JPH0613232A - Abnormality detecting device for load drive circuit - Google Patents

Abstract

PURPOSE:To reduce the number of parts and to reduce the cost of a load drive circuit by a method wherein an abnormality detecting device is provided with an abnormality detecting means for detecting the presence or absence of a continuity of a rectifying means. CONSTITUTION:A transistor Tr3 is turned on based on a high-level signal inputted to the base of a transistor Tr1 from a CPU 3 and a current is made to flow through a rotary solenoid 1. An anode voltage of a diode D1, which is used as a protective circuit, is monitored and a low-level signal at the time of grounding of a terminal is detected to detect the operation of the protective circuit. Here, an anode side signal level of the diode D1, which is used as a rectifying means, is inputted to a port P3 of the CPU 3 to correspond to an abnormality detecting means and the CPU 3 decides the state of the operation of the protective circuit on the basis of an abnormality decision table. When the side of an input of the solenoid 1 is in a state that it is grounded and the upstream side transistor Tr3 is turned on, a terminal voltage is turned into an earth potential, the diode D1 is made to have continuity and a base potential in the transistor Tr1 is reduced to 0 volt. As a result, the transistors Tr1 and Tr3 are both turned on and the transistor Tr3 can be prevented from being broken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load drive circuit abnormality detection apparatus.

[0002]

2. Description of the Related Art For example, some active suspensions of automobiles have recently used a rotary solenoid as a control actuator (Japanese Patent Application No. 3-34).
6077). In FIG. 3, load drive circuits 2a to 2c are connected to the rotary solenoid 1 via harnesses, for example, so that the rotary solenoid 1 is excited in two-phase to three-phase.

Further, in FIG. 4 showing each load drive circuit 2 of the rotary solenoid 1, an NPN transistor T is shown.
A push-pull drive circuit is configured by connecting r ₃ and PNP transistor Tr ₄ in series between the power supply of voltage V _B and ground, and connecting the rotary solenoid 1 as a load to the connection point. The push / pull drive circuit controls the energization direction of the rotary solenoid 1 to be bidirectional. Transistors Tr ₁ and Tr ₂ are CPUs respectively
A high-level signal "H" or a low-level signal "L" is input from the ports P ₁ and P _{2 of 3} to drive and control the NPN transistor Tr ₃ and the PNP transistor Tr ₄ , respectively.

In the load driving circuit 2, for example, if the upstream transistor Tr ₃ is turned on while the harness connecting the rotary solenoid 1 is grounded, the transistor Tr ₃ may be burned by an overcurrent. In circuit 2, upstream transistor Tr at ground fault
_It is general to provide a protection circuit so that ₃ is turned off, and the diode D ₁ as the protection circuit is connected between the terminal p and the base of the transistor Tr ₁ with the terminal p on the cathode side. With this diode D ₁ , the terminal voltage V _p of the terminal _p is short-circuited to the transistor Tr ₁ due to grounding of the harness.
When the voltage drops below the base voltage of the transistor T
r ₁ and Tr ₃ turn off to protect the push-pull drive circuit.

Further, when the harness ground faults, the original operation of the rotary solenoid 1 is disabled, so that it is necessary to warn the driver of the state. Therefore, in the conventional load drive circuit 2, in addition to the protection circuit, the terminal p An abnormality detection device is provided for monitoring the terminal voltage V _p of the. The abnormality detecting device is composed of a terminal monitor circuit 4 and a CPU _{3. In} the terminal monitor circuit 4, the diode D ₂ is a diode for blocking the voltage due to the back electromotive force of the rotary solenoid 1 and protecting the PNP transistor Tr ₅ and has a high withstand voltage. It is a thing. A resistor R ₆ is connected between the collector of the transistor Tr ₅ and the ground, and the terminal voltage of the resistor R ₆ is input to the port P ₃ of the CPU 3. The CPU 3 is provided with the abnormality determination table of FIG. 5, and the ground fault of the terminal p is detected based on this abnormality determination table.

