Flying Capacitor Primary Circuit for High-Voltage DC/DC Switching
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Solution Overview
Problem
High power DC/DC converters require large and inefficient switches due to high voltage ratings, leading to bulky designs and potential transformer saturation issues.
Innovation Solution
A primary side circuit with four switches and two capacitors in series, combined with a flying capacitor and transformer coil configuration, allows for reduced switch voltage ratings, enabling smaller switches and faster switching, while maintaining high voltage application and reducing transformer saturation risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high voltage ratings are used in switches for high power DC/DC converters, then the converter can handle high voltage applications, but the switches become large and inefficient leading to bulky designs
Solution Approach 1:
The primary side circuit is divided into four switches connected in series between two voltage application nodes, with two capacitors coupled in series. This segmentation allows the voltage to be distributed across multiple switches rather than requiring a single high-voltage switch, enabling the use of smaller, lower-voltage-rated switches while maintaining high voltage handling capability.
Solution Approach 2:
The patent introduces a flying capacitor connected between circuit nodes in the switch series, and a primary side transformer coil connected between additional circuit nodes. This adds a temporal/dimensional dimension to voltage distribution by utilizing capacitive energy storage and magnetic coupling to achieve voltage multiplication and distribution, allowing smaller switches to handle high voltage through coordinated switching sequences.
2Temperature
If high voltage ratings are used in switches, then high voltage applications are enabled, but switching speed decreases due to larger switch capacitance
Solution Approach 1:
By dividing the high voltage application across four series-connected switches, each switch only needs to block a fraction of the total voltage. This reduces the output capacitance of each individual switch, enabling faster switching speeds while maintaining the overall high voltage capability of the converter through the series configuration and flying capacitor assistance.
Solution Approach 2:
The patent changes the voltage parameter distribution across switches by introducing capacitive and inductive elements. The flying capacitor and transformer coil enable voltage multiplication and redistribution, allowing each switch to operate at lower voltage stress with corresponding reduced capacitance and improved switching speed, while the overall system maintains high voltage conversion capability.
3Power
If high power switches are used, then high power conversion is achieved, but transformer saturation issues arise
Solution Approach 1:
The primary side circuit segments the power conversion function across four switches and two capacitors, with the transformer coil coupled to intermediate circuit nodes. This segmentation allows better control of current waveforms and voltage stress distribution, preventing excessive current spikes that could cause transformer saturation while maintaining high power conversion capability through coordinated operation of all components.
Solution Approach 2:
The flying capacitor acts as an intermediary energy storage element between the switches and transformer, and the transformer coil serves as an intermediary for magnetic coupling. These intermediary elements smooth current waveforms, distribute voltage stress, and control energy transfer timing, preventing direct high-current stress on the transformer that would lead to saturation while enabling high power conversion.
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 results in a more compact and efficient DC/DC converter with improved power density and faster switching capabilities, minimizing transformer saturation and power losses.
Implementation Method 1
the primary side is inductively coupled to the secondary side using a transformer
Data Source
AI summary
A voltage converter circuit including a primary side circuit including four transistors connected in series between two voltage application nodes, and two capacitors coupled in series between the two voltage application nodes. A flying capacitor is connected between first circuit node and a second circuit node, where the first circuit node is between the first and second transistors in the transistor series, and the second circuit node is between the third and fourth transistors in the transistor series. A primary side transformer is connected between a third circuit node and a fourth circuit node, where the third circuit node is between the second and third transistors in the transistor series, and the fourth circuit node is between the first and second capacitors in the capacitor series.