the voltages between the drains and the sources of the first and the second reference MOSFET's QB, QB' which voltages correspond to currents equivalent to the maximum value and the minimum value of the ordinary current of the sensor S which flow in the reference resistors Rr1 and Rr2. Based on the compared result, generation of short circuit and disconnection is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-carrying fault judging device for judging a fault in a load connected to a power supply via a current-carrying means.

[0002]

2. Description of the Related Art A vehicle is equipped with a large number of electric loads such as various sensors, motors, actuators, and displays, and these are generally supplied with electric power from a battery via a wire harness.

[0003] Since these electric loads become inoperative when the wire harness itself or the wire harness is disconnected or short-circuited, the disconnection or short-circuit of the load or the wire harness is quickly detected in order to ensure the normal function of the vehicle. It is very important to do so, and many devices for that purpose have been provided.

FIG. 5 is a circuit diagram showing an example of a conventional device used for detecting such a load or disconnection or short-circuit of a wire harness. In this conventional device, a 12V power supply from a battery VB is used. Resistance R22 and connector C
The load of the vehicle via N21, here, the running sensor S which outputs a running pulse having the number of pulses per unit time according to the running speed of the vehicle, is intermittently output at a predetermined sampling cycle via the switching transistor Tr21. To supply.

More specifically, a microcomputer 21 mounted on a vehicle applies a pulse signal F1 of the above-described sampling period from an output port Out21 thereof to a base of a switching transistor Tr21 via a resistor R23, and to a battery VB. By intermittently conducting the collector of the connected switching transistor Tr21 to the emitter of the grounded switching transistor Tr21 in synchronization with the cycle of the pulse signal F1, the 12V power supply from the battery VB is intermittently transmitted to the travel sensor S. Supplying.

Then, the traveling sensor S and the traveling sensor S and the connector C
In order to detect a disconnection or short-circuit of the wire harness WH21 connecting between the microcomputer 21 and the input port In21 of the microcomputer 21 and the collector of the switching transistor Tr21, the pull-up resistor R21 sets a voltage of 5 V between the input port In21 and the collector of the switching transistor Tr21. The pull-up resistor R21 and the resistor R2 are connected to a pull-up power supply Vp21 and pulled up.
2, the anode is connected to the pull-up resistor R21 and the cathode is connected to the diode D21 whose breakdown voltage is greater than 5V and smaller than 12V in order to make the direction from the pull-up resistor R21 toward the resistor R22 a forward direction. Resistance R
22 so as to be connected thereto.

The resistor R23 and the microcomputer 2
The capacitor C21 provided between the first output port Out21 and the output port Out21 is a filter for removing a noise component in the pulse signal F1.

In the conventional device described above, if the traveling sensor S and the wire harness WH21 are normal, the pulse signal F1
Is "L", the 12V power from the battery VB is supplied to the travel sensor S via the connector CN21 and the wire harness WH21.
The level of the detection signal F2 input to the first input port In21 becomes “H” according to the potential of the pull-up power supply Vp21 pulled up by the pull-up resistor R21,
When the pulse signal F1 is “H”, the battery VB and the pull-up power supply Vp21
Since it is grounded via the collector-emitter 21, it becomes “L”.

Further, in the above-described conventional apparatus, when the running sensor S and the wire harness WH21 are disconnected, when the pulse signal F1 is "L", the potential on the anode side of the capacitor C21 is approximately 12 V close to the voltage of the battery VB. Therefore, the level of the detection signal F2 input to the input port In21 of the microcomputer 21 becomes approximately 12 V in relation to the breakdown voltage of the capacitor C21, and when the pulse signal F1 is “H”, the battery VB and the pull-up Since the power supply Vp21 is grounded via the collector-emitter of the switching transistor Tr21, "L"
Becomes

Further, in the above-described conventional device, when a short circuit occurs in the travel sensor S or the wire harness WH21,
When the pulse signal F1 is "L", the battery VB and the pull-up power supply Vp21 are body-grounded via the short-circuit portion of the travel sensor S and the wire harness WH21, so that the pulse signal F1 is "L", and the pulse signal F1 is "H". In addition, since the battery VB and the pull-up power supply Vp21 are grounded via the collector-emitter of the switching transistor Tr21, the voltage becomes "L".

Therefore, in the conventional device, the pulse signal F
1 and “L” and “H” states of the detection signal,
By confirming the relationship between the state of "H" and the potential, the traveling sensor S and the wire harness WH21 are distinguished from each other to determine whether they are normal or abnormal, and if abnormal, whether they are broken or short-circuited. can do.

[0012]

However, in the above-described conventional apparatus, the core wire of the wire harness WH21 repeatedly contacts the vehicle body in small increments in accordance with the vibration of the vehicle.
, When the pulse signal F1 is “L” and the collector-emitter of the switching transistor Tr21 is in a non-conductive state, the battery VB and the pull-up power supply Vp21 are not grounded enough as in the case of disconnection. The level of the detection signal F2 is equal to the pull-up resistance R2.
It becomes "H" according to the potential of the pull-up power supply Vp21 pulled up by 1 and is determined to be normal,
There was a problem that it could not be detected.

The present invention has been made in view of the above circumstances,
The object of the present invention is not limited to the vehicle, in determining the energization failure of the load connected to the various power supplies through the energizing means,
It is an object of the present invention to provide an energization failure determination device capable of determining occurrence of a rare short or current leak that is not a complete disconnection or short, as an energization failure.

[0014]

According to a first aspect of the present invention, there is provided a power supply failure determining apparatus for determining a power supply failure of a load connected to a power supply via a power supply means. A power MOSFET connected in series between the power supply and the load, for turning on and off the connection of the load to the power supply;
A reference circuit unit connected in parallel with a series circuit of an OSFET and the load, wherein the reference circuit unit includes a series circuit of a reference MOSFET and a reference resistor equivalent to the power MOSFET; If the resistance value of the resistor is
A reference current equivalent to the maximum value of the current normally flowing through the load is set to the maximum current resistance value flowing between the drain and the source of the reference MOSFET, and the power MOSFET
A short-circuit judging means for judging a short-circuit state in the load and the load based on a difference between a T drain-source voltage and a drain-source voltage of the reference MOSFET; And outputting a determination signal having a content corresponding to the determination result of the short circuit state in the means and the load.

According to a second aspect of the present invention, in the first embodiment, the reference circuit section includes the reference MOSFET.
T and a series circuit of the reference resistor, wherein the resistance value of the reference resistor in one of the series circuits is set to the maximum current resistance value, The resistance value of the reference resistor in the other one of the series circuits has a reference current equivalent to the minimum value of the current that normally flows through the load, and the reference current between the drain and the source of the reference MOSFET in the other one of the series circuits. The short-circuit determination means is configured to set the minimum current resistance value to flow, based on the difference between the drain-source voltage of the power MOSFET and the drain-source voltage of the reference MOSFET in the one series circuit. Means and means for determining a short circuit condition in the load,
Disconnection determining means for determining a disconnection state in the energizing means and the load based on a difference between an FET drain-source voltage and a drain-source voltage of the reference MOSFET in the another one of the series circuits, The disconnection determination means outputs a determination signal having a content corresponding to the determination result of the disconnection state in the energizing means and the load.

According to a third aspect of the present invention, there is provided an energization failure judging device according to the first or second aspect of the present invention, wherein the judging data representing the content of the output judgment signal is transmitted. The apparatus further includes a determination content data generation unit to be generated, and a determination content data storage execution unit that stores the determination data generated by the determination content data generation unit in a non-volatile storage unit in a readable manner.

According to a fourth aspect of the present invention, there is provided the power supply failure judging device according to the first, second, or third aspect, wherein the reference MOSFET comprises the power MOSFET. And the resistance value of the reference resistance is equal to the resistance value of the load × (the power MO
Number of MOSFETs constituting SFET / the reference MOS
(The number of MOSFETs constituting the FET).

According to a fifth aspect of the present invention, there is provided a current-carrying fault judging device according to the first, second, third or fourth aspect of the present invention, wherein the reference MOSFET is in the same chip as the power MOSFET. It is assumed that it is formed in.

According to the present invention, the reference current equivalent to the maximum value of the current normally flowing to the load flows through the series circuit of the reference MOSFET and the reference resistor, while the power MOSFET Since a current whose magnitude changes due to an overcurrent or the like flows through a series circuit of the load and the load, the load is actually loaded using the difference between the drain-source voltage of the power MOSFET and the drain-source voltage of the reference MOSFET. Based on whether or not the flowing current exceeds the maximum value of the current that normally flows through the load, the short-circuit state of the energizing unit and the load is differentially determined by the short-circuit determining unit.

