JPH0525963Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a load protection circuit in a control device such as an auto suspension device that detects changes in vehicle speed or vehicle height and switches and controls shock absorber damping force. It is.

[Conventional technology]

As a conventional load protection circuit, there is one shown in FIG. 3, for example. In the figure, is an arithmetic processing circuit that controls the load of a motor, etc. for driving a variable-diameter orifice for oil flow control in the shock absorber based on information on changes in vehicle speed and vehicle height output from various sensors (not shown). It calculates various control signals for control and outputs the various control signals to the drive circuit. The drive circuit generates a current that drives the load based on various control signals output from the arithmetic processing circuit. is a current detection circuit that detects the current applied from the drive circuit. The current detection circuit outputs a monitoring signal whose potential varies depending on the current value applied from the drive circuit to the overcurrent protection circuit. The overcurrent protection circuit is provided to prevent excessive current from being applied to the load from the drive circuit. For example, the overcurrent protection circuit prevents the potential of the monitoring signal output from the current detection circuit from reaching a preset potential. If the current exceeds the current limit, a current control signal CL is output to the drive circuit. Note that the two-dot chain line in the figure is usually incorporated into the control device.

Next, the operation will be explained.

When information on changes in vehicle speed and vehicle height is output from various sensors to the arithmetic processing circuit, the arithmetic processing circuit controls the load of the motor, etc. that drives the variable-diameter orifice for oil flow control in the shock absorber. calculates various control signals and outputs the various control signals to the drive circuit. In response, the drive circuit begins applying the appropriate current to the load. At this time, the drive current is constantly monitored by a current detection circuit connected in series with the drive circuit, and a monitoring signal is output to the overcurrent protection circuit.
At this time, for example, if the overcurrent protection circuit detects that an overcurrent that is large enough to have an adverse effect on the load is applied, current control is performed to limit or cut off the drive current being applied to the load. Outputs signal CL. Accordingly, the drive current sent out from the drive circuit is limited or cut off, so that the load is not destroyed or damaged.

[Problem that the invention attempts to solve]

However, in such conventional load protection circuits, as shown in Figure 4, a current detection circuit connected in series with the load monitors the drive current sent from the drive circuit and detects overload. Since the configuration was such that a protection circuit, that is, an overcurrent protection circuit operates when current is detected, it is possible to protect against overcurrent caused by short circuits in the load, etc. However, current may continue to flow to the load due to a ground fault between the load and the control device. If such a situation occurs, there is a problem that the load cannot be protected from overcurrent.

This idea was created by focusing on these conventional problems, and by monitoring the voltage of the drive output terminal and cutting off the current supply to the load when an abnormality is detected in the voltage, the above-mentioned problem can be solved. The purpose is to solve problems.

[Means for solving problems]

The load protection circuit according to this invention includes an arithmetic processing circuit that performs arithmetic operations for load control according to input;
A drive circuit that outputs a load drive signal in accordance with an output of the arithmetic processing circuit, a load connected between an output terminal of the drive circuit and a power supply terminal, a state of a terminal voltage of the load, and the arithmetic processing circuit. an abnormality detection circuit that detects whether a predetermined relationship is maintained by comparing the output contents of the abnormality detection circuit, and a switching circuit that cuts off power supply to the load based on the abnormality detection output of the abnormality detection circuit. It is prepared.

[Effect]

In the load protection circuit of this invention, a load drive signal is output from the drive circuit to the load according to the output of the arithmetic processing circuit, and the terminal voltage of the load connected between the output terminal of the drive circuit and the power supply terminal is An abnormality detection circuit detects whether a predetermined relationship is maintained by comparing the state of It acts to cut off the power supply.

〔Example〕

This invention will be explained below based on the drawings.

1 and 2 are a block diagram and a circuit diagram showing an embodiment of this invention.

First, to explain the configuration, is an arithmetic processing circuit,
Input from various sensors that provides information on changes in vehicle speed and vehicle height
A control signal X for driving the load based on IN is output to the drive circuit and the abnormality detection circuit. The abnormality detection circuit monitors and compares the terminal voltage of the load, that is, the relationship between the voltage signal Y and the control signal X, and the relationship between the supply voltage data Z to the load and the control signal X (which can be set arbitrarily). If it is recognized that the relationship is inconsistent with the preset relationship, for example, if the control signal It recognizes it and outputs an abnormality detection signal AN to the switching circuit to cut off the power supply circuit BL. That is, the switching circuit cuts off power supply to the load based on the abnormality detection signal AN output from the abnormality detection circuit, and prevents overcurrent from flowing into the load.

The operation of cutting off the power supply to the load according to this invention will be explained below with reference to FIG.

FIG. 2 is a circuit diagram showing an example of the configuration of the switching circuit, drive circuit, and abnormality detection circuit shown in FIG. 1, and the same parts as in FIG. 1 are given the same reference numerals.

