CN1619946A - Noise limiting circuit during power source switching - Google Patents
Noise limiting circuit during power source switching Download PDFInfo
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- CN1619946A CN1619946A CN 200310118065 CN200310118065A CN1619946A CN 1619946 A CN1619946 A CN 1619946A CN 200310118065 CN200310118065 CN 200310118065 CN 200310118065 A CN200310118065 A CN 200310118065A CN 1619946 A CN1619946 A CN 1619946A
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Abstract
A silencing circuit for switching power source wherein the power action circuit conducts bypass transistor in power switching moment to transmit sound signal through bypass way to grounding end, the special voltage provide circuit forbids power switching to amplifying circuit by a input/output control end before power switching on to reduce the amplifying circuit generating noise. In power switching off moment, the power on/off control circuit conducts bypass transistor to transmit sound signal through bypass way to grounding end by charge voltage of a capacitor.
Description
Technical field
The present invention is relevant for the control circuit of voice signal, and the mute circuit of voice signal when particularly switching relevant for power supply.
Prior art
Please refer to Fig. 1, it is depicted as the schematic diagram of audio signal processing circuit in the known player.In general, all there is the processing core of a microcontroller (Microprocessor) 12 as player 10 player 10 inside, it can receive the audio-visual data (Audio Video Data) 20 of all size, and the voice data in the audio-visual data (Audio Data) 22 is delivered to Audio Processing chip 14 handle voice data, and view data (Video Data) is delivered to the picture processing chip (not shown) and come image data processing.
And Audio Processing chip 14 can be L channel (Left Channel, L '), R channel (Right Channel, R ') or the voice signal of multichannel more with voice data translation.These voice signals then can export amplifying circuit 16 to again, carry out the operation that voice signal amplifies.Therefore, receive and be sent to the loudspeaker (not shown) by the post-amplifier (not shown) behind the voice signal that amplifying circuit 16 is used to amplify L channel (L) and amplify R channel (R).
In general, player that sells on the market and home audio have a problem that can't solve fully for a long time at the output of voice signal always, and that is exactly when power supply switches, and loudspeaker can produce the noise of moment.In other words, when the moment of power connection, because power supply provides no show stable state still, the circuit of player inside can produce noise inevitably and be attached on the voice signal, can produce discordant noise when these voice signals with noise are amplified to output to loudspeaker.In like manner, on the voice signal of circuit after also can producing noise and being added in amplification of the moment of power remove player inside and make loudspeaker produce noise.
In order to address the above problem, can see the noise suppression chip in the time of can constraining the power supply switching on the market, yet, use these chips not only can significantly improve the cost of player.In fact, these chips can not be eliminated the voice signal output that contains noise fully when power supply switches, and it only can reduce the volume of noise.So, can not solve the problem that the noise of player when power supply switches produces fully.
Summary of the invention
Order of the present invention provides the mute circuit that a kind of power supply switches, in the moment that the player power supply switches, the voice signal on the audio signal output terminal can bypass to earth terminal, prevent that voice signal is passed to post-amplifier.
The mute circuit that the present invention proposes a kind of power supply when switching is used in the amplifying circuit with audio signal output terminal, and it is summarized as follows: each bypass elements has a control end, but when control end is connected the signal on the bypass audio signal output terminal; Energy supply startup control circuit is to rise within the scheduled time in power connection moment, connects the control end of bypass elements; It is control according to the I/O port control end that specific voltage provides circuit, forbids the amplifying circuit operation in the moment of power connection; And the power remove control circuit is the moment at power remove, utilizes charging voltage on the capacitor to connect the control end of bypass elements.
Moreover the mute circuit that the present invention proposes a kind of power supply when switching is used in the amplifying circuit with audio signal output terminal, and it is summarized as follows: each bypass elements has a control end, but when control end is connected the signal on the bypass audio signal output terminal; Energy supply startup control circuit is to rise within the scheduled time in power connection moment, connects the control end of bypass elements; And the power remove control circuit is the moment at power remove, utilizes charging voltage on the capacitor to connect the control end of bypass elements.
Moreover the mute circuit that the present invention proposes a kind of power supply when switching is used in the amplifying circuit with audio signal output terminal, and it is summarized as follows: each bypass elements has a control end, but when control end is connected the signal on the bypass audio signal output terminal; And energy supply startup control circuit is to rise within the scheduled time in power connection moment, connects the control end of bypass elements.
