Digital Amplifier Three-Value Output With Dead-Time Noise Reduction
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Solution Overview
Problem
Conventional digital amplifiers outputting three-value signals suffer from significant noise due to common mode noise, which increases noise radiation and requires costly countermeasures like shielding and filters, especially in environments with stringent noise regulations such as on-vehicle environments.
Innovation Solution
A digital amplifier design that incorporates a switch control circuit to manage three switches, ensuring a period where all switches are turned off during switching operations, and utilizes signal output circuits for both positive and negative electrodes that output inverted three-value signals based on differential outputs, reducing common mode noise by operating switches with a switch control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If three-value signals are output in a digital amplifier, then power consumption is reduced, but noise occurs due to switching operations
Solution Approach 1:
The patent extracts and eliminates the harmful switching noise by introducing a dead time period where all switches are turned off simultaneously. This removes the noise-generating switching transitions while preserving the three-value signal output functionality, thereby maintaining low power consumption without the harmful noise side effect
Solution Approach 2:
The patent converts the potentially harmful switching noise into a beneficial dead time period. By intentionally creating a noise-free interval between switching operations, the system uses the switching transition itself to establish a noise-reduction mechanism, where the off-state of all switches serves to suppress common mode noise while maintaining the energy-efficient three-value output
2Speed
If three-value output is executed without a dead time period, then switching speed is improved, but common mode noise increases
Solution Approach 1:
The patent introduces a dead time period as an intermediary element between switching operations. This intermediate off-state acts as a mediator that prevents direct interaction between opposing switch transitions, thereby eliminating common mode noise generation while maintaining acceptable switching speed for audio signal reproduction
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3
AI summary
Noise is reduced when three-value output is performed. In a digital amplifier 1, a three-value driver 18a associated with a positive electrode and a three-value driver 18b output three-value signals which are inverted to each other, and execute an output of three values on the basis of a differential output of the positive electrode and a negative electrode.