Abstract: An exchanging converter includes a zero-voltage switching control circuit, which drives an output voltage filter capacitor to partially feed back storage energy to an input side thereof by means of the operation of a transformer (or storage inductor), and provides a complementary driving signal to switches in the exchanging converter when the switches reaching a zero-voltage switching control condition, so as to control turn off or turn-on time of the switches, enabling the switches to repeat the switching operation at zero-voltage again and again.

Abstract: The invention is a load voltage and power control and supply system for the supply of power to a load for which, over particular periods of time, usually on a daily basis, it is desired to reduce power. The invention has particular application to street lighting systems in which, for a period of several hours during the night (when traffic is minimal and many people are asleep), the luminaires of the lighting system can operate at reduced power. The power control system is able to act as a voltage stabilizer as well as a controlled power reduction system. The power control system may operate the bank of spaced luminaires from a single control location. Moderately reduced power (say a 30% reduction in power) supplied to luminaires does not noticeably diminish the adequacy of the illumination provided. Further, the power control system reduces power in stepwise decrements each of which reduces power by a small amount insufficient to diminish noticeably the ambient illumination.

Abstract: A frequency sensing NMOS voltage regulator is disclosed. A NMOS source follower transistor has a gate connected to a predetermined gate voltage, a drain coupled to an external supply voltage through a PMOS switching transistor, and a source connected to a load. The gate of the PMOS transistor is controlled by a delay circuit through which a pulse derived from the system clock is passed. Through the use of the delay circuit and the PMOS transistor, the amount of current produced by the NMOS transistor is made a function of the cycle rate of the system clock and the current provided by the NMOS transistor tracks the frequency-dependent current requirements of the load, resulting in a reduced variance of the supply voltage Vcc over a wide current range.

Abstract: An apparatus for converting a direct current into an alternating current comprises a direct-current converter having an input and an output, which direct-current converter is continuously controllable, a capacitor, and a control unit for controlling the direct-current converter. The apparatus furthermore comprises a second direct-current converter having an input and an output, wherein the input of the second direct-current converter is connected in parallel to the input of the first direct-current converter and the outputs of the first and the second direct-current converter are connected in series. An unfolding bridge is connected to the series-connected outputs of the direct-current converters, whilst the capacitor is connected to the output of the second direct-current converter.

Abstract: A hybrid regulator in which a switching regulator and a series regulator are inter-connected in a desired manner. In the hybrid regulator, most of current required for a load is supplied from the switching regulator which has a poor regulation performance while having high efficiency. The hybrid regulator also includes a sensing unit for the rapid sensing of the current supplied to the load. Based on the operation of the sensing unit, the series regulator, which has a poor power efficiency while exhibiting a excellent regulation performance, supplies or absorbs only a small amount of ripple current. The series regulator serves as an independent voltage source whereas the switching regulator serves as a dependent current source. Accordingly, the hybrid regulator ensures a superior regulation performance while achieving high efficiency.

Abstract: A synchronizer module for a multivoltage power supply having at least two output rails, and comprising a respective voltage monitor having a first input coupled to each of the output rails for monitoring a supply voltage thereon and providing an enable signal on an output thereof when the supply voltages on all of the output rails reach a respective in-tolerance condition. A switching element connected in each of the output rails and is responsive to the enable signal for changing from a first open state to a second closed state.

Abstract: A system for delivering power to a battery and to a load includes a power source that supplies energy to the battery and the load. The battery can be charged by the power source and used to supply energy or power to the load when the power source is unable to provide sufficient energy and power to the load. The system reduces injection of DC current into the load and, as a result, extends the operation life of the load, particularly if the load is an AC lighting or lamp system. The system operates the load in an optimal manner such that battery storage is maintained at near full charge, yet the lighting load operates for a maximum number of hours per night. The benefit of the system is to prevent early failure of either the lighting load or the battery.

Abstract: A circuit includes a plurality of DC-to-DC converter circuits and separates in time switching of the respective power switches of the DC-to-DC converter circuits which would otherwise be switching at nearly a same time, such as based upon a same desired output level. The switching time may be separated by inverting a periodic control waveform of at least one of the DC-to-DC converter circuits. The multiple output DC-to-DC converter circuit thereby provides an increased noise margin and operates with greater accuracy and stability. The circuit may also determine when the DC-to-DC converter circuits would otherwise be switching at nearly the same time, and activate the switching time separation responsive thereto. For example, the determination may be made based upon a selectable output level being within a predetermined range of at least one other output level.

