JPH11122805A - Conduction controller and self-diagnostic method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen stress on a semiconductor switch while shortening the time required for failure diagnosis by shortening the conduction time and the conduction interval of the semiconductor switch. SOLUTION: Semiconductor switches S1, S2 constituting a switch circuit 4 are subjected to time division sequential conduction at a constant time interval for a time shorter than that required for an inrush current to reach an absolute maximum rated level at the time of conduction and the smoothed output voltage Vm from a DC motor is compared with a threshold level when a specified number of conduction times us reached. If it is lower than the threshold level, a decision is made that at least one of the semiconductor switches S1, S2 is abnormal. According to the arrangement, stress on the semiconductor switch can be lessened while shortening the time required for failure diagnosis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energization control device for energizing a control target such as a DC motor which is a drive source of an electric actuator, and a self-diagnosis method thereof.

[0002]

2. Description of the Related Art An energization control apparatus 1 shown in FIG. 4 is an apparatus for energization control of a DC motor 2 which is a drive source of an electric actuator, and has a positive terminal of a battery power supply 3 and a positive voltage application to the DC motor 2. The switching circuit 4 connected between the terminals is controlled by a microprocessor 5 to conduct. The switch circuit 4 is formed by connecting in parallel a number of semiconductor switches corresponding to the drive current required for driving the DC motor 2. In this example, the switch is turned on or off depending on the gate voltage applied to the gate. (Semiconductor Switches S1 and S2)
Are connected in parallel with each other to meet the drive current requirements. The gates of the semiconductor switches S1 and S2 are connected to the output port of the microprocessor 5. A positive voltage application terminal of the DC motor 2 is connected to an input port with a built-in A / D converter of the microprocessor 5 via a filter circuit 6. The filter circuit 6 includes a low-pass filter circuit including a resistor R and a capacitor C, and functions to smooth the voltage applied to the DC motor 2 and supply the smoothed voltage to the input port of the microprocessor 5.

Incidentally, the semiconductor switches S1 and S2 are
It has more failure modes than a mechanical relay or the like, and periodic failure diagnosis is indispensable. The switch circuit 4 shown in this example is configured by connecting a pair of semiconductor switches S1 and S2 in parallel in order to meet the drive current requirement of the DC motor 2, so that each semiconductor switch S
1 and S2 need to be individually diagnosed. Therefore, conventionally, the semiconductor switches S1 and S2 are turned on alternately at a set time interval in consideration of a sufficient margin, and the applied voltage Vd of the DC motor 2 at that time is taken in through the filter circuit 6. A method of judging a failure by judging a threshold value of the smoothed output voltage Vm has been adopted. FIG. 5 is a flowchart for explaining a failure diagnosis operation by the microprocessor shown in FIG. 4, and FIGS. 6A and 6B are diagrams showing a circuit of the motor drive device shown in FIG. It is a signal waveform diagram of each part.

In diagnosis, first, as shown in step (201) of FIG. 5, the microprocessor 5 turns on one semiconductor switch S1. Then, a fixed time T required for the applied voltage Vd of the DC motor 2 to stabilize.
The conduction state is maintained until 1 has elapsed. Then, if the specified fixed time T1 has elapsed, the judgment step (20)
In the judgment step (203) following 2), the voltage Vd smoothed and output by the filter circuit 4 is taken in via an A / D converter (not shown) built in the input port, and the voltage Vd is input to the diagnostic operation program of the microprocessor 5. Is compared with the failure determination threshold value Vthh set in (1).

If the semiconductor switch S1 is normal,
As shown in FIG. 6A, the applied voltage Vd of the DC motor 2 increases with a slight delay after the conduction, and finally stabilizes at a voltage very close to the output voltage of the battery power supply 3. Therefore, when the predetermined time T1 has elapsed after the conduction, the smoothed output voltage Vm has exceeded the failure determination threshold value Vthh, and the determination in the determination step (203) is affirmed. The determination in the determination step (203) is affirmed,
When the semiconductor switch S1 is found to be normal, as a second step, in step (204), the microprocessor 5 turns on the other semiconductor switch S2,
In the immediately following step (205), the semiconductor switch S
1 is non-conductive. In this case, too, the fixed time T1 required for stabilizing the applied voltage Vd to the DC motor 2 is obtained.
Is maintained until a predetermined time T1 elapses, and in a determination step (207) following the determination step (206), the output voltage V of the filter circuit 6 is determined.
m is compared with a failure determination threshold value Vthh set on a program of the microprocessor 5.

