Switching Converter Output Sampling for Stable PWM Voltage Control
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Solution Overview
Problem
Switching converters face challenges in maintaining a constant output voltage due to variations in input voltage and power consumption, as the LC-circuit is unable to completely rectify oscillating input voltage, leading to voltage variations within a switching cycle, which can be mitigated by increasing capacitive storage element capacity but at the cost of higher manufacturing costs.
Innovation Solution
A control circuit that generates a pulsewidth modulated drive signal with a duty cycle adjusted based on sampled output voltage feedback, allowing for real-time modification of energy transfer to maintain a constant output voltage, using a sampling signal to determine optimal sampling times within a switching cycle, thereby reducing voltage variations without increasing capacitive storage element capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the capacity of the capacitive storage element is increased to reduce output voltage variation during switching cycle, then the output voltage stability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by determining an optimal sampling time within the switching cycle before the output voltage variation becomes problematic. The control circuit samples the output voltage at this predetermined optimal time point, allowing it to adjust the duty cycle in advance to compensate for upcoming voltage variations, thereby maintaining stability without needing larger capacitive storage elements.
Solution Approach 2:
The patent changes the parameter of sampling time within the switching cycle to optimize voltage regulation. By adjusting when the output voltage is sampled during the switching cycle rather than changing hardware capacity, the system achieves better voltage stability with the same capacitive storage element, avoiding increased manufacturing costs.
2Measurement precision
If the sampling frequency is increased to capture output voltage variations more accurately, then the control precision is improved, but the complexity of the control circuit increases
Solution Approach 1:
The patent determines an optimal sampling time in advance within each switching cycle, eliminating the need for continuous or high-frequency sampling. This preliminary determination of the best sampling moment provides accurate voltage measurement without requiring complex high-frequency sampling circuits, thus improving measurement precision while keeping control circuit complexity manageable.
3Speed
If the duty cycle adjustment response time is reduced to better track output voltage changes, then the voltage regulation speed is improved, but the switching losses increase
Solution Approach 1:
By determining the optimal sampling time in advance within the switching cycle, the control circuit can accurately measure the output voltage at the most informative moment and adjust the duty cycle accordingly. This approach achieves fast voltage regulation response without requiring excessive switching frequency increases, thereby maintaining acceptable switching loss levels while improving voltage regulation speed.
Data Source
AI summary
An apparatus and method of generating a drive signal for a switch in a switching converter having input terminals for applying an input voltage, output terminals for providing an output signal, and at least one inductive storage element coupled to the switch. The method includes sampling the output signal to provide a sampled output signal, and generating a pulsewidth modulated drive signal having a duty cycle that is dependent on the sampled output signal, wherein the output voltage is sampled at sampling times that are dependent on the duty cycle.