Buck Converter Current Regulation Using Switch On-Resistance
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Solution Overview
Problem
Current buck converter systems for LED lighting face challenges in regulating average current and switching frequency, particularly with low inductance coils, varying load conditions, and the need to minimize electromagnetic emissions, while also reducing power losses and eliminating the need for external sensing elements.
Innovation Solution
A system comprising a driver module with a buck converter and a regulating module that senses current during the 'on' time of a switch, adjusts the switch's operating states to maintain a desired average current, and operates independently of coil inductance and input voltage, using a control module to regulate the time periods and adjust the switching frequency based on sensed currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensing elements are used to regulate current, then current regulation accuracy is improved, but device complexity and power losses increase
Solution Approach 1:
The patent extracts the current sensing function from external sensing elements and relocates it to the existing switch component. The switch's inherent on-resistance is utilized as the sensing element, eliminating the need for separate external sensing resistors or devices. This reduces device complexity while maintaining current regulation accuracy through the use of the switch's known resistance characteristics.
Solution Approach 2:
The switch component is given multiple functions: it serves both as the power switching element and as the current sensing element. By utilizing the switch's on-resistance for current measurement, the same component performs dual roles, reducing the total number of components needed in the circuit while maintaining accurate current regulation capability.
2Reliability
If switching frequency is increased to improve current regulation with low inductance coils, then current regulation is improved, but electromagnetic emissions increase
Solution Approach 1:
The patent implements a feedback control mechanism that monitors the actual current through the load and adjusts the switching duty cycle accordingly. By using the switch's on-resistance to sense current and comparing it with the target current value, the system can regulate current accurately without requiring excessively high switching frequencies, thereby reducing electromagnetic emissions while maintaining reliable current regulation.
3Object-affected harmful factors
If switching frequency is adjusted to minimize electromagnetic emissions, then EMC compliance is improved, but current regulation capability deteriorates
Solution Approach 1:
The patent changes the control parameter from fixed-frequency switching to variable duty-cycle switching at a lower frequency. By adjusting the duty cycle based on feedback from current sensing through the switch's on-resistance, the system maintains effective current regulation capability while operating at lower switching frequencies that comply with electromagnetic emission standards.
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 solution enables efficient regulation of average current and frequency, reduces power losses, and eliminates the need for external sensing elements, while maintaining stability and EMC compliance, even with varying load conditions and low inductance coils.
Implementation Method 1
the switch's known on-resistance value to sense current flowing through the switch
Data Source
AI summary
Various embodiments of apparatuses, systems and methods for regulating the currents provided by a DCDC buck converters to an LED unit are provided. In accordance with at least one embodiment, a regulating element operable to instruct and regulate the periods during which a first switch of a driver module, used to control the operation of a buck converter module, is configured into at least one of a first operating state and a second operating state such that the maximum and minimum currents provided by the buck converter module to a load, such as an LED unit, over a given duty cycle are symmetrically disposed about an average current provided to the LED unit during the duty cycle, where the average current provided is substantially equal to a target current for the LED unit.