Light Source Device Open-Circuit Failure Protection
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Solution Overview
Problem
In light source devices with solid-state light sources, when one light emitting device fails open-circuit, it causes all connected devices to stop functioning, leading to deterioration due to repeated rush currents during PWM driving, especially with existing solutions like Zener diodes and self-on devices that generate heat and induce voltage drops.
Innovation Solution
A light source device with a series-connected open-circuit failure detection and maintenance system that short-circuits the failed device using an FET, reducing heat generation and preventing repeated rush currents by maintaining the circuit state during failures, allowing for continuous operation of other devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is connected in parallel to light emitting devices to protect against open-circuit failure, then the light emitting devices can continue to operate when one fails, but heat radiation becomes necessary due to heat generation by the Zener diode
Solution Approach 1:
The patent changes the operating parameters by using an FET instead of a Zener diode. The FET has different electrical characteristics with lower power dissipation, transforming the protection mechanism from high-heat to low-heat operation while maintaining the failover functionality.
Solution Approach 2:
The patent substitutes the Zener diode protection mechanism with an FET-based protection mechanism. This replacement eliminates the need for heat radiation structures while maintaining the ability to maintain continuous operation when a light emitting device fails open-circuit.
2Temperature
If a self-on device such as a thyristor or triac is connected in parallel instead of a Zener diode, then heat generation is reduced, but a sudden drop of voltage across terminals occurs causing large rush current to flow
Solution Approach 1:
The patent changes the electrical parameters by using an FET with controlled gate voltage instead of a self-on device. The FET can be precisely controlled to turn on at specific voltage thresholds, preventing the sudden voltage drop and associated rush current while maintaining low heat generation.
3Object-affected harmful factors
If a short-circuit protection device is used with self-on devices, then protection against rush current is provided, but the device returns to OFF state after stopping and causes repeated rush current during PWM driving
Solution Approach 1:
The patent implements a dynamic protection mechanism where the FET remains in a maintained ON state after detecting open-circuit failure. This dynamic state change prevents the protection device from repeatedly turning OFF and ON during PWM dimming operations, eliminating repeated rush current while continuing to protect the circuit.
Solution Approach 2:
The patent performs preliminary action by detecting open-circuit failure and turning on the FET before PWM dimming operations begin. The maintained ON state ensures that when PWM driving pulses are applied, the protection is already in place and will not cause repeated rush current.
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 the deterioration of light emitting devices by preventing repeated rush currents and eliminating the need for heat radiation structures, ensuring stable operation even when one device fails.
Implementation Method 1
the short-circuiting section includes an FET, a drain of which is connected to one end of the light emitting device and a source of which is connected to the other end of the light emitting device, and the short-circuiting section short-circuits both the ends of the light emitting device by changing the drain and the source of the FET to a conduction state
Data Source
AI summary
A light source device includes a plurality of light emitting devices connected in series, an open-circuit failure detecting section, a failure detection and maintenance section, and a short-circuiting section connected in parallel to at least one light emitting device among the plurality of light emitting devices. The open-circuit failure detecting section detects an open-circuit failure of the light emitting device connected in parallel. The failure detection and maintenance section shifts to, when the open-circuit failure detecting section detects the open-circuit failure, a circuit state during the open-circuit failure and maintains the circuit state to which the failure detection and maintenance section shifts. The short-circuiting section short-circuits, when the failure detection and maintenance section maintains the circuit state during the open-circuit failure, both ends of the light emitting device in which the open-circuit failure is detected.