CN111900933A - Automatic power on/off circuit of power amplifier - Google Patents

Automatic power on/off circuit of power amplifier Download PDF

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Publication number
CN111900933A
CN111900933A CN201910370903.1A CN201910370903A CN111900933A CN 111900933 A CN111900933 A CN 111900933A CN 201910370903 A CN201910370903 A CN 201910370903A CN 111900933 A CN111900933 A CN 111900933A
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CN
China
Prior art keywords
triode
resistor
state
power amplifier
circuit
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Pending
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CN201910370903.1A
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Chinese (zh)
Inventor
兰伟华
汤益明
陈远
钟富明
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Xiamen Yaxon Networks Co Ltd
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Xiamen Yaxon Networks Co Ltd
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Priority to CN201910370903.1A priority Critical patent/CN111900933A/en
Publication of CN111900933A publication Critical patent/CN111900933A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/26—Modifications of amplifiers to reduce influence of noise generated by amplifying elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/181—Low frequency amplifiers, e.g. audio preamplifiers
    • H03F3/183—Low frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only
    • H03F3/187—Low frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only in integrated circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
    • H03F3/213—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only in integrated circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/03—Indexing scheme relating to amplifiers the amplifier being designed for audio applications

Abstract

The invention discloses an automatic switch circuit of a power amplifier, which relates to the field of vehicle-mounted power amplifier control.A input end of the automatic switch circuit of the power amplifier is connected with a sound source input of the power amplifier, and an output end of the automatic switch circuit of the power amplifier is connected with a state gating pin of the power amplifier and is used for controlling a difference value between the state gating pin and a power source anode of the power amplifier so as to control the working state of the power amplifier, wherein the states comprise a PLAY state, an ST-BY state and an MUTE state; when an audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the ST-BY state to the MUTE state, and after time T, the power amplifier is switched from the MUTE state to the PLAY state; and when no audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the PLAY state to the ST-BY state. The automatic power on/off circuit of the invention realizes the automatic power on of the power amplifier when sound source is input and the automatic power off when no sound source is input, improves the power on noise and ensures that the power amplifier is in a low power consumption state when the power amplifier is powered off, thereby avoiding unnecessary loss of the power supply on the vehicle.

