Comparator Propagation Delay Compensation in DC-DC Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
DC to DC power converters used in LED lighting systems face challenges in accurately controlling the on/off cycles of main transistors due to signal propagation delays and DC offsets, leading to inconsistent average current delivery to LEDs.
Innovation Solution
A comparator system is developed that compensates for propagation delays and DC offsets by sampling differential voltages across its inputs during on cycles and adjusting its output in subsequent cycles, ensuring precise control of the main transistor's on/off times through a sample and hold circuit and error controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a comparator is used to control the on/off cycles of the main transistor, then the switching control function is achieved, but propagation delays and DC offsets cause inaccurate timing and inconsistent average current delivery
Solution Approach 1:
The patent applies preliminary action by measuring the differential voltage at the comparator inputs before the switching decision is made. The sample and hold circuit captures the differential voltage at the moment the comparator output transitions, storing this value for compensation in the next cycle. This preliminary measurement allows the system to anticipate and correct for propagation delays and DC offsets before they affect the timing accuracy, thereby resolving the contradiction between achieving switching control and maintaining timing precision.
2Measurement precision
If propagation delay compensation is implemented through sampling and holding differential voltage, then timing accuracy is improved, but device complexity increases due to additional circuits
Solution Approach 1:
The patent merges multiple functions into the comparator circuit itself. The differential voltage sampling is performed using the inherent capacitance at the comparator inputs, and the sample and hold circuit reuses the comparator's internal nodes and switching mechanisms. This merging approach allows the system to achieve propagation delay compensation without adding completely separate compensation circuits, thereby improving timing accuracy while limiting the increase in device complexity.
Data Source
AI summary
Operating DC to DC power converters. At least some of the example embodiments are methods including: driving current through an inductance in a first on cycle of the power converter; comparing, by a comparator, a signal indicative of current through the inductance coupled to a first input of the comparator to a threshold applied to a second input of the comparator, and asserting a comparator output responsive to the signal indicative of current meeting the threshold; sampling a differential voltage across the first and second inputs, the sampling responsive to assertion of a comparator output, and the differential voltage indicative of propagation delay through the comparator; and compensating the comparator in a second on cycle for the compensation delay based on the differential voltage, the second on cycle subsequent to the first on cycle.