Staggered Switching Control for Power Circuit EMI Reduction
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Solution Overview
Problem
In power systems, such as those used in hard disk drives and solid state drives, high-frequency switching in power circuits generates undesirable noise that can be magnified in thin ground planes, leading to electromagnetic interference (EMI) issues, particularly as form factors shrink and ground layers are reduced or eliminated.
Innovation Solution
The implementation of control circuitry that manages high-side and low-side switches in multiple power circuits to prevent them from switching on or off concurrently, using priority rankings and delay mechanisms to synchronize switching based on priority rankings, thereby mitigating noise amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-frequency switching is used in power circuits to supply power to different components, then power delivery efficiency is improved, but electromagnetic interference and noise on ground/power planes worsen
Solution Approach 1:
The patent applies periodic action by implementing non-concurrent switching schedules for multiple power circuits. Each power circuit operates with a periodic switching pattern, but the switching events are deliberately错相 (dephased) so that they do not occur simultaneously. This maintains the high-frequency periodic operation needed for efficient power delivery while distributing the electromagnetic noise events in time, preventing their constructive interference and magnification on the ground and power planes.
2Adaptability or versatility
If multiple power circuits operate concurrently with high-frequency switching, then power system functionality is improved, but noise magnification on ground planes worsens
Solution Approach 1:
The patent applies segmentation by dividing the operation of multiple power circuits into distinct, non-overlapping time segments. Each power circuit is assigned a specific time window within the overall switching period during which it can switch. This temporal segmentation ensures that while all power circuits remain functional and operational, their switching events are separated in time, preventing the simultaneous noise generation that causes magnification on thin ground planes.
3Volume of moving object
If ground layers are reduced or eliminated to achieve smaller form factors, then device compactness is improved, but susceptibility to noise worsens
Solution Approach 1:
The patent applies preliminary anti-action by proactively preventing the generation of simultaneous switching noise at its source, rather than attempting to mitigate or shield against it afterward. By implementing control logic that schedules power circuit switching events to occur at different times, the system preemptively eliminates the conditions that would create magnified noise on thin or absent ground planes, making the system inherently more susceptible to noise without requiring additional ground layer thickness.
Data Source
AI summary
A power system is disclosed including a plurality of power circuits, each power circuit providing an independent power output and including a high-side driver coupled to a high-side switch and a low-side drive coupled to a low-side switch, and control circuitry coupled to each of the power circuits. The control circuitry is operable to detect a present state of each high-side and low-side switch, and prevent two or more of the high-side switches from substantially concurrently switching from a first state to a second state, or two or more of the high-side switches and one or more of the low-side switches from substantially concurrently switching from a third state to a fourth state, or two or more of the low-side switches from substantially concurrently switching from the third state to the fourth state.