According to a second aspect of the present invention, the reference current equivalent to the minimum value of the normal current flowing through the load is provided in the first aspect of the present invention. Flows into a series circuit of a reference MOSFET and a reference resistor of another series circuit of a plurality of series circuits constituting a reference circuit unit, while a power MOSFET
Since a current whose magnitude changes due to disconnection or the like flows through a series circuit of the power MOSFET and the load, the drain-source voltage of the power MOSFET and the drain-source of the reference MOSFET in another one of the plurality of series circuits are connected. Based on whether the current actually flowing through the load exceeds the minimum value of the current that normally flows through the load, the disconnection state in the energizing means and the load is determined by the disconnection determination means based on whether the current flowing through the load exceeds the minimum value of the current flowing normally through the load. Is determined.

According to a third aspect of the present invention, the content of the determination signal from the short-circuit determining means is represented in the first or second aspect of the present invention. Judgment data or judgment data representing the contents of judgment signals from the short-circuit judging means and the disconnection judging means is generated by the judgment content data generating means, and this judgment data is output by the judgment content data storage executing means when power supply is cut off. The data is also written and readably stored in the non-volatile storage means in which the stored contents are not lost.

According to a fourth aspect of the present invention, there is provided a power supply failure judging device according to the first, second or third aspect of the present invention,
When each of the reference MOSFET and the reference MOSFET is formed by a MOSFET, a value obtained by multiplying a resistance value of the load by a ratio of the number of the MOSFETs forming the power MOSFET to the number of the MOSFETs forming the reference MOSFET is a reference equivalent to the load. By setting a predetermined value of the resistance, the power MOSFE
The reference MOSFE for the number of MOSFETs constituting T
Even if the number of MOSFETs constituting T is reduced, the resistance value of the reference resistance always becomes a value equivalent to the load.

According to a fifth aspect of the present invention, there is provided a power supply failure judging device according to the first, second, third or fourth aspect of the present invention.
Since the FET and the reference MOSFET are formed in the same chip, the power MOSFET and the reference MOSFET
T is formed by the same process.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 1 shows a vehicle power supply failure determination device (hereinafter abbreviated as “determination device”) according to a first embodiment of the present invention.
FIG. 1 is a circuit diagram showing a schematic configuration of a partial block diagram,
The determination device of the embodiment includes a vehicle battery (corresponding to a power supply) and a travel sensor S (corresponding to a load) indicated by reference numeral 1 in FIG.
, A reference power supply circuit 7 connected to the load power supply control IC 5, and a unit time per unit time corresponding to the traveling speed of the vehicle from the travel sensor S. A microcomputer (hereinafter abbreviated as "microcomputer") 9 to which a traveling pulse having the number of pulses is input, a non-volatile memory (NVM) 11 connected to the microcomputer 9, and an external diagnostic tester 15 are connected. And an interface 13 for performing the operations.

Here, the configuration of the load power supply control IC 5 and its basic operation will be described.

The load power supply control IC 5 has a power connection terminal T1 to which a DC power supply VB (= 12V) composed of a vehicle-mounted battery is connected, as indicated by a portion surrounded by a dotted line in the detailed circuit diagram of FIG. A load connection terminal T2 to which a load L is connected, an adjustment resistance connection terminal T3 to which a variable resistance RV for adjusting an overcurrent determination value is connected, a reference resistance connection terminal T4 to which a reference resistance Rr equivalent to the load L is connected, A signal input terminal T to which an external switch C1 for instructing driving of the load L is connected.
5, and a signal output terminal T6 to which the microcomputer 9 is connected.
Of the six external connection terminals.

The load power supply control IC 5 includes a power MOSFET QA for cutting off an overcurrent to the load L connected to the load connection terminal T2, and a reference circuit used for detecting an overcurrent state of the load L. Reference MOSFET QB and power MOSFET QA configured together with Rr
CPN for comparing the voltage between the drain and the source of the reference MOSFET QB and the power MOSFET QA and the reference MOSFET Q according to the comparison result of the comparator CP.
A drive circuit DR for driving B on is provided.

The power MOSFET QA and the reference MO
Each of the SFETs QB is a DMOS (Double D
It is an N-channel enhancement type having an expulsion MOS structure, and is composed of a plurality of MOSFETs. The power MOSFET QA and the reference MOSFET QB are formed on the same chip by the same process.

MOS constituting power MOSFET QA
Number of FETs and MOSF that constitutes reference MOSFET QB
The number of ETs has a relationship of QA> QB, and the reference MOSFE
The smaller the number of MOSFETs forming the TQB, the smaller the chip occupation area of the reference MOSFET QB can be.

In the following description, as an example, the power MO
Number of MOSFETs constituting SFET QA and reference MOS
The ratio of the number of MOSFETs constituting FET QB to Q
A: QB = 1000: 1.

The drains D of the power MOSFET QA and the reference MOSFET QB are connected to the power connection terminal T.
1 is connected to the DC power supply VB via the
The gates TG of the SFET QA and the reference MOSFET QB are connected to the drive circuit DR via resistors R7 and R8, and the source SA of the power MOSFET QA is connected to the load L via the load connection terminal T2. The source SB is connected to the reference resistance Rr via the reference resistance connection terminal T4.

By the connection relation described above, the reference MO
The series circuit of the SFET QB and the reference resistor Rr has a power M
The reference circuit is equivalent to a series circuit of the OSFET QA and the load L, and the power MOSFET QA and the load L
And connected in parallel with the series circuit.

When the power MOSFET QA and the reference MOSFET QB are operating in the pinch-off region, the power MOSFET QA and the reference MOSFET
ETQB constitutes a current mirror, and a power MOSFE
TQA drain current IDQA and reference MOSFET QB
Between the drain current IDQB and the power MOSFET
Number of MOSFETs constituting TQA and reference MOSFET
Depending on the ratio to the number of MOSFETs constituting QB, ID
The relationship of QA = 1000XIDQB holds.

Therefore, for example, the power MOSFET Q
A drain current IDQA = 5A, reference MOSFET Q
When the drain current IDB of B is 5 mA, the drain-source voltage VDSA of the power MOSFET QA
And the drain-source voltage VD of the reference MOSFET QB
SB matches, and the gate-source voltage VTGSA of the power MOSFET QA matches the gate-source voltage VTGSB of the reference MOSFET QB.

The reference resistance Rr is for setting an overcurrent determination value for determining whether an overcurrent is flowing to the load L. The resistance value of the reference resistance Rr is the power M
The same voltage as the drain-source voltage VDSA of the power MOSFET QA, which is generated when the load current of 5 A flows through the load L when the OSFET QA is turned on, is equal to the reference M
The value is set to a value generated between the drain and the source when the OSFET QB is turned on.

More specifically, when the reference MOSFET QB is completely turned on, the voltage of the DC power supply VB is substantially applied across the reference resistor Rr.
QA drain current IDQA = 5A, reference MOSFET
Since the drain current IDQB of QB is 5 mA,
The resistance value of the reference resistor Rr is Rr = 12V / 5mA = 1.4.
It is set to KΩ.

The positive-phase input terminal of the comparator CP has a drain-source voltage VDSA of the power MOSFET QA.
Is divided by the parallel resistance of the resistors R1 and R3 and the resistance R2, and is input. The negative-phase input terminal of the comparator CP receives the drain-source voltage VDSB of the reference MOSFET QB. The output of the power MOSF
ETQA drain-source voltage VDSA is the reference MO
It becomes “H” when the voltage exceeds the drain-source voltage VDSB of the SFET QB, and becomes “L” when the drain-source voltage VDSA of the power MOSFET QA falls below the drain-source voltage VDSB of the reference MOSFET QB.

The power MOSFET QA and the reference M
When all of the OSFETs QB are off, the input potential of the positive-phase input terminal of the comparator CP becomes a potential obtained by dividing the voltage of the DC power supply VB by the resistors R1 and R2.
Since the resistance values of the resistors R1 and R2 are set so that this potential is always higher than the input potential of the negative-phase input terminal of the comparator CP, the case where both the power MOSFET QA and the reference MOSFET QB are in the off state That is, when the external switch C1 is not operated and the signal instructing the driving of the load L is not input to the driving circuit DR via the input terminal T5, the output of the comparator CP is fixed to “H”. You.

The drive circuit DR has a charge pump output voltage VP (= VB + 10) which is a boosted voltage of the DC power supply VB.
V) is supplied to the collector of the NPN transistor Tr1.
And an NPN transistor Tr2 having a collector connected to the emitter of the transistor Tr1. A connection point between the emitter of the transistor Tr1 and the collector of the transistor Tr2 is connected to the power MOSFET QA and the reference through the resistors R7 and R8. It is connected to the gate TG of the MOSFET QB.

