Abstract: An apparatus for driving LEDs using high voltage includes a plurality of LEDs divided into a plurality of LED segments connected in series with a switching voltage detector and a current limiting device. Each of the plurality of LED segments is connected in parallel with a switching device. A high input voltage supplies power to the apparatus. The switching voltage detector generates a first mode change signal when the input voltage increases and a second mode change signal when the input voltage decreases. A switch controller receives the two mode change signals and generates a plurality of switching control signals to respectively control the switching devices of the plurality of LED segments.

Abstract: An LED-based lighting apparatus includes a plurality of LED-based lighting segments connected in series with a current control device. Each lighting segment has at least one LED-based lighting unit connected in series. A plurality of switch controllers controlled by a switching voltage comparator unit is connected with the plurality of LED-based lighting segments to provide multiple operation modes for turning on different number of LED-based lighting segments. In one embodiment, each switch controller is connected in parallel with a corresponding segment. The switching voltage comparator unit generates a propagation signal that propagates through and controls the plurality of switch controllers. In the other embodiment, each switch controller is connected between a positive end of the corresponding segment and a current control device. The switching voltage comparator unit generates two propagation signals that propagate through and control the plurality of switch controllers.

Abstract: An LED-based lighting apparatus is powered by multi-phase AC voltages to reduce flicker. A multi-phase AC-to-AC power generator is used to generate a plurality of AC voltages from an AC power source. The plurality of AC voltages each having a different phase are rectified by a plurality of rectifiers to provide a plurality of rectified AC voltages for a plurality of LED lighting units. Each LED lighting unit has voltage dependent brightness and reaches maximum brightness at different time due to the phase difference in the rectified AC voltage. The peak-to-peak variation in the total brightness is reduced and therefore the LED-based lighting apparatus has low flicker.

Abstract: An apparatus for driving LEDs using high voltage includes a plurality of LEDs divided into a plurality of LED segments connected in series and a plurality of three-terminal voltage controlled current limiting devices. Each of the current limiting devices is associated with one of the LED segments and has a first terminal connected to a negative end of the associated LED segment, a second terminal applied with a bias voltage and a third terminal connected to a common node. A current source is connected between the common node and ground. A power-loss reduction circuit having a plurality of LEDs controlled by an LED controlling circuit may further be inserted between the common node and the current source to reduce the power loss in the current source because of the high voltage at the common node.

Abstract: An apparatus for driving LEDs using high voltage includes a plurality of LEDs divided into a plurality of LED segments connected in series and a plurality of three-terminal voltage controlled current limiting devices. Each of the current limiting devices is associated with one of the LED segments and has a first terminal connected to a negative end of the associated LED segment, a second terminal applied with a bias voltage and a third terminal connected to a common node. A current source is connected between the common node and ground. A power-loss reduction circuit having a plurality of LEDs controlled by an LED controlling circuit may further be inserted between the common node and the current source to reduce the power loss in the current source because of the high voltage at the common node.

Abstract: A plurality of LED-based lighting units is segmented into a plurality of LED-based lighting segments connected in series. Each lighting segment has a plurality of LED-based lighting units connected in series with at least a series-connection switch, and a bypass-connection switch is connected in parallel with the series of LED-based lighting units. The total number of LED-based lighting units can be determined by a maximum voltage level of an input voltage supply and the forward voltage of the LED-based lighting unit for achieving optimal efficiency. The number of lighting segments and the number of lighting units in each lighting segment are properly chosen based on the total number of the LED-based lighting units in such away that any number up to the total number of all the LED-based lighting units can be connected in series by respectively controlling the series-connection switch and the bypass-connection switch of each LED-based lighting segment.

Abstract: An apparatus comprises red, green and blue LED strings each having a corresponding switching circuit. Each LED string is divided into a plurality of LED segments. The three LED strings are connected in parallel or in series. Each LED string may be connected in series with a respective current source or share a common current source. A controller controls each switching circuit so that the number of LED segments connected in series in the red, green or blue LED string can be respectively controlled according to a color setting signal and the voltage level of an input voltage. A first control method is provided for controlling the apparatus having a constant input voltage and a second control method is provided for controlling the apparatus having a periodically time-varying input voltage.

Abstract: An apparatus comprises a plurality of controllable LED strings interposed with a plurality of switching units with each switching unit being connected between a leading controllable LED string and a trailing controllable LED string. A controller controls the switching units so that controllable LED strings are connected in a combination of series and parallel connections by connecting two adjacent leading and trailing controllable LED strings in series or parallel or by-passing the leading controllable LED string based on an automatically detected input voltage range. Each controllable LED string includes a plurality of LEDs connected in series between positive and negative ends of the controllable LED string and a plurality of controlling switches each corresponding to an LED. The number of LEDs connected in series in each controllable LED string is further adjusted by the controller as the input voltage varies with time.

Abstract: An LED-based lighting apparatus includes a plurality of LED-based lighting segments connected in series with a current control device. Each lighting segment has at least one LED-based lighting unit connected in series. A plurality of switch controllers controlled by a switching voltage comparator unit is connected with the plurality of LED-based lighting segments to provide multiple operation modes for turning on different number of LED-based lighting segments. In one embodiment, each switch controller is connected in parallel with a corresponding segment. The switching voltage comparator unit generates a propagation signal that propagates through and controls the plurality of switch controllers. In the other embodiment, each switch controller is connected between a positive end of the corresponding segment and a current control device. The switching voltage comparator unit generates two propagation signals that propagate through and control the plurality of switch controllers.

