Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2000-10-02
2001-11-06
Riley, Shawn (Department: 2838)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S307000, C315S246000, C362S800000, C340S907000
Reexamination Certificate
active
06313589
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply circuit for use with, for example, signal lights utilizing LEDs (light-emitting diodes).
2. Description of the Related Art
An attempt has been made to use signal lights utilizing LEDs as traffic lights. LEDs can provide various colors and can be used as excellent light sources for lighting equipment, because LEDs have higher luminous efficiencies than do incandescent lamps and are excellent in terms of energy conservation.
In order to use an LED light source as a light source of a traffic light or ordinary lighting equipment indoor and outdoor, while guaranteeing safety and long service life, the LED light source must be used in consideration of great changes in environmental temperature from winter to summer.
For example, when a signal light utilizing an LED is used at temperatures lower than 0° C. in winter, heat is rapidly generated at a light-emitting portion of the LED when the LED is turned on, with the result that an internal material constituting the LED expands thermally. Since the entire structure of the LED is in a contracted state at such low temperature, the internal expansion generated when the LED is turned on generates mechanical stress within the LED structure.
Accordingly, repeated turning on and off operations create severe operating conditions, possibly resulting in breakage of the LED, depending on the conditions.
Therefore, in order to secure a required quantity of light and mitigate the above-described phenomena, current supplied to the LED must be determined in consideration of the temperature characteristics of the LED such that the current becomes suitable for temperatures encountered during winter.
Further, when an LED is used at high temperature in summer, the following points must be taken into consideration. A manufacturer of LEDs provides various ratings in relation to use of LEDs. According to such ratings, when an LED is used in an environment having a temperature higher than room temperature, the maximum current permitted to be supplied to the LED is lower than that at room temperature.
That is, when during actual use an LED is placed in a high-temperature atmosphere having a temperature higher than about 40° C., the current supplied to the LED must be reduced as compared with that supplied at ordinary temperature, in order to prevent thermal damage such as thermal fusion of an internal material that constitutes the LED.
Therefore, for such high temperature use, the supply current must be determined so as to secure a required quantity of light and not to exceed a rated current specified for high temperatures encountered during summer.
Further, conventional signal lights utilizing an LED have a drawback in that there arises a time delay between supply of power and actual emission of light from the LED.
SUMMARY OF THE INVENTION
In view of the foregoing demands and problems, an object of the present invention is to provide a power supply circuit which is used with signal lights or other lights utilizing an LED and which enables the LED to properly operate in the cold during winter and in the hot during summer and to emit light immediately after being turned on.
To achieve the above object, the present invention provides a power supply circuit comprising: a rectification section for rectifying AC voltage so as to obtain DC voltage; a voltage regulating circuit section for receiving the DC voltage and outputting a constant voltage; a light-emitting diode driven by the voltage output from the voltage regulating circuit section; and an output voltage detection section for detecting ambient temperature and the voltage output from the voltage regulating circuit section and outputting a voltage suitable for the light-emitting diode to operate at the detected ambient temperature, wherein the voltage regulating circuit section compares the voltage output from the output voltage detection section with a reference voltage so as to obtain a control signal; inputs to a transformer current which is switched in accordance with the control signal; and supplies an output from the transformer to the light-emitting diode.
The power supply circuit according to the present invention enables an LED to properly operate in the cold during winter and in the hot during summer and to emit light immediately after being turned on.
REFERENCES:
patent: 5663719 (1997-09-01), Desse et al.
patent: 6150771 (2000-11-01), Perry
Akimoto Noriko
Kobayashi Yasumasa
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Riley Shawn
Tokiwa Dengyo Co., Ltd.
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