Equivalent input

Abstract: The efficiency of wireless power transfer (WPT) systems is highly dependent on the load, which may change in a wide range in field applications. Besides, the detuning of WPT systems caused by the component tolerance and aging of inductors and capacitors can also decrease the system efficiency. In order to track the maximum system efficiency under varied loads and detuning conditions in real time, an active single-phase rectifier (ASPR) with an auxiliary measurement coil (AMC) and its corresponding control method are proposed in this paper. Both the equivalent load impedance and the output voltage can be regulated by the ASPR and the inverter, separately. First, the fundamental harmonic analysis model is established to analyze the influence of the load and the detuning on the system efficiency. Second, the soft-switching conditions and the equivalent input impedance of ASPR with different phase shifts and pulse widths are investigated in detail. Then, the analysis of the AMC and the maximum efficiency control strategy are provided in detail. Finally, an 800-W prototype is set up to validate the performance of the proposed method. The experimental results show that with 10% tolerance of the resonant capacitor in the receiver side, the system efficiency with the proposed approach reaches 91.7% at rated 800-W load and 91.1% at 300-W light load, which has an improvement by 2% and 10% separately compared with the traditional diode rectifier.

Abstract: Compact low-voltage power-efficient operational amplifiers are described that are very suitable as very-large-scale-integration library cells because of the small die area of 0.08 mm/sup 2/ and the minimum supply voltage of 1.8 V. A key part of the circuit is the rail-to-rail class-AB output stage with folded mesh feedback control that combines power efficiency with operation down to 1.8 V and allows sufficient gain in a compact two-stage topology. A version with rail-to-rail input stage features a rail-to-rail input range for supply voltages down to 2.5 V. The dc gain of the op amps is more than 80 db while driving 10 k/spl Omega/, and the unity-gain frequency is 4 MHz with phase margin of 67/spl deg/ while driving 5 pF. The equivalent input noise voltage is 38 nV//spl radic/(Hz) at a frequency of 100 kHz. The amplifiers have been implemented in a standard digital 1.6-/spl mu/m complementary metal-oxide-semiconductor process.

Abstract: A low-noise CMOS instrumentation amplifier for low-frequency thermoelectric infrared sensor applications is described which uses a chopper technique to reduce low-frequency noise and offset. The offset reduction efficiency of the band-pass filter, implemented to reduce residual offset due to clock feedthrough, has been analyzed and experimentally verified. The circuit has been integrated in a transistor-only 1-/spl mu/m single-poly n-well CMOS process. It features a gain of 52 dB with a 500 Hz bandwidth and a common-mode rejection ratio (CMRR) of more than 70 dB. The equivalent input low frequency noise is 15 nV//spl radic/Hz. The typical residual input offset is 1.5 /spl mu/V. The amplifier power consumption is 1.3 mW.

Abstract: A theoretical analysis of threshold modulation in error diffusion is given. It is shown that spatial modulation of the threshold is mathematically identical to processing an equivalent input image with the standard error diffusion algorithm. The equivalent input is the sum of the original image with a high-pass-filtered version of the threshold spatial modulation. The filter is a function only of the weights used to distribute the errors. This result can be used to explain the several published observed effects of threshold modulation, such as edge enhancement and the effects of adding noise to the threshold.