JPH07337092A - Constant current controller with abnormality diagnostic function - Google Patents

Abstract

PURPOSE:To diagnose a current sensor and an overcurrent sensor by detecting a current flowing upon simultaneous turn ON of two switching elements connected in series before starting the current control using four switching elements forming an H bridge in a constant current controller. CONSTITUTION:The microcomputor 11 in a controller comprises a CPU 11b, a memory 11c, I/O interfaces 11d, 11e, and an A/D converter 11f disposed around a bus 11a. A drive circuit 14a comprises switching elements 14a1-4 connected in bridge and a drive logic 14a5. Phase A drive coil 12a is connected between a pair of joints of the bridge having the other pair of joints connected with a power supply bus 16 and the earth. A shunt resistor 13a1 for current detection and an overcurrent sensor 15 are connected between the bridge and the power supply bus 16. The voltage across the shunt resistor 13a1 is connected through a butter amplifier 13a2 with the A/D converter 11f.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current controller, and more particularly to a constant current controller having an abnormality diagnosing function.

[0002]

2. Description of the Related Art A so-called constant current control device for controlling a current flowing through a load to a predetermined current set value is widely applied as, for example, a drive control device for a stepping motor. As this constant current control device, there are a device that performs feedback control by measuring an actual load current, a device that performs on / off control of a switching element at a duty ratio that is predetermined corresponding to a current setting value, etc. In general, a microcomputer system is generally applied as a control device.

Further, a current sensor for actually detecting the current flowing through the load and an overcurrent sensor for cutting off the power supply to the load when the current flowing through the load becomes excessive are installed.

[0004]

However, when the detection characteristics of the current sensor deviate due to aging, not only the constant current control cannot be performed accurately, but also the detection characteristics of the overcurrent sensor deviate due to aging. If this happens, the hardware of the device may be damaged. The present invention has been made in view of the above problems, and an object thereof is to provide a constant current control device in which a so-called abnormality diagnosis function is added to the control device.

[0005]

In the constant current control device according to the first invention, four switching elements are connected in a bridge shape, and a load is connected to one diagonal and a power source and a ground are connected to the other diagonal. H bridge, and a current detection unit installed between the H bridge and the power supply for detecting a load current,
Overcurrent detection means installed between the H-bridge and the power supply for detecting that the current flowing through the load has exceeded a predetermined maximum current, and four switching elements of the H-bridge are provided with a current supply direction and current value to the load. And a load current detected by the current detecting means by simultaneously turning on the two switching elements connected in series before the constant current control by the four switching elements of the H-bridge is turned on. When the difference from the predetermined calibration current is equal to or larger than the predetermined difference, it is determined that the current detection means is abnormal, and when the overcurrent detection means does not detect the overcurrent, the overcurrent detection means is abnormal. An abnormality determining means for determining is provided.

The constant current control device according to the second invention is 4
An H bridge in which two switching elements are connected in a bridge shape and a load is connected to one diagonal and a power supply and a ground are connected to the other diagonal, and a current installed between the H bridge and the power supply to detect a load current The detection means, the control means for controlling the on / off state of the four switching elements of the H-bridge according to the current supply direction to the load and the current value, and the predetermined constant current control before the constant current control by the four switching elements of the H-bridge are started. The current detection characteristic correction means for driving the switching element at the standard frequency and the standard duty ratio to determine the detection characteristic value of the current detection means based on the load current detected by the current detection means, and the control means for detecting the current On / off control is performed based on the detection characteristic value of the current detection means determined by the characteristic correction means.

In the constant current control device according to the third aspect of the present invention, the control means changes the detection characteristic value of the current detection means determined by the current detection characteristic correction means according to the power supply voltage. A constant current control device according to a fourth aspect of the present invention is a load current detected by the current detection means when the current detection characteristic correction means drives the switching element at a predetermined standard frequency and standard duty ratio, and the standard frequency and standard. A current detection abnormality determination means for determining that the current detection means is abnormal when the difference from the standard current predicted to flow when the switching element is driven at the duty ratio is equal to or greater than a predetermined current threshold value. To do.

