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Power off delay circuit and method, and audio system with power off delay

a delay circuit and delay technology, applied in the field of audio systems, can solve the problems of reducing the working voltage margin of the internal circuit, unable to maintain the mute function, and lack of sufficient supply voltage, so as to reduce the voltage drop

Inactive Publication Date: 2013-03-14
RICHTEK TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The solution effectively maintains the audio system's internal circuit operation during power off, reducing voltage drop and fluctuations, thereby preventing pop generation and ensuring a stable output signal.

Problems solved by technology

At power off, however, the audio mute IC lacks a sufficient supply voltage to support proper operation of its internal circuit, and is thus hard to maintain its mute function.
However, the diode connected between the external power source and the internal circuit leads to an additional voltage drop, and thus decreases the margin of the working voltage of the internal circuit.

Method used

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  • Power off delay circuit and method, and audio system with power off delay
  • Power off delay circuit and method, and audio system with power off delay
  • Power off delay circuit and method, and audio system with power off delay

Examples

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Embodiment Construction

[0018]FIG. 1 is a block diagram of an audio system using a power off delay circuit of the present invention, in which a POR IC 10 is connected to an external power source Vcc, an external capacitor C, and a plurality of drive transistors M1-MN, each of which is connected to a loudspeaker 12 through an audio line 11. When the POR IC 10 detects an abnormal condition from the external supply voltage Vcc, e.g. power down, a load current I_load is provided to the drive transistors M1-MN from electric charges stored by the capacitor C to pull down the voltage of the audio line 11 to zero, to avoid pop generation. The POR IC 10 includes a power off delay circuit according to the present invention, which delays the timing of internal power off of the POR IC 10 so that the POR IC 10 can still maintain an enough load current I_load for a period of time after the power down of the external power source Vcc. As shown in FIG. 2, a power off delay circuit 14 includes the external capacitor C conn...

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Abstract

A power off delay circuit includes a switch connected between an external power input terminal and an internal power supply terminal, a capacitor connected to the internal power supply terminal, and a hysteresis comparator to switch the switch according to the voltages of the external power input terminal and the internal power supply terminal. During on-time of the switch, the external power input terminal is connected to the internal power supply terminal and the capacitor can be charged by the external power source. When the switch is off, the capacitor provides electric power for an internal circuit. Application of the power off delay circuit to an audio system may eliminate the turn-off pops of the audio system.

Description

REFERENCE TO RELATED APPLICATION[0001]This Application is being filed as a Divisional application Ser. No. 12 / 818,539, filed 18 Jun. 2010, currently pending.FIELD OF THE INVENTION[0002]The present invention is related generally to an audio system and, more particularly, to a power off delay circuit and method for an audio system.BACKGROUND OF THE INVENTION[0003]Conventionally, to avoid pop generation by a loudspeaker of an audio system at power on or power off, an audio mute integrated circuit (IC) is adopted to eliminate pops. At power off, however, the audio mute IC lacks a sufficient supply voltage to support proper operation of its internal circuit, and is thus hard to maintain its mute function. To solve this problem, the supply voltage of the audio mute IC must be given with a longer sustained interval of time at power off so that after the power off, the internal circuit of the audio mute IC can still work normally for a period of time for the audio mute function to come into...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H03F1/30
CPCH02B1/24H04R3/007
Inventor LIN, CHI-HUATANG, CHIEN-FUCHEN, ISAAC Y.CHEN, AN-TUNG
Owner RICHTEK TECH