Switch-Controlled Voltage Converter for Zero-Voltage Switching
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Solution Overview
Problem
Conventional voltage converters face inefficiencies and high switching losses due to the use of coreless transformers with low magnetizing inductance and high DC resistance, particularly at high switching frequencies, which limits their ability to transfer sufficient output current and power effectively.
Innovation Solution
A voltage converter design incorporating a switching circuit with a first and second pair of switches, a transformer with magnetizing and leakage inductance dependent on windings ratio, and a capacitor, where the switch control circuit sets a frequency to control the switches such that the peak capacitor voltage is within a percentage margin of the output voltage multiplied by the windings ratio, optimizing efficiency and output power by minimizing switching losses and utilizing zero voltage turn-on/off techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If coreless transformers with low magnetizing inductance are used, then device complexity is reduced, but switching losses increase and power transfer capability deteriorates
Solution Approach 1:
The patent changes the operating parameters by controlling the switch frequency and duty cycle to achieve zero voltage switching (ZVS). The control circuit adjusts the switching frequency dynamically to ensure that switches turn on when the voltage across them is near zero, thereby reducing switching losses despite using coreless transformers with low magnetizing inductance.
Solution Approach 2:
The patent implements continuous power transfer by using a full-bridge switching topology with complementary switching pairs. The circuit maintains continuous current flow through the transformer by ensuring that one pair of switches is always conducting, eliminating discontinuities in power transfer and reducing energy losses.
2Device complexity
If coreless transformers with high DC resistance are used, then device complexity is reduced, but power dissipation increases
Solution Approach 1:
The patent employs parameter changes by optimizing the switching frequency and duty cycle to achieve resonant operation. By operating at frequencies where the impedance of the transformer is minimized and reactive power is balanced, the circuit reduces the impact of high DC resistance and minimizes power dissipation.
Solution Approach 2:
The patent introduces a resonant capacitor as an intermediary element that forms an LC resonant circuit with the transformer inductance. This resonant circuit compensates for the high DC resistance by providing a low-impedance path for current flow at the operating frequency, thereby reducing power dissipation in the transformer.
3Speed
If high switching frequency is used, then power transfer speed is improved, but switching losses increase
Solution Approach 1:
The patent uses periodic switching action with complementary pairs of switches that operate in alternating phases. This periodic operation at high frequency enables rapid power transfer while the zero-voltage switching technique ensures that each switching event occurs at the optimal moment (when voltage is near zero), minimizing switching losses despite the high frequency.
Solution Approach 2:
The patent implements feedback control through a control circuit that monitors the voltage and current waveforms and dynamically adjusts the switching frequency and duty cycle. This feedback mechanism ensures that the circuit operates at the optimal frequency for zero voltage switching, maintaining high power transfer speed while minimizing switching losses.
4Device complexity
If conventional switching control is used, then device complexity is reduced, but output current capability deteriorates
Solution Approach 1:
The patent employs dynamic control by using a control circuit that continuously adjusts the switching frequency and duty cycle based on load conditions. This dynamic operation enables the circuit to maintain optimal performance across a wide range of output currents, achieving high output current capability while managing transformer saturation and switching losses effectively.
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 configuration enhances the efficiency and maximum output power capability of the voltage converter by reducing switching losses and enabling effective power transfer across the transformer, even at maximum load, while maintaining low power dissipation during switching events.
Implementation Method 1
A coreless transformer or other isolation device may be used to provide isolation between the primary side and the secondary side of the isolated driver. The primary side may transfer power to the secondary side
Implementation Method 2
The voltage converter includes a capacitor coupled to the transformer and the switching circuit
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A voltage converter is provided. The voltage converter comprises a switching circuit that includes a first pair of switches and a second pair of switches. The voltage converter comprises a transformer having a magnetizing inductance and a leakage inductance that are a function of a windings ratio of the transformer. The voltage converter comprises a capacitor coupled to the transformer and the switching circuit. The voltage converter comprises a switch control circuit configured to generate a frequency for controlling the first pair of switches and the second pair of switches. The frequency is set of a value to control the pairs of switches so that a peak capacitor voltage of the capacitor is a factor of an output voltage of the voltage converter and the windings ratio of the transformer.