LED Driver With Isolated Bias Voltage Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LED driver circuits face issues with electromagnetic interference (EMI) and safety concerns due to non-isolated dimming control circuits, which can lead to increased EMI levels and safety hazards when occupancy sensors are used, particularly because the bias power for dimming controllers is not galvanically isolated from the input power source.
Innovation Solution
The proposed LED driver circuit includes a galvanically isolated bias voltage generating circuit that uses a tertiary winding coupled through mutual inductance to generate a bias voltage for the dimming control circuit, ensuring that the bias power is isolated from both the primary and secondary sides of the driver, thereby reducing EMI and enhancing safety by providing a galvanically isolated power source for the dimming controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If non-isolated dimming control circuits are used to power LED drivers, then device complexity is reduced, but electromagnetic interference increases and safety concerns arise
Solution Approach 1:
The patent segments the power supply system into isolated primary and secondary sides using a transformer. The dimming control circuit and its bias power supply are placed on the secondary side, galvanically isolated from the primary power input. This segmentation reduces EMI by preventing noise coupling between high-power switching circuits and sensitive control circuits.
Solution Approach 2:
The patent introduces a transformer as an intermediary component between the primary power input and the secondary side control circuits. The transformer provides galvanic isolation while transferring power and control signals, acting as a mediator that blocks EMI propagation while maintaining system functionality.
2Ease of manufacture
If non-isolated bias power supply is used for dimming control, then manufacturing cost is reduced, but safety hazards increase
Solution Approach 1:
The bias power supply for the dimming control circuit is segmented into an isolated secondary side configuration. By using the transformer's secondary winding to generate bias power, the system achieves safety isolation without requiring separate isolated power supplies, balancing manufacturing cost with safety requirements.
3Object-affected harmful factors
If galvanically isolated bias voltage generating circuit is implemented, then electromagnetic interference is reduced, but device complexity increases
Solution Approach 1:
The patent merges the bias voltage generation function with the main power transformation function by using the transformer for both purposes. The same transformer that provides power isolation also generates bias voltage for the control circuit through its secondary winding, eliminating the need for separate isolation circuits and reducing overall device complexity.
Solution Approach 2:
The transformer is designed with multi-functionality, serving both as the main power isolation element and as the bias voltage generator for the dimming control circuit. This universal component approach reduces the total number of components needed while achieving EMI reduction through galvanic isolation.
4Reliability
If isolated control circuits are used, then safety is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple functions into the transformer component, which provides both power isolation for safety and bias voltage generation for the control circuit. This merging approach achieves safety isolation without requiring additional expensive isolated power supply components, thereby controlling manufacturing costs.
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
The solution effectively reduces electromagnetic interference and improves safety by isolating the dimming control circuit from the input power source, meeting regulatory standards and preventing unwanted current flow, thus ensuring reliable and safe operation of LED lighting systems.
Implementation Method 1
the bias voltage generating circuit may include a tertiary winding coupled to the primary and secondary windings through mutual inductance
Implementation Method 2
a bias capacitor coupled to a cathode of the diode
Implementation Method 3
The dimming control circuit may include an opto-coupler that galvanically isolates the dimming control signal from the voltage converter circuit
Data Source
AI summary
A light emitting diode (LED) driver circuit that generates current for driving an LED load includes a voltage converter circuit configured to supply a drive current to the LED load in response to a control signal, a control circuit that generates the control signal, and a bias voltage generating circuit that generates the bias voltage for the control circuit. The bias voltage generating circuit is galvanically isolated from a power supply voltage and from the LED load. The voltage converter circuit regulates a level of the drive current supplied to the LED load in response to the control signal.