Switching Regulator Frequency Locking for Stable Hysteretic Control
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Solution Overview
Problem
Existing hysteretic control methods for switching regulators suffer from variable switching frequency and slow frequency locking speed, particularly under heavy load conditions and in the presence of noise, which affects frequency accuracy and stability.
Innovation Solution
A frequency locking circuit is introduced that generates a periodic threshold signal with distinct signal portions synchronized to a reference clock signal, allowing for precise control of power switch operation and rapid frequency locking, using a frequency locking circuit with a control switch, control capacitor, and current source to adjust the threshold signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hysteretic control is used to control switching regulator, then the control simplicity is improved, but the switching frequency stability deteriorates
Solution Approach 1:
The patent implements a frequency lock loop (FLL) that continuously monitors the actual switching frequency and adjusts the hysteresis window dynamically to maintain the target frequency. The FLL compares the actual switching frequency with the target frequency and modifies the hysteresis window accordingly, creating a closed-loop feedback system that stabilizes the switching frequency while preserving the simplicity of hysteretic control.
Solution Approach 2:
The hysteresis window is transformed from a static fixed value to a dynamic adjustable parameter. The FLL dynamically modifies the hysteresis window width based on frequency deviation, allowing the system to adapt its control characteristics in real-time to maintain stable switching frequency under varying load and operating conditions.
2Measurement precision
If FLL is applied to lock switching frequency, then the frequency accuracy is improved, but the frequency locking speed deteriorates
Solution Approach 1:
The FLL employs periodic sampling of the switching frequency at defined intervals rather than continuous monitoring. This periodic action allows the system to achieve frequency locking within a predetermined number of cycles, balancing accuracy with speed by updating the hysteresis window at optimal moments in the switching cycle.
Solution Approach 2:
The FLL implements adaptive adjustment of the hysteresis window parameter based on the magnitude and direction of frequency deviation. When frequency error is large, the FLL makes aggressive adjustments to accelerate locking; when frequency approaches the target, adjustments become finer to maintain accuracy, thus optimizing both locking speed and frequency accuracy.
3Stability of the object's composition
If FLL adjusts hysteresis window to maintain target frequency, then the frequency stability is improved, but the noise sensitivity increases
Solution Approach 1:
The FLL applies partial adjustment to the hysteresis window rather than full correction of frequency deviations. By making controlled, limited adjustments rather than aggressive corrections, the system achieves frequency stability while minimizing the amplification of noise and preventing oscillatory behavior that could arise from over-correction.
4Measurement precision
If digital FLL is implemented to generate hysteresis window, then the frequency control precision is improved, but the device complexity increases
Solution Approach 1:
The digital FLL is integrated into the existing control architecture of the switching regulator, allowing it to perform multiple functions: frequency monitoring, hysteresis window generation, and dynamic adjustment. This multi-functionality reduces the need for separate dedicated circuits and minimizes overall device complexity while maintaining high frequency control precision.
Data Source
AI summary
A switching regulator is provided. The switching regulator generates an output voltage based on an input voltage using at least one power switch and an inductor. The switching regulator includes a first control circuit for generating a first control signal for turning off the power switch, in dependence of a level of the inductor current through the inductor. The switching regulator further includes a second control circuit for generating, based on a reference clock signal for setting a switching frequency of the switching regulator, a second control signal for turning on the power switch, in dependence of the level of the inductor current through the inductor. The switching regulator further includes a frequency locking circuit coupled to the second control circuit and for generating a periodic threshold signal based on the reference clock signal to control the generation of the second control signal.