Abstract: A load controller and method are provided for maximizing effective capacity of a non-controllable, renewable power supply coupled to a variable electrical load also coupled to a conventional power grid. Effective capacity is enhanced by monitoring power output of the renewable supply and loading, and comparing the loading against the power output and a load adjustment threshold determined from an expected peak loading. A value for a load adjustment parameter is calculated by subtracting the renewable supply output and the load adjustment parameter from the current load. This value is then employed to control the variable load in an amount proportional to the value of the load control parameter when the parameter is within a predefined range. By so controlling the load, the effective capacity of the non-controllable, renewable power supply is increased without any attempt at operational feedback control of the renewable supply.

Abstract: A booster circuit is provided that inhibits the operation of a foldback cent limited power supply during its turn-on phase so that a load may be power to its full output voltage and at the same time retain foldback current limiting during normal operation so that the benefits of short circuit protection are retained.

Abstract: A low-noise switching regulator and a method for driving an inductive load, employing current slew control and voltage slew control, is provided. Open and closed loop embodiments, as well as first and higher order slewing, are also provided.

Abstract: A voltage stabilizer, having at least one supply-voltage input and at least one load-voltage output, has an in-phase regulator which is connected between the supply-voltage input and the load-voltage output. Provision is made for at least a first switching element, by means of which a first resistor is switchable in series to the in-phase regulator.

Abstract: A power conversion architecture includes one control capable of simultaneous operation with multiple power conversion circuits. The function of the controlling mechanism includes an output signal proportional to one or more inputs to the controlling mechanism for the purpose of maintaining a destination level at a substantially constant value. The function of each power conversion path is to transfer power from a source to a destination in an amount dictated by the controlling mechanism. The function of the parallel power conversion architecture is to proportionally distribute the power transfer between all power conversion paths.

Abstract: A dual adjustable voltage regulator combining a DC--DC switching regulator with a linear regulator implemented on a single chip is disclosed. The invention provides switching circuitry that can select between a fixed output voltage level and a user-adjustable output voltage. The circuit further provides means to automatically detect and generate power supply voltage levels as required by the system.

Abstract: Switching power supply circuit of the invention is provided with an nMOS transistor (Q1) and a pMOS transistor (Q2) connected in parallel inversely for switching an input DC voltage, and a driving circuit (3) for switching the nMOS transistor (Q1) when the duty-cycle is small and the pMOS transistor (Q2) when the duty-cycle becomes large. Therefore a stable output voltage can be obtained through the pMOS transistor (Q2) against fall of the input DC voltage supplied from a battery until its available limit determined by on-resistance of the pMOS transistor (Q2), while the stable output voltage can be obtained with minimum driving loss through the nMOS transistor (Q1) having smaller input parasitic capacitance compared to the pMOS transistor (Q2), when the input DC voltage is sufficiently high.

Abstract: A photovoltaic module capable of being oriented by hand with respect to the sun including an electrically activated display device for generating a visual informational display which indicates at least the power generating effectiveness of the module for its instantaneous orientation with respect to the sun, and an array of photovoltaic cells for generating a first power output for a load and a second power output for activating the display device and a third power output signal for the display device indicating the power generating effectiveness of the module.

Abstract: The fast transient load corrector is a circuit that attaches to the output terminals of a switching converter. Requiring no feedback circuit that interacts with any control parameter of the switching regulator, the fast transient load corrector works independently to improve the transient response of any switching regulator. Effectively the fast transient load corrector combines with the actual load to form a slowly varying composite load which permits the switching converter to maintain a well regulated output voltage or a voltage of pre-defined waveform. The conceptual construction consists of a bi-directional controlled current source and either a voltage sensor or a current sensor. The voltage or current sensor measures the amount of load disturbance and triggers the bi-directional controlled current source to supply transient current to the load. The quantity to be sensed can be the output voltage, the rate of change of the output voltage, or the rate of change of the output current.

Abstract: An integrated circuit has an on-chip voltage regulator circuit. The voltage regulator circuit includes a control circuit, a pass element and a control connection and also provided is a connection for connecting an external pass element to the voltage regulator. There is a switch circuit that when an external pass element is connected to the voltage regulator, the switch circuit will turn off the internal pass element.

