Patent Application
20090261740
The present invention relates to an LED driver structure, wherein a transformer unit cooperates with a push-pull driving circuit to generate driving power to drive an LED group.
LED (Light Emitting Diode) has advantages of small size, long lifetime, low power consumption, and high light efficiency. With the development of various colors of LEDs, LED has extensively replaced traditional light sources and has been widely used in many illumination and display applications. Therefore, many semiconductor manufacturers pay their attention to the development of LED. Similar to a general diode, LED also has forward bias and reverse bias in electric operation. In forward bias, current can easily pass through LED; in reverse bias, almost none current pass through LED. Only forward bias can make LED emit light. Thus, only the positive semi-period of alternating current can drive LED to work. However, LED has a smaller reverse breakdown voltage than general diodes, and the negative semi-period of alternating current can easily puncture LED and may externally damage LED. Therefore, LED needs a special driving circuit, preferably a constant-current driving circuit. Taiwan patent No. M298538 disclosed a “Control Device for LED Vehicle Light”, which comprises: a boost rectifier circuit, a driving IC and a plurality of LED lights. The driving IC controls the boost rectifier circuit and determines the current passing through LED lights. In the prior art, the LED lights are cascaded in the same direction, and the driving IC provides pulse signals to control the boost rectifier circuit to perform a switching type boosting, wherein the current is fluctuating and has a higher point and a lower point. Before reaching the higher point, the current has a stage unable to turn on LED. Further, the driving IC needs a circuit providing a constant voltage. Besides, the driving IC raises the cost of the LED light system. Therefore, the prior art is expensive but has an imperfect performance. Taiwan patent No. 1273536 disclosed a “Light Source Circuit, Transformer Circuit, Light-Emitting Panel and Current Balance Method”, wherein several sets of balancing transformers provide several balanced AC powers, and full-wave rectifier circuits transform the AC powers into fluctuating DC powers driving several sets of LED strings. However, the prior art has the disadvantages of non-constant current and high prices because it adopts full-wave rectification and uses at least one transformer. In conclusion, the conventional LED driving circuits still have the problems of non-constant current (fluctuating current) and high prices to overcome.
One objective of the present invention is to provide an LED driving circuit, which achieves a constant-current output and a lower price with fewer elements.
The present invention discloses an LED driver structure, which obtains input power coming from a power source to generate a constant-current power to drive a plurality of LEDs, and which comprises: a plurality of diode groups connected in parallel, a first piezoelectric conversion unit and a second piezoelectric conversion unit respectively arranged at both sides of the diode groups. The first and second piezoelectric conversion units receive the input power and opposite-phase convert the input power into driving powers to drive the diode groups. Among the plurality of diode groups, at least one diode group is formed of a plurality of LEDs. Each of the first and second piezoelectric conversion units has a piezoelectric inverter, which can easily achieve an impedance matching and a constant-current power via a piezoelectric effect to make the LEDs in the diode groups to emit light. The total driving power is the sum of the output powers of the first and second piezoelectric conversion units. The present invention replaces a single large-size and high-price power converter with two lower-price power converters to reduce the costs.
Below, the technical contents of the present invention will be described in detail in cooperation with the drawings.
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Alternatively, the first and second piezoelectric conversion units 2 and 3 may operate in the same timing, and the first and second piezoelectric conversion units 2 and 3 connect with the diode groups 4 in opposite polarities. Thus, the first and second piezoelectric conversion units 2 and 3 drive the diode groups 4 in opposite phases.
The preferred embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Therefore, any equivalent modification or variation according to the spirit of the present invention is to be also included within the scope of the present invention, which is based on the claims stated below.
From the above description, it is proved that the present invention has improvements over the conventional technology, and that the present invention indeed possesses novelty and non-obviousness and meets the conditions for a patent. Thus, the inventor files the application for a patent. It will be appreciated if the application is approved fast.
