The patent's assignee for patent number 8807795 is
News editors obtained the following quote from the background information supplied by the inventors: "The present invention is related to an LED lighting device, and more particularly to a lighting device which needs to comply with the safety standards of minimum creepage distances.
"Currently, for achieving the requirements of energy saving and environmental protection, the manufactures and the research & development unit of the lighting devices are gradually adopting LEDs as the light source of lighting devices. LED is a solid-state semiconductor device that can convert electrical energy directly into light. The LEDs have the advantages of small volume, fast response speed, low power consuming, and low pollution.
"However, the lighting devices belong to electronic products. Safety standards are required to be considerate to ensure that personal safety wouldn't be endangered and property and environment wouldn't be harmed in use. For the safety standards of LEDs, different countries enacted different standards for different working voltages.
"In order to solve the above mentioned problems, most of designers may drive LEDs in parallel, so that the working voltages of the whole system can be lower than Safety Extra Low Voltage (SELV). The SELV means that a voltage between conductors or between any conductor and earth does not exceed the standard voltage. No values of creepage distance are specified for working voltages below SELV. Therefore, when the working voltage of a lighting device is below SELV, the creepage distance is not needed to be considered. Moreover, different countries may have different standards for the SELV. However, because the internal resistances of each LED are different, parallel connection may cause a problem of uneven electric current, which may affect the lighting uniformity of the lighting devices and lower the life span of the LEDs. In addition, in order to solve the problem of uneven electric current for each LED, an additional current control IC is used for controlling the electric current of each LED by the manufactures. Nevertheless, as the demand for wattage is increased, the number of LED is increased; therefore, the number of ICs is increased as well as manufacturing costs, so that it is not a perfect way to solve the problem.
"Therefore, how to improve the structure of lighting device so that the lighting device can meet the standard requirements for creepage distances without increasing manufacturing costs is the problem to be solved."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "It is an object of the present invention to provide an LED lighting device, in which an insulation sheet is disposed between a substrate and a base, such that the shortest distance between edges of the substrate and the base measured along the surface of the insulation sheet can meet the creepage distance standards without additional manufacturing costs.
"Another object of the present invention is to provide an LED lighting device, in which an insulation sheet is disposed between a substrate and a base, the insulation sheet can further have thermal conduction and conducts the heat from the substrate to the base made of metal, so as to achieve a heat dissipating effect.
"To achieve the above-mentioned objects, the present invention discloses an LED lighting device, and the LED lighting device at least comprises: a base made of metal; at least one substrate disposed on a surface of the base, the substrate having at least one electrode and at least one LED chip electrically connected with the electrode; and at least one insulation sheet disposed between the base and the substrate, the insulation sheet and the substrate satisfying the correlations L2+2.times.T.gtoreq.L1+2.times.Cr, W2+2.times.T.gtoreq.W1+2.times.Cr and Cr.gtoreq.1.6 mm; wherein Cr is the shortest distance between edges of the substrate and the base measured along the surface of the insulation sheet, L1 is the length of the substrate, L2 is the length of the insulation sheet, W1 is the width of the substrate, W2 is the width of the insulation sheet, and T is the thickness of the insulation sheet.
"In one embodiment of the present invention, the base is a case, and the base further includes a plurality of heat dissipation fins.
"In one embodiment of the present invention, the LED lighting device comprises a plurality of substrates and a plurality of insulation sheets, and each insulation sheet is provided for a plurality of substrates to be disposed thereon.
"In one embodiment of the present invention, the thickness of the insulation sheet is greater than or equal to 0.4 mm; the insulation sheet further includes a function of thermal conduction, and the thermal conductivity of the insulation sheet is greater than or equal to 1 W/m-K.
"By disposing an insulation sheet between a substrate and a base, the shortest distance between edges of the substrate and the base measured along the surface of the insulation sheet can meet the creepage distance standards, so as to avoid hazards caused by a lighting device which does not comply with the safety standards. In addition, the cost of the insulation sheet is low, such that the lighting device can comply with the creepage distance standards with a little cost. Besides, if the insulation sheet has thermal conduction, heat can be conducted from the substrate to the base made of metal, so as to achieve a heat dissipating effect. Preferably, the thermal conductivity of the insulation sheet is greater than or equal to 1 W/m-K, and the thickness of the insulation sheet is greater than or equal to 0.4 mm; when the thermal conductivity of the insulation sheet is less then 1 W/m-K, the insulation sheet has poor thermal conduction and unable to conduct heat to the base effectively, such that the temperature of the LED may easily beyond the working temperature, which may lower the brightness and reduce the life span of the LED. When the thickness of the insulation sheet is less than 0.4 mm, the distance through insulation will be insufficient, such that the insulation reliability will be lower and can't meet the insulation requirement, which leads to a downgrade of safety for the lighting device."
For additional information on this patent, see: Hsu, Hui-Ju; Liu, Hong-Ping; Ho, Yen-Wei. LED Lighting Device. U.S. Patent Number 8807795, filed
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