JPH11205995A - Protection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely operate protection to eliminate apparatus failures, by irregular operations corresponding to respective failures based on detected information received by a failure detecting means at the two ports provided on a microcomputer. SOLUTION: A microcomputer 1 receives an over-current information transmitted from an over-current detecting circuits 4, 5 from a protect input terminal port IN1 via a protection microcomputer interface 2 and also receives, from a protect input terminal port IN2, a DC detected voltage of the detection points DT1, DT2 such as DC output or the like of a DC amplifier of an audio power amplifier via a protection microcomputer interface 3 individually provided to have the similar function. Depending on the state signal such as received detected information or the like, state display such as ON/OFF of the load or stop of supply of power may be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit, and more particularly to a protection circuit having improved reliability of a protection function.

[0002]

2. Description of the Related Art A device constituent circuit such as a power amplifier or a power supply circuit of an audio device or the like is protected from a load or prevents damage to the constituent circuit when an overload is applied or an output abnormality is caused by a malfunction of the circuit itself. Therefore, the function of shutting off the load from the circuit or stopping the power supply, that is, the protection function is important.

An example of a protection circuit having such a function is shown in FIG. This protection circuit is
A microcomputer 11 for executing a predetermined control operation, a protection microcomputer interface 12, and an overcurrent detection circuit 1
3, 14 and a DC voltage detection circuit 15 for detecting the DC voltage at the detection points DT1 and DT2 such as the DC output of the DC amplifier of the audio power amplifier. The microcomputer 11 is supplied with power of +5 V, executes load interruption and power supply stop according to a state signal such as a current state and a voltage state received from the protection microcomputer interface 12, and displays a state such as an abnormal state. Is displayed on the display unit.

[0004] Protection microcomputer interface 1
2, a power supply + Vcc is supplied, and overcurrent information, which is an abnormal current detected by the overcurrent detection circuits 13 and 14 flowing to a predetermined portion of the device configuration circuit, is interface-processed via the protection microcomputer interface 12;
To send to. Similarly, the DC voltage at the detection points DT1 and DT2 is detected at 15 and sent to the microcomputer 11 via the protection microcomputer interface 12.

[0005] The microcomputer 11 sends a power supply relay control signal to a drive circuit such as a power supply or a relay for performing an ON / OFF operation of an output, based on the state information received via the protection microcomputer interface 12.
Outputs the speaker relay control signal,
A display signal for displaying various status information such as protection is transmitted to the display unit.

FIG. 5 is a specific circuit diagram of the protection circuit shown in FIG. A power of +5 V is supplied to the microcomputer 11, an LED as a display element is connected to the display output terminal, and a lighting display is performed based on the protection information input to the protection input terminal IN. As shown in the figure, the protection microcomputer interface 12
It comprises a diode, a transistor Q0, a resistor and a capacitor, and is connected to overcurrent detection circuits 14 and 15 via diodes D1 and D2, respectively. The cathode of the diode D1 or D2 is normally Hi, becomes Lo when there is an abnormality, the transistor Q0 is turned on, and the protection input terminal is made Hi to notify the abnormality.

[0007] The DC voltage detection circuit 15
Two transistors Q1, Q2, a resistor, and a capacitor are connected, and detection points DT1, DT2 are connected to the base of the transistor Q2 via resistors R1, R2 on the input side. When the detection point DT1 or DT2 is equal to or larger than the predetermined range value, the transistor Q2 turns on and the transistor Q0 turns on. In addition, the detection point DT1
Alternatively, when DT2 is equal to or less than a predetermined range, the transistor Q2 is turned on and the transistor Q0 is turned on. When the transistor Q0 is turned on and the protect input terminal is set to H
Inform i of abnormality.

The relay drive circuit 16 includes a microcomputer 11
The control signal output from the relay control output terminal OUT is output to the base of the transistor Q3 on the basis of the protection information input to the protection input terminal IN, and a current flows through a relay coil connected in parallel with a diode to operate the relay. It drives to cut off the load or stop the power supply.

[0009]

In the above-mentioned conventional protection circuit, since there is only one input terminal port for receiving the protection information for protection to be taken into the microcomputer 11, the common input is used for overcurrent detection and voltage detection. The voltage must be taken from the terminal, and voltage detection is not performed for several seconds when the power is turned on until the circuit operation is stabilized. As a result, if the output stage of the power amplifier fails due to a short circuit or the like, the protection function works once, but when the power is turned on again, the protection function does not work for a few seconds, so an abnormal current flows while the primary fuse blows. There is a problem that a dangerous state such as ignition or smoke is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a protection circuit in which a protection function works reliably and there is no risk of device failure.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a protection circuit according to the present invention receives detection information from abnormality detection means for detecting at least two abnormality states at a port provided in a microcomputer, and detects the information. A protection circuit for executing an operation corresponding to each of the abnormalities based on the abnormal information, wherein the microcomputer is provided with at least two ports for respectively receiving the detection information by the at least two abnormality detection means;
It is configured to execute an abnormality countermeasure operation corresponding to each abnormality based on the detection information received at one port.