Abstract: A voltage-to-current converter configured to operate over substantially the entire range of a power supply voltage signal that is employed to drive the voltage-to-current converter. A closed-loop voltage-to-current converter is configured to provide a first output current signal substantially linearly responsive to a predetermined range of an input voltage signal having values between the low voltage level of the power supply and a predetermined reference voltage signal. An open loop voltage-to-current converter is coupled to the closed-loop voltage-to-current converter. It is configured to provide a second output current signal, substantially linearly responsive to a predetermined range of input voltage signals, having values ranging between the reference voltage level and the high voltage level of the power supply. The first and second output currents are combined to provide the output current signal of the voltage-to-current converter.

Abstract: Circuits and methods are provided for low drop-out operation of switching regulator circuits that include a switching transistor and an output circuit adapted to supply current at a regulated voltage to a load. The circuits and methods generate a limiting signal that allows the switching transistor to remain in a continuous conductive state for a predetermined number of oscillator cycles. The predetermined number of oscillator cycles is preferably set by a counter that initiates a signal that turns the switching transistor OFF.

Abstract: A first power source for providing a positive voltage and a second power source for providing a negative voltage are selectively activated to supply a positive or a negative voltage to a load. A rectifying element is connected between the first and second power sources to prevent electric current from flowing through the second power source when only the first power source is active. A switch and a resistor for generating a feedback current are connected in series with an output terminal of the first power source and a terminal of the load. The switch is opened to prevent current flow through the resistor when only the second power supply is active.

Abstract: An apparatus and method for providing dynamic voltage regulation for a system with a fluctuating current demand are disclosed. A first voltage regulator is used for producing regulated output to the system. A control circuit activates a second voltage regulator with faster transient response than the first voltage regulator to help source current when the first voltage regulator is unable to adequately respond to an increase in current demand from the system. The control circuit activates a load element to help sink current at the output of the first voltage regulator when the first voltage regulator is unable to adequately respond to a decrease in current demand from the system.

Abstract: A direct current or direct voltage power supply operating from a mains AC line is corrected for power factor so that the maximum power can be extracted from the source. The AC line is full-wave rectified, filtered and the resulting pulsating direct voltage is applied to a buck/boost switched inductor switched at a frequency higher than the line frequency. The buck/boost switching action is controlled so that the switchover between buck and boost modes occurs when the instantaneous value of the pulsating direct voltage equals the supply output voltage. The inductor current in the buck mode of operation is controlled to have an input voltage-squared characteristic; the inductor current in the boost mode is controlled to have an input voltage-proportional characteristic. The resulting average current makes the AC line current substantially proportional to the AC line voltage, to achieve substantially unity power factor.

Abstract: The voltage regulator includes two sections, a switching regulator section (12) for regulating a voltage from an input (10) to an intermediate node (14). This voltage on the intermediate node (14) is then regulated with a linear regulator down to a regulated output voltage on an output node (18). The linear regulator includes a pass transistor (16) that is controlled by a linear regulator control (50). Linear regulator control (50) is operable to sense the voltage across the transistor (16) and perform multiple functions. First, it controls the pass element transistor (16) to regulate the voltage from the node (14) to the node (18) in a linear manner. Second, it controls the switching regulator section (12) to provide a regulated voltage on the node (14). Third, it controls the level of the voltage on the intermediate node (14) such that it is at a predetermined voltage level above the voltage on the output node (18), such that the power dissipation through the pass element transistor (16) is minimized.

Abstract: The power supply control device comprises two regulating modes, linear regulation and chopping regulation. A current from a sensor, rectified by diodes, supplies a power supply circuit comprising a storage capacitor and a regulating transistor. A resistor and a control circuit measure the value of the current and select the regulating mode via a selector. If the current is lower than a preset threshold regulation is linear, the base of the transistor is connected to a Zener diode. When the current exceeds a preset threshold regulation is chopped and the base of the transistor is connected to the output of a comparator.

