Abstract: Apparatus for controlling an inductive load, particularly for a coil of an electromagnet, including an electronic chopper switch fitted in series with the coil and controlled by a pulse width modulator, and an opening switch, also fitted in series with the coil. A transformer converter 20 with two secondary windings, one of which is connected to the modulator 11, and the other is connected to the gate of the opening transistor T2 via a switch 25 solicited by the opening signal.

Abstract: The present invention relates to an arrangement for reduction of magnetic alternating fields for example in a vehicle or similar which comprises at least one electrical system which comprises at least two elements of which at least one comprises one or more components generating and/or consuming electricity, and which are connected through at least one connecting cable in which flows a current having an alternating current component generating a low frequency magnetic field. The arrangement also comprises at least one detecting element which is arranged to detect the alternating current component, and means for generating a compensating current with the use thereof. The compensating current flows adjacent to the connecting cable in such a way that the low frequency magnetic field is reduced or eliminated.

Abstract: A power supply apparatus is provided for energizing an electronic control unit mounted on a vehicle having a battery and a starter switch. The apparatus includes a coil connected to the power supply line, and a switch which operates for selectively enabling a current to flow through the coil and cutting off the current through the coil. A control circuit operates for selectively changing the switch between an ON state and an OFF state when the starter switch assumes an ON position. The ON and OFF states alternate in accordance with predetermined delays.

Abstract: An electromagnet drive apparatus being characterized by a switching element 1 connected in series with a coil 3 of an electromagnet; a pulse signal generation circuit 16 which generates, on predetermined cycles, a pulse signal used for turning on the switching element; a regenerative circuit 4 which permits flow of a regenerated electrical current when the switch section is turned on and the switching element is turned off from a state in which the switch section and the switching element are in an on state and a source voltage is applied to the coil of the electromagnet, and which causes the power absorbing element to immediately reduce the regenerated electrical current flowing through the coil of the electromagnet when the switch section and the switching element are turned off; and a delay circuit 11 which turns on the switch section by application of the supply voltage and maintains the switch section in an on state until a predetermined period of time elapses after the application of the supply voltage

Abstract: In a circuit, switch (1) switches a current from a reference voltage terminal through an inductive element (3). The energy stored in the magnetic field associated with the inductive element when a current is flowing is transferred on interruption of the current either capacitively or inductively to an energy storage element (4). The stored energy is then returned to re-energize the inductive element (3) when the current flow is restored by the switch (1).

Abstract: The magnetic residual energy stored in a coil is made to decay within a shorter and/or definite time period by the use of a free-wheeling circuit connected in parallel. The free-wheeling circuit comprises a series circuit, which includes a first diode and a first switching transistor connected in parallel to a non-linear resistor, connected in parallel to the coil. The first switching transistor is driven by a parallel circuit formed by a capacitor and a first ohmic resistor, which is connected in parallel to a second switching transistor. When a switch-off overvoltage appears in the coil, the second switching transistor becomes conductive and thus the first switching transistor is reliably blocked, so that the residual energy decays through the non-linear resistor.

Abstract: Disclosed is an exposure control device for a camera. The exposure control device has a magnetic plunger including a permanent magnet and a plunger coil. The plunger coil generates, when energized, a magnetic field which weakens a magnetic force of the permanent magnet. A resistor is connected in parallel with the plunger coil. Resistance of the resistor is substantially equal to a DC resistance of the plunger coil.

Abstract: A circuit arrangement for independently switching the induction coils of several d.c.-operated solenoid valves connected in parallel that, with a reduction of power loss, features a disconnection time which is independent of the voltage of the d.c. voltage source.

Abstract: A power distribution network including a voltage support transformer is disclosed which uses the fault current from a line of the power distribution network in which a fault condition exists to support or stabilize the voltage across one or more other lines of the network connected to the same bus and seeing the same source impedance, to maintain the voltage in those lines substantially at the pre-fault levels. The voltage support or stabilization in the unfaulted line is based upon a current change due to the impedance change in the faulted line caused by the fault.

Abstract: A solenoid valve driving device includes a bypassing current path of which one end is connected to a point between a first switching device and a first solenoid valve and another end is connected to a point between a second switching device and a second solenoid valve, and an element disposed in the bypassing current path and having a characteristic that causes current to flow from the first switching device side to a second switching device side. By adopting the above described constitution, through current generated when the first switching device is switched from an OFF-state to an ON-state during duty control of the first switching device can be suppressed by the inductance of the second solenoid valve. In this way, one solenoid valve among a pair of the first and second solenoid valves, which is not operated, has a function of suppressing the through current.