The abnormality detecting means includes an overcurrent detecting circuit for detecting an overcurrent and a voltage detecting circuit for detecting a voltage.
According to the detection state detected by the detection circuit, a state display such as a load cutoff, a power supply stop, and an abnormal state is performed.

A protection circuit according to another aspect of the present invention receives detection information from circuit state detection means for detecting at least two circuit states at a port provided in a microcomputer, and responds based on the detected circuit state information. In the protection circuit for performing the operation of performing at least two A / Ds, the microcomputer is provided with at least two A / D ports for respectively receiving circuit information by the at least two circuit state detecting means.
Performs an operation based on the circuit state information received at the port,
As a result of the calculation, when it is determined that the state is abnormal, an abnormality countermeasure operation corresponding to each abnormality is executed.

The circuit state detecting means is a circuit voltage state detecting circuit for detecting a circuit voltage, and according to a result of an operation based on the detection circuit information, a state display such as a load cutoff, a power supply stop, an abnormal state, and the like. Execute

In the display, the lighting state is changed according to the abnormal state, such as lighting, blinking, blinking interval, and blinking duty.

[0016]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of a protection circuit according to the present invention.

The protection circuit according to the present embodiment comprises:
The microcomputer 1 has the same basic configuration as that of FIG. 4, and the microcomputer 1 receives the overcurrent information sent from the overcurrent detection circuits 4 and 5 via the protection microcomputer interface 2 and is separately provided with the same function. Detection points DT1, such as the DC output of the DC amplifier of the audio power amplifier, via the protection microcomputer interface 3 provided.
The DC detection voltage of DT2 is being received. The microcomputer 1
In accordance with status signals such as overcurrent information and voltage status, which are abnormal currents received via the protection microcomputer interfaces 2 and 3, status display such as load shutoff, power supply stop, and abnormal status is executed.

As described above, in the present embodiment, two systems of the protection detection ports 2 and 3 for operating the protection function are provided, one for overcurrent detection and the other for the voltage detection circuit. In addition, overcurrent detection of the microcomputer operation is always performed (detection is performed immediately after the power of a power amplifier or the like is turned on), and voltage detection is performed until the circuit operation is stabilized (after several seconds) after the power is turned on. .

When the protection circuit detects an abnormal state, the microcomputer 1 turns off the power ON / OFF relay and the like, and turns OFF the output ON / OFF relay and the like. Also, a display signal for displaying various state information such as protection is transmitted to the display unit.

FIG. 2 is a specific circuit diagram of the protection circuit shown in FIG. The basic configuration of this circuit is the same as that of FIG. 5. The microcomputer 1 receives power supply of +5 V, connects an LED as a display element to a display output terminal, and protects the protection input terminal ports IN1 and IN2. A predetermined display such as lighting or blinking is performed based on the information. The protection microcomputer interface 2
It is composed of a diode, a transistor Q0, a resistor, and a capacitor, and 4, 5 are connected via diodes D1 and D2, respectively. The operation of each unit is the same as that of the conventional protection microcomputer interface 12.

The DC voltage detection circuit 6 is connected to two transistors Q1 and Q2, a resistor and a capacitor, and the detection points DT1 and DT2 are connected to the base of the transistor Q2 via the input-side resistors R1 and R2. . The protection microcomputer interface 3 includes a transistor Q4, a resistor, and a capacitor. The collectors of the transistors Q1 and Q2 on the output side of the DC voltage detection circuit 6 are connected to the base of the transistor Q4. The operation of each section is the same as that of the DC voltage detection circuit 15 of the conventional example, and the function of the transistor Q0 is replaced by the transistor Q4.

The relay drive circuit 7 outputs a control signal output from the relay control output terminal to the base of the transistor Q3 based on the protection information input to the protection input terminals IN1 and IN2, thereby connecting the diodes in parallel. A current is supplied to the relay coil to drive the relay.

In the above, each abnormality detection circuit is connected to the protection IN1 and IN2 via the transistors Q0 and Q4, and operates correspondingly.

Next, the two protection detection ports of the microcomputer are set as AD ports, and the microcomputer interface circuit changes the potential and amplitude of the signal of the detection unit linearly within the input voltage range of the AD port, thereby protecting the protection target. It is possible to protect against overcurrent, abnormal voltage and excess power dissipation.

FIG. 3 shows an example of a protection circuit for protecting a control transistor of a stabilized power supply using an AD port according to the present invention. In the transistor Q11, an input voltage source is supplied to a collector side, a control circuit 21 is connected to a base, and a load 22 is connected to an emitter on the output side via a resistor R11.

The voltage detection interface circuit 23 is supplied with the collector voltage and the emitter voltage of the transistor Q11, detects the collector-emitter voltage of the transistor Q11, and detects an A / D port (voltage detection input port) of the microcomputer 25. Output to Further, the current detection interface circuit 24 is supplied with the emitter on the output side of the transistor Q11 and the voltage on the output side of the resistor R11 connected to the emitter, and outputs the voltage across the resistor R11 (in other words, the resistor R11). R11, that is, transistor Q1
1) for A / D of the microcomputer 25.
Output to the port (current detection input port).

