LED Constant-Current Converter Control Without Voltage Sampling
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Solution Overview
Problem
Existing constant-current switch-mode power converters for LED lighting face challenges in achieving high-precision constant-current control, particularly at low brightness levels where errors in voltage sampling can significantly impact performance.
Innovation Solution
The proposed solution involves a controller for a constant-current switch-mode power converter that includes a constant-current controller and a driver. The constant-current controller generates a modulation signal based on the input voltage, and the driver outputs a drive signal to a transistor coupled to an inductive coil and a resistor. The controller uses a reference voltage generator to produce a reference voltage equal to the input voltage multiplied by the ratio of on-time to the sum of on-time and demagnetization period, enabling accurate constant current control without relying on voltage sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage sampling is used for current control in conventional power converters, then the control circuit can be simplified, but measurement precision deteriorates at low brightness levels due to sampling errors
Solution Approach 1:
The patent replaces the voltage sampling method (electrical measurement approach) with a timing-based measurement method. Instead of sampling voltage to determine current, the system measures the time duration of the demagnetization process, which directly correlates with the current magnitude. This substitution eliminates sampling errors and achieves high-precision current control without complex analog-to-digital conversion circuits.
Solution Approach 2:
The patent changes the measurement parameter from voltage (analog quantity prone to sampling errors) to time (digital quantity with high precision). By measuring the demagnetization time period and using it to control the switching duty cycle, the system achieves accurate current regulation. The reference voltage is dynamically adjusted based on the measured time parameter, creating a precise feedback mechanism that eliminates the need for traditional voltage sampling.
2Ease of operation
If traditional voltage sampling control is used, then the control method is simple, but control precision worsens due to errors in voltage sampling particularly at low brightness
Solution Approach 1:
The patent substitutes the voltage sampling control method with a time-based control method. The control precision is improved by measuring the demagnetization time period and using this time parameter to directly control the switching duty cycle. This eliminates the accumulation of errors from voltage sampling and analog-to-digital conversion, achieving high-precision constant current control while maintaining operational simplicity through digital timing measurements.
3Device complexity
If voltage sampling is employed for current regulation, then the control circuit design is easier, but reliability deteriorates due to error accumulation in sampling processes
Solution Approach 1:
The patent replaces the voltage sampling control system with a time-based control system. By measuring the demagnetization time period and using it to control the switching duty cycle, the system eliminates error accumulation inherent in voltage sampling and analog-to-digital conversion. This substitution significantly improves reliability and control accuracy, especially at low brightness levels where sampling errors would normally accumulate.
Solution Approach 2:
The patent implements a precise feedback mechanism where the measured demagnetization time period is used to dynamically adjust the reference voltage and control the switching duty cycle. This closed-loop feedback based on time measurement rather than voltage sampling eliminates error accumulation and ensures high reliability in current regulation across all brightness levels.
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 improves the accuracy of constant current control, particularly at low brightness levels, by eliminating errors associated with voltage sampling and ensuring precise regulation of the output current.
Implementation Method 1
the off-time includes a demagnetization period during which the inductive coil undergoes a demagnetization process
Data Source
AI summary
Controller and method for a constant-current switch-mode power converter. For example, a controller for a constant-current switch-mode power converter includes: a constant-current controller configured to receive an input voltage and generate a modulation signal based at least in part on the input voltage; and a driver configured to receive the modulation signal, generate a drive signal based at least in part on the modulation signal, and output the drive signal to a transistor coupled to an inductive coil and a resistor; wherein: the drive signal corresponds to at least one switching cycle; the switching cycle includes an on-time during which the drive signal is at a first logic level and an off-time during which the drive signal is at a second logic level; and the off-time includes a demagnetization period during which the inductive coil undergoes a demagnetization process.