JP2011229099A - Power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the presence of a state in which a D.C. voltage is to be supplied and place a main power supply circuit in a continuously turned-off state.SOLUTION: When a positive D.C. voltage is supplied, a transistor Q1 is placed in a turned-on state, and a transistor Q3 is placed in a turned-on state. A transistor Q4, to whose base a sub-power supply voltage Vs is supplied, is placed in a turned-on state. A transistor Q5, whose base is placed in a state of being connected to a ground potential, is placed in a turned-off state. As a result, the sub-power supply voltage Vs from a sub-power supply circuit 6 is no longer supplied to a coil 5a, and a relay switch 5b is placed in a turned-off state. Therefore, a main power supply circuit 7 is placed in a turned-off state, and outputting of a positive D.C. voltage to a loudspeaker is obstructed. When the transistor Q3 is placed in a turned-on state, the sub-power supply voltage Vs is supplied to the base of the transistor Q1 via a diode D3, and the transistor Q1 maintains a turned-on state irrespective of the output voltage to the loudspeaker.

Description

  The present invention relates to a power supply control device that controls a main power supply circuit to an off state when it is determined that a DC voltage is supplied.

  In the amplifying apparatus, if a direct current (DC) voltage is supplied from the amplifier circuit to a speaker as a load due to damage of a transistor of the amplifier circuit, the speaker may be damaged. In order to prevent this problem, a power supply control device that detects a state in which a DC voltage is supplied from the amplifier circuit to the speaker and controls the main power supply circuit to an off state is provided. In an amplifying apparatus including a microcomputer, when a state in which a DC voltage is supplied from an amplifier circuit to a speaker is detected, the microcomputer turns off a relay switch for the main power supply circuit and maintains this state, whereby the main power supply The circuit is turned off so that no DC voltage is supplied to the speaker, and the speaker is prevented from being damaged. However, in an amplifying apparatus that does not include a microcomputer, if the detection circuit detects a state in which a DC voltage is supplied from the amplifier circuit to the speaker, the relay switch of the main power circuit is turned off, but the amplifier circuit does not supply a DC voltage to the speaker. As soon as the state where the power is supplied is not detected, the relay switch of the main power supply circuit is turned on. Accordingly, when the detection circuit detects again that the DC voltage is supplied from the amplifier circuit to the speaker, the relay switch of the main power supply circuit needs to be turned off again. Therefore, there arises a problem that the relay switch of the main power supply circuit frequently repeats the on state and the off state, and the main power supply circuit frequently repeats the on state and the off state.

JP 2002-51453 A JP 2002-368550 A

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to detect a state in which a DC voltage is supplied and to continuously turn off the main power supply circuit. Is to provide.

  A power supply control device according to a preferred embodiment of the present invention includes a first transistor that detects a state in which a positive DC voltage is supplied, a second transistor that detects a state in which a negative DC voltage is supplied, and a positive DC voltage. Is turned on when the first transistor detects a state in which the first transistor is supplied, or when the second transistor detects a state in which a negative DC voltage is supplied, the sub power supply voltage is supplied to the main power supply control circuit and When the first transistor does not detect a state in which a positive DC voltage is supplied and the second transistor does not detect a state in which a negative DC voltage is supplied, the transistor is turned off. A third transistor that does not supply a sub power supply voltage to the main power supply control circuit and the sustain circuit; and a sub power supply voltage when the third transistor is in an ON state. The main power supply control circuit which controls the main power supply circuit to be turned off by controlling the main power supply circuit to be turned off by supplying the sub power supply voltage when the third transistor is turned off. And a sustain circuit for continuously detecting a state in which a positive DC voltage is supplied by supplying a sub power supply voltage to the first transistor when the third transistor is in an on state; Is provided.

  When a state in which a positive DC voltage is supplied is detected, or when a state in which a negative DC voltage is supplied is detected, a state in which a positive DC voltage is supplied is continuously detected by the first transistor. Thus, the main power supply circuit can be continuously turned off.

