CN201967028U - STB silence circuit - Google Patents
STB silence circuit Download PDFInfo
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- CN201967028U CN201967028U CN201020669286XU CN201020669286U CN201967028U CN 201967028 U CN201967028 U CN 201967028U CN 201020669286X U CN201020669286X U CN 201020669286XU CN 201020669286 U CN201020669286 U CN 201020669286U CN 201967028 U CN201967028 U CN 201967028U
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Abstract
The utility model relates to a silence circuit that suppresses STB switching on and shutting down noise. Said circuit is connected with the inside acoustic signal amplifier power supply circuit of STB, and this acoustic signal amplifier power supply circuit includes a triode, the direct-connected power supply power of its collecting electrode, and first ohmic connection power supply power is passed through to the base, and the emitter-base bandgap grading passes through second ohmic connection acoustic signal amplifier power foot; Establish third resistance between first resistance and power supply power, establish first electric capacity between first resistance and the ground, and establish first diode between first resistance and triode collecting electrode. This utility model not only can effectively suppress the noise that produces in the STB switching on and shutting down process, can play the effect of filtering simultaneously again, provides steady, clean power for the audio-frequency amplifier; The circuit is succinct, and is with low costs, easily realizes.
Description
Technical field
The utility model relates to the set-top box technique field, specifically is meant a kind of set-top box mute circuit.
Background technology
Digital TV set-top box is a kind of conversion equipment that digital television signal is converted to analog signal, it is to the reduction of decoding through the image of digitalization compressed and voice signal, produce the video and the voice signal of simulation, provide high-quality TV programme to spectators by television indicator and stereo set.Along with popularizing and development of digital television techniques, top box of digital machine has become the indispensable equipment in many families parlor.But in use also there are some little flaws in existing set-top box, for example, tends to send ear-piercing flip-flop when the set-top box switching on and shutting down, and especially when tv volume being opened very big, this noise is very obvious.
The generation reason of this noise is to adopt 3.3V or the power supply of 5V power supply because be used for digital audio and video signals is converted to the analog-digital chip (DAC) of simulated audio signal in the set-top box, the power amplifier that carries out the audio signal amplification that is connected with analog-digital chip then uses the 12V power supply, little 2 orders of magnitude of equiva lent impedance of the load that the equiva lent impedance of the load that can be with because of 3.3V or 5V power supply can be with than 12V, and differing maximum, the capacitive load of the capacitive load of 12V electric power network and 3.3V or 5V is no more than 1 order of magnitude, therefore, the charging constant of 12V electric power network capacitive load is much smaller than the charging constant of the capacitive load of 3.3V/5V electric power network, when then set-top-box opening was switched on, power amplifier can enter operating state faster than analog-digital chip.
In television boot-strap moment, the television set load end has a positive pulse, this pulse duration is narrower, its energy spectrum mainly is distributed in the low-frequency range that people's ear can be heard, can carry out the transition to a negative pulse then, then this negative pulse width is bigger if the DAC start is just opened moment, and its energy spectrum mainly is distributed in the unheard ultralow frequency range of people's ear.If DAC just opens through after a while after powering on, then this negative pulse width is less, and its energy spectrum is also mainly concentrated to be distributed in the medium and low frequency section that people's ear can be heard, just returns to 0V at last.
On the contrary, be that 3.3V/5V voltage descends prior to 12V during power down, promptly the power down specific power amplifier of DAC is wanted fast (0V is arrived in DAC power down in the side circuit, and power amplifier is also in work).Power down moment a positive pulse can occur at the television set load end, and this pulse duration is narrower, and its energy spectrum mainly is distributed in the low-frequency range that people's ear can be heard, carries out the transition to negative pulse then, just slowly returns to 0V at last.The reason that noise produces when below all being switching on and shutting down.
In the prior art, the circuit of eliminating this sonic boom often complexity and effect is not very good.
Summary of the invention
The problem that the utility model need solve provides a kind of set-top box mute circuit.
For addressing the above problem, the technical scheme that the utility model is taked is: a kind of set-top box mute circuit, be connected with set-top box internal audio frequency signal amplifier power circuit, described audio signal amplifier power circuit comprises a triode, its collector electrode directly connects power supply, base stage connects power supply by first resistance, emitter-base bandgap grading connects the audio signal amplifier supply pin by second resistance, it is characterized in that: between first resistance and power supply, establish the 3rd resistance, establish first electric capacity between first resistance and the ground.
Preferably, establish first diode between first resistance and transistor collector, described first diode cathode connects described transistor collector.
Preferred, be connected to second electric capacity between described power supply and the ground.
Be connected to filter capacitor between described audio signal amplifier supply pin and the ground.