Moreover the mute circuit that the present invention proposes a kind of power supply when switching is used in the amplifying circuit with audio signal output terminal, and it is summarized as follows: each bypass elements has a control end, but when control end is connected the signal on the bypass audio signal output terminal; And the power remove control circuit is the moment at power remove, utilizes charging voltage on the capacitor to connect the control end of bypass elements.
In order further to understand feature of the present invention and technology contents, see also following about detailed description of the present invention and accompanying drawing, yet appended graphic only provide with reference to and the explanation usefulness, be not to be used for the present invention is limited.
Description of drawings
Its illustrate of Fig. 1 is the schematic diagram of audio signal processing circuit in the known player;
Its mute circuit figure when switching of Fig. 2 for power supply of the present invention;
It is the voltage stabilizing circuit figure in the present invention's invention Fig. 3; And
It is charge-discharge circuit figure of the present invention for Fig. 4.
The drawing reference numeral explanation
10,30 players
12,32 microcontrollers
14,34 Audio Processing chips
16,36 amplifying circuits
20 audio-visual datas
22 voice signals
50 power turn-on control circuits
60 specific voltages provide circuit
64 voltage stabilizing circuits
80 power remove control circuits
83 charge-discharge circuits
Embodiment
Please refer to Fig. 2, the mute circuit figure when it switches for power supply of the present invention.At first introduce its annexation, all there is the processing core of a microcontroller 32 as player 30 player 30 inside, it can receive the audio-visual data (Audio Video Data) 20 of all size, and the voice data in the audio-visual data (Audio Data) 22 is delivered to Audio Processing chip 34 handle voice data, and view data (VideoData) is delivered to the picture processing chip (not shown) and come image data processing.
And Audio Processing chip 34 can be L channel (Left Channel, L '), R channel (Right Channel, R ') or the voice signal of multichannel more with voice data translation.These voice signals then can export amplifying circuit 36 to again, carry out the operation that voice signal amplifies.Therefore, amplifying circuit 36 is to receive and be sent to the loudspeaker (not shown) by the post-amplifier (not shown) behind the voice signal that is used to amplify L channel (L) and amplify R channel (R).
The present invention is that all audio signal output terminals (L, R) at amplifying circuit 36 are gone up adding one bypass transistor (Bypass BJT) B1, B2.According to present embodiment, pass-transistor B1, B2 are NPN bipolar junction transistor (Bipolar Junction Transistor), wherein, collector terminal (Collector) is connected to audio signal output terminal (L, R), emitter terminal (Emitter) is connected to earth terminal, and base terminal (Base) is the conducting (On) and shutoff (Off) in order to control pass-transistor B1, B2 then.
Also comprise an energy supply startup control circuit 50 among the present invention, the conducting of control pass-transistor B1, B2 and shutoff opportunity when being used for power connection.In power connection control circuit 50, also comprise replacement (Reset) circuit 52 and one first a switching transistor T1.Wherein, the variation of reset circuit 52 supply voltage 5V supply voltage during of being connected to 5V in order to the monitoring power connection.According to embodiments of the invention, reset circuit 52 is before the 5V supply voltage rises to 4.38V, and reset circuit 52 outputs are exported a low level signal, the exportable high level signal of its output after the rising of 5V supply voltage reaches 4.38V.And the first switching transistor T1 is a PNP bipolar transistor, emitter terminal is connected to the 5V supply voltage, be connected one first resistance R 1 between base terminal and reset circuit 52 outputs, collector terminal is connected to the positive terminal of first Schottky diode (Schottky Diode) D1, is connected one second resistance R 2 between the control end of the negative pole end of the first Schottky diode D1 and pass-transistor B1, B2.
The present invention comprises that also a specific voltage provides circuit 60, is used to provide the power supply of amplifying circuit 36.According to embodiments of the invention, it is to receive a 12V supply voltage to be connected to a voltage stabilizing circuit 64 through a second switch transistor T 2 that specific voltage provides circuit 60, and voltage stabilizing circuit 64 can receive output one 10V voltage behind the 12V supply voltage and as the power supply of amplifying circuit 36.In an embodiment of the present invention, second switch transistor T 2 is a P-channel metal-oxide-semiconductor transistor (P Channel MOSTransistor), wherein, source terminal (Source) is connected to the 12V supply voltage, be connected one the 3rd resistance R 3 between source terminal and the gate terminal (Gate), drain electrode end (Drain) is connected to voltage stabilizing circuit 64.
