Primary Side LED Driver Control Circuit
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Solution Overview
Problem
Conventional constant current generators for LED lighting, which use optical couplers and sensing circuits, face issues with stability, reliability, and efficiency due to degradation, increased space requirements, and power loss, failing to meet needs for smaller size, higher efficiency, and energy savings.
Innovation Solution
A controlling circuit and method that employs direct sampling of the primary side of a transformer to simplify the circuit structure and improve efficiency, eliminating the need for an optical coupler and secondary side feedback, using a flyback topology with a sampling circuit, on time sensing circuit, regulating signal generator, and PWM controller to maintain a constant output current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional constant current generators use optical couplers and sensing circuits, then output regulation is achieved, but device complexity and space occupation increase
Solution Approach 1:
The patent extracts and eliminates the optical coupler and secondary side sensing circuit from the conventional constant current generator. By using primary side only control with current sampling through a sensing resistor and flyback topology, the invention removes these problematic components while maintaining output regulation functionality through alternative control mechanisms.
Solution Approach 2:
The invention enables the primary side circuit to self-regulate the output current without external feedback from the secondary side. The controlling circuit uses the transformer's flyback characteristics and primary side current sampling to automatically maintain constant output current, making the system self-sufficient and eliminating the need for optical couplers.
2Reliability
If optical couplers are used in constant current generators, then output regulation is maintained, but component deterioration occurs over time
Solution Approach 1:
The patent removes the optical coupler from the circuit entirely, eliminating the component that deteriorates over time. The primary side only control architecture achieves output regulation without this aging-prone component, thereby extending the operational life of the constant current generator.
Solution Approach 2:
The invention replaces the expensive and aging-prone optical coupler with simple, robust components like sensing resistors and standard semiconductor devices that have longer operational lifetimes and do not suffer from the same deterioration mechanisms.
3Reliability
If sensing circuits are used for output regulation, then current control is achieved, but power loss increases
Solution Approach 1:
The primary side sensing circuit uses the existing current path through the switching device and transformer primary winding to generate sensing voltage, eliminating the need for additional power-consuming sensing circuits on the secondary side. The system leverages its own operational parameters for regulation.
Solution Approach 2:
The invention replaces the conventional secondary side voltage sensing and optical feedback mechanism with primary side current sampling. This substitution reduces power loss by using direct current measurement through low-value sensing resistors rather than maintaining power-intensive optical coupling and secondary side regulation circuits.
4Reliability
If multiple devices are used in conventional constant current generators, then regulation function is achieved, but cost increases
Solution Approach 1:
The patent eliminates the optical coupler and secondary side sensing circuit, reducing the total component count. This extraction of unnecessary components directly lowers material costs, assembly complexity, and manufacturing expenses while preserving the essential current regulation function through primary side control.
Solution Approach 2:
The invention merges the regulation function into the primary side controlling circuit, combining multiple functions (current sensing, regulation control, and output management) into a single integrated architecture. This consolidation reduces the number of discrete devices needed and lowers overall manufacturing cost.
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 increases stability and operating life, reduces space and costs, and enhances reliability and efficiency by eliminating the optical coupler and secondary side sensing circuit, resulting in a more compact, cost-effective, and high-efficiency LED driver.
Implementation Method 1
a transformer, an output diode arranged at a secondary side of the transformer, and a switching device arranged at a primary side of the transformer to form a flyback topology
Implementation Method 2
sampling current flowing through a primary side of a transformer of the LED driver by a sensing resistor arranged in series with a switching device at the primary side of the LED driver, and generating a sensing voltage signal in response thereto
Implementation Method 3
a light-emitting diode (LED) driver
Data Source
AI summary
The present invention relates to a controlling circuit and controlling method for an LED driver implemented as a flyback topology. The controlling circuit may be at a primary side of a transformer of the LED driver, and include a sampling circuit, an on time sensing circuit of an output diode, a regulating signal generator, and a PWM controller. The sampling circuit may generate a sampling signal indicating output current by sampling at the primary transformer side. The on time sensing circuit can detect an on time of the output diode. The regulating signal generator can generate a regulating signal by regulating the sampling signal, a voltage reference, and the on time of the output diode. The PWM controller may generate a controlling signal to control operation of a switching device of the LED driver to maintain a substantially constant output current in accordance with the regulating signal.