Compared with prior art, the beneficial effects of the utility model are: (1) can effectively suppress the noise that produces in the set-top box switching on and shutting down process, can play simultaneously the effect of filtering again, provide steady, clean power supply to audio signal amplifier, the every index when guaranteeing its work all can reach best values; (2) circuit is succinct, and cost is low, is easy to realize.
Description of drawings
Fig. 1 is the utility model embodiment circuit theory schematic diagram.
Embodiment
The utility model is described in further detail below in conjunction with drawings and Examples.
The bad noise that the utility model produces when being used to suppress the set-top box switching on and shutting down, reason according to this noise generation: promptly power panel provides 12V power supply for the audio signal amplifier chip, because the audio signal amplifier chip generally powers on prior to DAC, cause noise to produce, therefore this circuit is exactly to allow the 12V arrival audio signal amplifier chip in evening as far as possible of supply audio frequency signal amplifier chip power supply, thereby suppress the unlatching operation of audio signal amplifier chip, make the noise that enters the audio signal amplifier chip amplify back output through the audio signal amplifier chip.
As Fig. 1, the audio signal amplifier power circuit adopts triode Q1, and its collector electrode directly connects the 12V power supply, and base stage connects the 12V power supply by first resistance R 2, and emitter-base bandgap grading connects the audio signal amplifier supply pin by second resistance R 3.When powering on, the 12V power supply makes triode Q1 conducting by resistance R 2, and then the 12V power supply is powered to audio signal amplifier by transistor collector, emitter-base bandgap grading.
The set-top box mute circuit that present embodiment disclosed comprises the 3rd resistance R 1, first capacitor C 1 and the first diode D1.Wherein, the 3rd resistance R 1 is connected between first resistance R 2 and the power supply, and first capacitor C 1 is connected between first resistance R 2 and the ground; The first diode D1 is connected between first resistance R 2 and the triode Q1 collector electrode.Be connected to second capacitor C 2 between described power supply and the ground, be connected to filter capacitor C3, C4 between audio signal amplifier supply pin and the ground.
During start, the RC filter circuit that the 12V power supply of coming from power panel forms by resistance R 1 and capacitor C 1 arrives the base stage of triode Q1 again by resistance R 2, the time that the RC filter circuit that is formed by resistance R 1 and capacitor C 1 makes the 12V power supply arrive triode Q1 becomes very long, thereby audio signal amplifier is powered on slowly, can delay the opening time of audio signal amplifier like this, thereby can be input to the noise of audio signal amplifier by audio signal amplifier interception, and then effectively suppress the noise that CPU in the start process or DAC produce.Concrete slack time can be adjusted by the value of resistance R 1 and capacitor C 1, and resistance R 1 and capacitor C 1 play the effect of filtering simultaneously, makes the 12V of supply audio frequency signal amplifier steady more, clean.
Capacitor C 1 can be passed through diode D1 repid discharge during shutdown, capacitor C 1 anodal no-voltage when guaranteeing next the start.Carry out filtering further for again the audio signal amplifier power supply by the RC filter circuit that resistance R 3, capacitor C 3, C4 form.
The foregoing description is the preferred version that the utility model is realized; and indefiniteness is exhaustive; the utility model can also have other variations under same idea; need to prove; under the prerequisite that does not break away from the utility model design, any conspicuous replacement is all within the utility model protection range.
Claims (4)
1. set-top box mute circuit, be connected with set-top box internal audio frequency signal amplifier power circuit, described audio signal amplifier power circuit comprises a triode, its collector electrode directly connects power supply, base stage connects power supply by first resistance, emitter-base bandgap grading connects the audio signal amplifier supply pin by second resistance, it is characterized in that: establish the 3rd resistance between first resistance and power supply, establish first electric capacity between first resistance and the ground.
2. set-top box mute circuit according to claim 1 is characterized in that, establishes first diode between first resistance and transistor collector, and described first diode cathode connects described transistor collector.
3. set-top box mute circuit according to claim 2 is characterized in that, is connected to second electric capacity between described power supply and the ground.
4. set-top box mute circuit according to claim 3 is characterized in that, is connected to filter capacitor between described audio signal amplifier supply pin and the ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201020669286XU CN201967028U (en) | 2010-12-20 | 2010-12-20 | STB silence circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201020669286XU CN201967028U (en) | 2010-12-20 | 2010-12-20 | STB silence circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201967028U true CN201967028U (en) | 2011-09-07 |
Family
ID=44529580
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201020669286XU Expired - Fee Related CN201967028U (en) | 2010-12-20 | 2010-12-20 | STB silence circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201967028U (en) |
-
2010
- 2010-12-20 CN CN201020669286XU patent/CN201967028U/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20110907 Termination date: 20131220 |