Description

Automatic power on/off circuit of power amplifier
Technical Field
The invention relates to the field of vehicle-mounted power amplifier control, in particular to an automatic power amplifier on-off circuit.
Background
With the rapid development of the automobile market, the vehicle-mounted multimedia entertainment terminal is widely applied to the passenger car. Meanwhile, in order to meet the requirement that the sound sources of passengers and drivers are separated independently, an independent external power amplifier is often allocated to the drivers independently. And to external power amplifier's control, because long distance transmission problem, can't use CPU's IO mouth to control, generally can increase a mechanical control switch on the panel board, carry out external power amplifier's on-off control, but sometimes because receive the restriction of installation environment in the car, do not reserve sufficient switch mounted position, the mechanical button on passenger train own car has already been many moreover, increases mechanical button again, will bring extra troublesome poeration for the driver. In addition, there is another problem that when an external power amplifier is designed, an AB-type high-power amplifier chip is often used, and some power amplifier ICs have only one state control pin, and the three states of ST-BY, MUTE, and PLAY of the power amplifier are realized BY adjusting the voltage difference between the state control pin and a power supply, where ST-BY is a standby state, the power amplifier is turned off in the state output, and has a small holding current, MUTE is a MUTE state, the power amplifier is turned off in the state output, the noise is minimal, PLAY is a PLAY state, and the power amplifier is turned on in the state output to push a speaker to sound. Fig. 1 shows an amplifying circuit of a TDA7265 dual channel power amplifier, in which a control pin is MUTE/ST-BY (standby), and a voltage difference of the pin MUTE/ST-BY with respect to a power supply + Vs of the power amplifier is adjusted BY combining a switch SW1 and a switch SW2, that is, the power amplifier can be controlled to enter a MUTE state or an ST-BY state BY two switches. When the power amplifier is switched from the ST-BY or MUTE state to the PLAY state, the audio can be output, and the power amplifier can be considered to be started; when the power amplifier is switched into the ST-BY or MUTE state from the PLAY state, no audio is output, and the power amplifier can be considered to be shut down.
Sometimes, for design convenience, a switch is often used for controlling, so that the power amplifier works in an ST-BY state and a PLAY state, or works in an MUTE state and a PLAY state, the former situation is difficult to process power-on 'plop' noise, and the static current of the latter power amplifier in the MUTE state is larger, so that when the power amplifier with only one state control pin is designed, the power amplifier needs to work in the MUTE state at the moment of power-on; when the power amplifier is turned off, the power amplifier is in the ST-BY state, which is the best choice.
Disclosure of Invention
The invention aims to provide an automatic on-off circuit of a power amplifier, which does not carry out automatic on-off control of the power amplifier through external on-off signals such as keys or IO control of a system, improves the starting noise and ensures that the power amplifier is in a low power consumption state when not working, thereby avoiding unnecessary loss of a vehicle-mounted power supply.
In order to achieve the purpose, the invention provides the following technical scheme:
an automatic switch circuit of a power amplifier is provided, wherein the power amplifier is provided with a state gating pin, and the state of the power amplifier is controlled BY adjusting the difference value between the state gating pin and the power supply anode of the power amplifier, wherein the states comprise a PLAY state, an ST-BY state and an MUTE state;
the input end of the automatic switch circuit is electrically connected with an audio input end of the power amplifier, the output end of the automatic switch circuit is electrically connected with a state gating pin of the power amplifier,
when an audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the ST-BY state to the MUTE state, and after time T, the power amplifier is switched from the MUTE state to the PLAY state;
and when no audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the PLAY state to the ST-BY state. Further, in the above-mentioned case,
further, the absolute value of the difference in each state is, from small to large, the ST-BY state, the MUTE state, and the PLAY state.
Further, the automatic on-off circuit comprises an audio amplifying and shaping circuit and a state gating circuit;
the audio amplifying and shaping circuit is used for inputting an audio signal and smoothly outputting a first switch signal, and when the first switch signal is a low-level signal, the audio amplifying and shaping circuit indicates that the audio signal is input, and when the first switch signal is a high-level signal, the audio amplifying and shaping circuit indicates that no audio signal is input;
the state gating circuit includes a first control unit, a second control unit, and a third control unit,
the second control unit receives the first switching signal and outputs a second switching signal in an inverted state;
the third control unit receives the first switching signal and outputs a third switching signal in an inverted phase after time delay;