And the conducting of second switch transistor T 2 and shutoff are to bring in control by I/O port control.The I/O port control end is any one I/O port with normal low level (Normal Lo) on the microcontroller 32.The I/O port control end is connected to a pull-down transistor (Pull DownTransistor) M1 grid.According to present embodiment, pull-down transistor M1 is a N channel metal oxide semiconductor transistor (N Channe1 MOS Transistor), and drain electrode end is connected to the grid of second switch transistor T 2, and source terminal is connected to earth terminal.
The present invention also comprises a power remove control circuit 80.Wherein, the 4th resistance R 4 is connected between pull-down transistor M1 drain electrode end and one the 3rd switching transistor T3 base terminal.According to present embodiment, the 3rd switching transistor T3 is a PNP bipolar junction transistor, and its emitter terminal is connected to the 12V supply voltage, and drain electrode end is connected to a charge-discharge circuit 83.Charge-discharge circuit 83 is when the 3rd switching circuit T3 conducting (On), and output can provide a high voltage, and when the 3rd switching circuit T3 turn-offed (Off), output can provide a low-voltage.Moreover one second Schottky diode D2 positive terminal is connected to the 12V supply voltage, is connected one first capacitor C1 between negative pole end and the earth terminal.And the 4th switching transistor T4 gate terminal is connected to the output of charge-discharge circuit 83.According to present embodiment, the 4th switching transistor T4 is a P-channel metal-oxide-semiconductor transistor, and its source terminal is connected to the negative pole end of the first Schottky diode D1, is connected one the 5th resistance R 5 between its drain electrode end and pass-transistor B1, the B2 control end.
Please refer to Fig. 3, it is the voltage stabilizing circuit figure in the present invention's invention.Include an inductor L in the voltage stabilizing circuit 64, the one end is connected to the drain electrode end of second switch transistor T 2.And between second, third capacitor C2 in parallel, the other end and earth terminal that C3 is connected in inductor L.The the 6th, the 7th, the 8th resistance R 6 of serial connection, C3 two ends that R7, R8 are connected in the 3rd capacitor.The positive terminal of shunt voltage adjuster (Shunt Regulator) SR is connected to earth terminal, and negative pole end is connected to the node between the 6th resistance and the 7th resistance, and reference edge is connected to the node between the 7th resistance and the 8th resistance.Therefore, when 2 conductings of second switch transistor T,, make that the node between the 6th resistance and the 7th resistance can provide a stable 10V voltage via the dividing potential drop of the 6th, the 7th, the 8th resistance and the operation of shunt voltage adjuster SR.
Please refer to Fig. 4, it is charge-discharge circuit figure of the present invention.The 9th resistance R 9 one ends are connected in the 3rd switching transistor T3 collector terminal, and the other end of the 9th resistance R 9 is connected to earth terminal.The tenth resistance R 10 be parallel to the 9th resistance R 9 two ends after the 4th capacitor C4 is connected in series.And the negative pole end of the 3rd Schottky diode D3 is connected to the node between the 9th resistance R 9 and the tenth resistance R 10, and the positive terminal of the 3rd Schottky diode D3 is connected to the node between the tenth resistance R 10 and the 4th capacitor C4.And the node that the tenth resistance R 10 is connected with the 4th capacitor C4 is the output of charge-discharge circuit 83.When the 3rd switching transistor T3 conducting, the 10th resistance R 10 and the 4th capacitor C4 form a RC charging circuit, and therefore, the 4th capacitor C4 can obtain the 12V supply voltage when stable state.Therefore, the output output HIGH voltage of charge-discharge circuit 83.Moreover when the 3rd switching transistor T3 turn-offed, the electric charge on the 4th capacitor C4 was via the 3rd Schottky diode D3 and 9 repid discharges of the 9th resistance R.Therefore, the output output LOW voltage of charge-discharge circuit 83.
