Dual Mode Charge Pump with Transitional Current Limiting
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Solution Overview
Problem
Dual rail charge pumps are inefficient when used to power circuitry that amplifies signals with amplitudes much smaller than the power supply, as most output power is wasted in producing heat rather than driving the signal, and they often require large decoupling capacitors to manage current transitions between modes.
Innovation Solution
A dual mode charge pump circuit that operates in two modes, with a transitional mode to manage current flow by restricting current during mode transitions, using a constant current source or current limiting switch to prevent large currents from the input supply, and alternately connecting a flying capacitor to reservoir capacitors to maintain voltage equality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dual rail charge pump operates in full output range mode, then voltage output capability is improved, but power efficiency deteriorates
Solution Approach 1:
The charge pump circuit dynamically switches between two operational modes (full output range mode and reduced output voltage mode) based on the actual signal amplitude requirements. This dynamic adaptation allows the circuit to maintain high efficiency when full voltage is not needed, while still providing the capability to output full voltage when required, thus resolving the contradiction between versatility and energy efficiency.
2Speed
If charge pump transitions between modes directly, then mode switching speed is improved, but current stability deteriorates
Solution Approach 1:
The circuit performs preliminary actions during mode transitions by using transitional modes that gradually adjust the output voltage and current levels. Before fully switching to a new mode, the circuit prepares by incrementally changing operating parameters, which prevents sudden current spikes or drops and maintains current stability throughout the transition process.
Solution Approach 2:
Transitional modes act as intermediaries between full output range mode and reduced output voltage mode. These intermediate states provide a smooth bridge during mode transitions, allowing the circuit to change modes without abrupt current variations. The transitional modes mediate the switch by progressively adjusting voltage and current levels, thus maintaining stability while enabling mode changes.
3Stability of the object's composition
If large decoupling capacitors are used, then current transition management is improved, but device complexity deteriorates
Solution Approach 1:
The circuit manages current transitions by changing operational parameters (voltage levels, switching sequences, current limiting) during transitional modes rather than relying on large decoupling capacitors. This parameter-based approach to current management achieves stable transitions without requiring additional large capacitor components, thus reducing device complexity while maintaining current stability.
Data Source
AI summary
A method of generating a voltage supply (Vout+, Vout−) from a single input supply (+VDD), comprising connecting at least one flying capacitor (Cf) to at least one reservoir capacitor (CR1, CR2) and to the input supply in repeated cycles so as to generate a voltage on said reservoir capacitor, the cycles differing between at least two modes so that each mode generates a different voltage on said reservoir capacitor the method including changing from an existing one of said modes to enter a new one of said modes during operation, and operating in at least one transitional mode for a period prior to entering fully said new mode.