Switching Regulator Control Circuit with Variable Hysteresis Response
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Solution Overview
Problem
Hysteresis control switching regulators face challenges in maintaining a stable switching frequency, leading to difficulties in addressing electromagnetic interference (EMI) due to fluctuating switching frequencies.
Innovation Solution
A control circuit for a switching regulator that includes a hysteresis comparator with variable response speed, driven by a pulse width modulation signal, a phase comparator, and a loop filter, which stabilizes the switching frequency by adjusting the bias current and time constant of feedback circuits, ensuring the frequency aligns with a reference clock signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hysteresis control is used in a switching regulator, then load-responsiveness is improved, but switching frequency stability deteriorates
Solution Approach 1:
The patent implements a phase detection mechanism that compares the phase of the pulse signal with a reference clock signal, and uses this phase difference to adjust the response speed of the hysteresis comparator. This feedback loop enables the system to maintain stable switching frequency while preserving the fast load-responsiveness characteristic of hysteresis control.
Solution Approach 2:
The patent dynamically adjusts the response speed of the hysteresis comparator based on the detected phase difference. By making the comparator's response speed variable rather than fixed, the system can adapt to different operating conditions and maintain frequency stability without sacrificing load responsiveness.
2Adaptability or versatility
If switching frequency is allowed to fluctuate for load responsiveness, then adaptability is improved, but electromagnetic interference countermeasure effectiveness deteriorates
Solution Approach 1:
The phase detection and control mechanism provides continuous feedback to adjust the switching frequency, enabling the system to adapt to load changes while maintaining a stable fundamental frequency that is easier to filter and shield against electromagnetic interference.
Solution Approach 2:
The patent changes the response speed parameter of the hysteresis comparator dynamically, allowing the switching frequency to adapt to load conditions while preventing excessive frequency variation that would complicate EMI countermeasures.
3Speed
If the response speed of the hysteresis comparator is increased for faster control, then load-responsiveness is improved, but switching frequency fluctuation increases
Solution Approach 1:
The patent makes the response speed of the hysteresis comparator dynamically adjustable rather than fixed. The response speed is increased when needed for fast load response but reduced when frequency stability is compromised, creating an optimal balance between speed and stability.
Solution Approach 2:
The phase detection mechanism provides feedback that monitors the effect of response speed changes on switching frequency. This feedback enables automatic adjustment of the comparator's response speed to maintain frequency stability while preserving necessary responsiveness.
Data Source
AI summary
A control circuit for controlling a switching transistor of a switching regulator includes a hysteresis comparator circuit comparing a feedback voltage according to an output signal of the switching regulator with a reference voltage and a threshold voltage and outputting a pulse width modulation signal as an output signal of the hysteresis comparator circuit, where the threshold voltage has a hysteresis according to the pulse width modulation signal. The control circuit further includes a driver driving the switching transistor based on the pulse width modulation signal, a phase comparator generating a phase difference signal based on a phase difference between a reference clock signal and a pulse signal corresponding to the pulse width modulation signal, and a loop filter generating a control voltage by filtering the phase difference signal. The hysteresis comparator circuit is further configured to control a response speed thereof depending on the control voltage.