569 results about "Lamp current" patented technology

An electronic ballast for high intensity gas discharge lamps where the wave form of the lamp current is square wave providing acoustic resonance and flickering free operation. The circuit, having high efficiency, operates in a wide temperature range providing ideal ballast curve and reliable ignition for the lamps. Furthermore, significant energy saving can be achieved by its externally controlled built in dimming capability.

A circuit arrangement and control thereof for igniting a high intensity discharge (HID) lamp, for reducing the high frequency ripple superimposed on the low frequency rectangular waveform lamp current after ignition, and for increased circuit efficiency. The high frequency ignition voltage is only applied to the lamp during ignition phase and is mainly generated by the second stage of the low pass (LP) filter. The first stage of the LP filter whose resonant frequency is below the second stage further attenuates the high frequency ripple current through the lamp in normal operation. The resulting lamp current is a low frequency rectangular wave with less than 10% high frequency ripple. Acoustic resonance is avoided. The inductor in the first stage of LP filter is operated in discontinuous current mode. Doing so, the active switches are in zero current switching (ZCS) to maximize the circuit efficiency.

An efficient power conversion circuit for driving a fluorescent lamp uses a pre-regulator to generate a regulated voltage with a relatively high level of ripple voltage. The regulated voltage can be varied to provide dimming of the fluorescent lamp. The regulated voltage is provided to a direct drive inverter. The direct drive inverter uses driving signals of fixed pulse widths to generate an output voltage to drive the fluorescent lamp. The output voltage has relatively long on-time durations so that the difference between the peak lamp current and the average lamp current is reduced, thus reducing a lamp current crest factor for improved lamp lighting efficiency.

Disclosed is inductive coupling of power to devices having negative resistances, such as gas-filled discharge lamps (fluorescent tubes, neon signs, and the like) from a primary inductive loop, using resonant conditioning of the power provided to the device. A "C" shaped inductor (202) around the loop and a resonating capacitor (406) in parallel with the inductor provide a current source to the lamp (403) from across the capacitor. The circuit is capable of first igniting a lamp using a higher voltage available when the Q of the unloaded circuit is high, then running the lamp or other device at a controlled current. The lamp current is substantially proportional to the primary inductive loop flux, and substantially independent of the lamp resistance. A second inductor (404) in series with the first though not itself a collector of flux acts as a current limit. Applications include lighting, displays (optionally isolated and dimmable), and production of ultraviolet radiation.

An electric street light controller apparatus and monitoring method allows automatic street light turn-on and turn-off characteristics to be field programmable using RFID technology, lamp current magnitude recording, auxiliary sensor input, diagnostic alarming and data storage for later retrieval in a remote electric street lighting monitoring system. The apparatus and method includes, from a remotely located exciter apparatus using an antenna to transmit a specific frequency and code key to the antenna of an electric street light control and monitoring apparatus associated with the electric street light allowing remote wireless field programming of turn-on fight levels, turn-off light levels, rate of change of light levels, specific turn-on, turn-off, and turn back on sequences during dark hours, and specific remote wireless sensors or internal sensor inputs useful for radiological, biological, chemical, or environmental sensing and alarming. Additionally the method and apparatus includes a method of providing automatic diagnostics for the street lamp bulb, starter and self diagnostics of the controller itself.

An electronic ballast for driving a gas discharge lamp avoids mercury pumping in the lamp by adaptively changing an operating frequency of an inverter of the ballast when operating near high-end. The inverter of the ballast generates a high-frequency AC voltage, which is characterized by the operating frequency and an operating duty cycle. The ballast also comprises a resonant tank for coupling the high-frequency AC voltage to the lamp to generate a present lamp current through the lamp, and a current sense circuit for determining the magnitude of the present lamp current. A hybrid analog / digital control circuit controls both the operating frequency and the operating duty cycle of the inverter with closed-loop techniques. The control circuit adjusts the duty cycle of the inverter in response to a target lamp current and the present lamp current. To avoid mercury pumping, the control circuit attempts to maximize the duty cycle of the inverter when operating at high-end. Specifically, the control circuit adjusts the operating frequency of the inverter in response to the target lamp current signal, the duty cycle of the inverter, and a target duty cycle in order to drive the operating duty cycle toward the target duty cycle.

An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.

A power conversion circuit improves lamp operating life and lamp efficiency by driving a fluorescent lamp with a square wave signal. The square wave signal is an alternating current signal with relatively fast transition times. The square wave signal advantageously reduces lamp current crest factor for more efficient operation of the fluorescent lamp.

