Charge Pump Circuit Dividing Input Voltage Span
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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 produce output voltages with a rail-to-rail magnitude twice the input voltage, resulting in significant power wastage as heat.
Innovation Solution
A charge pump circuit with a network of switches and a controller that operates in multiple states to divide the input voltage between a flying capacitor and a reservoir capacitor in series, and then applies the flying capacitor's portion of the divided voltage across another reservoir capacitor, generating positive and negative output voltages that span approximately the input voltage, centered on a common terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a known dual rail charge pump produces output voltage with magnitude twice the input voltage (VDD), then the output voltage span is increased, but power efficiency deteriorates due to significant power wastage as heat
Solution Approach 1:
The charge pump dynamically switches between different operational states (first state and second state) to control voltage distribution. In the first state, the input voltage is divided between the flying capacitor and first reservoir capacitor in series. In the second state, the flying capacitor's portion of the divided voltage is applied across the second reservoir capacitor. This dynamic switching enables the output voltage span to be adjusted to approximately equal the input voltage, optimizing power efficiency while maintaining adequate voltage span for signal amplification.
2Loss of energy
If the output voltage span is reduced to match the signal amplitude, then power efficiency is improved, but the output voltage magnitude is reduced
Solution Approach 1:
The invention changes the operational parameters of the charge pump by implementing a multi-state switching scheme that controls the distribution of input voltage across the capacitors. By adjusting the switching sequence and timing, the output voltage magnitude is optimized to approximately equal the input voltage (rather than twice the input voltage), while maintaining sufficient span to drive the amplifier circuitry efficiently, thus improving power efficiency without sacrificing necessary voltage magnitude.
3Measurement precision
If multiple flying capacitors are used to achieve precise voltage division, then voltage control precision is improved, but device complexity increases
Solution Approach 1:
The invention segments the voltage division function into two stages using a single flying capacitor: first, dividing the input voltage between the flying capacitor and first reservoir capacitor in series; second, applying the flying capacitor's portion across the second reservoir capacitor. This segmentation achieves precise voltage control with only one flying capacitor, avoiding the need for multiple capacitors and reducing overall device complexity while maintaining adequate voltage control precision for the application.
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
This approach reduces power wastage by generating output voltages that are half the input voltage, improving efficiency and allowing for the use of a single flying capacitor, which can be integrated on-chip, reducing component count and size.
Implementation Method 1
a single flying capacitor, for transferring packets of charge repeatedly from said input supply to said reservoir capacitors
Data Source
Figure 1~2c
Figure 3~4a
Figure 4b~10
AI summary
A charge pump circuit and associated method and apparatuses for providing a plurality of output voltages using a single flying capacitor is disclosed, 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 and centred on the voltage at the common terminal.