the first control unit comprises a voltage division network, the voltage division network comprises a pull-up resistor and a grounding resistor which are connected in series, an intermediate node of the voltage division network is connected with a state gating pin, and is connected to the power supply anode of the power amplifier through the pull-up resistor and grounded through the grounding resistor;
when the second switch signal is a low level signal, the intermediate node and the ground are disconnected;
when the second switch signal is a high-level signal, the intermediate node is connected with the ground;
when the third switch signal is changed from a low level signal to a high level signal, the ground resistance is decreased.
Further, the first control unit includes a first triode, a fourth triode, a fifteenth resistor, a sixteenth resistor, a second capacitor, and a second resistor, and the first triode and the fourth triode are NPN triodes;
the pull-up resistor is a second resistor; the grounding resistor comprises a fifteenth resistor and a sixteenth resistor;
the collector of the first triode is connected with the state gating pin, the collector of the first triode is connected with the positive electrode of the power supply of the power amplifier through a second capacitor and a second resistor which are connected in parallel, the emitter of the first triode is grounded through a sixteenth resistor, and the base of the first triode is connected with the output end of the second control unit;
and the collector electrode of the fourth triode is connected to the emitter electrode of the first triode through a fifteenth resistor, the emitter electrode of the fourth triode is grounded, and the base electrode of the fourth triode is connected with the output end of the third control unit.
Further, the second control unit comprises a second triode, a first voltage regulator tube, a fourth resistor, a fifth resistor and a ninth resistor, and the second triode is an NPN triode;
the input end of the second control unit is connected with the base electrode of the second triode;
the output end of the second control unit is connected with the collector electrode of the second triode;
the collector of the second triode is connected with a first node through a fifth resistor and is grounded through a ninth resistor, the first node is grounded through a first voltage-regulator tube and is connected with the positive electrode of a signal power supply through a fourth resistor, and the emitter of the second triode is grounded;
the third control unit comprises a fifth triode, a seventeenth resistor, a twenty-second resistor, a nineteenth resistor and a tenth capacitor, and the fifth triode is an NPN triode;
the input end of the third control unit is connected with the base electrode of the fifth triode;
the output end of the third control unit is connected with the collector of the fifth triode through a nineteenth resistor;
and the collector of the fifth triode is connected with the anode of the signal power supply through a seventeenth resistor, and is grounded through a twenty-second resistor and a tenth capacitor which are connected in parallel, and the emitter of the fifth triode is grounded.
Further, the audio amplifying and shaping circuit comprises an audio amplifying unit, a third triode, a second diode, a seventh resistor, a fourteenth resistor and a seventh capacitor;
the output end of the audio amplifying and shaping circuit is connected with the input end of the audio amplifying unit;
the output end of the audio amplification and shaping circuit is connected with the collector electrode of the third triode;
the audio amplification unit amplifies the audio signal, and inputs the audio signal into a base electrode of a third triode after the audio signal is blocked by a capacitor;
the collector of the third triode is connected with the positive electrode of the signal power supply through a seventh resistor and is grounded through a seventh capacitor and a fourteenth resistor which are connected in parallel;
the cathode of the second diode is connected with the base electrode of the third triode, and the anode of the second diode is grounded.
Further, the audio amplifying unit is a second-order low-pass audio amplifying circuit.
The invention realizes the following technical effects:
the invention realizes the automatic switch control of the power amplifier through the input of the power amplifier sound source, the power amplifier automatically starts when the sound source is input, and automatically shuts down when no sound source is input, simultaneously improves the starting noise, and ensures that the power amplifier is in a low power consumption state when the power amplifier is shut down, thereby avoiding unnecessary loss of the power supply on the vehicle.
Drawings
FIG. 1 is a schematic diagram of power amplifier control;
FIG. 2 is a schematic block diagram of the power amplifier automatic switch control of the present invention;
fig. 3 is a circuit schematic of a preferred embodiment of the present invention.
Detailed Description
To further illustrate the various embodiments, the invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. Those skilled in the art will appreciate still other possible embodiments and advantages of the present invention with reference to these figures. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.
The invention will now be further described with reference to the accompanying drawings and detailed description.
As shown in fig. 2, the present invention discloses an automatic switch circuit of a power amplifier, which includes an audio amplifying and shaping circuit 40 and a state gating control circuit 30, wherein an input terminal of the automatic switch circuit is connected to one of left and right audio channels AUXL/AUXR of the power amplifier 20 (i.e. connected to one of left and right audio channels AUXL/AUXR of a sound source 10), an output terminal of the automatic switch circuit is electrically connected to a state gating pin of the power amplifier 20, and a difference between the state gating pin 201 and an anode of the power amplifier power supply is adjusted to control a state of the power amplifier 20, wherein the state includes a PLAY state, an ST-BY state and a MUTE state.
