JPH048114A - Output forbidding circuit against excessive power supply voltage - Google Patents

Abstract

PURPOSE:To avoid the misoperation of an antilock breaking system by a method wherein, when an overvoltage in supplied by a power supply, the overvoltage is absorbed by an overvoltage absorbing circuit which is connected between a power supply line and an output forbidding means and the output forbidding means is protected from the supply of the overvoltage. CONSTITUTION:In an antilock breaking system, when an overvoltage is supplied by a power supply, the supply of the overvoltage to an output forbidding device 3 is restricted by a resistor 6 and a Zener diode 5 which are connected to a power supply line 100. At that time, an output forbidding signal 102 is outputted from the output forbidding device 3 in accordance with the overvoltage detection signal 104 of an overvoltage detecting circuit 2 and an output circuit 4 does not outputs a driving signal for an actuator 8. Further, a reverse current from the output circuit 4 to the output forbidding device 3 is blocked by an inverter 7. With this constitution, even if an overvoltage output is inputted to a CPU 1, the output is securely forbidden by the output forbidding device 3 and, moreover, the output forbidding device 3 itself is protected from the overvoltage by an overvoltage absorbing circuit 10 and the inverter 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to an output prohibition unit used in an output prohibition unit of an electronic control unit (ECU) such as an anti-lock brake system (ABS) for a vehicle when a power supply overvoltage occurs. It is related to circuits.

(Prior Art) In recent years, in order to prevent traffic accidents, there has been a demand for safety measures for the structure of vehicles and the various devices installed on them.

Anti-lock braking system (ABS)
has been used in some luxury cars.

In the electronic circuits used in this anti-lock brake system (ABS), if the power supply voltage is higher than the standard, it becomes difficult to guarantee reliable circuit operation, so an output inhibit circuit is used to prevent the circuit from malfunctioning. There is a need.

FIG. 3 is a circuit diagram showing an example of a conventional output prohibition circuit at the time of 8-power overvoltage.

Reference numeral 50 denotes a microcomputer (CPU), through which foot brake operation information and the like from a foot brake (not shown) is input to the CPU 50 .

A voltage signal is input to the overvoltage detection circuit 51 from a power supply section (not shown), and it is detected whether the voltage signal is equal to or higher than a desired threshold value.

Further, the output prohibition element 52 is connected to the overvoltage detection circuit 51 and the power supply line, and the output prohibition element 52 has, for example,
Output is prohibited when there are two inputs.

On the other hand, the output circuit 53 includes the CPU 50 and the output inhibiting element 5.
2, and supplies an output signal to the actuator 54 when there is an output from the CPU 50.

The output circuit 53 is connected to the actuator 54, and the actuator is driven by the output from the output circuit 53.

(Problem to be solved by the invention) However, the conventional ABS (anti-lock brake system)
In the output prohibition circuit of the system), the power supply terminal voltage increases when the power supply voltage exceeds a predetermined threshold.

Therefore, in the conventional ABS output inhibit circuit, the circuit elements, CPU, etc. may become inoperable due to overvoltage, and there is a possibility that a sufficient braking effect by the foot brake cannot be obtained.

Therefore, the present invention provides a microcomputer (CPU)
In view of the fact that the output inhibiting means is vulnerable to overvoltage and may cause malfunction or inoperable state, an output inhibiting circuit with a simple circuit configuration that can reliably shut off overvoltage output without installing a protection circuit in the CPU has been developed. The purpose of the present invention is to provide an output prohibition circuit in the event of power supply overvoltage, which securely cuts off overvoltage output and prevents the anti-lock braking system (ABS) from malfunctioning by adding an output prohibition means. It is.

(Means for Solving the Problem) As a means for solving the above problem, the present invention inputs a signal supplied from a microcomputer to an output means when an electric signal supplied from a power supply line is normal,
A power source that supplies the drive signal output from the output means to the actuator, and when the electric signal supplied from the power supply line has an overvoltage, the overvoltage detection means detects the voltage, and the output is inhibited by the output prohibition means. Output inhibiting means at the time of overvoltage, wherein an inverter is connected in a forward direction between the 8-force inhibiting means and the output means, and an overvoltage absorption circuit is connected between the power supply line and the output inhibiting means. It is characterized by this.

(Function) When the electrical signal supplied from the power supply line is normal,
A signal supplied from the microcomputer is input to the output means, and a drive signal output from the output means is supplied to the actuator.

When the electric signal supplied from the power supply line has an overvoltage, the overvoltage is absorbed by an overvoltage absorption circuit connected between the power supply line and the output inhibiting means, so that the overvoltage is not supplied to the output inhibiting means. Make it.

