KR102051681B1 - Virtual ground circuit - Google Patents

Virtual ground circuit Download PDF

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KR102051681B1
KR102051681B1 KR1020130018333A KR20130018333A KR102051681B1 KR 102051681 B1 KR102051681 B1 KR 102051681B1 KR 1020130018333 A KR1020130018333 A KR 1020130018333A KR 20130018333 A KR20130018333 A KR 20130018333A KR 102051681 B1 KR102051681 B1 KR 102051681B1
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transistor
resistor
virtual ground
amplifier
emitter
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KR1020130018333A
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Korean (ko)
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KR20140110111A (en
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진옥상
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진옥상
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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
    • H03F1/52—Circuit arrangements for protecting such amplifiers
    • 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
    • H03F1/30—Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/34—DC amplifiers in which all stages are DC-coupled
    • H03F3/343—DC amplifiers in which all stages are DC-coupled with semiconductor devices only
    • H03F3/3432—DC amplifiers in which all stages are DC-coupled with semiconductor devices only with bipolar transistors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/007—Protection circuits for transducers

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)

Abstract

Receive the + VI3 voltage and the terminal power supplied to the input power ground (GND-i3) and use the virtual ground circuit 310 to supply the + voltage (+ VO3), -voltage (-VO3) and virtual ground node (GND-o3). In the amplifier 330 operating by using both power sources, when the input power ground (GND-i3) and the virtual ground node (GND-o3) are short-circuited by a user, an overcurrent is generated in the virtual ground circuit 310. And the voltage is output to the output terminal OUT3 of the amplifier 330 so that the output element of the virtual ground circuit 310 is burnt out, the output element of the amplifier 330 is burnt out, or the load connected to the output terminal OUT3 is burnt out. It is a virtual ground circuit that prevents it from happening.

Description

Virtual ground circuit

However, a power circuit and related control unit that receive both powers by inputting power and using a virtual ground circuit to achieve positive power,-voltage, and virtual ground configuration.

Generally, a portable power supply or a stationary amplifier that uses an AC_DC adapter as a power source requires a positive power supply circuit with + power, -power, and GND configuration to drive an OP_AMP or negative feedback amplifier circuit. In order to convert the power into a positive power circuit, a virtual ground node is additionally created using a virtual ground circuit.

Here, the voltage between the + terminal of the AC_DC adapter and the virtual ground node is 1/2 of the output voltage of the AC_DC adapter, and the voltage between the-terminal of the AC_DC adapter and the virtual ground node is 1/2 of the output voltage of the AC_DC adapter. Always maintains the center voltage.

In this case, the voltage of the virtual ground node must be maintained at 1/2 of the voltage input from the AC_DC adapter so that the OP_AMP or the negative feedback amplifier circuit can operate normally.

In general, as shown in FIG. 1, an audio power supply of a PC sound card is connected to an AMP composed of OP_AMP or a negative feedback amplifier while using an independent power supply device. In this case, the negative electrode of the power supply and the audio output terminal of the PC sound card are electrically insulated, so the virtual ground node inside the AMP maintains half the voltage of the power supply, so the OP_AMP or negative feedback amplifier circuit is normal. It works.

If you do not use an independent power supply as shown in Fig. 2 and connect it to the power supply inside the PC where the PC sound card is installed, the terminal of the PC sound card and the internal power supply of the PC are short-circuited. The OP_AMP or Negative Feedback Amplifier does not operate normally because the virtual ground node is shorted with the negative terminal of the power supply, and the virtual ground node cannot maintain half the voltage of the power supply.

That is, in FIG. 3, the + VI3 voltage and the stage power supplied to the input power ground GND-i3 are input and the + voltage (+ VO3), -voltage (-VO3), and virtual ground nodes are input using the virtual ground circuit 310. In the amplifier 330 operating using both power sources configured as (GND-o3), when the input power ground (GND-i3) and the virtual ground node (GND-o3) are shorted by a user's mistake, the virtual ground circuit 310 ), Overcurrent flows and voltage is output to the output terminal OUT3 of the amplifier 330 so that the output element of the virtual ground circuit 310 is burnt out, the output element of the amplifier 330 is burnt out, or connected to the output terminal OUT3. The loaded load may be burned out.

The virtual ground circuit 310 prevents overcurrent from flowing through the virtual ground circuit 310 even when the audio output terminal of the PC sound card is connected to the audio input terminal of the AMP and the power input terminal of the AMP is connected to the power input terminal of the PC. It is to prevent the output device of the burnout, and by blocking the relay (RY311) to prevent the burnout of the output device of the amplifier 330 and to prevent the burnout of the load.