Abstract: The inductance-change detection apparatus comprises an inductance-change converter that converts inductance-change in coils into voltage to output, a reference-voltage generator that generates and outputs a predetermined reference voltage, a frequency characteristic adder that adds a frequency characteristic similar to that of the converted voltage converted by the inductance-change converter to the reference voltage, a reference-voltage compensator that varies and compensates the frequency spectrum of the reference voltage containing the added frequency characteristic, in parallel in the direction of amplitude, corresponding to a parallel variation of the frequency spectrum of the converted voltage in the direction of amplitude, and an inductance-change detector that compares the converted voltage with the compensated reference voltage to detect inductance changes in the coils.

Abstract: Inductive energy from the coil of an electromagnetic actuator is stored in capacitive network at a relatively high voltage when the actuator is deenergized. When the actuator is energized, the capacitive network is coupled to the coil thereby releasing the stored energy at a high voltage to the coil.

Abstract: A system for protecting an electronic device from electromagnetic radiation is provided that receives electromagnetic radiation impinging on said electronic device, determines a value of a characteristic of said electromagnetic radiation, generates a testing signal when said value of said characteristics of said electromagnetic radiation is greater than a predetermined value, and tests said electronic device in response to said testing signal to determine if said electromagnetic radiation has affected said electronic device. A method for protecting an electronic device from electromagnetic radiation is also provided.

Abstract: A safety system comprises separate safety circuits connected to a process to be safeguarded, each of which safety circuits are coupled to a data acquisition circuit via a retroaction-free element, which takes care of it that in the event of a malfunction occurring on the input of the data acquisition circuit, this malfunction will not affect the reliability and operational safety of each of the separate safety circuits.

Abstract: An automatic transfer switch for transferring a load between a normal power source and an alternate power source has a control circuit which senses the movement of the plunger of the switch-actuating solenoid into a position proximate the plunger stop or pole piece and then turns off power to the coil current so that the plunger can be restored to its rest position as the inertia of the switch enables completion of the transfer. Upon interruption of voltage to the coil, the coil is switched in series with a resistance which rapidly dissipates the residual current generated by the collapsing field within the coil to alleviate the braking effect of the residual coil current on the solenoid plunger.

Abstract: A solenoid driver circuit is controlled by an electronic control module ("ECM") and eliminates many components required for a high voltage power supply required by the prior art. The solenoid driver circuit includes a high voltage select switch, a select switch and a modulation switch that are controlled by the ECM. The ECM causes the switches to be opened and closed so that the back EMF created by the solenoid coil when the modulation switch is opened can be recaptured by charging a capacitor. That energy can then be used to energize the solenoid coil.

Abstract: In one embodiment of the present invention, across an electrical load to prevent over dissipation semiconductor switch in the event of a short circuit. The system includes a microprocessor with a terminal which is alternatively configurable as an input and as an output. When the terminal is configured as an output, the microprocessor can turn the electrical load ON and OFF via a transistor, under software control. Once the microprocessor turns the load ON, the microprocessor reconfigures its terminal to be an input. The system automatically latches the electrical load ON until a short circuit occurs or until the microprocessor turns the load OFF. When a short circuit occurs, the system automatically turns the load OFF. With the microprocessor terminal configured as an input, the microprocessor can detect when the system has automatically turned the load OFF due to a short circuit, thus being able to set a diagnostic code or take other appropriate action.

Abstract: A method of recognizing armature impingement in an electromagnetic actuator having an electromagnet including a solenoid, an armature movable toward and away from the electromagnet and return means for exerting a force on the armature. The method includes the steps of maintaining a solenoid current at a predetermined magnitude I.sub.max during a predetermined period T.sub.A for capturing the armature at the electromagnet; switching off the solenoid current at a moment t.sub.1 upon lapse of the period T.sub.A ; upon lapse of a period T.sub.1 running from moment t.sub.1, oscillating the solenoid current between a lower holding current threshold I.sub.H1 and an upper holding current threshold I.sub.H2 ; detecting a current course from moment t.sub.1 ; and deriving a signal from such current course.

