Bidirectional Solid-State Switch Inrush Limiting With MOSFET-IGBT Control
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Solution Overview
Problem
Solid state switches in electrical systems are susceptible to damage from current inrush and voltage spikes due to load capacitance and inductance, which existing technologies fail to adequately mitigate.
Innovation Solution
A bidirectional switching circuit employing a control board with sensors, field effect transistors, and insulated gate bipolar transistors, along with inrush resistors and diodes, to regulate operations and manage current inrush and voltage spikes by adding impedance during switching events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid state switch is engaged to energize a capacitive load, then the load can be powered on, but a large inrush of current can damage the solid state switch
Solution Approach 1:
The circuit performs preliminary action by charging the load capacitance through a current limiting path (resistor and/or inductor) before the main solid state switch is fully engaged. This pre-charging phase limits the inrush current to safe levels, and only after the capacitance is charged does the switch transition to its low-impedance on state, preventing damage to the switch.
Solution Approach 2:
The patent introduces intermediary components (current limiting resistors and/or inductors) that mediate between the power source and the capacitive load during the switching transition. These intermediaries temporarily limit the current flow during the energizing phase, protecting the solid state switch from inrush current damage while still allowing the load to be powered on.
2Reliability
If a solid state switch is disengaged from an inductive load, then the switch can be turned off, but the inductance causes a voltage spike that can damage the solid state switch
Solution Approach 1:
The patent converts the harmful inductive voltage spike into a beneficial controlled energy dissipation process. By providing a designated energy dissipation path with resistive elements, the circuit allows the inductive energy to be safely converted into heat through controlled resistance, rather than creating a damaging voltage spike. The voltage spike is thus transformed into a controlled, harmless current flow through the dissipation path.
Solution Approach 2:
The patent introduces intermediary energy dissipation paths (resistive elements) that mediate between the inductive load and the solid state switch during the disengagement phase. These intermediaries provide a controlled path for the inductive kickback current, limiting the voltage spike magnitude and protecting the switch from damage while still allowing the switch to turn off.
3Adaptability or versatility
If bidirectional switching capability is implemented, then the switch can control power flow in both directions, but the complexity of managing current inrush and voltage spikes in both directions increases
Solution Approach 1:
The bidirectional switch is segmented into four individual solid state switches arranged in a bridge configuration, with each switch handled independently by its own controller. This segmentation allows each controller to manage its respective switch's inrush current and voltage spike protection independently, simplifying the control logic while achieving bidirectional capability. The segmentation of protection paths for each switch further reduces complexity by isolating the protection mechanisms.
Solution Approach 2:
The patent implements universal protection paths that serve multiple functions: the same energy dissipation resistors and inductor paths are used for both inrush current limiting and voltage spike suppression. This multi-functionality reduces the overall component count and circuit complexity compared to having separate protection circuits for each function, while still providing comprehensive protection for bidirectional operation.
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 or eliminates current inrush and voltage spikes, protecting the solid state switches and improving operational efficiency by managing impedance and energy dissipation during energizing and de-energizing processes.
Implementation Method 1
a first field effect transistor and a second field effect transistor electrically connected in a common source configuration
Implementation Method 2
Each field effect transistor may optionally have a Schottky diode electrically connected between the source and drain
Implementation Method 3
if the load exhibits an inductance, such as with the coils of an electric motor, when the switch is disengaged the inductance will cause a voltage spike
Implementation Method 4
When a switch is engaged the applied voltage may see a capacitance due to the load. The impedance of an uncharged capacitor is initially essentially zero
Data Source
AI summary
A bidirectional switch and a method of the bidirectional switch including, a first enhancement mode n-channel metal oxide semiconductor field effect transistor (n-MOSFET) and a second n-MOSFET electrically connected in a common source configuration. The emitter of an insulated gate bipolar transistor (IGBT) is further electrically connected to the common sources of the n-MOSFET. A control board regulates a first operation of the IGBT and an operation of the first field effect transistor. The control board additionally receives at least one measured characteristic, from a sensor and determines the measured characteristic is below a predetermined threshold. The control board then regulates an operation of the second field effect transistor and a second operation of the IGBT.