Full-Bridge Inverter Resonant Mode Control for Power Efficiency
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Solution Overview
Problem
Existing power conversion devices with full-bridge inverters and rectifier circuits face inefficiencies due to circulating currents, which increase conduction loss and limit power transmission, and the addition of capacitors to address these issues raises costs and introduces additional losses.
Innovation Solution
The power conversion device switches between single-leg and dual-leg resonant-mode operations based on load conditions, eliminating circulating currents and enhancing power transmission without additional components or transformer turns ratio, utilizing soft switching techniques with capacitors and reactors for efficient power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circulation period is set to enable soft switching, then switching elements achieve zero-voltage and zero-current switching turn-on, but power transmission period is reduced limiting transmission power
Solution Approach 1:
The patent makes the circulation period dynamic, adjusting it based on load conditions. When load demand is high, the circulation period is reduced to maximize power transmission time. When load demand is low, the circulation period is extended to maintain soft switching operation. This dynamic approach allows the system to maintain reliability through soft switching while adapting power transmission capacity to actual needs.
Solution Approach 2:
The patent applies partial action by not maintaining a full circulation period at all times. Instead, the circulation period is applied partially - extended only when necessary to enable soft switching under light load conditions, and reduced or eliminated when full power transmission is needed under heavy load conditions. This partial application of circulation period optimizes both soft switching and power transmission.
2Power
If transformer turns ratio is increased to transmit power in narrow transmission period, then power transmission capability is improved, but voltage across secondary-side diodes increases requiring higher withstand voltage elements
Solution Approach 1:
Rather than using a fixed high turns ratio, the patent dynamically adjusts the effective transmission period and circulation period based on load conditions. This dynamic time-based control allows the system to achieve high power transmission capability when needed without permanently increasing the transformer turns ratio, thereby avoiding the need for high-withstand-voltage diodes while maintaining the capability when required.
Solution Approach 2:
The patent changes the operational parameters (circulation period and power transmission period) rather than changing the physical transformer turns ratio. By varying the timing parameters dynamically, the system achieves high power transmission capability temporarily when needed, without the permanent structural change that would require higher-voltage-rated components.
3Power
If additional capacitor is added to advance current and increase voltage-current time product, then transmission power from transformer is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing capacitor in the circuit serve multiple functions. By dynamically adjusting the circulation period, the existing capacitor's voltage-current time product is optimized to provide both power factor correction and power transmission enhancement without requiring additional capacitors. The circuit serves itself by utilizing existing components more effectively through intelligent control.
Solution Approach 2:
The patent makes the existing capacitor multi-functional by optimizing its utilization through dynamic circulation period control. The same capacitor that provides basic filtering also provides power factor correction and enhances transmission power when the circulation period is properly adjusted, eliminating the need for additional dedicated power factor correction capacitors.
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 increases power transmission efficiency by eliminating circulating currents and reducing conduction losses, allowing for higher power delivery without additional parts or increased transformer turns ratio, while maintaining a compact and cost-effective design.
Implementation Method 1
the two switching elements constituting the second leg operate the soft switching with ZVS turn-on and ZVS turn-off utilizing a resonance phenomenon caused by the reactor and the capacitor connected with each switching element
Implementation Method 2
with zero-voltage switching (ZVS) turn-off utilizing the tangent of the rising voltage of the capacitor connected in parallel with each switching element
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A full-bridge inverter (2) is configured with a parallel connection of a first leg (3) and a second leg (4) each having two switching elements (S1, S2, S3, S4) connected in series, and controlled in a dual-leg resonant mode in which a positive-side switching element (S1) of the first leg (3) and a negative-side switching element (S4) of the second leg (4) are turned on/off at the same time and a negative-side switching element (S2) of the first leg (3) and a positive-side switching element (S3) of the second leg (4) are turned on/off at the same time, and controlled in a single-leg resonant mode in which the positive-side switching element (S1) of the first leg (3) and the negative-side switching element (S4) of the second leg (4) are turned on/off shiftedly in time by a phase shift amount and the negative-side switching element (S2) of the first leg (3) and the positive-side switching element (S3) of the second leg (4) are turned on/off shiftedly in time by the phase shift amount.