An electronic ballast for driving a high intensity discharge (HID) lamp is provided. The electronic ballast includes a voltage boost stage for receiving a DC input voltage and outputting a boosted DC output voltage with a controlled current. It further includes a switching stage for converting the boosted DC output voltage to a switched AC voltage capable of driving the HID lamp. An integrated circuit (IC) is coupled to the voltage boost stage and the switching stage for controlling both. The IC includes a lamp power control circuit comprising a sensing circuit for sensing an output current from the switching stage and the boosted DC output voltage, a current control loop which controls the lamp power if the lamp current is at a maximum level and a power control loop which controls the lamp power if the lamp current is below a maximum level. The IC also includes a controller unit interface and provides an ignition mode and a regular operation mode.

An efficient power conversion circuit for driving a fluorescent lamp uses a minimum pulse generator circuit to control the minimum on-time of a time modulated signal to increase the dimming range of the fluorescent lamp operating over a wide range of temperature and supply voltage. A minimum number of lamp current cycles with respective amplitudes above a preset threshold is typically required to avoid flickering or shimmering during minimum brightness. The minimum pulse generator circuit counts the lamp current cycles and adjusts the on-time accordingly to guarantee the minimum number of cycles with respective amplitudes above a preset threshold under all operating conditions.

A power conversion circuit improves lamp operating life and lamp efficiency by driving a fluorescent lamp with a square wave signal. The square wave signal is an alternating current signal with relatively fast transition times. The square wave signal advantageously reduces lamp current crest factor for more efficient operation of the fluorescent lamp.

A lamp driving apparatus includes a change rate calculating section, a dimming transforming section and a power supplying section. The change rate calculating section calculates a change rate signal from an image signal corresponding to the image. The dimming transforming section outputs a digital dimming signal and an analog dimming signal, in response to a dimming signal provided from an external device and the change rate signal. The power supplying section provides the lamp with power, in response to a vertical synchronizing signal, the analog dimming signal and the digital dimming signal. Thus, although an instantaneous lamp current is increased, life and characteristics of the lamp will not be adversely influenced, and motion blur of a moving image may be removed.

An electronic ballast for driving a gas discharge lamp avoids mercury pumping in the lamp by adaptively changing an operating frequency of an inverter of the ballast when operating near high-end. The inverter of the ballast generates a high-frequency AC voltage, which is characterized by the operating frequency and an operating duty cycle. The ballast also comprises a resonant tank for coupling the high-frequency AC voltage to the lamp to generate a present lamp current through the lamp, and a current sense circuit for determining the magnitude of the present lamp current. A hybrid analog / digital control circuit controls both the operating frequency and the operating duty cycle of the inverter with closed-loop techniques. The control circuit adjusts the duty cycle of the inverter in response to a target lamp current and the present lamp current. To avoid mercury pumping, the control circuit attempts to maximize the duty cycle of the inverter when operating at high-end. Specifically, the control circuit adjusts the operating frequency of the inverter in response to the target lamp current signal, the duty cycle of the inverter, and a target duty cycle in order to drive the operating duty cycle toward the target duty cycle.

Disclosed a high pressure discharge lamp driving apparatus for driving a high pressure discharge lamp during a stable operation thereof with an AC lamp current alternating for opposite half-cycle periods, the apparatus comprising an AC lamp current supply for supplying the AC lamp current to the high pressure discharge lamp, a detector for detecting the output AC lamp current to the high pressure discharge lamp, a controller responsive to the detector for controlling the AC supply to output the AC lamp current with a waveform which is characterized by that (i) a mean value in the second half of each half-cycle period is larger than the means value of the first half of each half-cycle period, (ii) no pulse current is contained in the second half of each half-cycle period, (iii) the AC lamp current has a maximum value immediately after polarity change between the positive and negative half-cycle periods, and (iv) the AC lamp current has also a waveform defined by that the ratio (d / a) of the maximum value (d) of the AC lamp current and a mean value (a) of the AC lamp current in its each half-cycle period satisfies a following equation.

A means of ballasting for high intensity discharge (HID) lamps, wherein the necessary lamp striking voltage, warm-up current and steady state running current may all be controlled using only two power switching transistors 9,10 operating in two discrete modes is provided for avoiding acoustic arc resonance during the steady state running. A low frequency lamp current is generated with a frequency modulated high frequency ripple.

An electronic ballast for driving a gas discharge lamp comprises a measurement circuit for measuring a lamp current flowing through the lamp and a lamp voltage produced across the lamp. The ballast comprises a first winding magnetically coupled to a main transformer of an inverter circuit, and a second winding magnetically coupled to a resonant inductor of a resonant tank circuit. The first and second windings are coupled in series electrical connection to generate a voltage representative of the magnitude of the lamp voltage. The ballast further comprises a current transformer having primary windings coupled in series with the electrodes of the lamp. The measurement circuit integrates the current conducted through secondary windings of the current transformer only during every other half-cycle of the lamp voltage to generate a control signal representative of the magnitude of the lamp current that is in-phase with the lamp voltage.