When an audio signal exists, the automatic switching circuit controls the power amplifier 20 to be switched from the ST-BY state to the MUTE state, and after the time T, the power amplifier is switched from the MUTE state to the PLAY state;
when no audio signal exists, the power amplifier automatic switching circuit controls the power amplifier 20 to be switched from the PLAY state to the ST-BY state.
Fig. 3 shows a preferred embodiment of the automatic switching circuit of the power amplifier according to the present invention, which is specifically described as follows:
the audio amplification and shaping circuit 40 of the automatic switching circuit comprises an audio amplification unit and a shaping unit, wherein the audio amplification unit comprises an operational amplifier U1A, capacitors C4 and C5, resistors R6, R10, R11, R12 and R13, the U1A is the audio operational amplifier, the resistors, the capacitors and the operational amplifier U1A form a second-order low-pass audio power amplification circuit, and the output of the audio amplification unit is defined as a node A; the maximum amplification factor of the audio amplification unit is between 50 and 100 times, the input small audio signal can be amplified into a large audio signal, and when the input audio signal is large, the audio signal is subjected to amplitude limiting output through the audio amplification unit. The audio amplification unit may also employ other audio power amplification circuits with low pass filtering as known in the art to amplify the audio signal and suppress high frequency noise signals.
The shaping unit comprises a diode D2, a triode Q3, resistors R7, R14, a capacitor C6 and a capacitor C7, wherein a triode Q3 is an NPN triode, the collector of the triode Q3 is connected with the output of the shaping part and is defined as a node B, the capacitor C6 is a blocking capacitor and allows an alternating-current audio signal to pass through, a diode D2 provides a negative bias for the base of the triode Q3, when the signal of the node A is a small signal, the base of the triode Q3 cannot generate a positive bias, the triode Q3 is in a closed state, the state of the node B is controlled by the capacitor C7, the resistor R7 and the resistor R14, when the signal of the node A is a large signal, the base of the triode Q3 generates a positive bias, the collector and the emitter of the triode Q3 are conducted, and the voltage of the node B is pulled to be close to 0V; the capacitor C7 is a filter capacitor and is used for smoothing voltage fluctuation of the node B, the resistor R7 and the resistor R14 form a voltage dividing circuit, and when the transistor Q3 is turned off, the voltage of the node B is gradually increased to VCC R14/(R7+ R14).
Whether audio input exists is judged by the switching state of the transistor Q3, and when the transistor Q3 is conducted, the audio input is considered to exist; when transistor Q3 is off, we consider there to be no audio input. The noise introduced by an audio system can be suppressed by adjusting the input threshold of the audio signal, and a good signal-to-noise ratio can be provided when the audio signal is input.
The state gating control circuit 30 of the automatic switching circuit is divided into a first control unit, a second control unit and a third control unit, wherein: the first control unit comprises triodes Q1, Q4, resistors R15, R16, R2 and a capacitor C2, wherein the triodes Q1 and Q4 are NPN triodes.
In the first control unit, the collector of the transistor Q1 and the state gating pin 201 are connected to a node F, the point F is connected to the positive power supply BATT of the power amplifier 20 through a capacitor C2 and a resistor R2, the emitter of the transistor Q1 is grounded through a resistor R16, the collector of the transistor Q4 is connected to a node E through R15 and the emitter of the transistor Q1, the emitter of the transistor Q4 is grounded, and parameters of resistors R2, R15 and R16 are adjusted, so that:
when the triode Q1 is turned off, the voltage VF of the node F is pulled up to BATT through the resistor R2, the voltage of the VF is approximately equal to BATT, and the power amplifier is in an ST-BY state;
when the triode Q1 is conducted and the triode Q4 is closed, the voltage VF of the node F is between BATT-2.5V and BATT-6V, and the power amplifier is in the MUTE state;
when the triode Q1 is conducted and the triode Q4 is conducted, the voltage VF of the node F is smaller than BATT-6V, and the power amplifier is in a PLAY state.
In other embodiments, the first control unit may also adopt other circuits, which may be understood as: the power amplifier comprises a voltage division network, wherein the voltage division network comprises a pull-up resistor and a grounding resistor which are connected in series, an intermediate node of the voltage division network is connected with a state gating pin 201, is connected to a power supply anode BATT of the power amplifier through the pull-up resistor, and is grounded through the grounding resistor; when the transistor Q2 is turned on, the output control signal controls the first control switch to disconnect the intermediate node from ground, so that the intermediate node is pulled high through the pull-up resistor to enter the ST-BY state, and when the transistor Q2 is turned off, the output control signal connects the intermediate node with ground.
