Abstract: A power supply apparatus useful for starting and driving a discharge lamp 22 includes a DC-to-DC converter 16 for converting a DC signal from a DC power supply to a second DC signal having a predetermined magnitude which is supplied to the lamp. A current detector 24 develops a DC current representative signal representing DC current supplied to the lamp from the DC-to-DC converter. A combination of the current detector 24, a DC voltage detector 26 and a multiplier 30 develops a DC power representative signal representing DC power supplied from the DC-to-DC converter to the lamp. An error amplifier 32 develops a DC current error signal representing the difference between the DC current representative signal and a predetermined DC current reference signal. An error amplifier 36 develops a DC power error signal representing the difference between the DC power representative signal and a predetermined power reference signal.

Abstract: One of commercial AC voltages is coupled to power supply terminals from one of commercial AC power supplies. The AC power supplies belong to either a first group providing higher voltages or a second group providing lower voltages. A rectifier rectifies the AC voltage applied to the power supply terminals, and a rectified voltage is developed between two rectifier output terminals. A switching unit operates to connect voltage-boosting converters selectively in series and in parallel between the rectifier output terminals. Inverters are connected in the output sides of and in association with the respective voltage-boosting converters for converting DC voltages from the associated voltage-boosting converters to high-frequency voltages. The high-frequency voltages are voltage-transformed by associated voltage-transformers, and the voltage-transformed high-frequency voltages are converted into a DC voltage by a rectifier circuit and a reactor.

Abstract: A voltage from an AC power source is converted into a DC voltage in an input-side rectifier-smoother circuit. The DC voltage is then converted into a high-frequency voltage in an inverter, and the resulting high-frequency voltage is voltage-transformed in a transformer. The voltage-transformed high-frequency voltage is converted into a DC voltage in an output-side rectifier-smoother circuit, which is applied via output terminals to a load. The input-side and output-side rectifier-smoother circuits, the inverter and the transformer are enclosed in a casing having a plastic panel. The output terminal of the apparatus is mounted on the plastic panel.

Abstract: One of commercial AC voltages is coupled to power supply terminals from one of commercial AC power supplies. The AC power supplies belong to either a first group providing higher voltages or a second group providing lower voltages. A rectifier rectifies the AC voltage applied to the power supply terminals, and a rectified voltage is developed between two rectifier output terminals. A switching unit operates to connect voltage-boosting converters selectively in series and in parallel between the rectifier output terminals. Inverters are connected in the output sides of and in association with the respective voltage-boosting converters for converting DC voltages from the associated voltage-boosting converters to high-frequency voltages. The high-frequency voltages are voltage-transformed by associated voltage-transformers, and the voltage-transformed high-frequency voltages are converted into a DC voltage by a rectifier circuit and a reactor.

Abstract: A voltage from an AC power source is converted into a DC voltage in an input-side rectifier-smoother circuit. The DC voltage is then converted into a high-frequency voltage in an inverter, and the resulting high-frequency voltage is voltage-transformed in a transformer. The voltage-transformed high-frequency voltage is converted into a DC voltage in an output-side rectifier-smoother circuit, which is applied via output terminals to a load. The input-side and output-side rectifier-smoother circuits, the inverter and the transformer are enclosed in a casing having a plastic panel. The output terminal of the apparatus is mounted on the plastic panel.

Abstract: A power supply apparatus useful for starting and driving a discharge lamp 22 includes a DC-to-DC converter 16 for converting a DC signal from a DC power supply to a second DC signal having a predetermined magnitude which is supplied to the lamp. A current detector 24 develops a DC current representative signal representing DC current supplied to the lamp from the DC-to-DC converter. A combination of the current detector 24, a DC voltage detector 26 and a multiplier 30 develops a DC power representative signal representing DC power supplied from the DC-to-DC converter to the lamp. An error amplifier 32 develops a DC current error signal representing the difference between the DC current representative signal and a predetermined DC current reference signal. An error amplifier 36 develops a DC power error signal representing the difference between the DC power representative signal and a predetermined power reference signal.

Abstract: A power supply apparatus includes a power supply unit disposed within a casing. The power supply unit includes power semiconductor devices. A fan is provided in the casing for cooling the power semiconductor devices. The power supply unit is operated in a plurality of contiguous cycles each including a running and pausing modes of operation. Each cycle lasting a relatively short time period. The power supply unit operates in the running mode and the pausing mode, respectively in response to the closing and opening of a start switch. In association with the closing and opening of the start switch, a switch for the cooling fan causes the fan to rotate and stop, respectively, which results in minimizing the difference between the highest and lowest temperatures of the power semiconductor devices so that the lifetime of the power semiconductor devices can be prolonged.

