Switching Amplifier Feedback Clamping for Saturation Distortion
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Solution Overview
Problem
Class D amplifiers experience output distortion due to the extra time required to discharge capacitors and transition from an open loop to a closed loop state when the output level reaches its maximum, causing deviations from the ideal waveform.
Innovation Solution
A switching amplifier with an integration circuit, comparison circuit, and feedback circuit that clamps the integration result to a predetermined value, generating a feedback signal to maintain the operational amplifier in a closed loop state, thereby preventing current flow to the capacitor and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output level of the D type amplifier reaches the maximum value, then the output signal is saturated, but the operational amplifier operates in an open loop state causing extra discharging time and output distortion
Solution Approach 1:
The feedback circuit performs preliminary action by clamping the integration result to a predetermined value before the operational amplifier enters the open loop state. This prevents the capacitor from discharging and the operational amplifier from transitioning to open loop, eliminating the need for extra discharging time and maintaining continuous closed loop operation.
Solution Approach 2:
The feedback circuit continuously monitors the integration result and provides real-time feedback control. When the integration result reaches the predetermined value, the feedback circuit immediately clamps it, ensuring the operational amplifier remains in closed loop state and preventing the time loss and distortion associated with open loop transitions.
2Measurement precision
If the output level of the integrator reaches the maximum value, then the charging current lowers the input signal level, but the operational amplifier operates in open loop state causing distortion
Solution Approach 1:
The feedback circuit provides continuous monitoring and control of the integration result. When the integration result reaches the predetermined value, the feedback circuit clamps it immediately, preventing the charging current from lowering the input signal level and avoiding the operational amplifier entering open loop state, thus eliminating output distortion.
Solution Approach 2:
The feedback circuit applies preliminary anti-action by clamping the integration result before the charging current can significantly lower the input signal level. This prevents the harmful effect of input signal level reduction and the subsequent open loop operation that causes distortion.
3Ease of operation
If the system needs to lower the output signal, then the capacitor must be discharged to recover the operational amplifier state, but this wastes extra time and causes deviation from ideal state
Solution Approach 1:
The feedback circuit performs preliminary action by clamping the integration result to the predetermined value when it reaches this level. This prevents the capacitor from charging to maximum and eliminates the need for subsequent discharging operations, allowing the operational amplifier to remain in closed loop state without recovery time delays.
Solution Approach 2:
The feedback circuit ensures continuous closed loop operation by preventing the operational amplifier from entering open loop state. The integration result is continuously controlled within the predetermined range, maintaining uninterrupted feedback control and eliminating idle recovery periods.
4Reliability
If the feedback circuit clamps the integration result to a predetermined value, then the operational amplifier remains in closed loop state, but this requires additional feedback circuit components
Solution Approach 1:
The feedback circuit uses standard feedback control components to monitor the integration result and provide clamping control. This implementation achieves improved feedback system stability through continuous monitoring and control, while using conventional circuit elements that minimize added complexity.
Data Source
AI summary
A switching amplifier includes an input end for receiving an input signal, a reference signal reception end for receiving a reference signal, a feedback end for receiving a feedback signal, an output end for outputting an output signal, an integration circuit for performing integration operation on the input signal according to the output signal and the feedback signal, so as to generate an integration result, a comparison circuit coupled to the integration circuit, the reference signal end, and the output end, for comparing the integration result and the reference signal, so as to generate the output signal for the output end, and a feedback circuit coupled between an output end of the integration circuit and the feedback end, for generating the feedback signal for the feedback end to clamp the integration result to a predetermined value when the integration result reaches the predetermined value.