Patent Application
20100052573
The present invention relates to a regulation circuit and method for electronic devices and particularly to an LED (light emitting diode) regulation circuit and method.
LED provides many advantages over conventional lighting features such as a higher efficiency, longer life span and less likely to be damaged, thus is widely used in people's daily life nowadays. However, due to the LED is driven by a front end DC power supply to generate light and the DC power supply outputs a high current in a constant current mode as shown in
In order to disperse the heat of the LED when in use, the general approach is mounting an LED chip set onto a metal seat. The metal seat is connected to a radiation metal blade to disperse heat. However, when the LED is in a high current duty condition, heat dissipation efficiency often is not desirable and results in heat accumulation and forming hot spots. This could cause burned down of the LED. A conventional technique to attack this problem is installing radiation fins and even an air fan outside an LED module to provide more cooling power. As the power of LED increases constantly in recent years, the size of composite products also increases. The conventional technique mentioned above becomes a constraint to LED product design and production process. Improvements are needed to resolve those problems.
The primary object of the present invention is to reduce heat generated by LEDs during operation to prevent excessive heat accumulation resulting in decreasing of life span and brightness, and also reduce installation of cooling elements to simplify total structure of the LEDs.
To achieve the foregoing object, the invention provides an LED regulation circuit which includes a voltage transformation unit to receive DC power and provide a constant current to drive at least one LED and a pulse-width modulation unit to generate a driving signal to control the voltage transformation unit. The driving signal has an operation period. In the operation period, the driving signal drives the voltage transformation unit to output regular operation power. The pulse-width modulation unit also is connected to a timing regulation unit which generates a regulation signal sent to the pulse-width modulation unit to regulate the driving signal by adding a sleep period in the operation period. In the sleep period, the driving signal lowers the power of the voltage transformation unit that drives the LED. Through alternately switching of the operation period and sleep period of the driving signal, heat accumulation of the LED can be prevented during continuous operation.
In one aspect, the sleep period is less than 1/16 second. The voltage transformation unit is electrically connected to a rectification filter circuit. The rectification filter circuit includes a rectification unit and a filter unit. The rectification filter circuit receives AC power from an AC power source and transforms to DC power output to the voltage transformation unit. The driving signal generated by the pulse-width modulation unit is a pulse-width modulation signal. The voltage transformation unit outputs non-zero current power. The timing regulation circuit and pulse-width modulation unit are bridged by a coupler unit. The timing regulation unit further has a comparator and a clock generator. The comparator gets a standard signal from the regulation circuit and a clock signal from the clock generator, and determines generation of the regulation signal according to output frequency of the clock signal.
Furthermore, the invention provides a regulation method of the aforesaid regulation circuit adaptable to DC power driving circuits. The method includes procedures as follow:
a. output a driving signal with an operation period to a voltage transformation unit;
b. drive the voltage transformation unit to provide a regular operation current to at least one LED;
c. regulate the operation period of the driving signal by adding a sleep period; and
d. lower the regular operation current of the LED driven by the voltage transformation unit according to the driving signal in the sleep period to prevent heat accumulation of the LED during continuous operation.
In one aspect, another step of determining to add a sleep period interval frequency is included. The sleep period is less than 1/16 second. The power output by the voltage transformation unit has non-zero current.
In another aspect, in the LED regulation circuit and method set forth above, the driving power output from the voltage transformation unit to the LED can be changed according to the operation period and sleep period of the driving signal output from the pulse-width modulation unit to prevent the LED at the rear end from continuously receiving the regular driving power and accumulating heat and resulting in damage and a shorter life span of the LED. Thus cooling of the LED can be effectively accomplished without installing radiation elements. And production and assembly of the LED devices can be done easier and more efficiently.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Please refer to
Refer to
The invention further provides a regulation method adaptable to the aforesaid regulation circuit. Refer to
a. output a driving signal with an operation period to a voltage transformation unit (S10);
b. drive the voltage transformation unit to provide a regular operation current to at least one LED (S20);
c. regulate the operation period of the driving signal by adding a sleep period (S30); and
d. lower the regular operation current of the LED driven by the voltage transformation unit according to the driving signal in the sleep period to prevent heat accumulation of the LED during continuous operation (S40).
The procedures set forth above further include a step of determining to add a sleep period interval frequency. At this step, the interval of the sleep period can be determined through a clock signal output by a selected frequency. In general, the sleep period is less than 1/16 second to prevent flickering of the LED. The voltage transformation unit outputs power with non-zero current.
Refer to
As a conclusion, the LED regulation circuit and method of the invention adding the sleep period in the operation period of the driving signal to shorten DC power supplying time of the voltage transformation unit received from the rectification filter circuit. Thus the driving power provided by the voltage transformation unit to the rear end LED is altered, and the LED goes through the idle period at a lower current without continuously receiving the driving power at a higher current. Therefore, heat accumulation that might otherwise occur by continuous operation of the LED can be prevented and life span of the LED increases. Moreover, the regulation circuit and method of the invention need less conventional radiation elements to perform cooling. Production of the LED devices can be done easier and more efficiently. It offers a great improvement over the conventional techniques.
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
