摘要:
A system providing deep dimming of a solid state lighting (SSL) load includes a hysteretic down-converter, a shunt switch, a controller and a comparator. The down-converter controls average current value and amplitude of ripple of SSL current using amplitude modulation (AM) dimming control. The shunt switch controls magnitude of the SSL current using pulse width modulation (PWM) dimming control. The controller generates first and second PWM signals for controlling upper and lower current levels at which the down-converter operates based on the SSL current and voltage across the SSL load, and generates a third PWM signal for controlling the shunt switch based on a dimming level load set by a dimmer. The comparator circuit compares first and second analog signals corresponding to the first and second PWM signals with the SSL current, and drives the down-converter in response to the comparison. The SSL current is based on both the AM dimming control and the PWM dimming control.
摘要:
A driver (100; 200) for driving a dimmable load (L) is powered from phase-cut mains (U1) and determines the dimming state of the load on the basis of the phase of the cutting of the mains. The driver comprises: a load current generating device (130; 230) generating load current; a controllable auxiliary load (170; 270) connected to an input (131; 231) of the load current generating device; a control device (140; 240) controlling the auxiliary load. The control device has an input (141; 241) receiving a signal indicating the momentary voltage at the driver input. The load current generating device generates interrupted current pulses, so that the average output current corresponds to the dim command reflected by the phase cutting angle of the input mains. The control device switches the auxiliary load on during those time periods when the output current generated by the load current generating device is zero.
摘要:
A LED light source comprises—a full bridge rectifier equipped with a first input terminal and a second input terminal for coupling to output terminals of the phase cut dimmer, —a series arrangement comprising N LED loads, a first and second end of said series arrangement being coupled to a first output terminal and a second output terminal of the full bridge rectifier respectively, —control means for during a period of the rectified AC supply voltage subsequently making the LED loads comprised in the first series arrangement carry a current, one by one and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude increases and for subsequently making the LED loads stop carrying a current, one by one, and in dependency of the momentary amplitude of the rectified AC supply voltage when the momentary amplitude decreases, said control means controlling the current through the LED loads at zero when the output voltage of the phase cut dimmer equals zero and controlling the current through the LED loads at a value that is independent from the phase angle of the phase cut dimmer when the output voltage of the phase cut dimmer differs from zero Volt. In order to make the LED light source compatible with a phase cut dimmer, the LED light source is further equipped with—a switchable bleeder current source coupled between the first and second output terminal of the full bridge rectifier, —a latch coupled between the first and second output terminals of the full rectifier bridge and comprising a series arrangement of a resistor and a capacitor to prevent the current through the dimmer from crossing zero after a leading edge generated by the phase cut dimmer, in case the phase cut dimmer is a leading edge phase cut dimmer, —a unidirectional element arranged in series with the capacitor for preventing discharging of the capacitor via the LED loads or the adjustable bleeder current source, and—a clamp circuit coupled to the capacitor and comprising a current source for discharging the capacitor and providing a low ohmic path for the dimmer current when the dimmer is off.
摘要:
A light generating device (1) is provided with at least a voltage input (21) adapted for receiving a variable voltage, at least three LED circuits (10), coupled with said voltage input (21), wherein each LED circuit (10) comprises a LED unit (14) and controllable current regulator (15) to control the current through said LED circuit (10). The light generating device (1) further comprises a controllable switch matrix (30) comprising a plurality of switches (25, 26, 27), said switch matrix (30) is configured to operate in at least three different switching modes and a controller (50), connected at least with said switch matrix (30), configured to determine said variable operating voltage and to control the switching mode of said switch matrix (30) in dependence of the determined operating voltage. To provide an efficient operation of such device (1) with a variable operating voltage, such as an AC voltage, in a first switching mode, said LED units (10) are connected parallel to each other, in a second switching mode, at least two of said LED units (10) are connected in series and in a third switching mode, said LED units 10 are connected in series with each other.
