Switching Converter Nonlinear Capacitance Voltage Spike Suppression
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Solution Overview
Problem
Switching converters face challenges with electromagnetic interference radiation and overvoltages due to rapid changes in current through inductive storage elements during transitions from switched-on to switched-off phases, leading to voltage spikes at parasitic inductances.
Innovation Solution
Incorporating capacitive elements with nonlinear capacitance characteristics between the load path terminals of the switching element and rectifier element, which slow down the voltage rise during transition phases by varying capacitance based on voltage, thereby reducing voltage spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching element is switched off rapidly to improve switching speed and converter responsiveness, then the switching speed is improved, but voltage spikes occur at parasitic inductances causing electromagnetic interference and overvoltages
Solution Approach 1:
The patent applies beforehand cushioning by introducing a capacitive element with nonlinear capacitance characteristic that is activated in advance during the transition phase. This capacitive element provides a temporary energy buffer that cushions the rapid current change when the switching element turns off, preventing voltage spikes at parasitic inductances before they can occur. The nonlinear capacitance increases as voltage rises, providing progressive cushioning during the transition.
Solution Approach 2:
The patent employs parameter changes by using a capacitive element whose capacitance value is not fixed but varies with voltage according to a nonlinear characteristic curve. The capacitance parameter changes dynamically during operation - being smaller at low voltages and larger at high voltages - which allows the system to adapt to different operating conditions and effectively suppress voltage spikes during the critical transition phase while maintaining normal operation during steady states.
2Loss of energy
If the current through the inductive storage element changes rapidly during transition phase to improve power conversion efficiency, then the power conversion efficiency is improved, but overvoltages occur at parasitic inductances
Solution Approach 1:
The capacitive element with nonlinear capacitance provides beforehand cushioning by being pre-positioned in the circuit to handle the abrupt current transfer from the switching element to the rectifier element. During the transition phase, it cushions the rapid current change that would otherwise cause overvoltages at parasitic inductances, thereby protecting components from excessive voltage stress while allowing efficient power transfer.
Solution Approach 2:
The capacitive element acts as an intermediary between the switching element and the rectifier element during the transition phase. It mediates the current transfer by temporarily storing energy and releasing it in a controlled manner, preventing direct abrupt current changes that would cause overvoltages at parasitic inductances. This intermediary function allows rapid switching while protecting against voltage stress.
3Object-affected harmful factors
If a linear capacitive element is used to suppress voltage spikes, then voltage spike suppression is improved, but the device complexity and component count increase
Solution Approach 1:
Instead of adding multiple linear capacitive elements, the patent uses a single capacitive element with nonlinear capacitance characteristic. The capacitance parameter changes with voltage, providing variable suppression capability - offering higher capacitance when voltage spikes occur and lower capacitance during normal operation. This dynamic parameter change eliminates the need for multiple fixed-value capacitors, reducing device complexity while maintaining effective voltage spike suppression.
Solution Approach 2:
The capacitive element with nonlinear capacitance performs multiple functions: it suppresses voltage spikes during transitions, stores energy during operation, and adapts its characteristics based on operating conditions. This multi-functionality replaces what would traditionally require multiple specialized components, thereby reducing the overall device complexity and component count while maintaining comprehensive protection against voltage spikes.
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 voltage spikes at parasitic inductances by controlling the rate of voltage rise, enhancing the stability and efficiency of switching converters during transitions.
Implementation Method 1
A first capacitive element is between the load path terminals of the switching element and has a first capacitance having a nonlinear capacitance characteristic curve that is dependent on a voltage between the load path connections
Data Source
AI summary
A switching converter including a rectifier element with nonlinear capacitance. One embodiment provides a switching element configured to be driven in the on state and in the off state. A first capacitive element is between the load path terminals of the switching element and has a nonlinear capacitance characteristic curve dependent on a voltage between the load path connections. A rectifier element is coupled between the inductive storage element and the capacitive storage element such that it enables a current flow between the inductive storage element and the capacitive storage element when the switching element is driven in the off state. A second capacitive element is between the load path terminals of the rectifier element and has a nonlinear capacitance characteristic curve dependent on a voltage between the load path connections.