  A power supply control device according to a preferred embodiment of the present invention includes a first transistor that detects a state in which a positive DC voltage is supplied, and an ON state when the first transistor detects a state in which a positive DC voltage is supplied. The sub power supply voltage is supplied to the main power supply control circuit and the sustain circuit, and when the first transistor does not detect a state in which a positive DC voltage is supplied, the sub power supply voltage is turned off. A third transistor not supplied to the circuit and the sustain circuit, and a sub power supply voltage is supplied when the third transistor is in an on state, thereby controlling the main power supply circuit in an off state, and the third transistor in an off state. In this case, the main power supply control circuit that controls the main power supply circuit to be turned on by not supplying the sub power supply voltage, By supplying a sub-power supply voltage to the first transistor when the third transistor is on, and a the sustain circuit in which a positive DC voltage to continuously detect the condition to be supplied to the first transistor.

  When the state in which the positive DC voltage is supplied is detected, the main power supply circuit can be continuously turned off by causing the first transistor to continuously detect the state in which the positive DC voltage is supplied. .

  In a preferred embodiment, the sustain circuit includes a diode having an anode connected to one of the electrodes of the third transistor and a cathode connected to one of the electrodes of the first transistor.

  By supplying the sub power supply voltage to one of the electrodes of the first transistor through the diode, the first transistor can continuously detect a state in which a positive DC voltage is supplied.

  A power supply control device according to a preferred embodiment of the present invention includes a second transistor that detects a state in which a negative DC voltage is supplied, and an ON state when the second transistor detects a state in which a negative DC voltage is supplied. The sub power supply voltage is supplied to the main power supply control circuit and the sustain circuit, and is turned off when the second transistor does not detect a state in which a negative DC voltage is supplied, and the sub power supply voltage is controlled by the main power supply control. A third transistor not supplied to the circuit and the sustain circuit, and a sub power supply voltage is supplied when the third transistor is in an on state, thereby controlling the main power supply circuit in an off state, and the third transistor in an off state. In this case, the main power supply control circuit that controls the main power supply circuit to be turned on by not supplying the sub power supply voltage, By the third transistor supplies the sub-power supply voltage to the second transistor when the ON state, and a the sustain circuit continuously to detect the state where the negative DC voltage is supplied to the second transistor.

  When the state in which the negative DC voltage is supplied is detected, the main power supply circuit can be continuously turned off by causing the second transistor to continuously detect the state in which the negative DC voltage is supplied. .

  It is possible to provide a power supply control device capable of detecting a state in which a DC voltage is supplied and continuously turning off the main power supply circuit.

1 is a circuit diagram illustrating a power supply control device according to a preferred embodiment of the present invention. 1 is a circuit diagram illustrating a power supply control device according to a preferred embodiment of the present invention. 1 is a circuit diagram illustrating a power supply control device according to a preferred embodiment of the present invention. 1 is a circuit diagram illustrating a power supply control device according to a preferred embodiment of the present invention. 1 is a circuit diagram illustrating a power supply control device according to a preferred embodiment of the present invention.

[Example 1]
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to these embodiments. FIG. 1 is a schematic circuit diagram showing a main part of an amplification device 1 to which a power supply control device according to a preferred embodiment of the present invention is applied.

  The amplifying apparatus 1 includes a detection circuit 2, a maintenance circuit 3, a main power supply control circuit 4, and a relay circuit 5.

  The detection circuit 2 detects a state in which a positive direct current (DC) voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker (load). Specifically, it is detected that the level (amplitude value) of the point A voltage in FIG. 1 is equal to or higher than a first predetermined value. The first predetermined value is a positive value and is not particularly limited, but is, for example, + 12V. The detection circuit 2 detects a state in which a negative direct current (DC) voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker. Specifically, it is detected that the level (amplitude value) of the voltage at point A in FIG. 1 is equal to or lower than a second predetermined value. The second predetermined value is a negative value and is not particularly limited, but is −12V, for example.

  The detection circuit 2 includes resistors R0 to R3, transistors Q1 to Q3, diodes D1 and D2, and a capacitor C1. One end of the resistor R1 is connected to an audio output terminal (that is, an output of the amplifier circuit) to the speaker, the other end is connected to the ground potential via the capacitor C1, and the anode of the diode D1 and the emitter of the transistor Q2 It is connected to the. The resistor R0 is connected in parallel with the capacitor C1.

