Resonant Rectifier Using MOS Transistors for Power Efficiency
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Solution Overview
Problem
In resonant rectifying circuits, inductance leakage in transformers leads to suboptimal power transfer efficiency due to non-resonant operation and high internal resistance of diodes, causing increased power consumption and potential load damage from magnetic flux leakage.
Innovation Solution
The use of MOS transistors instead of diodes in the secondary side and the strategic placement of inductors in the primary side to create a resonant circuit, along with a control method that includes pulse width modulation and frequency modulation to manage power transfer, effectively disconnecting the circuit loop and minimizing magnetic flux leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If diodes are used in the rectifying circuit of the secondary coil, then the circuit structure is simple, but the internal resistance of diodes causes high power consumption and low converting efficiency
Solution Approach 1:
The patent changes the key parameter from diode to MOS tube in the rectifying circuit. MOS tubes have much lower on-resistance compared to diodes, which dramatically reduces conduction losses and power consumption while maintaining circuit simplicity. The control mode is also changed from traditional PWM to resonant frequency control, optimizing the operating parameters for minimal energy loss.
Solution Approach 2:
The patent converts the harmful effect of magnetic flux leakage and inductance leakage into beneficial resonance effects. By operating at the resonant frequency of the LC circuit formed by the transformer and capacitor, the leakage inductance becomes part of the resonant system rather than a loss mechanism, improving overall efficiency.
2Ease of manufacture
If the capacitor and transformer are connected in parallel, then the circuit is easy to implement, but inductance leakage prevents real resonant operation and reduces power converting efficiency
Solution Approach 1:
The patent introduces dynamic control of the MOS tubes to achieve resonant operation. By controlling the switching timing and duration of the MOS tubes, the circuit dynamically adjusts to maintain resonant conditions, allowing the capacitor and transformer to operate as a true resonant system rather than a static parallel connection.
Solution Approach 2:
The MOS tubes serve multiple functions: they act as switches for power transfer, as resonant elements when properly timed, and as controllable impedance elements to manage the interaction between the capacitor and transformer. This multi-functionality allows the same components to achieve both ease of implementation and resonant operation.
3Device complexity
If traditional PWM control is used, then the control circuit is simple, but power transfer efficiency is reduced due to non-resonant operation
Solution Approach 1:
The patent changes the control parameter from fixed PWM duty cycle to variable switching frequency that tracks the resonant frequency of the LC circuit. This parameter change enables the system to operate at maximum efficiency by maintaining resonant conditions across different load and voltage conditions.
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 solution enhances power transfer efficiency, stabilizes load operation, protects the load from damage, and reduces power consumption by ensuring synchronous rectification and zero voltage transitions.
Implementation Method 1
The capacitor and the transformer connected in series constitute a LC resonant circuit. Power of the resonant circuit transfers from the primary side to the secondary side of the transformer.
Implementation Method 2
Power of the primary side of a transformer is transferred to the output circuit of the secondary side mainly by the means of resonance
Data Source
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AI summary
The present disclosure relates to a resonant rectifying device, a control method and an apparatus for resonant rectifying. In the resonant rectifying device, a rectifying diode in the secondary side of the resonant rectifying device is replaced by a MOS transistor. According to the present disclosure, power utilization rate may be increased by resonating and synchronous rectifying of the primary side and the secondary side of the resonant rectifying device circuit.