Operation when next introducing power supply of the present invention and switching:
(1) when the moment of power connection, because the I/O port control end is normal low level, therefore, pull-down transistor M1 turn-offs (Off).Moreover, because pull-down transistor M1 turn-offs, make second switch transistor T 2 gate terminal be connected to the 12V supply voltage.Therefore, second switch transistor T 2 also turn-offs (Off), that is the 12V supply voltage can't provide to voltage stabilizing circuit 64, makes amplifying circuit 36 not have power supply to provide, so, can reduce the chance that produces noise on the amplifying circuit 36.Therefore, do not have noise output on the audio signal output terminal of amplifying circuit 36.
Moreover, for still can output noise on the audio signal output terminal that prevents amplifying circuit 36, energy supply startup control circuit 50 in moment of power connection because 5V supply voltage no show stable state still, therefore, be changed in the time of 4.38V by 0V at the 5V supply voltage, reset circuit 52 output low level signal to the first switching transistor T1 make the switching transistor T1 conducting (On) of winning, that is, pass-transistor B1, the control end of B2 can receive the 5V supply voltage that is rising, therefore, pass-transistor B1, B2 conducting (On) so, can connect all signals on amplifying circuit 36 audio signal output terminals and conduct to earth terminal.So, in the moment of power turn-on, conduct to earth terminal via amplifying circuit 36 power supplys not being provided and signals all on the audio signal output terminal being connect, can prevent fully that any signal on the audio signal output terminal is passed to the post-amplifier (not shown).
When the 5V supply voltage rises above after the 4.38V, reset circuit 52 output high level signal to the first switching transistor T1 make the switching transistor T1 that wins turn-off (Off), make the control end of pass-transistor B1, B2 turn-off (Off), at this moment, all signals can be passed to the post-amplifier (not shown) on the audio signal output terminal.
(2) when player 30 operation, the I/O port control end must be exported high level, makes pull-down transistor M1 conducting (On).Moreover, because pull-down transistor M1 conducting makes second switch transistor T 2 gate terminal be connected to earth terminal.Therefore, also conducting of second switch transistor T 1 (On), that is the 12V supply voltage can provide to voltage stabilizing circuit 64, and making amplifying circuit 36 obtain power supply provides, and therefore, amplifying circuit 36 gets final product operate as normal.
Moreover, because pull-down transistor M1 conducting, but the 3rd also conducting of switching transistor T3, make charge-discharge circuit 83 output high level turn-off (Off) the 4th switching transistor T4, so when the player normal running, pass-transistor B1, B2 are at off state.Moreover the charge path that the second Schottky diode D2 is provided can charge to the 12V supply voltage with the first capacitor C1.
(3) when the moment of power remove, the 3rd switching circuit T3 turn-offs (Off), and therefore, charge-discharge circuit 82 output LOW voltages make the 4th switching transistor T4 conducting (On).At this moment, but charging voltage conducting pass-transistor B1, B2 on the first capacitor C1.Therefore, before the electric charge on the first capacitor C1 disappeared, pass-transistor continued to maintain the state of conducting, and at this moment, signals all on the audio signal output terminal are all conducted to earth terminal.Therefore, in the moment of power remove, can prevent fully that any signal on the audio signal output terminal is passed to the post-amplifier (not shown).
In the present invention, energy supply startup control circuit 50 is at the moment of power turn-on conducting pass-transistor B1, B2, makes voice signal be passed to earth terminal by bypass path.Therefore in the moment of power turn-on, prevent that amplifying circuit 36 from producing and have the noise sound signal and be passed to post-amplifier.
Moreover it is before power turn-on and player 30 operate as normal that specific voltage provides circuit 60, utilizes I/O port control to bring in and forbids providing power supply to amplifying circuit 36, reduces the chance that amplifying circuit 36 produces the voice signal with noise.
Moreover, power remove control circuit 80 is the moments at power remove, because the 4th switching transistor T4 conducting, charging voltage on the first capacitor C1 can be so that pass-transistor B1, B2 conducting, make in the moment of power remove, prevent that amplifying circuit 36 from producing and have the noise sound signal and be passed to post-amplifier.
Therefore, advantage of the present invention is the mute circuit when proposing a kind of power supply and switching, in the moment that the player power supply switches, the voice signal on the audio signal output terminal can bypass to earth terminal, prevent that voice signal is passed to post-amplifier.
In sum, though the present invention with preferred embodiment openly as above, right its is not in order to limit the present invention, any those skilled in the art, under the situation that does not break away from the spirit and scope of the present invention, can carry out various changes and modification, therefore scope of the present invention is as the criterion with the claim restricted portion that is proposed.