In the constant current control device according to the fifth aspect of the present invention, the current detection abnormality determination means changes the current threshold value according to the power supply voltage. The constant current control device according to the sixth invention is 4
An H bridge in which two switching elements are connected in a bridge shape and a load is connected to one diagonal and a power supply and a ground are connected to the other diagonal, and a current installed between the H bridge and the power supply to detect a load current Detecting means, control means for controlling the on / off state of the four switching elements of the H bridge according to the current supply direction to the load and the current value, and current detecting means before the start of constant current control by the four switching elements of the H bridge. The ON / OFF time of the switching element is measured when the load current detected by the load current is controlled to a predetermined reference current setting value, and the difference between this ON / OFF time and a predetermined standard ON / OFF time is greater than or equal to a predetermined time threshold value. A current detection abnormality determining means for determining that the current detecting means is abnormal at times is provided.

In the constant current control device according to the seventh aspect of the present invention, the current detection abnormality determination means changes the time threshold value according to the power supply voltage. The constant current control device according to the eighth invention is 4
An H bridge in which two switching elements are connected in a bridge shape and a load is connected to one diagonal and a power supply and a ground are connected to the other diagonal, and a current installed between the H bridge and the power supply to detect a load current Detecting means, control means for controlling the on / off state of the four switching elements of the H bridge according to the current supply direction to the load and the current value, and current detecting means before the start of constant current control by the four switching elements of the H bridge. The ON / OFF time of the switching element when the load current detected by the control is controlled to a predetermined reference current setting value is stored as the standard ON / OFF time. When the difference between the two is greater than or equal to a predetermined time threshold value, it is determined that the current detection means is abnormal. Comprising means.

In the constant current control device according to the ninth aspect of the present invention, the current detection abnormality determining means changes the time threshold value according to the power supply voltage. A constant current control device according to a tenth invention is
The current detection abnormality determining means controls the on / off time of the switching element when the load current detected by the current detecting means is controlled to the specific reference current setting value before the constant current control by the four switching elements of the H-bridge is started. A reference other than the specific reference current set value determined based on the on / off time and the specific standard on / off time at the reference current set value other than the specific reference current set value after the constant current control by the four switching elements of the H bridge is started. When the difference between the set current value and the standard on / off time is equal to or greater than a predetermined time threshold value, it is determined that the current detection means is abnormal.

A constant current controller according to the eleventh invention is
The current detection abnormality determination means changes the time threshold value according to the power supply voltage.

[0012]

In the constant current control device according to the first aspect of the present invention, it is diagnosed whether or not the current sensor and the overcurrent sensor are normal before the control is started. In the constant current control device according to the second and fourth aspects, it is diagnosed whether or not the current sensor is normal before the control is started.

In the constant current control device according to the third and fifth aspects of the invention, the threshold value for determining whether or not the current sensor is normal is corrected according to the power supply voltage. In the constant current control device according to the sixth aspect of the present invention, the device diagnosis is performed depending on whether the ON time and the OFF time of the switching element when the current is controlled to a predetermined current before the control is started are deviated from the reference time. Be seen.

In the constant current control device according to the seventh aspect of the invention, the reference time is corrected according to the power supply voltage. In the constant current control device according to the eighth aspect of the present invention, the ON time and OFF time of the switching element when controlled to a predetermined current before the start of control, and the ON time and OFF time of the switching element during constant current control. The device is diagnosed based on whether or not the difference from

In the constant current control device according to the ninth aspect of the invention, the shift threshold value is corrected according to the power supply voltage.
In the constant current control device according to the tenth invention, the ON time and the OFF time of the switching element when the current is controlled to a predetermined current before the control is started for one specific current level, and the remaining time is measured. For the current level, the on time and off time of the switching element are determined based on a predetermined function.

In the constant current control device according to the eleventh aspect of the invention, the shift threshold value is corrected according to the power supply voltage.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram (only the phase A drive circuit is shown) of an embodiment of a stepping motor drive device to which a constant current control device according to the present invention is applied. The microcomputer 11, which is a control device, has a bus C as a center and a C
PU 11b, memory 11c, input interface 11
d, output interface 11e and A / D converter 1
It is composed of 1f.