A backlight assembly includes a plurality of lamps emitting a first light. A optical member converts the first light to a second light having enhance optical characteristics. A receiving member receives the lamps and the optical member. The receiving member has protrusions that are aligned with the lamps and protrude away from the lamps. The protrusions increase the distance between the lamps and the receiving member, thereby reducing current leakage from the lamp.

A dimming ballast control circuit for driving a ballast power switching circuit powering a gas discharge lamp. The circuit includes a driver circuit for driving high and low side switches of the ballast power switching circuit; a control circuit for driving the driver circuit including an oscillator circuit for providing an oscillating signal to control the frequency of operation of the ballast power switching circuit, the ballast power switching circuit outputting lamp powering pulsed signals; and a dimming control circuit having an input, the dimming control circuit receiving an AC lamp current feedback signal at the input, the dimming control circuit further receiving a DC input voltage reference at the input whereby the DC input voltage reference determines a desired dimming level of the lamp and the AC lamp current feedback signal maintains the lamp brightness at the desired dimming level.

A lighting circuit for a light source includes a drive circuit and an overcurrent protection circuit. The drive circuit supplies power to the light source. The overcurrent protection circuit is inserted between the drive circuit and the light source. The overcurrent protection circuit restricts a lamp current flowing into the light source so that the lamp current does not exceed an overcurrent threshold value. The overcurrent protection circuit includes a transistor, an inductor, a rectifier, a current sensor and an overcurrent protection controller. The current sensor generates a current detection signal according to the lamp current. The overcurrent protection controller controls ON / OFF of the transistor based on the current detection signal and the overcurrent threshold value. The transistor, the inductor and the rectifier are disposed in a T-shape.

An electronic ballast for high intensity gas discharge lamps where the wave form of the lamp current is square wave providing acoustic resonance and flickering free operation. The circuit, having high efficiency, operates in a wide temperature range providing ideal ballast curve and reliable ignition for the lamps. Furthermore, significant energy saving can be achieved by its externally controlled built in dimming capability.

In a discharge lamp lighting apparatus, a power supplied to a discharge lamp La through a DC-DC converter 1 and an inverter 2 is controlled depending on detection results of a lamp voltage detection unit 6 and a lamp current detection unit 7, and in an electrode heating period an alternation time of an output to the discharge lamp when starting actuation of the discharge lamp is set longer than an alternation time in a steady lighting period, and the alternation time in the electrode heating period is increased depending on lowering of a supply power or current to the discharge lamp. Thus, even when a lamp current is suddenly changed, the discharge lamp is prevented from going off at the time of polarity inversion without lowering a life.

A lamp actuating device includes a number of lamps each having an output terminal, an inverter circuit coupled to the lamps to energize the lamps, a low frequency control unit coupled to the inverter circuit, to set an average value for the level of the effective lamp current at the output terminals of the lamps and to control the inverter circuit, a number of current detecting devices coupled between the lamps and the low frequency control devices to obtain and send the average current value at the output terminals of the lamps to the low frequency control unit. A number of regulating devices are coupled between the lamps and the low frequency control unit, to maintain each lamp at the predetermined average value of the effective current.

An object of the invention is to provide method of operating a projection-type system, which method is capable of suppressing flicker and minimizing gradation disorder at the same time by superimposing a pulse current on a d.c. lamp current to stabilize arc while synchronizing the superimposition of the pulse current on the d.c. lamp current with a predetermined segment. The method of operating a projection-type system configured to pass light emitted from a high-pressure discharge lamp lit by d.c. lighting through divided plural color segments sequentially to project an image onto a screen, includes superimposing a pulse current on a d.c. lamp current in the high-pressure discharge lamp in synchronism with at least one specific color segment.

In a lamp operation controller and a method thereof, for obtaining a stable light emission, simply and certainly, without necessity of detection of a parameter accompanying discharge, the lamp operation controller, for operating a discharge lamp having a pair of electrodes, which are disposed at both ends of a light emission tube to have a predetermined distance therebetween, converts electric power of an electric power source 1, through an inverter, into alternating voltage and alternating current, changing the polarity thereof continuously and alternately, so as to produce operating current, and apply that across the pair of the electrodes of the discharge lamp, thereby letting the lamp to emit a light. A driver circuit provides a pulse at a trailing edge of the lamp current or the lamp voltage to be supplied when the discharge lamp emits the light, and also determine amplitude of the pulse, in accordance with fluctuation on the lamp voltage (VL) with respect to lighting time of the discharge lamp, which is measured in advance.