  The transistor Q1 is a transistor that detects a state in which a positive DC voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker. The transistor Q1 has a base connected to a connection point between the cathode of the diode D1 and the resistor R4, an emitter connected to the ground potential, and a collector connected to a connection point between the collector of the transistor Q2 and the resistor R2. When the transistor Q1 is in a state in which a positive DC voltage is supplied from the amplifier circuit of the amplifying apparatus 1 to the speaker, that is, when the point A voltage is equal to or higher than the first predetermined value, the base-emitter voltage is conductive. It becomes more than the start voltage and turns on.

  The transistor Q2 is a transistor that detects a state in which a negative DC voltage is supplied from the amplifier circuit of the amplifying apparatus 1 to the speaker. The transistor Q2 has a base connected to the cathode of the diode D2, an emitter connected to a connection point between the resistor R1, the capacitor C1, and the anode of the diode D1, and a collector connected to a connection point between the collector of the transistor Q1 and the resistor R2. ing. The anode of the diode D2 is connected to the ground potential. When the transistor Q2 is in a state in which a negative DC voltage is supplied from the amplifier circuit of the amplifying apparatus 1 to the speaker, that is, when the point A voltage is equal to or lower than the second predetermined value, the base-emitter voltage is conductive. It becomes more than the start voltage and turns on.

  The resistor R1 and the capacitor C1 constitute a time constant circuit, and when an audio signal having a large amplitude value is supplied from the amplifier circuit to the speaker, the voltage at the point A is greater than or equal to a first predetermined value by the audio signal, or the second Preventing it from being below a predetermined value. In other words, since the audio signal from the amplifier circuit is an AC voltage and the amplitude value changes to positive and negative values as needed, the voltage at which the point A voltage turns on the transistors Q1 and Q2 due to the influence of the time constant circuit. Not reach. On the other hand, in a state where the DC voltage from the amplifier circuit is continuously supplied to the speaker, the time constant circuit reaches the voltage at which the point A voltage reaches the voltage for turning on the transistor Q1 or Q2 after a predetermined time.

  The transistor Q3 is a transistor that switches whether the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the sustain circuit 3 and the main power supply control circuit 4 in accordance with the on state or the off state of the transistors Q1 and Q2. The transistor Q3 has an emitter connected to the sub power supply circuit 6 and supplied with a sub power supply voltage Vs, and is connected to a connection point between the base of the transistor Q3 and the resistor R2 via the resistor R3, and a collector connected to the anode of the diode D3. The base is connected to the connection point between the resistors R2 and R3. When the transistor Q1 or Q2 is turned on, the transistor Q3 is connected to the ground potential and turned on, and supplies the sub power supply voltage Vs to the main power supply control circuit 4. On the other hand, when the transistors Q1 and Q2 are both in the off state, the transistor Q3 is turned off when the sub power supply voltage Vs is supplied to the base, and the supply of the sub power supply voltage Vs to the main power supply control circuit 4 is cut off. .

  When the detection circuit 2 detects that the positive DC voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker, the maintenance circuit 3 is independent of the voltage value supplied from the amplifier circuit to the speaker. The detection circuit 2 is continuously detected that a positive DC voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker. Further, when the detection circuit 2 detects a state in which a negative DC voltage is supplied from the amplifier circuit of the amplification device 1 to the speaker, the maintenance circuit 3 is independent of the voltage value supplied from the amplification device 1 to the speaker. The detection circuit 2 continuously detects that a positive DC voltage is being supplied from the amplifier circuit of the amplification device 1 to the speaker.

  The sustain circuit 3 has a diode D3 and a resistor R4. The anode of the diode D3 is connected to the connection point between the collector of the transistor Q3 and the resistor R5, and the cathode is connected to the connection point between the base of the transistor Q1 and the cathode of the diode D1 through the resistor R4. When the transistor Q3 is turned on, the diode D3 supplies the sub power supply voltage Vs to the base of the transistor Q1 via the resistor R4, thereby maintaining the transistor Q1 in the on state. As a result, the transistor Q3 is turned on. To maintain.

