Multiphase PWM Control for Voltage Regulator Overshoot Limiting
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Solution Overview
Problem
Multiphase switching voltage regulators face challenges in maintaining output voltage within a narrow tolerance band during transient conditions, leading to overshoot and undershoot issues that can damage loads or corrupt data, due to the storage of pending PWM pulses and negative inductor currents.
Innovation Solution
Implementing a method that includes storing and ceasing storage of pending PWM pulses, tri-stating PWM pulses when inductor current reaches zero, and providing truncated PWM pulses during overshoot conditions to prevent excessive energy transfer and manage inductor currents effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pending PWM pulses are stored to improve transient response, then the response speed improves, but output voltage overshoot increases
Solution Approach 1:
The patent applies preliminary action by storing pending PWM pulses in advance to prepare for transient load changes. When a transient condition is detected, the pre-stored pulses are immediately released to achieve fast response. This resolves the contradiction by preparing control actions beforehand, enabling rapid response without waiting for error detection and processing.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the PWM pulse generation based on operating conditions. The system transitions between different PWM modes (continuous PWM, pending pulse release, and cessation of pending pulses) depending on whether the regulator is in transient mode or steady state. This dynamic adaptation allows fast transient response while preventing overshoot during steady-state operation.
2Productivity
If PWM pulses continue to be provided during overshoot conditions, then the control loop remains active, but the overshoot condition worsens
Solution Approach 1:
The patent applies preliminary anti-action by detecting overshoot conditions and immediately providing truncated PWM pulses with reduced duty cycle. This counteracts the overshoot tendency by reducing energy transfer to the output before the overshoot can worsen. The control loop remains active but applies opposing control action to correct the deviation.
Solution Approach 2:
The patent implements partial action by providing truncated PWM pulses instead of full-duty-cycle pulses during overshoot conditions. The pulse width is reduced to a predetermined truncated value that provides just enough control action to correct the overshoot without causing excessive correction or oscillation. This partial action is sufficient to resolve the contradiction.
3Power
If the switching regulator operates in current limit mode with high inductor current, then the power delivery capability improves, but the risk of component stress increases
Solution Approach 1:
The patent applies feedback by continuously monitoring the inductor current and comparing it against a predetermined current limit threshold. When the current exceeds the threshold, the system transitions to current limit mode where pending PWM pulses are ceased. This feedback mechanism ensures power delivery capability is maintained within safe operating limits, preventing excessive component stress while maximizing power transfer.
Data Source
AI summary
In an example, a method includes storing a pending PWM pulse for a switching voltage regulator. The method also includes determining a switching voltage regulator is operating in a current limit mode, where an inductor current is above a current limit threshold. The method includes providing a predetermined number of PWM pulses in the current limit mode. The method also includes, responsive to providing the predetermined number of PWM pulses, ceasing storage of pending PWM pulses for the switching voltage regulator.