Abstract: 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.

Abstract: 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 (2) an LC series resonance circuit (4) that can be connected via a first switch (S1) to the input voltage (Vin) and via a second switch (S2) to ground. On the secondary side (3), an output switch (S3) 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 (S3) is connected via a diode (Dr) to the input voltage (Vin) so as to divert voltage overshoots.

Abstract: An electrical appliance, particularly a television or a monitor, having a lighting device (8) having light emitting diodes (12). The light emitting diodes (LED) (12) are collected in LED strings (11) and controlled by a balancing network (17). The balancing network (17) has a circuit branch (19) for each string (11), the circuit branches (19) being connected in parallel to each other. Disposed in each circuit branch (19), is a bridge rectifier (20) to which the LED string (11) is connected. Moreover, each circuit branch has a balancing transformer (23), wherein all the secondary windings (26) of the balancing transformer (23) are connected in series in a closed conductor loop (27), by which the currents in all circuit branches are balanced.

Abstract: 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.

Abstract: 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 IL, wherein fluctuations in the lamp current IL caused 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 QH, QL of the DC/AC inverter.

Abstract: A DC-DC converter (1) is provided having a resonant half-bridge circuit (2) and a transformer (TX1) that has a primary winding (P1) and a secondary winding (S1, S2) on a transformer core (4). The voltage converter (1) has a secondary circuit (3) with which the secondary winding (S1, S2) is associated and a switch (Q3, Q4) that is connected in series to the secondary winding (S1, S2), and a smoothing capacitor (C0, C01). The switch (Q3, Q4) is operated as a synchronous rectifier.

Abstract: 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.

Abstract: 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.

Abstract: An electrical appliance, particularly a television or a monitor, having a lighting device (8) having light emitting diodes (12). The light emitting diodes (LED) (12) are collected in LED strings (11) and controlled by a balancing network (17). The balancing network (17) has a circuit branch (19) for each string (11), the circuit branches (19) being connected in parallel to each other. Disposed in each circuit branch (19), is a bridge rectifier (20) to which the LED string (11) is connected. Moreover, each circuit branch has a balancing transformer (23), wherein all the secondary windings (26) of the balancing transformer (23) are connected in series in a closed conductor loop (27), by which the currents in all circuit branches are balanced.

Abstract: 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.

Abstract: The invention relates to 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. According to the invention, 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 IL, wherein fluctuations in the lamp current IL caused 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 QH, QL of the DC/AC inverter.

Abstract: 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.

Abstract: 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.

Abstract: The invention relates to a transformer (10) for balancing the current in an AC circuit, comprising a primary winding (12), a secondary winding (14) and a main inductance (16). The transformer is characterized in that a capacitive component is connected in parallel to the primary winding (12) or to the secondary winding (14), whose capacitance value is determined such that the reactive current IL brought about by the main inductance (16) 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.

Abstract: 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.

Abstract: 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 device 10 according to the present invention includes inverter means 12 and a plurality of inverter transformers TR1 to TRn. Discharge lamps La1 to Lan are connected to secondary windings Ns1 to Nsn of the inverter transformers TR1 to TRn. Preferably, variable impedance elements Z1 to Zn, as variable inductance elements, are serially connected to primary windings Np1 to Npn of the plurality of inverter transformers TR1 to TRn. Accordingly, the tube current can be stabilized and equalized without using an element resistant to a high voltage.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.