Output Current Variation Research Articles

Analysis of Output Current Characteristics for Higher Order Primary Compensation in Inductive Power Transfer Systems

Constant output current is desirable for some wireless power transmission applications such as charging batteries and driving light-emitting diodes. Converters having an inherently small output current fluctuation versus variations of load and coupling are attractive solutions since such converters can be controlled to achieve constant current with minimum control efforts. In this paper, the impedance conditions and the output current characteristics for different compensation types are presented. It is shown that the types of compensation producing load- and coupling-independent output current at the designed operating point as well as having a unimodal dependence of the output current on coupling would achieve better output current performance against variations of load and coupling. The sensitivities of the output current to parameter variation of typical compensation types are quantitatively analyzed and compared. Analytical results indicate that the primary parallel–series and secondary series compensation, which produces output current that exhibits a unimodal relationship with coupling and is nearly immune to coupling variation at the designed operating point, has the smallest output current fluctuation versus variation of the coupling coefficient. Finally, a comparison of experimental results of different types of compensation is presented for verification.

None Operational Amplifier (OPA) Based: Design of Analogous Bandgap Reference Voltage

By using 0.35-um CMOS process, this work achieves a design of analogous band-gap reference voltage circuit with low temperature coefficient. The proposed circuit operates at 3V and generates a reference current of 44 uA. The HSPICE simulation results show the temperature coefficient of this circuit is 23 ppm/°C at range of -10 °C to 100 °C, and the line regulation (the ratio of output current variation to supply voltage variation) is estimated as 1.95 uA/V from supply voltage variation of 3 V to 5 V. The experimental chip is fabricated and measured. The circuit provides adjustable capability for output voltage among temperature variation of -10 - 100 °C. The chip area is 534 × 695 um2. In this new design, the operational amplifier is not necessary. The chip design effort can be great reduced.

An Adaptive High-Precision OCP Control Scheme for Flyback AC/DC Converters

Flyback topology has been widely used in low-power applications due to its simplicity, wide input voltage range, low cost, and low standby power. However, conventional over current protection (OCP) control scheme in flyback converters cannot meet the high precision constant current (CC) requirement in battery charger and LED applications. The proposed adaptive high-precision OCP control scheme can be widely used in ac/dc flyback converters to improve their CC accuracy. It consists of an OCP-Comp circuit and a Vpump circuit to detect the primary current in current cycle and adjust it in next cycle adaptively. The proposed OCP control scheme has been implemented in a controller IC adding no extra pin and achieves a significant improvement in output current accuracy compared to conventional OCP schemes. Test results show that the output current variation of the proposed prototype is less than ±0.6% when the input line voltage changes from 85 to 265 Vac.

A single-stage primary side controlled flyback LED driver

In applications for indoor illumination, light-emitting diode (LED) is widely used. The requirements for small volume, low cost and high reliability LED driver makes additional challenges. Conventional single stage flyback LED driver requires additional feedback components such as opto-coupler or auxiliary winding. These components take space on printed circuit board, reduce the reliability and may introduce interference into the feedback loop. A 2.7 W LED driver without opto-coupler or auxiliary winding is proposed. With novel demagnetizing time sampling method, the feedback circuit is fully integrated into the controller, leaving few off-chip components. The controller integrated circuit (IC) is fabricated in CSMC 0.8 μm 500 V BCD process to verify the proposed sampling method. A power MOS is also integrated into the controller IC to simplify the off-chip circuit further. A prototype of the driver is also built and optimized to reduce the volume into 1.6 × 2.4 × 1.4 cm3. The experimental results show that the efficiency is above 72.75 % and the average output current variation is less than 5 % under universal input voltage.

High precision control technique for constant current regulation in primary‐side regulation systems

A constant current control technique for a primary-side control system is proposed to realise high precision output current regulation. With the novel ring detect and demagnetisation portion control technique, the ending time of demagnetisation can be accurately determined and the portion of demagnetisation in a switching period remains precisely the same. The simulation results show that with this control technique, the variation of output current is less than ±1.5% of the target value.

