EV Charger Mode Switching for Power Pulsation Absorption
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Solution Overview
Problem
Existing electric vehicle chargers face challenges in reducing the size of high-capacity capacitors required for power pulsation absorption, leading to inefficiencies and increased switching losses due to hard switching and resonance issues in Dual-Active-Bridge (DAB) converters.
Innovation Solution
A charger design that incorporates a rectifier, a DC/DC converter, and a power pulsation absorbing circuit with a controller that switches between discontinuous and continuous current modes based on output power levels, optimizing switching frequency to avoid zero current phases and reduce passive element sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If discontinuous current mode control is used to absorb power pulsation, then power pulsation can be absorbed, but switching loss increases due to hard switching after zero current phase
Solution Approach 1:
The patent dynamically adjusts the switching frequency of the DC/DC converter based on the operating conditions. By making the switching frequency variable rather than fixed, the system can optimize performance across different power levels, reducing switching losses while maintaining power pulsation absorption capability.
Solution Approach 2:
The patent changes the operating parameters of the DC/DC converter, specifically transitioning from discontinuous current mode to continuous current mode by adjusting the switching frequency. This parameter change eliminates the zero current phase and prevents hard switching, thereby reducing switching losses while maintaining effective power pulsation absorption.
2Loss of energy
If continuous current mode control is used to eliminate zero current phase, then switching loss is reduced, but the charger cannot operate when charging small loads
Solution Approach 1:
The patent implements dynamic switching frequency adjustment that adapts to different load conditions. At high power levels, the system operates in continuous current mode with optimized switching frequency to minimize losses. At low power levels, it transitions to discontinuous current mode to maintain stable operation, thereby achieving both efficiency and adaptability across the full operating range.
Solution Approach 2:
The patent segments the operating range into different modes: discontinuous current mode for small loads and continuous current mode for large loads. This segmentation allows the system to optimize for each specific operating condition, ensuring efficient small load operation while maintaining low switching losses at high power levels.
3Loss of energy
If high capacitance capacitor is used for DC link, then power pulsation can be absorbed, but the size of the capacitor increases
Solution Approach 1:
The patent extracts the power pulsation absorption function from the DC link capacitor by introducing a separate active buffer circuit. This allows the DC link capacitor to be significantly reduced in size while the active buffer handles the pulsation absorption, thereby reducing overall component size while maintaining pulsation absorption capability.
Solution Approach 2:
The patent introduces an active buffer circuit as an intermediary between the DC/DC converter and the battery. This intermediary component absorbs power pulsations that would otherwise require a large DC link capacitor, enabling the use of a smaller capacitor while maintaining system performance.
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
Enables a compact and efficient charger that effectively absorbs power pulsation, reducing switching losses and passive element sizes, thereby improving operational efficiency and reducing the size of capacitors and inductors.
Implementation Method 1
a rectifier including two input terminals, a cathode terminal and an anode terminal, wherein the two input terminals are configured for connection to an AC power supply
Implementation Method 2
a DC/DC converter including a first terminal, a second terminal and two output terminals
Implementation Method 3
resonance between the inductor L of the DC/DC converter 120 and parasitic capacitances of the switches S21 to S28
Implementation Method 4
an inductor, a capacitor, a first switch and a second switch
Implementation Method 5
a capacitor and the first switch are connected in series between the first line and the second line with the capacitor being arranged closer to the second line than the first switch
Data Source
AI summary
A charger is configured such that when an output power value of a DC/DC converter is smaller than a first power value, a switch of the DC/DC converter and a first switch of a power pulsation absorbing circuit are controlled according to a discontinuous current mode during one entire period of an AC voltage inputted from a AC power supply; and wherein when the output power value of the DC/DC converter is equal to or greater than a second power value, the switch of the DC/DC converter and the first switch of the power pulsation absorbing circuit are controlled according to a continuous current mode during one entire period of the AC voltage.