PWM Multi-Phase Voltage Converter Phase Transition Control
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Solution Overview
Problem
Multi-phase voltage converters face significant output voltage undershoot during transitions from active to inactive phase circuits, leading to inefficiency and disruption in voltage control, particularly under varying load conditions.
Innovation Solution
The method involves maintaining the equivalent frequency of the converter unchanged by uniformly outphasing the phase currents of active phase circuits and adjusting the switching period based on the number of active phases, using a circuit with a variable clock signal generation to manage the transition, ensuring minimal off-time and updating the switching period as inactive phases are turned off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of active phase circuits is reduced to adapt to load conditions, then power efficiency is improved, but output voltage undershoot increases during transitions
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor before transitioning from N phases to M phases. The control circuit activates the output capacitor charging path before the phase transition occurs, ensuring that the capacitor is ready to supply the required current immediately when phases are deactivated, thereby preventing output voltage undershoot while maintaining power efficiency benefits
Solution Approach 2:
The patent implements beforehand cushioning by using the output capacitor as a buffer energy storage element. The capacitor is charged in advance during normal operation and then discharges to compensate for the current deficit during phase transition, cushioning the impact of reduced active phases and preventing harmful voltage drops
2Loss of energy
If phase circuits are turned off to reduce switching frequency, then power loss is reduced, but output voltage stability deteriorates during transition
Solution Approach 1:
The patent introduces the output capacitor as an intermediary element between the phase circuits and the load. During transitions from N phases to M phases, the capacitor mediates the current delivery, temporarily supplying the difference between load current and reduced phase current, thus maintaining output voltage stability while allowing phase circuits to be turned off for power savings
3Loss of energy
If the switching frequency is reduced during phase transition, then switching losses are decreased, but the response time of voltage compensation increases
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor before the phase transition occurs. This preparation ensures that when the transition happens and switching frequency is reduced, the capacitor is already charged and can immediately compensate for voltage drops, maintaining fast response without incurring high switching losses during the transition
Data Source
AI summary
A circuit may generate a clock signal with a variable period given by a ratio between an initial switching period and a number of phase circuits through which a current of a multi-phase PWM voltage converter flows. The circuit may include an adjustable current generator driven by a signal representing the number of phase circuits through which the current flows and configured to generate a current proportional to the number of phase circuits through which the current flows, and a tank capacitor charged by the adjustable current generator. The circuit may include a comparator of a voltage on the tank capacitor with a threshold value configured to generate a pulse of the clock signal when the threshold value is attained, and a discharge path of the tank capacitor, the discharge path being enabled during the pulses of the clock signal.