Abstract: A power supply for a portable telephone, includes a battery pack comprised of at least one battery cell providing an unregulated output voltage; a boost/buck switcher connected with the battery pack for boosting/bucking the output voltage to a different level; a first regulator connected with the boost/buck switcher for regulating the boosted/bucked output voltage to produce a first regulated voltage; a second regulator connected with the boost/buck switcher for regulating the boosted/bucked output voltage to produce a second regulated voltage having a voltage value different from the first regulated voltage; an EMI shielded case surrounding the battery pack, the boost/buck switcher, the first regulator and the second regulator; a first output terminal connected to the battery pack and supplied with the output voltage; a second output terminal connected with the first regulator and supplied with the first regulated voltage from the first regulator; and a second output terminal connected with the second regula

Abstract: A current driver has a short circuit protection circuit which monitors the magnitude of the current driver's output voltage. The protection circuit looks for the failure of the output voltage to either change to a prescribed non short-circuit representative value within a prescribed time window after the onset of a voltage transition at the input node, or to maintain that value as dictated by the input signal. If either of these conditions occurs, the protection circuit takes action to reduce the driver's output current to a relatively small `short circuit` current.

Abstract: A secondary low voltage regulator for systems having low voltage control logic and high voltage devices susceptible to thermal damage due to loss of control logic power. When a power failure interrupts the primary power supply for the control logic, the secondary regulator uses the falling high voltage normally supplied to the high voltage devices as an input to a secondary regulator which supplies power to the control logic. The control logic remains active until the falling high voltage reaches a low level where the high voltage devices will not be heat damaged if not controlled by the control logic circuitry.

Abstract: A DC-DC converter is provided which is operable to drive a reactive circuit (10) that includes both a series inductor (12) and a capacitor (14) disposed between the output node and ground. The DC-DC converter includes two switches, a transistor switch (20) connected between a positive supply and an input node (16) and a second transistor (28) connected between the node (16) and ground. In one mode of operation, the transistors (20) and (28) operate in an asynchronous regulation mode with clock signals provided to the gates thereof. In a second asynchronous mode of operation, transistor (28) is turned off and replaced by its junction isolation diode (48). The transistor (20) is driven by a clock signal in accordance with an asynchronous regulation mode of operation. In a third mode of operation, the modified asynchronous duty cycle to the gate of transistor (20) is altered.

Abstract: A controller for a two-switch buck-boost converter accomplishes one-at-a-time switch control by simultaneously employing an analog error signal to control one drive output and an analog inversion of that error signal, with respect to a voltage that is equal to the voltage excursion limit of a timing ramp signal, to control the other drive output. In a second embodiment of the invention, a controller employs a comparator to compare an analog error signal against a given voltage excursion limit of a timing ramp signal to perform the functions of determining which of two drive outputs is to be enabled to be modulated and of modifying the voltage excursion limits of the timing ramp signal such that the voltage excursion limit compared by the comparator is switched between two different voltage excursion limits.

Abstract: An integrated circuit having a unit for controlling a load of an inductive nature, which unit includes a first output transistor having a first control electrode and a first main current path, a second output transistor having a second control electrode and a second main current path, a control stage coupled to the control electrodes and adapted to control the output transistors. An output terminal is coupled between the main current paths and adapted to connect the load.

Abstract: A high-voltage power supply and regulator circuit for an X-ray tube which utilizes solid-state switching devices with feed-back control for real-time monitoring and protection against voltage spikes. More specifically, the regulator circuit utilizes a feedback control loop and a series of FET to produce a continuous or pulsed output of predetermined duration and/or amplitude. Shielded voltage dividers are provided to accurately measure the voltage output and produce feedback control signals. The shielded voltage divider includes a plurality of paired conductive members disposed along the length of a resistor, which paired conductive members separate the resistor into separate portions and provide alternating first and second pairs of conductive members along the length of the resistor.

Abstract: A step-up converter is utilized to convert a first lower input voltage to a second higher output voltage. The circuit includes a soft start capability such that ringing due to excessive voltage and current is substantially eliminated. In addition, this converter includes an overcurrent protection mechanism if a load failure or other overcurrent condition occurs.

Abstract: A voltage regulator especially adaptable for use with field-programmable gate arrays (FPGA). The voltage regulator is configurable as a true voltage regulator or, alternatively, as a pseudo-voltage regulator. The voltage regulator includes circuitry to rapidly generate an operating voltage for the core or nucleus logic elements. Additional circuitry is provided to reduce the steady-state power consumption once the operating voltage is reached. To compensate for die-to-die variations, additional circuitry is also provided to adjust the compensation delays or switching rates.