The drive circuit 14a is composed of bridge-connected switching elements 14a1-4 and drive logic 14a5, and the A-phase drive coil 12a is connected to one diagonal of the bridge. The other diagonal of the bridge is connected to the power bus 16 and ground and the bridge and power bus 1
A shunt resistor 13a1 and an overcurrent sensor 15 for detecting the current flowing through the bridge are installed between the shunt resistor 6 and the switch 6.

The voltage generated across the shunt resistor 13a1 is supplied to the A / D converter 1 via the buffer amplifier 13a2.
It is connected to 1f. FIG. 2 is a flow chart of a first abnormality diagnosis routine executed by the microcomputer 11 in the first invention, which is executed only once before the start of the constant current control.

In step 21, the switching elements 14a1 and 14a3 are turned on to put them in a pseudo short circuit state. In step 22, a flag OC indicating whether the overcurrent sensor 15 has operated and the A / D converter 11
The load current I _L taken through f is read. In step 23, it is determined whether the flag OC is "1".

If a negative determination is made, it is determined that the overcurrent sensor 15 has not operated when it should have operated, that is, the overcurrent sensor 15 is abnormal, and step 2
In step 4, the overcurrent sensor abnormality flag AOC is set to "1" and the process proceeds to step 25. When an affirmative determination is made in step 23, it is determined that the overcurrent sensor 15 is normal, and the process directly proceeds to step 25.

In step 25, it is judged whether or not the load current I _L is _{equal to} or more than a predetermined maximum current I _MAX .
When a negative determination is made in step 25, a current equal to or larger than the maximum current I _MAX is not detected despite the overcurrent state, that is, the current sensor 13a including the shunt resistor 13a1 and the buffer amplifier 13a2 is abnormal. If it is determined that there is a current sensor abnormality flag A
CS is set to "1" and this routine is ended.

FIG. 3 is a flow chart of a second abnormality diagnosis routine executed by the microcomputer 11 in the second invention, which is executed only once before the start of the constant current control. In step 31, switching element 1
4a4 to the ON command, switching element 14a1
On the other hand, a pulse control signal having a constant frequency and a constant duty ratio (for example, a frequency of 10 kHz and a duty ratio of 30%) is output.

In step 32, the load current I _L is read. In step 33, the proportional constant k representing the detection characteristic of the current sensor 13a is calculated by the following equation. k = I _L / DR where DR is the duty ratio, which is 30% in this embodiment.

In the subsequent constant current control, this proportional constant k is used. It is common that the power supply voltage V _B differs during abnormality diagnosis and during constant current control.
Can be corrected according to the power supply voltage V _B. FIG. 4 is a flow chart of a third abnormality diagnosis routine executed by the microcomputer 11 in the fourth invention, which is executed only once before the start of the constant current control.

In step 41, an ON command is issued to the switching element 14a4,
For 1, the pulse control signal having a constant frequency and a constant duty ratio (for example, a frequency of 10 kHz and a duty ratio of 30%) is output. In step 42, the load current I _L is read. Standard current I when switching is performed at a constant frequency and a constant duty ratio with the load current I _L in step 43
It is determined whether or not the absolute value of the difference from _ST is greater than or equal to a predetermined current threshold value α.

If a positive determination is made in step 43, it is determined that the current sensor 13a is abnormal, the current sensor abnormality flag ACS is set to "1" in step 44, and this routine ends. When a negative determination is made in step 43, the current sensor 13a is determined to be normal, and this routine is ended directly.

It is also possible to correct the standard current I _{ST according} to the power supply voltage V _B. FIG. 5 is a graph for determining the standard current I _ST , where the horizontal axis represents the power supply voltage V _B and the vertical axis represents the standard current I _ST . That is, the standard current I _ST can be determined as a value proportional to the power supply voltage V _B.

FIG. 6 is a flow chart of a fourth abnormality diagnosis routine executed by the microcomputer 11 in the sixth invention, which is executed only once before the start of the constant current control. In step 61, the target current value I _d is set to a predetermined reference current target value I _dC .

The on-time measuring process is executed in step 62, the off-time measuring process is executed in step 63, and the process proceeds to step 64. On time T in step 64
Whether the deviation between _ON and the predetermined reference ON time T _ONC is greater than or equal to a predetermined ON time threshold τ _ON is determined in step 65 by the OFF time T _OFF and the predetermined reference ON time T _OFFC . Is determined to be _{equal to} or greater than a predetermined off time threshold value τ _OFF .

