Abstract: A 0-10V dimming interface protection circuit generating an indication that line voltage is applied across first and second leads of the dimming interface controlling light output by a lamp, includes a first device for limiting current serially connected between a line voltage source and the first lead of the dimming interface, a second device connected across the first and second leads for detecting application of line voltage to the dimming interface and for generating a control signal, and a third device for switching, operated in response to the control signal, for causing an increase in resistance of the first device to thereby limit current to the dimmer interface and limit light output by the lamp. According to one aspect of the invention, the protection circuit also includes a fourth device for preventing spurious operation of the second device.

Abstract: A recording apparatus includes a thin film magnetic head (20) with eight write units (21-28) positioned adjacent to each other in a transversal direction (y) to write data in parallel tracks on a magnetic tape (10). Switching arrangement 70 has a switch (SW) to switch from a normal mode to a combination mode. In the normal mode the switch is in a first position (D1) and the switching arrangement (70) couple a first data signal (S1) to a first write unit (21), a second data signal (S2) to a second write unit (22) etc., so that in the normal mode eight tracks (T21-T28) are written on the tape resulting in a first track density. In the combination mode the switch is in a second position (D2) and the switching arrangement couples the first data signal (S1) to the first and second write units (21 and 22), the second data signal (S2) to the third and fourth write units (23 and 24) etc.

Abstract: A digital lamp signal processor senses lamp current and lamp voltage in real time. These two signals are sufficient to obtain information, such as real lamp power calculation, necessary to control ballast operation and fault detection. The apparatus measures the phase of lamp current and voltage, the peak current and voltage, and calculates the average lamp current and voltage. The digital lamp signal processor eliminates the effect of parasitic capacitance of power wiring and a signal condition circuit. It may detect and control hard switching and apply over current and voltage protection. The apparatus directly processes AC signals, allowing for simple and easily integrated single chip design.

Abstract: A recording apparatus for recording an information signal on a magnetic record carrier includes a write driver circuit and a magnetic write head. The write driver circuit comprises a first voltage driver and a second voltage driver. A first current driver and a second current driver are present for driving the write head. The first and second voltage driver each include a respective series circuit of an npn transistor and a bidirectional impedance element coupled between a point of constant potential and the respective outputs of the first and second voltage drivers.

Abstract: A circuit arrangement for supplying a load which comprises a discharge lamp. The circuit includes apparatus for generating a DC voltage and provided with input terminals for connection to a supply voltage source. A rectifier is coupled to the input terminals for rectifying an AC voltage supplied by the supply voltage source. In addition, there are output terminals for connection to the load and a DC-DC converter connected between the rectifier and the output terminals and provided with a first inductor, a first unidirectional element, and a switching element. The output terminals are interconnected by a circuit branch which comprises a series arrangement of an impedance and a first capacitor, which impedance is shunted by a further unidirectional element. As a result, the inrush current which flows immediately after switching-on of the circuit arrangement is limited.

Abstract: A timing circuit which is used to synchronize different circuit to each other. The timing circuit includes adjustable delay apparatus which delay an input signal with a predetermined value. The timing circuit uses counting devices to count the input signal and the delayed output signal and thereby provides a simple and more cost effective timing circuit.

Abstract: An apparatus for electrochemically machining of a workpiece by means of an electrode has an actuator for setting a gap between the electrode and the workpiece. The apparatus further has a channel for flushing the gap with an electrolyte and a container for containing the electrolyte. Power cords and are provided for feeding an electric current I supplied by a power supply through the electrolyte in the gap. Near the gap an antenna is provided to pick up electromagnetic waves radiated from the gap. The antenna is connected to a band-pass filter which passes signals in a frequency band of 40 to 100 MHz to a level detector. The level detector compares the amplitude of the filtered signal with a threshold value and supplies a stop signal to the control unit when the amplitude exceeds the threshold value. The control unit is programmed to open a switch in the power supply in response to the stop signal.

Abstract: In a device (1) having a variable-speed motor (2), a single switching device (9) has been provided for influencing the speed of the motor and for generating turn-off voltage transients (SP) on a coil terminal (3b) of the motor. The turn-off voltage transients can be applied to a voltage boosting circuit (14) for generating a d.c. control voltage required for driving a control electrode of the single switching device. This d.c. control voltage is supplied to the control electrode of the switching device with the aid of a control pulse generator (10). The d.c. control voltage reaches a higher value than the d.c. supply voltage (V) applied to the device (1). Preferably, the device includes a starting circuit (20), by which a minimum d.c. control voltage, required for the control electrode of the single switching device, can be generated for the first time in order to drive the single switching device into its conductive state.

Abstract: An electro-stimulation apparatus comprises an electrode system for measuring local electrical impedance. The electrode system includes a multitude of electrode pads and a counter electrode held at a reference voltage. The electrode pads and the counter electrode are assembled in an electrode unit. A particular embodiment of the electro-stimulation apparatus comprises an electronic circuit including a source group of electrode pads and a sink group of electrode pads and a source conductor for applying a first electrical quantity to electrode pads of the source group. The electronic circuit also includes a sink conductor for receiving a second electrical quantity from electrode pads of the sink group. Switching elements couple individual electrode pads of the source group to the source conductor. Other switching elements couple individual electrode pads of the sink group to the sink conductor.

Abstract: A PWM amplifier comprising a comparator and an integrator is known to amplify, for example, audio signals. One drawback of the known PWM amplifiers is the maximally achievable loop gain is low. To overcome the disadvantages of the prior art PWM amplifiers, a PWM amplifier is provided with a second integrator in the feedback loop.

