Digital PFM Control for Power Converter Pulse Generation
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Solution Overview
Problem
Conventional power converters using analog techniques struggle to generate short high-side control pulses efficiently, especially in buck converters with smaller inductors and higher switching frequencies, due to start-up time issues, which are inadequate for meeting the requirements of nearly instant reaction times in pulse frequency modulation (PFM) operations.
Innovation Solution
A digital PFM solution is implemented, which includes a low-side controller that adjusts the duration of low-side control based on inductor current and a high-side controller that adjusts high-side control duration to maintain a constant PFM pulse length, minimizing inductor current ripple variations by toggling between low-side, high-side, and high-impedance control modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional analog techniques are used to generate high-side control pulses, then the control circuit can operate with simple structure, but the start-up time is too long and cannot meet nearly instant reaction time requirements
Solution Approach 1:
The patent replaces conventional analog control techniques with a digital control system that uses a processor to generate control pulses. The processor determines pulse widths based on feedback signals, enabling nearly instant reaction times while maintaining manageable complexity through software-based control logic.
Solution Approach 2:
The patent changes the operating parameters by using digital signal processing instead of analog circuitry. The processor dynamically adjusts pulse width parameters based on real-time feedback, allowing flexible and fast response without the inherent start-up delays of analog circuits.
2Duration of action of moving object
If the high-side control pulse length is reduced to achieve short pulses, then the reaction time improves, but the inductor current ripple variations increase
Solution Approach 1:
The patent implements a feedback mechanism where the processor monitors the output voltage and adjusts the control pulse width dynamically. This closed-loop control ensures that even with short pulse lengths, the inductor current ripple remains minimized by continuously optimizing the pulse duration based on actual system state.
Solution Approach 2:
The patent uses dynamic pulse width adjustment rather than fixed pulse lengths. The processor modifies the control signal duration in real-time based on feedback, allowing the system to maintain stability and minimize current ripple variations while operating with short control pulses.
3Productivity
If the switching frequency is increased to improve converter performance, then the efficiency improves, but the requirement for short control pulses becomes more stringent
Solution Approach 1:
The patent employs digital processing to generate control pulses at high switching frequencies. The processor can rapidly determine and output control signals with precise timing, meeting the stringent requirements of high-frequency operation where analog circuits would suffer from insufficient reaction time.
Data Source
AI summary
Methods and apparatus to digitally control pulse frequency modulation pulses in power converters are disclosed. An example apparatus includes a low-side controller structured to, when an inductor current corresponds to a first current direction during a low-side control signal of a power converter, decrease a first duration of the low-side control after the first duration; and when the inductor current corresponds to a second current direction during the low-side control signal of the power converter, increase the first duration of the low-side control after the first duration; and a high-side controller structured to, when a sum of the first duration and a second duration corresponding to a high-side control of the power converter does not satisfy target pulse length, increase a third duration of the high-side control after the third duration; and when the sum of the first duration and the second duration satisfies the target pulse length, decrease the third duration of the subsequent high-side control.