Switching Regulator EMI Reduction via Randomized Frequency
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Solution Overview
Problem
Voltage regulators (VRs) generate unpredictable Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI) due to switching, which can cause interference with nearby electrical components, particularly in on-chip VRs where these interferences can affect other components within the chip.
Innovation Solution
Incorporating a random number generator circuitry in the VR to randomize the switching frequencies by varying threshold values for the power stage switches, thereby distributing EMI and RFI across a broader frequency range, reducing their adverse effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching regulators use fixed frequency switching to regulate output voltage, then voltage regulation is achieved, but EMI and RFI are concentrated at specific frequencies causing interference to nearby components
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. A random number generator continuously varies the switching frequency around a nominal value, causing the EMI and RFI to be distributed across a broader frequency spectrum rather than concentrated at a single frequency, thereby reducing peak interference levels while maintaining voltage regulation functionality
Solution Approach 2:
The patent changes the frequency parameter of the switching signal by introducing random variations. The random number generator modifies the switching frequency parameter dynamically, transforming the EMI/RFI characteristics from a narrow-band concentrated spectrum to a wide-band distributed spectrum, which reduces the harmful effects at any specific frequency
2Volume of moving object
If on-chip VR is used to reduce size, then integration is improved, but EMI and RFI from switching affect other components within the same chip
Solution Approach 1:
The patent uses dynamic frequency variation to mitigate the proximity interference problem in integrated circuits. By continuously changing the switching frequency through random variations, the electromagnetic interference affects a broader frequency range at lower intensity, reducing the impact on other chip components that are physically close to the voltage regulator
Solution Approach 2:
The patent converts the harmful concentrated EMI/RFI into a beneficial distributed spectrum. The random frequency variation transforms the narrow-band high-intensity interference into wide-band low-intensity interference, which is less harmful to adjacent components on the same chip while maintaining the size benefits of integration
Data Source
AI summary
An apparatus is provided which comprises: at least two switches in series between an input voltage node and a ground terminal; an inductor coupled between a mid-point of the at least two switches and an output terminal; a first circuitry to compare a current through the inductor with a threshold current, and to control one or both of the at least two switches, based at least in part on the comparison; and a second circuitry to randomly vary the threshold current over consecutive cycles of switching of the at least two switches.