Abstract: A tapped inductor slave regulating circuit provides a second slave output voltage derived from a tapped connection to the filter storage inductor of a first output voltage of a switching power supply converter. In the converter, an unregulated voltage is provided through a switching circuit to a storage inductor to develop a first output. The switching circuit is turned off and a synchronous rectifier is turned on to freewheel the current through the storage inductor and the load. The storage inductor is center-tapped and coupled to a switching circuit to provide a second slaved output. The location of the center tap is chosen to provide the proper voltage of the second output. In one embodiment, the switching circuit for the slaved output is turned on during the freewheel portion of each cycle to provide a proper voltage level for the second output. In another embodiment, a separate local feedback circuit is provided to further regulate the second output voltage level.

Abstract: The invention relates to a regulated DC power supply circuit comprising a full wave rectification stage for rectifying an AC input and a regulating stage for regulating an output voltage from the rectification stage. The regulating stage has a primary voltage regulating circuit and a secondary voltage regulating circuit. The primary voltage regulating circuit includes a series pass element, such as a MOSFET device, connected to operate continuously in source-follower mode. A primary voltage reference element, such as a zener diode, provides a gate reference for the series pass element. The secondary voltage regulating circuit is cascaded to the primary voltage regulating circuit in a voltage sharing configuration. The power supply circuit is therefore capable of handling input voltages over 1 kV, which exceed the maximum voltage rating of the MOSFET device. The invention extends to a DC voltage regulator, which includes the regulating stage without the rectification stage.

Abstract: The invention relates to a method and a circuit array for regulating the supply voltage of a load as may be found, for example, in the form of an integrated circuit in a chip card. An integrated circuit of this type contains a non-volatile memory and the control logic needed to read out the information stored in the non-volatile memory, but with the transmission of both energy and data being wireless, for example inductive. Data is transmitted by suitable modulation of the voltage supply. In order for the reader to clearly evaluate the read-out logic states, it is proposed in accordance with the invention that during output of the first logic level the supply voltage of the load is generated by serial regulation and that during output of the second logic level the terminal voltage of the voltage source is under parallel regulation.

Abstract: An apparatus for triggering a plurality of thyristor devices has a clock generator for producing a pulse train output and a digital counter for counting the number of pulses generated by the clock generator. The digital counter has a digital output which is received by a decoder. The decoder has a plurality of output lines, only one of which is in a high logic state at any time depending upon the digital output from the digital counter. A memory unit contains a plurality of digital control data, only one of which is accessed during the duration of the pulse train output. The memory unit has a plurality of memory data lines which are divided into several groups and which are used for reflecting the accessed one of the control data thereon.

Abstract: A bilateral power conversion circuit (30) includes a current sensor that includes a resistance (R.sub.s) coupled in series between a first terminal of a switch (SW2) and a ground potential. The current sensor has an output for providing an over-current signal to an input of a control circuit (24) during a time that the circuit is sinking current from a load and also during a time when the circuit is sourcing current to the load.

Abstract: The synchronous switching power supply can be employed in power supply systems requiring multiple outputs and extremely high efficiency. No minimum load is necessary. A switching power supply with boost and/or flyback converters comprises a switching circuit for providing an AC signal. Two diodes rectify the AC signal and provide a pulsating DC signal to a node. An inductor is coupled thereto for attaining a current. A capacitor is coupled to the inductor for providing a first DC output signal which is also fed back to the switching circuit. The boost and flyback converters are coupled to the node for converting the pulsating DC signal into a second and third DC output signals.

Abstract: The voltage regulator of the boosting/lowering type is comprised of a switching regulator block and a series regulator block, which are cascade-connected to each other. One input terminal of an error amplifier of the switching regulator block is connected to a dividing node of bleeder resistors in the series regulator block to constitute a regulative feedback loop effective to improve an efficiency of the voltage regulator.

Abstract: High-voltage, solid-state switches that are capable of interrupting current, offer relatively low on-state losses (low forward voltage drop) and provide for high current densities. Low-voltage transistors and silicon-controlled rectifiers are employed to achieve low power losses at high current densities. One embodiment of the present invention relates to a solid-state switch for controlling a source of direct current. The switch includes four switching elements. Each element has a first terminal, a second terminal and a control signal input terminal. The switching elements provide a high resistance to the flow of electrical current in response to a first control signal. A second control signal causes the switching elements to offer a low resistance to the flow of electrical current. The first and second switching elements are connected in series, as are the third and fourth switching elements.

