Digital Pulse Controller Frequency Targeting Ultrasonic Mode
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Solution Overview
Problem
Traditional pulse-frequency modulated (PFM) controllers face issues with audible switching noise due to varying switching frequencies, leading to efficiency sacrifices when transitioning to pulse-width modulation (PWM) to avoid noise, and increased switching losses with heavier loads.
Innovation Solution
A digital pulse controller employing a frequency targeting mode and an ultrasonic mode, where the ultrasonic mode keeps pulse frequencies above the audible range by adjusting the ratio of high-side to low-side pulse on-times and using a higher reference voltage, and the frequency targeting mode ensures frequencies remain within a desired range through dynamic pulse size adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional PFM control is used with fixed pulse width, then high efficiency is achieved during light load conditions, but switching frequency drops into audible range causing audible noise
Solution Approach 1:
The patent applies dynamics by making the pulse width variable rather than fixed. The controller dynamically adjusts the pulse width based on the measured switching frequency - when frequency approaches the audible threshold, the pulse width is reduced to push frequency above the audible range, and when frequency is safely above threshold, pulse width is increased to maintain efficiency. This dynamic adjustment resolves the contradiction between maintaining high efficiency and avoiding audible noise.
Solution Approach 2:
The patent implements feedback by continuously measuring the switching frequency and using this information to adjust the pulse width in subsequent cycles. The frequency measurement feeds back to the control logic which modifies the pulse width accordingly, creating a closed-loop system that automatically maintains frequency above the audible threshold while optimizing for efficiency.
2Object-affected harmful factors
If PWM is used instead of PFM to avoid audible noise, then switching frequency remains stable above audible range, but efficiency decreases during light load conditions
Solution Approach 1:
The patent uses dynamics by implementing variable pulse width that adapts to operating conditions. During light load conditions, the pulse width is optimized to maintain frequency above audible threshold while minimizing switching losses. During heavy load conditions, the pulse width adjusts to handle the higher power requirements. This dynamic behavior allows the system to achieve both low switching losses and audible noise avoidance, unlike fixed PWM which incurs constant switching losses.
Solution Approach 2:
The patent applies parameter changes by modifying the pulse width parameter based on operating conditions and frequency measurements. Rather than using fixed PWM parameters, the system dynamically changes the pulse width parameter to optimize both efficiency and noise performance across different load conditions, resolving the contradiction between energy loss and noise avoidance.
3Device complexity
If fixed pulse width is used in PFM, then control is simple, but switching frequency increases proportionally with load causing increased switching losses
Solution Approach 1:
The patent applies dynamics by making the pulse width variable and adaptive. Instead of fixed pulse width that causes frequency to increase linearly with load, the system dynamically adjusts pulse width based on frequency measurements. This prevents excessive frequency increases during heavy load conditions, thereby reducing switching losses while adding only moderate control complexity through frequency measurement and conditional adjustment logic.
Data Source
AI summary
A digital pulse controller uses digital logic to send pulses to a high side and low side switches of a switch-mode power supply converter. The digital logic uses a pulse frequency mode which includes a frequency targeting mode and an ultrasonic mode. The frequency targeting mode dynamically adjusts the size of the pulses in order to achieve a switching frequency within a desired band. The ultrasonic mode is switched into when the frequency of the pulses are at or below a threshold and the time of the pulses reaches a minimum threshold.