Power Converter Control Circuit for Stable Ramp Injection
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Solution Overview
Problem
Hysteretic-based power converters employing constant on-time control schemes face instability issues such as sub-harmonic oscillations, leading to excessive ripple voltage, which can be mitigated by injecting a voltage ramp into the feedback circuit but may cause undesirable effects like input offset in error amplifiers.
Innovation Solution
A control scheme that separates the ramp signal from the feedback signal and injects it into the feedback loop via a summing stage, using conversion units to convert voltage signals into current signals and a comparator to determine the high-side switch's turn-on, thereby improving stability and transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a voltage ramp is injected into the feedback circuit to avoid sub-harmonic oscillation, then stability is improved, but input offset of the error amplifier occurs
Solution Approach 1:
The patent segments the feedback circuit into two separate paths: one for the feedback signal and another for the ramp signal. The feedback signal is applied to the inverting input of the error amplifier, while the ramp signal is injected through a separate summing stage at the non-inverting input. This segmentation prevents the ramp signal from causing input offset at the error amplifier while maintaining stability.
Solution Approach 2:
The patent introduces a summing stage as an intermediary component between the ramp signal source and the error amplifier. This summing stage combines the ramp signal with the feedback signal in a way that prevents direct injection into the error amplifier input, thereby avoiding input offset while still achieving the stabilizing effect of the ramp signal.
2Stability of the object's composition
If a large ramp signal is used to improve stability, then sub-harmonic oscillation is suppressed, but transient response deteriorates
Solution Approach 1:
The patent employs dynamic adjustment of the ramp signal characteristics through the summing stage, which allows the ramp signal to be actively managed rather than being a fixed large signal. The summing stage enables the system to maintain stability while preserving transient response by combining the ramp signal with the feedback signal in a dynamic manner that adapts to operating conditions.
3Stability of the object's composition
If direct injection of ramp signal into the control loop is performed, then stability is improved, but input offset and other undesirable effects occur
Solution Approach 1:
The summing stage serves as an intermediary that prevents direct injection of the ramp signal into the error amplifier. Instead of directly adding the ramp signal to the feedback signal at the error amplifier input, the summing stage combines them in a separate location, eliminating the harmful input offset effect while preserving the stabilizing benefit.
Solution Approach 2:
The patent extracts the ramp signal injection point from the error amplifier input and relocates it to a separate summing stage. This extraction removes the source of input offset and other undesirable effects while maintaining the essential function of ramp signal injection for stability.
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
This approach enhances the performance of power converters by maintaining stable operations and fast transient responses under varying conditions while avoiding direct injection issues, thus reducing sub-harmonic oscillations and improving output voltage stability.
Implementation Method 1
a first conversion unit configured to convert a ramp voltage signal into a ramp current signal flowing through a first resistor
Implementation Method 2
a second conversion unit configured to convert a feedback voltage signal into a feedback current signal flowing through the first resistor
Implementation Method 3
a third conversion unit configured to convert a control voltage signal generated by an error amplifier into a control current signal flowing through a second resistor
Implementation Method 4
a comparator having a first input coupled to the first resistor and a second input coupled to the second resistor, wherein an output of the comparator determines a turn-on of a high-side switch
Data Source
AI summary
An apparatus includes a first conversion unit configured to convert a ramp voltage signal into a ramp current signal flowing through a first resistor, a second conversion unit configured to convert a feedback voltage signal into a feedback current signal flowing through the first resistor, a third conversion unit configured to convert a control voltage signal generated by an error amplifier into a control current signal flowing through a second resistor, and a comparator having a first input coupled to the first resistor and a second input coupled to the second resistor, wherein an output of the comparator determines a turn-on of a high-side switch of a power converter.