In this case, if the semiconductor switch S2 is normal, as shown in FIG.
d maintains However, when the semiconductor switch S2 is out of order, the applied voltage Vd cannot maintain a voltage very close to the output voltage of the battery power supply 3, and drops as time passes, as shown in FIG. Therefore, when a certain time T1 elapses after the conduction, the smoothed output voltage Vm becomes 0
The voltage drops to near V, and as a result, it is determined in the determination step (207) that Vm ≦ Vthh. Thereby, the failure is notified in step (211) assuming that the semiconductor switch S2 has failed.

If no abnormality is detected in the semiconductor switches S1 and S2 up to the step (207), the microprocessor 5 proceeds to the next step (208).
, The semiconductor switch S2 is turned off. And
A constant time T sufficient for the applied voltage Vd to converge to zero voltage
2, the output voltage Vm of the filter circuit 6 is determined in a step (210) following the determination step 209.
And compares it with the failure determination threshold value Vthl set on the program of the microprocessor 5 in step (210). In this case, the semiconductor switches S1,
If both S2 are normal, the applied voltage V
Although m is stabilized at a voltage very close to 0 V, if any one of them is abnormal, it does not fall below the failure determination threshold voltage Vthl. For this reason, if it is determined that Vm> Vthl, it means that one of the semiconductor switches S1 and S2 has failed, and step (21)
A failure is reported in 1).

[0008]

In the conventional energization control device 1, the microprocessor 5 alternately operates the two semiconductor switches S1 and S2 for a predetermined time according to a self-diagnosis program, and applies the DC motor 2 at that time. Voltage V
The voltage Vm obtained by smoothing d is compared with the failure determination threshold voltage Vthh or Vthl, and self-diagnosis is performed according to the comparison result. However, the diagnosis of the individual semiconductor switches S1 and S2 is performed by allocating time periods T1 and T2 sufficient to stabilize the applied voltage Vd applied to the DC motor 2, and determining the smoothed output voltage Vm under statically stable conditions. Since the threshold value was determined, a large inrush current flowed into the semiconductor switch S1 or S2 at each diagnosis. For this reason, the stress caused by such a large current is accumulated each time diagnosis is performed, and the temperature rise caused by the steady current promotes the stress. Furthermore, since the diagnosis is performed while the semiconductor switches S1 and S2 are alternately operated at a sufficient time interval, the time required for the diagnosis becomes longer as the number of semiconductor switches constituting the switch circuit 4 increases. It was something to have.

The present invention has solved the above-mentioned problems, and
It is an object of the present invention to reduce the energizing time and energizing interval to a semiconductor switch, to reduce stress on the semiconductor switch, and to shorten the time for failure diagnosis.

[0010]

To achieve the above object, an energization control device according to the present invention comprises a plurality of semiconductor switches connected in parallel to each other, and a switch circuit connected between a control target and a power supply; A filter circuit for smoothing and detecting a voltage applied to the control target, and individually controlling conduction of each semiconductor switch of the switch circuit;
In the diagnostic mode, the plurality of semiconductor switches are sequentially turned on in a time-sharing manner at a fixed time interval for a time shorter than a time during which an inrush current flowing during conduction rises to an absolute maximum rated value, and a predetermined number of times of conduction is reached. A threshold value discrimination of the output of the filter circuit at the time when the threshold value is reached, and a microprocessor that diagnoses that at least one of the plurality of semiconductor switches is abnormal when the output value is equal to or less than the threshold value.

In addition, the self-diagnosis method of the power supply control device according to the present invention controls the conduction of a plurality of semiconductor switches connected in parallel between a control target and a power supply, and controls a voltage applied to the control target. A self-diagnosis method for an energization control device that detects by smoothing, wherein a time interval is shorter than a time period during which an inrush current flowing into the plurality of semiconductor switches during conduction increases to an absolute maximum rated value at a predetermined time interval. Conduction is sequentially performed in a divided manner, and when the predetermined number of times of conduction is reached, the smoothed voltage is discriminated as a threshold value, and when the voltage is equal to or less than the threshold value, at least one of the plurality of semiconductor switches is diagnosed as abnormal It is characterized by doing.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic circuit configuration diagram showing an embodiment of a motor drive device to which an energization control device according to the present invention is applied, and FIG. 2 is a flowchart for explaining a failure diagnosis operation by the microprocessor shown in FIG. 3 (A) and 3 (B) are signal waveform diagrams of respective parts of the circuit of the motor drive device shown in FIG. 1 at the time of normal operation and at the time of failure, respectively.

