Switched-Capacitor Charging Circuit for Efficient 2:1 Conversion
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Solution Overview
Problem
Switch capacitor charging circuits face efficiency issues when switching between voltage conversion ratios of 4:1 and 2:1, particularly at the 2:1 ratio where only power transistors near the high voltage side operate, leading to reduced efficiency.
Innovation Solution
The proposed switch capacitor charging circuit includes N−1 switch capacitor units configured in series and parallel, allowing for operation in both 4:1 and 2:1 voltage conversion modes. In the 2:1 mode, the first switch capacitor unit participates, or the (N−1)-th and first units connect in parallel, optimizing power transistor operation to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only power transistors near the high voltage side operate in 2:1 voltage conversion mode, then the circuit structure is simplified, but charging efficiency deteriorates due to increased switching losses
Solution Approach 1:
The charging circuit is divided into multiple switch capacitor units (first, second, third, and fourth units) with distinct functions. The first and second units handle 4:1 voltage conversion, while the third and fourth units handle 2:1 voltage conversion. This segmentation allows selective operation of different units based on the required voltage conversion ratio, enabling both high-voltage-side and low-voltage-side power transistors to operate efficiently in 2:1 mode without increasing overall circuit complexity.
2Loss of energy
If switch capacitor units are configured for both 4:1 and 2:1 voltage conversion modes, then charging efficiency in 2:1 mode improves, but device complexity increases
Solution Approach 1:
Each switch capacitor unit is designed with multi-functionality to operate in both 4:1 and 2:1 voltage conversion modes. The units share common circuit elements such as flying capacitors, power transistors, and control logic. This universal design allows the system to achieve improved charging efficiency in 2:1 mode through proper unit configuration while avoiding the need for completely separate circuit structures for each mode.
Data Source
AI summary
A switch capacitor charging circuit can include: a first port coupled to a first voltage source; a second port coupled to a first battery; a switch capacitor circuit including (N−1) switch capacitor units coupled between the first port and the second port, and being configured to charge the first battery, where each of the switch capacitor units includes a flying capacitor; at least one first power transistor, where each first power transistor includes a first terminal coupled to the first port, and a second terminal coupled to one terminal of a flying capacitor in a different switch capacitor unit; and where the first switch capacitor unit is coupled to the second port, and an (N−1)-th switch capacitor unit is configured to be coupled to the first port, where N is a positive integer greater than or equal to 3.