CN201403188Y - POP noise suppression circuit - Google Patents

Abstract

The utility model discloses a POP noise suppression circuit applied to a vehicle-mounted entertainment system, comprising a first switch pipe, a first energy storage capacitor, a second energy storagecapacitor, a discharge diode, a second switch pipe and a third switch pipe, wherein the emitting electrode of the first switch pipe is connected with a loudspeaker power supply through a diode, and the base electrode of the same is connected with the loudspeaker power supply through a series resistor; the first energy storage capacitor is connected between the emitting electrode of the first switch pipe and the ground; the second energy storage capacitor is connected between a connecting point of the series resistor and the ground; the discharge diode is reversely connected between the loudspeaker power supply and the connecting point of the series resistor; the base electrodes of the second switch pipe and the third switch pipe are respectively connected with the collecting electrode ofthe first switch pipe, the collecting electrodes of the second switch pipe and the third switch pipe are respectively connected to the positive end and the negative end of a loudspeaker, and the emitting electrodes of the second switch pipe and the third switch pipe are respectively connected to the ground. The utility model has simple circuit, low cost, can effectively prevent the transient impact of electrification or power failure from enabling the loudspeaker to generate POP noises and reduce the POP noises generated during audio-frequency switching by increasing the filter capacitance value of a reference voltage end, thereby integrally improving the sound effect of the vehicle-mounted entertainment system.

Description

A kind of POP noise reducing circuit

Technical field

The utility model relates to the noise suppression technology, specifically is meant a kind of POP noise reducing circuit that is applied to vehicle entertainment system

Background technology

The POP noise is meant that audio frequency amplifier is powering on or the moment and when in the stable back that powering on it being carried out various operation of cutting off the power supply, and power supply is perhaps exported the explosion sound that the instantaneous charging of capacitance is produced to input capacitance, biased electrical.Because power supply is to producing a peak voltage at the audio frequency amplifier output usually in the instantaneous charging process of electric capacity, this voltage is added in the loud speaker two ends, produces electric current and cutting magnetic line, and this electric current causes loud speaker to send the noise of Pop-click.In the vehicle entertainment system of having used audio frequency amplifier, this noise inevitably has influence on people's hearing enjoying.

The utility model content

At the shortcoming of prior art, the purpose of this utility model provides a kind of noise reducing circuit that is applied to can effectively prevent in the vehicle entertainment system generation of POP noise.

For achieving the above object, the technical scheme of taking of the present utility model is:

A kind of POP noise reducing circuit is provided, and this circuit is connected in the positive and negative two ends of loud speaker, comprises that on/off suppresses the unit and audio frequency switches the inhibition unit.

Described on/off suppresses the unit and comprises first switching tube, and its emitter connects a diode cathode, is connected with the loud speaker power supply by this diode, and its base stage then connects the loud speaker power supply by two resistance of series connection; First storage capacitor, it is connected between the first switching tube emitter and the ground; Second storage capacitor, it is connected between the tie point and ground of described series resistance; Discharge diode, its reversal connection is between the tie point of loud speaker power supply and series resistance; Second, third switching tube, its base stage are connected with the first switching tube collector electrode by resistance respectively, its collector electrode respectively with about two channel speakers anodes be connected the equal ground connection of its emitter.

Described audio frequency switches the inhibition unit and adopts a Da Rong value filtering electric capacity, and it is connected between audio frequency amplifier reference voltage and the ground.

The utility model circuit makes instantaneous all the be in ground state of the positive and negative two ends of loud speaker in power or power-down, the POP noise that the transient impact that can effectively prevent power or power-down produces loud speaker, and by strengthening the filter capacitor appearance value of reference voltage terminal, reduce the POP noise that produces when the normal operating conditions audio frequency switches, integral body has been improved the acoustics of vehicle entertainment system; Its circuit is succinct simultaneously, and cost is low.

Description of drawings

Fig. 1 is that the utility model on/off suppresses the element circuit principle schematic;

Fig. 2 is the operation principle schematic diagram that described audio frequency amplifies chip.

Embodiment

Below in conjunction with drawings and Examples composition of the present utility model and operation principle are described in further detail.

" POP " noise problem appears in general circuit when power or power-down be to be difficult to solve, because there is not the power supply whole system not work, the I/O of MCU is out of hand, even also uncontrollable by software.

