Patent ID: 7519190
Filing Date: 2009-04-14
Classification: H03G

Abstract:
1. A noise reduction circuit for reducing pulse noise caused at switching of an analog audio processing circuit, comprising a voltage division resistor circuit, an end of the voltage division resistor circuit being electrically connected to an output end of a switching circuit of the analog audio processing circuit, and another end of the voltage division resistor circuit being electrically connected to a reference voltage; a plurality of voltage-division points of the voltage division resistor circuit are connected respectively with a plurality of controllable switches, while other ends of the plurality of controllable switches are connected together to form an output end; a first one of the controllable switches serves as a master control switch, during switching of the switching circuit, the master control switch will firstly be turned off automatically for a while, and then the rest controllable switches will be controlled sequentially by a series of continuous short pulses, so that the rest controllable switches are turned on and then turned off, starting from the second switch to the last switch, afterwards, the rest controllable switches are turned on and turned off again, starting from the last switch to the second switch; and finally the master control switch is turned on, and thus the switching of the analog audio processing circuit is accomplished without causing pulse noise.