Closed-Loop DAC Switching for Glitch-Free Amplifier Output
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Solution Overview
Problem
Amplifier systems using digital-to-analog converters (DACs) in closed loop regulated supplies often experience glitching, which is undesirable, especially when transitioning between operating modes, leading to output ripple and aberrations.
Innovation Solution
The implementation of a closed loop amplifier system with multiple DACs and an auxiliary DAC to generate reference levels, allowing for seamless switching between high voltage low-resolution and low voltage high-resolution modes without inducing glitches, using a control circuit to adjust DAC codes and introduce voltage offsets to mitigate high-glitch transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single DAC is used in closed loop regulated supply, then the device complexity is low, but the dynamic range is limited and glitching occurs when transitioning between operating modes
Solution Approach 1:
The patent divides the DAC system into multiple segments: a first DAC for high voltage low-resolution mode and a second DAC for low voltage high-resolution mode. This segmentation allows the system to achieve extended dynamic range by switching between different DAC segments based on operating conditions, resolving the contradiction between limited dynamic range and low device complexity.
Solution Approach 2:
The patent implements a universal DAC system where the first and second DACs can operate independently or in combination to serve multiple functions: high voltage operation, low voltage operation, and intermediate voltage operation. This multi-functionality allows a single DAC system to cover the entire dynamic range required by the load, eliminating the need for separate DAC systems for different voltage ranges.
2Measurement precision
If DAC codes are changed to adjust output voltage, then the output voltage can be regulated, but glitching and output ripple occur during code transitions
Solution Approach 1:
The patent employs preliminary action by predicting potential glitch conditions before they occur. The glitch prediction logic monitors DAC code changes and identifies transitions that would cause harmful glitches. Before executing the code change, the system prepares mitigation strategies such as adjusting the second DAC code or modifying the transfer function, thereby preventing glitching and output ripple while maintaining precise output voltage regulation.
Solution Approach 2:
The patent implements feedback mechanisms where the output voltage is continuously monitored and fed back to the control logic. When a glitch condition is detected or predicted, the feedback loop adjusts the DAC codes or transfer function to eliminate the glitch while maintaining the desired output voltage. This closed-loop feedback ensures precise voltage regulation without the harmful effects of uncorrected glitching.
3Stability of the object's composition
If the transfer function is changed to mitigate glitches, then output stability is improved, but the system response time may be affected
Solution Approach 1:
The patent employs dynamic adjustment of the transfer function based on operating conditions. The control logic selectively modifies the transfer function only when glitch conditions are predicted or detected, rather than maintaining a fixed transfer function. This dynamic approach allows the system to optimize for stability when needed while maintaining faster response times during normal operation, resolving the contradiction between output stability and system response time.
Data Source
AI summary
A method of feedback control of an amplifier system includes driving multiple amplifier circuits using at least one digital-to-analog converter (DAC) circuit to set a system output of the amplifier system, operating the at least one DAC circuit using a first set of DAC codes to set the system output to a steady state target output, detecting a high glitch transition of the first set of DAC codes that is greater than a specified threshold transition, and changing to operating the at least one DAC circuit using a second set of DAC codes to set the system output to substantially the same steady state target output, wherein operating the at least one DAC circuit using the second set of DAC codes reduces glitch energy at the output of the at least one DAC circuit.