Abstract: There is disclosed an apparatus and method for providing multiple power supply voltages to an integrated circuit. In an integrated circuit of the type comprising at least two power supply domains in which each power supply domain comprises at least one module powered by the same voltage level, the apparatus and method of the present invention blocks an output signal in a first power supply domain from being sent to a second power supply domain when the second power supply domain is in a low power mode. The apparatus and method of the present invention also blocks an output signal from a first power supply domain from being received in a second power supply domain when the first power supply domain is in a low power mode. Power sense cells are used to determine the status of power supply domains and logic circuits are used to block undesired signals. The present invention also properly synchronizes clock signals when power supply domains are activated or inactivated.

Abstract: A control device of a cooling device controls a fan based on a desired temperature around a CPU set by a target value setting unit and a temperature detected by a temperature detecting unit, so that the temperature around the CPU substantially coincides with the set desired temperature. When the detected temperature exceeds the desired temperature, the control device causes the fan to rotate. At this time, the control device monitors the level of a noise generated by the fan by means of the noise detecting unit. The control device increases the value of the voltage supplied to the fan within a range in which the detected noise does not vary abruptly. As a result, the rotation speed is gradually increased to a predetermined value without causing an abrupt rise of a noise, which may acutely irritate the user.

Abstract: An energy generation network according to the present disclosure includes energy generating elements organized in a tree structure of superior and inferior system levels, with control systems and a communication network. In a currently preferred embodiment, energy generating elements are turbogenerators as described above. Communications and processing are distributed throughout the systems and sub-systems of energy generating elements. Inferior sub-systems and systems of sub-systems appears as a single unit to the superior system or sub-system level. Thus, the energy generating elements appears as a seamless single energy generating unit. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A device includes a governor for controlling the frequency of the generator of a private power generation equipment, function generating means having a function characteristic for detecting the frequency variation rate of the generator and outputting a large output to the value thereof, effective power adjusting means for outputting an output proportionate to the signal, and protective relays for sensing abnormality of the frequency variation rate of the generator, so that, by making the signal in which an output from the function generating means and an output from the effective power adjusting means are synthesized an instruction signal of the governor, and shifting the frequency variation rate of the generator to a level sensed by the protective relays by the function characteristic of the function generating means at the power outage on the alternating current power line side, to detect the power outage on the alternating current power line side.

Abstract: Solid state switching devices, such as power IGBT's, are used to switch a load from one AC generator to another. The switching is controlled to occur only when the phase and voltage of the two generator outputs are within acceptable limited, thus minimizing voltage and current transients.

Abstract: A low cost differential voltage limiter circuit provides a feedback to regulate a voltage output of a voltage source. In one embodiment, the limiter circuit includes a transistor coupled to outputs of first and second voltage sources. If a differential voltage between the two sources exceeds a predetermined threshold, the output voltage of the higher source is reduced. In one embodiment, a PNP transistor is used to regulate the high voltage source.

Abstract: An apparatus and method for protecting synchronous generators against off-nominal frequency deviation and alternating forces excitation is provided. Particular application can be found with generators within a power generator plant integrated into a power transmission grid system. A electrical relay system is in operative association with an electrical signal representative of an actual frequency at which the generator is operating and to an electrical signal representative of an actual forcing amount at which the generator is operating. The relay system is adapted to respond to the actual frequency signal and the actual forcing signal such that the relay system compares the actual frequency signal with a predetermined desired frequency range and compares the actual forcing signal with at least one predetermined forcing amount, and selectively alarms the unit operator or trips the generator to an off-line mode depending upon the comparisons.

Abstract: A hybrid use of a phase-locked-loop controller and a microprocessor-based controller to synchronize the phase angles of a three-phase AC power source, such as a static power converter, with those of a three-phase power grid. The phase-angle synchronization may enable the AC power source to be safely connected to the power grid to provide additional power capacity.

Abstract: An apparatus for providing power to electronic equipment having multiple power sources. The separate and distinct power sources drive corresponding primary circuits such that the power source inputs can be of a different nature and the power supply can be designed to accommodate different types of voltage inputs. Each primary circuit is isolated one from the other, such that damage resulting from ground-loop potentials is minimized by circuit isolation. Circuit isolation is accomplished by optical isolation between each primary circuit.