Abstract: A method of switching an electromagnetic actuator which includes an armature movable along a path of travel and two electromagnets having respective solenoids, disposed at opposite ends of the path of travel for alternatingly attracting the armature. The method includes the steps of alternatingly applying a supply voltage to the electromagnets for alternatingly causing a supply current to flow therethrough for effecting a reciprocating motion of the armature; and applying an induced current, generated by an induced voltage appearing across one of the solenoids upon removal of the supply current from the one solenoid, to the other of the solenoids until the supply voltage applied to the other solenoid is greater than the induced voltage and the supply voltage across the other solenoid is capable of maintaining an attained current flow therethrough.

Abstract: A varying voltage is applied across a coil of a contactor. The varying voltage has a characteristic (frequency) which varies as a function of the position of the armature. The varying voltage is transmitted to a coupler which transmits information to a controller. The coupler may include one or more light sources (LEDs) which are sequentially energized and de-energized to sequentially render a phototransistor conducting and nonconducting. The frequency of the output from the coupler corresponds to the frequency at which the phototransistor is changed between the conducting and nonconducting conditions. A controller determines whether the frequency of the output from the coupler corresponds to the intended position of the armature of the contactor or to an unintended position by comparing the frequency of the output from the coupler to known frequencies for various positions of the armature.

Abstract: Transfer between alternative electrical power sources for highly inductive loads, such as motors, is made using an open transition with the load connected to the new source only after the voltage on the load bus has fallen below a predetermined value, preferably a value which is about 30% or less of the nominal source voltage.

Abstract: The present invention is concerned with a method and an arrangement relating to visual display units, preferably a picture tube (1), for reducing to a minimum the electrical alternating fields generated by the display unit in the unit surroundings. The visual display unit is provided with a voltage connected part (5) on which undesirable voltage variations occur. These voltage variations are indicated. A signal which is phase inverted in relation to the indicated voltage variations is generated. The generated phase-inverted signal is fed back to the voltage connected part (5), to compensate for the voltage variations.

Abstract: A low voltage power supply which uses a low voltage transistor in conjunction with a winding of an electric motor and the high voltage motor commutation transistors. The motor winding is energised by the commutation transistors for example during use of the motor, and the low voltage transistor is used to divert current from the energised motor winding at desired intervals to provide the low voltage power supply. The low voltage supply may be used in an appliance such as a laundry machine for supplying the motor control circuitry and auxiliary devices for example, a drainage pump and water supply control valves.

Abstract: A driver circuit for controllably connecting an inductive load to a source of electrical power in response to an input control signal is provided. The inductive load includes an inductive winding of a solenoid. The driver circuit controllably connects and disconnects the inductive load to and from the source in response to a first control signal and controllably provides a discharge path for a flyback current of the inductive load in response to a second control signal. The driver circuit senses both the energizing current and the flyback current and responsively provides an energization path and a flyback discharge path in a non-overlapping manner.

Abstract: In an electrical power system for a residential building, a multi-conductor cable supplies power to loads in the residential building from a power supply. A net current returning from loads to the power supply via alternative conductive paths different from the neutral conductor in the cable creates a magnetic field in the vicinity of and inside of the residential building. A net current control device, including a ferromagnetic core, is attached to the multi-conductor cable in order to increase the impedance of the alternate conductive paths to the net current and to increase the net current flowing along the neutral conductor. Various modifications of the net current control device are disclosed.

Abstract: A circuit device for recovering energy from an inductive load is connected to a protection circuit for protecting a driver circuit from a charge contained in the inductive load. The inductive load is connected between a power supply line at one end and the driver circuit and protection circuit at another end. The circuit device has a charge accumulator, preferably a capacitor, connected to the protection circuit for accumulating charge from the inductive load. A control circuit monitors the level of charge in the capacitor. A switch, connected between the capacitor and the power supply line, permits the charge accumulated in the capacitor to discharge into the power supply line. The control circuit controls the switch so as to permit the intermittent discharge of the inductive load: the switch is opened to permit charge from the inductive load to accumulate in the capacitor; and, the switch is closed to permit the capacitor to discharge the accumulated charge to the power supply line.

Abstract: A bridge circuit, intended for use as a PWM driver of an inductive load, includes at least one source driver transistor connected in series totem-pole fashion with a sink driver transistor. A base resistor is connected from base to emitter of one of the driver transistors. This totem pole circuit is connected across a pair of DC supply conductors. A protective fly-back diode is connected across the one driver transistor. An auxiliary resistor is connected from the base of the auxiliary transistor to the emitter of the one driver transistor. When a fly-back diode across the one driver transistor conducts, the one driver transistor tends to conduct in the reverse direction and to store charge that in a subsequent period leads to shoot-through currents through the source and sink drivers.

