Class-D Amplifier Pulse-Width Control for Low Distortion
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Solution Overview
Problem
Conventional class-D amplifiers exhibit non-linear input-output characteristics in large-signal areas, leading to high total harmonic distortion and reduced open-loop gain, while small-signal areas have high power consumption due to narrow pulse widths and overlapping output pulses.
Innovation Solution
A class-D amplifier with a control circuit that adjusts offset voltages based on input signal levels to maintain a high-gain area by varying pulse widths of output pulses, using a control signal to manage pulse widths dynamically and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pulse width becomes narrow in the small-signal area to reduce power consumption, then power consumption is reduced, but the amplifier operates in a high-gain area with non-linear characteristics causing high total harmonic distortion
Solution Approach 1:
The patent applies dynamics by making the offset voltage variable rather than fixed. The control circuit dynamically adjusts the offset voltage based on the input signal level: applying a larger offset in the small-signal area to maintain linear operation, and reducing or eliminating the offset in the large-signal area to maintain efficiency. This dynamic adjustment resolves the contradiction between power consumption and distortion.
Solution Approach 2:
The patent changes the parameter of offset voltage based on signal level. By varying the offset voltage parameter according to input signal amplitude, the system maintains optimal operating conditions across different signal ranges, achieving both low distortion in small-signal areas and efficient operation in large-signal areas.
2Manufacturing precision
If the offset voltage is increased to suppress distortion in the small-signal area, then total harmonic distortion is reduced, but power consumption increases due to wider pulse widths
Solution Approach 1:
The control circuit dynamically adjusts the offset voltage based on input signal level, applying larger offsets only when needed for distortion suppression in small-signal areas, and reducing offsets in large-signal areas to maintain efficiency. This dynamic approach resolves the contradiction between distortion suppression and power consumption.
Solution Approach 2:
The offset voltage parameter is varied according to signal level conditions. The system changes this parameter adaptively: increasing it to suppress distortion when the input signal is small, and decreasing it when the input signal is large to reduce power consumption, thus resolving the contradiction.
3Loss of energy
If the amplifier operates in the large-signal area with wide pulse widths, then power consumption is reduced, but the non-linear characteristics cause high total harmonic distortion
Solution Approach 1:
The system dynamically adjusts the offset voltage based on signal level to maintain linear operation. In large-signal areas where the amplifier naturally operates more efficiently, the control circuit reduces or eliminates the offset voltage, allowing the system to benefit from both low power consumption and acceptable distortion levels.
Solution Approach 2:
The offset voltage parameter is adaptively changed based on operating conditions. In large-signal areas, the parameter is reduced to allow efficient operation while maintaining adequate linearity, resolving the contradiction between power consumption and distortion in this operating region.
Data Source
AI summary
A class-D amplifier that amplifies an input signal comprises a control circuit configured to generate a control signal that varies in accordance with a level of the input signal, a first generating circuit configured to generate a first pulse, and a second generating circuit configured to generate a second pulse. A pulse width of the first pulse becomes narrower as the signal level of the input signal becomes smaller, and the pulse width of the first pulse becomes wider as an instantaneous magnitude of the input signal becomes larger. A pulse width of the second pulse becomes narrower as the signal level of the input signal becomes smaller, and the pulse width of the second pulse becomes wider as an instantaneous magnitude of the input signal becomes smaller.