If an affirmative decision is made in either step 64 or step 65, the control unit determines that there is an abnormality, proceeds to step 66, sets an abnormality flag, and terminates this routine. When a negative determination is made in step 64 and step 65, the control device determines that it is normal and directly ends this routine.

The predetermined on-time threshold value τ_ONAnd oh
Time threshold τ_OFFPower supply voltage V _BAccording to
It is also possible. FIG. 7 shows the on-time threshold τ_ONDecide
And a power supply voltage V on the horizontal axis._BVertical
On-time threshold τ on axis_ON, But the on-time threshold
τ_ONIs the power supply voltage V_BTo be determined as a value that is inversely proportional to
You can

FIG. 8 is a graph for determining the off-time threshold value τ _OFF , where the horizontal axis is the power supply voltage V _B and the vertical axis is the off-time threshold value τ _OFF. Value τ
_OFF can be determined as a value proportional to the power supply voltage V _B. FIG. 9 shows step 62 of the fourth abnormality diagnosis routine.
6 is a flowchart of the on-time measuring process executed in step 621, in which the on-time timer T _ON is started.

In step 622, for example, a switching element
An ON command is output to 14a1, and in step 623
Load current I_LRead. In step 624, the load current I
_LIs the reference current target value I_dCIt is judged whether it is above,
If the fixed determination is made, the process returns to step 622. Step 624
If a positive determination is made at step 625, the on-time timer
Imma T _ONStop at step 626.
Imma T_ONThe count value of is stored, and this processing ends.

FIG. 10 is a flowchart of the off-time measuring process executed in step 63 of the fourth abnormality diagnosis routine.
Start _OFF . Switching element 1 in step 632
An off command is output to 4a1, and in step 633 the load current I _L is read.

In step 634, the load current I_LIs the reference current
Target value I_dCIs less than or equal to the value obtained by subtracting the predetermined value ΔI from
If it is determined negatively, the process returns to step 632.
If an affirmative decision is made in step 634, the operation proceeds to step 635.
Off time timer T _OFFStop and go to step 636
OFF time timer T_OFFThe count value of
End the reason.

FIG. 11 is a flow chart of a reference time measuring routine executed by the microcomputer 11 in the eighth invention, which is executed only once before the start of the constant current control. In step 111, the target current value I _d is set to a predetermined reference current target value I _dC .

In step 112, the standard on-time measuring process is executed to obtain the standard on-time T _ONS , and step 1
In 13, the reference off-time measuring process is executed to obtain the standard off-time T _OFFS , and this routine is ended. The standard on-time measurement process is the same as the on-time measurement process shown in FIG.
The standard off-time measuring process is the same as the off-time measuring process shown in FIG.

FIG. 12 is a flow chart of a constant current control routine executed by the microcomputer 11 in the eighth invention. In step 121, the target current value I
The _d, is set to current target value I _d1 corresponding to for example the level 1. The ON control process is executed in step 122, the OFF control process is executed in step 123, and step 12 is executed.
Go to 4.

In step 124, the on time T_ONAnd standard
Quasi on time T_ONSIs a predetermined on-time threshold τ
_ONWhether or not the above is determined at step 125 when off
Interval T _OFFAnd a standard on-time T predetermined_OFFSDeviation from
Is the predetermined off-time threshold τ _OFFIt is decided whether or not it is above
Set. One of the steps 124 or 125 is affirmative
If it is determined that the current sensor 13a is abnormal
And set the current sensor error flag ACS to "1".
Exit the routine.