摘要:
A LED light source comprises a first rectifier (DB1) having input terminals coupled to an AC voltage source and output terminals connected by a first series arrangement comprising N LED loads and further comprises circuitry (I1, I2, I3, CC) for making the LED loads one by one carry a current when the momentary value of the AC voltage increases and one by one stop carrying a current when the momentary value of the AC voltage decreases. The LED light source also comprises a second rectifier (DB2) having input terminals coupled to the AC voltage source via a reactive element and LED1 LED2 LED3 output terminals connected by a second series arrangement comprising M LED loads and further comprises circuitry (I4) for making the LED loads one by one carry a current when the momentary value of the AC voltage present at the input terminals of the second rectifier increases and one by one stop carrying a current when the momentary value of the AC voltage decreases.
摘要:
There is provided an arrangement for light balancing. The arrangement provides light balancing and robust flux feedback and comprises a light source array, a plurality of light sources arranged as a plurality of strings of individual light emitting diodes, at least one light guide structure, and at least one optical sensor. The arrangement provides feedback relating to the optical contribution for each one of the plurality of strings of individual light emitting diodes and is thereby maintaining the emitted light at a balanced level.
摘要:
A LED light source comprises a first rectifier (DB1) having input terminals coupled to an AC voltage source and output terminals connected by a first series arrangement comprising N LED loads and further comprises circuitry (I1, I2, I3, CC) for making the LED loads one by one carry a current when the momentary value of the AC voltage increases and one by one stop carrying a current when the momentary value of the AC voltage decreases. The LED light source also comprises a second rectifier (DB2) having input terminals coupled to the AC voltage source via a reactive element and output terminals connected by a second series arrangement comprising M LED loads and further comprises circuitry (I4) for making the LED loads one by one carry a current when the momentary value of the AC voltage present at the input terminals of the second rectifier increases and one by one stop carrying a current when the momentary value of the AC voltage decreases.
摘要:
A light generating device (1) is provided with at least a voltage input (21) adapted for receiving a variable voltage, at least three LED circuits (10), coupled with said voltage input (21), wherein each LED circuit (10) comprises a LED unit (14) and controllable current regulator (15) to control the current through said LED circuit (10). The light generating device (1) further comprises a controllable switch matrix (30) comprising a plurality of switches (25, 26, 27), said switch matrix (30) is configured to operate in at least three different switching modes and a controller (50), connected at least with said switch matrix (30), configured to determine said variable operating voltage and to control the switching mode of said switch matrix (30) in dependence of the determined operating voltage. To provide an efficient operation of such device (1) with a variable operating voltage, such as an AC voltage, in a first switching mode, said LED units (10) are connected parallel to each other, in a second switching mode, at least two of said LED units (10) are connected in series and in a third switching mode, said LED units 10 are connected in series with each other.
摘要:
A string of LED loads is supplied by means of a rectified mains voltage. A cathode of each LED load is coupled to ground by means of a string. The strings are made conductive and non-conductive one by one in dependency of the instantaneous value of the rectified mains using both voltage and current sensing.
摘要:
LED light source suitable for use with a phase cut dimmer (III), comprising •input terminals (K1, K2) for connection to an AC supply voltage, •a rectifier (I) coupled to the input terminals, 108 a series arrangement comprising N LEDs (LL1, LL2, LL3) coupled to the rectifier, •control circuitry (EX) for sequentially activating (deactivating) the LEDs as the supply voltage increases (decreases), wherein the control circuitry comprises: •N controllable current regulators, each regulator being coupled between the cathode of a LED and ground and comprising a transistor and one impedance in series, •a global current control circuit (X) coupled to the control electrodes of said transistors and comprising circuitry for adjusting the voltage at said control electrodes in dependency of the phase angle, •a series arrangement of a switch (S) and a capacitor (C1) coupled- to the rectifier and •means (VIII) for rendering said switch conductive in case the AC supply voltage drops below a reference value.