When a signal for instructing driving of the load L is input from the external switch C1 connected to the input terminal T5, the drive circuit DR turns on the transistor Tr1 and turns off the transistor Tr2 to charge. The pump output voltage VP is applied to the gates TG of the power MOSFET QA and the reference MOSFET QB, and these are turned on.

On the other hand, the drive circuit DR includes an external switch C
When there is no signal input from No. 1, the transistor Tr1 is turned off and the transistor Tr2 is turned on, the application of the charge pump output voltage VP to the gate TG of the power MOSFET QA and the reference MOSFET QB is stopped, and these are driven off. ing.

When the output of the comparator CP is "H", the drive circuit DR turns off the transistor Tr1 and turns off the transistor Tr1 even if a signal instructing the drive of the load L is input from the external switch C1. Tr2 is turned on, and the power MOSFET QA and the reference MOSFET
Charge pump output voltage V for gate TG of TQB
It is configured to stop application of P and drive them off.

A diode D1 having a cathode connected to a connection point of the resistors R7 and R8 and an anode connected to a positive-phase input terminal of the comparator CP, a connection point of the resistors R1 and R2, and a positive-phase input of the comparator CP. The resistor R5 interposed between the terminals constitutes a hysteresis circuit.

The resistor R3, the MOSFET Q2 having a source connected to the resistor R3, and the MOSFET
Power supply VB equal to or higher than the gate of TQ2 and DC power supply VB
A resistor R4 interposed between + 5V, a MOSFET Q1 having a source connected to the gate of the MOSFET Q2,
A Zener diode ZD2 having an anode connected to the gate of the OSFET Q1, a cathode of the Zener diode ZD2, a power MOSFET QA, and a reference MOSFET.
A circuit including a resistor R6 interposed between the gate TG of the TQB and a resistor R9 interposed between the source and the gate of the MOSFET Q1 changes an overcurrent determination value regarding the load L between the pinch-off region and the ohmic region. It is for.

Next, the operation (operation) of the load power supply control IC 5 configured as described above will be described.

(A) Operation in the pinch-off region First, the power MOSFET QA is turned on by applying the charge pump output voltage VP from the drive circuit DR to the gate TG, and then the drain of the power MOSFET QA is turned on.
The power MOSFET QA operates in a pinch-off region until the source-to-source voltage VDSA is saturated. In this pinch-off region, the power MOSFET after ON driving is operated.
The drain current IDQA of the TQA rises toward the final load current value determined by the circuit resistance.

Therefore, the gate-source voltage VTGSA of the power MOSFET QA is equal to the drain current IDQA.
The value is determined by the power MOSFET QA
Of the power MOSFET QA due to the mirror effect of the gate-drain capacitance CGD caused by the decrease in the drain-source voltage VDSA.

On the other hand, application of charge pump output voltage VP from drive circuit DR to gate TG causes reference MOSFE
When the TQB is turned on, the power M that is turned on at the same time
The drain current IDQA of the OSFET QA reaches 5A,
Until the drain current IDQB of the reference MOSFET QB reaches 5 mA equivalent to this, the reference MOSFET Q
The gate-source voltage VTGSB of B is a power MOS
It rises so as to have the same value as the gate-source voltage VTGSA of the FET QA.

However, after the drain current IDQB of the reference MOSFET QB reaches 5 mA, the drain current IDQB becomes constant at 5 mA in the pinch-off region.
The GSB is also constant, so that the power MO
The gate-source voltage V of the power MOSFET QA increases with the increase of the drain current IDQA of the SFET QA.
The relationship between TGSA and the gate-source voltage VTGSB of the reference MOSFET QB is VTGSB <VTGSA.

The drain-source voltage VDSA of the power MOSFET QA is
Gate-source voltage VTGSA and power MOSFET
Sum of TQA and drain-gate voltage VTGD (VD
SA = VTGSA + VTGD), and the reference MOSFE
The drain-source voltage VDSB of TQB is equal to the reference MO
Since the sum of the gate-source voltage VTGSB of the SFET QB and the drain-gate voltage VTGD of the reference MOSFET QB (VDSB = VTGSB + VTGD), VDSA-VDSB = VTGSA-VTGSB.

Here, the gate-source voltage VTGSA of the power MOSFET QA is
Corresponding to the drain current IDQA of
Gate-source voltage VTGS of reference MOSFET QB
B corresponds to the drain current IDQB of the reference MOSFET QB which is constant at 5 mA, and the reference MO
The drain current IDQB of the SFET QB = 5 mA is a value corresponding to the drain current IDQA = 5 A of the power MOSFET QA as described above.

Therefore, the gate-source voltage VTGSA of the power MOSFET QA and the reference MOSFET QB
(VTGSA) from the gate-source voltage VTGSB of
-VTGSB) means power MOSFE
From the drain current IDQA of the TQA, the drain current IDQA of the power MOSFET QA corresponding to the drain current IDQB of the reference MOSFET QB which becomes constant at 5 mA =
You will see the value of IDQA-5A minus 5A.

That is, if a difference (VDSA-VDSB) between the drain-gate voltage VTGD of the power MOSFET QA and the drain-gate voltage VTGD of the reference MOSFET QB, which is equal to VTGSA-VTGSB, is detected, the value of IDQA-5A is obtained. Is obtained.

When the drive circuit DR turns on the power MOSFET QA and the reference MOSFET QB in accordance with a signal for instructing driving of the load L input from the external switch C1, immediately thereafter, the drive circuit DR is connected to the positive-phase input terminal of the comparator CP. A value obtained by dividing the input voltage VDSA between the drain and the source of the power MOSFET QA by the parallel resistance of the resistors R1 and R3 and the resistance R2, that is, VDSA × (R1 // R3) / ｛(R1 // R3) + R2｝... (A), the drain-source voltage VDSB of the reference MOSFET QB input to the negative-phase input terminal of the comparator CP.
Is larger, the output of the comparator CP becomes “L”.

However, after that, the power MOSFET QA
When the reference MOSFET QB operates in the pinch-off region, the value of (a) inputted to the positive-phase input terminal of the comparator CP gradually increases, and the comparator C
When the voltage exceeds the drain-source voltage VDSB of the reference MOSFET QB input to the negative-phase input terminal of P, the output of the comparator CP is inverted from “L” to “H”.

When the output of the comparator CP is inverted from "L" to "H", the drive circuit DR stops applying the charge pump output voltage VP to the power MOSFET QA and the reference MOSFET QB.
When the QA and the reference MOSFET QB are driven off and their gates TG are grounded, the cathode side potential of the diode D1 is obtained by subtracting the forward voltage of the Zener diode ZD1 from the drain-source voltage VDSA of the power MOSFET QA, (VDSA -0.7).

Therefore, when the power MOSFET QA and the reference MOSFET QB are off, the DC power supply V
The current caused by the conduction of B flows in the order of parallel resistance (R1 // R3) → resistance R5 → diode D1, and the potential of the positive-phase input terminal of the comparator CP is determined by the drive circuit DR
It is lower than when the QA and the reference MOSFET QB are driven on.

In the power MOSFET QA and the reference MOSFET QB, the potential of the positive-phase input terminal of the comparator CP is equal to the difference (VDSA-VDSB) between the drain-gate voltage VTGD of the power MOSFET QA and the drain-gate voltage VTGD of the reference MOSFET QB. ) Until the potential of the positive-phase input terminal of the comparator CP decreases to (VDSA-VDSB) until the potential of the comparator CP decreases ((VDSA-VDSB)). Is turned on from the "H" to "L" by the drive circuit DR.

The hysteresis circuit formed by the diode D1 and the resistor R5 is merely an example, and the power MOS
The circuit configuration for providing hysteresis between the transition point from ON to OFF by the drive circuit DR of the drive state of the FET QA and the reference MOSFET QB and the transition point from OFF to ON is based on the diode D1 and the resistor R5 described above. Various other than the hysteresis circuit can be considered.

By the way, the fact that the power MOSFET QA, which has been driven on, is turned off by the drive circuit DR as the output of the comparator CP is inverted from “L” to “H” means that the load L is too high. Since the current is flowing, the current is cut off, and the drain of the power MOSFET QA input to the positive-phase input terminal of the comparator CP at the time when the driving state of the power MOSFET QA by the driving circuit DR changes from ON to OFF. −Source voltage VDSA
Is a value serving as a reference for determining the overcurrent of the load L.

The power MOS by the drive circuit DR
If the value of the drain-source voltage VDSA of the power MOSFET QA at the time when the driving state of the FET QA changes from on to off is VDSATH, VDSATH-VDSB = R2 / (R1 // R3) × VDSB (when VDSB = 5 mA ) ... (b)

Therefore, the overcurrent judgment value of the load L is determined by the above equation (b). When changing this judgment value, the variable resistor RV for adjusting the overcurrent judgment value is connected to the adjustment resistor connection terminal. The overcurrent determination value may be shifted downward by appropriately connecting to T3.