In Figure 4

One end of the positive voltage input terminal (+ VI4), one end of the 41st resistor (R41), one end of the 45th resistor (R45), the collector of the 41st transistor (Q41), and the fourth positive power source (+ VO4);

One end of the input power ground (GND-i4), one end of the 42nd resistor (R42), one end of the 46th resistor (R46), a collector of the 42nd transistor (Q42), and a fourth cathode power source (-VO4);

The other end of the 41st resistor R41, the one end of the 41st constant voltage source CV41, the collector of the 43rd transistor Q43, and the base of the 41st transistor Q41 are connected,

The other end of the 42nd resistor R42, the other end of the 41st constant voltage source CV41, the emitter of the 43rd transistor Q43, and the base of the 42nd transistor Q42,

The base of the 43rd transistor Q43, the other end of the 45th resistor R45 and the other end of the 46th resistor R46 are connected,

Connected to an emitter of the 41st transistor Q41 and one end of the 43rd resistor R43,

Connected to an emitter of the 42nd transistor Q42 and one end of the 44th resistor R44,

A virtual ground circuit 410 connected to the other end of the 43rd resistor R43, the other end of the 44th resistor R44, and the virtual ground node GND_o4;

Is connected to one end of the virtual ground node GND_o4 and the 411 constant voltage source CV411,

The other end of the 411 constant voltage source CV411 and the base of the 412 transistor Q412,

Connected to an emitter of the 412th transistor Q412 and one end of the 411th resistor R411,

A collector of the 412th transistor Q412, one end of the 412th resistor R412, and a base of the 413th transistor Q413,

A collector of the 413 transistor Q413, one end of the 413 resistor R413, a base of the 411 transistor Q411, and one end of the 411 capacitor C411,

Connected to the emitter of the 411 transistor Q411 and one end of the 411 relay RY411 coil,

The other end of the 411 resistor (R411), the other end of the 413 resistor (R413), the collector of the 411 transistor (Q411), and the fourth positive power source (+ VO4),

An amplifier connected to the other end of the 412th resistor R412, the emitter of the 413 transistor Q413, the other end of the 411 capacitor C411, the other end of the 411 relay RY411 coil, and the fourth cathode power source (-VO4). An output control circuit 420;

Connected to an input of a fourth input terminal IN4 and an amplifier AMP4,

Connected to an output of the amplifier AMP4 and one end of the normal open contact of the 411 relay RY411,

An amplifier 430 connected to the other end of the normal-open contact of the 411 relay RY411 and the output terminal OUT4;

Virtual ground circuit consisting of.

In case of using the amplifier (AMP) with the built-in virtual ground circuit, when the audio input terminal and the power input terminal are simultaneously connected to the same PC by a user's mistake, the virtual ground circuit 310, the amplifier 330, and the load (headphone, speaker) ) If the audio input terminal and power input terminal are electrically insulated and replaced with an independent power supply after recognizing the user's faulty connection, the AMP will operate normally and damage the AMP and the load (headphones and speakers). The user can avoid economic or time loss, and the AMP manufacturer can avoid the loss due to after-sales service.

1 illustrates a normal connection method.
2 illustrates an abnormal connection method.
Figure 3: An embodiment of a virtual ground circuit of the prior art.
4 is an embodiment of a virtual ground circuit of the present application.

In Figure 4
By making the resistance values of the 41st resistor R41 and the 42nd resistor R42 the same, the voltage of the virtual ground node GND_o4 becomes 1/2 of the input power supply voltage.
The 43rd transistor Q43, the 45th resistor R45, and the 46th resistor R46 are protection circuits that operate when the virtual ground node GND_o4 and the input power ground GND-i4 are shorted. The virtual ground node GND_o4 and the fourth cathode power source -VO4 are connected to the same node.
The 43rd transistor Q43 controls the voltage across the 41st constant voltage source CV41 which supplies the bias voltage to the output transistors Q41 and Q42. The potential Vb_Q43 of the base of the 43rd transistor Q43 is set by the 45th resistor R45 and the 46th resistor R46 to be lower than the potential of the emitter of the 43rd transistor Q43.
Precisely, the voltage of Vbe_Q23 is lower than the normal bias voltage Vb_Q43 at the base of the 43rd transistor Q43.
Alternatively, when the virtual ground node GND_o4 is described as a reference, the voltage Vbe_Q42 of the 42nd transistor Q42 and the voltages V_R44 of the 44th resistor R44 of the 42nd transistor Q42 are lower than the sum of the potentials of the virtual ground node GND_o4. do.

