Minebea Company, Limited

Mineba Co., Ltd.

Mineabea Co., Ltd.

Robert Weger

Mykhaylo Raykhman

Hiroshi Shinmen

Manfred Schlenk

Martin Feldtkeller

Michael Herfurth

Masaya Yamashita

Hans Hoffmann

Jurgen Adam

The invention describes a control circuit for backlighting having a plurality of control channels in each of which a light emitting diode string is controlled. The control circuit has a balancing device for balancing the currents in the individual control channels, and a control unit that is connected to a power factor correction circuit (PFC), to a bridge circuit and to a primary-side current measuring device. Each control channel has a switch for switching the light emitting diode string that is connected to a separate dimming signal. The control circuit furthermore has at least one smoothing capacitor and one current limiter that limits the charging current for the smoothing capacitor. The control unit is additionally designed such that if all the dimming signals are logical ON, the output voltage of the PFC is regulated with the aid of the current measuring device such that the current on the primary side corresponds to a pre-determined setpoint value and that as soon as at least one dimming signal is logical OFF, the output voltage of the PFC is kept constant at its last value (FIG.).

Control circuit for LED backlighting

A down converter for converting an input DC voltage (Vin) into a lower output DC voltage (Vout). The down converter has on the primary side () an LC series resonance circuit () that can be connected via a first switch (S) to the input voltage (Vin) and via a second switch (S) to ground. On the secondary side (), an output switch (S) and an output capacitor (C) are each connected in parallel to the DC voltage output (Vout) and connected to each other through an inductor (L). The output switch (S) is connected via a diode (Dr) to the input voltage (Vin) so as to divert voltage overshoots.

Down converter

An electrical appliance, particularly a television or a monitor, having a lighting device () having light emitting diodes (). The light emitting diodes (LED) () are collected in LED strings () and controlled by a balancing network (). The balancing network () has a circuit branch () for each string (), the circuit branches () being connected in parallel to each other. Disposed in each circuit branch (), is a bridge rectifier () to which the LED string () is connected. Moreover, each circuit branch has a balancing transformer (), wherein all the secondary windings () of the balancing transformer () are connected in series in a closed conductor loop (), by which the currents in all circuit branches are balanced.

Electrical appliance having a lighting device having light emitting diodes

A method and a device for controlling gas discharge lamps using a direct current/alternating current inverter (DC/AC inverter) that is operated at a predetermined frequency and that generates an AC output voltage U for operating the gas discharge lamps from a DC input voltage which has a residual ripple. The DC/AC inverter is operated in zero voltage switching (ZVS) mode, wherein the DC input voltage is used as the control variable for the lamp current I, wherein fluctuations in the lamp current Icaused by the residual ripple of the DC input voltage are compensated by a variation in the switch-on times and/or switch-off times of the switching elements Q, Qof the DC/AC inverter.

Method for controlling gas discharge lamps

The proposed circuit makes it possible to operate a plurality of gas discharge lamps, particularly cold cathode tubes, across a common voltage source. The circuit reduces the resistance tolerance of the lamp characteristic curves through controlled debalancing of the lamp currents with the aid of debalancing modules. Through the active reduction in the resistance tolerance, the requirements placed on the electric strength of the balancing transistors as well as energy losses of the balancing circuit are reduced.

Electronic circuit for operating a plurality of gas discharge lamps across a common voltage source

A method for controlling a high-frequency transformer by which the acoustic transformer noises occurring during intermittent operation (burst operation) are reduced. This is achieved according to the invention by halving a length of the first and the last pulse of an AC voltage pulse train or the first and the last half-wave in the ON interval (Tn). This goes to avoid magnetizing peaks in the core that cause a major part of the background noise.

Method for controlling a high-frequency transformer

The presented circuit makes it possible to operate a plurality of gas discharge lamps, particularly cold cathode tubes, at a common voltage source. The uniform distribution of current to all the lamps is achieved without using any magnetic components, but only using semiconductor components.

Electronic circuit for operating a plurality of gas discharge lamps at a common voltage source

According to the present invention an electronic stabilizer circuit for suppressing startup instabilities when supplying a cold cathode fluorescent lamp with current is proposed which is connected in series with a power supply line of the cold cathode fluorescent lamp. The stabilizer circuit has variable impedance which is automatically adjusted depending on the magnitude of the lamp current thus limiting the lamp current to a certain current threshold.

