Buck Converter On-Time Control Circuit Transient Response
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing buck converters with constant on-time mode have limited load transient response due to minimum off-time limitations, which can be improved but at the cost of increased circuit complexity.
Innovation Solution
A buck converter design that incorporates a switching circuit, error amplifier, comparator, on-time control circuit, and driver, utilizing a clock set signal and logic gate to expand on-time duration without adding additional comparators, thereby maintaining better load transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching frequency is increased to improve load transient response, then the response speed improves, but the on-time duration is limited by minimum off-time
Solution Approach 1:
The patent applies preliminary action by pre-charging a capacitor during the off-time period before the switch turns on. This allows the capacitor to store energy in advance, enabling the on-time duration to be extended beyond what would normally be limited by the minimum off-time requirement. The capacitor is charged through a current source during off-time, and this pre-stored charge allows the switch to remain on longer than the minimum off-time would normally permit, thus resolving the contradiction between response speed and on-time duration.
2Duration of action of moving object
If multiple threshold voltages are added to expand on-time duration, then the on-time can be extended, but the circuit complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically varying the threshold voltage level during the switching cycle rather than using multiple fixed threshold voltages. A single comparator adjusts its reference threshold based on the charging state of the capacitor, allowing the on-time duration to be extended without requiring multiple comparators or complex threshold voltage generation circuits. This single-parameter dynamic adjustment resolves the contradiction by achieving extended on-time with minimal additional circuitry.
Solution Approach 2:
The patent applies universality by making a single comparator perform multiple functions: it compares the capacitor voltage against a dynamic threshold, controls the on-time duration, and adapts to different loading conditions. This multi-functional approach eliminates the need for separate circuit elements for each threshold voltage level, thereby extending on-time duration without proportionally increasing circuit complexity.
3Productivity
If the turn-off duration is decreased to maintain duty ratio, then the transient response improves, but the switching frequency becomes limited by minimum off-time
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor during the off-time period, which enables the switch to stay on longer during the next on-time period. This pre-charging action allows the system to maintain better transient response performance without being constrained by minimum off-time limitations, as the capacitor's stored charge sustains the on-state beyond what the minimum off-time would normally allow.
Data Source
AI summary
A buck converter includes a switching circuit, an error amplifier, a comparator, a reset circuit, a logic gate, a flip-flop and a driver. The switching circuit generates an output voltage according to an input voltage. The error amplifier generates a compensation voltage signal according to a feedback voltage signal and the reference voltage signal. The feedback voltage signal is associated with the output voltage. The comparator generates a clock set signal according to the compensation voltage signal and a ramp voltage signal. The reset circuit generates a first reset signal according to an on-time control signal. The logic gate generates a second reset signal according to the clock set signal and the first reset signal. The flip-flop generates the on-time control signal according to the clock set signal and the second reset signal. The driver controls the switching circuit according to the on-time control signal.