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: A charge regulation circuit provides regulation of an unregulated voltage supply and provides energy storage. The charge regulation circuit according to the present invention provides energy storage without unnecessary dissipation of energy through a resistor as in prior art approaches.

Abstract: An apparatus for triggering a plurality of thyristor devices includes a full-wave rectifier circuit having a sinusoidal pulse output, a Schmitt trigger circuit to generate a constant amplitude pulse signal when the sinusoidal pulse output exceeds a certain triggering level, a clock pulse generator to generate a predetermined number of clock pulses within the duration of the constant amplitude pulse signal, and an address counter to receive the generated clock pulses. The address counter has a digital output corresponding to the number of clock pulses received. A read-only memory unit has digital data stored therein. The memory unit has a plurality of address lines to receive the digital output of the address counter and a set of output data bits corresponding to the stored digital data which is accessed according to the digital output of the address counter. Each thyristor device is triggered into the conducting state by one of the output data bits of the memory unit.

Abstract: An output circuit (62) for generating a signal in the form of a voltage between an output signal node and an output reference node (60) receives power from a pair of voltage regulators (Q1 and 68, Q2 and 70). The regulators are connected in power-circuit series so as to be powered by the difference between the output potentials of two opposite-polarity supplies without a direct low-impedance connection between the power-supply ground (73) and the output reference node (60). To avoid large current flow in any external path between an output reference node (60) of an electronic circuit and the ground node (73) of its power supply, a current sensor (R1, R2, 86) senses the net current that the power supplies provide to the circuitry that includes the regulators, and it controls variable loads (Q3, Q4) that selectively drive current into and draw current from the reference node (60) so as to drive the net current to zero.

Abstract: A device for supplying power to an electronic computer in a motor vehicle has first and second voltage regulators, operable independently of one another and having parallel inputs and outputs, and in which a desired output voltage is regulated downwards from an input voltage provided by a vehicle network. The first and second regulators each include at least one capacitive storage element at their inputs. A protective device is coupled to the inputs of the first and second regulators for connecting and disconnecting the first and second regulators from the input voltage. A voltage monitoring circuit is coupled to the first and second regulators and the protective device for detecting and evaluating the input voltage and includes at least one output each for individually controlling activation of the first and second regulators and the protective device.

Abstract: A power supply module for control electronics of a DC motor, the module comprising a power cell of the stepdown type controlled as a function of peak current, the current flowing in both directions, and the module including a bridge stage likewise capable of passing current in both directions and including a reactive element constituted by one of the windings of the DC motor. The invention is particularly suitable for space applications.

Abstract: An apparatus capable of acting as a current-limited voltage source or a voltage-limited current source is disclosed. The output of the apparatus is provided by a differential amplifier. The current and voltage outputs are compared to positive and negative current and voltage limits. Depending on whether the apparatus is in the voltage mode or the current mode, the inverting input of the differential amplifier is clamped to the appropriate voltage or current comparison signal, respectively, to provide an error signal to the differential amplifier. This clamping is current limited so that if the output current limits are exceeded while in the voltage source mode, a clamp to one of the current comparison signals occurs and dominates the voltage clamp. Similarly, if the output voltage limits are exceeded while in the current source mode, a clamp to one of the voltage comparison signals occurs and dominates the current clamp.

Abstract: A direct current power supply circuit converts an unregulated direct current input source such as an automobile battery to a regulated direct current output voltage for a device such as a mobile telephone requiring a fixed operating voltage. The circuit has an improved input to output voltage rating of less than two volts, enabling it to supply a load reliably with direct current power from an unregulated direct current source as low as ten volts. The circuit operates in a linear mode at low power levels and in a switching, pulse width modulated mode at higher output power levels. The circuit employs a three-terminal linear voltage regulator as a control element. It has input, output, and ground pins and is effective in response to current input through the input pin to maintain a predetermined, fixed voltage differential between the output and ground pins. In the example disclosed, the linear voltage regulator maintains a 5-volt differential between the output and ground pins.