EV Power Supply Resonant Inverter Frequency Control
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Solution Overview
Problem
Power supplies for electric vehicles experience unintended increases in power loss due to variations in the power amount supplied to loads, primarily because the actual resonant frequencies of resonant circuits in inverters deviate from the switching frequencies, leading to hard switching and increased energy loss.
Innovation Solution
A power supply system that includes a resonant inverter, a transformer with mutually insulated and magnetically coupled windings, and a control unit that adjusts the switching frequency to maintain a predetermined difference with the resonant frequency, ensuring the inverter performs soft switching and minimizing current flow through switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the resonant inverter operates with fixed capacitor and transformer values, then the resonant frequency is determined, but when power amounts supplied to loads vary, the resonant frequency deviates from switching frequency causing hard switching and increased power loss
Solution Approach 1:
The patent applies dynamics by making the capacitor value adjustable rather than fixed. The capacitor value changing unit dynamically adjusts the capacitance value in the resonant circuit based on the detected power amount supplied to the load, allowing the resonant frequency to adapt and remain substantially equal to the switching frequency across varying power conditions, thereby preventing hard switching and reducing power loss.
2Loss of energy
If the resonant frequency is set higher than switching frequency to enable soft switching, then switching losses are reduced, but when power amounts vary, the resonant frequency may fall below switching frequency causing unintended hard switching
Solution Approach 1:
The patent implements feedback by using a power amount detecting unit to monitor the power supplied to the load and a capacitor value changing unit that adjusts the capacitance based on this feedback. This closed-loop control ensures the resonant frequency adapts to maintain soft switching conditions across varying power amounts, preventing unintended hard switching while maintaining reduced switching losses.
3Device complexity
If fixed capacitor values are used in the resonant circuit, then the circuit design is simple, but the resonant frequency cannot adapt to power variations leading to increased power loss
Solution Approach 1:
The patent applies parameter changes by making the capacitance value variable rather than fixed. The capacitor value changing unit adjusts the capacitance parameter in the resonant circuit based on detected power amounts, allowing the resonant frequency to adapt and remain equal to the switching frequency across different operating conditions, thereby preventing hard switching and reducing power loss without significantly increasing circuit complexity.
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 losses in the resonant inverter, optimizes the switching frequency, and prevents unintended power loss increases by maintaining soft switching even when resonant frequencies deviate, thus enhancing efficiency and reducing cooling system complexity.
Implementation Method 1
generates first alternating-current power from the direct-current power through resonance of the resonant circuit and periodic switching of the switching element
Implementation Method 2
The transformer includes at least a first winding and a second winding mutually electrically insulated and magnetically coupled, is included in a part of the resonant circuit, supplies first alternating-current power generated by the resonant inverter to the first winding, and supplies second alternating-current power after the conversion of the first alternating-current power from the second winding to a load
Data Source
AI summary
A resonant inverter of a power supply for electric vehicle includes a first resonant capacitor and a switching element cutting off a current flowing in a resonant circuit and generates first alternating-current power from direct-current power. The transformer is included in a part of the resonant circuit, supplies the first alternating-current power generated by the resonant inverter to a first winding, and supplies second alternating-current power after conversion of the first alternating-current power to a load from a second winding. A control unit confines a difference between a resonant frequency of the resonant circuit and a switching frequency of the switching element to a predetermined range to cause that a current flowing in switching of the switching element to at least the first winding or the second winding is equal to or less than a predetermined value and to cause the resonant inverter to perform soft switching.