Abstract: A damping circuit includes two circuits. Each circuit has a PNP transistor, an NPN transistor, and a shunt resistor. The PNP transistors are connected in series to the NPN transistors through level shift stages. The PNP transistor and the NPN transistor have emitter functions of the same area. The shunt resistors are connected to the emitters of the NPN transistors. Both of the two circuits are connected to a coil in parallel in such a manner that the two circuits have opposite polarities to each other about the coil.

Abstract: A circuit in which the source-to-drain conduction path of a power switching transistor is connected in series with an inductive load between first and second power terminals includes a voltage transient clamping transistor having its source-to-drain conduction path connected between the drain and gate of the switching transistor. In response to a turn-off signal applied to the gate of the switching transistor, a transient voltage is generated at the drain of the switching transistor. When the transient voltage at the drain of the power switching transistor exceeds a predetermined value, the clamping transistor is turned-on. The conduction of the clamping transistor limits the voltage rise at the drain of the switching transistor and tends to maintain the switching transistor conducting temporarily to aid in the discharge of the energy stored in the inductive load.

Abstract: An apparatus and method are adapted for detecting an end-of-fill condition of an actuator having a varying control volume is provided. The end-of-fill condition corresponds to the varying control volume being pressurized to a predetermined end-of-fill pressure. The apparatus comprises a solenoid having a coil and an armature. The armature is movable relative to the coil in response to energization of the coil. A valve delivers a flow of fluid to the actuator. The fluid flow having a rate responsive to the movement of the armature. The apparatus and method controllably energizes the coil with a control current. The apparatus and method detects a flyback current in the coil, detects a change in the level of noise in said flyback current, and responsively producing an end-of-fill signal in response to the change being greater than a predetermined threshold.

Abstract: An apparatus for energizing the coil of, and detecting the resultant armature actuation in, a solenoid of the type having a movable armature reciprocable along an axis between first and second positions, a spring bias normally biasing the armature toward the first position, and an actuating coil for inducing a force on the armature tending to move the armature from the first position toward the second position in response to current flow in the actuating coil. A voltage is first provided to the solenoid coil and thereafter, a resulting current flow is differentiated and a zero crossing comparator is utilized to determine when the differentiated current is zero and, therefor, the time at which the sensed current flow reaches a maximum (dv/dt=0). The time at which the armature began to move in response to the resulting coil current may be inferred and the voltage to the solenoid coil interrupted a Predetermined time after the time at which the armature began to move.

Abstract: In a switching transistor control circuit, the switching transistor has a control electrode and first and second main circuit electrodes. A reactor is connected in series with the first main circuit electrode of the switching transistor to receive a main circuit current through the switching transistor. Circuitry is connected to an end of the reactor remote from the first main electrode and to the control electrode of the switching transistor, for supplying an electromotive force to the control electrode which is generated by the reactor as main circuit current decreases when the switching transistor is turned off. A control electrode driving circuit is connected to the control electrode, and is connected to one of the first main circuit electrode and a predetermined intermediate position on the reactor, for supplying a drive signal to the control electrode for selectively turning the switching transistor on and off.

Abstract: A polyphase electric power distribution system is protected from the effects of geomagnetic storms by countering the difference of potential between spaced grounding points in the system, and or by altering the magnetic circuits of transformers in the system to reduce half-cycle saturation and associated high peak currents.

Abstract: A polyphase electric power distribution system is protected from the effects of geomagnetic storms by countering the difference of potential between spaced grounding points in the system, and or by altering the magnetic circuits of transformers in the system to reduce half-cycle saturation and associated high peak currents.

Abstract: A circuit capable of driving inductive loads below a chip substrate voltage level while minimizing on-chip power dissipation and eliminating parasitic effects. Two negative voltage drive modes are included in the circuit design. The first drive circuit forces a low negative voltage referenced to the circuit output voltage across an inductive load referenced to ground to provide a slow recirculation of the current in the inductive load. The second drive circuit forces a large negative voltage referenced to the circuit output voltage across the inductive load to provide a fast collapse of the inductive load. The switching regulator switches off when the current to the inductive load reaches a first value and switches on when the recirculating current from back e.m.f. reaches a second value. The switching regulator initially provides a higher level of power when first tuned on.