Temperature dependence of spin-torque-driven self-oscillations

We have measured the temperature dependence of spin-torque-driven self-oscillations in point-contact nano-oscillators for both in-plane and out-of-plane applied fields. We find that the linewidth for both field geometries is qualitatively similar. In the absence of observable low-frequency noise, at high temperatures the linewidth decreases roughly linearly as the temperature decreases. However, extrapolation of the quasilinear region to a zero-temperature linewidth intercept can yield either a positive or negative value. This variation in the zero-temperature linewidth intercept indicates that a range of mechanisms must be involved in setting the linewidth. When $1/f$ noise is present in the device power spectrum, the linewidth varies quasiexponentially with temperature. While the linewidth versus temperature behavior is similar for both in-plane and out-of-plane applied fields, their output power versus current variation with temperature is qualitatively different.

Output current variation and polarity effect by electric field and ion-pair non-uniformity inside thimble-type ionization chamber

A new analytic approach considering both electric field and ion-pair non-uniformity has been proposed to accurately analyze the design characteristics of an ionization chamber and to interpret measurements. It is commonly assumed that ion-pairs are generated uniformly in the air volume, but such an assumption ignores various source and geometry conditions. The new approach was applied to angular dependence analysis and to polarity effect assessment in an ionization chamber. For the angular dependence analysis, whole, uniform, and non-uniform output currents were calculated as a function of the irradiation angle for an 241Am gamma-ray source. The non-uniform output current proposed in this paper was found to be closer to the measured one. This is because the non-uniform output current takes into account the ion-pair distribution in the air volume as well as the active volume determined by the electric field. For the polarity effect assessment, the amount of field distortion due to potential difference and actual current difference was calculated. Previous methods cannot appropriately estimate the variation of polarity effect because they ignore the influence of the ion-pair distribution. The polarity effect assessment using the non-uniform output current can be more useful for obtaining the practical current difference, because this assessment considers both the variation of active volume and the ion-pair non-uniformity according to source conditions such as the irradiation angle and the distance. It is important to precisely calculate not only the active volume, but also the variation in the ion-pair distribution.

Design and Analysis of an Ultrahigh-Speed Glitch-Free Fully Differential Charge Pump With Minimum Output Current Variation and Accurate Matching

An ultrahigh-speed fully differential charge pump with minimum current mismatch and variation is proposed in this brief. A mismatch suppression circuit is employed to minimize the mismatch between the charging and discharging currents, which minimizes the steady-state phase error in a phase-locked loop (PLL). A variation suppression circuit is proposed to minimize output current variation with the change of output voltage, which reduces the variation of the bandwidth in a PLL. Techniques are proposed to suppress both low-speed glitches and high-speed glitches in the output current to allow glitch-free operation of the charge pump with ultrafast input pulses. The differential charge pump is designed and simulated under the power supply of 3.3 V in TSMC 0.35-mum CMOS technology to verify the effectiveness of the proposed techniques

Current-source a-Si:H thin-film transistor circuit for active-matrix organic light-emitting displays

We describe a four thin-film-transistor (TFT) circuit based on hydrogenated amorphous silicon (a-Si:H) technology. This circuit can provide a constant output current level and can be automatically adjusted for TFT threshold voltage variations. The experimental results indicated that, for TFT threshold voltage shift as large as /spl sim/3 V, the output current variations can be less than 1 and 5% for high (/spl ges/0.5 μA) and low (/spl les/0.1 μA) current levels, respectively. This circuit can potentially be used for the active-matrix organic light-emitting displays (AM-OLEDs).