As shown in this figure, the switching circuit consists of transistors TR ₁ and TR ₂ and resistors R ₁ to _{R 4.} Power is supplied to the emitter of transistor TR ₁ , and transistor TR ₁ has a resistor connected to its base. Power is supplied to the load by turning on and off the transistor TR ₂ connected through the transistor R ₂ . The drive circuit consists of resistors R ₅ , R ₆ and transistors
_A control signal X ₍ point A
voltage signal Y (potential at point B) of the load connected to the collector of transistor TR ₃ .
is applied. The abnormality detection circuit is exclusive NOR gate EXNOR1, EXNOR2 and NOR gate NOR3.
The exclusive NOR gate _EXNOR1 takes the exclusive NOR between the potential data at point A and the potential data at point _B of the drive circuit, and outputs the exclusive NOR output EN1 to the subsequent NOR gate.
Output to one end of NOR3. exclusive noah gate
EXNOR2 takes the exclusive NOR between the potential data (power supply potential) at point C divided into logical potentials by resistors R ₇ and R ₈ and the potential data at point A, and outputs the exclusive NOR output EN2 to the subsequent stage. noah gate
Output to one end of NOR3. Noah Gate NOR3
takes the exclusive NOR of the exclusive NOR gates EN1 and EN2, and in a normal state, applies a "HIGH" level signal to the base of the transistor TR2, turns on _the transistor _TR2 , and supplies power to the load.

For example, when a control signal X is output from the arithmetic processing circuit to the drive circuit and power is supplied to the load,
The exclusive NOR gate EXNOR1 of the abnormality detection circuit monitors the potentials of points A and B, i.e.
Take the exclusive NOR between and the potential data of point B,
When both potential data are at positive logic level, exclusive NOR output EN1 is at “0” level (LOW
level). At this time, exclusive Noah Gate
EXNOR2 monitors the potential at points A and C,
In other words, if an exclusive NOR is performed with the potential data of points A and C, and both potential data are at a positive logic level, the exclusive NOR output EN2 is "0".
level (LOW level). Therefore, at this time, the inputs of the NOR gate NOR3, that is, the exclusive NOR outputs EN1 and EN2 are both at the "0" level,
NOR output EN3 becomes a positive logic level, turning on transistor _TR2 and supplying power to the load.

On the other hand, if a trouble such as a ground fault occurs between the terminals of the load, for example, if a ground fault occurs at point B while the control signal The exclusive NOR output EN1 becomes a positive logic level (HIGH level), and the NOR gate
The output of NOR3 becomes LOW level, turning off transistor _TR2 and cutting off the power supply to the load.

Similarly, if a trouble such as a ground fault occurs between the terminals of the load, for example, if a ground fault occurs at point C while the control signal The exclusive NOR output EN2 by EXNOR2 becomes a positive logic level (HIGH level), and the NOR gate
The output of NOR3 becomes LOW level, turning off transistor _TR2 and cutting off the power supply to the load.

In this way, the exclusive NOR gates EXNOR1 and EXNOR2 monitor the voltage between the terminals of the load and the presence or absence of sending the control signal The simple configuration of outputting to the switching circuit prevents overcurrent from flowing to the load even if trouble occurs between the load terminals.

[Effect of idea]

As explained above, according to this idea,
The configuration has been changed from the conventional configuration that detects the current flowing through the load and operates the protection circuit to a configuration that detects the state of the load side from the voltage applied to the drive circuit and operates the protection circuit. This allows the protection circuit to operate accurately against troubles that may occur on the load side, such as short-circuits, load short-circuits, ground faults and disconnections downstream of the load, and protects the load and control equipment from destruction and damage. .

In addition to the above-mentioned common effects, each embodiment has the following effects.

If voltage detection is performed only at the output terminal section in order to suppress cost increases, all troubles except short circuits in the load can be dealt with.

[Brief explanation of drawings]

Fig. 1 is a block diagram illustrating the configuration of a load protection circuit showing one embodiment of this invention, and Fig. 2 is a circuit diagram showing an example of the configuration of the switching circuit, drive circuit, and abnormality detection circuit shown in Fig. 1. , 3 and 4 are a block diagram and an explanatory circuit diagram showing a conventional load protection circuit. In the figure, is an arithmetic processing circuit, is a drive circuit, is a current detection circuit, is an overcurrent protection circuit,
is the load, is the abnormality detection circuit, and is the switching circuit.

Claims (1)

[Scope of utility model registration request] An arithmetic processing circuit that performs calculations for load control according to the input IN, a drive circuit that outputs a load drive signal according to the output of the arithmetic processing circuit, and between the output terminal of the drive circuit and the power supply terminal. a connected load, an abnormality detection circuit that compares the state of each terminal voltage of the load and the output content of the arithmetic processing circuit to detect whether a predetermined relationship is maintained; and the abnormality detection circuit. A load protection circuit comprising: a switching circuit that cuts off power supply to the load based on an abnormality detection output of the load protection circuit.