Abstract: A circuit arrangement for monitoring an output load (4) of a digital-to-analog current converter (1). The digital-to-analog converter supplies an analog output current dependent on a digital comparison data word to a first resistor (2) and, if present, to the output load (4) arranged in parallel with the first resistor. In order to provide a continuous monitoring of the output load, a digital first comparator (12) compares the data words applied to the digital-to-analog current converter (1) with at least one comparison data word. An analog second comparator (5) compares the voltage drop across the first resistor with at least one reference voltage and applies its output signal to a flip-flop (8). A comparison circuit (11) monitors the magnitude and/or the presence of the output load dependent on the output signals of the first comparator and the flip-flop.

Abstract: In a multiple-output digital to analog converter, digital input data (Dd) is converted into a plurality of analog output voltages (Voi) across associated loads (Li). A timing generator (TG) generates time periods (Ti1) in dependence on the digital input data (Dd). A buffer (B1) has an output (O1) to supply a waveform (WF1) to the loads (Li) via a coupling circuit (S1i). The coupling circuit (S1i) couples a certain load (Li) to the buffer output (B1) during an associated time period (Ti1). The output voltage (Voi) across the certain load (Li) is related to a value of the waveform (Wf1) at the end of the associated time period (Ti1) when the coupling circuit decouples the load (Li) from the buffer output (O1). The multiple-output digital to analog converter further comprises a plurality of dummy loads (Ldi), each one of the dummy loads (Ldi) is associated to a corresponding one of the loads (Li).

Abstract: A hearing aid comprises a controllable oscillator, a control circuit and a receiver for receiving a reference signal from a remote control. The control circuit is coupled to the controllable oscillator and to the receiver and is constructed so as to control the frequency of a clock signal generated by the oscillator by means of the reference signal received by the receiver.

Abstract: A method of electrochemically machining an electrically conductive workpiece in an electrolyte by applying electrical pulses between the workpiece and an electrically conductive electrode, one or more machining pulses alternating with passivation voltage pulses for depositing passivation layers on the workpiece. The amplitude of the passivation voltage pulses is adjusted during an adjustment procedure in which the amplitude of the passivation voltage pulses is increased gradually from zero to the voltage at which the workpiece starts to dissolve in the electrolyte. After each voltage increase the resistance of the gap between the electrode and the workpiece is measured. The voltage value for the highest gap resistance is stored in a memory and used during further machining. The time span of the passivation voltage pulses may be divided into time slices and for each time slice the voltage is adjusted for maximum gap resistance during that time slice.

Abstract: A ballast including a single sense element and a single controller for mulitple lamp operation. The ballast avoids the need for separate feedpaths for sensing individual lamp conditions and/or the need for separate controllers for controlling the individual lamp conditions. Consequently, the ballast scheme avoids the use of expensive components (e.g. controllers and chokes) and minimizes the number of components required in order to operate multiple lamps.

Abstract: Current measuring device which comprises a current sense resistor (2) for generating a voltage proportional to the current to be measured. The voltage is measured by a MOS transistor (4) having its gate terminal connected to a first terminal of the current sense resistor, and having its source terminal connected to a second terminal of the current sense resistor. The drain current of the MOS transistor is coupled via a current coupling device to the source terminal of a further MOS transistor (10) having its gate and source terminals interconnected. The drain current of the MOS transistor causes a voltage across the further MOS transistor which is proportional to the current in the current sense resistor. This is true only if the voltage across the current sense resistor exceeds the threshold voltage of the MOS transistor. By introducing an offset source (6, 8), an output voltage is obtained which is proportional to the current to be measured for all current values as long as the MOS transistor is conducting.

Abstract: A time period (Td) is generated with a high accuracy and a high resolution. At a starting instant (ti) of the time period (Td), an analog integration operation (3) is started to generate an integration value (ios). At a certain instant (t1), the analog integration operation is interrupted to start counting (2) clock pulses (Clk). A selected number (N;N2) of clock pulses (Clk) is counted to obtain a sub-period (T2). The analog integration operation is resumed at the end of the sub-period (T2) at the integration value (ios) reached at the start of the sub-period (T2). The analog integration operation finishes at an end instant (td) of the time period (Td) at which the integration value (ios) crosses a reference value (Ref).

Abstract: A device for measuring the resistance of an MR element which passes a bias current Imr and which derives a bias voltage. A voltage comparator CMP receives the bias voltage Vmr and a reference voltage Vref. A counter UPCNT has an enable input EN coupled to the output of the comparator and a digital output forming the output of the device. A current source supplies the bias current Imr which represents a digital value received by the current source at its control input which is coupled to the digital output of the counter. The device enables the digital value of a resistance to be measured automatically.

Abstract: An electronic ballast circuit for driving a gas discharge lamp from a mains voltage signal supply includes a ballast bridge unit having upper and lower signal lines. A capacitive divider is disposed across the bridge. The capacitive divider comprises at least two capacitors coupled in series at a common reference voltage signal terminal. The bridge unit also includes two diodes coupled in series at a rectifier common terminal, wherein each of the diodes is respectively coupled to one of the signal lines of the bridge unit. The bridge unit further includes an input converter bridge and an output converter bridge each having at least two switches coupled in series at input and output common terminals, respectively.

Abstract: A method for operating a lamp which includes the steps of providing an electric lamp having a pair of electrodes and an arc gap therebetween, providing a power supply for applying a voltage and current to the electric lamp, and providing a controller for sensing lamp parameters and configured to control a signal to be applied by the power supply to the electric lamp. The method further includes sensing the parameters of lamp operation. The sensed parameters are compared with desired lamp parameters. The controller commands the power supply to add a current pulse to a specific portion of the lamp current.