Muting circuit of network-version STB (set top box)

Abstract

The invention discloses a muting circuit of a network-version STB (set top box), which comprises an active muting control circuit, a power-on impact noise eliminating control circuit, a power-off impact noise eliminating control circuit, and a public portion of the muting circuit, wherein the active muting control circuit, the power-on impact noise eliminating control circuit and the power-off impact noise eliminating control circuit are respectively connected with the public portion of the muting circuit; the active muting control circuit is connected with the power-off impact noise eliminating control circuit; and the power-off impact noise eliminating control circuit is connected with the power-on impact noise eliminating control circuit. The invention provides a muting circuit of a network-version STB (set top box), by which power-on / off impact noises can be perfectly eliminated; meanwhile, a power supply design is reasonable, and the reliability of the circuit is strong.

Description

【Technical field】 [0001] The invention relates to a mute circuit, in particular to a mute circuit of a network version set-top box. 【Background technique】 [0002] In the embedded audio and video circuit, the mute function needs to meet the user's needs for mute, and it must play a role in mute when the switcher, standby, power on and off, and software start. Generally, software can be used to control the audio decoding process or control the audio digital-to-analog converter DAC to realize the mute function, but these two methods are not easy to realize in terms of controlling the noise when the switch is turned on and the audio digital-to-analog converter DAC is started, resulting in unsatisfactory mute effects . [0003] In the existing mute control circuit, when the user turns on or off or the audio digital-to-analog converter DAC inside the main chip starts, the power supply transitions from a transient state to a steady state, and the noise inside the circuit is ampli...

AI Technical Summary

Problems solved by technology

However, since the power-on / off impact noise elimination control circuit belongs to the hardware mute, it can only solve the instantaneous noise problem. After the system is up, if you want to mute for a relatively long time, you need to actively mute through the software.

[0006] The technical solution of the above-mentioned patent also has the following disadvantages: 1. The power supply used by the three parts is VCC_Audio, which is theoretically unreasonable , because the power-on shock noise cancellation control circuit hopes to use the group of power supplies that are powered on the earliest, and the shutdown shock noise cancellation control circuit hopes to use the group of power supplies that are powered off the fastest

2. The role of the active mute control circuit in this circuit is limited to the mute after the system is up, and it has no effect on the moment when the system is powered on.

3. There are design flaws in the power-on impact noise elimination control circuit, and the capacitor CD2 cannot be fully charged, resulting in unreliable power-on mute. In the case of fluctuations in VCC_Audio, abnormal mute actions may occur

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