Abstract: An off-line switching power supply is described which controls the switching transistor of a fly-back circuit in such a fashion as to achieve better than 0.99 power factor control. The technique used for power factor control allows the switching power supply to operate either from AC or DC sources. The power supply operating from an AC source will accept all international voltages and line frequencies as input to produce a well-regulated DC output. The inductor of the fly-back circuit is maintained at the verge of continuous/discontinuous operation by the power factor control circuit to achieve a high efficiency operation and to minimize switching losses. The power factor correction circuit uses pulsewidth modulation and frequency modulation to control the switching transistor and maintain a high power factor under varying line and load conditions. The power supply also includes integral current limiting protection and RFI filtering for safe and quiet operation.
Abstract: A regenerative d-c power supply comprises a bridge rectifier, a series-connected smoothing choke, a shunt-connected filter capacitor and a switching circuit consisting of a first diode disposed in a positive line of the d-c power supply between the smoothing choke and one terminal of the capacitor, a second diode disposed in a negative line of the power supply between another terminal of the capacitor and the rectifier and a pair of converter valves in the form of transistors connecting the cathodes of the diodes to one another and the anodes of the diodes to one another. Each converter valve is operated in the forward energy transmission direction by a respective first pulse sequence having pulses staggered in time with respect to the pulses of the other first pulse sequence. The converter valves are operated in the reverse energy transmission direction by respective second pulse sequences each having pulses staggered in time with respect to the pulses of the other second pulse sequence.
Abstract: An apparatus for converting a single phase electrical signal into a three phase electrical signal is disclosed. A converter includes a rectifier connectable to a single phase electrical power source. One output of the rectifier is connected through a smoothing ciruit to four switching transistors. The other output of the rectifier is connected to center taps of a first and a second load coil. The first phase load coil is connected across a first pair of the switching transistors and the second phase load coil is connected across a second pair of the switching transistors. Third and fourth phase load coils are connected to opposite sides of the first and second phase load coils. The first, second, and third phase load coils are delta connected and the first, second, and fourth phase load coils are delta connected. The first and second pairs of switching transistors are controlled by first and second pairs of phase shifting signals.
Abstract: A pair of ratioed emitter size transistors is operated to produce a .DELTA.V.sub.BE. A second pair of transistors is coupled in series with the first pair and matched therewith so as to produce 2.DELTA.V.sub.BE. This differential voltage appears across a resistor coupled in series with the low current density transistors. This circuit combination produces a current that is proportional to absolute temperature (PTAT) and which is passed through a suitable value resistor to develop a PTAT voltage. This voltage is combined with a negative temperature coefficient voltage produced by forward biased series connected diodes so as to produce a combined voltage that is a multiple of the semiconductor bandgap extrapolated to absolute zero. The diodes are operated at very low current levels so that the circuit requires a very low operating current.
Abstract: An AC motor drive includes a power converter which supplies current to a DC bus from three-phase power lines. An inverter drives the motor from power delivered to the DC bus and it regenerates power to the DC bus when the motor is decelerated. The power converter in turn regenerates the power to the power lines by controlling line current such that it is substantially in-phase with the applied line voltages. Current overload protection is provided for the transistor switches employed in the power converter bridge circuit.