The ground resistor is composed of two resistors, which can be set in a series mode or a parallel mode, one of the two resistors is controlled by the second control switch and connected in a parallel or series mode, so that the change of the resistance value of the ground resistor is caused, the voltage change of the state gating pin 201 is caused, and the power amplifier 20 can be controlled to enter the MUTE state or the PLAY state by selecting the resistance values suitable for the pull-up resistor and the ground resistor.
The second control unit is used for controlling the conduction of a transistor Q1, and the third unit is used for controlling the conduction of a transistor Q4. When the second control unit and the third control unit adopt the same control input, the delay circuit is arranged on the third power supply, so that the triode Q4 is conducted later than the triode Q1, the power amplifier is switched from the ST-BY state to the MUTE state and then enters the PLAY state when the power amplifier is started, and the problem of starting noise is solved. When the power amplifier is shut down, the triode Q1 is closed, and the power amplifier enters a low-power-consumption ST-BY state from a PLAY state.
Specifically, in this embodiment, the second control unit includes: the triode Q2, the resistor R4, the resistor R5, the resistor R9 and the voltage regulator tube D1; the triode Q2 is an NPN triode, the stabilized voltage of the voltage regulator tube D1 is VZ, and the voltage regulator tube D1 and the resistor R4 are connected in series with the anode VCC of the signal power supply and the ground GND to form a voltage stabilizing circuit and provide stable voltage. The base electrode of the triode Q2 is connected with the node B through a resistor R8, the collector electrode of the triode Q2 is defined as a node C, the node C is connected with the middle node of a voltage stabilizing tube D1 and a resistor R4 through a resistor R5, the node C is grounded through a resistor R9 and is connected with the base electrode of the triode Q1, the conduction and the closing of the triode Q1 are controlled, and the emitter electrode of the triode Q2 is grounded. When the triode Q2 is conducted, the voltage VC of the node C is close to 0V, and the triode Q1 is closed; when the transistor Q2 is turned off, the voltage VC at the node C is VZ R9/(R5+ R9), and the resistor R5 and the resistor R9 are adjusted so that the transistor Q1 is turned on at this voltage.
The third unit comprises a triode Q5, resistors R21, R17, R22, R19 and a capacitor C10, wherein the triode Q5 is an NPN triode, the base electrode of the triode Q5 is connected with a node B through the resistor R21, the collector electrode of the triode Q5 is connected with the positive electrode VCC of the signal power supply through the resistor R17, the collector electrode is grounded through the resistor R17 and the capacitor C10 which are connected in parallel, the base electrode of the triode Q4 is connected through the resistor R19, and the emitter electrode of the triode Q5 is grounded. When the triode Q5 is turned on, the voltage VD of the node D is close to 0V, the triode Q4 is turned off, and when the Q5 is turned off, the node D is boosted to VCC R22/(R17+ R22) from 0V after the time T under the action of the delay circuit formed by the resistor R17 and the capacitor C10, and the triode Q4 is turned on.
Under the common control of the second control unit and the third unit, the transistor Q1 is turned on before the transistor Q4.
In practical applications, the second control unit and the third control unit may also adopt other control circuits, as long as the triode transistor Q1 of the first control unit is controlled to be turned on before the triode transistor Q4, so that the power amplifier is turned from the ST-BY state to the MUTE state and then from the MUTE state to the PLAY state when the power amplifier is turned on. Through the circuit, the automatic on-off control of the power amplifier is realized, and the on-off noise is reduced; when the power amplifier is shut down, the power amplifier enters an ST-BY mode with low power consumption, so that unnecessary power consumption on a vehicle is avoided.
While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. The utility model provides an automatic on-off circuit of power amplifier which characterized in that: the power amplifier is provided with a state gating pin, and the state of the power amplifier is controlled BY adjusting the difference value between the state gating pin and the power supply anode of the power amplifier, wherein the state comprises a PLAY state, an ST-BY state and an MUTE state;
the input end of the automatic switch circuit is electrically connected with an audio input end of the power amplifier, the output end of the automatic switch circuit is electrically connected with a state gating pin of the power amplifier,
when an audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the ST-BY state to the MUTE state, and after time T, the power amplifier is switched from the MUTE state to the PLAY state;
and when no audio signal exists, the automatic switching circuit controls the power amplifier to be switched from the PLAY state to the ST-BY state.
2. The auto-on/off circuit of claim 1, wherein: the absolute value of the difference in each state is the ST-BY state, the MUTE state and the PLAY state from small to large.
3. The auto-on/off circuit of claim 2, wherein: the device comprises an audio amplification and shaping circuit and a state gating circuit;
the audio amplifying and shaping circuit is used for inputting an audio signal and smoothly outputting a first switch signal, and when the first switch signal is a low-level signal, the audio amplifying and shaping circuit indicates that the audio signal is input, and when the first switch signal is a high-level signal, the audio amplifying and shaping circuit indicates that no audio signal is input;
