Resonant Power Converter Phase Shift Control
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Solution Overview
Problem
Conventional resonant power converters face challenges in efficiently operating over a broad range of input and output voltages and currents due to frequency variations, leading to increased losses, reduced dynamic range, and discontinuities in output current, which complicates the sizing of magnetic elements and filters.
Innovation Solution
A series-parallel resonant power converter structure with two half-bridges and coupled inductors allows for phase opposition and soft switching, enabling efficient operation across all loads without frequency variation, reducing losses and electromagnetic disturbances, and simplifying filter sizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the operating frequency is changed to adapt to input voltage and output load variations, then the resonant converter can operate over a broader range, but magnetic elements and filters experience increased losses due to operation away from their designed frequency
Solution Approach 1:
The patent changes the control parameter from frequency variation to phase shift variation. The resonant frequency is maintained at its optimal value, while the phase difference between the half-bridge inverters is adjusted to adapt to different operating conditions. This resolves the contradiction by maintaining frequency constant (avoiding magnetic losses) while achieving adaptability through phase control.
2Productivity
If the operating frequency is swept to cover a large dynamic range, then the converter can handle varying loads, but the dynamic range itself is reduced and system performance deteriorates
Solution Approach 1:
The patent introduces dynamic control through phase shift adjustment between the two half-bridges. Instead of dynamically changing frequency, the system dynamically adjusts the phase difference to adapt to load variations. This maintains a fixed operating frequency while achieving the needed adaptability, thus preserving dynamic range without sacrificing load adaptation capability.
3Adaptability or versatility
If frequency is changed to vary output load, then the converter can adapt to different operating conditions, but discontinuities in output current occur and secondary current increases
Solution Approach 1:
The patent changes the control variable from frequency to phase shift. By maintaining constant resonant frequency and adjusting only the phase difference between half-bridges, the output current remains continuous and smooth. This eliminates the current discontinuities and secondary current spikes that occur with frequency-based control, while still achieving full output load variation capability.
4Ease of operation
If operating frequency is removed from magnetic elements' operating area, then frequency can be varied for load adaptation, but significant losses occur in inductors and transformer
Solution Approach 1:
The patent segments the control function into two independent parts: frequency selection (fixed at resonant value for magnetic element optimization) and load adaptation (achieved through phase shift). This segmentation allows the magnetic elements to operate always at their optimal frequency while the phase control provides the needed flexibility, resolving the contradiction between frequency flexibility and minimizing magnetic losses.
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 extends the operational range of resonant power converters with high dynamic range, minimizing losses and electromagnetic disturbances, and allowing for efficient soft switching across all loads, including no-load conditions.
Implementation Method 1
If this square-wave signal is at the right frequency, i.e. at the resonant frequency or at a frequency close to the resonant frequency of the Lr, Cr pair, the current can be considered purely sinusoidal
Implementation Method 2
a first inductor between the first half-bridge and the resonant circuit, a second inductor between the second half-bridge and the resonant circuit, and in that the first and second inductors have the same inductance and are coupled in the opposite direction to one another
Data Source
AI summary
A power converter having a parallel resonant circuit, includes an inverter, a resonant circuit, a transformer comprising a primary circuit and a secondary circuit, control means for the inverter, the inverter being connected to the resonant circuit, which is intended to be connected to an output load via the transformer, the power converter wherein the inverter comprises a first half-bridge and a second half-bridge in parallel with the first half-bridge, a first inductor between the first half-bridge and the resonant circuit, a second inductor between the second half-bridge and the resonant circuit, and in that the first and second inductors have the same inductance and are coupled in the opposite direction to one another.