Capacitive Solid State Relay for Fast Gate Drive
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Solution Overview
Problem
Traditional opto-based solid state relays face inefficiencies in power transmission across isolation barriers, leading to slow startup times and limited ability to drive larger gate loads due to inefficiencies and temperature variability.
Innovation Solution
The implementation of a capacitive isolation communication channel using a first die with an oscillator, charge pump, and driver circuit to generate a boosted voltage and transmit signal, which is received and boosted on a second die to control a transistor, allowing for faster power transfer and reduced temperature dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If optical isolation is used to transmit signals across the isolation barrier, then the solid state relay can control the transistor, but the power transmission efficiency is low and startup time is slow
Solution Approach 1:
The patent replaces the optical isolation mechanism with an electromagnetic field-based isolation mechanism. Instead of using light-emitting diodes and photodetectors, the invention uses a primary winding and secondary winding coupled through an isolation barrier to transmit signals electromagnetically. This substitution of the isolation mechanism enables more efficient power transmission and faster startup times while maintaining electrical isolation between the control circuit and the power circuit.
2Reliability
If optical components are used for isolation, then the relay can provide isolation, but the temperature variability is high and turn-on time increases
Solution Approach 1:
The patent substitutes optical components with electromagnetic coupling components. The primary winding receives the control signal and generates a magnetic field that couples through the isolation barrier to the secondary winding, which generates the output signal. This electromagnetic approach eliminates the temperature sensitivity inherent in optical components while providing faster response times, as electromagnetic coupling is inherently faster and more stable across temperature variations.
3Power
If a larger FET is used to drive larger gate loads, then the power handling capability increases, but the turn-on time becomes slower
Solution Approach 1:
The patent introduces a secondary winding as an intermediary between the control circuit and the FET gate. The primary winding receives the control signal and couples it through the isolation barrier to the secondary winding, which then provides the amplified signal to drive the FET gate. This intermediary electromagnetic coupling mechanism enables faster charging of the FET gate capacitance, allowing larger FETs to turn on more quickly while maintaining their high power handling capability.
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 enables faster startup times, up to ten times faster than opto-based methods, and increased power transfer capability with reduced temperature dependence, facilitating the control of larger gate loads.
Implementation Method 1
coupled to the first die through a capacitive isolation communication channel
Implementation Method 2
A transmit side charge pump is coupled to the clock signal and boosts a voltage supplied to the charge pump to generate a boosted voltage
Data Source
AI summary
An oscillator supplies a clock signal having a frequency determined in part according to a received current. A transmit side charge pump is coupled to the clock signal and boosts a voltage supplied to the charge pump to generate a boosted voltage. A driver circuit drives a transmit signal having a frequency based on the clock signal and a voltage based on the boosted voltage to a capacitive isolation communication path. A receive side charge pump is coupled to the isolation capacitors of the isolation communication path and boosts a voltage of the received signal on the receive side of the isolation communication path and supplies a gate signal with the boosted voltage to a gate of at least one transistor.