Power Converter Control Preventing Burst Mode Ripple
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Solution Overview
Problem
Power converters employing constant on-time control schemes experience burst mode under light load conditions, leading to excessive ripple voltage, which is undesirable in many applications.
Innovation Solution
A control scheme that includes a first and second switch, an inductor, an output capacitor, and a comparator with low-pass filters to generate feedback signals, allowing the power converter to operate in minimum switching frequency or turn-off modes when necessary, thereby preventing burst mode and improving voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If constant on-time control scheme is employed, then fast transient response is achieved, but burst mode occurs under light load conditions causing excessive ripple voltage
Solution Approach 1:
The patent implements dynamic switching frequency adjustment by detecting the output voltage and comparing it with reference voltages. When the output voltage exceeds the upper threshold, the switching frequency is reduced to minimum frequency; when it drops below the lower threshold, the switching frequency is increased. This dynamic adaptation prevents burst mode while maintaining fast transient response capability.
Solution Approach 2:
The patent employs a feedback control mechanism where the output voltage is continuously monitored and fed back to the control circuit. The control circuit compares the feedback voltage with upper and lower reference thresholds and adjusts the switching frequency accordingly. This closed-loop feedback prevents excessive ripple voltage by regulating the switching frequency based on actual output conditions.
2Device complexity
If constant on-time control scheme is used, then simple circuit design is achieved, but voltage regulation deteriorates under light load conditions
Solution Approach 1:
The patent adds dynamic voltage regulation capability by implementing switching frequency adjustment based on output voltage detection. The control circuit dynamically switches between minimum frequency mode and hysteretic control mode, ensuring stable voltage regulation under varying load conditions while maintaining relatively simple circuit architecture.
Solution Approach 2:
The patent changes the switching frequency parameter dynamically based on load conditions. By detecting output voltage and adjusting the switching frequency between minimum frequency and higher frequencies, the system maintains reliable voltage regulation across different operating conditions without significantly increasing circuit complexity.
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 prevents burst mode and enhances voltage regulation in power converters under light load conditions, reducing power losses and maintaining stable output voltage.
Implementation Method 1
The second feedback signal is generated by applying at least one low-pass filter to a switching ripple voltage
Implementation Method 2
a comparator having a first input connected to a reference, a second input configured to receive a sum of a first feedback signal and a second feedback signal
Implementation Method 3
an inductor connected between a common node of the first switch and the second switch
Implementation Method 4
an output capacitor and a comparator having a first input connected to a reference
Data Source
AI summary
A power converter comprises a first switch and a second switch connected in series between an input power source and ground, an inductor connected between a common node of the first switch and the second switch, and an output capacitor and a comparator having a first input connected to a reference, a second input configured to receive a sum of a first feedback signal and a second feedback signal and an output configured to generate a turn-on signal of the first switch, wherein the first feedback signal is proportional to an voltage across the output capacitor and the second feedback signal is generated by applying at least one low-pass filter to a switching ripple voltage.