Analog Oscillator Frequency Modulation for EMI Peak Reduction
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Solution Overview
Problem
High power analog blocks, such as high-voltage charge pumps, generate electromagnetic interference (EMI) due to synchronized current and voltage variations at specific frequencies, which can harm nearby sensitive electronic devices like Bluetooth transmitters.
Innovation Solution
A frequency modulator is used to vary the clock frequency of oscillators in these blocks, spreading EMI energy over a wide spectrum by alternately providing charge and discharge currents during charging and discharging stages, thereby reducing peak energy at the main frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed-frequency oscillator is used to generate clock signals, then the system can provide stable timing for electronic devices, but it generates strong EMI at specific frequencies that interferes with nearby sensitive devices
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed-frequency oscillator to a variable-frequency oscillator. The oscillator frequency is modulated according to a spreading sequence, making the frequency dynamic rather than static. This dynamic frequency variation spreads the EMI energy across multiple frequencies while maintaining the timing function, thus resolving the contradiction between timing stability and EMI reduction.
Solution Approach 2:
The patent changes the frequency parameter of the oscillator dynamically. By modulating the oscillator frequency according to a spreading sequence, the EMI energy that would normally concentrate at a single frequency is distributed across multiple frequencies. This parameter change approach maintains the timing function while reducing peak EMI energy at any specific frequency.
2Object-generated harmful factors
If the clock frequency is varied to spread EMI energy, then EMI peak energy is reduced, but the timing stability may be compromised
Solution Approach 1:
The patent employs periodic action by using a spreading sequence to modulate the oscillator frequency in a structured, periodic manner. The frequency varies according to the spreading sequence pattern, which ensures that EMI energy is distributed while the periodic nature maintains predictable timing characteristics. This resolves the contradiction by providing both EMI spreading and timing reliability through the structured periodic modulation.
Solution Approach 2:
The system incorporates feedback mechanisms to maintain timing stability despite frequency variations. The spreading sequence modulation is controlled in a manner that ensures the timing function remains reliable, using feedback to adjust and maintain proper timing characteristics while achieving EMI reduction through frequency variation.
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
The solution effectively reduces EMI peak energy by approximately 30 times, spreading it across a wider frequency range, minimizing interference with sensitive electronic devices.
Implementation Method 1
A frequency modulator is used to vary the clock frequency of oscillators in these blocks, spreading EMI energy over a wide spectrum
Implementation Method 2
a device or a system including the fixed-frequency oscillator can emit radio frequency (RF) signals of sufficient magnitude that can cause electromagnetic interference (EMI)
Data Source
AI summary
Embodiments of the present disclosure provide systems and methods of reducing the EMI effect generated by such analog blocks. By varying the clock frequency in time of oscillators used by such analog blocks, the EMI energy may be spread over a wide spectrum range thereby reducing the peak energy for the main frequency. To achieve this, the oscillator frequency is directly varied using analog mechanisms. The mechanisms may be based on a synchronized method for increasing/decreasing the current that is charging/discharging the oscillator capacitor. The frequency variation may be achieved by analog control of the extra charge/discharge current.