(B) Operation in the Ohmic Region When the power MOSFET QA is turned on by applying the charge pump output voltage VP from the drive circuit DR to the gate TG, the wiring from the DC power supply VB to the load L causes an abnormality such as a short circuit. In normal condition, power MO
Since the SFET QA is continuously turned on, the power MOS
The gate-source voltage VTGSA of the FET QA and the gate-source voltage VTGSB of the reference MOSFET QB each reach nearly 10 V, and both the power MOSFET QA and the reference MOSFET QB operate in the ohmic region.

During the operation in the ohmic region, there is no one-to-one relationship between the drain-source voltage VDS and the drain current ID of the MOSFET. For example, the power MOSFET QA and the reference MOSFET QA
When both B are constituted by HAF2001 manufactured by Hitachi, Ltd., since the ON resistance RDS (ON) of HAF2001 is 30 mΩ (when VDS = 10 V), the drain-source voltage VDSA of the power MOSFET QA and the reference The drain-source voltage VDSB of the MOSFET QB is as follows: VDSA = 5A × 30 mΩ = 0.15V) VDSB = I
DQA × 30 mΩ.

When the drain current IDQA of the power MOSFET QA increases due to a short circuit of the wiring from the DC power supply VB to the load L, the power MOSFET QA
QA drain-source voltage VDSA and reference MOSF
The difference between the ETQB and the drain-source voltage VDSB, that is, the value of VDSA-VDSB = 30 mΩ (IDQA-5A) (C) increases, and the value of (C) is determined by the above equation (B). If the current determination value is exceeded, the drive state of the power MOSFET QA is changed from on to off by the drive circuit DR.

Then, the operating state of the power MOSFET QA shifts from the ohmic region to the pinch-off region due to the transition of the driving state from on to off, and the power MOSFET QA repeats the on-off operation in this pinch-off region, eventually leading to overheat interruption.

However, for example, due to an intermittent short (rare short) from the DC power supply VB to the load L, the value of the above equation (c) exceeds the overcurrent determination value determined by the above equation (b). As in the case, if the state of the wiring returns to normal before the overheat interruption, the power MOSFET QA returns to the continuous ON state and returns to the operation in the ohmic region.

If it is assumed that the same value is used for the pinch-off region and the ohmic region for the overcurrent determination value determined by the above equation (b), ΔΔ in the pinch-off region
When (VDSA−VDSB) / ΔID is obtained, in the case of the above-mentioned HAF2001, from the characteristic curve, ΔVTGSA / ΔIDQA = 80 mV / A... (VDSA-VDSB) * 0.4 ...

Therefore, from the above equation and Δ (VDSA−VDSB) / ΔID in the pinch-off region, Δ (VDSA−VDSB) / ΔID = 200 mV / A (d), while Δ (VDSA−) in the ohmic region
From the above equation (C), VDSB) / ΔID becomes Δ (VDSA−VDSB) / ΔID = 30 mV / A (E).

As can be seen by comparing the above equations (d) and (e), the current sensitivity is more sensitive in the pinch-off region than in the ohmic region, and even if the overcurrent determination value is appropriate in the ohmic region, the current sensitivity is too low in the pinch-off region. There is a possibility that the current is determined too much.

Therefore, in the load power supply control IC 5, as described above, the resistors R3, R4, R6, R9,
MOSFET Q1, Q2 and Zener diode Z
A circuit comprising D2 is provided to change the overcurrent determination value related to the load L between the pinch-off region and the ohmic region. In this circuit, the determination as to whether the region is the pinch-off region or the ohmic region is made based on the gate-source voltage VTGSA of the power MOSFET QA. Perform in size.

More specifically, in the power MOSFET QA in the pinch-off region, the gate-source voltage VTGSA increases as the drain current IDQA increases. However, even if a dead short circuit occurs in the wiring from the DC power supply VB to the load L, the gate-source Voltage VTGS
Since A does not exceed 5 V, if VTGSA> 5 V, it can be determined that the current is in the ohmic region.

In the circuit for changing the overcurrent determination value, immediately after the drive state of the power MOSFET QA changes from off to on, the MOSFET Q1 is turned off and
Although the MOSFET Q2 is on, this MOSFET Q
In order to turn on the power supply 2, a power supply voltage higher than the DC power supply VB is required. Therefore, a power supply VB + 5 V, which is 5 V higher than the DC power supply VB, is connected to the gate of the MOSFET Q <b> 2.

In this circuit, the Zener voltage of the Zener diode ZD2 is 5 V which is a threshold value for the gate-source voltage VTGSA of the power MOSFET QA.
To the threshold voltage of the MOSFET Q1.
It is set to 5V-1.6V after subtracting 6V.

Therefore, in this circuit, the power MOS
When the gate-source voltage VTGSA of the FET QA exceeds 5 V, the MOSFET Q1 turns on and the MOSFET Q2
Is turned off, the resistor R3 in parallel with the resistor R2 is removed in a circuit manner, and the compression ratio of the drain-source voltage VDSA of the power MOSFET QA decreases, so that an overcurrent state occurs in the load L. Power MOSF to be determined
The difference (VDSA-VDSB) between the drain-source voltage of the ETQA and the reference MOSFET QB becomes smaller.

The presence of the circuit for changing the overcurrent determination value makes it possible to reduce the overcurrent judgment value as compared with the case where such a circuit does not exist.
Since the overcurrent is determined with a smaller current value in the ohmic region than in the pinch-off region, even if the current sensitivity is more sensitive in the pinch-off region than in the ohmic region, appropriate overcurrent determination in the ohmic region Only by setting the value, the overcurrent can be properly determined even in the pinch-off region.

However, the above-described circuit for changing the overcurrent determination value may not be used in some cases, that is, when the final load current value is large.

That is, if the final load current value is small, the drain current IDQA of the power MOSFET QA after ON driving
Completely rises in the pinch-off region, but if the final load current value is large, the power MOSFET
The drain current IDQA of the ETQA does not completely rise in the pinch-off region and is on its way. Therefore, the power MOSFET QA in the pinch-off region
Of the drain current IDQA of the
Even in the case of a dead short where the value of QA is the largest, it is limited to MAX40A.

That is, the power MOSFET after ON driving
As the final load current value increases, the drain current IDQA of the QA converges to a current rising curve having a certain gradient, and the difference in the final load current value indicates the power MOQ.
Since the difference in the voltage VDSA between the drain and the source of the SFET QA cannot be determined, it is determined that an overcurrent state has occurred in the load L even if the current sensitivity in the pinch-off region is large. The voltage difference (VDSA-VDSB) does not increase, and therefore, it becomes practical without using the above circuit, depending on the selection of the resistance value of the reference current Rr.

The load power supply control IC 5 having the configuration and the basic operation described above is different from the determination device of the first embodiment shown in FIG. 1 in that the first and second reference MOSFETs QB and Q
B 'and first and second reference resistance connection terminals T4, T4', and first and second comparators CP, CP 'and first and second signal output terminals T6, T6'. Have.

The voltage VDSA between the drain and source of the power MOSFET QA is divided and input to the positive-phase input terminal of the first comparator CP by the parallel resistance of the resistors R1 and R3 and the resistor R2. The drain-source voltage VDSB of the first reference MOSFET QB is input to the negative-phase input terminal of the first comparator CP, and the second comparator CP '
, A drain-source voltage VDSA of the power MOSFET QA is divided by a parallel resistor of the resistors R1 and R3 and the resistor R2, and is inputted to the second comparator CP '. The terminal is connected to the second reference MOSF
Drain-source voltage VDSB 'of ETQB is input.

Further, in the determination device of the first embodiment, the battery 1 is connected to the power connection terminal T1, and the load connection terminal T2
Is connected to a traveling sensor S via a normally closed relay RLY1, and first and second reference resistance connection terminals T4, T4
4 'is connected to a reference resistance circuit section 7, and a signal input terminal T
The microcomputer 9 is connected to the fifth and first and second signal output terminals T6 and T6 '.

The relay RLY1 is for interrupting the power supply path from the battery 1 to the travel sensor S as required. Usually, the common contact c and the closed contact a are connected, and the coil d is energized. Is performed, the common contact c is connected to the open contact b.

The reference resistor circuit section 7 has two reference resistors Rr1 and Rr2 (resistance value Rr1> Rr2), and one end of the reference resistor Rr1 is connected to a first reference resistor connection terminal of the load power supply control IC5. T4, one end of the reference resistor Rr2 is connected to the second reference resistor connection terminal T4 'of the load power supply control IC 5,
The other ends of the reference resistors Rr1 and Rr2 are both grounded.

