Audio Output Driver Sequencing to Reduce Power-On Pop Noise
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Solution Overview
Problem
Existing signal processing devices in image display apparatuses struggle to effectively reduce pop noise and harmonic distortion when power is turned on, and they also face challenges in minimizing circuit size.
Innovation Solution
The proposed solution involves a signal processing device with an amplifier, an output driver, a reference voltage output device, a pre-output driver, and switching devices. The output driver operates after the first switching device is turned on in response to power ON, and the pre-output driver compensates for offset voltage to prevent rapid voltage changes at the output terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If power is turned on instantaneously, then the device starts operating quickly, but pop noise and harmonic distortion occur due to instantaneous voltage changes
Solution Approach 1:
The patent applies preliminary action by enabling the output driver before the amplifier during power-on. This sequence allows the output driver to be ready to handle any voltage spikes or transient signals before the amplifier becomes active, thereby preventing pop noise and harmonic distortion from occurring when power is applied. The controller coordinates this staged activation to ensure smooth power-on without instantaneous voltage changes affecting the output.
2Object-generated harmful factors
If complex noise reduction circuits are added, then pop noise and harmonic distortion are reduced, but circuit size increases
Solution Approach 1:
The patent employs dynamics by implementing controllable switching of the amplifier and output driver based on power-on/power-off detection. Instead of using complex passive noise reduction circuits, the system dynamically adjusts the operational state of active components through a controller that detects power transitions and sequentially enables/disables the amplifier and output driver. This dynamic control approach reduces noise without adding bulky passive circuitry.
Solution Approach 2:
The patent applies parameter changes by altering the operational parameters (on/off state) of the amplifier and output driver in a specific sequence during power transitions. The controller changes the activation timing of these components - enabling the output driver first during power-on and disabling it last during power-off - to minimize noise generation. This parameter control method achieves noise reduction without increasing circuit complexity.
3Speed
If the output driver operates simultaneously with the amplifier during power ON, then the device responds quickly, but offset voltage causes rapid voltage changes at the output terminal
Solution Approach 1:
The patent applies preliminary action by activating the output driver before the amplifier during power-on. This sequencing ensures that the output driver is already operational and ready to properly drive the output signal when the amplifier becomes active, preventing rapid voltage changes caused by offset voltage. The controller coordinates this staged activation to maintain both speed and stability.
Solution Approach 2:
The patent implements beforehand cushioning by having the output driver operational before the amplifier activates during power-on. This preparatory state of the output driver acts as a cushion against potential voltage instability that would occur if both components started simultaneously. The output driver's early activation prevents offset voltage from causing rapid output voltage changes, ensuring smooth transitions.
Data Source
AI summary
Disclosed are a signal processing device and an image display apparatus including the same. The signal processing device includes an amplifier to perform amplification based on an input differential signal, an output driver to output an audio output signal based on an output signal from the amplifier, a reference voltage output device to output a reference voltage in response to power ON, a pre-output driver configured to pre-compensate for an offset voltage and output a compensation signal, based on an output signal from the amplifier after the power ON, and a first switching device disposed between an output terminal of the output driver and an output terminal of the pre-output driver, wherein the output driver operates after the first switching device is turned on in response to the power ON. Accordingly, pop noise and harmonic distortion in case in which power is turned on may be reduced.