DC/DC Power Conversion Device Voltage Suppression
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Solution Overview
Problem
Conventional bi-directional choppers face challenges in maintaining efficient and compact power conversion due to increased voltage applied to switching elements, which requires high withstand voltage, leading to increased circuit scale and cost, and limits the use of low-loss, high-speed switching elements.
Innovation Solution
A power conversion device configuration with series-connected switching elements and reactors between midpoints and terminals, where switching control is managed using specific duty command values and high-frequency current components to maintain voltage within a predetermined range, allowing the use of low withstand voltage switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power source voltage increases, then the power conversion capability is improved, but the voltage applied to the switching elements increases requiring higher withstand voltage
Solution Approach 1:
The patent divides the switching element into multiple series-connected switching elements (first switching element and second switching element). This segmentation allows the total voltage to be distributed across multiple components, so each individual switching element only needs to withstand a fraction of the total voltage, enabling the use of lower-voltage-rated switching elements even when the power source voltage is high.
Solution Approach 2:
The patent introduces a capacitor as an intermediary component connected in parallel with the second switching element. This capacitor acts as a voltage buffer that stabilizes the voltage across the second switching element, preventing voltage spikes and ensuring that the voltage distribution remains balanced. This allows the switching elements to operate reliably at lower voltage stress while still handling high power source voltages.
2Strength
If switching elements with high withstand voltage are used, then the voltage handling capability is improved, but the device becomes less efficient and larger in size
Solution Approach 1:
By segmenting the voltage handling task across multiple switching elements, each element can be optimized for lower voltage operation. Low-voltage-rated switching elements have lower on-resistance and faster switching speeds, resulting in reduced conduction losses and switching losses compared to using a single high-voltage-rated switching element.
Solution Approach 2:
The patent changes the voltage parameter distribution across the switching elements through series connection and capacitor assistance. This parameter transformation allows each switching element to operate in its optimal voltage range, achieving better efficiency characteristics while maintaining the required overall voltage handling capability.
3Strength
If the number of switching elements is increased, then the voltage applied to each switching element is reduced, but the circuit scale and cost increase
Solution Approach 1:
The patent applies segmentation by using exactly two switching elements in series, which is the minimum number needed to effectively divide the voltage stress. This segmented approach achieves voltage distribution benefits while minimizing the increase in circuit complexity compared to using a single switching element.
Solution Approach 2:
The capacitor connected in parallel with the second switching element serves multiple functions: it acts as a voltage buffer, balances voltage distribution, and enables the use of lower-voltage-rated switching elements. This multi-functional component helps achieve voltage distribution benefits without proportionally increasing circuit scale.
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 configuration suppresses voltage applied to switching elements, enabling the use of low withstand voltage elements for a highly efficient and compact power conversion device.
Implementation Method 1
a first reactor (61) connected between a midpoint of the first switching element (41) and the second switching element (42) and a terminal of the third switching element (43) not connected to the fourth switching element (44)
Data Source
AI summary
Voltage applied to switching elements of a power conversion device is suppressed to be within a predetermined range. A power conversion device (1) includes a leg (31) in which switching elements (41, 42) are connected in series, a leg (32) in which switching elements (43, 44) are connected in series, a reactor (61) connected between the midpoint of the switching elements (41, 42) and the switching-element (43) end not connected to the switching element (44), a reactor (62) connected between the midpoint of the switching elements (43, 44) and the switching-element (42) end not connected to the switching element (41), and a DC power source (10) connected between the switching-element (41) end not connected to the reactor (61) and the terminal of the switching element (44) not connected to the reactor (62). Loads can be connected in parallel to the legs (31, 32).