No in steps 124 and 125
If it is determined that the current sensor 13a is normal,
Then, this routine is ended directly. The ON control process is
The on-time measuring process and the off-control process shown in FIG.
This is the same processing as the off-time measurement processing shown in. Given
On-time threshold τ of_ONAnd the off-time threshold τ_OFF
Power supply voltage V _BIt is also possible to make corrections according to

In the eighth aspect of the invention, it is necessary to obtain the standard on-time and the standard off-time corresponding to the number of levels of the current set value, but the specific current target value corresponding to one specific current level. The specific on-time T _ONP and the specific off-time T _OFFP that are the on-time and the off-time for I _dP are obtained, and the on-time and the off-time other than the specific current level are determined to be the specific on-time T _ONP and the specific off-time T _OFFP.
It is also possible to make a decision based on

FIG. 13 shows the ON time T_ONTo determine
It is rough and the horizontal axis shows the current setting value I. _dIs on the vertical axis
Interval T_ONTake That is, the specific current target value I_dPCorresponding to
Constant on time T_ONPIf is found, the current setting value I_dAnd the function
Then on time T_ONCan be determined. 14
Is off time T_OFFIs a graph for determining
Current setting value I on axis_dIs the off time T on the vertical axis_OFFTake
Current setting value I_dOff-time T as a function of _OFFTo decide
It is also possible.

[0044]

According to the constant current control device of the first aspect of the present invention, the operational reliability of the constant current control device is improved by diagnosing whether the current sensor and the overcurrent sensor are normal before the control is started. It becomes possible to improve. According to the constant current control device according to the second and fourth aspects of the present invention, it is possible to improve the operational reliability of the constant current control device by diagnosing whether or not the current sensor is normal before starting control. Becomes

According to the constant current control device of the third and fifth aspects of the invention, the diagnostic accuracy is improved by correcting the threshold value for determining whether or not the current sensor is normal in accordance with the power supply voltage. It becomes possible to do. According to the constant current control device of the sixth aspect of the present invention, the device is diagnosed by whether or not the ON time and the OFF time of the switching element when the current is controlled to a predetermined current before the control is started are deviated from the reference time. This makes it possible to improve the operational reliability of the constant current control device.

According to the constant current controller of the seventh invention, the reference time is corrected according to the power supply voltage,
It is possible to improve the diagnostic accuracy. According to the constant current control device of the eighth invention, the on time and off time of the switching element when controlled to a predetermined current before the start of control, and the on time and off time of the switching element during constant current control. It is possible to improve the operational reliability of the constant current control device by diagnosing the device based on whether or not the difference between the two is deviated.

According to the constant current control device of the ninth aspect of the present invention, it is possible to improve the diagnostic accuracy by correcting the shift threshold value according to the power supply voltage. According to the constant current control device of the tenth aspect of the present invention, the on time and off time of the switching element when the current is controlled to a predetermined current before the control is started for one specific current level, and the remaining current is measured. For the level, it is possible to simplify the configuration by determining the on time and off time of the switching element based on a predetermined function.

In the constant current control device according to the eleventh aspect of the invention, it is possible to improve the diagnostic accuracy by correcting the shift threshold value according to the power supply voltage.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment.

FIG. 2 is a flowchart of a first abnormality diagnosis routine.

FIG. 3 is a flowchart of a second abnormality diagnosis routine.

FIG. 4 is a flowchart of a third abnormality diagnosis routine.

FIG. 5 is a graph for determining standard current.

FIG. 6 is a flowchart of a fourth abnormality diagnosis routine.

FIG. 7 is a graph for determining an on-time threshold.

FIG. 8 is a graph for determining an off-time threshold.

FIG. 9 is a flowchart of an on-time measurement process.

FIG. 10 is a flowchart of an off-time measuring process.

FIG. 11 is a flowchart of a reference time measurement routine.

FIG. 12 is a flowchart of a current control routine.

FIG. 13 is a graph for determining on-time.

FIG. 14 is a graph for determining the off time.

[Explanation of symbols]

 11 ... Microcomputer 12a ... Stepping motor drive coil 13a ... Current sensor 14a1-4 ... Switching element 14a5 ... Drive logic 15 ... Overcurrent sensor

Claims (11)