The energization control device 11 shown in FIG. 1 has almost the same circuit configuration as the conventional one except for the microprocessor 12 in terms of circuit configuration. As the microprocessor 12, improved software for diagnosing the semiconductor switches S1 and S2 is used. With this improvement, the semiconductor switches S1 and S2 can be diagnosed in a short time without exerting excessive stress. The biggest improvement of the diagnostic software installed in the microprocessor 12 is that the semiconductor switch S
1 and S2 are turned on sequentially in a time-division manner at regular time intervals for a time shorter than the time during which the inrush current flowing during conduction rises to the absolute maximum rated value. The point is that the current supply time and the current supply interval can be considerably reduced as compared with the related art.

Here, when the microprocessor 12 starts a diagnostic operation in the diagnostic mode, first, in step (101), the semiconductor switch S1 is turned on, and the state is maintained for τ1 time. However,
As described above, the conduction time τ1 is set to be shorter than the time during which the rush current flowing at the moment when the semiconductor switch S1 is turned on increases to the absolute maximum rated value of the semiconductor switch S1. Subsequently, when the time τ1 has elapsed,
In a step (103) following the determination step (102), the semiconductor switch S1 is turned off. In this case, the non-conduction period τ2 is set to be approximately the same as the conduction period τ1.

When the time τ2 has elapsed since the semiconductor switch S1 was turned off, the microprocessor 12 turns on the semiconductor switch S2 in a step (105) following the determination step (104), and the state is changed over the time τ1. Persist. However, the conduction time τ1 is also shorter than the time when the inrush current flowing at the moment when the semiconductor switch S2 is turned on rises to the absolute maximum rated value of the semiconductor switch S2. continue,
When the time τ1 has elapsed, in the step (107) following the determination step (106), the semiconductor switch S2
Is turned off. In this case, the non-conduction period τ2 is set to a time approximately equal to the conduction period τ1.

When the time τ2 has elapsed since the semiconductor switch S2 was turned off, in the step (109) following the determination step (108), the processing from the step (101) to the step (108) is repeated a predetermined number of times. Determine if it has been performed. If the number of executions is less than the predetermined number, the process returns from the determination step (109) to the step (101) and repeats the same operation as before.
If the number of executions has reached the predetermined number, the output voltage Vm of the filter circuit 6 is determined in the subsequent determination step (110).
Is determined.

In this case, if the semiconductor switches S1 and S2 are both normal, the DC motor 2 is τ1 / (τ1 + τ
Since the current is intermittently supplied a predetermined number of times with the duty of 2), the smoothed output voltage Vm rises to the steady drive voltage as shown in FIG. 3A, and is very close to the output voltage of the battery power supply 3. Stabilizes with voltage. Therefore, when the threshold value Vm is higher than the threshold voltage Vth when the threshold value of the smoothed output voltage Vm is determined in the determination step (110), it can be determined that both the semiconductor switches S1 and S2 are normal. . On the other hand, the semiconductor switch S
If any one of S1 and S2, for example, S2 is faulty, the DC motor 2 is intermittently energized only at a duty of τ1 / 2 (τ1 + τ2), and as shown in FIG. The voltage Vd applied to the DC motor 2 does not increase to the extent that energization by the failed semiconductor switch S2 is lost. Therefore, in the determination step (110), the smoothed output voltage V
m, the threshold voltage Vth is set to Vm
Will not exceed. That is, Vth ≦ Vm.
Therefore, the microprocessor 12 can diagnose whether the semiconductor switches S1 and S2 are normal or at least one of them is abnormal according to the threshold value determination result at this time.

As described above, the above-described power supply control device 11
Semiconductor switches S1 and S2 constituting switch circuit 4
Are successively conducted in a time-division manner at a constant time interval τ2 for a time τ1 shorter than the time during which the inrush current flowing during conduction rises to the absolute maximum rated value, and when the prescribed number of conductions is reached, Smooth output voltage Vm of motor 2
Is determined as a threshold value, and when the difference is equal to or less than the threshold value, at least one of the semiconductor switches S1 and S2 is diagnosed as abnormal.
Therefore, stress is not given due to excessive inrush current flow, and a failure diagnosis can be performed without overdoing. Therefore, for example, a sufficient time is allowed for the applied voltage Vd to be applied to the DC motor 2 to stabilize, and the threshold value of the smoothed output voltage Vm is determined under statically stable conditions, as in the conventional apparatus 1. Each time the inrush current of the large current flows into the semiconductor switches S1 and S2, the stress caused by the large current does not accumulate as the frequency increases, and the failure rate does not increase due to the stress of the temperature rise due to the steady current, etc. In addition, the time required for the failure diagnosis is determined from the voltage application characteristics of the DC motor 2 and the time constant of the filter circuit 6, and the plurality of semiconductor switches S1 and S2 are sequentially turned on in a time-sharing manner. This makes it possible to make a diagnosis, and unlike the conventional method in which sufficient time is allocated to stabilize the applied voltage applied to the DC motor 2, In it is possible to complete the diagnosis.

