Clock Modulation Control Circuit for EMI Reduction
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Solution Overview
Problem
Conventional digital systems face challenges in reducing electromagnetic interference (EMI) caused by high-frequency clock signals, which affects reliability and performance, and existing solutions either require complex circuit designs or struggle to control current variations effectively.
Innovation Solution
A control circuit incorporating a periodic signal generator and a modulation controller with a delay unit, which adjusts the frequency of the modulation periodic signal by setting various delay periods based on control signals, allowing for precise timing of the feedback modulation signal to reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If EMI filters or snubbing devices are disposed at power input end to minimize electromagnetic interference, then electromagnetic interference is reduced, but manufacturing cost increases
Solution Approach 1:
The patent extracts the EMI reduction function from external components (EMI filters and snubbing devices) and implements it within the clock generator circuit itself through a modulation controller that generates feedback modulation signals. This eliminates the need for additional external EMI mitigation components, thereby reducing manufacturing cost while maintaining EMI reduction effectiveness.
Solution Approach 2:
The clock generator performs self-regulation of its own EMI through the modulation controller that generates feedback modulation signals based on the clock signal. The system serves itself by internally controlling its electromagnetic interference without requiring external EMI filters or snubbing devices, thus avoiding additional manufacturing costs.
2Ease of operation
If D/A converter output current is combined with oscillator current to control frequency, then frequency control is achieved, but current variation control is insufficient due to large current difference
Solution Approach 1:
The patent changes the parameter domain from current control to voltage control. Instead of combining D/A converter current with oscillator current (which has large current difference), the system uses a voltage control oscillator where the D/A converter output voltage directly controls the oscillator frequency. This parameter transformation enables precise frequency control without the current matching problems.
Solution Approach 2:
The patent introduces a voltage control mechanism as an intermediary between the D/A converter and the oscillator. Rather than directly combining currents, the D/A converter output voltage serves as an intermediary control signal that adjusts the oscillator frequency through voltage-controlled timing components, achieving precise control without direct current interaction.
3Adaptability or versatility
If multiple resistors and switches are used to generate multiple input reference voltages and select output voltage, then voltage control is achieved, but circuit design becomes complicated
Solution Approach 1:
The patent makes the single D/A converter serve multiple functions: it generates the feedback modulation signal, provides voltage control for the oscillator, and enables frequency adjustment without requiring separate voltage reference generation circuits or multiple switches. This multi-functionality reduces circuit complexity while maintaining adaptability.
Solution Approach 2:
The patent merges the voltage reference generation, voltage control, and frequency selection functions into a single integrated path through the D/A converter and modulation controller. Instead of having separate resistor networks and switch matrices for voltage control, the system combines these functions into the feedback modulation signal generation process, significantly simplifying the circuit design.
Data Source
AI summary
A control circuit for reducing electromagnetic interference is provided. The control circuit includes a periodic signal generator and a modulation controller. The periodic signal generator adjusts a modulation periodic signal generated by the periodic signal generator, according to a feedback modulation signal. The modulation controller is coupled to the periodic signal generator, for receiving the modulation periodic signal, and adjusting a frequency of the received modulation periodic signal according to a plurality of delay periods set according to a plurality of control signals, and generating the feedback modulation signal.