DC/DC Converter Precharging Circuit for Low-Loss Grid Feedback
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Solution Overview
Problem
Existing DC/DC converters and grid feedback units face challenges in being manufactured inexpensively and minimizing power losses, particularly in three-phase grid applications.
Innovation Solution
A DC/DC converter design featuring parallel-connected switching cells with a precharging circuit that includes a resistor and a driveable switching means, allowing for controlled precharging and reduced switch-on currents, coupled with an inverter for efficient energy feedback into a three-phase grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC/DC converter is designed with parallel switching cells for three-phase grid applications, then power conversion capability is improved, but manufacturing cost and power losses increase
Solution Approach 1:
The patent combines multiple switching cells (first and second switching cells with capacitors, diodes, and semiconductor switching means) into a single DC/DC converter architecture that processes three-phase grid power. By merging these cells to work in parallel with shared components and a unified control unit, the design achieves improved power conversion capability while controlling manufacturing costs through component consolidation and standardized construction.
2Device complexity
If switching cells are activated directly without precharging, then device complexity is reduced, but power losses and switch-on currents increase
Solution Approach 1:
The patent implements a precharging circuit with a precharging resistor and driveable switching means that activates before the main switching cells. This preliminary action precharges the capacitors in the switching cells to the appropriate voltage level before full power operation begins, thereby reducing switch-on currents and minimizing power losses during activation without significantly increasing overall device complexity.
3Speed
If capacitor switching occurs without precharging, then switching speed is improved, but harmful switch-on currents are generated
Solution Approach 1:
The patent introduces a precharging circuit as an intermediary between the power source and the main switching cells. This intermediary circuit, containing a precharging resistor and control switching means, prepares the capacitors by charging them to the required voltage level before the main switching operation. This mediation enables fast switching while preventing harmful switch-on currents by ensuring capacitors are properly precharged, thus resolving the contradiction between switching speed and harmful current generation.
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
This design achieves cost-effectiveness and low power losses, enabling production on an uncooled circuit board with reduced space requirements and minimal additional impedance, thus addressing the manufacturing and efficiency issues.
Implementation Method 1
The precharging circuit has a precharging resistor and a driveable switching means, for example in the form of a relay, wherein the precharging resistor and the driveable switching means are connected in parallel.
Implementation Method 2
The capacitor of the first switching cell and the capacitor of the second switching cell may together form a buffer capacitor to be precharged.
Data Source
AI summary
A DC/DC converter includes: a first connection pole and a second connection pole, wherein a first DC voltage is applied between the first connection pole and the second connection pole; a third connection pole and a fourth connection pole, wherein a second DC voltage is applied between the third connection pole and the fourth connection pole; a first commutation cell, wherein the first commutation cell has a capacitor, a diode and a semiconductor switch; a second commutation cell, wherein the second commutation cell has a capacitor, a diode and a semiconductor switch; and a precharging circuit for precharging the capacitor of the first commutation cell and the capacitor of the second commutation cell. The precharging circuit has a precharging resistor and an actuable switching device. The precharging resistor and the actuable switching device are connected in parallel. The capacitor of the first commutation cell, the precharging circuit and the capacitor of the second commutation cell are looped in series between the first connection pole and the second connection pole.