Next, the abnormality detecting operation will be described. Terminal p is positive
Always, port P₁, P₂High level signal from both
When "H" is output, the transistor Tr₁, Tr₂Each
Turn on, off, transistor Tr₃, Tr _FourTurns on and off
Terminal voltage V of terminal p_pBecomes "H", and the CPU3
Red P ₃Signal level becomes "L". Also port
P₁, P₂When both output low level signal "L"
Transistor Tr₁Tr₂Turn off and on, respectively
Ta Tr ₃, Tr_FourTurns off and on, and the terminal voltage V_pIs "L"
Nari CPU3 port P₃Signal level is "H"
It

Therefore, when the upstream side transistor Tr ₃ is turned on, the signal level of the port P ₃ of the CPU 3 changes to the mode.
Corresponding to 11, when the downstream side transistor Tr ₄ is turned on,
Since the signal level of the port P ₃ corresponds to the mode 12, it is determined that the terminal p is not grounded. CPU3
Despite port P ₃ of the signal for turning on the upstream side transistor Tr ₃ from the port P ₁ "H" is output
5 is "H" as in mode 13 of FIG. 5, it is determined that the harness connecting the load drive circuit 2 and the rotary solenoid 1 is grounded.

[0008]

By the way, in the conventional load drive circuit abnormality detection apparatus, the rotary solenoid 1 is used.
In order to directly monitor the terminal voltage V _p of the output terminal p to the output terminal p, it is necessary to have a strong terminal monitor circuit 4 that can withstand the voltage due to the back electromotive force of the rotary solenoid 1, which reduces the cost of the parts constituting the terminal monitor circuit 4. It could not be reduced.

The present invention has been made in view of such conventional problems, and an object thereof is to provide an abnormality detecting apparatus for a load drive circuit which can reduce the number of parts and the cost.

[0010]

Therefore, the present invention is a load drive circuit for driving a load with a high level drive signal based on an input high level control signal. In the load drive circuit including the protection circuit for the load drive circuit having the rectifying means that conducts only from the input side to the load side, the abnormality detecting means for detecting the conduction of the rectifying means is provided.

[0011]

According to the above construction, when the protection circuit operates,
The rectifying means becomes conductive. The abnormality detecting means detects that the rectifying means is conducting, and the abnormality of the load drive circuit is detected. Therefore, since the configuration of the abnormality detecting means is simple, the cost can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same elements as those in FIGS. 3 to 5 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 1 showing the present embodiment, the conventional terminal monitor circuit is eliminated, and the signal level of the anode of the diode D ₁ as the rectifying means is input to the port P ₃ of the CPU 3. Further, the CPU 3 corresponds to abnormality detecting means, and the CPU 3 is provided with the abnormality determination table shown in FIG.

Next, the operation will be described. Upstream transistor
When Tr ₃ is on and terminal p is not grounded,
Since the terminal voltage V p of the terminal _p is higher than the signal level of the port P ₁ , the diode D ₁ does not conduct. Thus the base potential of the transistor Tr ₁ becomes "H" level, the signal level is input to the port P ₃ of the CPU 3. Then, the signal level of the port P ₃ is compared with the abnormality determination table of FIG. 2, and since it corresponds to the mode 1, it is determined that the protection circuit is not operating.

As shown by the dotted line in FIG. 1, the terminal p is grounded.
The upstream transistor Tr in the entangled state ₃Is turned on,
Terminal voltage V_pIs at ground potential, diode D₁But
Conduct transistor Tr₁The base potential of is 0V,
Transistor Tr₁, Tr₃Turns off and turns off due to overcurrent.
Dista Tr₃Is prevented from burning. On the other hand, this base potential
Is port P₃Is also input to port P₃The signal level of
Since it corresponds to mode 2 when the terminal p is grounded,
D₁Is connected and it is judged that the protection circuit is operating, and the dotted line
A ground fault at the terminal p is detected as indicated by.

According to this structure, the terminal voltage of the rotary solenoid 1 is not directly monitored, but when the terminal p is grounded, the diode D ₁ as a protection circuit is turned on and the base voltage of the transistor Tr ₁ becomes 0V. Since it is possible to detect an abnormality in the load drive circuit 2 by detecting that
The conventional terminal monitor circuit can be eliminated, and the cost can be reduced.

[0016]

As described above, according to the present invention, the circuit configuration can be simplified and the cost can be reduced by detecting the presence or absence of conduction of the rectifying means and detecting the abnormality.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an abnormality determination table of FIG.

FIG. 3 is a circuit diagram of a rotary solenoid.

FIG. 4 is a conventional circuit diagram.

5 is a diagram showing an abnormality determination table of FIG.

[Explanation of symbols]

1 Rotary Solenoid 2a ~ 2c Load Drive Circuit 3 CPU D ₁ Diode

Claims (1)

[Claims] 1. A load drive circuit for driving a load with a high-level drive signal based on a high-level control signal that is input, the rectifier being conductive only from the control signal input side of the load drive circuit to the load side. A load drive circuit including a protection circuit for the load drive circuit having means, comprising: abnormality detection means for detecting the presence or absence of conduction of the rectifying means.