A voltage-doubler rectifier includes an ac fullbridge diode rectifier and a dc-to-dc converter having two output boost circuits. One of the output boost circuits is coupled between the rectifier and a dc link, and the other output boost circuit is coupled, with opposite polarity, between the rectifier and the circuit common. Two series-connected filter capacitors are also coupled between the dc link and the circuit common. In a preferred embodiment, the two output boost circuits each comprise either a series, parallel, or combination series/parallel resonant circuit and a rectifier. A switch is coupled between the junction joining one pair of diodes of the rectifier and the junction joining the two filter capacitors. For a relatively high ac line voltage, the switch is open, and the circuit operates in a low boost mode. For a relatively low ac line voltage, the switch is closed, and the circuit operates in a high boost, or voltage-doubling, mode.

High power factor, voltage-doubler rectifier

An off-line switching power supply includes an ac rectifier and a dual-output switching converter having one output coupled between the ac rectifier and the input to the dual-output converter in order to provide a high power factor, the other output of the dual-output switching converter providing a dc voltage as the power supply output. The outputs of the dual-output converter are fully decoupled so as to allow independent control of the ac input current and the power supply output voltage. In a preferred embodiment, a full-wave ac rectifier bridge is coupled in series with the second output of the power converter via an input resonant boosting converter. A full-bridge dc-to-ac converter is coupled between the dc link and ground for providing an ac signal to excite the boosting converter and for providing another ac voltage through a transformer to an output rectifier to generate a regulated dc output voltage. The amplitude of the regulated output voltage is controlled by pulse width modulation, while active frequency control of the boosting converter is provided to control the amplitude of the ac input current. Alternatively, frequency control of the boosting converter is passive, i.e., depends on the gain characteristics of the boosting converter resonant circuit. As a result of the complete decoupling of the input boosting converter and the power supply output voltage, the off-line switching power supply is capable of drawing high quality current waveforms from the ac source while producing a regulated dc output voltage with fast transient response.

High power factor power supply

A single power converter is capable of drawing low distortion current from an AC line and delivering DC or AC power to a load. The single power converter is used to independently control the input current and the output current. The power converter transformer has an output winding which is controlled by pulse-width modulation (PWM) and a frequency controlled boost winding for controlling input current.

Power circuit with high input power factor and a regulated output

A battery management system for managing the voltage of a battery cell, such as a lithium ion battery, is disclosed. The battery management system comprises a semiconductor switch coupled to the battery cell, wherein the semiconductor switch is in an on condition when the voltage across the battery cell exceeds a first threshold voltage, and a microprocessor coupled to the semiconductor switch, wherein the microprocessor monitors the voltage across the battery cell when the semiconductor switch is on, and turns itself off when the when the monitored voltage is less than a second threshold voltage, thereby preventing further current drain from the battery cell.

System for preventing deep battery discharge

A circuit arrangement for supplying a load, e.g. an X-ray tube, with a pulsating voltage by means of a DC voltage source connected in series with the load and a controllable rectifier, which is extinguished by means of the charge on a commutating capacitor, which, via a current transformer, is charged by the leading edges of the load current, and the discharge of which is controlled, via a timing device, by the voltage across the commutating capacitor. Means may be provided for reducing the time constant of the timing device when the load current exceeds a given value.

Circuit arrangement for transforming the voltage of a dc voltage source into a pulsating voltage

AC mains voltage is full-wave rectified and applied to a storage capcitor 22 providing input to an inverter 24. The voltage applied to the capacitor is maintained above the peak mains voltage by an additional voltage which is applied to the output of the rectifier 20. The additional voltage is produced by a second rectifier circuit 50 fed with a high frequency input from a transformer 42 having its primary 44 across the inverter output. The additional voltage is applied by a filter 76, 74. The signal from the transformer is modulated by PWM by the action of a control circuit 70 which governs the firing of the SCR's 52, 54. The control circuit uses error signals including a signal representing the difference between the actual current waveform and a predetermined waveform to ensure that the waveform of the current drawn from the mains 10 is as required e.g. sinusoidal and in phase with the mains voltage.

Power supply circuit

An electrical power switch comprising two transistors (1 and 2) in Darlington connection and a transformer (4) of which the primary (5) is in series with the collector/emitter circuit of the second transistor (2) and the secondary (6) is connected in series with the collector/emitter circuit 9 the first transistor in such a way that when current flows in the primary a current is induced in the secondary in a sense which accords with the current already flowing therein, and the voltage that appears across the secondary is in a sense which reduces the collector/emitter voltage of the second transistor, thus also reducing power loss. The winding ratio is chosen so that when current flows the second transistor is always in saturation. Further embodiments show two of these transistor pairs connected in series (Fig. 3), and parallel (Fig. 4), being switched on and off alternately such that the magnetic flux is reset in each secondary when the associated pair is off. Also there is an embodiment wherein the magnetic flux is reset by load current (Fig. 5) which free-wheels when the switch is off.

Darlington transistor switch.

