This patent application is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "In the current state of the art of LED dimmer technology, one of the ways to control multiple banks of LEDs is the use of a series dimmer control. For purposes of the invention a 'bank' is defined as a series connection of one or more LEDs. This control works by turning on the LEDs during only a portion of the time at the beginning or end of the positive and negative input sine wave of the AC power source. The control involves various types of semiconductors to implement this switching, but when multiple banks are dimmed, all of the banks dim together, at the same time.
"An alternate way of dimming multiple LED banks is to use a Pulse Width Modulated (PWM) control signal going to the driver circuitry. Typically, in the industry, a zero to ten volt pulse signal is applied to the dimming switching device. The wider the pulse that controls the switching device to conduct current to the LED banks, the brighter the LED banks appear. All LED banks behave in unison.
"In the first mentioned approach, utilizing a series dimmer circuit, there is the problem of noticeable brightness and visible lamp flicker, especially when there is a dimmer setting for very dim lighting. In addition, if there is minor perturbation of the voltage level, there is a very discernible short term brightening or dimming of the LEDs. This happens to all of the banks simultaneously, since the dimmer circuitry's control setting affects all of the banks at the same time."
In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventors' summary information for this patent application: "An exemplary LED driver that sequentially illuminates and dims multiple banks is presented as the invention described herein. The invention has the compatibility of working within pre-existing older installations with conventional, old-style phase dimmer controllers that effect the dimmer operation by switching on to conduct current through the LED bank based on the setting of said controller and the instantaneous phase angle of the AC input voltage. As the multiple LED banks are controlled from almost fully dimmed to fully bright settings, at first one bank of LEDs turns on, then the next bank turns on and eventually all banks turn on. As the banks are dimmed each bank is selectively dimmed as described below.
"If the implementation of this invention using PWM control is used, as the control response from maximum dimmed to maximum brightness is affected, sequentially, first one bank, then two etc., turn on and brighten until all banks are fully illuminated at maximum brightness. Using the PWM control, since dimming operation is proportional to the pulse width of the control signal, magnification of dimming effects, due to input line voltage variations does not occur, since the proportion of dimming switching is fixed based on the PWM signal, rather than being based on the voltage relating to a particular phase angle. When input AC voltage is reduced due to AC supply voltage variations, there is a phase angle shift that yields a magnification of dimming effects, which results in accentuated dimming proportional to the voltage variation, due to a narrowing of the semiconductor switch's conduction on-time, but not the magnified effect caused by the addition of phase angle shift due to input voltage variations.
BRIEF DESCRIPTION OF THE DRAWINGS
"The above and other aspects, features and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings which:
"FIG. 1 is a block diagram of the driver implementation when used in conjunction with an external dimmer.
"FIG. 2 is a block diagram of the driver implementation when used in conjunction with a PWM control input.
"FIG. 3 is a typical circuit implantation of a two bank driver.
"FIG. 4 is a typical circuit implementation of a 4-bank configuration with a PWM control input.
"FIG. 5 illustrates signal waveforms with the circuitry to be implemented using a conventional external dimmer control.
"FIG. 6 illustrates signal waveforms with the circuitry configured using external PWM control input.
"FIG. 7 illustrates a detailed circuit of a single driver bank.
"FIG. 8 shows detailed circuitry for a dual driver bank. The critical differences between the two banks are encircled to show the difference between the two banks.
"FIG. 9 shows a voltage divider network in accordance with the invention."
URL and more information on this patent application, see: Tetik, Attila; Visconti, Peter J. Flicker-Free Lamp Dimming-Driver Circuit for Sequential Led Bank Control. Filed
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