JPS6213108A - Protecting device - Google Patents

Abstract

PURPOSE:To protect an amplifier circuit by providing an adder circuit adding output signals of the amplifier circuit and a phase comparator comprising the output signal of the amplifier and the output signal of the adder circuit so as to disconnect a relay of the grounded load side when the load is grounded. CONSTITUTION:An output waveform of amplifier circuits 12, 13 is in-phase and opposite phase sinusoidal waves amplified by A times. The phase comparator circuits 21, 22 are designed that an output voltage goes to a high level when the in-phase signal is inputted. if an output terminal 18 is at a grounding potential due to a fault of a connected cable and load, the input to the adder circuit 20 is only a signal from an output terminal 19. Since the 2-input signal of the phase comparator 22 is in the relation of in-phase, the output voltage goes to a high level, a relay 16 is disconnected to change over the amplification factor of the amplifier 13 into double. The substantial output voltage between output terminals 18 and 19 is the same when the output terminals 18, 19 are operated normally.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an output protection device for an amplifier circuit or the like having a balanced output, which is used in the commercial field.

BACKGROUND OF THE INVENTION In recent years, the two-transformer type has been replaced with a transistor type as the output of an amplifier circuit having a balanced output. At that time, a problem arises when the load is shorted.

An example of the above-mentioned conventional balanced output amplifier circuit will be described below with reference to all the drawings. FIG. 2 shows a conventional circuit configuration. In the figure, 1 is an input terminal of an amplifier circuit, and 2 and 3 are non-inverting inputs.

An amplifier circuit having an inverting input terminal, 4 and 5 are amplifier circuits 2,
3 is the output protection resistor, 6.7 is a relay that intermits the output signal, and is mainly used to turn on the power of the device.

This is to prevent an abnormal signal from being output to the output when switching to OFF. Reference numerals 8 and 9 are output terminals, which have opposite phases to each other. Now, if the load on one side is short-circuited for some reason, for example, if the output terminal 8 is grounded, the load on the amplifier circuit 2 will be only the resistor 4, and if the resistance value is small, the amplifier will malfunction. becomes. In order for this circuit configuration to work properly, the resistance value of resistor 4 must be increased, or
A method of providing a current limiting circuit in the amplifier circuit 2 is used.

Problems to be Solved by the Invention However, when the resistance value of the resistor 4 is increased, the output voltage that can be taken out to the output terminal 8 in a normal state becomes smaller, resulting in poor utilization efficiency for the power supply electrician. Further, when a current limiting circuit is provided, there are problems in that distortion becomes sensitive when the current limiting circuit starts working, and that it affects the other amplifier circuit 3 through the ground line of the circuit.

Means for Solving the Problems In order to solve the above problems, the protection device of the present invention includes an adder circuit that adds the output signals of the amplifier circuits, and compares the output signals of the amplifier circuits with the output signals of the adder circuits. It is equipped with a phase comparator.

Operation The present invention uses the above-described configuration to protect the amplifier circuit by using the output signal of the phase comparator when one load is grounded due to some influence, and at the same time protects the amplifier circuit by using the output signal of the phase comparator. By increasing the amplification degree of the amplifier circuit, the output voltage can be kept unchanged.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a protection device according to the present invention.

In FIG. 1, 11 is an input terminal, 12.13 is an amplifier circuit each having a non-inverting input and 2 inverting input terminals, 14.15 is an output protection resistor of the amplifier circuit 12.13, 16.17 is a relay that cuts off the output, 18.19 is an output terminal, 20 is an adder circuit, 21.22 is a phase detection circuit, and these outputs are
It controls relays 16 and 17 and also switches the amplification degrees of amplifier circuits 12 and 13.

In the circuit block configured as above, the first
The operation will be explained using figures.

Assume that a sine wave is input to the input terminal 11 in FIG. The output waveforms of the amplifier circuits 12 and 13 become in-phase and anti-phase sine waves that are multiplied by M. If the values of the output protection resistors 14 and 15 are the same and the values of the load resistors 18 and 19 are also the same, a signal of opposite phase will be input to the input of the adder circuit 20, and its output will be DC. If the phase comparators 21 and 22 are designed so that the output voltage becomes high level when the in-phase signal is input, in this case, since the output of the adder circuit 20 is DC, the output of the phase comparators 21 and 22 remains at low level, and input terminal 11
The input signal is amplified and output to the 18°19 output terminal.

Next, due to an abnormality in the connected cable or load, the output terminal 18
Considering the case where becomes the ground potential, adder circuit 2
The 0 input is only the signal from the output terminal 19, the output waveform is in phase with the output waveform of the amplifier circuit 13, and the amplitude is at a level divided by the output protection resistor 16 and the load resistor. This signal enters the phase comparators 21 and 22, but since the two signals from the phase comparator 21 are in opposite phases to each other, the output of the phase comparator 21 remains at a low level. Phase comparator 22
Since the two human power signals are in phase, the output voltage becomes high level, and this control signal turns off the relay 16 and switches the amplification degree of the amplifier 13 to double it, which causes the output voltage to reach the output terminal 18.
．． The actual output voltage between terminals 18 and 19 is the same as when the output terminals 18 and 19 are working normally, and the subsequent devices can be operated without any hindrance. 6 '- Conversely, if the output terminal 19 becomes the ground potential, the output voltage of the phase comparator 21 becomes . Give it twice as much,
The output level between the output terminals 18 and 19 is the same as when it is normal. Note that this circuit configuration does not depend on the value of the load resistance, and any device that has a balanced input may be used.

Effects of the Invention As described above, the present invention provides an adder circuit and a phase comparator separately, so that when either load is grounded, the relay on the grounded load side is turned off to protect the amplifier circuit. At the same time, the amplification degree of the other amplifier circuit is doubled, so it can be used with confidence. Furthermore, since the output protection resistance of the amplifier circuit does not need to be made large, there is little signal amplitude loss outside the protection resistance, and the signal can be effectively supplied to the load.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a protection device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional protection device. 7... 11... Input terminal, 12.13... Each non-inverting and inverting amplifier circuit, 14.15... Protection resistor, 16.17... Relay, 18.19...
...Output terminal, 2o...Addition circuit, 21.22
・・・・・・Phase comparator.

Claims (1)

[Claims] An amplifier circuit that has a balanced output terminal and can switch the amplification level, a relay that continues the output, an adder circuit that adds the signal taken out after the relay, and the output signal of the amplifier circuit and the output of the adder circuit. It is equipped with a comparator that compares the phase of signals, and when one output of the balanced output terminals is grounded, that output relay is turned OFF and the amplification degree of the other amplifier circuit is increased, causing a change in the output signal. A protective device that prevents