In the protection circuit using the A / D port, the output of the microcomputer interface circuit is connected to the A / D port.
By making it change linearly within the input range of the port, it is possible to protect the protection target from excess of allowable loss other than overcurrent and abnormal voltage.

Here, the collector loss of the transistor is
PC = VCE × IC, where VCE is the voltage of the voltage detection input A / D port, and IC is the current detection input A / D
Calculated from port voltage. Therefore, microcomputer 2
5 performs arithmetic processing based on the input voltage of each A / D port, and when the result exceeds a specified value, activates the protection circuit as an output.

According to the circuit according to the above-described embodiment, overcurrent protection, protection against abnormal input voltage, protection against excessive collector loss, and protection conditions against load inrush and steady current can be separately set by a microcomputer program.

Further, since the processing is performed based on the calculation result of the detected voltage and current, the operation is performed more accurately and only when necessary than when only one of them is operated.

As described above, in the protection circuit of the present invention, when an abnormal state (for example, overcurrent) is detected immediately after the power is turned on, the protection state can be set. There is no danger of falling into a dangerous state. In addition, when the power amplifier or the like breaks down, in order to confirm that the user is abnormal, the power supply
Although the N / OFF operation is repeated and a wasteful operation is performed, in the present invention, an abnormal state or a failure state of the apparatus can be notified by visual recognition of a display device, a speaker (buzzer) or the like, or an audio alarm, so that the apparatus can be promptly notified. Action can be taken.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications are possible. That is, in the above-described embodiment, two protection ports of the microcomputer are provided. However, if more protection ports are provided and the detection contents are associated with each system, that is, FIG.
In the circuit shown in FIG. 5, in addition to the detecting means for detecting the abnormality of the input voltage applied to the control transistor Q11 and the overcurrent,
It is also possible to provide means for detecting other abnormal states, receive the detected information at the protection port of the microcomputer corresponding to these means, and perform appropriate control based on each detected information.

In a display device for displaying a protection state, for example, when only one display element LED is provided, the lighting state of the LED is changed according to the abnormal state, for example, lighting, blinking, blinking interval, and the like. By changing the blinking duty, it is possible to visually recognize whether the protection is the overcurrent protection or the DC voltage protection.

[0034]

As described above, according to the present invention, it is possible to provide a protection circuit in which the protection function works reliably and there is no risk of device failure.

[Brief description of the drawings]

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

FIG. 2 is a specific circuit diagram of the protection circuit shown in FIG.

FIG. 3 is an example of a protection circuit for protecting a control transistor of a stabilized power supply as an application example of the present invention.

FIG. 4 is a configuration diagram of a conventional protection circuit.

FIG. 5 is a specific circuit diagram of the conventional protection circuit shown in FIG.

[Description of Signs] 1, 11, 25 Microcomputer 2, 3, 12 Protection microcomputer interface 4, 5, 13, 14 Overcurrent detection circuit 6, 15 DC voltage detection circuit 7, 16 Relay drive circuit 21 Control circuit 22 Load 23 Voltage Interface for detection 24 Interface for current detection

Claims (5)

[Claims] 1. A protection circuit for receiving detection information from an abnormality detecting means for detecting at least two abnormal states at a port provided in a microcomputer and executing an operation corresponding to each abnormality based on the detected abnormality information. In the above, the microcomputer is provided with at least two ports for respectively receiving the detection information by the at least two abnormality detection means, and executes an abnormality countermeasure operation corresponding to each abnormality based on the detection information received at the at least two ports. A protection circuit characterized in that: 2. The abnormal condition detecting means includes an overcurrent detecting circuit for detecting an overcurrent, and a voltage detecting circuit for detecting a voltage.
The protection circuit according to claim 1, wherein a state display such as a cutoff of a load, a stop of power supply, an abnormal state, or the like is executed according to a detection state detected by the detection circuit. 3. A protection circuit for receiving detection information from circuit state detection means for detecting at least two circuit states at a port provided in a microcomputer and executing a corresponding operation based on the detected circuit state information. The microcomputer is provided with at least two A / D ports for respectively receiving circuit information from the at least two circuit state detecting means, and the microcomputer performs an operation based on the circuit state information received at the at least two A / D ports. A protection circuit for performing an abnormality countermeasure operation corresponding to each of the abnormalities when it is determined as a result of the operation that the state is abnormal. 4. The circuit state detecting means is a circuit voltage state detecting circuit for detecting a circuit voltage. The circuit state detecting means detects a load interruption, a power supply stop, an abnormal state or the like in accordance with a result of an operation based on the detection circuit information. 4. The protection circuit according to claim 3, wherein a status display is performed. 5. The protection circuit according to claim 2, wherein the display changes a lighting state according to the abnormal state, such as lighting, blinking, blinking interval, and blinking duty.