Claims (20)
1. the mute circuit a when power supply switches is used in the amplifying circuit with at least one audio signal output terminal, comprising:
At least one bypass elements, each this bypass elements has a control end, when this control end is connected, but the signal on this at least one audio signal output terminal of bypass;
One energy supply startup control circuit, this energy supply startup control circuit are to rise within the scheduled time in power connection moment, connect this control end of this at least one bypass elements;
One specific voltage provides circuit, and it is control according to an I/O port control end that this specific voltage provides circuit, forbids this amplifying circuit operation in the moment of this power connection; And
One power remove control circuit, this power remove control circuit is the moment at this power remove, utilizes charging voltage on the capacitor to connect this control end of this at least one bypass elements.
2. the mute circuit when power supply as claimed in claim 1 switches, wherein each this bypass elements all has a bipolar junction transistor.
3. the mute circuit when power supply as claimed in claim 2 switches, wherein this bipolar junction transistor is a NPN bipolar junction transistor, wherein a collector terminal is connected to this at least one audio signal output terminal, and an emitter terminal is connected to an earth terminal, and a base terminal is this control end.
4. the mute circuit when power supply as claimed in claim 1 switches, wherein this energy supply startup control circuit comprises:
One reset circuit, this reset circuit can play output one signal specific in this scheduled time in this power connection moment; And
One switch element, this switch element can be connected this control end of this at least one bypass elements according to this signal specific.
5. the mute circuit when power supply as claimed in claim 1 switches, wherein this specific voltage provides circuit to comprise:
One switch element, this switch element are that the signal according to this I/O port control end optionally provides a supply voltage; And
One voltage stabilizing circuit, this voltage stabilizing circuit can receive this supply voltage and be converted into a specific voltage and provide to this amplifying circuit.
6. the mute circuit when power supply as claimed in claim 5 switches, wherein this I/O port control end signal specific of having normality in the moment of this power connection makes this switching circuit forbid providing this supply voltage to this voltage stabilizing circuit.
7. the mute circuit when power supply as claimed in claim 1 switches, wherein this power remove control circuit comprises:
One first switch element optionally provides a supply voltage according to the signal of this I/O port control end;
One control circuit when this control circuit does not receive this supply voltage that this first switch element exports, provides a connection signal;
One Schottky diode, a positive terminal of this Schottky diode is connected to this supply voltage;
This capacitor, this capacitor are connected between the negative pole end and this earth terminal of this Schottky diode;
One second switch element when this second switch element receives this connection signal, is connected the charging voltage on this capacitor this control end of this at least one bypass elements.
8. the mute circuit a when power supply switches is used in the amplifying circuit with at least one audio signal output terminal, comprising:
At least one bypass elements, each this bypass elements has a control end, when this control end is connected, but the signal on this at least one audio signal output terminal of bypass;
One energy supply startup control circuit, this energy supply startup control circuit are to rise within the scheduled time in power connection moment, connect this control end of this at least one bypass elements; And
One power remove control circuit, this power remove control circuit is the moment at this power remove, utilizes charging voltage on the capacitor to connect this control end of this at least one bypass elements.
9. the mute circuit when power supply as claimed in claim 8 switches, wherein each this bypass elements is all a bipolar junction transistor.
10. the mute circuit when power supply as claimed in claim 9 switches, wherein this bipolar junction transistor is a NPN bipolar junction transistor, wherein a collector terminal is connected to this at least one audio signal output terminal, and an emitter terminal is connected to an earth terminal, and a base terminal is this control end.
The mute circuit when 11. power supply as claimed in claim 8 switches, wherein this energy supply startup control circuit comprises:
One reset circuit, this reset circuit can play output one signal specific in this scheduled time in this power connection moment; And
One switch element, this switch element can be connected this control end of this at least one bypass elements according to this signal specific.
The mute circuit when 12. power supply as claimed in claim 8 switches, wherein this power remove control circuit comprises:
One first switch element optionally provides a supply voltage according to the signal of this I/O port control end;
One control circuit when this control circuit does not receive this supply voltage that this first switch element exports, provides a connection signal;
One Schottky diode, a positive terminal of this Schottky diode is connected to this supply voltage;
This capacitor, this capacitor are connected between the negative pole end and this earth terminal of this Schottky diode;
One second switch element when this second switch element receives this connection signal, is connected the charging voltage on this capacitor this control end of this at least one bypass elements.
