Switched Capacitor Converter PFM Control for Light-Load Efficiency
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Solution Overview
Problem
Switched capacitor DC/DC converters in single-cell battery systems operate inefficiently at light loads due to high quiescent current consumption, leading to reduced battery life and inefficiency, while dual-cell systems face challenges with large input currents and customized USB connectors.
Innovation Solution
Implementing a pulse frequency modulation (PFM) mode operation in switched capacitor converters, controlled by a circuit with a one-shot circuitry and PFM mode comparator, which detects trailing currents and output currents to switch between PFM and open-loop modes, reducing quiescent current consumption and maintaining output voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switched capacitor DC/DC converters operate in open-loop mode for fast charging, then charging speed is improved, but quiescent current consumption increases significantly at light loads
Solution Approach 1:
The patent implements dynamic mode switching between open-loop and PFM operations based on real-time load conditions. The control circuit detects trailing current and automatically transitions between operating modes, making the system adaptive rather than static. This resolves the contradiction by using open-loop mode for fast charging when needed and PFM mode for energy efficiency at light loads.
Solution Approach 2:
The patent changes the operational parameters of the switched capacitor converter by introducing PFM mode with variable switching frequencies. The control circuit adjusts the switching frequency and duty cycle dynamically based on load conditions, allowing the system to optimize between speed and energy consumption by varying operational parameters rather than maintaining fixed open-loop parameters.
2Loss of energy
If dual-cell battery system is used to reduce input current, then power dissipation is reduced, but system complexity increases
Solution Approach 1:
The patent designs a universal control circuit that can operate with both single-cell and dual-cell battery configurations. The same PFM control circuitry adapts to different battery arrangements, making the power management system multi-functional. This resolves the contradiction by providing a single solution that works across different battery configurations without requiring separate complex control systems for each case.
3Duration of action of stationary object
If PFM mode is implemented to reduce power consumption, then battery life is extended, but output voltage stability becomes more challenging to maintain
Solution Approach 1:
The patent implements feedback control through the PFM control circuit that continuously monitors trailing current and adjusts switching parameters accordingly. This feedback mechanism ensures output voltage stability is maintained while operating in PFM mode, resolving the contradiction by using intelligent control to balance battery life extension with voltage regulation requirements.
Solution Approach 2:
The patent replaces complex analog voltage regulation mechanisms with a digital/PFM-based control system. The control circuit uses timing-based switching and frequency modulation to achieve voltage regulation, substituting traditional mechanical or analog regulation methods with more efficient electronic control that better maintains stability while reducing power consumption.
Data Source
AI summary
A control circuit is configured to control a switched capacitor converter to operate in a pulse frequency modulation (PFM) mode. The control circuit includes a one-shot circuitry configured to generate a one-shot pulse to drive the switched capacitor converter to operate in the PFM mode. A PFM mode comparator is coupled to the one-shot circuitry, and is configured to trigger, based on an output voltage of the switched capacitor converter, the one-shot circuitry to generate the one-shot pulse. The switched capacitor converter may be controlled to exit or continue the PFM mode operation based on a trailing current flowing through a flying capacitor of the switched capacitor converter, an output current of the switched capacitor converter, a time interval of charging the flying capacitor, or a PFM switching period of the switched capacitor converter operating in the PFM mode. Corresponding controlling methods are also provided.