Furthermore, by connecting the inverter in the forward direction between the output inhibiting means and the output means, there is no possibility that a reverse current will flow into the output inhibiting means.

(Example) Next, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a circuit diagram showing an output control circuit of an embodiment of the output prohibition circuit at the time of output overvoltage according to the present invention.Hereinafter, an example in which this output control circuit is applied to an anti-lock brake system (ABS) will be explained. Proceed.

Reference numeral 1 denotes a microcomputer (CPU), which inputs foot brake operation information and the like from a foot brake (not shown) to CPtJl.

The output prohibition circuit of this embodiment includes an overvoltage detection circuit 2 which is an overvoltage detection means for detecting a power supply overvoltage of a constant voltage circuit 38 (described later), an output prohibition element 3 which is an output prohibition means for determining output prohibition, and an output prohibition element 3 which is an output prohibition means for determining output prohibition. It is composed of an output circuit 4 that is an output means for inhibiting, a Zener diode 5 and a resistor 6 that constitute an overvoltage absorption circuit l○ that absorbs overvoltage, and an inverter 7 that protects the output inhibiting element 3 at the time of overvoltage.

The overvoltage detection circuit 2 is connected via a power supply line 100 to a constant voltage circuit 38 that outputs a constant voltage of 5 (V) and is connected to a power supply section BT in FIG. 2, which will be described later.
A voltage signal is input to , and it is detected whether the level of the voltage signal at that time is equal to or higher than a desired threshold value.

Further, the output side of the overvoltage detection circuit 2 is connected to one input side of the output prohibition element 3, and the overvoltage absorption circuit 10 connected to the power supply line l○0 is connected to the other input side of the output prohibition element 3. It is connected.

A Zener diode 5 is connected between the output inhibiting element 3 and the resistor 6.
are connected, the overvoltage is reduced by these, and therefore no overvoltage is applied to the output inhibiting element 3.

Note that as the output inhibiting element 3, for example, a gate array or a CPU is used.

The output inhibiting element 3 includes a runaway detection circuit for the CPU 1, and one of the output terminals of the CPU 1 is connected to one of the input terminals of the output inhibiting element 3.

One input side of the output circuit 4 is connected to the output side of the CPU 1, and the other input side of the output circuit 4 is connected to the output side of the 8-force inhibiting element 3 via an inverter 7.

The output circuit 4 is composed of an AND gate 4a and an NPN transistor 4b, and an NPN transistor is connected to the output side of the AND gate 4a.
When the base of the transistor 4b is connected and there is a logic gate output of the AND gate 4a, a base voltage is applied to the base of the NPN transistor 4b, turning on the transistor 4b.

Furthermore, since the solenoid 9 of the actuator 8 is connected to the output side of the output circuit 4, current flows through the solenoid 9 of the actuator 8 when the transistor 4b is turned on, and the actuator 8 is driven.

Next, a specific configuration of an anti-lock brake system that employs an output prohibition circuit at the time of power supply overvoltage according to an embodiment of the present invention will be described.

This anti-lock brake system is the rear brake LS
It uses PV.

Note that detailed explanation of the same configuration as in FIG. 1 will be omitted here.

The output boat 30a of the foot brake 30 is connected to the oil path 200.
is connected to the brake shoes 31a and 31b of the front brake 31, and is connected to the brake shoes 31a and 31b of the front brake 31.
Wheel cylinder 3 of rear brake 34 via SPV 33
4a and 34b are connected.

On the other hand, the output boat 30b of the foot brake 30 is connected to the input boat 30b of the regulator valve 32 via the oil passage 202.
connected to a.

Then, the output boat 32 b of the regulator valve 32
C. The oil passages 203 and 201 are connected to the wheel cylinders 34a and 34b of the rear brake 34 via the LSPV 33.

Further, the output boat 32c of the regulator valve 32 is connected to the manual boat 9a of the solenoid valve 9 via an oil passage 204.

On the other hand, the output boat 9b of the solenoid valve 9
05 to a reservoir 35, and hydraulic oil is temporarily stored in the reservoir 35.

Further, the reservoir 35 is connected to the inlet valve 36a side of the oil pump 36 through an oil passage 206.

The outlet valve 36b side of the oil pump 36 is connected to the regulator valve 32 through an oil passage 207 and an oil passage 202.

On the other hand, in FIG. 2, gear information from a sensor 37 is input through a signal line 300 to an input terminal 1a of a CPU of an electronic control unit ECU.

Further, the output circuit 4 of the electronic control unit ECTJ is connected to the solenoid valve by a signal line 301, and the output circuit 4
The opening and closing of the solenoid valve 9 is controlled by the output of the solenoid valve 9.