Abstract: A system includes a first voltage regulator, a second voltage regulator, a third voltage regulator and a circuit. The first voltage regulator is coupled to receive power from a first power line, and the second voltage regulator coupled to receive power from a second power line. The circuit monitors a voltage of at least one of the first and second power lines and based on the monitored voltage, the circuit selectively couples the third voltage regulator to receive power from one of the first and second power lines.

Abstract: An active protection circuit for a MOSFET isolated switched power supply system operates to control the switching of the MOSFET isolation switches. A monitoring circuit operates to sense and turn off the isolation switch of the currently active power supply if it senses reverse current flowing through the switch. Simultaneously, a controller receives indication that the active power supply is out of specification, and actively switches the system voltage source to the other power supply. The controller actively ensures that the isolation switch of the out-of-specification power supply remains off until it determines otherwise.

Abstract: Process for electrically energizing a motor vehicle wiring circuit which has a battery, at least one electric consuming device and a fuel cell unit connected therein. The fuel cell unit is activated when the battery voltage falls below a preadjustable battery voltage limit, and when the wiring load exceeds a preadjustable vehicle wiring load; and is deactivated when the battery voltage exceeds a preadjustable battery voltage limit.

Abstract: A circuit configuration for supplying voltage to an integrated circuit via a pad that is connected to the input of a Schmitt trigger on the integrated circuit. The pad is also provided for configuring the integrated circuit. The integrated circuit has a multiplicity of voltage supply lines for voltage supply purposes. According to the invention, the pad is connected to a respective voltage supply line via a respective switch, and the switches are switched on or off by a control circuit that is controlled by at least one on-chip control signal.

Abstract: An inductance balancer is connected between a drive and a flat three phase power transmission cable employed to carry power to a remote load. The inductance balancer includes a first inductance device (e.g., a single wound inductor) connecting the center cable conductor to the drive and raising the total effective inductance of the center cable conductor to the inductance of either of the outer cable conductors at maximum inductance. The inductance balancer also includes a second inductance device connecting both outer conductors to the drive and adding an inductance equal to that of the first inductance device when current exists only on an outer conductor and the center conductor, but adding no inductance to the outer conductors when current exists only on those two conductors.

Abstract: A system for connecting a receiver to a redundant power supply. The power supply units are connected to the receiver by means of a pair of control switches, each being connected in series between one of the power units and the receiver, and each having its intrinsic diode forwardly biased between the power unit and the receiver. A voltage comparator senses which of the power supply units is having the higher potential difference between its high and low potential terminals. The output of the comparator controls the gate of both control switches such that the control switch in series with the sensed power supply unit is conducting while the other one is off. When a reversed polarity is applied to the receiver, the receiver is protected by the intrinsic diode. When at least one of the power supplies is connected with the correct polarity, the receiver is supplied without an appreciable voltage drop and with the lowest possible power losses.

Abstract: A power supply device having two AC power inputs includes a power unit that has first and second AC power inputs and a power output, a step-down and filter unit, a power regulator unit, and a detecting and switching unit. The step-down and filter unit converts the AC from the power unit to a low-voltage DC power. The power regulator unit maintains the low-voltage DC power as a stable power. The detecting and switching unit detects whether a power failure occurs on the first AC power input and subsequently switches the power supply to the second AC power input to keep a stable power supply so as to avoid any damage caused from the failure of the power supply.

Abstract: A switching circuit useful in a binary demand feedback DC converter having multiple DC outputs which are all independently regulated using a binary on/off technique is disclosed. A comparator associated with each output compares the voltage at a given output with a reference voltage for the respective given output and generates a first signal the moment the output voltage exceeds the reference voltage. Responding immediately to the first signal a switch opens the converter transformer secondary winding associated with that output from a rectifier and filter. The voltage at that output is determined by the voltage across a capacitor in the filter and the capacitor commences discharging to be below the reference voltage at which time the first signal ceases and the switch reconnects the secondary winding to the rectifier and filter to recommence charging the filter capacitor.

Abstract: A back-electromotive force protection circuit that is able to protect circuit components other than a hard disc against the back-electromotive force generated in the hard disc. A back-electromotive force protection circuit includes a power source 10, a hard disc 20 having a positive side terminal connected via a connection line 22 to the positive side terminal of the power source 10 and having Ma negative side terminal connected via connection lines 24, 26 to the negative side terminal of the power source 10, a load 30 provided between the connection line 22 and the connection line 24 and a FET 40 for turning off the connection lines 24, 26 if no power is supplied from the power source 10.

