Dual Mode Charge Pump Circuit for Efficient Voltage Generation
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Solution Overview
Problem
Existing dual rail charge pump circuits are inefficient when used to power circuitry that amplifies signals with amplitudes much smaller than the power supply, as they generate output voltages with a rail-to-rail magnitude greater than the input voltage, leading to significant power wastage as heat.
Innovation Solution
A dual mode charge pump circuit that operates in two modes: Mode 1 generates output voltages of half the input voltage magnitude, and Mode 2 produces dual rail outputs of +/-VDD, using a single flying capacitor and two reservoir capacitors, allowing for reduced bipolar supply generation and efficient power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dual rail charge pump generates output voltages of +/-VDD (full rail-to-rail magnitude), then the voltage range is sufficient for amplifying signals, but power efficiency deteriorates when the signal amplitude is much smaller than the power supply voltage
Solution Approach 1:
The charge pump circuit dynamically switches between two operating modes based on the required output voltage. In Mode 1, it generates full +/-VDD output for applications requiring maximum voltage range. In Mode 2, it generates reduced +/-VDD/2 output for applications with smaller signal amplitudes. This dynamic adaptability resolves the contradiction by matching the output voltage to the actual load requirements, minimizing power waste while maintaining versatility.
Solution Approach 2:
The invention changes the output voltage parameter by introducing a selectable operating mode that divides the output voltage by two. The control circuit receives a mode selection signal that switches the charge pump between generating full rail-to-rail voltages (+/-VDD) and reduced voltages (+/-VDD/2). This parameter change allows the system to adapt to different power requirements, improving efficiency when full voltage range is not needed.
2Adaptability or versatility
If a charge pump uses multiple capacitors to generate dual rail output voltages, then the voltage generation capability is improved, but the device complexity increases
Solution Approach 1:
The single flying capacitor in the invention performs multiple functions that would traditionally require separate components. It serves as both the charge transfer element and the basis for generating both positive and negative output voltages. By making this one capacitor multi-functional through clever switching arrangements, the circuit achieves dual rail voltage generation without the complexity of multiple dedicated capacitors, resolving the contradiction between versatility and device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dual mode charge pump circuit efficiently generates reduced bipolar supply voltages using a single flying capacitor, reducing power wastage and eliminating the need for additional capacitors, thereby improving efficiency and reducing component count.
Implementation Method 1
The charge pump includes a capacitor, typically known as a 'flying capacitor', for transferring charge to one or more output capacitors, which will be referred to as 'reservoir capacitors'.
Data Source
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Figure 4b
AI summary
Disclosed is a dual mode charge-pump circuit and associated method and apparatuses for providing a plurality of output voltages (Vout+, Vout-), using a single flying capacitor (Cf), the circuit comprising, a network of switches (410) that is operable in a number of different states and a controller (420) for operating said switches in a sequence of said states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage (+VDD) and centred on the voltage at a common terminal (N11), in a first mode and positive and negative output voltages each up to substantially said input voltage in a second mode.