Voltage regulator

About: Voltage regulator is a research topic. Over the lifetime, 33536 publications have been published within this topic receiving 350859 citations.

Method and apparatus for voltage regulation in multi-output switched mode power supplies

Abstract: A step-down switched-mode power supply circuit includes a transformer having at least one primary winding and at least one secondary winding, a current sensing device for sensing a current through a primary winding of the transformer, a first switch and a second switch, a first comparator for determining if the current through the current sensing device exceeds a threshold, a voltage regulator coupled to the secondary winding to produce a regulated voltage, a second comparator for determining if the regulated voltage has drooped below an acceptable level, a counter coupled to the second comparator for generating a signal having a fixed number of switch cycles, and control circuitry for generating signals controlling the first switch and the second switch and responsive to the first comparator to enter a power saving mode disabling the signals, and to the second comparator to temporarily exit the power saving mode for a fixed number of cycles when the regulated voltage has drooped below an acceptable level.

Predictive modulation schemes to reduce common-mode voltage in three-phase inverters-fed AC drive systems

Abstract: Pulse width modulation controlled inverters produce common-mode voltage, which has been reported to cause many system drawbacks. This voltage along with high d v /d t raises leakage currents which can result in serious problems such as motor damage and electromagnetic interference to the surrounding equipment. Also common-mode voltage is responsible for bearing failure and overvoltage stress to the winding insulation of an AC motor. Therefore knowledge of reducing common-mode voltage is essential to provide a correct insight into the design of the drive system. Previous methods for common-mode voltage reduction cause extra harmonic in output currents, since they are based on voltage control. This study proposes new modulation strategies based on predictive current control (PCC) for three-phase pulse width modulation inverters-fed AC motor drive systems which mitigate the common-mode voltage and moreover, decrease the harmonic contents of output currents. As PCC can be employed in low voltage and medium voltage drive applications, the proposed strategies have been implemented on two-level and three-level neutral-point clamped inverter. A comparative study of proposed techniques with traditional ones has been carried out from the output current total harmonic distortion point of view. Simulation results and mathematical analyses, along with experimental tests for two-level inverter using Texas Instrument DSP model TMS320F28335, confirm that the new strategies improve behavior of drive systems in comparison with previous methods.

Diode-assisted buck-boost voltage source inverters

Abstract: This paper proposes buck-boost voltage source inverters with a unique X-shape diode-capacitor network inserted between inverter circuitry and dc source for producing a large voltage boost gain. Comparing with other voltage buck-boost techniques, the presented topologies with only a little more passive components can significantly enhance voltage boost capability for dc-ac inversion. With different front-end circuitries, the diode-assisted buck-boost inverters can show different operational principle and voltage boost ratio. Carefully analyzing the operational principle for the inherent energy charging and discharging processes of passive components reveals that the dc-link voltage can alternate between two levels, which therefore demonstrate the phenomena that the specified modulation schemes should note. A modulation scheme that can achieve optimized harmonic switching is first designed with symmetrical state placement in each switching sequence to avoid unnecessary voltage stress across both passive and active components. To reduce the total commutation count, the designed modulation scheme is then modified without increasing voltage stress. All theoretical findings were verified experimentally using a number of scale-down laboratory prototypes.

Phase locked loop circuit having regulator

Abstract: Embodiments of present invention provide a circuit including a voltage regulator, a phase frequency detector, a charge pump, a low pass filter a control-voltage generating circuit and a voltage controlled oscillator. In a first mode of operation the voltage controlled oscillator produces an output clock in accordance with a control voltage produced from the control-voltage generating circuit and the output voltage of the voltage regulator. In a second mode of operation, the voltage controlled oscillator produces an output clock in accordance with a control voltage from the low pass filter and the output voltage of the voltage regulator.