Resonant Auxiliary Circuit for Switch Protection
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Solution Overview
Problem
Power converters face increased switching losses and risk of oxide breakdown due to high switching frequencies, which limits their operational frequency and increases thermal strain and EMI noise, necessitating a solution to reduce losses and protect transistors from excessive voltage.
Innovation Solution
A resonant power converter with a resonant auxiliary switching circuit and electrical safety components, including Zener diodes, that control current flow and prevent excessive voltage across transistors, allowing high-frequency operation with reduced switching losses and EMI noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching frequency is increased to improve output control accuracy and reduce switching ripple, then the output control accuracy and EMI are improved, but the switching losses increase due to more frequent commutation cycles
Solution Approach 1:
The auxiliary resonant circuit performs preliminary action by pre-charging or pre-discharging the main switch voltage before the actual switching event. This prepares the voltage conditions in advance to enable zero-voltage switching, thereby reducing switching losses while maintaining high switching frequency for accurate output control
Solution Approach 2:
The auxiliary switch and resonant capacitor act as intermediaries between the DC voltage source and the main switch. They mediate the voltage transfer process by temporarily storing and transferring energy, allowing the main switch to operate under optimized voltage conditions that reduce switching losses
2Volume of moving object
If the switching frequency is increased to reduce switching ripple and component values, then the component size and EMI are reduced, but the switching losses increase due to higher commutation frequency
Solution Approach 1:
The resonant circuit performs preliminary voltage preparation before main switch commutation, enabling the system to operate at higher frequencies with smaller components while maintaining low switching losses through zero-voltage switching conditions
3Loss of energy
If the gate oxide layer is made thinner to reduce the energy required for transistor commutation, then the switching losses are reduced, but the risk of oxide breakdown increases due to higher electric field stress
Solution Approach 1:
The auxiliary resonant circuit provides beforehand cushioning by preparing the voltage conditions prior to switching, ensuring that the main switch experiences minimal voltage stress during commutation. This protective action in advance allows the use of thinner gate oxide layers without excessive breakdown risk
Solution Approach 2:
The auxiliary switch and resonant circuit serve as intermediaries that buffer and control the voltage stress on the main switch. They mediate the voltage transfer to reduce peak electric field stress on the gate oxide, enabling thinner oxide layers with acceptable reliability
4Loss of energy
If auxiliary switch resistance is reduced to lower switching losses, then the switching efficiency is improved, but the transistor must still commutate with potential difference requiring gate signal energy
Solution Approach 1:
The auxiliary switch performs preliminary commutation action before the main switch operates, preparing the voltage conditions in advance. This preliminary action reduces the voltage across the main switch during its switching event, thereby reducing both conduction losses and gate signal energy requirements
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
Enables high-accuracy, high-frequency operation with reduced thermal strain and EMI noise, extending the lifespan of transistors and allowing for more compact and cost-effective designs by minimizing heat generation and eliminating the need for cooling.
Implementation Method 1
a resonant component to the circuitry in which a current is generated by an inductive element, by the discharge of a capacitor. A circuit employing this technique is known as a resonant converter, and the method of using resonance to facilitate commutation is known as soft switching.
Implementation Method 2
The first electrical safety component being adapted to: hinder the current from flowing from the positive DC conductor to the phase conductor, and allow current to flow from the auxiliary switching circuit to the positive DC conductor when the potential difference between the positive DC conductor and the auxiliary switching circuit is above a threshold voltage.
Data Source
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AI summary
A resonant power converter comprising electrical safety components (29b) comprising a combination of a diodes (Dn2) and a zener diodes (Zn) coupled between DC conductors and an auxiliary switching circuit, the diodes being adapted to hinder the current from flowing from the auxiliary switching circuit to the negative DC conductor, and the zener diodes being adapted to allow current to flow from the negative DC conductor to the auxiliary switching circuit when the potential difference between the negative DC conductor and the phase conductor is above a threshold voltage. The Zener diodes being selected such that the threshold voltage of the Zener diodes is below the maximum blocking voltage of the transistors.