Abstract: A vacuum cleaner with a suction nozzle which is coupled to a handle on which a user of the vacuum cleaner can exert a pushing or pulling force for moving the suction nozzle over a surface to be cleaned. The suction nozzle is provided with an electrical drive for exerting a driving force on the suction nozzle, such that the pushing or pulling force to be exerted by the user is limited.According to the invention, the vacuum cleaner comprises a detector capable of measuring the pushing or pulling force, exerted on the handle and an electrical controller for controlling the driving force as a function of the measured pushing or pulling force. The controller controls the driving force in such a manner, for example, that the measured pushing or pulling force remains substantially zero. It is thus possible for the user to move the suction nozzle effortlessly over the surface to be cleaned.

Abstract: A flyback converter based on a switcher IC with Pulse Width Modulation control of the switching transistor. The pulse width is controlled by changing the input current at the control input. Under normal operating conditions the voltage at the control input is maintained at a fixed level, which voltage also serves as a supply voltage for the control unit. A charge pump provides extra charge for the smoothing capacitor at the control input when the load would cause the voltage across the smoothing capacitor to collapse below the fixed level, thereby preventing the control unit from entering the auto-restart mode of the switcher IC. In this way the flyback converter can be used as a constant power source for charging rechargeable batteries with a working voltage lower than the nominal operating output voltage of the converter.

Abstract: A switching power supply with synchronous rectification by means of a diode and a parallel-connected electronic switch. By means of a one-shot circuit the electronic switch is driven into conduction during a fixed portion of the time period during which the diode would be conductive without the electronic switch.

Abstract: A power supply system for an apparatus (SVR) with a rechargeable battery (B) has its power supply unit (PSU) coupled to the apparatus (SVR) by a two-wire connection (PSA/SVA; PSB/SVB). The power supply unit (PSU) having a flyback converter (DCC) with a transformer (TR) which supplies the battery (B) with charging current. The converter (DCC) is stopped periodically during breaks in which the apparatus (SVR) applies a status signal (STS) to the power supply unit via the two-wire connection. The power supply unit detects the status signal by means of a status detector (STD) and depending on the meaning of the status signal it switches the converter to another value of the charging current. When the battery (B) is full, which is detected by a battery management unit (BMU), or when the charging current is too large, which is detected by a comparator (CMP) and a current-sensing resistor (R2), it is thus possible to switch from fast charging to trickle charging.

Abstract: A circuit arrangement for operating a high pressure discharge lamp having a full bridge commutator network. A capacitor across each of four commutator switches forms a tuned circuit together with a ballast coil for soft switching. To counteract the core material of the ballast coil from vibrating audibly during lamp operation about no more than 15% of the commutation cycle elapses between turning off the first of the four commutator swithes and turning on the last of the four commutator switches.

Abstract: In a switched-mode power supply a coil is periodically connected across an input voltage by means of a switching element. The switching element is turned off when the voltage across a sensing resistor in series with the switching element exceeds a given threshold. The threshold is reached sooner when the input voltage increases. This effect is compensated by an inductive element in series with the sensing resistor, through which inductive element the same current flows as through the sensing resistor.

Abstract: A device for generating a control signal voltage which is dependent on a resistance value of a variable resistor (8) includes a transformer (24) having a first winding (22) which is in series with the variable resistor and a rectifier diode (20). A current generator (32) coupled to a power source is coupled to a second winding (26) of the transformer and supplies it with a periodically interrupted current (I.sub.2). Upon each such interruption an exponentially decreasing current will flow through the first winding and also through the variable resistor (8). The peak value of the voltage drop produced by such current across that resistor is proportional to the resistance value thereof. It is also produced across the first winding (22) and is detected by the peak detector (62). That constitutes the control voltage (U.sub.c). Since the variable resistor is fully electrically isolated from the power source, it can be safely touched without shock hazard.

Abstract: A power supply circuit having a standby mode includes an input terminal, an output terminal and a reference terminal. A direct voltage source is connected to the input terminal and the reference terminal and a load is connected to the output terminal and the reference terminal. A series arrangement of an inductive element and a diode are connected to one another at a first node. The inductive element is connected between the input terminal and the first node and the diode is connected between the first node and the output terminal. A first electronic switch has a main current path connected between the first node and the reference terminal. A drive circuit periodically makes the main current path of the first electronic switch conductive and non-conductive. The drive circuit comprises a first switching device for making the main current path of the first electronic switch permanently non-conductive in response to a standby signal (SBS).