Coupled-Inductor PWM Phase Control for Zero-Voltage Switching
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Solution Overview
Problem
Existing power circuits face significant switching losses due to transitions between switch states, which can be mitigated through Zero Voltage Switching (ZVS) to reduce power dissipation.
Innovation Solution
A switching circuit incorporating a coupled inductor and a controller to manage the phase difference between PWM signals for switch legs, ensuring ZVS conditions are met by controlling the ripple current through the inductor windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional switching is used in power circuits, then switching operations can be performed, but switching losses occur due to voltage and current overlap during state transitions
Solution Approach 1:
The patent applies preliminary action by using the coupled inductor to pre-charge or discharge the parasitic capacitance of the switch before the actual switching event. The inductor current is prepared in advance to ensure that when the switch transitions, the voltage across it is already at or near zero, thereby eliminating switching losses without requiring complex additional circuitry.
Solution Approach 2:
The coupled inductor serves as an intermediary element between the power source and the switch. It mediates the energy transfer by storing and releasing energy in a controlled manner, enabling the switch to transition states without direct voltage-current overlap. The inductor acts as a buffer that decouples the harsh switching action from the power transfer function.
2Loss of energy
If ZVS is implemented to reduce switching losses, then power dissipation during transitions is reduced, but control complexity increases due to phase difference management
Solution Approach 1:
The patent employs feedback by continuously monitoring the voltage across the switch and the current through the coupled inductor. The controller uses this feedback information to dynamically adjust the phase difference between PWM signals, ensuring that ZVS conditions are maintained across varying operating conditions. This closed-loop control automatically adapts to changes in load and input voltage, simplifying the overall control strategy.
Solution Approach 2:
The patent changes the phase difference parameter between PWM signals as a function of operating conditions. By dynamically adjusting this parameter, the system maintains optimal ZVS performance across different loads and input voltages. The phase difference is modified to compensate for variations in switching characteristics, ensuring consistent low-loss operation without requiring complex control algorithms.
3Loss of energy
If phase difference control is applied to achieve ZVS, then switching losses are reduced, but measurement precision requirements increase for voltage timing detection
Solution Approach 1:
The patent applies beforehand cushioning by designing the coupled inductor with sufficient energy storage capability to ensure that the voltage transition is gradual and well-defined. This cushioning effect creates a clear, measurable voltage ramp that is easier to detect precisely, reducing the measurement precision requirements compared to abrupt switching transitions. The inductor current acts as a buffer that smooths the voltage transition timing.
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 effectively reduces conduction losses by ensuring switches operate at zero voltage, enhancing efficiency in power converters like inverters and buck converters.
Implementation Method 1
a coupled inductor comprising: a first winding; and a second winding, wherein the first winding is coupled between the first switching node and a third node, and wherein the second winding is coupled between the second switching node and the third node
Data Source
AI summary
A switching circuit may comprise first and second switch legs and a coupled inductor. The controller may operate the first and second switch legs to control a current flowing through the coupled inductor such that zero voltage switching (ZVS) may be applied to the first and second switch legs. The system may determine a switching event time of a switch in the first switch leg, and determine a switching node voltage rise event time of the first switch leg based on a voltage measured at a switching node of the first switch leg. The controller may drive one or more switches using PWM signals. For example, the controller may drive one or more switches based on determining, for a switching instance, a phase difference between a first PWM signal and a second PWM signal for generating a ripple current for ZVS.