  The relay circuit 5 includes a coil 5a and a relay switch 5b. When the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the coil 5a, the relay switch 5b is turned on, and the main power supply circuit 7 is connected to commercial AC. Power is supplied to turn on the main power supply circuit 7. When the main power supply circuit 7 is turned on, the main power supply voltage Vm is supplied to the amplifier circuit or the like, so that the amplifier circuit supplies an audio signal (a DC voltage when the amplifier circuit is damaged) to the speaker. On the other hand, in the relay circuit 5, when the sub power supply voltage Vs is not supplied to the coil 5a, the relay switch 5b is turned off, the supply of commercial AC power to the main power supply circuit 7 is cut off, and the main power supply circuit 7 is turned off. Let me. When the main power supply circuit 7 is turned off, the main power supply voltage Vm is not supplied to the amplifier circuit or the like, so the amplifier circuit does not supply an audio signal (DC voltage when the amplifier circuit is damaged) to the speaker. The on / off control of the relay switch 5b is normally controlled by the transistor Q6.

  The main power supply control circuit 4 controls the on and off states of the relay switch 5b of the relay circuit 5 according to whether or not the sub power supply voltage Vs is supplied from the detection circuit 2, and the on and off states of the main power supply circuit 7 To control. When the transistor Q3 is on and the sub power supply voltage Vs is supplied, the main power supply control circuit 4 causes the coil 5a to supply the sub power supply voltage Vs from the sub power supply circuit 6, and as a result, turns on the relay switch 5b. Let me. On the other hand, when the transistor Q3 is in the off state and the sub power source voltage Vs is not supplied, the sub power source voltage Vs is not supplied from the sub power source circuit 6 to the coil 5a, and as a result, the relay switch 5b is turned off.

  Main power supply control circuit 4 includes resistors R5 and R6, and transistors Q4 and Q5. The transistor Q4 is a transistor that controls on / off of the transistor Q5 according to whether or not the sub power supply voltage Vs is supplied. The base of the transistor Q4 is connected to the connection point between the collector of the transistor Q3 and the anode of the diode D3 via the resistor R5, and is connected to the ground potential via the resistor R6, and the emitter is connected to the ground potential. Is connected to the base of transistor Q5. The transistor Q5 is turned off to open the coil 5a with respect to the ground potential, and the sub power supply voltage Vs is not supplied to the coil 5a, and the transistor Q5 is turned on to place the coil 5a connected to the ground potential. The sub power supply voltage Vs is supplied to the coil 5a. The base of the transistor Q5 is connected to the collector of the transistor Q4, the emitter is connected to the ground potential, and the collector is connected to the coil 5a.

The operation of this embodiment will be described.
[Normal operation]
When the amplifier circuit of the amplification device 1 is not damaged, a positive DC voltage or a negative DC voltage is not supplied from the amplifier circuit to the speaker and the detection circuit 2. In addition, an audio signal (AC voltage) supplied from the amplifier circuit to the speaker is supplied to the detection circuit 2, but the point A voltage does not exceed the first predetermined value by the time constant circuit, and the second predetermined voltage is supplied. Not less than the value. Therefore, since the voltage at the point A is less than the first predetermined value and larger than the second predetermined value (greater than -12V and less than + 12V), the transistors Q1 and Q2 are both turned off. . As a result, the transistor Q3 is in a state in which the sub power supply voltage Vs is supplied to the base, and is in an off state. Since the transistor Q3 is in the off state, the sub power supply voltage Vs is not supplied to the base of the transistor Q4 and is in the off state. The transistor Q5 is in a state where the base is released from the ground potential and is in an on state. As a result, the sub power source voltage Vs from the sub power source circuit 6 is supplied to the coil 5a, and the relay switch 5b is turned on. It is in a state. Therefore, the main power supply circuit 7 is in an on state, and the audio signal from the amplifier circuit is output to the speaker.