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That is, the potential Vb_Q43 of the base of the 43rd transistor Q43 is
Vb_Q43 <(V_GND_o4-Vbe_Q42-V_R44) ----- (Equation 41)

The voltage V_CV411 of both ends of the 411 constant voltage source CV411 is greater than the absolute value voltage between the virtual ground node GND_o4 and the fourth positive power source (+ VO4), and the fourth positive power source (+ VO4) and the fourth negative electrode power source ( -VO4) The absolute voltage of both ends is set to be smaller than the voltage obtained by subtracting the voltage Vbe_Q412 between the base and emitter of the 412th transistor Q412.
If you write it down again,
(| + VO4-GND_o4 |) <V_CV411 <(| + VO4 | + | -VO4 |-Vbe_Q412)
----------- (Equation 42)

If the virtual ground node (GND_o4) and the input power ground (GND-i4) is not shorted to explain the normal operating state

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When the potential of the base of the 43rd transistor Q43 satisfies the condition of Equation 41, the collector and the emitter of the 43rd transistor Q43 are turned off to the bases of the output transistors Q41 and Q42. The bias voltage is normally supplied so that the virtual ground node GND_o4 maintains half the voltage of the fourth positive power source (+ VO4) and the negative power source (-VO).

 In this case, the operation of the amplifier output control circuit 420 will be described.

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Since the voltage set in the 411 constant voltage source CV411 by Equation 42 is greater than the voltage between the fourth positive power source (+ VO4) and the virtual ground node GND_o4, the current from the emitter to the base of the 412 transistor Q412 is increased. Since the emitter does not flow, the emitter and the collector of the 412 transistor Q412 are turned off, and the emitter and the collector of the 413 transistor Q413 are also turned off, so that the 411 capacitor C411 and the 413 resistor are turned off. After the delay by the time constant of R413, the 411th relay RY411 operates and the output of the amplifier AMP4 is connected to the output terminal OUT4.

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In this case, the abnormal operation state in which the virtual ground node GND_o4 and the input power ground GND-i4 are shorted will be described.

In Figure 4

When the input power ground (GND-i4) and the virtual ground node (GND_o4) are shorted

The potential of the virtual ground node GND_o4 is lowered equally to the potential of the input power ground GND-i4.

If the operation of the virtual ground circuit in the abnormal operation state,

The base potential of the 43rd transistor Q43 is set under the condition of Equation 41. The virtual ground node GND_o4 is shorted with the input power ground GND-i4 and is also shorted with the fourth cathode power source (-VO4). .
At this time, the emitter potential of the 43rd transistor Q43 is lower than the voltage set by the 45th resistor R45 and the 46th resistor R46, thereby passing through the 45th resistor R45 at the base of the 43rd transistor Q43. As the current flows through the emitter to the base of the 42nd transistor Q42, the collector and the emitter of the 43rd transistor Q43 are turned on, so that the 41st transistor Q41 and the 42nd transistor Q42 are turned on. The bias is set to 0 between the bases, so that no current flows between the emitter and the collector of the 42nd transistor Q42, thereby preventing the overcurrent from flowing. In other words, when the bias voltage becomes zero between the 41 th transistor Q41 and the 42 th transistor Q42 base, both the 41 th transistor Q41 and the 42 th transistor Q42 are turned off and the virtual ground node. (GND_o4) becomes high impedance.

That is, overcurrent does not flow to the output element of the virtual ground circuit 210, thereby protecting the output element.

Referring to the operation of the amplifier output control circuit 420 in an abnormal operation state,

As the potential of the virtual ground node GND_o4 is lowered to the input power ground GND-i4 and the fourth cathode power source (-VO4), the voltage of the 411 constant voltage source CV411 is greater than the voltage represented by Equation 42. The current flows from the emitter of the 412 transistor (Q412) to the 411 constant voltage source (CV411) via the base via the 411 resistor (R411), so that the emitter and collector of the 412 transistor (Q412) are turned on. (ON), the collector and emitter of the 413 transistor (Q413) is also turned on (ON), the voltage of the 411 capacitor (C411) is discharged, the 411 relay (RY411) is stopped and the output of the amplifier (AMP4) Separated from the output terminal OUT4, the output element and the load of the amplifier AMP4 due to overcurrent are protected.

310: virtual ground circuit of an embodiment of the prior art
320: amplifier output control circuit of an embodiment of the prior art
330: Amplifier of one embodiment of the prior art
410: virtual ground circuit of an embodiment of the present technology
420: amplifier output control circuit of an embodiment of the present technology
430: Amplifier of an embodiment of the present technology
GND-o3, GND-o4: Virtual ground node.