Performance analysis of commercial scale Ar–Cs disk MHD generator connected to electric power system with synchronous generator

Performance analyses of a commercial scale closed-cycle MHD disk generator are performed. A large scale MHD generator, superconducting magnet, inversion system and synchronous generator are designed. The MHD generator is operated with Ar–Cs plasma and connected to the ac power infinite bus through line-commutated inverters, while the synchronous generator is operated in parallel. The thermal input is 1000 MW, and the power output is 400 and 200 MW, from the MHD and synchronous generators. Fault analyses have found that rather large fluctuations within the MHD generator are induced by faults of the inverter and power transmission line, but control of the inverters can recover the MHD generation system to normal operation within 0.15 s. The feature of behavior of the MHD generator is the same with or without the parallel operation of the synchronous generator. The interaction between the MHD and the synchronous generators is small, and this feature is much different from the open-cycle MHD generation system, since the variation of output current of the closed-cycle disk MHD generator is much smaller compared with open-cycle MHD generators.

97/04707 Characterization of two modified lithium vanadate cathode materials in secondary lithium batteries: Yu, A. and Kumagai, N. Proc. Electrochem. Soc., 1997, 97-18 (Batteries for Portable Applications and Electric Vehicles), 215–232

Performance analyses of a commercial scale closed-cycle MHD disk generator are performed. A large scale MHD generator, superconducting magnet, inversion system and synchronous generator are designed. The MHD generator is operated with Ar–Cs plasma and connected to the ac power infinite bus through line-commutated inverters, while the synchronous generator is operated in parallel. The thermal input is 1000 MW, and the power output is 400 and 200 MW, from the MHD and synchronous generators. Fault analyses have found that rather large fluctuations within the MHD generator are induced by faults of the inverter and power transmission line, but control of the inverters can recover the MHD generation system to normal operation within 0.15 s. The feature of behavior of the MHD generator is the same with or without the parallel operation of the synchronous generator. The interaction between the MHD and the synchronous generators is small, and this feature is much different from the open-cycle MHD generation system, since the variation of output current of the closed-cycle disk MHD generator is much smaller compared with open-cycle MHD generators.

An improved Clark-type galvanic sensor for dissolved oxygen

A novel Clark-type galvanic oxygen sensor has been fabricated, in which the indicator electrode is made from an industrially produced Ni Cu alloy containing ≃ 30% Ni. The exposed are of the tubular-shaped indicator electrode is about 10 cm 2. The anodeis prepared from cadmium. The sensor is filled with 6 M aqueous KOH solution. The 95% response time of the device is on average 50 s, its residual current at zero oxygen concentration is negligible, its lifetime is one to two years, its output-current variation is less than 5% in a one-year period and an excellent linear calibration curve for oxygen concentrations in the range 0–17 mg l −1 is observed.

Current programmed control nonresonant coupled parallel resonant convertor

In the nonresonant coupled parallel resonant convertor operated below unity gain, the inductor current at the switching points has a maximum value which is determined by the convertor gain and the output load. By switching transistors at predetermined inductor current levels, it is possible to regulate the output voltage due to output current and input voltage variations. The peak inductor current, which can be limited to desirable values, is regulated by the control circuit. By using nonresonant coupling in the output circuit, the maximum capacitor voltage is clamped to the output voltage level; thus, the convertor has low voltage stresses. In the paper, the authors introduce the analysis and design of this convertor. The performance characteristics of the convertor are also presented. Computer simulation results are used to verify the authors' theoretical work. >

A Theoretical Study of the Three-Element Vacuum Tube

Starting with a functional relation between the plate current and the grid and plate voltages, the plate current variation is deduced to a sufficient degree of approximation in terms of constants of the tube and the grid voltage variation (for pure resistance in the output circuit). The requirements of amplification, modulation, and detection are then deduced from the equations obtained. Heterodyne amplification is discussed, and it is held that within the working range of the tube this amplification is the ratio of the amplitudes of the locally and remotely generated waves provided the latter is small as compared with the former. The general problem of output current variation with an impedance in the output circuit is then considered, and the production of harmonic frequencies noted.