Inverter Soft Start Circuit for EEFL Lighting Reliability
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Solution Overview
Problem
External electrode fluorescent lamps (EEFL) are difficult to light compared to other fluorescent lamps, requiring repeated starting operations and external circuits, leading to increased circuit size and cost.
Innovation Solution
A control circuit for an inverter that includes a soft start circuit generating a time-changing voltage, a pulse modulator for feedback-controlled pulse signal generation, and a logical control unit for transformer primary coil switching, eliminating the need for external striking circuits by performing controlled striking operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated starting operations are performed to light the EEFL, then lighting reliability is improved, but device complexity increases due to requiring external circuits
Solution Approach 1:
The patent merges the striking operation functionality into the inverter control circuit itself. The control circuit performs both the normal inversion function and the striking function (repeated starting operations) without requiring separate external striking circuits. This integration eliminates the need for additional external components while maintaining the ability to perform repeated starting operations to ensure EEFL lighting reliability.
Solution Approach 2:
The inverter control circuit is designed to perform multiple functions: it serves as both the normal inversion controller and the striking circuit. The control circuit can operate in different modes (normal operation mode and striking mode) to handle both regular inverter control and the special repeated starting operations needed for EEFL lighting, thereby eliminating the need for dedicated external striking circuits.
2Reliability
If external circuits are added for repeated starting operations, then lighting reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines the striking operation functionality into the inverter control circuit itself. The control circuit performs both the normal inversion function and the striking function (repeated starting operations) without requiring separate external striking circuits. This integration eliminates the need for additional external components while maintaining the ability to perform repeated starting operations to ensure EEFL lighting reliability.
3Reliability
If external striking circuits are used, then EEFL lighting is ensured, but circuit area increases
Solution Approach 1:
The patent merges the striking operation functionality into the inverter control circuit itself. The control circuit performs both the normal inversion function and the striking function (repeated starting operations) without requiring separate external striking circuits. This integration eliminates the need for additional external components while maintaining the ability to perform repeated starting operations to ensure EEFL lighting reliability.
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 reliable lighting of EEFL with a reduced circuit area and lower costs by integrating the striking functionality within the inverter control circuit, allowing for adjustable striking operations based on lighting probability.
Implementation Method 1
a transformer (12) having a primary coil (12a) and a secondary coil (12b)
Data Source
AI summary
A soft start circuit generates a soft start voltage Vss which changes with time at a starting time of lighting an EEFL. A pulse width modulator generates a PWM signal Vpwm whose duty ratio is feedback-controlled so that a feedback voltage Vfb corresponding to an output voltage Vdrv of an inverter conforms to the soft start voltage Vss. A logical control unit performs switching control of a voltage of a primary coil of a transformer on the basis of the PWM signal Vpwm from the pulse width modulator. The soft start circuit executes at least one striking operation in which the soft start voltage Vss is raised with time, lowered when being reached to a first voltage level VH, and raised again when being lowered to a second voltage level VL lower than the first voltage level VH.