The resistance value of the reference resistor Rr1 is the same as the drain-source voltage VDSA of the power MOSFET QA which occurs when the power MOSFET QA is turned on and the current flowing through the travel sensor S has a maximum value in normal operation. When the voltage is the first reference MOSFET Q
The value is set to a value generated between the drain and the source when B is turned on.

The resistance value of the reference resistor Rr2 is the same as the drain-source voltage VDSA of the power MOSFET QA that occurs when the power MOSFET QA is turned on and the current flowing through the traveling sensor S becomes a normal minimum value. When the voltage is the second reference MOSFET Q
The value is set to a value generated between the drain and the source at the time of driving B 'on.

Therefore, the reference resistance Rr1 is used for determining the short-circuit state of the travel sensor S, and the reference resistance Rr1 is used for determining the disconnection state of the travel sensor S.

The microcomputer 9 is constituted by a so-called one-chip microcomputer in which a CPU, a RAM, and a ROM are mounted on one chip, and an output port Out1 of the CPU is provided with a signal input of the load power supply control IC5. The terminal T5 is connected to the output port Out of the CPU.
2, the coil d of the relay RLY1 is connected.

The input ports In1, In2 of the CPU
Are connected to the first and second signal output terminals T6 and T6 'of the load power supply control IC 5, respectively, and the travel sensor S is connected to the input port In3 of the CPU.

Further, a nonvolatile memory 11 is connected to the input port In4 and the output port Out3 of the CPU, and the input port In5 and the output port Out4 of the CPU are connected.
The interface 13 for connecting the diagnostic tester 15
Is connected.

Next, the processing performed by the CPU according to the control program stored in the ROM of the microcomputer 9 will be described with reference to the flowchart of FIG.

When power is supplied from the battery 1 via a dark current power supply (not shown) and the microcomputer 9 is started, the CPU first sets both outputs of the output ports Out1 and Out2 to "L" and provides the outputs to the RAM. Initial setting for setting the flags of the various flag areas to "0" is performed (step S1).

When the initial setting of step S1 is completed,
Next, the potential of the output port Out1 is changed from “H” to “L”, and a signal for instructing ON of the power MOSFET QA and the first and second reference MOSFETs QB and QB ′ is sent to the load power supply control IC 5. (Step S3), and based on whether the potential of the input port In1 is “H” or not, the load power supply control IC 5
It is confirmed whether or not the short-circuit determination signal is input from the first signal output terminal T6 (step S5).

If the short-circuit determination signal has not been input (N in step S5), the process proceeds to step S11 described later, and if it has been input (Y in step S5), the potential of the output port Out1 is changed from "L". "H", the power MOSFET QA and the first and second reference
A signal instructing the SFETs QB and QB 'to be turned off is output to the signal input terminal T5 of the load power supply control IC 5 (step S7), and the flag F1 in the short-circuit flag area of the RAM is set to "1" (step S7). S9), and proceed to step S23 described below.

In step S11, where the short-circuit determination signal is not input in step S5 (N), in step S11, the load power supply control IC 5 is controlled based on whether or not the potential of the input port In2 is "H". Of the second signal output terminal T
It is checked whether or not the disconnection determination signal from 6 'has been input. If it has not been input (N in step S11),
The process proceeds to step S17 described below.

On the other hand, if the disconnection determination signal is input (Y in step S11), the potential of the output port Out1 is changed from "L" to "H" to change the power MOSFET.
QA and a signal instructing off driving of the first and second reference MOSFETs QB and QB 'are supplied to the load power supply control IC 5.
Is output to the signal input terminal T5 (step S13).
After setting the flag F3 of the M disconnection flag area to "1" (step S15), the process proceeds to step S23.

Further, if no disconnection determination signal is input in step S11, the process proceeds to step S1 (N).
At 7, it is confirmed whether or not both the short-circuit flag F1 and the disconnection flag F3 are "0". If both are "0" (Y in step S17), step S25 to be described later is performed.
Proceed to.

On the other hand, if at least one of the short-circuit flag F1 and the disconnection flag F3 is not “0” (N in step S17), the short-circuit flag F1 and the disconnection flag F
3 is set to "0" (step S19), the potential of the output port Out1 is changed from "H" to "L", and the power MOSFET QA and the first and second reference MOSFETs QB, After outputting a signal for instructing ON drive with QB 'to the signal input terminal T5 of the load power supply control IC 5 (step S21), step S2 is performed.
Go to 5.

In step S9, the short-circuit flag F
In step S23, which proceeds after setting 1 to "1" and after setting the disconnection flag F3 to "1" in step S15, the potential of the output port Out2 is changed from "L" to "H". Then, a signal for instructing interruption of the power supply path from the battery 1 to the travel sensor S is output to the coil d of the relay RLY, and then the process proceeds to step S25.

If both the short-circuit flag F1 and the disconnection flag F3 are "0" in step S17 (Y),
In step S21, the power MOSFET QA and the first
After outputting the ON drive instruction signal to the second reference MOSFETs QB and QB 'and changing the potential of the output port Out2 from "L" to "H" in step S23, the process proceeds to step S25 where the RAM is used. After the diagnostic data is generated based on the state of the short-circuit flag F1 and the disconnection flag F3, the diagnostic data stored in the nonvolatile memory 11 is updated to the diagnostic data generated in step S25 (step S27). Step S5
Return to

As is clear from the above description, in the first embodiment, step S in the flowchart of FIG.
Step 25 corresponds to the determination content data generating means in the claims, and step S27 in FIG. 3 corresponds to the determination content data storage executing means in the claims.

In the schematic circuit diagram shown in FIG. 1, for simplification of the drawing, the configuration of the internal circuit of the load power supply control IC 5 is omitted from the detailed circuit diagram of FIG.

Next, the operation (operation) of the determination device of the first embodiment configured as described above will be described.

In the determination device of the first embodiment, the microcomputer 9
Starts, the travel sensor S for the drive circuit DR connected to the signal input terminal T5 of the load power supply control IC5.
A signal instructing driving of the vehicle is output, and the travel sensor S connected to the load connection terminal T2 of the load power supply control IC 5 is output.
Changes from a state where it is not input to the drive circuit DR to a state where it is input.

Therefore, the power MOSFET QA, the first and second power MOSFETs QA and the first and second MOSFETs are controlled by the charge pump output voltage VP applied from the drive circuit DR of the load power supply control IC 5 to the gate TG of the power MOSFET QA and the first and second reference MOSFETs QB and QB '. Second reference MOSFET Q
B and QB 'are turned on, and the power MOSFET QA
Power is supplied from the battery 1 to the travel sensor S via the.

When the power supply path from the battery 1 to the travel sensor S is formed, the first comparator CP of the load power supply control IC 5 receives a signal between the drain and source of the power MOSFET QA which is input to the positive phase input terminal. The value of (a) obtained by dividing the voltage VDSA is compared with the drain-source voltage VDSB of the first reference MOSFET QB input to the negative-phase input terminal. Similarly, the second comparator C
At P ', the value of (a) input to the positive-phase input terminal and the second reference MOSFE input to the negative-phase input terminal
A comparison is made with the drain-source voltage VDSB of TQB '.

Here, if there is no particular abnormality on the power supply path from the battery 1 to the travel sensor S, the current flowing through the travel sensor S falls within a normal range, so that the first and second comparators CP, The value of (a) obtained by dividing the voltage VDSA between the drain and the source of the power MOSFET QA, which is input to the positive-phase input terminal of the CP ', is equal to the value of the first comparator C
The first reference MOSFET Q input to the negative-phase input terminal of P
B, the drain-source voltage VDSB and the second comparator C
Second reference MOSFET input to the negative input terminal of P '
Both of them fall below the drain-source voltage VDSB of QB '.

Therefore, the first and second comparators CP,
Both outputs of CP 'become "L", whereby the drive circuit DR continues to apply the charge pump output voltage VP to the power MOSFET QA and the gates TG of the first and second reference MOSFETs QB and QB', and the power MO
SFET QA and first and second reference MOSFETs QB, Q
B 'continues to be driven ON, and therefore, the travel sensor S from the battery 1 via the power MOSFET QA.
Continues to be powered.

The first and second comparators CP, C
Since the outputs of P 'are both "L", the first and second signal output terminals T6, T
Neither the short-circuit determination signal nor the disconnection determination signal is input to the CPU of the microcomputer 9 having the input ports In1 and In2 connected to 6 ', respectively. Therefore, at this timing, there is no abnormality in either the short-circuit or the disconnection. Is generated, and the diagnostic data is written and stored in the nonvolatile memory 11.