Abstract: An apparatus is adapted to detect an end-of-fill condition of an actuator having a varying control volume, C. The apparatus includes a solenoid having a coil and an armature. The armature is movable relative to the coil in response to energization of the coil. A control valve delivers a flow of fluid to the actuator. The rate of the fluid flow is responsive to the movement of the armature. An electrical circuit detects a voltage spike across the coil and responsively produces an end-of-fill signal. The voltage spike is generated by an electromotive force produced by the armature in response to the control volume achieving a predetermined end-of-fill pressure.

Abstract: An arrangement for injecting fuel for an internal combustion engine has at least one inductive injection valve which is switch controlled via a controllable semiconductor switch. This injection valve is provided with an inductive or capacitive oscillator component for atomizing fuel. During the switching control operation, electrical energy from the inductive injection valve is fed into the oscillator component for exciting its oscillating movement each time the semiconductor switch is opened. On the one hand, with this arrangement no separate high frequency generator is required for the oscillator component while, on the other hand, a second transistor is not required for the switch-controlled output stage with a rapid discharge without loss being possible at least in principle.

Abstract: A driving circuit for driving a solenoid pump or the like, wherein a driving current supplied from a rechargeable battery 1 is alternately switched to on and off when flowing in an inductive element 2. The inductive element produces a driving force applied to the solenoid pump when the driving current flows therein. The inductive element generated a counter-electromotive force when the driving current flowing therein is interrupted. An accumulating circuit comprising a capacitor 5 is connected to the inductive element to accumulate the counter-electromotive force, and a releasing circuit 4 is connected to the accumulating circuit to release the counter-electromotive force accumulated in the accumulating circuit. The counter-electromotive force released from the releasing circuit produces a superfluous driving current and the latter current is superposed on the driving current supplied form the battery.

Abstract: There is disclosed an improved output circuit for use with a differential line driver which drives a parallel inductance and resistance load coupled across the line driver output. The output circuit substantially reduces the kickback voltage produced across the load which results from a residual magnetizing current being stored in the load inductance. The output circuit includes an impedance means which is coupled across the output terminals and a common mode current source coupled between the impedance means and a common potential for sinking a portion of the residual magnetizing current to reduce the amount of residual magnetizing current flowing through the load resistance.

Abstract: An energy recovery system for an electrotherapy device, particularly for bone healing, which permits the device to be small, light and portable, and to have extended battery life. Included are a drive voltage source and a ground reference potential. Driving transistors are between an inductive load and, relatively, the voltage source and ground potential, with a storage capacitor connected between the latter two. The voltage source is commonly a battery, preferably a zinc-air battery. Induction load power is applied when both transistors turn on simultaneously. For energy recovery, diodes are connected between the first terminal of the inductive load and the ground potential and between the second terminal of the inductive load and the high voltage source, such that they are reversed biased when the drive transistors are conducting. When drive power is removed from the inductive load by switching off the drive transistors, a reverse EMF is established in the inductive load.

Abstract: A circuit and method which eliminates the voltage spike generated by inductive kick, and generates a signal which is active while a relay is being released and for a given period thereafter. This signal can be used to power down circuits supplying signals to relay contacts, thereby allowing the relay to release without current or voltage potentials at its contact, e.g. dry switching. The generated signal may also be used to disable sensors which might give false indications while the relay contacts are switching. In telephone line circuits, the generated signal can be used to disable the telephone hook switch detector or to power down the battery feed circuit feeding the subscriber line. The relay coil energy generates a signal which is active while the relay is being released. The invention uses a minimum number of components and the circuit is adjustable as to how long the generated signal remains active after the relay is released.

Abstract: An apparatus for protecting an integrated circuit from reverse voltages caused by an inductive load. An integrated circuit (397) drives a relay (411). A first diode (407) is used in a conventional manner to limit the reverse voltage generated by the relay (411). A second diode (410) further suppresses the reverse voltage and protects the integrated circuit (397).

Abstract: A bistable electromechanical transducer is disclosed having an armature reciprocable between first and second positions, a permanent magnet latching arrangement for maintaining the armature in the respective positions, and an electromagnetic repulsion arrangement operable when energized to dislodge the armature from the position in which the armature was maintained and causing it to move to the other of the positions. In a preferred embodiment, the transducer takes the form of an electronically controllable valve mechanism for use in an internal combustion engine and has an engine valve with an elongated valve stem along with the electromagnetic repulsion arrangement for causing the valve to move in the direction of stem elongation between valve-open and valve-closed positions.