Abstract: A power transfer device includes a first current transferring section connected between a first AC power source and a load, a second current transferring section with first and second switches which have opposite conduction directions, connected in parallel, and connected between a second AC power source and the load; a current detector for detecting a current flowing from the first AC power source to the load; a generator for generating a power transfer signal instructing transfer from the first AC power source to the second AC power source; a current direction estimator for estimating the direction of a current which flows from the first AC power source to the load when the second current transferring section enters the conduction state after a time period; and a conduction signal generator for causing one of the first and second switches to be conductive, so that the current flowing from the first AC power source to the load is cancelled, and, thereafter, causing the other of the first and second switches

Abstract: A pulse signal transmitting circuit generates a pulse signal having an enhanced high-frequency component with a reduced power loss. A pulse signal is transmitted to a load circuit through a transmission cable connected to a secondary winding of a transformer. First and second transistors are connected to a primary winding of the transformer. A voltage output from an external power source is input to the primary winding of the transformer when at least one of the first and second transistors is conductive so that a pulse voltage signal is input to the transformer. A booster power supply circuit is located between the external power source and a middle point of the primary winding of the transformer. The booster power supply circuit superimposes a boost voltage onto the voltage input to the primary winding of the transformer so that a high-frequency component of the pulse voltage signal input to the primary winding of the transformer is enhanced.

Abstract: A power system has a first power supply operatively connect in parallel to a second power supply. The output of the first power supply is connected to the input of a switching device, such as a mosfet. The output of the switching device is the output of the power system. A measuring device, such as a differential amplifier measures the polarity between the input and output of the switching device. A controller connected to the switching device permits the switching device to conduct current if a first polarity is present between the input and the output. The controller interrupts current flow if a second polarity is present between the input and the output.

Abstract: An active protection circuit for a MOSFET isolated switched power supply system operates to control the switching of the MOSFET isolation switches. A monitoring circuit operates to sense and turn off the isolation switch of the currently active power supply if it senses reverse current flowing through the switch. Simultaneously, a controller receives indication that the active power supply is out of specification, and actively switches the system voltage source to the other power supply. The controller actively ensures that the isolation switch of the out-of-specification power supply remains off until it determines otherwise.

Abstract: The present invention provides a system interconnection protective device. A command for dropping a voltage is issued when the frequency change rate of a private generator set is positive, and a command for raising a voltage is issued when the frequency change rate is negative. The output voltage of the private generator set is varied by supplying an automatic voltage regulator with the voltage variation reference obtained by assisting the commands based on a rough tendency of frequency variations. Thus, a sole operation of the private generator set, which interconnects with a system, can reliably and easily be detected and protected on the side of the private generator set by enlarging the frequency variations without using any expensive transfer breaker.

Abstract: There is disclosed an apparatus and method for providing multiple power supply voltages to an integrated circuit. In an integrated circuit of the type comprising at least two power supply domains in which each power supply domain comprises at least one module powered by the same voltage level, the apparatus and method of the present invention blocks an output signal in a first power supply domain from being sent to a second power supply domain when the second power supply domain is in a low power mode. The apparatus and method of the present invention also blocks an output signal from a first power supply domain from being received in a second power supply domain when the first power supply domain is in a low power mode. Power sense cells are used to determine the status of power supply domains and logic circuits are used to block undesired signals. The present invention also properly synchronizes clock signals when power supply domains are activated or inactivated.

Abstract: A preferred embodiment of the electrical power system of the present invention includes a power conditioning unit which is configured to receive the DC electrical output signal to deliver an AC output signal to a grid-connected load. Preferably, the power conditioning unit includes a controller which is configured to monitor the AC output signal so that the power conditioning unit may cease delivering the AC output signal when a characteristic of the AC output signal satisfies an established criterion.

Abstract: Solid state switching devices, such as power IGBT's, are used to switch a load from one AC generator to another. The switching is controlled to occur only when the phase and voltage of the two generator outputs are within acceptable limited, thus minimising voltage and current transients.

