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Researchers Submit Patent Application, "Led Driving Apparatus Having Holding Current Circuit and Operating Method Thereof", for Approval

May 14, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Cheng, Chung-Tai (Zhubei City, TW); Lin, Chia-Hsiu (Hsinchu City, TW), filed on October 14, 2013, was made available online on May 1, 2014.

The patent's assignee is Raydium Semiconductor Corporation.

News editors obtained the following quote from the background information supplied by the inventors: "The invention relates to the driving of a light-emitting diode (LED); in particular, to a LED driving apparatus having a holding current circuit and operating method thereof.

"Please refer to FIG. 1 and FIG. 2. FIG. 1 illustrates a schematic diagram of a conventional tri-electrode AC switch (TRIAC) circuit; FIG. 2 illustrates a schematic diagram of the tri-electrode AC switch circuit of FIG. 1 being applied in a lighting circuit. As shown in FIG. 1 and FIG. 2, the tri-electrode AC switch TRIAC is a gate-controlled switch and it is also called 'bidirectional triode thyristor' and can be conducted in both the forward voltage and the reverse voltage. When the tri-electrode AC switch circuit 1 is applied in a lighting product, the tri-electrode AC switch circuit 1 can adjust the lightness of the lighting product by changing the resistance of the variable resistor R1. When the AC voltage passes through the tri-electrode AC switch circuit 1, the tri-electrode AC switch circuit 1 changes the resistance of the variable resistor R1 to adjust the voltage conduction angle to change the lightness of the lighting product correspondingly.

"However, as to current LED products, if the tri-electrode AC switch circuit 1 is added as shown in FIG. 2, because the tri-electrode AC switch circuit 1 is unstable under low-voltage and low-current condition, the input voltage V.sub.IN will be also unstable at low-voltage conduction angle, and different voltage forms VS1 and VS2 will be formed as shown in FIG. 3B. If the input voltage V.sub.IN is zero at low-voltage conduction angle, the LED apparatus 24 will even flicker.

"One solution is to add a holding current circuit 20 in the lighting circuit 2. FIG. 4 shows an embodiment of a conventional holding current circuit 20. As shown in FIG. 4, a resistor R.sub.H is disposed between the input voltage V.sub.IN and the regulator REG, and the gate of the transistor MOS is coupled between the resistor R.sub.H and the regulator REG. The regulator REG will generate a voltage V.sub.F, and the voltage at the setting resistor R.sub.SET will approach the voltage V.sub.F, therefore, a current can be formed by adjusting the resistance of the setting resistor R.sub.SET. This current can be used as the holding current in the lighting circuit 2 to make the input voltage V.sub.IN stable at low-voltage conduction angle, and the same voltage forms VS1' and VS2' will be formed as shown in FIG. 3C.

"However, the conventional holding current circuit 20 applied in the lighting circuit 2 having the tri-electrode AC switch TRIAC will also cause serious problems of high power consumption and over-heat of the light product since the higher the voltage, the larger the power consumption. In addition, because the current and the voltage of the current source circuit 22 disposed under the LED apparatus 24 will become larger, the power consumption P of the current source circuit 22 will be excessive (as shown in FIG. 5B); therefore, the over-heat problem is needed to the overcome.

"Therefore, the invention provides a LED driving apparatus having a holding current circuit and operating method thereof to solve the above-mentioned problems occurred in the prior arts."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "An embodiment of the invention is a LED driving apparatus having a holding current circuit. In this embodiment, the holding current circuit of the LED driving apparatus includes an input terminal, a holding resistor, a regulator, a first resistor, a second resistor, a setup resistor, a control unit, and a transistor. The holding resistor and the regulator, the first resistor and the second resistor, and the transistor and the setup resistor are coupled between the input terminal and ground terminal respectively.

"The control unit is coupled to the transistor, between the holding resistor and the regulator, and between the first resistor and the second resistor respectively. The control unit receives a first voltage between the holding resistor and the regulator and a second voltage between the first resistor and the second resistor and outputs a control signal to selectively control the transistor off.

"Another embodiment of the invention is a method of operating a LED driving apparatus having a holding current circuit. In this embodiment, the holding current circuit includes an input terminal, a holding resistor, a regulator, a first resistor, a second resistor, a setup resistor, a control unit, and a transistor. The holding resistor and the regulator are coupled in series between the input terminal and a ground terminal. The first resistor and the second resistor are coupled in series between the input terminal and the ground terminal. The transistor and the setup resistor are coupled in series between the input terminal and the ground terminal. The control unit is coupled to the transistor, between the holding resistor and the holding resistor, and between the first resistor and the second resistor respectively.

"The method includes steps of: (a) the control unit receiving a first voltage between the holding resistor and the regulator and a second voltage between the first resistor and the second resistor and outputting a control signal; and (b) selectively switching off the transistor according to the control signal.

"Compared to the prior art, the LED driving apparatus having the holding current circuit and operating method thereof disclosed by the invention can achieve following effects of: (1) maintaining the input voltage V.sub.IN stable at low-voltage conduction angle to prevent the flickering of the LED apparatus; (2) effectively solving the problems of high power consumption and over-heat when the input voltage V.sub.IN is excessive in prior arts.

"The advantage and spirit of the invention may be understood by the following detailed descriptions together with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

"So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

"FIG. 1 illustrates a schematic diagram of a conventional tri-electrode AC switch (TRIAC) circuit.

"FIG. 2 illustrates a schematic diagram of the tri-electrode AC switch circuit of FIG. 1 being applied in a lighting circuit.

"FIG. 3A illustrates a wave-form diagram of the input voltage; FIG. 3B illustrates a wave-form diagram of the unstable voltage caused by the TRIAC circuit; FIG. 3C illustrates a wave-form diagram of the stable voltage maintained by the holding current circuit.

"FIG. 4 illustrates an embodiment of the conventional holding current circuit.

"FIG. 5A illustrates a wave-form diagram of the input voltage; FIG. 5B illustrates a schematic diagram of the excessive power consumption when the conventional holding current circuit is used.

"FIG. 6 illustrates a schematic diagram of the holding current circuit of the LED driving apparatus in an embodiment of the invention.

"FIG. 7 illustrates a schematic diagram of the reduced power consumption when the holding current circuit of the invention is used.

"FIG. 8 illustrates a schematic diagram of the holding current circuit of the LED driving apparatus in another embodiment of the invention.

"FIG. 9 illustrates a schematic diagram of the holding current circuit of the LED driving apparatus in another embodiment of the invention.

"FIG. 10 illustrates a flow chart of the method of operating the holding current circuit of the LED driving apparatus in another embodiment of the invention."

For additional information on this patent application, see: Cheng, Chung-Tai; Lin, Chia-Hsiu. Led Driving Apparatus Having Holding Current Circuit and Operating Method Thereof. Filed October 14, 2013 and posted May 1, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4636&p=93&f=G&l=50&d=PG01&S1=20140424.PD.&OS=PD/20140424&RS=PD/20140424

Keywords for this news article include: Electronics, Raydium Semiconductor Corporation.

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Source: Electronics Newsweekly