[When a positive DC voltage is supplied, that is, when the voltage at point A is equal to or higher than a first predetermined value]
When a positive DC voltage is supplied from the amplifier circuit to the detection circuit 2, the point A voltage gradually increases, and after a predetermined time determined by the time constant circuit, the point A voltage is equal to or higher than a first predetermined value (approximately + 12V). become. Accordingly, the transistor Q1 is turned on and the transistor Q2 is turned off. As a result, the transistor Q3 is in a state where the base is connected to the ground potential and is turned on. When the transistor Q3 is turned on, the sub power supply voltage Vs is supplied to the base of the transistor Q4, and the transistor Q4 is turned on. Transistor Q5 has its base connected to the ground potential and is turned off. As a result, the sub power supply voltage Vs from the sub power supply circuit 6 is not supplied to the coil 5a, and the relay switch 5b is turned off. Therefore, the main power supply circuit 7 is turned off, and a positive DC voltage is prevented from being supplied from the amplifier circuit to the speaker, so that the speaker can be prevented from being damaged. Here, when the transistor Q3 is turned on, the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the base of the transistor Q1 via the diode D3 and the resistor R4, so that it is supplied from the amplifier circuit to the speaker. Regardless of the voltage value, the transistor Q1 is kept on. Therefore, the relay switch 5b can be continuously turned off and the main power supply circuit 7 can be continuously turned off.

[When a negative DC voltage is supplied, that is, when the voltage at point A is equal to or lower than a second predetermined value]
When a negative DC voltage is supplied to the detection circuit 2 from the amplifier circuit, the point A voltage gradually decreases, and after a predetermined time determined by the time constant circuit, the point A voltage is a second predetermined value (approximately -12 V). It becomes the following. Accordingly, the transistor Q2 is turned on and the transistor Q1 is turned off. As a result, the transistor Q3 is in a state where the base is connected to the ground potential and is turned on. When the transistor Q3 is turned on, the sub power supply voltage Vs is supplied to the base of the transistor Q4, and the transistor Q4 is turned on. Transistor Q5 has its base connected to the ground potential and is turned off. As a result, the sub power supply voltage Vs from the sub power supply circuit 6 is not supplied to the coil 5a, and the relay switch 5b is turned off. Therefore, the main power supply circuit 7 is turned off, and a negative DC voltage is prevented from being supplied from the amplifier circuit to the speaker, so that the speaker can be prevented from being damaged. Here, when the transistor Q3 is turned on, the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the base of the transistor Q1 via the diode D3 and the resistor R4, so that it is supplied from the amplifier circuit to the speaker. Regardless of the voltage value, the transistor Q1 is kept on. Therefore, the relay switch 5b can be continuously turned off and the main power supply circuit 7 can be continuously turned off.

  As described above, according to the present embodiment, when a state in which a positive DC voltage or a negative DC voltage is supplied from the amplifier circuit to the speaker is detected by the function of the diode D3, the relay switch 5b is continuously thereafter. Can be turned off, and the main power supply circuit 7 can be turned off continuously.

[Example 2]
FIG. 2 is a circuit diagram illustrating a main part of the amplifying device 11 to which the power supply control device according to the present embodiment is applied. In the present embodiment, the main power supply control circuit 4 is changed to a second main power supply control circuit 8 as compared with the first embodiment. The second main power supply control circuit 8 has diodes D4 and D5. When the transistor Q3 is in the ON state, the sub power supply voltage Vs is supplied, and the sub power supply circuit 6 is set to the ground potential via the diodes D4 and D5. By connecting, the sub power supply voltage Vs is lowered to a predetermined voltage. The predetermined voltage is a voltage at which the relay switch 5b is turned off and the transistor Q1 can be turned on, and is approximately + 1.2V.

The operation of this embodiment will be described.
[Normal operation]
Same as Example 1.

