An LED array circuit includes a number of series connected LED pairs, each pair including two parallel connected oppositely polarized LEDS. The array is coupled to a standard AC voltage source in series with an inductor L having Q>5 and a reactance which is equivalent to the resistance of a current limiting resistor. The use of an inductor in place of a resistor increases the efficiency of the array to approximately 80%. The efficiency of the array is increased even further by coupling a capacitor parallel to the array and by tuning the inductor and capacitor to the frequency of the AC voltage source. According to one embodiment of the invention, a somg;e retro-fittable unit is provided wherein an inductor, a capacitor, and an array of LEDs are contained in a housing having substantially the same size and shape as a standard incandescent bulb or the lens/filter used in a traffic signal display. According to another embodiment of the invention, a single module is provided with a plurality of LED arrays, with each LED array having its own capacitor coupled in parallel thereto, and its own series coupled switch. The module is coupled to and across the AC voltage source, with one node of the module coupled to the AC voltage source by an inductor.
The analog driver for a display device which is controlled by current, such as an LED, includes a strobed analog input which charges a storage capacitor. The voltage across the storage capacitor is fed to the positive input of a comparator. The negative input of the comparator receives the voltage from a feedback resistor which is in series with the drive voltage, the drive FET (with a gate connected to the output of the comparator) and the light emitting device. Additionally, a reset FET is provided in parallel with the storage capacitor. Displays can be manufactured by a series of panels, each of the panels including an array of these drivers and light emitting devices, along with appropriate control circuitry.
The present invention provides a LED decorative light string that comprises one or more branch circuits, each of said more branch circuits is connected in parallel with each other, and then connected to a common power supply wire for importing operational voltage; each said branch circuit comprises a quantity of light groups, and said quantity of light groups are serially connected in turn; each said light group comprises two or more LEDs, wherein at least one LED is connected in parallel with other LEDs in reverse direction, said other LEDs are connected in parallel in the same direction. The LED decorative light string of the present invention has the advantage of more economical, more reliable in performance, longer life span.
The disclosure concerns a light display panel with a matrix of pixels each comprising three monochrome electroluminescent diodes of three colors. The diodes are controlled by a control circuit delivering electrical power P to each diode, said electrical power being expressed in the form P-k.Pr, wherein Pr is a reference electrical power particular to the diodes of each color and k is a coefficient selected according to the display to be presented. Over the course of time the reference electrical power is subjected to different variations depending on the colors, to compensate for the aging of the diodes.
A cost and space efficient diode circuit arrangement for limiting current from an AC source using only a few components, the circuit includes a capacitor coupled to an AC source and at least two oppositely polarized diodes connected in parallel. This circuit may be used in a variety of applications. For example, the circuit finds particular use in household appliances and electronics, such as vacuum cleaners, where electrical compartment space for light emitting diodes (LEDs) is constrained.
An LED driving circuit that is directly activated by an AC power supply is disclosed. A driving circuit has a first and second pair of opposite branches. The first pair of opposite branches operates in a positive half cycle of the AC power supply and the second pair of branches operates in a negative half cycle of the AC power supply, so the lighting time for each LED is less than a half cycle time, in other words, the time for heat dissipation is prolonged.