Abstract: Apparatus for automatically selecting one of two or more available power supply voltages for use as a main power supply of a PCI adapter is described. In one embodiment, a power supply selector is designed such that the presence of a positive voltage at a Vaux input thereof prevents power at a Vcc input thereof from driving a main power supply input to a PCI adapter. Conversely, the absence of a positive voltage at the Vaux results in the main power supply input to the PCI adapter being derived from the Vcc input. In an alternative embodiment, jumpers are provided for enabling a user to select which power supply will be used as the “default” power supply for the adapter.

Abstract: A power delivery system including a primary power bus for transferring power to the facility from on-site generators, and a secondary power bus for transferring power to the facility from a utility. The system further includes a static disconnect switch capable of quickly isolating the facility from the utility power grid, and a controller for controlling the overall operation of the power delivery system. In a normal mode of operation, the utility supplies power approximately in the amount of the single largest load in the facility, with the remaining power being supplied by the on-site generators. If one or more of the generators go off-line, the power supply from the utility may be increased. Similarly, if the quality of the power supplied by the utility drops below a predetermined level, the static disconnect switch quickly opens and islands the facility, whereupon 100% of the power is supplied by the generators.

Abstract: A system includes a first voltage regulator, a second voltage regulator, a third voltage regulator and a circuit. The first voltage regulator is coupled to receive power from a first power line, and the second voltage regulator coupled to receive power from a second power line. The circuit monitors a voltage of at least one of the first and second power lines and based on the monitored voltage, the circuit selectively couples the third voltage regulator to receive power from one of the first and second power lines.

Abstract: Disclosed is a power management system for a portable phone, for example, a cellular phone operating according to a specific mobile communications standard GSM. The power management system comprises a switching module which switches automatically from a voltage provided by a battery to a voltage provided by an external power supply when the power management system is connected to an external power supply. Furthermore, the system comprises a module of voltage regulators, each regulator providing a preset voltage, and a first and second voltage converter. The first voltage converter transforms a first input voltage having a first value to an internal voltage having a lower value. The second voltage converter transforms a second input voltage having a second value to an internal voltage having a higher value. An included reset circuit provides an automated reset function. A logic array module is connected to input ports and is associated with a communications interface.

Abstract: A binary demand feedback DC converter having multiple DC outputs which are all independently regulated using a binary on/off technique is disclosed. A comparator associated with each output compares the voltage at a given output with a reference voltage for the respective given output and generates a first signal the moment the output voltage exceeds the reference voltage. Responding immediately to the first signal a switch opens the converter transformer secondary winding associated with that output from a rectifier and filter. The voltage at that output is determined by the voltage across a capacitor in the filter and the capacitor commences discharging to be below the reference voltage at which time the first signal ceases and the switch reconnects the secondary winding to the rectifier and filter to recommence charging the filter capacitor.

Abstract: A control arrangement and method is provided for a power electronic system configured as a high-speed source-transfer switching systems (HSSTSS). The HSSTSS supplies an electrical load with alternating current from either a first source or a second source via respective first and second solid-state switches. The HSSTSS also includes a controller that samples the voltage waveforms of each of the first and second sources to detect when transfer between the sources is desirable, e.g. outages or voltage that is either too low or too high. The controller provides appropriate control signals to control operation of the solid-state switches and transfer supply of the load therebetween. The control arrangement avoids undesirable current flow between sources via a comparison of the voltages of the sources and current in the outgoing source, i.e.

Abstract: An electronic instrument in which erroneous operation after power is applied thereto even in the case where a power source voltage is not quickly raised. Power is generated by a power source such as a thermoelectric conversion device and stored in a secondary battery or charge storage device through a optional boosting circuit. A control circuit and a main circuit are supplied with the power. However, the control circuit has a lower minimum operating voltage than the main circuit. Thus, with the increase in level of the power source voltage, the control circuit starts to operate before the main circuit and outputs a control signal to prevent the main circuit from operating in such a manner that a through current is prevented and the main circuit is prevented from drawing appreciable current from the power source circuit, which would prevent the voltage of the secondary battery or the charge storage device from increasing.

Abstract: The protecting apparatus includes a circuit for automatically and continuously determining the difference voltage between the voltage at the input side of a connecting circuit breaker and the voltage at an output side thereof between an electric generator and an associated power system, following initiation of closure of the connecting circuit breaker. The difference voltage is representative of the voltage angle of the generator relative to the electrical system. The difference voltage is compared against a reference value, which is selected such that a voltage angle value greater than the reference value will result in damage to the generator and/or the electrical system. An output signal is developed which can then be used to trip circuit breakers serving the electrical system if the reference value is exceeded by the difference voltage.

