High-Frequency Thyristor Chopper

Combined Bidirectional Buck-Boost DC-DC Chopper-Mode Inverters With High-Frequency Link

Frequency & duty cycle control considerations for soft-switching buck chopper

This paper presents considerations on the switching frequency and duty cycle & operating equations of softswitching BUCK chopper. These considerations are discussed and applied to selected soft-switching families such as ZVS-QRC, ZCS-QRC, ZVS-QSW-CV, ZCS-QSWCC, ZVT-PWM and ZCT-PWM [1]. The limitations on switching frequency and duty cycle are derived in terms of: chopper input voltage (Vg), cho...

Water-cooled Heat Load Chopper for High-energy Synchrotron Experiments

FIGURE 2. Traditional X-ray scattering experiment setup. Photo Credit: Argonne National Laboratory. In addition to the setup shown in Figure 2, time resolution at BioCARS is provided by precise synchronization of additional beam blocking equipment placed before the sample under test—two rotating disk choppers and a shutter [2]. The X-ray beam is intercepted by a watercooled heat load chopper wh...

Reflective Optical Chopper Used in NIST High-Power Laser Measurements

For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has several advantages over the use of wedge-shaped transparent materials (usually crystals) often used as beam splitters in this type of measurement s...

High frequency skin ultrasonography in systemic sclerosis

Background: Systemic sclerosis is an autoimmune connective tissue disorder which is characterised by cutaneous and internal organ fibrosis. Raynaud’s phenomenon is the earliest feature and may precede the onset of the disease by months to years. The heart, lungs, gastrointestinal tract, kidneys and other organs may be involved. Our aim was to evaluate skin thickness and echogenicity in systemic...