The present application claims priority to Chinese Patent Application No. 201910052814.2, filed Jan. 21, 2019, which is incorporated herein by reference in its entirety.
This disclosure relates to a light string, and more particularly to a parallel circuit for light-emitting diodes.
Certain light strings that include a plurality of light sources directly soldered onto an electric cord at intervals, so as to form a sting-shaped illumination device without a lamp holder, are known in the art. A light string is generally as flexible as the electric cord is, such that the light string is easily arranged in any configuration to comply with requirements for special illumination or decoration.
In a light string, if the light sources are grouped into different groups to be controlled, for example, a group of the light sources flicker while the others remain on, light sources having a control integrated circuit (IC) chip are required, such as a light source having a control chip and an LED packaged together. Furthermore, the drive circuit has to be equipped with an encoding function to send encoding commands to individually switch each of the light sources.
Both the light source having a control IC and the drive circuit equipped with the encoding function are relatively expensive, and the overall cost and the retail price of the light string rises which put the light string at a competitive disadvantage.
In view of the above problems, this disclosure provides a parallel circuit for light-emitting diodes to solve the above-mentioned problem.
The parallel circuit for light-emitting diodes according to this disclosure includes a first power wire, a second power wire, a first light-emitting diode (first LED), a second light-emitting diode (second LED), a switch, and a controller. The first LED has two ends respectively connected to the first power wire and the second power wire. The second LED and the switch are serially connected into a series circuit, and one end of the series circuit is connected to the first power wire, and the other end of the series circuit is connected to the second power wire. The switch changes between a conductive state and a non-conductive state according to a switching frequency. The controller is electrically connected to the first power wire and the second power wire. The controller supplies electric power to the first power wire and the second power wire, to generate a voltage difference between the first power wire and the second power wire.
In one or more embodiments, the controller repeatedly changes the electric power according to a switch cycle, to switch the voltage difference between a high voltage difference and zero voltage difference.
In one or more embodiments, the controller is configured to adjust a length of a half-cycle of the high voltage difference.
In one or more embodiments, the length of a half-cycle of the high voltage difference is larger than or equal to a period of the conductive state of the switch.
In one or more embodiments, a length of a half-cycle of the high voltage difference is smaller than a period of the conductive state of the switch.
In one or more embodiments, the controller is configured to adjust a length of a half-cycle of the high voltage difference.
According to embodiments of this disclosure, a plurality of LEDs are connected in parallel. Only a switch and a controller able to output variable pulse are required to group the LEDs into different groups to be controlled, so as to individually switch each group of the light sources flicker (selectively be powered on and off) or remain on. A complex control signal generator and LEDs having control IC are not required.
The present invention will become more fully understood from the detailed description given herein below for illustration only, and is not intended to limit the present invention, wherein:
Referring to
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In an embodiment, and as explained further below, the switch 150 may have a predetermined or default period of the conductive state, Tc, or first half-cycle of the switch cycle, and may also have a predetermined default period of the non-conductive state, To, or the second half-cycle of the switch cycle. The predetermined default period of the conductive state, Tc, may be a maximum amount of time that the switch will stay in the conductive state for any given switch cycle; the predetermined default period of the non-conductive state, To, may be a maximum amount of time that the switch will stay in the non-conductive state for any given switch cycle. In an embodiment, the predetermined default periods of the conductive and non-conductive states may be equal in duration.
In an embodiment, the switch 150 will be “reset” based on an incoming voltage provided by the controller 160. In one such embodiment, and as explained above switch 150 closes/makes/conducts when an input voltage to switch 150 changes from low voltage, Vo to a high voltage Vh. As long as Vh is maintained, the switch 150 will cycle between conductive and non-conductive states. If the input voltage to the switch 150 is changed to a low voltage, such as Vo, which in an embodiment is zero volts, the switch 150 switches to the non-conductive state. When the input voltage is switched back to a high voltage, such as Vh, the switch 150 is reset and begins to conduct. In one such embodiment, the switch 150 makes on a rising voltage and breaks on a falling voltage. As such, the actual conductive period of time of the conductive state of the switch may be determined by the period of the input voltage signal or the predetermined conductive period of the switch as further explained below, whichever is less.
An example of the switch 150 is a control chip, which in an embodiment, is packaged with the second LED 140 to form a single light emitting component. In another embodiment, switch 150 is not packaged with the second LED, but rather, the series circuit comprises two electrically-connected chips, one for the switch 150 and one for the second LED 140.
In
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In an embodiment, the controller 160 outputs DC power so as to maintain the voltage difference Vd at a fixed value. When the voltage difference Vd is generated, each of the first LEDs 130 remains on, while the second LED 140 flickers, i.e., is turned on and off, according to the switching frequency of the switch 150. In an embodiment, the switching frequency fs of the switch 150 is 1 Hz, such that the second LED 140 flickers by alternately turning on for 0.5 second and turning off for 0.5 second. This switching frequency of 1 Hz is much lower than the sampling rate of the human eye such that the human eye can observe the second LED 140 flickering. At this timing, it appears that among a plurality of LEDs one LED, LED 140, flickers, while the other LEDs, LEDs 130, remain on.
As depicted in
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Providing that the switching frequency and the high voltage difference Vh are fixed, the length of the half cycle of the high voltage difference Vh takes a dominant role of the equivalent luminance of an LED. The equivalent luminance rises when the half cycle of the high voltage difference Vh becomes longer, and the equivalent luminance lowers when the half cycle of the high voltage difference Vh becomes shorter. Therefore, providing that the switching frequency and the high voltage difference Vh are fixed, changing the length of the half cycle of the high voltage difference Vh by time can have the LEDs to adjust LED brightness or light output.
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According to embodiments of this disclosure, a plurality of LEDs are connected in parallel. Only a switch 150 in each circuit, and a controller 160 able to output variable pulse are required to group the LEDs into different groups to be controlled, so as to individually switch each group of the light sources to flicker or remain on. A complex control signal generator and LEDs having control ICs are not required.
The embodiments above are intended to be illustrative and not limiting. Additional embodiments are within the claims. In addition, although aspects of the present invention have been described with reference to particular embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention, as defined by the claims.
Persons of ordinary skill in the relevant arts will recognize that the invention may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the invention may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the invention may comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art.
For purposes of interpreting the claims for the present invention, it is expressly intended that the provisions of Section 112, sixth paragraph of 35 U.S.C. are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.
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