DC/DC Converter Voltage Balancing via Intermediate Capacitor
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Solution Overview
Problem
Conventional DC/DC converters face issues with increased ripple current and semiconductor device breakdown due to circuit loss components and variations in switching device ON times, leading to unbalanced voltages and potential overvoltage, which necessitate higher breakdown voltages and increased costs.
Innovation Solution
A DC/DC converter design featuring low-voltage and high-voltage smoothing capacitors, semiconductor circuits with ON/OFF switching functions, and a control apparatus that calculates operation values to control conduction ratios, ensuring balanced voltages and preventing overvoltage breakdown by dynamically adjusting switching operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional DC/DC converter circuit components (switching devices, diodes, reactor) are used with standard breakdown voltages, then the converter can operate, but semiconductor devices may break down due to overvoltage caused by ripple current and voltage imbalance
Solution Approach 1:
The patent introduces an intermediate capacitor connected between the connection point of the second switching device and diode, and the connection point of the diode and first switching device. This intermediate capacitor acts as a voltage balancing element that equalizes the voltages applied to switching devices S1 and S2, preventing overvoltage breakdown. The capacitor mediates the voltage distribution in the circuit, ensuring that no single switching device承受excessive voltage stress.
Solution Approach 2:
The patent changes the voltage parameter distribution in the circuit by introducing the intermediate capacitor. This capacitor modifies the voltage balance equation, ensuring that the sum of voltages across switching devices S1 and S2 equals the sum of voltages across the intermediate capacitor and diode D2. This parameter change prevents voltage imbalance and overvoltage conditions that would otherwise cause semiconductor breakdown.
2Reliability
If higher breakdown voltage semiconductor devices are used to prevent overvoltage breakdown, then device reliability improves, but cost and efficiency deteriorate
Solution Approach 1:
The intermediate capacitor serves as a voltage balancing mediator that allows the use of lower breakdown voltage semiconductor devices. By equalizing the voltage distribution, the capacitor enables standard-rated switching devices to operate safely without requiring expensive high-breakdown-voltage components, thus reducing overall converter cost while maintaining reliability.
3Adaptability or versatility
If the inter-terminal voltage of the charge-discharge capacitor varies from zero to output voltage, then the converter can handle regenerative power, but ripple current in the reactor increases and loss increases
Solution Approach 1:
The intermediate capacitor acts as a voltage reference mediator that stabilizes the operating point of the charge-discharge capacitor. By providing a fixed voltage reference point, the intermediate capacitor helps maintain stable voltage levels during regenerative power operation, reducing voltage variations that would otherwise cause increased ripple current and energy loss in the reactor.
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 effectively prevents semiconductor circuit breakdowns, reduces costs, and maintains efficient voltage control, even with low-breakdown-voltage devices, by dynamically managing switching operations and voltage balancing.
Implementation Method 1
a reactor L connected to a DC power supply
Implementation Method 2
The charge-discharge capacitor C1 is connected between the connection part between the diode D2 and the diode D1, and the connection part between the switching device S2 and the switching device S1
Data Source
AI summary
In a DC/DC converter, a first operation section calculates a first operation value, based on a difference voltage between an instruction value for a high-voltage-side voltage and a detected value of a high-voltage-side voltage, a second operation section calculates a second operation value, based on a difference voltage between a voltage instruction value for a charge-discharge capacitor and a voltage detected value of the charge-discharge capacitor, and a switching control section obtains a conduction ratio, based on the first operation value and the second operation value, and controls, based on the conduction ratio, switching operations of first to fourth semiconductor circuits, thereby controlling the high-voltage-side voltage, and the voltage of the charge-discharge capacitor.