Charge Pump Using Two Flying Capacitors for Symmetrical Voltage Generation
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Solution Overview
Problem
Existing charge pumps require a minimum number of flying capacitors to generate symmetrical positive and negative supply voltages, which are expensive and increase the number of external components and device pins, making them inefficient for energy-efficient audio systems.
Innovation Solution
A charge pump design using two flying capacitors and a digital controller to generate symmetrical output voltages with a 1/N ratio of the supply voltage, reducing the number of external components and pin count by operating in multiple phases to achieve ratios such as +/- Vdd/5 and +/- Vdd/6, while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional charge pump designs are used to generate symmetrical positive and negative supply voltages, then the required voltage ratios can be achieved, but the number of flying capacitors increases, leading to more external components and higher cost
Solution Approach 1:
The charge pump circuit is designed to generate multiple voltage ratios (1/2, 1/3, 1/4, 1/5, 1/6) using the same two flying capacitors through different switching sequences, eliminating the need for separate capacitor networks for each ratio and significantly reducing external component requirements
Solution Approach 2:
The circuit employs a digitally controllable switching network that dynamically reconfigures the charge pump operation to achieve different voltage division ratios on-demand, allowing the system to adapt between 1/2, 1/3, 1/4, 1/5, and 1/6 ratios without hardware changes
2Measurement precision
If more flying capacitors are used to achieve precise voltage ratios, then the voltage generation accuracy improves, but the power consumption and circuit complexity increase
Solution Approach 1:
The voltage generation process is divided into distinct phases (charge phase, transfer phase, discharge phase) controlled by digital switching sequences, allowing precise voltage ratio control through temporal segmentation rather than spatial multiplication of components
Solution Approach 2:
The circuit achieves different voltage ratios by changing the switching timing and sequence parameters rather than changing the physical capacitor values, enabling precise 1/2, 1/3, 1/4, 1/5, and 1/6 ratios through digital control of the same hardware
3Ease of manufacture
If a minimum number of flying capacitors is used to reduce external components, then the device pin count and cost decrease, but the ability to generate multiple voltage ratios is limited
Solution Approach 1:
The charge pump circuit is designed to generate multiple voltage ratios (1/2, 1/3, 1/4, 1/5, 1/6) using the same two flying capacitors through different switching sequences, eliminating the need for separate capacitor networks for each ratio and significantly reducing external component requirements
Solution Approach 2:
The circuit employs a digitally controllable switching network that dynamically reconfigures the charge pump operation to achieve different voltage division ratios on-demand, allowing the system to adapt between 1/2, 1/3, 1/4, 1/5, and 1/6 ratios without hardware changes
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 solution reduces the number of flying capacitors required, decreases power dissipation, and enhances efficiency by generating symmetrical voltages with fewer external components, thus improving power management in audio systems like Class-G amplifiers.
Implementation Method 1
a first flying capacitor and a second flying capacitor in a charge pump
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Systems and methods to achieve a charge pump for generating from single supply voltage (Vdd) energy efficient supply voltages having a value of ± 1/6 Vdd, ± 1/5 Vdd, ± 1/4 Vdd, ± 1/3 Vdd, ± 1/2 Vdd or ± 1 Vdd that are symmetrical around ground voltage have been disclosed. The charge pump requires two flying capacitors (C1,C2) only. The charge pump generates positive and negative supply voltages (Vp,Vn) following a 1/N ratio of Vdd voltage, i.e.+-Vdd/N, and can be generalized to generate +/-Vdd/2N voltages. This is especially useful for supplying class-G amplifiers with a voltage or power, which is just enough e.g. for an audio signal to be correctly generated at the output of the amplifier.