Digital Pre-compensation for Voltage Slewing in Power Converters
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Solution Overview
Problem
Conventional power management systems face limitations in rapidly responding to changes in desired output voltage due to impedances, leading to lag and overshoot, which hinders power savings and efficiency in modern electronic systems.
Innovation Solution
A clocked control logic circuit adjusts the slew rate of the digital-to-analog converter input to compensate for system dynamics by applying different slew rates during the transition period, including a steeper-than-nominal and flatter-than-nominal rate, to achieve a more precise and rapid change in output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional power management systems use standard impedance-based control, then system stability is maintained, but response speed to voltage changes is limited causing lag and overshoot
Solution Approach 1:
The system pre-calculates and stores compensation values in lookup tables before voltage transitions occur. When a voltage change is detected, the pre-computed compensation data is immediately applied to the DAC input, eliminating the need for real-time complex calculations and enabling faster response without compromising stability.
Solution Approach 2:
The invention dynamically adjusts the slew rate parameter of the DAC input signal based on the magnitude and direction of voltage transitions. By changing the rate of voltage change parameter in real-time, the system optimizes both response speed and stability, preventing overshoot while minimizing lag.
2Loss of time
If the slew rate is increased to reduce lag, then response speed improves, but overshoot increases causing instability
Solution Approach 1:
The compensation approach applies different slew rate adjustments to different portions of the voltage transition. Early in the transition, a higher slew rate is applied to reduce lag, while near the target voltage, the slew rate is reduced to prevent overshoot. This localized adjustment of signal characteristics optimizes both speed and stability.
Solution Approach 2:
The system continuously monitors the actual voltage output and compares it with the target voltage. Based on this feedback, the compensation logic dynamically adjusts the DAC input slew rate, reducing it when approaching the target to eliminate overshoot while maintaining fast response during the main transition phase.
3Measurement precision
If complex compensation circuits are added to improve response accuracy, then precision improves, but device complexity increases
Solution Approach 1:
Instead of using complex analog compensation circuits, the invention creates a digital model of the system dynamics and stores compensation characteristics in lookup tables. This digital copy of the compensation behavior is then applied through standard digital-to-analog conversion, achieving high precision without additional complex analog components.
Solution Approach 2:
The invention replaces complex analog compensation circuitry with digital signal processing. By using digital logic and lookup tables to generate compensation signals, the system achieves the same or better precision while reducing circuit complexity and improving programmability.
Data Source
AI summary
Control logic for producing a digital input to a digital-to-analog converter (DAC) in a power converter system. The control logic selects from among a plurality of slew rates during a transition of an output voltage in response to a change in the desired setpoint, so that the output voltage transition follows a desired nominal slew rate. In an initial interval of the transition, a steeper slew rate than the nominal slew rate is selected by the control logic for the digital input to the DAC, until the digital input to the DAC exceeds the nominal slew rate by a first parameter value. At that point, a slew clamp is applied to advance the digital input at the nominal slew rate. Upon the digital input approaching the setpoint value to within a second parameter value, a flatter slew rate than nominal is applied.