Cascade Switched Capacitor Converter With Zero-Voltage Switching
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Solution Overview
Problem
Conventional inductive DC-DC converters suffer from inefficient conversion efficiency due to large switching loss and inductive loss, which is inadequate for high power consumption applications like 5G communication and mobile phone fast charging.
Innovation Solution
A switched capacitor converter with an auxiliary circuit is proposed, which enables zero voltage switching (ZVS) for all primary power transistors, reducing switching loss and extending the converter topology to a 2N:1 switched capacitor converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional inductive DC-DC converters are used, then voltage conversion can be achieved, but conversion efficiency is low due to large switching loss and inductive loss
Solution Approach 1:
The patent replaces the inductive energy storage mechanism with a capacitive energy storage mechanism. The switched capacitor converter uses capacitors to store and transfer energy, eliminating the need for inductors and their associated switching losses. This substitution fundamentally changes the energy conversion approach from inductive to capacitive, achieving higher efficiency in high power consumption applications.
Solution Approach 2:
The patent changes the operating parameters of the power transistors by implementing zero voltage switching (ZVS) through the auxiliary circuit. By ensuring that power transistors switch when the voltage across them is zero, the switching loss is dramatically reduced. This parameter change (voltage at switching moment = 0) directly addresses the energy loss problem.
2Productivity
If cascade switched capacitor converters are used, then conversion efficiency is improved, but switching loss occurs due to parasitic capacitors Cds and Cgd when power transistors are turned on
Solution Approach 1:
The patent introduces an auxiliary circuit as an intermediary between the power transistors and the rest of the circuit. This auxiliary circuit includes additional capacitors and switches that work together to charge the parasitic capacitors (Cds and Cgd) of the power transistors before they turn on. By providing this intermediate charging path, the main power transistors can switch at zero voltage, eliminating the switching loss caused by parasitic capacitors.
Solution Approach 2:
The auxiliary circuit performs preliminary action by pre-charging the parasitic capacitors of the power transistors before the main switching event occurs. During the dead time between switching events, the auxiliary circuit charges the Cds and Cgd capacitors, so that when the power transistors are turned on, there is no voltage difference across them, and thus no switching loss is incurred.
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 significantly reduces switching loss and improves conversion efficiency, making it suitable for high power applications while maintaining low package size and cost.
Implementation Method 1
the auxiliary circuit is configured to transfer a charge or electric charges on one of the first branch and the second branch to another of the first branch and the second branch during a dead time when the primary power transistors are turned off
Data Source
AI summary
A switched capacitor converter includes an auxiliary circuit, a first branch and a second branch, the auxiliary circuit is connected between the first branch and the second branch, all power transistors of the first branch and the second branch are primary power transistors, and the auxiliary circuit transfers a charge or electric charges on one of the first branch and the second branch to another of the first branch and the second branch during a dead time when the primary power transistors are turned off, so as to the primary power transistors turn on at zero voltage and reduce a switching loss.