The invention relates to a frequency-modulation electronic ballast for a dimmable fluorescent lamp, comprising an EMC filter rectifier circuit, an input voltage sampling circuit, a PFC booster circuit, a half-bridge driver circuit, a DC-AC half-bridge inverter circuit, an ignition circuit, a microprocessor and a lamp current / voltage sampling circuit; the EMC filter rectifier circuit is connected with the PFC booster circuit; the PFC booster circuit is connected with the half-bridge driver circuit and the microprocessor; the half-bridge driver circuit is connected with the DC-AC half-bridge inverter circuit; the DC-AC half-bridge inverter circuit is connected with the ignition circuit; and the lamp current / voltage sampling circuit is connected with the microprocessor. The invention has the following advantages: the electronic ballast dose not use special integrated control circuit but universal microcontroller so as to perform the functions thereof through pulse frequency modulation dimming method, thus the whole structure is simple, and various dimming interfaces can be expanded conveniently to perform digital dimming.

A driving circuit for a single-string light-emitting diode (LED) lamp includes a push-pull converter. The push-pull converter converts an input low DC voltage (such as 12-19V) to a high DC voltage (such as above 200V) to supply power to the single-string LED lamp. The driving circuit controls a lamp current flowing through the single-string LED lamp by means of constant current and adjusts brightness of the single-string LED lamp by means of pulse-width modulation (PWM) dimming. In addition, the single-string LED lamp provides the standardization design for connectors of the driving circuit used to connect to the single-string LED lamp so that the driving circuit has better common-use characteristic. Moreover, the driving circuit does not need a current balance circuit and only needs a cheaper and general-purpose integrated circuit to control the push-pull converter to reduce design cost of the driving circuit.

The invention provides an ultraviolet disinfection method and an ultraviolet disinfection device capable of running quickly and disinfecting fluid efficiently. In the method, fluid or deposited liquid in a bending fluid pipeline is irradiated fully by ultraviolet for 0.5 to 3 seconds, and the ultraviolet radiation of the ultraviolet is improved by using a low-pressure and high-strength ultraviolet lamp, so that the ultraviolet radiation dose of the fluid is more than 10 mJ / cm<2>(mW s / cm<2>) to disinfect the fluid fully, wherein the current of the low-pressure and high-strength ultraviolet lamp is between 0.3 and 8.0 A, and the current density of the lamp is between 0.3 and 1.5 A / cm<2>. Simultaneously, the cold end of mercury is arranged at the bottom of the ultraviolet lamp and is heated,and heat is preserved, so that the temperature is controlled to be between 40 and 50 DEG C; and the ultraviolet lamp is started instantly so that the ultraviolet illumination is close to the maximum value quickly so as to meet the requirement of the ultraviolet radiation dose of the fluid and ensure quick, efficient and full disinfection.

A circuit for ballasting for high intensity discharge (HID) lamps, wherein the necessary lamp striking voltage, warm-up current and steady state running current may all be controlled using only two power switching transistors operating in two discrete modes is provided for avoiding acoustic arc resonance during the steady state running. A low frequency lamp current is generated with a frequency modulated high frequency ripple.

A method and system to supply current to a high pressure lamp is provided, the method and system comprising an alternating lamp current waveform with a half cycle mean amplitude I1 and a half cycle time duration T, a current pulse waveform including at least one current pulse with a half cycle mean amplitude I2 and at least one current pulse occurring after the trailing edge of a half cycle of the alternating lamp current, the pulse having a half cycle duration of Tp. These waveforms are combined to generate a current waveform including a current pulse waveform, the current pulse waveform starting after a time delay Td from the trailing edge of a half cycle of the alternating lamp current waveform, the time duration Tp of the at least one current pulse lasting less than the remaining time before the leading edge of the second half cycle of the alternating lamp current waveform. The combined current waveform supplies current to a high pressure lamp and produces a cone shaped tip protrusion which reduces lamp flicker.

The present invention refers to environmental protection type intelligent current-reducing and energy-saving control equipment method for street lamp. It contains single lamp controller circuit and street lamp circuit, wherein single lamp controller circuit module consisting of LCU control circuit module and multiple tapping power reducing ballast module, the output of said LCU control circuit respectively connected with one end of multiple tapping power reducing ballast, ac compensation capacitor module and street lamp circuit module through one end of multiple step control equipment of 220 ac power supply. Said invention has advantages of realizing single lamp independent timing or networking control, street lamp soft startups control, and street lamp relative constant power control etc, without harmonic contamination to electric power network, and prolonging street lamp service life.