Abstract: A portable, battery-operated AC electromagnetic yoke for detecting surface defects in ferrous materials by employing an AC magnetic field. The yoke includes a circuit that produces a quasi AC square wave voltage. The resulting AC magnetic field is the required inspection method of common practice and is capable of demagnetizing upon completion of inspection. A first bank of batteries supplies approximately sixty volts positive DC and a second bank of batteries supplies approximately sixty volts negative DC to power transistors that are in electrical communication with the yoke. Logic circuitry is employed to switch the respective banks of batteries on and off to simulate an AC circuit. The logic circuit includes a clock for generating pulses that are fed to a phase splitter circuit and to a delay and pulse shaping circuit. The respective outputs of those circuits are fed to logic gates that are in electrical communication with a voltage level shifting circuit that triggers the power drivers.

Abstract: An integrated system for comprehensive control of an electric power generation system utilizes state machine control having particularly defined control states and permitted control state transitions. In this way, accurate, dependable and safe control of the electric power generation system is provided. Several of these control states may be utilized in conjunction with a utility outage ride-through technique that compensates for a utility outage by predictably controlling the system to bring the system off-line and to bring the system back on-line when the utility returns. Furthermore, a line synchronization technique synchronizes the generated power with the power on the grid when coming back on-line. The line synchronization technique limits the rate of synchronization to permit undesired transient voltages.

Abstract: A power converter system includes: a circuit breaker having one terminal connected to a power system and another terminal connected to a load; a transformer for interconnection; a power converter; and a controller for controlling the power converter, wherein, during a return to grid connected operation, the power converter is controlled such that the phase of an output voltage of the power converter matches the phase of the system voltage, and the circuit breaker is closed, so as to prevent an overcurrent during a changeover from the self commutated operation to the grid connected operation of the power converter.

Abstract: The present invention relates generally to D.C. power supplies and more particularly to overvoltage protection in one or more D.C. power supply circuits, where a plurality of D.C. power supplies may be connected together to supply power to an electronic system. In one embodiment a D.C. power supply circuit is provided which, when used with the plurality of D.C. power supply circuits connected in parallel, is capable of stopping only the power supply circuit having run into an overvoltage state with minimal effect on the other D.C. power supply circuits. Thus power to the load is continued.

Abstract: A line-interactive single conversion uninterruptible power supply (UPS) utilizing a multiple tapped ferroresonant transformer and a square wave PWM inverter is presented. During normal utility line operation, the line voltage is not modified in any way, except for ferroresonant filtering and regulation. Tap control circuitry insures proper tap selection based on the utility input voltage. During tap transitions in utility out of specification operation, a second power source, such as an inverter, is operated to provide output power to the connected loads. The control of the inverter switching angles may be accomplished through a look-up table. This look-up table contains the converter pulse widths for monitored battery voltage. No output voltage feedback is required. Based on the inherent regulation provided by the ferroresonant transformer, the PWM control may be accomplished in course steps.

Abstract: A synchronous condenser (12) is synchronized with a power system (14) by modifying its rotational speed using a prime mover (18) while controlling the rate of change of rotational speed of the synchronous condenser (FIG. 1). With an open circuit breaker (16), the synchronous condenser (12) is brought to a rotational speed (44) close to a desired synchronizing speed (48). A clutch (20) operates between the prime mover (18) and the synchronous condenser (12) and disengages the prime mover (18) from operation once the synchronous condenser (12) is placed into operation with the power system (14). An excitation voltage is provided to the synchronization condenser (12) for providing an output voltage, which voltage is monitored. The rotational speed of the prime mover (18) is ramped at a desirable rate of change (46) for approaching an acceptable synchronizing speed (50). The rotor speed and system phase angles are monitored for bringing a desirable changing speed close to the synchronizing speed (48).

Abstract: A power sphere has a curved surface upon which are mounted individual indivisible solar cells receiving differing amounts of solar illumination without solar tracking and pointing while providing respective differing amounts of solar power coupled through respective regulators onto a regulated bus for powering a connected load. The respective regulators continue to provide sufficient coupled power onto the bus even in the event of a failure of one or more of the solar cells thereby enabling graceful degradation of power delivery to the load for improved reliability of power delivery, particularly useful in space satellite systems.