950,734. Control of D.C. motors. SMITH'S DELIVERY VEHICLES Ltd., H. W. HEYMAN, and J. HAMBLETON. May 29, 1961 [March 1, 1960; Aug. 20, 1960; March 11, 1961], Nos. 7245/60, 28893/60 and 8975/61. Heading H2J. [Also in Divisions G3 and H3] A control system for a battery-operated electric traction motor comprises a variable frequency pulse generator, the pulses from which are used to trigger a gated diode which in turn controls the motor current. Closure of switch S1 charges capacitor CE through silicon controlled rectifier SCR3, cutting off transistors Q3, Q4. Rectifier SCR3 remains conductive, however, until the charging current through capacitor CE decreases to a predetermined value. Capacitor C1 commences to charge, at a rate determined by the value of resistor VR coupled to an accelerator pedal, until it is discharged by transistors Q1, Q2, into the gates of rectifiers SCR1, SCR2. The battery voltage is then applied across the motor circuit, and the capacitor CE discharges inductively through the elements SCR1, SCR2, L1 and D3, so reversing the charge across capacitor CE. Capacitor C2 discharges at a rate determined by resistor R1 until transistor Q4 renders rectifier SCR3 conductive and the reverse potential held by capacitor CE turns off the rectifiers SCR1, SCR2. The capacitor CE then recharges in the original direction and the cycle is repeated. Motor current is maintained by diode RD2 during the interpulse period. Fluctuations in the battery voltage produce an inductive effect and tend to reduce the stored charge on capacitor CE, so preventing turn-off of the rectifiers SCR1, SCR2. The inclusion of diode RD1 ensures that the stored charge on capacitor CE is not reduced by the battery transients. For battery charging purposes, the points A, B, C and D are connected as shown in Fig. 2, the rectifiers SCR1, SCR2 serving for both speed control and battery charging. The battery is supplied through mains transformer T, an auxiliary winding of which supplies a bridge rectifier whose output is clipped by Zener diode Z. Potentiometer P controls the potential applied to transistor Q1 for charging capacitor C1 until transistors Q4, Q5 produce a sharp pulse. This pulse fires the rectifiers SCR1, SCR2, which are switched off automatically at the end of the half cycle. By varying the setting of potentiometer P, the time delay of the pulse from the start of the cycle can be changed. Current feedback from resistor R1 to transistor Q3 modifies the phase of the firing pulse. When charging is complete, a voltage sensitive relay actuates switch S to raise the potential of the base of transistor Q4, so delaying the pulse.

Improvements in or relating to control means for electrical apparatus

1,114,102. Supply systems for consumption apparatus. SEVCON ENGINEERING Ltd. 31 Jan., 1967 [3 March, 1966], No. 9258/66. Heading H2H. [Also in Division G3] A circuit arrangement for producing from a direct voltage of one value a direct voltage of another, lower, voltage comprises means for chopping the original voltage into pulses which may have a variable frequency or a variable width. A direct voltage is applied at terminals X and a lower voltage is taken from terminals Y, the chopping function being effected by two controlled rectifiers SCR1, SCR2. Conduction of SCR1 causes capacitor C1 to charge by way of inductor L, a further capacitor C2 being charged at the same time. When the capacitor C2 is fully charged, SCR2 fires after a time delay determined by a delay unit TD, thus causing SCR1 to be extinguished. After a further period determined by a variable unit FB, SCR1 refires, extinguishing SCR2 and the cycle is then repeated, the output direct voltage being the mean of the pulses which are produced. The arrangement produces pulses having a constant width and a variable frequency. In a further embodiment the units FB, TD are associated with SCR2 and SCR1 respectively and with this arrangement the pulses have constant frequency but variable width. The arrangement is suitable for producing a voltage for the headlights of a vehicle driven from a higher voltage supply.

Direct current transformation

1,271,497. Preventing over discharge of batteries. SEVCON ENG. Ltd. 30 April, 1969 [17 May, 1968], No. 23636/68. Heading H2H. [Also in Division G1] A battery discharge indicator incorporates a battery voltage sensing circuit which responds to the fall of battery voltage below a predetermined value to actuate an indicator, the system incorporating a switch which is actuated by a magnetic field generated by the battery current when this is above a given value so as to prevent actuation of the indicator. This ensures that the indicator will not be operated during temporary voltage drops due to heavy surge currents. In one arrangement (Fig. 1) a determined proportion of the voltage of battery 4 being monitored is tapped from resistor 15 and applied to one transistor 9 of an emitter coupled pair 7, 9. The other transistor 7 has a standard voltage from a Zener diode 1 applied to its base. Any changes due to temperature effects in the base-emitter voltage of 9 are compensated by similar changes at 7. If the battery voltage falls below a predetermined level, transistor 9 is switched off, current through the winding 13 ceases, and a pair of reed relay switch contacts controlled by the winding open. If however, there is a high current surge in the battery circuit to the load 6, a large field is produced in the winding 21 to hold the contacts closed. The contacts are used to control the operation of an indicator. In a second embodiment (Fig. 2) fall of the battery voltage is used to set a relaxation oscillator into operation. A proportion of the battery voltage is applied to the base of a transistor (37) whose emitter is normally held at the potential across a capacitor (43) charged from a Zener diode circuit (45). When the base voltage falls below the emitter, the transistor conducts and switches on a second (39) coupled back to the first so that the capacitor discharges and eventually prevents the first transistor conducting again. These oscillations are amplified and applied to a warning lamp (57). Heavy current flow in the battery circuit is used to operate a pair of contacts (61) across the warning lamp so that it is by-passed under surge current conditions. The first arrangement may be incorporated in a battery operated fork lift truck, operation of the contacts preventing the lift circuit from being operated.

Gurwicz David

Papers

Power supply circuit

Darlington transistor switch.

Improvements in or relating to control means for electrical apparatus

Direct current transformation

Improvements in or relating to battery discharge indicators