Abstract: A DC voltage resulting from rectifying and smoothing a commercial AC voltage is converted into a high-frequency voltage in an inverter which is operated in response to the closure of a start switch. A transformer transforms the high-frequency voltage, and the voltage-transformed high-frequency voltage is converted to a DC voltage by a rectifier and reactor for application between a torch and a workpiece with a gap disposed therebetween. In response to the closure of the start switch, an igniter operated from the voltage-transformed high-frequency voltage is enabled by an igniter driver to thereby apply a high-frequency voltage between the torch and the workpiece to generate an arc therebetween. A current detector detects current attributable to the arcing. A timer starts operating upon closure of the start switch and causes a disabling commander to disable the inverter when no current is detected by the current detector during a time period longer than a period required for an arc to be generated in the gap.

Abstract: A DC power supply apparatus includes a rectifier circuit which rectifies an input commercial AC voltage. The rectifier output voltage is smoothed in a smoothing capacitor. The DC voltage from the capacitor is converted to a high-frequency voltage in an inverter. The high-frequency voltage from the inverter is voltage-transformed by a transformer into a voltage-transformed, high-frequency voltage, which is then converted back into a DC voltage in a high-frequency-to-DC converter circuit. When an input commercial AC voltage is applied to the DC power supply apparatus, a pre-charging circuit pre-charges the smoothing capacitor from the input AC voltage. If a voltage having a magnitude larger than a prescribed value is applied to the DC power supply apparatus, an overvoltage protection circuit renders the rectifier circuit and the pre-charging circuit inoperative.

Abstract: An AC voltage applied among power input supply terminals is rectified by a rectifier, and the rectified voltage is adapted to be reduced in a voltage-reducing converter with a switch connected in parallel with it. A switching circuit connect smoothing capacitors in series or parallel to the voltage-reducing converter. Inverters are connected in parallel with the respective smoothing capacitors. The output voltages of the inverters are voltage-transformed by transformers. The transformed voltages from the transformers are converted to DC voltages by converters. A control unit renders the voltage-reducing converter operative and causes the switching circuit to connect the smoothing capacitors in series when a third AC voltage is applied among the power supply input terminals.

Abstract: A power supply apparatus for welders includes an input-side AC-to-DC converter for converting an input commercial AC voltage into a DC voltage, which is, in turn, converted to a high-frequency voltage in an inverter. The high-frequency voltage is transformed to a high-frequency voltage having a desired magnitude in a transformer. The transformed high-frequency voltage is then converted back to a DC voltage in an output-side high-frequency-to-DC converter. The DC voltage is developed between output terminals of the power supply apparatus. A current detector detects the current flowing through the output terminals and develops a detected-current representative signal. A voltage detector detects the voltage between the output terminals and develops a detected-voltage representative signal. A CPU has three control modes and controls, in a first mode, the inverter in such a manner that the current representative signal becomes equal to a reference-current representative signal.

Abstract: DC power from a smoothing capacitor is converted into high frequency power by an inverter, and then lowered by an output transformer. The lowered high frequency power is converted into DC power by an output rectifier and a DC reactor, and then supplied to a load. The load is short-circuited and then opened to initiate arcing. The short-circuiting and the arcing alternate. An auxiliary rectifier provides a load-voltage representative signal, and a current detector detects a load current. A load-current representative signal is differentiated by a differentiation circuit. The signals from the auxiliary rectifier, the current detector and the differentiation circuit, and a reference signal are applied to an operational amplifier. A control circuit controls the inverter such that the output of the operational amplifier can be zero.

Abstract: An inverter includes a series circuit of two current conducting units connected between two input terminals adapted to be connected to a DC power supply. Two first capacitors are connected in series between the two input terminals. A primary winding of a transformer is connected between the junction of the current conducting units and the junction of the first capacitors. Each of the current conducting units includes a parallel circuit of an IGBT, a diode and a second capacitor. The IGBT has a collector, an emitter and a gate and is rendered conductive when a control signal is applied to the gate while a voltage of a predetermined polarity is applied between the collector and the emitter. The diode is connected in inverse parallel with the IGBT. An inverter control circuit applies alternately the control signals to the respective IGBTs with a predetermined quiescent period disposed between the respective control signals applied.

