Quasi-Resonant DC-DC Converter Transistor Switching EMI Reduction
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Solution Overview
Problem
Quasi-resonant DC-DC voltage converters experience significant electromagnetic interference during the switching of transistors due to the discharge of input voltage into the transistor and resonance capacitor, which can exceed emission limits and reduce efficiency.
Innovation Solution
A method involving a timer-controlled reduction in the gate control current intensity for the transistor, from a high initial value to a lower value once a predefined duration threshold is reached, to minimize electromagnetic interference during the transient state before reaching the quasi-resonant steady state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate resistance value is lowered to speed up the discharge and reduce switching time, then the switching speed is improved, but electromagnetic interference increases causing emissions to exceed limits
Solution Approach 1:
The patent applies dynamics by making the gate resistance value variable rather than fixed. The resistance is adjusted dynamically based on the converter's operating state: a first resistance value is used during transient startup to limit electromagnetic interference, while a second (lower) resistance value is used during steady-state quasi-resonant operation to enable fast switching. This dynamic adaptation resolves the contradiction between switching speed and electromagnetic interference.
Solution Approach 2:
The patent changes the parameter of gate resistance value based on the converter's operational phase. During transient state, a higher resistance value limits the gate current to reduce electromagnetic emissions. Once the converter reaches steady-state quasi-resonant mode, the resistance is lowered to allow faster switching. This parameter change strategy resolves the technical contradiction by adapting the resistance to the operational requirements of each phase.
2Object-generated harmful factors
If the gate control current intensity is reduced to limit electromagnetic interference, then emissions are controlled, but the transistor switching speed decreases causing delays in synchronizing with the resonance interval
Solution Approach 1:
The patent dynamically adjusts the gate control current intensity based on the converter's operational phase. During transient startup, a lower current intensity limits electromagnetic emissions. Once steady-state quasi-resonant mode is achieved, the current intensity is increased to enable fast switching that synchronizes with the resonance interval. This dynamic adjustment resolves the contradiction between emission control and switching speed.
Solution Approach 2:
The patent changes the gate control current parameter according to the operational state. A first current intensity is applied during transient operation to control emissions, while a second (higher) current intensity is applied during steady-state operation to minimize switching delays. This parameter adaptation resolves the technical contradiction.
3Speed
If a high gate control current is used during transient state to ensure fast switching, then switching speed is improved, but electromagnetic interference increases exceeding emission limits
Solution Approach 1:
The patent dynamically controls the gate resistance and current based on the converter's operational phase. During transient startup, the system uses higher resistance and lower current to limit electromagnetic emissions even though switching is slower. Once steady-state is reached, the resistance and current are optimized for fast switching. This dynamic control strategy resolves the contradiction between switching speed and emission levels.
Solution Approach 2:
The patent applies parameter changes by adjusting gate resistance and control current intensity according to the operational state. During transient mode, parameters are set to prioritize emission control. During steady-state quasi-resonant mode, parameters are optimized for switching speed. This adaptive parameter adjustment resolves the technical contradiction.
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 reduces electromagnetic interference without causing overheating, maintaining efficiency and ensuring compliance with emission limits by adjusting the control current intensity based on the state of the converter.
Implementation Method 1
The principle consists in charging a coil with current and in interrupting the current cyclically, using a switch, notably a transistor
Implementation Method 2
the converter comprises a resonance capacitor connected between the drain and the source of the transistor
Implementation Method 3
a gate resistor connected to the gate of the transistor
Data Source
AI summary
Disclosed is a method for reducing the electromagnetic interference produced during the switching to the on state of a transistor for switching a quasi-resonant DC-DC voltage converter. The method includes the steps of: the transistor being initially controlled so as to be in the on state on the basis of a first control current, controlling the driving module by way of the control module so that the driving module switches the transistor to the off state at a first instant; and triggering the timer from the first instant, and, if the timer reaches a predefined duration threshold, controlling, by means of the driving module, the transistor so as to be in the on state on the basis of a second control current the intensity of which is lower than the intensity of the first control current.