Variable Rate Integrator for Power Regulator Settling
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Solution Overview
Problem
In power regulators, the integrator path absorbs unnecessary error during load transients, leading to slow settling and potential overshoot, as the existing proportional-integral control loop's integrator time constant is not optimally managed, causing inefficiencies in voltage regulation.
Innovation Solution
A variable rate integrator is implemented, increasing the integrator time constant during undershoot conditions and reducing it afterward based on the inductor and output filter capacitor configuration, allowing the integrator to be placed in a low time constant mode until a defined number of PWM pulses occur, thereby reducing drift and settling time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a fixed integrator time constant is used in the proportional-integral control loop, then the control loop is simple to implement, but the settling time is prolonged and overshoot occurs during load transients
Solution Approach 1:
The integrator time constant is made variable rather than fixed. The control circuit dynamically adjusts the integrator time constant based on the operating state: using a first integrator time constant during steady state conditions and a second integrator time constant during transient conditions. This dynamic adjustment reduces settling time during transients while maintaining stability during steady state, resolving the contradiction between simple implementation and fast settling.
Solution Approach 2:
The patent changes the parameter of integrator time constant from a fixed value to a variable value that adapts to different operating conditions. By detecting whether the system is in steady state or transient mode and selecting appropriate time constant values, the system achieves fast settling during transients without compromising steady-state stability, thus resolving the time-loss versus complexity contradiction.
2Reliability
If the integrator absorbs error during load transients, then the output voltage is regulated, but the integrator causes slow settling and potential overshoot
Solution Approach 1:
The integrator's time constant is dynamically adjusted based on system state. During transient conditions, a shorter second time constant is used to reduce the integrator's error absorption effect, enabling faster settling and preventing overshoot. During steady state, a longer first time constant maintains proper voltage regulation. This dynamic behavior resolves the contradiction between reliable regulation and fast settling.
3Stability of the object's composition
If a longer integrator time constant is used, then steady state stability is maintained, but the settling time during transients is prolonged
Solution Approach 1:
The system uses two different integrator time constants: a first time constant for steady state that maintains stability, and a second time constant for transient conditions that enables fast settling. The control circuit detects the operating state and switches between time constants accordingly, thus achieving both steady-state stability and fast transient response without compromise.
Solution Approach 2:
The integrator time constant parameter is changed based on operating conditions. By selecting an appropriate time constant value (first or second) depending on whether the system is in steady state or transient mode, the patent achieves optimal performance for each condition, resolving the contradiction between stability and settling speed.
4Loss of time
If a shorter integrator time constant is used during transients, then settling time is reduced, but steady state operation may become unstable
Solution Approach 1:
The control circuit dynamically selects the integrator time constant based on system state. The shorter second time constant is used only during transient conditions to achieve fast settling, while the longer first time constant is used during steady state to maintain stability. This conditional, dynamic approach allows the system to benefit from both short and long time constants without the drawbacks of either used exclusively.
Data Source
AI summary
In described examples of a system having a proportional-integral control module, an error signal is produced that is indicative of a difference between a reference signal and an output signal. An integral control signal is produced by integrating the error signal using an integrator time constant value. During a steady state condition, a first integrator time constant value is used. When an undershoot in the output signal is detected, the integrator time constant value is increased to a second time constant value that is larger than the first integrator time constant value during the undershoot condition. The integrator time constant value is reduced to a third integrator time constant value that is less than the first integrator time constant value during a period following the undershoot condition.