Abstract: An operation confirming device for electromagnetic actuator according to the present invention is applied to an electromagnetic actuator comprising a stationary core, a movable core facingly arranged with respect to the stationary core so that the movable core can be moved close to or apart from the stationary core and formed in a closed magnetic circuit together with the stationary core, and an electric coil wound around the closed magnetic circuit. This operation confirming device is provided with a movable core shift detector for detecting time when shift operation of the movable core with respect to the stationary core by applying DC current to the electric coil is completed, by means of transitional fluctuating wave of the applied DC current. This operation confirming device is simply constructed, so that it can be formed in a compact size and a light weight with low manufacturing cost, and the reliability of operation confirming for electromagnetic actuator can be improved.

Abstract: A speaker system especially designed to improve the characteristics of low sound bands. The speaker system desirably includes a partition dividing the interior of a cabinet into a speaker chamber and a resonance chamber, and two radiation ports. One radiation port is formed on the partition and the other one on the walls of the resonance chamber which do not face each other.

Abstract: An electromagnetic drive circuit comprises a coil for detecting and driving a permanent magnet; a comparator for generating an output when the induced voltage of the coil exceeds a reference voltage; a pulse generator for generating a drive pulse train in response to generation of the output of the comparator; a driver responsive to the drive pulse train for feeding a drive current to the coil; and a controller responsive to interruption of the output of the comparator for interrupting generation of the drive pulse train of the pulse generator. The permanent magnet is detected and driven by the single coil so that the output may be generated by the comparator when the induced voltage of the coil exceeds the reference value, and the drive pulse train is generated during generation of that output to feed the drive current to the coil. The coil can always be efficiently driven at the maximal point of the induced voltage, and the permanent magnet can be driven with a stable amplitude.

Abstract: Herein disclosed is an electromagnetic drive circuit for driving a pendulum or the like, comprising: a coil for detecting and driving a permanent magnet; a reference voltage source having a variable reference voltage; a comparator for generating an output when the induced voltage of the coil exceeds the reference voltage; a pulse generator for generating a drive pulse in response to generation of the output of the comparator; a driver responsive to the drive pulse for feeding a drive current to the coil; and a controller responsive to the output of the comparator for controlling the reference voltage in accordance with the amplitude of the induced voltage. It is possible to integrate the most of construction and to eliminate the disadvantage of generating the drive pulses at the level of the induced voltage other than its maximal point so that the automatic control can be accomplished to effect the drive efficiently at the maximal point of the induced voltage at all times.

Abstract: In a disk memory library, picker arms, operated by a solenoid, are used to remove a selected disk from a library stack of disks and to place the disk in a reading/writing environment. The solenoid plunger's position is determined by noting its effect on a series resonant circuit that is formed with the coil inductance of the solenoid coil and a series capacitor. A function generator provides a triangular signal to the solenoid coil. An amplifier and peak detector are coupled to the coil to amplify and peak detect the voltage signal across the coil. A threshold detector, coupled to the output of the peak detector, is set to provide a digital output indicating when the solenoid's plunger is in or out. The function generator also provides a square wave that is synchronized to the triangle wave and is coupled to sample the output from the threshold detector. The change in the coil's inductance causes a phase shift in the triangle wave which further accentuates the voltage difference appearing across the coil.

Abstract: A driver circuit for the coil in relay contains a suppressor diode across the coil terminals. Two light-emitting diodes are connected in reverse polarity so that one diode operates when the coil is energized and the other diode operates if there is current flowing in the reverse direction when the suppressor diode fails to clamp the coil voltage. The diodes may be of different colors and may be positioned close to each other to produce the composite color when they are energized at the same time or in rapid succession.

Abstract: Power recovery circuit for printer haivng printing elements actuated by electromagnets energized by a voltage VS available at a terminal. The circuit includes a voltage booster for generating a voltage HV higher than voltage VS at a node and a buffer capacitor charged by the voltage HV and connected between the terminal and the node, a connection between the electromagnets and the node for transferring the magnetic energy imparted to the electromagnets by the buffer capacitor for storing therein as capacitive energy, an inductor and a control switch, series connected between the node and the terminal, a recirculation diode connected between ground and the node common to the switch and the inductor, a voltage detector providing an enabling signal when voltage HV exceeds a predetermined level and a controlled oscillator, enabled by the enabling signal to generate a control signal which periodically switches the control switch on and off.