Adjustable Ramp Power Converter for Stability and Transient Response
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power converters employing the constant on-time control scheme face instability issues such as sub-harmonic oscillation, leading to excessive ripple voltage, which affects the stability and transient response, especially when the equivalent series resistance of the output capacitor is insufficient.
Innovation Solution
A control scheme with an adjustable ramp is implemented, where a ramp generator dynamically adjusts the amplitude of the ramp signal based on operating conditions, using a ramp capacitor and a dc blocking capacitor, and adjusting currents to maintain a consistent dc voltage level and ramp amplitude, thereby stabilizing the power converter and enhancing transient responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage ramp is injected into the feedback circuit to avoid sub-harmonic oscillation, then stability is improved, but transient response deteriorates
Solution Approach 1:
The patent implements a dynamic ramp amplitude adjustment mechanism where the ramp amplitude is varied based on the operating duty cycle. A duty cycle detector monitors the switching duty cycle and controls a variable ramp amplitude generator to adjust the ramp signal strength in real-time, enabling the system to adapt between stability and transient response requirements under different operating conditions
Solution Approach 2:
The patent changes the ramp signal parameter (amplitude) as a function of the duty cycle. When the duty cycle exceeds a predetermined threshold, the ramp amplitude is increased to enhance stability; when the duty cycle is below the threshold, the ramp amplitude is reduced to improve transient response. This parameter variation resolves the contradiction by making the ramp signal adaptive rather than fixed
2Reliability
If a large ramp signal is used to improve stability, then sub-harmonic oscillation is reduced, but transient response performance deteriorates
Solution Approach 1:
The system dynamically adjusts the ramp signal amplitude based on real-time duty cycle detection. The variable ramp amplitude generator modifies the ramp signal strength according to the detected duty cycle, allowing the system to use large ramp signals only when necessary for stability while maintaining small ramp signals during transient conditions for optimal response performance
3Ease of operation
If the constant on-time control scheme is employed to achieve fast transient response, then simplicity is improved, but stability deteriorates due to sub-harmonic oscillation
Solution Approach 1:
The patent maintains the simplicity of the constant on-time control scheme by adding only a duty cycle detector and a variable ramp amplitude generator. The dynamic adjustment of ramp amplitude provides the necessary stability improvement without fundamentally changing the simple control architecture, thus preserving ease of operation while enhancing reliability
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 adjustable ramp control scheme improves the stability and transient response of power converters by maintaining a consistent ramp amplitude across varying operating conditions, reducing sub-harmonic oscillations and ensuring stable output voltage under different loads.
Implementation Method 1
a voltage ramp generated by charging a ramp capacitor with a constant current source
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, a control apparatus comprising a feedback control apparatus and an ramp generator, wherein the ramp generator is configured to dynamically adjust an amplitude of a ramp based upon different operating conditions, an on-time control generator and a latch having a set input configured to receive an output signal of the control apparatus and a reset input configured to receive an output signal of the on-time control generator.