Claims (6)

The positive voltage input terminal (+ VI4), one end of the 41st resistor (R41), one end of the 45th resistor (R45), the collector of the 41st transistor (Q41) and the fourth positive power source (+ VO4) are connected,
One end of the input power ground GND-i4, the 42nd resistor R42, the one end of the 46th resistor R46, the collector of the 42nd transistor Q42, and the fourth cathode power source (-VO4) are connected.
The other end of the 41st resistor R41, the one end of the 41st constant voltage source CV41, the collector of the 43rd transistor Q43, and the base of the 41st transistor Q41 are connected,
The other end of the 42nd resistor R42, the other end of the 41st constant voltage source CV41, the emitter of the 43rd transistor Q43 and the base of the 42nd transistor Q42 are connected,
The base of the 43rd transistor Q43, the other end of the 45th resistor R45 and the other end of the 46th resistor R46 are connected,
The emitter of the 41st transistor Q41 and the one end of the 43rd resistor R43 are connected,
The emitter of the 42nd transistor Q42 and one end of the 44th resistor R44 is connected,
A virtual ground circuit 410 to which the other end of the 43rd resistor R43 and the other end of the 44th resistor R44 and the virtual ground node GND_o4 are connected;
One end of the virtual ground node GND_o4 and the 411 constant voltage source CV411 is connected,
The other end of the 411 constant voltage source CV411 and the base of the 412 transistor Q412 are connected,
An emitter of the 412th transistor Q412 and one end of the 411th resistor R411 are connected,
The collector of the 412th transistor Q412, one end of the 412th resistor R412, and the base of the 413th transistor Q413 are connected to each other.
The collector of the 413 transistor Q413, one end of the 413 resistor R413, the base of the 411 transistor Q411, and one end of the 411 capacitor C411 are connected.