Electronic stabilizer circuit for suppressing startup instabilities in cold cathode fluorescent lamps

The invention relates to an electrodeless high frequency gas discharge lamp according to the induction principle that, as a result of its design and construction, shows particularly low electromagnetic interference with a simultaneous increase in light efficiency. The gas discharge lamp according to the invention owes these advantageous properties on the one hand to the high coupling factor between the discharge current and the exciting current and, on the other hand, to the essentially homogeneous field conditions in the discharge vessel, which has been achieved by designing the discharge vessel to take the form of a hollow cylindrical ring which is seated directly over the exciter winding that extends over the entire length of the discharge vessel on a fully-closed, highly-permeable ferrite core.

Electrodeless gas discharge lamp

The invention relates to a transformer () for balancing the current in an AC circuit, comprising a primary winding (), a secondary winding () and a main inductance (). The transformer is characterized in that a capacitive component is connected in parallel to the primary winding () or to the secondary winding (), whose capacitance value is determined such that the reactive current Ibrought about by the main inductance () is substantially compensated. A transformer of this kind can preferably be employed in current balancing circuits as used, for example, in systems for backlighting LCD displays.

Transformer for balancing currents

To provide a multiple-light discharge lamp lighting device that stabilizes and equalizes tube current of a plurality of discharge lamps without arranging a Ballast element to the secondary side of an inverter transformer with low costs. A multiple-light discharge lamp lighting deviceaccording to the present invention includes inverter meansand a plurality of inverter transformers TRto TR. Discharge lamps Lato Laare connected to secondary windings Nsto Nsn of the inverter transformers TRto TR. Preferably, variable impedance elements Zto Z, as variable inductance elements, are serially connected to primary windings Npto Npn of the plurality of inverter transformers TRto TR. Accordingly, the tube current can be stabilized and equalized without using an element resistant to a high voltage.

Multiple-light discharge lamp lighting device

A multiple discharge lamp lighting apparatus is provided which achieves stable and uniform lamp currents in a plurality of discharge lamps without a ballast element at the secondary side of an inverter transformer. The multiple discharge lamp lighting apparatus includes an inverter, and a plurality of inverter transformers each of which has a discharge lamp connected at a secondary winding thereof. A balance inductance element is provided between the primary side wirings of any adjacent pair of the plurality of inverter transformers. Each of the inverter transformers includes a tight coupling section and a loose coupling section, which function as a balance coil and an impedance element, respectively, whereby the lamp currents of the discharge lamps are stabilized and equalized without using a high withstand voltage element.

Multiple discharge lamp lighting apparatus

A DC/DC converter having an input switching stage on the primary side and a plurality of output channels on the secondary side of the converter, each output channel having a secondary control loop and a monitoring device, the monitoring devices monitoring the operation of the secondary control loops, and a primary control loop being provided on the primary side which receives output signals from the monitoring devices and drives the input switching stage according to the output signals.

DC/DC converter having an input switching stage and a plurality of output channels

There is provided a multiple discharge lamp lighting apparatus, which includes an inverter and plurality of inverter transformer. In the multiple discharge lighting apparatus, a discharge lamp is connected to the secondary winding of each inverter transformer, a ballast impedance element is connected in series between a switch of the inverter and the primary winding of each inverter transformer, and a current balancing unit is provided between each two adjacent inverter transformers.

The invention relates to a high voltage transformer having a double symmetric winding arrangement. The transformer comprises a closed core () having a first and a second leg (), a first and a second coil member () having a first end, a second end and a middle section. Each coil member () is wound with a first and a second primary winding (Prim, Primand Prim, Prim) and a first and a second secondary winding (Sec, Secand Sec, Sec), the first primary winding (Prim, Prim) being disposed at the first end and the second primary winding (Prim, Prim) at the second end of each coil member () respectively. The first secondary winding (Sec, Sec) of each coil member () is wound in the direction of the first end starting from the middle of the coil member, and the second secondary winding (Sec, Sec) of each coil member () is wound in the direction of its second end starting from the middle of the coil member, the winding direction of the first secondary winding (Sec, Sec) being opposite to the winding direction of the second secondary winding (Sec, Sec), and a first electric connection (HV, HV) being disposed in the middle of each coil member ().

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Wels, Austria

Robert Weger