Switch Transistor Driver With Randomized Gate Strength for EMI Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switched mode power supplies (SMPS) face challenges in designing power-efficient systems that comply with electromagnetic interference (EMI) standards due to increased electromagnetic emissions caused by high switching speeds, despite using advanced power semiconductor components.
Innovation Solution
A method of driving a switching transistor using a variable strength driver circuit that modulates the drive strength based on a random or pseudo-random sequence, attenuating sharp peaks in the frequency spectrum of electromagnetic emissions by adjusting the output impedance, drive voltage, or drive current on a cycle-by-cycle basis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high switching speed is used to improve power efficiency, then switching losses decrease, but electromagnetic emissions increase
Solution Approach 1:
The patent applies dynamics by making the drive strength variable rather than fixed. The driver circuit dynamically adjusts its output impedance, drive voltage, or drive current on a cycle-by-cycle basis according to a random or pseudo-random sequence, allowing the switching characteristics to vary over time while maintaining high average switching speed for efficiency.
Solution Approach 2:
The patent changes the drive strength parameters (output impedance, drive voltage, or drive current) of the switching transistor driver according to a random or pseudo-random sequence. This parameter modulation spreads the electromagnetic energy spectrum, reducing peak emissions while preserving the high switching speed needed for low power losses.
2Productivity
If switching frequency is increased to improve power efficiency, then switching losses decrease, but EMI compliance becomes more difficult
Solution Approach 1:
The driver circuit dynamically modulates its drive strength according to a random or pseudo-random sequence, creating time-varying switching characteristics. This dynamic approach maintains high switching speed for productivity while spreading electromagnetic emissions across a broader frequency spectrum, improving EMI compliance.
Solution Approach 2:
The patent modifies the drive strength parameters (output impedance, drive voltage, or drive current) on a cycle-by-cycle basis using random or pseudo-random sequences. This parameter variation preserves the high switching frequency needed for efficiency while reducing peak electromagnetic emissions to meet compliance standards.
3Speed
If drive strength is increased to improve switching speed, then power efficiency improves, but electromagnetic emissions increase
Solution Approach 1:
The patent employs dynamic drive strength modulation where the driver circuit adjusts its output impedance, drive voltage, or drive current according to a random or pseudo-random sequence. This creates varying switching speeds over time, maintaining high average switching speed for efficiency while spreading electromagnetic emissions to reduce peak levels.
Solution Approach 2:
The drive strength parameters are changed on a cycle-by-cycle basis using random or pseudo-random sequences. This parameter modulation maintains the high switching speed needed for power efficiency while distributing electromagnetic energy across a wider frequency range, reducing harmful peak emissions.
Data Source
AI summary
In accordance with an embodiment, a method of driving a switching transistor includes receiving an activation signal for the switching transistor and generating a sequence of random values. Upon receipt of the activation signal, a control node of the switching transistor is driven with a drive strength based on a random value of the sequence of random values.