On the other hand, if a dead short (short circuit), rare short circuit, current leak, or the like occurs on the power supply path from the battery 1 to the travel sensor S, the current flowing through the travel sensor S becomes abnormally high even for a moment. Therefore, in the second comparator CP ′, the drain-source voltage VDSA of the power MOSFET QA input to the positive-phase input terminal
Is lower than the drain-source voltage VDSB of the second reference MOSFET QB 'input to the negative-phase input terminal, but in the first comparator CP, the value of (a) is input to the positive-phase input terminal. The value of (a) is higher than the drain-source voltage VDSB of the first reference MOSFET QB input to the negative-phase input terminal.

Then, the output of the second comparator CP 'becomes "L".
However, the output of the first comparator CP changes from “L” to “H”, whereby the drive circuit DR outputs the power MOSFET.
The application of the charge pump output voltage VP to the gate TG of the TQA and the first and second reference MOSFETs QB and QB 'is stopped, and these are turned off, and the power MOSFET is turned off.
The supply of power from the battery 1 to the travel sensor S via the TQA is stopped.

When the supply of electric power from the battery 1 to the travel sensor S via the power MOSFET QA is stopped, the coil d of the relay RLY1 is energized, and the connection target of the common contact c is changed from the closed contact a to the open contact b. And the connection between the load connection terminal T2 and the travel sensor S is cut off.

Further, since the output of the first comparator CP is "H" and the output of the second comparator CP 'is "L", the CPU of the microcomputer 9 is provided with a load power supply control IC.
5 is input via the input port In1. The disconnection determination signal from the second signal output terminal T6 'of the load power supply control IC 5 is connected to the input port In2. Not entered via
At this timing, diagnostic data indicating that there is an abnormality in the short circuit and no abnormality in the disconnection is generated, and the diagnostic data is written and stored in the nonvolatile memory 11.

Further, if a disconnection occurs on the power supply path from the battery 1 to the travel sensor S, no current flows through the travel sensor S, so that in the first comparator CP, the above-mentioned signal inputted to the positive-phase input terminal is output. Although the value of (a) is lower than the drain-source voltage VDSB of the first reference MOSFET QB input to the negative-phase input terminal, in the second comparator CP ', the power MOSFET QA input to the positive-phase input terminal Drain-source voltage VDSA
Is higher than the drain-source voltage VDSB of the second reference MOSFET QB 'input to the negative-phase input terminal.

Then, the output of the first comparator CP changes to "L", but the output of the second comparator CP 'changes from "L" to "H", whereby the driving circuit DR outputs the power MOSFET.
The application of the charge pump output voltage VP to the gate TG of the TQA and the first and second reference MOSFETs QB and QB 'is stopped, and these are turned off, and the power MOSFET is turned off.
The supply of power from the battery 1 to the travel sensor S via the TQA is stopped.

When the supply of power from the battery 1 to the travel sensor S via the power MOSFET QA is stopped, the coil d of the relay RLY1 is energized, and the connection target of the common contact C is changed from the closed contact a to the open contact b. And the connection between the load connection terminal T2 and the travel sensor S is cut off.

Further, since the output of the first comparator CP is "L" and the output of the second comparator CP 'is "H", the CPU of the microcomputer 9 is provided with a load power supply control IC.
5, the disconnection determination signal from the second signal output terminal T6 'is input via the input port 1n2, but the short-circuit determination signal from the first signal output terminal T6 of the load power supply control IC 5 is connected to the input port In1. Not entered via
At this timing, diagnostic data indicating that there is no abnormality in the short circuit and abnormality in the disconnection is generated, and the diagnostic data is written and stored in the nonvolatile memory 11.

After the dead short (short), rare short, current leak, etc., which have occurred on the power supply path from the battery 1 to the travel sensor S due to repair, replacement of parts, etc. If the connection between the load connection terminal T2 and the travel sensor S is still cut off by the relay RLY, the apparent disconnection state continues, so that the operation of the return switch (not shown) causes the CPU of the microcomputer 9 to notify the CPU. The connection between the load connection terminal T2 and the travel sensor S is returned by stopping the energization of the coil d of the relay RLY1 by notifying the fact or restarting the microcomputer 9 or the like, and then restarting the processing. There is a need.

An abnormality such as a short-circuit or a disconnection on the power supply path from the battery 1 to the travel sensor S is eliminated by repair, replacement of parts, or the like.
When the processing by the PU is resumed, the load power supply control I
A signal instructing driving of the traveling sensor S to the driving circuit DR connected to the signal input terminal T5 of C5 is output, and accordingly, the power is controlled by the charge pump output voltage VP from the driving circuit DR of the load power supply control IC5. MOS
FET QA and first and second reference MOSFETs QB, Q
B ′ is turned on, and power is supplied from the battery 1 to the travel sensor S via the power MOSFET QA.

Then, the first of the load power supply control ICs 5
And in the second comparators CP and CP ', the value of (a) obtained by dividing the drain-source voltage VDSA of the power MOSFET QA, which is input to the positive-phase input terminal, and the negative-phase input terminal. First and second reference MOSFETs
Each of QB and QB 'is compared with the drain-source voltage VDSB.

At this timing, since there is no abnormality on the power supply path from the battery 1 to the travel sensor S, the current flowing through the travel sensor S falls within a normal range, and therefore, the first and second comparators CP, The value of (a) input to the positive-phase input terminal of CP ′ is the first comparator CP
Reference MOSFET QB input to the negative-phase input terminal of
Between the drain-source voltage VDSB and the second comparator C
Second reference MOSFET input to the negative input terminal of P '
Both of them fall below the drain-source voltage VDSB of QB '.

Therefore, the first and second comparators CP,
Both outputs of CP 'become "L", whereby the drive circuit DR continues to apply the charge pump output voltage VP to the power MOSFET QA and the gates TG of the first and second reference MOSFETs QB and QB', and the power MO
SFET QA and first and second reference MOSFETs QB, Q
B 'continues to be driven ON, and therefore, the travel sensor S from the battery 1 via the power MOSFET QA.
Will continue to be supplied with power.

The first and second comparators CP, C
Since the outputs of P 'are both "L", the first and second signal output terminals T6, T
Neither the short-circuit determination signal nor the disconnection determination signal is input to the CPU of the microcomputer 9 having the input ports In1 and In2 connected to 6 ', respectively. Therefore, at this timing, there is no abnormality in either the short-circuit or the disconnection. Is generated, and the diagnostic data is written and stored in the nonvolatile memory 11.

Although the detailed processing contents of the diagnostic data written and stored in the nonvolatile memory 11 are omitted in the flowchart of FIG. 3, the diagnostic tester 15 is connected to the interface 13 and the diagnostic tester 15 transmits the diagnostic data. By outputting the read request to the CPU of the microcomputer 9, the read request is read from the non-volatile memory 11 by the CPU and output to the diagnostic tester 15 via the interface 13.

As is clear from the above description, in the determination device of the first embodiment, the reference resistance Rr1 of the reference resistance circuit section 7 corresponds to the reference resistance whose resistance is set to the maximum current resistance. The reference resistance Rr2 of the reference resistance circuit 7 corresponds to a reference resistance whose resistance is set to the minimum current resistance.

Further, in the determination device of the first embodiment, a series circuit of the reference resistance Rr1 of the reference resistance circuit section 7 and the first reference MOSFET QB of the load power supply control IC 5 is replaced with one series circuit. In addition, a series circuit of the reference resistor Rr2 of the reference resistor circuit section 7 and the second reference MOSFET QB 'of the load power supply control IC 5 corresponds to another series circuit of the present invention. The circuit forms a reference circuit section in the claims, and the reference circuit section and the load power supply control I
The power MOSFET QA of C5 forms an energizing means in the claims.

Furthermore, in the determination device of the first embodiment, the first comparator CP corresponds to the short-circuit determination means in the claims, and the second comparator CP 'corresponds to the disconnection determination means in the claims. I have.

As described above, according to the determination device of the first embodiment, the power MOSFET QA provided on the power supply path from the battery 1 to the travel sensor S has the first and second reference M
OSFETs QB and QB 'are connected in parallel,
The two reference resistors Rr1, whose resistance values are set so that the maximum value and the minimum value of the normal current flowing through
Rr2 is set to the first and second reference MOSFETs QB and Q
B ', respectively, connected in series to the drain-source voltage of the power MOSFET QA according to the current actually flowing through the travel sensor S, and the maximum and minimum values of the normal current of the travel sensor S flowing through the reference resistors Rr1 and Rr2. First and second reference MOSFETs Q corresponding to equivalent currents, respectively.
The first and second comparators CP and CP 'compare the drain-source voltages of B and QB' with each other. On the basis of the comparison result, a short circuit or the like on the power supply path from the battery 1 to the travel sensor S is detected. It is configured to determine the occurrence of disconnection.

