Reduced Capacitor Charge-Pump for Symmetrical Supply Voltages
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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.
Innovation Solution
A charge pump design that generates symmetrical output voltages using a reduced number of flying capacitors, achieving a 1/N ratio of the supply voltage (Vp, Vn = +/- Vdd/N) without feedback control, utilizing feed-forward structures and switching sequences to halve voltages across capacitors, reducing the number of external components and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge pump generates symmetrical positive and negative supply voltages using conventional designs, then the output voltages are symmetrical around ground, but the number of flying capacitors increases, making the circuit complex and increasing external components
Solution Approach 1:
The patent combines multiple flying capacitors into a single shared flying capacitor that is reused across different charge pumping phases. Instead of having separate flying capacitors for each voltage generation path, the same capacitor is sequentially charged and discharged to generate both positive and negative output voltages, thereby reducing component count while maintaining symmetrical output characteristics
Solution Approach 2:
The single flying capacitor performs multiple functions by being reused in different configurations during different phases of the switching cycle. It serves as a charge storage element for both positive and negative voltage generation, and its connections are reconfigured through switching networks to achieve different charge pumping actions, making one component perform the work of multiple capacitors
2Manufacturing precision
If more flying capacitors are used to generate symmetrical voltages, then the voltage ratio control is improved, but the number of external components and device pins increases
Solution Approach 1:
The patent employs dynamic switching networks that reconfigure the connections of the single flying capacitor during different phases of operation. The switching elements dynamically change the circuit topology to achieve precise voltage ratio control (1:1 symmetry) without requiring multiple fixed capacitors, allowing the same component to serve different voltage generation purposes at different times
Solution Approach 2:
The invention changes the operational parameters of the single flying capacitor by adjusting its connection configuration, charging voltage, and discharge timing through controlled switching. This allows precise control over the output voltage ratios and symmetry while maintaining a minimal component count, as the same physical capacitor operates under different electrical conditions during different phases
3Reliability
If conventional charge pump designs are used with multiple flying capacitors, then symmetrical voltages are generated, but power consumption increases due to more components
Solution Approach 1:
By merging multiple flying capacitors into a single shared component, the patent reduces the total capacitance that needs to be charged and discharged during each switching cycle. This reduction in capacitive load directly decreases the energy required for charge pumping operations, lowering power consumption while still achieving the necessary symmetrical voltage generation through intelligent switching control
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 effectively generates energy-efficient symmetrical supply voltages around ground, reducing the number of external components and pin count, achieving power savings and efficiency without linear resistance, suitable for Class-G amplifiers.
Implementation Method 1
a charge pump comprising a network of switches operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage
Data Source
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AI summary
Systems and methods to achieve a charge pump for generating from single supply voltage energy efficient supply voltages that are symmetrical around ground voltage have been disclosed. The charge pump requires two flying capacitors only. The charge pump generates positive and negative supply voltages 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.