Semiconductor Light Source Driving Apparatus Open Fault Management
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Solution Overview
Problem
Existing semiconductor light source driving apparatuses face challenges in efficiently managing open faults in serially-connected light emitting diodes, leading to increased isolation voltage requirements and unwanted power consumption when one or more diodes are disconnected.
Innovation Solution
The apparatus includes a constant voltage diode for voltage suppression with low continuous allowable power dissipation connected between the endmost semiconductor light source elements, a current control element controlled by PWM, and a controller that detects open faults and diverts current to maintain illumination of unaffected light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant voltage diode with high breakdown voltage is used to suppress voltage across open-faulted light source modules, then voltage suppression effectiveness is improved, but power dissipation and cost increase
Solution Approach 1:
The patent changes the parameter of breakdown voltage from high to low, using a constant voltage diode with breakdown voltage lower than the sum of forward voltages of serially-connected light emitting diodes. This allows the diode to conduct and limit voltage across open-faulted modules without requiring high breakdown voltage, thereby reducing power dissipation and cost while maintaining adequate voltage suppression effectiveness.
2Ease of operation
If current continues to flow through open-faulted light source modules, then simplicity of operation is maintained, but power consumption increases
Solution Approach 1:
The patent introduces a constant voltage diode as an intermediary component connected in parallel with each light source module. When an open fault occurs, the diode conducts and provides a current path through the diode instead of through the open-faulted module, effectively diverting current while maintaining continuous operation of other modules without requiring complex control systems.
3Reliability
If high breakdown voltage diodes are used for voltage suppression, then voltage clamping capability is improved, but device cost increases
Solution Approach 1:
The patent changes the parameter of breakdown voltage from high to low, using a constant voltage diode with breakdown voltage lower than the sum of forward voltages of serially-connected light emitting diodes. This allows the use of lower-cost diodes with lower breakdown voltages that are sufficient for the application, thereby reducing device cost while maintaining adequate voltage clamping capability to protect switching elements.
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
This configuration allows for the use of low-cost, low-power diodes and minimizes power dissipation during open faults, ensuring that unaffected light sources remain lit with reduced power consumption.
Implementation Method 1
a first constant-voltage diode; a series circuit of a first current detection element and a second constant-voltage diode with a lower breakdown voltage than the first constant-voltage diode
Implementation Method 2
a current control element controlled by pulse-width modulation (PWM) using a PWM signal supplied to an end of the current control element
Implementation Method 3
a second current detection element for detecting current flowing through the light source modules; a controller for controlling a switching element, the current control element, and the DC power supply based on a detection output of the second current detection element
Data Source
AI summary
The semiconductor light source driving apparatus includes light source modules, a current control element, a second current detection element, a DC power supply, and a controller. The light source modules each include the following components connected in parallel: a semiconductor light source; a first constant-voltage diode; a series circuit of a first current detection element and a second constant-voltage diode with a lower breakdown voltage than the first constant-voltage diode; and a switching element. The controller controls the DC power supply based on a detection output of the second current detection element. After the first current detection element generates a output in response to an open fault in any of the semiconductor light sources, and then the current control element is turned off, the controller turns on the switching element of the light source module with the open fault, thereby allowing the current control element to be controlled.