the state gating circuit comprises a first control unit, a second control unit and a third control unit;
the second control unit receives the first switching signal and outputs a second switching signal in an inverted state;
the third control unit receives the first switching signal and outputs a third switching signal in an inverted phase after time delay;
the first control unit comprises a voltage division network, the voltage division network comprises a pull-up resistor and a grounding resistor which are connected in series, an intermediate node of the voltage division network is connected with a state gating pin, and is connected to the power supply anode of the power amplifier through the pull-up resistor and grounded through the grounding resistor;
when the second switch signal is a low level signal, the intermediate node and the ground are disconnected;
when the second switch signal is a high-level signal, the intermediate node is connected with the ground;
when the third switch signal is changed from a low level signal to a high level signal, the ground resistance is decreased.
4. The auto-on/off circuit of claim 3, wherein:
the first control unit comprises a first triode, a fourth triode, a fifteenth resistor, a sixteenth resistor, a second capacitor and a second resistor, and the first triode and the fourth triode are NPN triodes;
the pull-up resistor is a second resistor; the grounding resistor comprises a fifteenth resistor and a sixteenth resistor;
the collector of the first triode is connected with the state gating pin, the collector of the first triode is connected with the positive electrode of the power supply of the power amplifier through a second capacitor and a second resistor which are connected in parallel, the emitter of the first triode is grounded through a sixteenth resistor, and the base of the first triode is connected with the output end of the second control unit;
and the collector electrode of the fourth triode is connected to the emitter electrode of the first triode through a fifteenth resistor, the emitter electrode of the fourth triode is grounded, and the base electrode of the fourth triode is connected with the output end of the third control unit.
5. The auto-on/off circuit of claim 3, wherein:
the second control unit comprises a second triode, a first voltage regulator tube, a fourth resistor, a fifth resistor and a ninth resistor, and the second triode is an NPN triode;
the input end of the second control unit is connected with the base electrode of the second triode;
the output end of the second control unit is connected with the collector electrode of the second triode;
the collector of the second triode is connected with a first node through a fifth resistor and is grounded through a ninth resistor, the first node is grounded through a first voltage-regulator tube and is connected with the positive electrode of a signal power supply through a fourth resistor, and the emitter of the second triode is grounded;
the third control unit comprises a fifth triode, a seventeenth resistor, a twenty-second resistor, a nineteenth resistor and a tenth capacitor, and the fifth triode is an NPN triode;
the input end of the third control unit is connected with the base electrode of the fifth triode;
the output end of the third control unit is connected with the collector of the fifth triode through a nineteenth resistor;
and the collector of the fifth triode is connected with the anode of the signal power supply through a seventeenth resistor, and is grounded through a twenty-second resistor and a tenth capacitor which are connected in parallel, and the emitter of the fifth triode is grounded.
6. The auto-on/off circuit of claim 1, wherein: the audio amplifying and shaping circuit comprises an audio amplifying circuit, a third triode, a second diode, a seventh resistor, a fourteenth resistor and a seventh capacitor;
the output end of the audio amplifying and shaping circuit is connected with the input end of the audio amplifying circuit;
the output end of the audio amplification and shaping circuit is connected with the collector electrode of the third triode;
the audio amplifying circuit amplifies the audio signal, and inputs the audio signal into the base electrode of the third triode after the audio signal is blocked by the capacitor;
the collector of the third triode is connected with the positive electrode of the signal power supply through a seventh resistor and is grounded through a seventh capacitor and a fourteenth resistor which are connected in parallel;
the cathode of the second diode is connected with the base electrode of the third triode, and the anode of the second diode is grounded.
7. The auto-on/off circuit of claim 6, wherein: the audio amplification unit is a second-order low-pass audio amplification circuit.
CN201910370903.1A 2019-05-06 2019-05-06 Automatic power on/off circuit of power amplifier Pending CN111900933A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201910370903.1A CN111900933A (en) 2019-05-06 2019-05-06 Automatic power on/off circuit of power amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201910370903.1A CN111900933A (en) 2019-05-06 2019-05-06 Automatic power on/off circuit of power amplifier

Publications (1)

Publication Number Publication Date
CN111900933A true CN111900933A (en) 2020-11-06

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Application Number Title Priority Date Filing Date
CN201910370903.1A Pending CN111900933A (en) 2019-05-06 2019-05-06 Automatic power on/off circuit of power amplifier

Country Status (1)

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CN (1) CN111900933A (en)

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