Solid State Lighting Driver with Mixed Power Switch Control
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Solution Overview
Problem
Existing phase-cut dimmers are ineffective for controlling the illumination of Solid State Lighting (SSL) devices like LEDs and OLEDs due to their small loads and nonlinear behavior, leading to limited dimming range and increased costs with additional circuits causing power losses.
Innovation Solution
A driver circuit with a control unit that operates a transistor in two modes: a switched-mode power converter for dimming and a linear mode to determine the phase-cut angle, allowing for reliable phase detection and efficient control of SSL devices using a single power switch, reducing the number of control pins and minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase-cut dimmers are used to control SSL devices, then dimming functionality is achieved, but the dimming range is limited and additional circuits are required
Solution Approach 1:
The patent combines the phase detection function and power conversion function into a single power switch (transistor). The transistor operates in two modes: detecting the phase-cut angle by monitoring voltage across it, and converting power to drive the SSL device. This merging eliminates the need for separate phase detection circuits and reduces the overall circuit complexity while maintaining full dimming functionality.
Solution Approach 2:
The single power switch serves multiple functions: it acts as the primary power conversion element, a phase detection sensor, and a control element for dimming. By making the transistor multi-functional, the patent reduces the number of components needed and simplifies the circuit architecture while achieving both phase-cut dimming and power conversion.
2Adaptability or versatility
If additional circuits are added to enable dimming control, then dimming range is improved, but power losses increase
Solution Approach 1:
By merging phase detection and power conversion into a single transistor, the patent eliminates additional circuits that would otherwise cause power losses. The same transistor used for efficient power conversion also performs phase detection, avoiding the need for separate sensing circuits that would draw additional power and reduce overall efficiency.
3Measurement precision
If multiple power switches are used for control, then control precision is improved, but the number of control pins increases
Solution Approach 1:
The patent merges the phase detection function into the control of a single power switch. The microcontroller controls one transistor and determines the phase-cut angle by monitoring the voltage across that same transistor during its off-state. This approach achieves precise phase detection with minimal control pins, as no separate phase detection switch or additional sensing elements are required.
4Adaptability or versatility
If phase-cut dimmers are used with SSL devices, then compatibility with existing dimmers is achieved, but reliable phase determination is difficult due to small loads and nonlinear behavior
Solution Approach 1:
The patent uses the power switch itself to detect the phase-cut angle. By monitoring the voltage across the transistor during its off-state, the system self-determines the phase information directly from its own operation. This self-service approach ensures reliable phase detection even with small SSL loads and nonlinear behavior, as the detection is based on the actual switching operation rather than external sensing that might be affected by load characteristics.
Data Source
AI summary
In order to control of dimming of solid state lighting devices (SSL) a driver circuit drives the SSL subject to an input voltage using a phase-cut dimmer. The driver circuit comprises a transistor operable in two modes, either alternating between on/off states or continuously controlling a current through the transistor. A power converter network provides a switched-mode power converter in conjunction with the transistor when operated in the first mode generating a drive voltage for the SSL. The control unit controls the transistor to selectively operate in one of the two modes; to control the transistor to determine that the input voltage exceeds an input voltage threshold; and to control a drive current through the SSL based on a measurement of a phase-cut angle thereby controlling an illumination level of the SSL device.