[Claims] 1. An H-bridge in which four switching elements are connected in a bridge shape, a load is connected to one diagonal and a power source and a ground are connected to the other diagonal, and between the H-bridge and the power source. And a current detecting unit that is installed between the H-bridge and the power source and that detects that the current flowing through the load is equal to or greater than a predetermined maximum current. A constant current control device comprising: a control means for controlling an ON / OFF state of four switching elements of the H bridge according to a current supply direction to a load and a current value, wherein constant current control by the four switching elements of the H bridge. Before starting, two switching elements connected in series are turned on at the same time, and a load current detected by the current detecting means and a predetermined calibration current are set. Abnormality determination that the current detection means is abnormal when the difference is equal to or more than a predetermined difference, and that the overcurrent detection means is abnormal when the overcurrent detection means does not detect the overcurrent A constant current control device further comprising means. 2. An H-bridge in which four switching elements are connected in a bridge shape, a load is connected to one diagonal and a power source and a ground are connected to the other diagonal, and between the H-bridge and the power source. Constant current control, which is installed in the vehicle and includes a current detection unit that detects a load current, and a control unit that controls an ON / OFF state of the four switching elements of the H-bridge according to a current supply direction to the load and a current value. In the device, before starting the constant current control by the four switching elements of the H-bridge, the switching elements are driven at a predetermined standard frequency and standard duty ratio, and the current is detected based on the load current detected by the current detection unit. The current detection characteristic correction means for determining the detection characteristic value of the detection means is further provided, and the control means corrects the current detection characteristic. Detection characteristic value constant current control is performed on-off control based on said current detection means which is determined by the stage. 3. The constant current control device according to claim 2, wherein the control unit changes the detection characteristic value of the current detection unit determined by the current detection characteristic correction unit according to a power supply voltage. 4. The switching element with the load current, the standard frequency and the standard duty ratio detected by the current detecting means when the current detection characteristic correcting means drives the switching element with a predetermined standard frequency and standard duty ratio. Is provided with a current detection abnormality determination means for determining that the current detection means is abnormal when the difference from the standard current expected to flow when driving is greater than or equal to a predetermined current threshold value. The constant current controller according to claim 2 or 3. 5. The constant current control device according to claim 2, wherein the current detection abnormality determination means changes the current threshold value according to the power supply voltage. 6. An H-bridge in which four switching elements are connected in a bridge shape, a load is connected to one diagonal and a power source and a ground are connected to the other diagonal, and between the H-bridge and the power source. Constant current control, which is installed in the vehicle and includes a current detection unit that detects a load current, and a control unit that controls an ON / OFF state of the four switching elements of the H-bridge according to a current supply direction to the load and a current value. In the device, before the start of constant current control by the four switching elements of the H-bridge, the on / off time of the switching elements when the load current detected by the current detection means is controlled to a predetermined reference current setting value is measured, When the difference between this on / off time and a predetermined standard on / off time is greater than or equal to a predetermined time threshold value, it is determined that the current detection means is abnormal. A constant current control device comprising a current detection abnormality determining means for 7. The constant current controller according to claim 6, wherein the current detection abnormality determination means changes the time threshold value according to the power supply voltage. 8. An H-bridge in which four switching elements are connected in a bridge shape, a load is connected to one diagonal and a power source and a ground are connected to the other diagonal, and between the H-bridge and the power source. Constant current control, which is installed in the vehicle and includes a current detection unit that detects a load current, and a control unit that controls an ON / OFF state of the four switching elements of the H-bridge according to a current supply direction to the load and a current value. In the device, the on / off time of the switching element when the load current detected by the current detecting means is controlled to a predetermined reference current setting value before the constant current control by the four switching elements of the H-bridge is started is a standard on / off time. After the constant current control by the four switching elements of the H-bridge is started, the difference between the on-off time and the standard on-off time becomes A constant current control device comprising a current detection abnormality determination means for determining that the current detection means is abnormal when the time is equal to or greater than a predetermined time threshold value. 9. The constant current controller according to claim 8, wherein the current detection abnormality determination means changes the time threshold value according to the power supply voltage. 10. The current detection abnormality determination means when the load current detected by the current detection means is controlled to a specific reference current set value before the constant current control by the four switching elements of the H bridge is started. The on / off time of the switching element is stored as a specific standard on / off time, and based on the on / off time and the specific standard on / off time at a reference current setting value other than the specific reference current setting value after the constant current control by the four switching elements of the H-bridge is started. The current detection means is determined to be abnormal when the difference from the standard on / off time in the reference current setting value other than the specific reference current setting value determined by the above is a predetermined time threshold value or more. 8. The constant current control device according to item 8. 11. The constant current controller according to claim 10, wherein the current detection abnormality determination means changes the time threshold value according to the power supply voltage.