GB2280803A - Pop reduction in audio amplifier for a TV receiver - Google Patents

Pop reduction in audio amplifier for a TV receiver Download PDF

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Publication number
GB2280803A
GB2280803A GB9315436A GB9315436A GB2280803A GB 2280803 A GB2280803 A GB 2280803A GB 9315436 A GB9315436 A GB 9315436A GB 9315436 A GB9315436 A GB 9315436A GB 2280803 A GB2280803 A GB 2280803A
Authority
GB
United Kingdom
Prior art keywords
receiver
capacitor
diode
pin
voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9315436A
Other versions
GB9315436D0 (en
Inventor
Siew Hong Soo
Chun Hung Wu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Technicolor SA
Technicolor USA Inc
Original Assignee
Thomson Consumer Electronics SA
Thomson Consumer Electronics Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thomson Consumer Electronics SA, Thomson Consumer Electronics Inc filed Critical Thomson Consumer Electronics SA
Priority to GB9315436A priority Critical patent/GB2280803A/en
Publication of GB9315436D0 publication Critical patent/GB9315436D0/en
Publication of GB2280803A publication Critical patent/GB2280803A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
    • H03G3/348—Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits

Abstract

A TV receiver includes an integrated circuit fed by the IF sound signal and feeding a loudspeaker. For volume control an adjustable control voltage is fed to pin (1) of said IC. When the receiver is switched from ON to OFF by interrupting the main supply, pop noise occurs. Pin (1) of said IC, to which said volume control voltage (Uc) is supplied, is connected to a second source of dc voltage (9V) via the series circuit of a second capacitor (C1) and a resistor (R1) which is shunted by a diode (D1). During normal operation said diode (D1) is in OFF condition. When the receiver is switched off, said diode (D1) becomes conductive and discharges the capacitor (C2) at said control pin (1) rapidly so that no pop signal can arise at the loudspeaker (5). <IMAGE>

Description

Audio amplifier for a TV receiver The invention relates to an audio amplifier for a TV receiver according to the introductory part of claim 1.
Within a TV receiver during switching from ON to OFF an audible disturbance within the reproduced sound occurs, which generally is called "POP". This disturbance in form of a click is due to a sudden change in the operating voltage fed to the sound intermediate frequency amplifier IC. According to prior art capacitors are introduced to prevent such a sudden change in operating voltage. However, such known circuits do not operate sufficiently so that in most cases an undesirable pop remains.
It is an object of the invention to provide a simple circuit for the sound intermediate frequency amplifier in such a way that such disturbances in audio reproduction like pop do not occur or remain inaudible.
The invention relates to an audio amplifier for a TV receiver including an integrated circuit feeding the loudspeaker and having an input terminal being connected to ground via a capacitor and to a source of adjustable control voltage for volume control. According to the invention said terminal is connected to a second source of dc voltage via the series circuit of a second capacitor and a resistor which is shunted by a diode. Preferably said second capacitor is an electrolytic capacitor and said diode is a fast switching diode.
The invention reduces the dc volume to almost zero so as to reduce the amplitude of the unstable audio output across the loudspeaker to a level that is no more audible. The invention has solved the pop sound problem when the TV receiver is switched from ON to OFF by ac main supply.
In order that the invention may be better understood and easily carried out in practise an embodiment of the invention is described in connection with the accompanying drawing. In the drawing the single figure shows an integrated circuit for feeding a loudspeaker within a TV receiver.
The integrated circuit 3 shown in the figure is fed via pin 6 with the IF sound signal and via pin 2 with the operating voltage UB. Pin 4 of IC 3 feeds the demodulated audio frequency signal to loudspeaker 5. A volume control voltage Uc is fed to pin 1 of IC 3. Said control voltage Uc is derived from potentiometer R3 for volume control and fed via resistor R2 to pin 1 which is connected to ground by capacitor C2. Pin 1 of the IC 3 is further connected via the series circuit of capacitor C1 and resistor R1 to an operating voltage of +9V, resistor R1 being shunted by diode D1. During volume control Uc at pin 1 varies between +2V and +7V.
The operation of said circuit is the following. When the TV receiver is turned on, capacitor C1 is charged up through resistor R1 with a time constant T=R1 x C1. As Uc varies between +2V and +7V and cathode of D1 is connected to +9V, D1 will not conduct during the TV receiver is turned on. That means that circuit R1, C1, D1 has no influence on the operation and the volume control by Uc. When the TV receiver is switched from ON to OFF, the +9V voltage will drop much faster than the volume control voltage Uc. Volume control voltage Uc will drop much slower due to the long RC time constant provided by large capacitor C2. Due to the rapid drop of the +9V voltage diode D1 will conduct so that the charge in capacitor C1 causes the volume control voltage Uc at pin 1 of IC 3 to drop rapidly and reduce the amplitude of the unstable audio output at pin 4 to an unaudible level.
In a practically tested embodiment of the circuit according to the figure, the element shown had the following values: Resistor R1 : 33 kOhm Resistor R2 : 12 kOhm Capacitor C1 : electrolytic capacitor with 47 F Capacitor C2 : electrolytic capacitor with 10 F Diode D1 : Type 1N4148 IC 3 : one chip IC N52303ASP