Note that 38 is a constant voltage circuit for stabilizing the power supply.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2.

First, a case where the anti-lock brake system operates normally will be described.

At this time, the output signal 101 from the CPU 1 is sent to the output circuit 4.
However, the output inhibiting element 3 inhibits the output of the actuator drive signal 103 from the output circuit 4 shown in FIG.

Then, from the output circuit 4, the actuator drive signal 1
03 is output in response to the signal output from the CPU1.

When the output signal 101 of CPtJl is a signal for driving the actuator and the output prohibition signal 102 is not output from the output prohibition element 3, the actuator 8
Solenoid valve 9 is activated.

When the solenoid valve 9 is operating, the brake pressure is reduced, so the anti-lock brake system is activated.

That is, when the solenoid valve 9 is in operation, the hydraulic oil is supplied from the oil pump 36 to the wheel cylinders 34a and 34b of the rear brake 34 via the oil passage 207, the regulator valve 32, the passage 203, the LSPV 33, and the passage 201. Since the oil pressure is reduced from the oil pressure of the hydraulic oil supplied from the oil pump 36 to the wheel cylinders 34a, 34b of the rear brake 34 when the solenoid valve 9 is in the inactive state, it is possible to control the rear brake 34 so that it is not locked. can.

On the other hand, when the voltage output from the constant voltage circuit 99 is equal to or higher than the desired threshold, the overvoltage detection signal 104 is input from the overvoltage detection circuit 2 to the output prohibition element 3, and the output prohibition signal 102 (signal O) is output, and the output of the actuating signal of the actuator 8 from the output circuit 22 is regulated.

Therefore, in this embodiment, even if the CPU 1 malfunctions and an erroneous signal is input to the output circuit 4 during power supply overvoltage, the two input signals are not input to the AND gate 4a, so no gate output is obtained.

Therefore, no base voltage is applied to transistor 4b, and transistor 4b does not operate.

Therefore, no current flows through the solenoid 9 of the actuator 8, so the solenoid 9 does not operate.

On the other hand, in the event of overvoltage, the resistor 6 and Zener diode 5 connected to the power supply line 100 prevent the output inhibiting element 3.
Since the supply of overvoltage to the input terminal is regulated, destruction of the output inhibiting element 3 can be prevented.

Therefore, as mentioned above, when the voltage output from the constant voltage circuit 38 exceeds the desired threshold, the overvoltage detection circuit 38
An output prohibition signal 102 is output from the output prohibition element 3 in response to the overvoltage detection signal 104, and the drive signal for the actuator 8 is prevented from being output from the output circuit 4.

Further, in this embodiment, the inverter 7 allows the output circuit 4 to
A reverse current is also prevented from flowing from the output inhibiting element 3 to the output inhibiting element 3.

As described above, according to this embodiment, by adding a simple circuit configuration to the existing control circuit, the overvoltage output can be controlled by the ECU.
Even if the input is input to the CPU 1 of
Can be protected from overvoltage.

(Effects of the Invention) As described above, according to the present invention, by adding a simple circuit configuration to the existing circuit, even if a voltage value higher than the desired threshold is input from the constant voltage circuit to the microcomputer, the output Not only can the output be reliably inhibited by the inhibiting means, but also the overvoltage detection circuit can be protected from overvoltage by using the overvoltage absorption circuit and the inverter as the output inhibiting means.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an output control circuit of an embodiment of the output prohibition circuit at the time of output overvoltage of the present invention, Fig. 2 is an overall system diagram showing the operation of this embodiment, and Fig. 3 is a conventional power supply overvoltage control circuit. FIG. 3 is a diagram illustrating an example of an output prohibition circuit at a time. In the figure, 1 is a microcomputer (CPU), 2 is an overvoltage detection means, 3 is an output inhibiting means, 4 is an output means, 7 is an inverter, 8 is an actuator, and 10 is an overvoltage absorption circuit. Patent applicant: Aisin Seiki Co., Ltd. Applicant: Fujitsu Ten Co., Ltd. Figure 1

Claims (1)

[Scope of Claims] When the electrical signal supplied from the power supply line is normal, the signal supplied from the microcomputer is inputted to the output means, and the drive signal outputted from the output means is supplied to the actuator, and the power supply When an electric signal supplied from a supply line has an overvoltage, an overvoltage detection means detects the voltage and the output is inhibited by an output inhibiting means. An inverter is forward-connected to the output inhibiting circuit, and an overvoltage absorbing circuit is connected between the power supply line and the output inhibiting means.