Spread-Spectrum Switching Regulator Eliminates Modulation Ripple
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Solution Overview
Problem
Current switching regulators experience modulation ripple due to varying switching frequencies, which leads to spurious emissions and reduced spur-free dynamic range (SFDR), especially when the modulation rate is low, and can introduce noise and interference in electronic equipment.
Innovation Solution
A spread-spectrum switching regulator that includes a high gain amplifier, compensation circuit, ramp generator, pulse width modulator, driver circuit, and LC network, which generates a differential voltage and maintains a constant duty cycle by adjusting the ramp waveform's slope or pedestal voltage in response to switching frequency variations, thereby minimizing modulation ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching frequency is continuously modulated to increase SFDR, then spurious emissions are reduced, but modulation ripple is introduced at the modulation rate
Solution Approach 1:
The patent implements dynamic adjustment of the ramp waveform characteristics (slope or pedestal voltage) in response to switching frequency variations. The ramp generator continuously adapts the ramp parameters to maintain constant duty cycle despite spread-spectrum frequency modulation, thereby eliminating modulation ripple while preserving SFDR improvements
Solution Approach 2:
The patent employs feedback mechanisms where the actual switching frequency is monitored and used to adjust the ramp waveform parameters. The control system detects frequency deviations and dynamically compensates by modifying the ramp slope or pedestal voltage to maintain constant duty cycle, thus eliminating modulation ripple caused by frequency modulation
2Object-affected harmful factors
If the modulation rate is set low to avoid audible band spurs, then spurious emissions in audible band are reduced, but modulation ripple becomes more prominent
Solution Approach 1:
The patent makes the ramp waveform characteristics dynamically adjustable based on the modulation rate and switching frequency. By continuously adapting the ramp parameters in response to low-frequency modulation, the system eliminates modulation ripple that would otherwise be prominent at low modulation rates, while maintaining low audible band spurs
3Stability of the object's composition
If the switching frequency is varied to eliminate ripple, then output voltage stability is improved, but duty cycle varies causing modulation ripple
Solution Approach 1:
The patent changes the parameters of the ramp waveform (slope or pedestal voltage) in response to switching frequency variations. By adjusting these ramp parameters dynamically, the system maintains constant duty cycle despite frequency modulation, thereby eliminating modulation ripple while preserving output voltage stability benefits
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 eliminates modulation ripple, maintains a constant duty cycle, and increases the spur-free dynamic range (SFDR) by adaptively managing the switching frequency, allowing for higher modulation rates without introducing noise or interference.
Implementation Method 1
The pulsed waveform is further averaged to an approximately constant voltage level by using an LC network
Implementation Method 2
The pulsed waveform is further averaged to an approximately constant voltage level by using an LC network
Implementation Method 3
a high gain amplifier that is responsive to a reference voltage and a feedback voltage from a feedback loop to generate a differential voltage
Implementation Method 4
a compensation circuit, coupled to the high gain amplifier, that maintains stability of the feedback loop to generate an error level voltage
Implementation Method 5
a pulse width modulator, coupled to the compensation circuit and the ramp generator, that compares the error level voltage and the ramp waveform to generate a pulsed waveform
Data Source
AI summary
A spread-spectrum switching regulator for eliminating modulation ripple includes high gain amplifier that is responsive to reference voltage and feedback voltage of feedback loop to generate differential voltage, the feedback voltage being one of output voltage of the spread-spectrum switching regulator and a fraction of the output voltage; compensation circuit, coupled to the high gain amplifier, that maintains stability of the feedback loop to generate error level voltage in response to differential voltage; ramp generator that generates ramp waveform with slope adaptable to switching frequency to maintain duty cycle at constant value; pulse width modulator, coupled to compensation circuit and ramp generator, that compares error level voltage and ramp waveform to generate pulsed waveform; driver circuit, coupled to pulse width modulator, that drives the pulsed waveform to alternately switch a pair of transistors; and LC network, coupled to the pair of transistors, to average pulsed waveform to the output voltage.