An emitter of the 411 transistor Q411 and one end of the 411 relay RY411 coil are connected,
The other end of the 411 resistor (R411), the other end of the 413 resistor (R413), the collector of the 411 transistor (Q411), and the fourth positive power source (+ VO4) are connected.
An amplifier to which the other end of the 412 resistor (R412), the emitter of the 413 transistor (Q413), the other end of the 411 capacitor (C411), the other end of the 411 relay (RY411) coil, and the fourth cathode power source (-VO4) are connected. An output control circuit 420;
The fourth positive power supply (+ V04) and the positive power supply of the amplifier AMP4 are connected,
The fourth negative electrode power source (-V04) and the negative electrode power source of the amplifier AMP4 are connected,
The input of the fourth input terminal IN4 and the amplifier AMP4 is connected,
An output of the amplifier AMP4 and one end of the normal open contact of the 411 relay RY411 are connected,
An amplifier 430 to which the other end of the normal-open contact of the 411 relay RY411 and the output terminal OUT4 are connected;
Virtual ground circuit consisting of.
The positive voltage input terminal (+ VI4), one end of the 41st resistor (R41), the collector of the 41st transistor (Q41) and the fourth positive power source (+ VO4) are connected,
One end of the input power ground GND-i4, the 42nd resistor R42, the collector of the 42nd transistor Q42, and the fourth cathode power source (-VO4) are connected.
The other end of the 41st resistor R41, the one end of the 41st constant voltage source CV41, and the base of the 41st transistor Q41 are connected,
The other end of the 42nd resistor R42 and the other end of the 41st constant voltage source CV41 and the base of the 42nd transistor Q42 are connected.
The emitter of the 41st transistor Q41 and the one end of the 43rd resistor R43 are connected,
The emitter of the 42nd transistor Q42 and one end of the 44th resistor R44 is connected,
A virtual ground circuit 410 to which the other end of the 43rd resistor R43 and the other end of the 44th resistor R44 and the virtual ground node GND_o4 are connected;
One end of the 45th resistor R45 and the fourth positive electrode power source (+ VO4) are connected,
One end of the 46th resistor R46 and the fourth cathode power source (-VO4) are connected,
One end of the 41st constant voltage source CV41 and the collector of the 43rd transistor Q43 are connected,
The other end of the 41st constant voltage source CV41 and the emitter of the 43rd transistor Q43 are connected,
The base of the 43rd transistor (Q43), the other end of the 45th resistor (R45) and the other end of the 46th resistor (R46) is connected.
In claim 2
When the input power ground GND-i4 and the virtual ground node GND_o4 are shorted, the voltage of the 41st constant voltage source CV41 is decreased to turn off the 41th transistor Q41 and the 42nd transistor Q42. Virtual grounding circuit characterized in that to control the virtual ground node (GND_o4) with high impedance.
One end of the virtual ground node GND_o4 and the 411 constant voltage source CV411 is connected,
The other end of the 411 constant voltage source CV411 and the base of the 412 transistor Q412 are connected,
An emitter of the 412th transistor Q412 and one end of the 411th resistor R411 are connected,
The collector of the 412th transistor Q412, one end of the 412th resistor R412, and the base of the 413th transistor Q413 are connected to each other.
The collector of the 413 transistor Q413, one end of the 413 resistor R413, the base of the 411 transistor Q411, and one end of the 411 capacitor C411 are connected.
An emitter of the 411 transistor Q411 and one end of the 411 relay RY411 coil are connected,
The other end of the 411 resistor (R411), the other end of the 413 resistor (R413), the collector of the 411 transistor (Q411), and the fourth positive power source (+ VO4) are connected.
An amplifier to which the other end of the 412 resistor (R412), the emitter of the 413 transistor (Q413), the other end of the 411 capacitor (C411), the other end of the 411 relay (RY411) coil, and the fourth cathode power source (-VO4) are connected. An output control circuit 420;
The fourth positive power supply (+ V04) and the positive power supply of the amplifier AMP4 are connected,
The fourth negative electrode power source (-V04) and the negative electrode power source of the amplifier AMP4 are connected,
The input of the fourth input terminal IN4 and the amplifier AMP4 is connected,
An output of the amplifier AMP4 and one end of the normal open contact of the 411 relay RY411 are connected,
An amplifier 430 to which the other end of the normal open contact of the 411 relay RY411 and the output terminal OUT4 are connected;
Virtual ground circuit consisting of.
In claim 4
And setting the voltage of the 411 constant voltage source (CV411) to a condition (| + VO4-GND_o4 |) <V_CV411 <(| + VO4 | + | -VO4 |-Vbe_Q412).
In claim 3
One end of the virtual ground node GND_o4 and the 411 constant voltage source CV411 is connected,
The other end of the 411 constant voltage source CV411 and the base of the 412 transistor Q412 are connected,
An emitter of the 412th transistor Q412 and one end of the 411th resistor R411 are connected,
The collector of the 412th transistor Q412, one end of the 412th resistor R412, and the base of the 413th transistor Q413 are connected to each other.
The collector of the 413 transistor Q413, one end of the 413 resistor R413, the base of the 411 transistor Q411, and the one end of the 411 capacitor C411 are connected.
An emitter of the 411 transistor Q411 and one end of the 411 relay RY411 coil are connected,
The other end of the 411th resistor R411 and the other end of the 413th resistor R413 and the collector of the 411th transistor Q411 and the fourth positive power source (+ VO4) are connected.
An amplifier to which the other end of the 412 resistor (R412), the emitter of the 413 transistor (Q413), the other end of the 411 capacitor (C411), the other end of the 411 relay (RY411) coil, and the fourth cathode power source (-VO4) are connected. An output control circuit 420;
The fourth positive power supply (+ V04) and the positive power supply of the amplifier AMP4 are connected,
The fourth negative electrode power source (-V04) and the negative electrode power source of the amplifier AMP4 are connected,
The input of the fourth input terminal IN4 and the amplifier AMP4 is connected,
The output of the amplifier AMP4 and one end of the normal open contact of the 411 relay RY411 are connected,
An amplifier 430 to which the other end of the normal-open contact of the 411 relay RY411 and the output terminal OUT4 are connected:
(| + VO4-GND_o4 |) <V_CV411 <(| + VO4 | + | -VO4 |-Vbe_Q412) The normal open contact of the 411 relay (RY411) is turned off by the 411 constant voltage source (CV411) set to be a condition. OFF) to prevent burnout of the load connected to the output of the amplifier (430).
KR1020130018333A 2013-02-20 2013-02-20 Virtual ground circuit KR102051681B1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004071681A (en) 2002-08-02 2004-03-04 Nec Electronics Corp Input protective network
JP2010263116A (en) 2009-05-08 2010-11-18 Mitsubishi Electric Corp Semiconductor device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20120114703A (en) * 2011-04-08 2012-10-17 진옥상 Amplifier that interval regulator is placed

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004071681A (en) 2002-08-02 2004-03-04 Nec Electronics Corp Input protective network
JP2010263116A (en) 2009-05-08 2010-11-18 Mitsubishi Electric Corp Semiconductor device

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