[0130] For this reason, in the case of a short circuit, if the current flowing through the traveling sensor S becomes abnormally high even for a moment, it can be detected and detected as a short circuit. Such as leaks
Instantaneous phenomena as well as stable and continuous phenomena can be reliably determined.

Further, according to the determination device of the first embodiment,
Since the state of the short circuit or disconnection in the power supply path from the battery 1 to the travel sensor S is written and stored in the non-volatile memory 11 as the diagnostic data, the short circuit of the power supply path including the rare short circuit and the leak of the current is prevented. Can be held in a state where the power is not erased even when the power supply from the battery 1 is cut off, and in a state where the power can be output to the diagnostic tester 15.

In the above-described first embodiment, as shown in FIG. 1, a circuit that only supplies power to the travel sensor S from the battery 1 and stops it is described as an example. Some of the loads include a motor for driving the pointer of the meter (not shown) and a power window motor.
In some cases, the direction of energization must be switched according to the situation.

Next, a description will be given, with reference to FIG. 4, of a determination apparatus according to a second embodiment of the present invention, which determines a power supply failure for a load whose power supply direction is switched.

FIG. 4 is a circuit diagram partially showing a schematic configuration of a judgment device according to a second embodiment of the present invention. The judgment device according to the second embodiment is used for driving a pointer in a meter (not shown). The following configuration is adopted for the motor indicated by reference numeral 3 in FIG.

That is, another power MOSFET QA 'is provided in a pair with the power MOSFET QA, and a switching M
OSFETs QC and QC 'are provided, and these ON / OFF driving states are set to the signal input terminal T5 of the load power supply control IC5.
a, active / reverse rotation drive signals of “L” active, which are switched and output in accordance with the drive direction of a pointer (not shown) from the CPU of the microcomputer 9 connected to each of T. By switching, the direction of supply of electric power from the battery 1 to the motor 3 is switched.

That is, in the determination device shown in FIG.
OSFET QA, QA 'and switching MOSFET QC, Q
C ′ constitutes a so-called H-bridge, and the drive circuit DR outputs power MOSFETs QA and QA ′ regardless of whether the CPU 9 of the microcomputer 9 outputs a forward or reverse rotation drive signal.
, A charge pump output voltage VP is output.

However, when a positive rotation drive signal from the CPU of the microcomputer 9 is input to the signal input terminal T5a of the load power supply control IC 5, the signal input terminal T5a goes to "L" level, and the drive circuit DR and power MOSFET
Multiplexer MPX interposed between gate of QA
1 is turned on.

When a forward rotation drive signal is input to the signal input terminal T5a, the signal input terminal T5b, to which no reverse rotation drive signal is input from the CPU of the microcomputer 9, remains at "H" level. , Drive circuit DR and power MOS
The multiplexer MPX2 interposed between the gate of the FET QA 'is turned off.

Therefore, the charge pump output voltage VP when the positive rotation drive signal is input to the signal input terminal T5a of the load power supply control IC 5 is equal to the power MOSFET Q
The gate of A 'is cut off by the multiplexer MPX2 and is not applied, and is applied only to the gate of the power MOSFET QA via the multiplexer MPX1.

In conjunction with this, the potential of the signal input terminal T5a at "L" level is inverted by the inverting circuit INV1, and the switching MOSFET QC 'having its gate connected to the inverting circuit INV1 is turned on. At the same time, the potential of the signal input terminal T5b that has become “H” level is inverted by the inverting circuit INV2, and
The switching MOSFET QC whose gate is connected to V2 is driven off.

Therefore, when a forward rotation drive signal from the CPU of the microcomputer 9 is input to the signal input terminal T5a of the load power supply control IC 5, the battery 1 → power MO
Electric power from the battery 1 is supplied to the motor 3 through the path of SFET QA → motor 3 → switching MOSFET QC ′, and the motor 3 is driven to rotate in the forward direction.

On the other hand, when the reverse rotation drive signal from the CPU of the microcomputer 9 is input to the signal input terminal T5b of the load power supply control IC 5, the signal input terminal T5b becomes "L" level without the signal input terminal T5b. Circuit DR and power MO
The multiplexer MPX2 interposed between the gate of the SFET QA 'and the gate of the SFET QA' is turned on.

When the reverse rotation drive signal is input to the signal input terminal T5b, the signal input terminal T5a without the input of the forward rotation drive signal from the CPU of the microcomputer 9 remains at "H" level. , Drive circuit DR and power MOS
The multiplexer MPX1 provided between the gate of the FET QA and the gate of the FET QA is turned off.

Therefore, the charge pump output voltage VP when the reverse rotation drive signal is input to the signal input terminal T5b of the load power supply control IC 5 becomes the power MOSFET Q
The gate of A is cut off by the multiplexer MPX1 and is not applied, but is applied only to the gate of the power MOSFET QA 'via the multiplexer MPX2.

In conjunction with this, the potential of the signal input terminal T5b at "L" level is inverted by the inverting circuit INV2, and the switching MOSFET QC whose gate is connected to the inverting circuit INV2 is turned on. Along with
The potential of the signal input terminal T5a that has become “H” level is inverted by the inverting circuit INV1, and this inverting circuit INV1
Is turned off.

Therefore, when the reverse rotation drive signal from the CPU of the microcomputer 9 is input to the signal input terminal T5b of the load power supply control IC 5, the battery 1 → power MO
Electric power from the battery 1 is supplied to the motor 3 through the path of SFET QA '→ motor 3 → switching MOSFET QC, and the motor 3 is driven to rotate in the window closing direction.

The drain of the power MOSFET QA and the power MOSFET Q are connected to the positive-phase input terminal of the comparator CP.
A 'and the drain of A'
Between the source and the drain of the FET QB, a CPU of the microcomputer 9 is connected to a signal input terminal T5a of the load power supply control IC5.
When the positive rotation drive signal is input from the
When a current equivalent to the current flowing between the source and the drain of the OSFET QA flows and a reverse rotation drive signal from the CPU of the microcomputer 9 is input to the signal input terminal T5b of the load power supply control IC 5, the power MOSFET Q
Since a current equivalent to the current flowing between the source and the drain of A 'flows, the motor 3 which is set by the resistance value of the reference resistance circuit unit 7 at the time of outputting both the forward rotation drive signal and the reverse rotation drive signal. Judgment of short circuit and disconnection,
The power cutoff operation according to the result is performed in the same manner as in the case of the power window device of the first embodiment.

In each of the first and second embodiments, the value of (a) obtained by dividing the drain-source voltage VDSA of the power MOSFET QA and the values of the first and second reference MOSFETs QB and QB ' Although the comparison with the drain-source voltage VDSB is performed by the load power supply control IC 5 in an analog manner, the comparison may be performed digitally on the logic of the processing performed by the CPU.

Further, in each of the first and second embodiments, the power MOSFET Q of the load power supply control IC 5 is formed on the same chip by the same process.
A and the first and second reference MOSFETs QB and QB 'may be formed on separate chips,
And the power MO as in the determination device of the second embodiment.
SFET QA and first and second reference MOSFETs QB,
If formed on the same chip as QB 'by the same process, the power MOSFET QA and the first and second reference
This is advantageous because the effects of temperature drift between the SFETs QB and QB ', variation between IC lots, and wiring inductance / resistance can be eliminated.

Further, in each of the first and second embodiments, the configuration for performing the disconnection determination in addition to the short-circuit determination including the rare short-circuit has been described as an example, but the configuration for disconnection determination is omitted. Similarly, in each of the first and second embodiments, the diagnosis data is stored in the nonvolatile memory 11.
Is provided, but this configuration may be omitted.

However, the structure for performing the disconnection determination is the first and second configurations.
Is advantageous in that not only short-circuits but also disconnections can be determined, and important monitoring items on the power supply path can be almost covered. If the configuration for storing in the memory 11 is provided as in each of the first and second embodiments, the data that can be collected by connecting the existing diagnostic tester 15 includes data such as a short circuit and a disconnection on the power supply path. This is advantageous because it can be provided with higher precision than before.

The diagnostic data to be stored in the nonvolatile memory 11 is not limited to the latest data as in the first and second embodiments, but is also determined for a short period or disconnection for a predetermined period or number of times. The result history may be used.

According to each of the first and second embodiments, the first and second reference MOSFETs Q having a smaller MOSFET number ratio (current ratio) than the power MOSFET QA.
Since the reference circuit is configured using B and QB ', the required function can be realized with a small circuit size and a small chip occupation area.

In each of the first and second embodiments, the case where the short-circuit or the disconnection in the power supply path of the vehicle is determined has been described as an example. It is needless to say that the present invention can be widely applied to other electric crystallization and the like.

