SSL Thermal Control Using PTC Thermistor Integration
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Solution Overview
Problem
Conventional solid-state lights (SSLs) face challenges with heat management, as existing passive temperature control systems have slow response times and inefficient heat dissipation, leading to uneven temperature distribution among multiple SSEs, which can result in premature degradation and color shift.
Innovation Solution
Integrating a positive temperature coefficient (PTC) thermistor directly with the light emitting structure, allowing for conductive heat transfer and rapid resistance increase at high temperatures to limit current and reduce heat generation, while maintaining optimal operating temperatures for each SSE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a laterally positioned PTC thermistor is used to control temperature, then the SSL package can limit heat generation, but the response time is slow due to thermal lag
Solution Approach 1:
The patent merges the PTC thermistor with the SSE by positioning it in direct thermal contact with the SSE, eliminating the need for separate thermal coupling components. This integration enables immediate thermal coupling and rapid response to temperature changes, resolving the contradiction between temperature control capability and slow response time.
Solution Approach 2:
The patent introduces a thermally conductive material as an intermediary between the PTC thermistor and the SSE to enhance thermal coupling. This mediator ensures efficient heat transfer from the SSE to the PTC thermistor, enabling fast response times while maintaining effective temperature control.
2Device complexity
If a single PTC thermistor controls multiple SSEs, then device complexity is reduced, but individual SSEs cannot operate at optimal temperatures
Solution Approach 1:
The patent segments the temperature control system by providing an individual PTC thermistor for each SSE. This segmentation allows each SSE to be independently controlled and maintained at its optimal operating temperature, resolving the contradiction between simplified device complexity and uniform temperature control across multiple SSEs.
3Temperature
If heat is drawn away from SSEs using passive heat sinks, then heat management is improved, but adequate heat removal may not be achieved
Solution Approach 1:
Instead of passively drawing heat away from the SSEs using heat sinks, the patent inverts the approach by using PTC thermistors that actively limit heat generation at the source. When the SSEs reach a certain temperature, the PTC thermistors increase their resistance, reducing the current and thereby limiting further heat generation. This active limitation approach ensures adequate heat management where passive dissipation fails.
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 solution provides faster response times and more efficient heat management, ensuring consistent light output and extended lifespan by maintaining each SSE at optimal temperatures, reducing overheating risks, and optimizing light output per unit area.
Implementation Method 1
provide an active temperature control system having a temperature sensor located in the SSL and a feedback controller that modulates the drive current to the SSE based on the signals from the temperature sensor
Implementation Method 2
depositing a converter material (e.g., phosphor) on the SSE. For example, FIG. 1A shows a conventional SSL 10 that includes a support 2, an SSE 4 attached to the support 2, and a converter material 6 on the SSE 4. The SSE 4 can include one or more light emitting components. The SSE 4 typically emits blue light that stimulates the converter material 6 to emit light at a desired frequency (e.g., yellow light).
Data Source
AI summary
A solid state light (“SSL”), a solid state emitter (“SSE”), and methods of manufacturing SSLs and SSEs. In one embodiment, an SSL comprises a packaging substrate having an electrical contact and a light emitting structure having a front side and a back side. The back side of the light emitting structure is superimposed with the electrical contact of the packaging substrate. The SSL can further include a temperature control element aligned with the light emitting structure and the electrical contact of the packaging substrate.