Abstract: A DC power supply apparatus includes an input-side rectifier which rectifies an input AC voltage and supplies the rectified voltage to a voltage-boosting converter. The voltage-boosting converter converts the supplied voltage to a voltage of a predetermined magnitude. The predetermined magnitude voltage is, then, converted to a high-frequency voltage by an inverter and applied to a primary winding of a transformer. An output-side rectifier rectifies a high-frequency voltage induced in a secondary winding of the transformer. The inverter includes IGBTs and diodes, which are connected in a full-bridge configuration. A capacitor is connected in parallel with each IGBT. When the IGBTs are rendered conductive by the charging and discharging of the capacitors, no current flows through the IGBTs, and when the IGBTs are rendered nonconductive, the voltages applied to the IGBTs are made to become zero.

Abstract: DC power supply apparatus includes an input-side rectifier for converting an AC signal from an AC power supply into a DC signal. A DC-to-high-frequency converter converts the DC signal into a high frequency signal in response to a control signal from a control unit. An output-side rectifier converts the high frequency signal into a DC signal and applies it to a load. An input current detector detects an input current flowing through the input-side rectifier and generates a signal representative of the input current. A load current detector detects a load current flowing through the load and generates a signal representative of the load current.

Abstract: Power supply apparatus includes a converter which converts a commercial AC voltage into a DC voltage. An inverter converts the DC voltage into a high frequency voltage. The high frequency voltage is voltage-transformed by a transformer, and then rectified and smoothed by a rectifier and a smoothing reactor into a DC voltage. This DC voltage is applied between a workpiece and a torch. A high frequency voltage generator generates a high frequency voltage and applies it to a primary winding of a coupling transformer. A boosted high frequency voltage is induced in a first secondary winding and applied between the workpiece and the torch, so that arcing is initiated. The coupling transformer includes a second secondary winding in which another high frequency voltage is induced. The high frequency voltage induced in the second secondary winding is converted into a DC voltage by a diode and a smoothing capacitor for application between the workpiece and the torch, so that the arcing is sustained.

Abstract: A power supply apparatus for a plasma arc utilizing equipment providing an output current nearly equal to an input current includes a first converter for converting an AC voltage to a DC voltage. The DC voltage is converted to a high frequency voltage by an inverter. The output of the inverter is converted through a second converter to a DC voltage which is applied between a torch and a workpiece. A current detector detects an output current flowing between the second converter and the workpiece. A voltage detector detects an output voltage between the torch and the workpiece. A multiplier multiplies the output current and the output voltage to provide a signal representative of an output power. A comparator compares the output power representative signal with a first preset value.

Abstract: A power supply apparatus includes a housing containing therein a component which generates heat when operating, a fan for cooling the heat-generating component, and a driving unit for driving the fan. The housing also contains therein a temperature detector for detecting the temperature in the housing and providing a detected-temperature representing signal. In response to the detected-temperature representing signal, a control unit provides the driving unit with a control signal to change the rotation speed of the fan.

Abstract: A DC power supply apparatus includes a rectifier circuit for rectifying an input AC voltage to develop a rectified voltage between two output terminals thereof. First and second smoothing capacitors are connected in series between the output terminals of the rectifier circuit. First and second voltages developed across the first and second capacitors are applied to first and second inverters which convert the applied voltages to high-frequency voltages, which, in turn, are applied to a transformer. The transformer develops a transformed high-frequency voltage which is converted to a DC voltage by a converter. A voltage detector detects the first and second voltages, and the detected first and second voltages are compared in a microprocessor. An inverter control circuit controls the first and second inverters in accordance with the result of comparison, in a sense to make the voltages across the first and second smoothing capacitors equal.

Abstract: An arc welder includes an inverter for converting a DC voltage to a RF voltage which, then, is rectified by a rectifier. The output of the rectifier is smoothed by a DC reactor. A RF generator provides RF current to flow between a workpiece and a main electrode of the welder forming a welder load, which initiates arcing between the workpiece and the main electrode. Initiation of arcing causes output current from the DC reactor to be supplied to the welder load, so that steady-state arcing is established. The DC reactor has a relatively small inductance which permit the output current from the DC reactor to reach a value required for establishing the steady-state arcing within a time period during which the RF generator provides RF current. The RF voltage from the inverter has a relatively high frequency so that the output current from the DC reactor can sustain the steady-state arcing.