[0155]

According to the present invention as described above, according to the present invention, there is provided an apparatus for judging an improper conduction of a load connected to a power supply via an energizing means. A power supply means is connected in series between the power supply and the load, a power MOSFET for turning on and off the connection of the load to the power supply, and a reference connected in parallel with a series circuit of the power MOSFET and the load. A circuit section, wherein the reference circuit section includes the power MOSF.
A series circuit of a reference MOSFET and a reference resistor equivalent to ET, and a resistance value of the reference resistor is a reference current equivalent to a maximum value of a current normally flowing to the load.
The maximum current resistance value flowing between the drain and source of the SFET is set, and the power MOSFET drain-
A short-circuit determining unit that determines a short-circuit state in the energizing unit and the load based on a difference between a source-to-source voltage and a drain-source voltage of the reference MOSFET, wherein the short-circuit determining unit includes the energizing unit and the short-circuit determining unit. The configuration is such that a determination signal having contents corresponding to the determination result of the short circuit state in the load is output.

For this reason, even if it is an instantaneous one such as a rare short circuit, a short circuit in the energizing means can be determined with high accuracy without fail as an energizing failure.
Power MOSFET drain-source voltage and reference MO
Based on the difference between the drain-source voltage of the SFET and the short-circuit, the current-carrying failure related to the short-circuit is determined based on the drain-source voltage of the power MOSFET and a reference M equivalent to the power MOSFET.
Since the differential determination is made based on the drain-source voltage of the OSFET, it is possible to eliminate the common-mode error factor and improve the accuracy of the determination of the short-circuit conduction failure.

Further, according to the present invention, in the current supply failure judging device according to the first aspect, the reference circuit section may be configured to include the reference MO.
A plurality of series circuits including an SFET and the reference resistor, wherein a resistance value of the reference resistor in one of the plurality of series circuits is set to the maximum current resistance value; The resistance value of the reference resistor in the other one of the series circuits has a reference current equivalent to the minimum value of the current that normally flows through the load, and the reference current between the drain and the source of the reference MOSFET in the other one of the series circuits. The short-circuit determination means is configured to set the minimum current resistance value to flow and the reference MOSFET in the one series circuit with the power MOSFET drain-source voltage.
Based on the difference between the drain-source voltage of ET and the short-circuit state in the energizing means and the load, the drain-source voltage of the power MOSFET and the drain-source voltage of the reference MOSFET in the other one series circuit are determined.
A disconnection determining unit that determines a disconnection state in the energizing unit and the load based on a difference between the source-to-source voltages, wherein the disconnection determining unit responds to a determination result of the disconnection state in the energizing unit and the load. The configuration is such that a content determination signal is output.

Therefore, not only a short-circuit but also a disconnection can be determined with high accuracy as an energizing failure in the energizing means.
T drain-source voltage and the power MOSFET
Since the differential determination is made based on the drain-source voltage of the reference MOSFET equivalent to T, it is possible to eliminate the common-mode error factor and improve the accuracy of determining the current-carrying failure related to the disconnection.

Further, according to the present invention, in the current supply failure judging device according to the first or second aspect of the present invention, the judgment representing the content of the output judgment signal is provided. A configuration further includes a determination content data generating unit that generates data, and a determination content data storage executing unit that stores the determination data generated by the determination content data generation unit in a non-volatile storage unit in a readable manner.

For this reason, it is possible to hold the judgment data relating to the energization failure of the energization means so as to be readable from the outside, and to keep the judgment data even after the power supply is cut off.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the reference MOSFET is provided.
T is constituted by a smaller number of MOSFETs than the MOSFETs constituting the power MOSFET, and the resistance value of the reference resistor is calculated by: the resistance value of the load × (the number of MOSFETs constituting the power MOSFET / the reference MOSFET (The number of MOSFETs to be configured).

For this reason, M constituting the reference MOSFET
The number of OSFETs is used to configure the power MOSFET
Since the number of FETs can be reduced, the circuit scale of the reference circuit can be reduced.

Further, according to the present invention, in the current supply failure judging device according to the first, second, third or fourth aspect, the reference MO
Since the SFET is formed in the same chip as the power MOSFET, it is possible to reduce or eliminate the influence of inter-individual errors such as temperature drift and lot-to-lot variation.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing, in partial blocks, a configuration of a vehicle conduction failure determination device according to a first embodiment of the present invention.

FIG. 2 is a detailed circuit diagram of the load power supply control IC of FIG. 1;

FIG. 3 is a flowchart showing a process performed by a CPU according to a control program stored in a ROM of the microcomputer of FIG. 1;

FIG. 4 is a schematic circuit diagram showing, in partial blocks, a configuration of a vehicle conduction failure determination device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an example of a short-circuit and disconnection detection device according to a conventional example.

[Explanation of symbols]

Reference Signs List 1 battery (power supply) 3 motor (load) 5 load power supply control IC 9 microcomputer (judgment data generation means,
Judgment content data storage execution means) 11 Non-volatile memory (Non-volatile storage means) CP comparator (short circuit judgment means) CP 'comparator (disconnection judgment means) DSW dummy switch (normally open contact, reference resistance section) DR drive circuit ( Gate voltage control means) QA Power MOSFET (Electrification means) QB First reference MOSFET (Electrification means, reference circuit part) QB 'Second reference MOSFET (Electrification means, reference circuit part) Rr1, Rr2 Reference resistance (Reference resistance, Reference circuit) Part) S Travel sensor (load)

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H03K 17/08 H03K 17/08 CF term (reference) 2G014 AA02 AA03 AA16 AB07 AB20 AB24 AB38 AC19 2G035 AA11 AA12 AB03 AC15 AD02 AD03 AD04 AD10 AD13 AD23 AD26 AD28 AD44 5G004 AA04 AB02 BA03 BA04 BA05 DA02 DA04 DC14 EA01 GA02 5J055 AX31 AX36 BX16 CX28 DX13 DX15 DX17 DX22 DX53 DX54 DX60 DX73 EX04 EX06 EX11 EX23 EY01 EY03 EY05 EY13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ13 EZ30 FX05 FX07 FX38 GX01 GX03

Claims (5)

[Claims] 1. An apparatus for judging a power supply failure of a load connected to a power supply via a power supply means, wherein the power supply means is connected in series between the power supply and the load, A power MOSFET for turning on / off a connection to a power supply; and a reference circuit unit connected in parallel with a series circuit of the power MOSFET and the load, wherein the reference circuit unit is a reference MOSFET equivalent to the power MOSFET. And a series circuit of a reference resistor, wherein the resistance value of the reference resistor is a maximum current resistance value at which a reference current equivalent to a maximum value of a current normally flowing to the load flows between a drain and a source of the reference MOSFET. The current supply means based on a difference between a drain-source voltage of the power MOSFET and a drain-source voltage of the reference MOSFET. And a short-circuit judging means for judging a short-circuit state in the load, wherein the short-circuit judging means outputs a judgment signal having a content according to the judgment result of the short-circuit state in the energizing means and the load. Energization failure determination device. 2. The reference circuit section includes a reference MOSFET.
And a plurality of series circuits of the reference resistor, wherein the resistance value of the reference resistor in one series circuit of the plurality of series circuits is set to the maximum current resistance value. The resistance value of the reference resistor in the other one of the series circuits is such that a reference current equivalent to the minimum value of the current that normally flows through the load flows between the drain and the source of the reference MOSFET in the other one of the series circuits. The short-circuit determination means is set to a minimum current resistance value, and the short-circuit determination means is configured to determine the short-circuit determination means based on a difference between the drain-source voltage of the power MOSFET and the drain-source voltage of the reference MOSFET in the one series circuit. And a short-circuit state in the load is determined.
Disconnection determining means for determining a disconnection state in the energizing means and the load based on a difference between an FET drain-source voltage and a drain-source voltage of the reference MOSFET in the another one of the series circuits, 2. The current-carrying failure judging device according to claim 1, wherein the disconnection judging means outputs a judgment signal having a content according to a judgment result of a disconnection state in the energizing means and the load. 3. A determination content data generating means for generating determination data representing the content of the output determination signal, and the determination data generated by the determination content data generating means are readablely stored in a non-volatile storage means. 3. The energization failure determination device according to claim 1, further comprising: a determination content data storage execution unit that causes the determination to be performed. 4. The power MOSFET according to claim 1, wherein the reference MOSFET is
A smaller number of MOs than the MOSFETs that make up the SFET
2. The resistance value of the reference resistor is set to (resistance value of the load × (number of MOSFETs configuring the power MOSFET / number of MOSFETs configuring the reference MOSFET)). , 2
Or the energization failure determination device according to 3. 5. The power MOSFET according to claim 1, wherein the reference MOSFET is
Claim 1 wherein the SFET and the SFET are formed in the same chip.
5. The energization failure determination device according to 2, 3, or 4.