13. the mute circuit a when power supply switches is used in the amplifying circuit with at least one audio signal output terminal, comprising:
At least one bypass elements, each this bypass elements has a control end, the signal when this control end is connected on this at least one audio signal output terminal of bypass; And
One energy supply startup control circuit, this energy supply startup control circuit are to rise within the scheduled time in power connection moment, connect this control end of this at least one bypass elements.
The mute circuit when 14. power supply as claimed in claim 13 switches, wherein each this bypass elements is all a bipolar junction transistor.
The mute circuit when 15. power supply as claimed in claim 14 switches, wherein this bipolar junction transistor is a NPN bipolar junction transistor, wherein a collector terminal is connected to this at least one audio signal output terminal, and an emitter terminal is connected to an earth terminal, and a base terminal is this control end.
The mute circuit when 16. power supply as claimed in claim 13 switches, this energy supply startup control circuit comprises:
One reset circuit, this reset circuit can play output one signal specific in this scheduled time in this power connection moment; And
One switch element, this switch element can be connected this control end of this at least one bypass elements according to this signal specific.
17. the mute circuit a when power supply switches is used in the amplifying circuit with at least one audio signal output terminal, comprising:
At least one bypass elements, each this bypass elements has a control end, the signal when this control end is connected on this at least one audio signal output terminal of bypass; And
One power remove control circuit, this power remove control circuit are in a mains switch disconnected moment, utilize charging voltage on the capacitor to connect this control end of this at least one bypass elements.
The mute circuit when 18. power supply as claimed in claim 17 switches, wherein each this bypass elements is all a bipolar junction transistor.
The mute circuit when 19. power supply as claimed in claim 18 switches, wherein this bipolar junction transistor is a NPN bipolar junction transistor, wherein a collector terminal is connected to this at least one audio signal output terminal, and an emitter terminal is connected to an earth terminal, and a base terminal is this control end.
The mute circuit when 20. power supply as claimed in claim 17 switches, wherein this power remove control circuit comprises:
One first switch element optionally provides a supply voltage according to the signal of this I/O port control end;
One control circuit when this control circuit does not receive this supply voltage that this first switch element exports, provides a connection signal;
One Schottky diode, a positive terminal of this Schottky diode is connected to this supply voltage;
This capacitor, this capacitor are connected between the negative pole end and this earth terminal of this Schottky diode;
One second switch element when this second switch element receives this connection signal, is connected the charging voltage on this capacitor this control end of this at least one bypass elements.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101180658A CN100508368C (en) | 2003-11-20 | 2003-11-20 | Noise limiting circuit during power source switching |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2003101180658A CN100508368C (en) | 2003-11-20 | 2003-11-20 | Noise limiting circuit during power source switching |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1619946A true CN1619946A (en) | 2005-05-25 |
| CN100508368C CN100508368C (en) | 2009-07-01 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2003101180658A Expired - Fee Related CN100508368C (en) | 2003-11-20 | 2003-11-20 | Noise limiting circuit during power source switching |
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| Country | Link |
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| CN (1) | CN100508368C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7974419B2 (en) | 2006-07-06 | 2011-07-05 | Tatung Company | Pop sound prevention module and speaker apparatus thereof |
| CN101111094B (en) * | 2006-07-21 | 2011-09-14 | 大同股份有限公司 | Noise preventing module and its public address set |
| CN102237095A (en) * | 2010-04-22 | 2011-11-09 | 鸿富锦精密工业（深圳）有限公司 | Audio frequency coding/decoding chip output circuit |
-
2003
- 2003-11-20 CN CNB2003101180658A patent/CN100508368C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7974419B2 (en) | 2006-07-06 | 2011-07-05 | Tatung Company | Pop sound prevention module and speaker apparatus thereof |
| CN101111094B (en) * | 2006-07-21 | 2011-09-14 | 大同股份有限公司 | Noise preventing module and its public address set |
| CN102237095A (en) * | 2010-04-22 | 2011-11-09 | 鸿富锦精密工业（深圳）有限公司 | Audio frequency coding/decoding chip output circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100508368C (en) | 2009-07-01 |
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Granted publication date: 20090701 Termination date: 20111120 |