Bidirectional DC/DC Power Supply Layout for Lower Switching Loss
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Solution Overview
Problem
Existing power supply systems for electric vehicles, such as those using multi-stage DC chopper circuits, face increased switching loss and steady loss due to the need for higher withstand voltage switching elements, which also raises costs and iron loss.
Innovation Solution
A power supply system that includes a DC power supply, a variable voltage power supply with an isolated bidirectional DC/DC converter, and a switching circuit with arm switches, where the variable voltage is stacked on the DC voltage, reducing the need for multiple stages and thus minimizing switching and steady losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a multi-stage DC chopper circuit is used to output multi-stage DC voltage, then the voltage output capability is improved, but the number of switching elements increases and switching loss increases
Solution Approach 1:
The patent divides the voltage output function into two independent parts: a DC voltage output unit that provides stable DC voltage, and an AC voltage output unit that generates AC voltage by switching. This segmentation allows each unit to be optimized independently, reducing the need for multiple high-voltage switching stages and thereby reducing switching loss while maintaining multi-stage voltage output capability.
Solution Approach 2:
The patent combines the DC voltage output function and AC voltage output function into a single power supply system. The DC voltage from the DC voltage output unit is combined with the AC voltage from the AC voltage output unit to provide both DC and AC power outputs, eliminating the need for separate multi-stage DC chopper circuits for each output type and reducing overall switching loss.
2Reliability
If switching elements with higher withstand voltage are used to handle surge voltage, then the reliability is improved, but the on-resistance increases and steady loss increases
Solution Approach 1:
The patent introduces a surge voltage countermeasure unit that actively suppresses surge voltage before it can damage switching elements. By detecting and counteracting surge voltage in advance, the system can use switching elements with lower withstand voltage ratings, thereby reducing on-resistance and steady loss while maintaining reliability.
3Power
If the number of switching elements is increased to achieve multi-stage DC voltage output, then the voltage output capability is improved, but the device complexity increases
Solution Approach 1:
The patent segments the power supply system into distinct functional units: a DC voltage output unit with fewer switching elements, and an AC voltage output unit that generates AC voltage. This segmentation achieves multi-stage voltage output capability while keeping the number of switching elements in each unit manageable, thereby reducing overall device complexity.
Solution Approach 2:
The DC voltage output unit serves multiple functions: it provides DC voltage directly to DC loads and also supplies DC voltage to the AC voltage output unit for conversion to AC. This multi-functionality eliminates the need for separate power conversion stages and reduces the total number of switching elements required.
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 reduces switching loss, steady loss, and costs by eliminating the need for high withstand voltage switching elements and minimizing high-frequency voltage components applied to the load.
Implementation Method 1
a first variable voltage power supply (for example, a variable voltage power supply 7, 7A, 7B, or 7C to be described below) that outputs power of a variable voltage
Data Source
AI summary
A power supply system 1 includes: a DC power supply 30; a variable voltage power supply 7 serving as an isolated bidirectional DC/DC converter that outputs power of a variable voltage E2 from a pair of secondary-side input/output terminals 72p and 72n; a positive electrode power line 21 and a negative electrode power line 22 that are connected to both electrodes of the DC power supply 30; a switching circuit5 including a plurality of arm switching elements 51, 52, 53, and 54 that connect the power lines 21 and 22 and a load 4; a backflow prevention switching element 34 that is provided on the positive electrode power line 21 between the pair of secondary-side input/output terminals 72p and 72n; a power supply driver 6 that operates the variable voltage power supply 7 and the backflow prevention switching element 34; and a switching circuit driver 8.