Abstract: A redundant power supply with a number of loads is coupled to each half of the redundant supply by a respectively different MOSFET switch, with logic gates coupling control signals to the MOSFET switches. The control signal is coupled as one input to the logic gate and the output of the logic gate is connected to the MOSFET switch. The other input of the logic gates for a particular power supply is the output of an overvoltage detection circuit whose output is coupled as an input to all the gates for that power supply. The output of the gates opens the MOSFET switches in response to detection of an overvoltage condition.

Abstract: The isolation operation of a non-utility generation system (7) interconnected to a power system enable to be reliably detected in the non-utility generation system, providing a transfer breaker. When the frequency change rate of the non-utility generation system (7) has a positive value, the advanced reactive power of the non-utility generation system (7) is increased. When the frequency change rate of the non-utility generation system (7) has a negative value, the delayed reactive power of the non-utility generation system (7) is increased. Further, the gain of the power control section (9) of the non-utility generation system (7) is adjusted in accordance with the frequency change rate. As the gain is thus adjusted, the voltage of the non-utility generation system (7) changes. This change in the voltage is detected. In accordance with the voltage change, the non-utility generation system (7) is disconnected from the system power supply.

Abstract: A battery backed-up semiconductor device employs a Vss switching configuration to provide uninterrupted battery power to critical circuitry of the device even in the event of external conditions, such as undershoot, that threaten to corrupt data stored by the device. Both primary power and battery power, when needed, are supplied to floating wells of the device rather than to the device substrate, making the device immune to undershoots that can short the battery to the device substrate and corrupt data stored by the device. The device substrate is permanently tied to the positive power supply voltage and the positive terminal of the battery voltage and is therefore not subject to the concerns associated with switching from a failed primary power supply to the back-up battery power supply.

Abstract: A generator set controller includes a dead bus sensor producing a dead bus signal indicative of a power failure on a power bus that is an input to the controller on a digital input channel. The controller also receives a voltage signal from a phase of a power bus.

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 fast changeover from one power system to another in the event of an irregularity in the power source system substantially reduces operating costs by minimizing a power loss in switches during conduction, dispenses with a cooling device for cooling a thyristor switch, and implements the thyristor switch in a compact and low-cost design. The power supply system for a load includes one switching apparatus for connecting a load to one power source system, and another switching apparatus for connecting the load to another power source system. Each of the switching apparatus includes a pair of thyristors connected in anti-parallel and a mechanical switch connected in parallel with the thyristor pair. The thyristor pairs and the mechanical switches are controlled so that the mechanical switches conduct a load current when the load is supplied with power from the one power source system in a steady power supply state.

Abstract: A switching system having a plurality of positions for separating or interconnecting a generator, a network transformer, and a starter device, the system including a circuit breaker for the generator and a busbar disconnector for separating or interconnecting the generator and the network transformer, and a starter disconnector for separating or interconnecting the generator and the starter device. The busbar disconnector includes a first fixed contact and a first moving contact that co-operates by sliding with the first fixed contact, the first fixed contact and the first moving contact being integrated with the circuit breaker of the generator. The starter disconnector includes a second fixed contact and a second moving contact that co-operates with the second fixed contact by rotation. This organization remains economical to implement even for applications in which the generator is an alternator in a combined cycle or a gas turbine power station.

Abstract: The output of the power unit 21 varies on the basis of the output of the power unit 22, and temperature-compensated in accordance with an ambient temperature. The control is performed by the output voltage control circuit 3. The output voltage of the power unit 21 is varied with an output voltage ratio between the outputs of the power units, and by compensating an output voltage of the power unit 22 in accordance with the ambient temperature, the output voltage of the other power unit 21 can be temperature-compensated by the control circuit 3.

Abstract: An apparatus and method for switching between two power supplies, a primary power supply and a secondary power supply. The present invention generates a first reference voltage using the voltage of the primary power supply and the secondary power supply, wherein the primary power supply voltage is variable. The present invention also generates a second reference voltage based on the voltage of the primary power supply. The first and second reference voltages each have a different slope and the crossing point between these two reference voltages indicate that a switch between the primary power supply and the secondary power supply should occur.