LED Driver Power Stage Mode Segmentation for Dimmer Compatibility
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Solution Overview
Problem
Existing LED driver solutions for offline applications face challenges in achieving high efficiency, long lifetime, low cost, and compatibility with phase-cut dimmers, often compromising on power factor, flicker, and component count.
Innovation Solution
A driver device with a power stage that operates in two modes, simulating a constant load like incandescent lamps in one mode and a high-ohmic or open load in another, using a single capacitor for energy storage to deliver power during the second mode, allowing compatibility with a wide range of dimmers and minimizing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single power converting stage with boost converter operating in discontinuous conduction mode is used to achieve high power factor, then power factor is improved, but device complexity increases and component count increases
Solution Approach 1:
The power conversion process is segmented into two distinct operational modes: a first mode where the power stage converts input power at high power factor, and a second mode where the power stage is disconnected and the load is supplied from energy storage. This segmentation allows the system to achieve high power factor during active conversion while simplifying the overall device structure by using a single power stage rather than multiple complex stages.
Solution Approach 2:
The power stage operates periodically by alternating between the first mode (active power conversion) and the second mode (disconnected state with energy storage supply). This periodic operation enables the system to maintain high power factor during the active mode while reducing device complexity through the simplified single-stage architecture during the disconnected mode.
2Use of energy by moving object
If two series connected power stages are employed to obtain high power factor while keeping output power constant, then power factor is improved, but device complexity and component count increase
Solution Approach 1:
The invention extracts the energy storage function into a separate component (energy storage device) that operates independently during the second mode. This allows the power stage to be simplified to a single stage that only needs to handle power conversion during the first mode, rather than requiring two series connected power stages to simultaneously handle both power factor correction and energy storage functions.
Solution Approach 2:
The system dynamically switches between two operational modes: in the first mode, the power stage operates actively to convert input power with high power factor; in the second mode, the power stage is disconnected and the energy storage device supplies the load. This dynamic operation allows a single power stage to replace what would otherwise require two series connected stages, reducing device complexity while maintaining high power factor performance.
3Adaptability or versatility
If bleeder circuits are used to provide holding currents for thyristors or triacs in dimmers, then dimmer compatibility is improved, but energy losses increase
Solution Approach 1:
The energy storage device acts as an intermediary between the power stage and the load during the second mode. It provides the necessary holding currents for dimmer thyristors or triacs without requiring continuous power conversion, thereby eliminating the need for energy-dissipating bleeder circuits while maintaining dimmer compatibility.
Solution Approach 2:
The energy storage device serves itself by being charged during the first mode and then autonomously supplying the load during the second mode. This self-service mechanism provides the holding currents needed for dimmer compatibility without requiring additional energy-dissipating components like bleeder circuits, thus reducing energy losses.
4Adaptability or versatility
If the power stage runs in off-state to form a high-ohmic load for dimmer compatibility, then dimmer compatibility is improved, but energy storage requirements increase
Solution Approach 1:
The energy storage device is charged in advance during the first mode before the power stage disconnects for the second mode. This preliminary charging action ensures that sufficient energy is stored to supply the load during the off-state period, enabling dimmer compatibility without requiring excessively large energy storage capacity.
Solution Approach 2:
The system maintains continuous useful action by ensuring that the energy storage device is continuously recharged during the first mode to compensate for the energy discharged during the second mode. This continuous cycle allows the power stage to operate in off-state for dimmer compatibility while keeping energy storage requirements at practical levels through sustained charging-d discharging operations.
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 ensures high efficiency, long lifetime, and low cost while maintaining compatibility with phase-cut dimmers, reducing flicker, and minimizing energy storage requirements, thus addressing the limitations of existing solutions.
Implementation Method 1
an energy storage unit, preferably a single capacitor (also called bus capacitor), is used and designed to deliver energy to the load for N-1 half-cycles of the supply voltage and thereby being discharged from a first upper threshold to a second lower threshold
Data Source
AI summary
The present invention relates to a driver device and a corresponding driving method for driving a load (22), in particular an LED unit, said driver device comprising power input terminals (51, 52) for receiving a periodic supply voltage from an external power supply potentially including a dimmer for dimming said periodic supply voltage,power output terminals (53, 54) for providing a drive voltage and/or drive current for driving a load (22), a power stage (70a, 70b, 70c, 70d) coupled between the power input terminals and the power output terminals for controlling an input current received from said power input terminals to draw a high power from said external power supply in a first mode or to draw a low or no power from said external power supply in a second mode, said high power being higher than the power required for driving said load and said low power being lower than the power required for driving said load, wherein said power stage controls said input current to be in the second mode only for a percentage of half cycle periods of a number of subsequent half cycle periods of said supply voltage, and for providing said drive voltage and/or drive current to said power output terminals in said first mode, and an energy storage unit (90) coupled to said power stage for storing electrical energy provided at said power input terminals in said first mode and for providing stored electrical energy to said load via said power output terminals in said second mode.