Claims (3)

  1. Claims 1. Audio amplifier for a television receiver including an integrated circuit (3) feeding the loudspeaker (5) and having an input terminal (1) being connected to ground by a first capacitor (C2) and to a source of adjustable control voltage (Uc) for volume control characterised in that said terminal (1) is connected to a second source of dc voltage (9V) via the series circuit of a second capacitor (C1) and a resistor (R1) which is shunted by a diode (D1).
  2. 2. Amplifier according to claim 1, characterised in that said capacitor (C1) is an electrolytic capacitor.
  3. 3. Amplifier according to claim 1, characterised in that said diode (D1) is a fast switching diode.
GB9315436A 1993-07-26 1993-07-26 Pop reduction in audio amplifier for a TV receiver Withdrawn GB2280803A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9315436A GB2280803A (en) 1993-07-26 1993-07-26 Pop reduction in audio amplifier for a TV receiver

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9315436A GB2280803A (en) 1993-07-26 1993-07-26 Pop reduction in audio amplifier for a TV receiver

Publications (2)

Publication Number Publication Date
GB9315436D0 GB9315436D0 (en) 1993-09-08
GB2280803A true GB2280803A (en) 1995-02-08

Family

ID=10739439

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9315436A Withdrawn GB2280803A (en) 1993-07-26 1993-07-26 Pop reduction in audio amplifier for a TV receiver

Country Status (1)

Country Link
GB (1) GB2280803A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0862265A2 (en) * 1997-02-26 1998-09-02 THOMSON multimedia Anti pop for power off
EP1635455A1 (en) * 2004-09-09 2006-03-15 ORION ELECTRIC CO., Ltd. Mute circuit

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2251350A (en) * 1990-10-10 1992-07-01 Thomson Consumer Electronics Muting circuit
US5199079A (en) * 1991-05-21 1993-03-30 Thomson Consumer Electronics, Inc. Supply voltage responsive audible transient (POP) suppression arrangement

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2251350A (en) * 1990-10-10 1992-07-01 Thomson Consumer Electronics Muting circuit
US5199079A (en) * 1991-05-21 1993-03-30 Thomson Consumer Electronics, Inc. Supply voltage responsive audible transient (POP) suppression arrangement

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0862265A2 (en) * 1997-02-26 1998-09-02 THOMSON multimedia Anti pop for power off
GB2322746A (en) * 1997-02-26 1998-09-02 Thomson Multimedia Sa Preventing pop noise in TV sound
EP0862265A3 (en) * 1997-02-26 2000-01-12 THOMSON multimedia Anti pop for power off
US6516067B1 (en) 1997-02-26 2003-02-04 Thomson Licensing, S.A. Anti pop for power off
EP1635455A1 (en) * 2004-09-09 2006-03-15 ORION ELECTRIC CO., Ltd. Mute circuit

Also Published As

Publication number Publication date
GB9315436D0 (en) 1993-09-08

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Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)