Synchronous Isolated LED Converter Timing for Accurate Voltage Sensing
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Solution Overview
Problem
Synchronous LED converter topologies face disturbances in voltage sensing signals due to concurrent current drive and voltage sensing, leading to incorrect feedback in closed-loop control, which existing hardware optimizations cannot adequately address.
Innovation Solution
A synchronous isolated LED converter design that includes a main transformer with an auxiliary winding for voltage sensing, a controller that samples the voltage sensing signal asynchronously with respect to drive current pulses, and uses an approach of similar triangles to estimate zero-crossing times, offsetting the sampling period with a delay term to avoid noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If voltage sensing is performed concurrently with current drive, then the voltage sensing signal can be acquired in real-time, but the pulsed drive current disturbs the voltage sensing signal and imprints itself on the sensing signal
Solution Approach 1:
The controller samples the voltage sensing signal periodically at zero-crossing moments of the output-side current, synchronizing the sampling action with the periodic nature of the converter operation. This periodic sampling at specific timing moments avoids the disturbance periods while maintaining real-time monitoring capability.
Solution Approach 2:
The controller estimates the zero-crossing time of the output-side current in advance using the approach of similar triangles based on waveform characteristics, and offsets the sampling period with a delay term before the actual zero-crossing occurs. This preliminary timing adjustment ensures sampling happens at the optimal moment before drive current pulses can imprint on the sensing signal.
2Measurement precision
If hardware design optimizations are attempted to avoid disturbances, then measurement accuracy may be improved, but device complexity increases and satisfactory improvements are not achieved
Solution Approach 1:
The patent replaces potential hardware-based disturbance filtering mechanisms with a software/control-based timing solution. Instead of adding complex analog filtering circuits or isolation hardware, the controller uses digital timing control to sample the voltage sensing signal at optimal moments, achieving high measurement precision without increasing hardware complexity.
Solution Approach 2:
The controller dynamically adjusts the sampling timing parameter by offsetting the sampling period with a delay term based on the estimated zero-crossing time. This parameter change in the sampling strategy allows the system to avoid disturbance periods while maintaining simple hardware architecture.
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 ensures accurate voltage sensing and measurement, achieving specified LED voltage measurement accuracy in a cost-efficient manner, improving the reliability of closed-loop control in LED converters, power supplies, and luminaires.
Implementation Method 1
The main transformer is configured to transform electric power from an input-side electric potential of the converter to an output-side electric potential of the converter
Implementation Method 2
The ancillary transformer is connected to the controller and configured to transform the drive current from the input-side electric potential to the output-side electric potential
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Disclosed is a synchronous isolated LED converter (1). The converter (1) comprises a main transformer (111, 112, 113), a voltage sensing circuit (14), a controller (16), an ancillary transformer (191, 192), and a switch (20). The main transformer (111, 112, 113) is configured to transform electric power from an input-side electric potential (12) of the converter (1) to an output-side electric potential (13) of the converter (1), and includes an auxiliary winding (113). The voltage sensing circuit (14) is connected to the auxiliary winding (113) and configured to generate a voltage sensing signal (15, VSNS2) in accordance with a voltage across the auxiliary winding (113). The controller (16) is connected to the voltage sensing circuit (14) and configured to provide a drive current (17, ISW2) in accordance with a sampling of the voltage sensing signal (15, VSNS2). The sampled voltage sensing signal (15, VSNS2) is indicative of an output voltage (18, VLED) of the converter (1), and the drive current (17, ISW2) is associated with the input-side electric potential (12). The ancillary transformer (191, 192) is connected to the controller (16) and configured to transform the drive current (17, ISW2) from the input-side electric potential (12) to the output-side electric potential (13). The switch (20) is operable in accordance with the transformed drive current (17, ISW2). The controller (16) is further configured to sample the voltage sensing signal (15, VSNS2) in accordance with a zero-crossing of an output-side current (I2) of the converter (1), yet asynchronously with respect to pulse edges of the drive current (17, ISW2). This avoids an incorrect voltage sensing in a cost-efficient manner.