Resonant Converter Phase Shift Modulation for Switching Loss Reduction
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Solution Overview
Problem
Resonant converters with inverter circuits face high switching losses due to sub-resonant and super-resonant actuation modes, especially when dealing with varying input voltages and output powers, leading to inefficient power transmission and increased conductance losses.
Innovation Solution
The method involves simultaneously regulating the actuation frequency and duty factor of the inverter voltage in a coordinated manner, using phase shift modulation to achieve zero-voltage switching across a wide operating range, reducing switching losses and eliminating the need for complex snubber networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sub-resonant actuation is used to achieve low output powers, then the actuation frequency becomes very low (reaching audible range), but this causes high switching losses when switching on the semiconductor switches
Solution Approach 1:
The patent applies dynamics by making the actuation frequency variable rather than fixed. The frequency is dynamically adjusted based on the desired output power level, allowing the system to operate at optimal frequencies for different power requirements while maintaining zero-voltage switching conditions to minimize losses
Solution Approach 2:
The patent changes the operating parameter (actuation frequency) to resolve the contradiction. By carefully selecting and adjusting the actuation frequency to be slightly below the resonant frequency, the system achieves zero-voltage switching across a wide power range, eliminating the need for snubber networks and reducing switching losses
2Speed
If super-resonant actuation is used to increase actuation frequency above audible range, then power transmission is maximized, but the reverse-connected diodes cannot be commutated off, causing high switching losses
Solution Approach 1:
The patent inverts the conventional approach by operating slightly below rather than above the resonant frequency. This inversion of the operating point allows the current to naturally reach zero before the switch turns on, enabling zero-voltage switching and allowing the reverse-connected diodes to be properly commutated off, thereby reducing switching losses
3Adaptability or versatility
If the resonant frequency is set below the maximum output voltage for minimum input voltage, then the actuation frequency range can be extended, but this results in inconvenient ratio for reactive and active power away from the operating point, producing excessively high conductance losses
Solution Approach 1:
The patent employs feedback control to maintain optimal operating conditions across varying input voltages and power levels. By continuously monitoring the operating point and adjusting the actuation frequency accordingly, the system maintains the resonant circuit operation near the optimal point, preventing excessive conductance losses while preserving adaptability
4Loss of energy
If additional passive or active snubber networks are used to reduce switching losses in sub-resonant actuation, then zero-current switching is achieved, but this increases device complexity
Solution Approach 1:
The patent extracts and eliminates the need for complex snubber networks by operating the resonant converter in a specific mode (slightly sub-resonant) where the resonant circuit naturally provides zero-voltage switching conditions. This removes the harmful element (complex snubber networks) while maintaining the beneficial effect (reduced switching losses)
Solution Approach 2:
The resonant circuit itself provides the necessary soft-switching conditions without requiring external snubber networks. The natural resonant behavior of the circuit is harnessed to achieve zero-voltage switching, making the system self-sufficient and eliminating the need for additional 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 approach allows for low switching losses and efficient operation across a wide range of input and output voltages, reducing reactive current and frequency swings, and enabling zero-voltage no-load switching without complex snubber networks, thus improving the efficiency and reliability of resonant converters.
Implementation Method 1
the voltage transformation and the power transmission close to the resonant frequency are at a maximum
Data Source
AI summary
A method for operating a resonant converter having an inverter circuit, the inverter circuit having a plurality of switches, includes: switching each of the switches of the plurality of switches at an actuation frequency and with a phase angle offset relative to one another, such that a voltage of an output of the inverter circuit has a duty factor; and determining the actuation frequency and the duty factor for a prescribable operating point and with a prescribable phase reserve of the resonant converter. A resonant converter and an x-ray generator having a resonant converter are described.