[When a positive DC voltage is supplied, that is, when the voltage at point A is equal to or higher than a first predetermined value]
When a positive DC voltage is supplied from the amplifier circuit to the detection circuit 2, the point A voltage gradually increases, and after a predetermined time determined by the time constant circuit, the point A voltage is equal to or higher than a first predetermined value (approximately + 12V). become. Accordingly, the transistor Q1 is turned on and the transistor Q2 is turned off. As a result, the transistor Q3 is in a state where the base is connected to the ground potential and is turned on. When the transistor Q3 is turned on, the sub power supply circuit 6 is connected to the ground potential via the diodes D4 and D5, and the sub power supply voltage Vs drops to a predetermined voltage (approximately +1.2 V). As a result, although the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the coil 5a, it has not reached the voltage for turning on the relay switch 5b, so the relay switch 5b is turned off. Accordingly, since the main power supply circuit 7 is turned off, the positive DC voltage is prevented from being supplied from the amplifier circuit to the speaker. Here, when the transistor Q3 is turned on, the sub power supply voltage Vs (approximately +1.2 V) is supplied to the base of the transistor Q1 via the diode D3 and the resistor R4, and thus is supplied from the amplifier circuit to the speaker. Regardless of the voltage value, the transistor Q1 is kept on. Therefore, the relay switch 5b can be continuously turned off and the main power supply circuit 7 can be continuously turned off.

[When a negative DC voltage is supplied, that is, when the voltage at point A is equal to or lower than a second predetermined value]
When a negative DC voltage is supplied to the detection circuit 2 from the amplifier circuit, the point A voltage gradually decreases, and after a predetermined time determined by the time constant circuit, the point A voltage is a second predetermined value (approximately -12 V). It becomes the following. Accordingly, the transistor Q2 is turned on and the transistor Q1 is turned off. As a result, the transistor Q3 is in a state where the base is connected to the ground potential and is turned on. When the transistor Q3 is turned on, the sub power supply circuit 6 is connected to the ground potential via the diodes D4 and D5, and the sub power supply voltage Vs drops to a predetermined voltage (approximately +1.2 V). As a result, although the sub power supply voltage Vs from the sub power supply circuit 6 is supplied to the coil 5a, it has not reached the voltage for turning on the relay switch 5b, so the relay switch 5b is turned off. Accordingly, since the main power supply circuit 7 is turned off, a negative DC voltage is prevented from being supplied from the amplifier circuit to the speaker. Here, when the transistor Q3 is turned on, the sub power supply voltage Vs (approximately +1.2 V) is supplied to the base of the transistor Q1 via the diode D3 and the resistor R4, and thus is supplied from the amplifier circuit to the speaker. Regardless of the voltage value, the transistor Q1 is kept on. Therefore, the relay switch 5b can be continuously turned off and the main power supply circuit 7 can be continuously turned off.

  As described above, according to the present embodiment, when a state in which a positive DC voltage or a negative DC voltage is supplied from the amplifier circuit to the speaker is detected by the function of the diode D3, the relay switch 5b is continuously thereafter. Can be turned off, and the main power supply circuit 7 can be turned off continuously.

[Example 3]
FIG. 3 is a circuit diagram illustrating a main part of the amplifying device 21 to which the power supply control device according to the present embodiment is applied. The present embodiment is a combination of the first embodiment and the second embodiment, and the amplifying apparatus 21 includes both the main power supply control circuit 4 and the second main power supply control circuit 8. These operations are as described in the first and second embodiments.

[Example 4]
In the above embodiment, the power supply control device for continuously turning off the main power supply circuit 7 when the amplifier circuit is damaged and a DC voltage is supplied from the amplifier circuit is shown. However, in this example, the main power supply circuit is shown. Is damaged, for example, when a + 15V DC voltage is supplied in a normal state, but when a + 20V DC voltage is supplied, the relay switch 5b is continuously turned off and the main power supply circuit 7 is continuously turned on. Control to off state. FIG. 4 is a schematic circuit diagram showing this example. In this example, as compared with FIG. 1, the transistor Q2 and the diode D2 are omitted, and a resistor R7 is provided instead of the capacitor C1. The operation of this example is substantially the same as the case where a positive DC voltage is supplied from the amplifier circuit to the speaker in FIG.