With reference to Fig. 1, the utility model has adopted the hardware silence processing method: when loud speaker power vd D connected, electric current passed through the base stage that R4, R3 arrive Q3 simultaneously by the emitter that diode D1 arrives switching tube Q3.Because electric current need be to capacitor C 4 chargings, so just beginning in a period of time that powers on, the base stage of switching tube Q3 is than the low threshold voltage of emitter, therefore Q3 conducting, then the Q3 collector electrode can be exported the high level signal of a period of time, this signal makes switching tube Q1, Q2 conducting, and then loud speaker two ends SPKL, SPKR current potential are dragged down, and has avoided the powered on moment peak voltage to drive the POP noise that loud speaker produces.

When loud speaker power vd D disconnected suddenly, capacitor C 4 was discharged rapidly by diode D2, and this moment, diode D2 forward conduction formed discharge loop by R4; And the electric charge that stores on the capacitor C 3 can not discharge, so occurred pressure reduction between the emitter of switching tube Q3 and the base stage again, then also exporting high level once more makes switching tube Q1 and Q2 conducting in switching tube Q3 conducting, realizes noise suppression.In case after power supply was stable, the base voltage of switching tube Q3 was a little more than emitter, then Q3 ends, and is in high-impedance state, does not influence the operate as normal of loud speaker.

With reference to Fig. 2, be the operation principle schematic diagram of described audio frequency amplification chip, when system works was stablized, reference voltage V BIAS value approximated VDD_AUDIO/2, and the appearance value that increases capacitor C 18 just can reach the purpose of inhibition " POP " noise.Its operation principle is: when holding state switches to operating state, dc offset voltage VBIAS begins to set up, raise gradually from zero, and filter capacitor C18 charged, through behind the certain hour, voltage rises to VDD/2, this moment audio frequency amplify chip U1 just can operate as normal, the audio signal of output swings up and down based on this direct voltage.Equally, when audio frequency amplifies the chip power down or enters holding state, filter capacitor C18 discharge, bias voltage VBIAS begins to descend, and drops to zero gradually from VDD_AUDIO/2.The appearance value that increases VBIAS end filter capacitor C18 can be slowed down rising, the decrease speed of DC reference voltage, plays the effect of minimizing " POP " noise.

In Fig. 2 circuit, R+, R-, L+, L-connect the two-way audio input signal respectively, SPKR, SPKL connect two channel speakers respectively, and C18 mainly works the time-delay that powers on and prevents that the noise of power supply is coupled into Vbias, and the effect of capacitor C 1, C2 is the radio-frequency component that suppresses VBIAS.

" POP " noise was at first caused by output capacitance C16, C17 charging when audio frequency switched, next is irregular the causing of charging order by input capacitance C22-C25 and partially installing capacitor C1, C2, want so to suppress this noise then must guarantee capacitor C 1, C2, C3, C4 charging finish before C18 finished charging.Therefore take all factors into consideration selection and " POP " requirement of noise of other electric capacity, the appearance value scope of filter capacitor C18 is generally got between the 0.1UF-1UF.

Claims (2)

1, a kind of POP noise reducing circuit is connected with the loud speaker two ends, comprises that on/off suppresses the unit and audio frequency switches the inhibition unit, and it is characterized in that: described on/off suppresses the unit and comprises:

First switching tube, its emitter connects a diode cathode, is connected with the loud speaker power supply by this diode, and its base stage then connects the loud speaker power supply by two resistance of series connection;

First storage capacitor, it is connected between the first switching tube emitter and the ground;

Second storage capacitor, it is connected between the tie point and ground of described series resistance;

Discharge diode, its reversal connection is between the tie point of loud speaker power supply and series resistance;

Second, third switching tube, its base stage are connected with the first switching tube collector electrode by resistance respectively, its collector electrode respectively with about two channel speakers anodes be connected the equal ground connection of its emitter;

Described audio frequency switches the inhibition unit and adopts a Da Rong value filtering electric capacity, and it is connected between audio frequency amplifier reference voltage and the ground.

2, POP noise reducing circuit according to claim 1 is characterized in that: described filter capacitor appearance value is 47UF-100UF.

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