In the above embodiment, the case where the switch circuit 4 composed of a pair of semiconductor switches S1 and S2 is used is taken as an example. However, the number of semiconductor switches constituting the switch circuit 4 is three or more. You may. Further, the energization control target is not limited to the DC motor 2 and may be an energization control target such as another drive source of the electric actuator.

[0020]

As described above, according to the present invention,
The semiconductor switches that constitute the switch circuit are sequentially turned on in a time-division manner at regular time intervals for a time shorter than the time during which the inrush current flowing during conduction rises to the absolute maximum rated value, and a predetermined number of times of conduction. At that point, the applied voltage of the control target is determined as a threshold value. If the applied voltage is lower than the threshold value, at least one of the semiconductor switches is diagnosed as abnormal. Without the stress associated with the current flow, it is possible to diagnose the failure without overdoing it.Therefore, allocate sufficient time for the applied voltage to be applied to the control target to stabilize, and under statically stable conditions. As in the conventional device that determines the threshold of the applied voltage, a large inrush current flows into the semiconductor switch at each diagnosis, and the stress due to the large current increases. The failure rate does not increase due to stress caused by temperature rise due to steady current, and the time required for failure diagnosis is determined by the voltage application characteristics of the control target and the time constant of the filter circuit. Conventionally, a plurality of semiconductors are sequentially turned on in a time-sharing manner, so that diagnosis can be performed by turning on only a necessary minimum number of times, and sufficient time is allocated to stabilize an applied voltage applied to a control target. In contrast to the method described above, an excellent effect is obtained such that the diagnosis can be completed in a short time.

[Brief description of the drawings]

FIG. 1 is a schematic circuit configuration diagram showing one embodiment of a motor drive device to which an energization control device of the present invention is applied.

FIG. 2 is a flowchart for explaining a failure diagnosis operation by the microprocessor shown in FIG. 1;

FIGS. 3A and 3B are signal waveform diagrams of respective parts of the circuit of the motor drive device shown in FIG. 1 in a normal state and a fault state, respectively.

FIG. 4 is a schematic circuit configuration diagram showing an example of a motor drive device to which a conventional energization control device is applied.

FIG. 5 is a flowchart for explaining a failure diagnosis operation by the microprocessor shown in FIG. 4;

6 (A) and 6 (B) are signal waveform diagrams of respective parts of the circuit of the motor drive device shown in FIG. 4 in a normal state and a fault state, respectively.

[Explanation of symbols]

 2 DC motor (control target) 3 Battery power supply 4 Switch circuit 6 Filter circuit 11 Current control device 12 Microprocessor S1, S2 Semiconductor switch

Claims (2)

[Claims] A switch circuit comprising a plurality of semiconductor switches connected in parallel to each other and connected between a control target and a power supply; a filter circuit for smoothing and detecting a voltage applied to the control target; While conducting conduction control of each semiconductor switch of the switch circuit individually, at the time of the diagnostic mode, the rush current flowing when conducting the plurality of semiconductor switches during a period shorter than the time during which the inrush current rises to the absolute maximum rated value is provided at fixed time intervals. Conducted sequentially in time division,
A microprocessor that determines a threshold value of the output of the filter circuit when a predetermined number of times of conduction is reached, and diagnoses that at least one of the plurality of semiconductor switches is abnormal when the output value is equal to or less than the threshold value. An energization control device characterized by the above-mentioned. 2. A self-diagnosis method for an energization control device that individually controls conduction of a plurality of semiconductor switches connected in parallel between a control target and a power supply and smoothes and detects a voltage applied to the control target. The plurality of semiconductor switches are sequentially turned on in a time-division manner at regular time intervals for a time shorter than a time during which an inrush current flowing during conduction rises to an absolute maximum rated value, at a predetermined number of times of conduction. When the voltage reaches the threshold value, the threshold value is determined for the smoothed voltage,
A self-diagnosis method for an energization control device, characterized in that at least one of the plurality of semiconductor switches is diagnosed as abnormal when the threshold value is equal to or less than a threshold value.