[Example 5]
In this example, the main power supply circuit is damaged. For example, when a -15V DC voltage is supplied in a normal state, the relay switch 5b is continuously turned off when a -20V DC voltage is supplied. The main power supply circuit 7 is continuously controlled to be turned off. FIG. 5 is a schematic circuit diagram showing this example. In this example, compared with FIG. 1, the transistor Q1 and the diode D1 are omitted, and a resistor R7 is provided instead of the capacitor C1, and the cathode of the diode D3 is connected to the base of the transistor Q2 via the resistor R4. Has been. The operation of this example is substantially the same as the case where a negative DC voltage is supplied from the amplifier circuit to the speaker in FIG. 1, but when the transistor Q3 is turned on, the sub power supply voltage Vs passes through the diode D3 and the resistor R4. And supplied to the base of the transistor Q2. Therefore, the transistor Q2 continuously detects a state in which a negative DC voltage is supplied by the function of the sustain circuit 3.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment.

  The present invention can be suitably employed in amplifiers, AV amplifiers, amplifier built-in speakers, TV receivers, and the like.

DESCRIPTION OF SYMBOLS 1 Amplifying apparatus 2 Detection circuit 3 Maintenance circuit 4 Main power supply control circuit 5 Relay circuit 6 Sub power supply circuit 7 Main power supply circuit 8 Second main power supply control circuit 10 Amplifier circuit 11 Amplifying apparatus 21 Amplifying apparatus

Claims (4)

A first transistor for detecting a state in which a positive DC voltage is supplied;
A second transistor for detecting a state in which a negative DC voltage is supplied;
When the first transistor detects a state in which a positive DC voltage is supplied, or when the second transistor detects a state in which a negative DC voltage is supplied, the sub power supply voltage is set to the main state. When the first transistor does not detect a state in which a positive DC voltage is supplied and the second transistor does not detect a state in which a negative DC voltage is supplied. A third transistor that is turned off and does not supply the sub power supply voltage to the main power supply control circuit and the sustain circuit;
By supplying a sub power supply voltage when the third transistor is in an on state, the main power supply circuit is controlled to be in an off state, and when the third transistor is in an off state, the sub power supply voltage is not supplied. The main power supply control circuit for controlling the main power supply circuit to an on state;
A sustain circuit for continuously detecting a state in which a positive DC voltage is supplied by supplying a sub power supply voltage to the first transistor when the third transistor is in an on state; , Power control device. A first transistor for detecting a state in which a positive DC voltage is supplied;
When the first transistor detects a state in which a positive DC voltage is supplied, the first transistor is turned on, the sub power supply voltage is supplied to the main power supply control circuit and the sustain circuit, and the state in which the positive DC voltage is supplied is A third transistor that is turned off when the first transistor does not detect and does not supply the sub power supply voltage to the main power supply control circuit and the sustain circuit;
By supplying a sub power supply voltage when the third transistor is in an on state, the main power supply circuit is controlled to be in an off state, and when the third transistor is in an off state, the sub power supply voltage is not supplied. The main power supply control circuit for controlling the main power supply circuit to an on state;
A sustain circuit for continuously detecting a state in which a positive DC voltage is supplied by supplying a sub power supply voltage to the first transistor when the third transistor is in an on state; , Power control device.   3. The sustain circuit according to claim 1 or 2, wherein the sustain circuit includes a diode having an anode connected to one of the electrodes of the third transistor and a cathode connected to one of the electrodes of the first transistor. Power control device. A second transistor for detecting a state in which a negative DC voltage is supplied;
When the second transistor detects a state in which a negative DC voltage is supplied, the second transistor is turned on, the sub power supply voltage is supplied to the main power supply control circuit and the sustain circuit, and the state in which the negative DC voltage is supplied is A third transistor which is turned off when the second transistor is not detected and does not supply the sub power supply voltage to the main power supply control circuit and the sustain circuit;
By supplying a sub power supply voltage when the third transistor is in an on state, the main power supply circuit is controlled to be in an off state, and when the third transistor is in an off state, the sub power supply voltage is not supplied. The main power supply control circuit for controlling the main power supply circuit to an on state;
A sustain circuit for continuously detecting a state in which a negative DC voltage is supplied by supplying a sub power supply voltage to the second transistor when the third transistor is in an on state; , Power control device.

Images