Abstract: A plurality of switching units interleaves with a plurality of LED-based lighting units to configure the interconnection of the LED-based lighting units for providing multiple lighting modes. Each switching unit disposed between a leading lighting unit and a trailing lighting unit is separately controlled by a controller. The switching unit can be configured to connect the two LED-based lighting units in parallel or in series, or to bypass the leading LED-based lighting unit. All the LED-based lighting units are connected in series when an input voltage supply is at a maximum voltage level, and connected in parallel when the input voltage supply is at a minimum voltage level. As the input voltage level decreases, the number of LED-based lighting units connected in parallel increases, and vice versa.

Abstract: A plurality of LED-based lighting units is segmented into a plurality of LED-based lighting segments connected in series. Each lighting segment has a plurality of LED-based lighting units connected in series with at least a series-connection switch, and a bypass-connection switch is connected in parallel with the series of LED-based lighting units. The total number of LED-based lighting units can be determined by a maximum voltage level of an input voltage supply and the forward voltage of the LED-based lighting unit for achieving optimal efficiency. The number of lighting segments and the number of lighting units in each lighting segment are properly chosen based on the total number of the LED-based lighting units in such away that any number up to the total number of all the LED-based lighting units can be connected in series by respectively controlling the series-connection switch and the bypass-connection switch of each LED-based lighting segment.

Abstract: A plurality of switching units interleaves with a plurality of LED-based lighting units to configure the interconnection of the LED-based lighting units for providing multiple lighting modes. Each switching unit disposed between a leading lighting unit and a trailing lighting unit is separately controlled by a controller. The switching unit can be configured to connect the two LED-based lighting units in parallel or in series, or to bypass the leading LED-based lighting unit. All the LED-based lighting units are connected in series when an input voltage supply is at a maximum voltage level, and connected in parallel when the input voltage supply is at a minimum voltage level. As the input voltage level decreases, the number of LED-based lighting units connected in parallel increases, and vice versa.

Abstract: A method in a KVM switch system for interacting with the user to switch computer ports using a touch panel device having a touch-sensitive screen is described. The system allows a user to accomplish port switching by “drawing” a symbol (such as an Arabic number) representing a port number on the touch screen, coupled with other actions, such as one or more touches of the screen, an action using another input device such as a mouse, keyboard, buttons, etc., to confirm the port number input.

Abstract: A method in a KVM switch system for interacting with the user to switch computer ports using a touch panel device having a touch-sensitive screen is described. The system allows a user to accomplish port switching by “drawing” a symbol (such as an Arabic number) representing a port number on the touch screen, coupled with other actions, such as one or more touches of the screen, an action using another input device such as a mouse, keyboard, buttons, etc., to confirm the port number input.

Abstract: A DC-DC converter includes a temperature compensation circuit arranged between a feedback differential amplification circuit and an output voltage detection circuit to compensate the variation of the voltage level of the DC output voltage of the converter caused by ambient temperature changes. The temperature compensation circuit includes a temperature detection circuit that detects the ambient temperature and, in response thereto, generates a temperature signal; and a current source circuit that is connected between a feedback signal input terminal of the feedback differential amplification circuit and the output voltage detection circuit. The current source circuit, based on the temperature signal, generates an electrical current and a compensation voltage proportional to the electrical current. The compensation voltage is applied to the DC output voltage to thereby regulate the voltage level of the DC output voltage.

Abstract: A constant current regulator includes a current sensing circuit loop connected to a switch unit of the constant current regulator to detect a current flowing through the switch unit and to generate a detection current that is in proportion to the current flowing through the switch unit. The detection current flows through a detection resistor to induce a detection voltage. A differential amplifier bases on a set voltage and the received detection voltage to generate an error voltage to a pulse width modulation controller, which in turn causes a gate driver circuit to control the switching operation of the switch unit thereby supplying a constant current to a load connected to an output voltage of the regulator.

Abstract: A constant current regulator includes a current sensing circuit loop connected to a switch unit of the constant current regulator to detect a current flowing through the switch unit and to generate a detection current that is in proportion to the current flowing through the switch unit. The detection current flows through a detection resistor to induce a detection voltage. A differential amplifier bases on a set voltage and the received detection voltage to generate an error voltage to a pulse width modulation controller, which in turn causes a gate driver circuit to control the switching operation of the switch unit thereby supplying a constant current to a load connected to an output voltage of the regulator.

Abstract: A DC-DC converter includes a temperature compensation circuit arranged between a feedback differential amplification circuit and an output voltage detection circuit to compensate the variation of the voltage level of the DC output voltage of the converter caused by ambient temperature changes. The temperature compensation circuit includes a temperature detection circuit that detects the ambient temperature and, in response thereto, generates a temperature signal; and a current source circuit that is connected between a feedback signal input terminal of the feedback differential amplification circuit and the output voltage detection circuit. The current source circuit, based on the temperature signal, generates an electrical current and a compensation voltage proportional to the electrical current. The compensation voltage is applied to the DC output voltage to thereby regulate the voltage level of the DC output voltage.

Abstract: A driving system used for light emitting diodes relating to a controllable driver which can detect the voltage desire from application and adjust driving voltage (Vapp1-Vapp2) automatically in order to reach a steady driving current. Additionally, users can adjust the setting of driving current and the output value of DC voltage source for application with different voltage and current requirements through a control interface. The over-temperature and over-current protections (e.g. cutting off driving current or setting the upper limit of driving current) are also included in the system for prevention of possible harms. In the system, a driving system is also disclosed for integration of all the mentioned functions but no need of massive space and can be used in LED lighting system or LED backlight system for constant power emitting.

Abstract: A constant power DC light emitting diode (LED) driving system and method is disclosed. The system comprises a plurality of LED, a DC voltage source for LED current generation, and a constant-voltage and constant-current regulator for constant luminance control. A method and a redundancy circuit thereof for LED current detouring and LED luminance maintenance are also disclosed.