Unlike virtually every other active device, the power MOSFET is unusual in that its schematic symbol includes a parasitic device – the body diode. The body diode is intrinsic to the device’s structure. It remains despite a number of fundamental changes in power MOSFET structure and device designs including the two most common types today […]
FAQ
Current sources and why we need them
Engineers are all familiar and comfortable with voltage sources such as batteries or ac/dc supplies. The function of a voltage source, represented by a simple symbol is clear: Provide as little or as much current as needed (up to a maximum current limit) at a given, defined voltage; this voltage value may be fixed or […]
Basics of understanding power factor and power factor correction
In qualitative terms, power factor is a measure of the congruency of voltage and current ac waveforms imposed by a load on the power mains. Ignoring the relative phase of the two waveforms, the apparent power (S) is the simple product of the waveform amplitudes, S = V × I. Limiting our focus for now […]
What are the benefits of 48 V distribution?
Mains-connected computational resources have been powered primarily by 12-V distribution feeds for decades. The 12-V distribution potential has been a convenient choice because it lets designers route power efficiently throughout small-to-medium-sized systems and operate inexpensive, off-the-shelf fans and disk drives directly from the distribution voltage. Advances in the semiconductor fabrication process have driven significant reductions […]
What engineering school doesn’t teach
about ceramic capacitors
Ceramics comprise the most widely used non-polarized dielectrics. The reason is they offer attractive combinations of volumetric efficiency, manufacturability, and cost. Some applications – such as high-frequency RF signal chains and high-precision measurement circuits – take advantage of the parametric performance available from other dielectrics, but currently available ceramic formulations perform well in a wide […]
A better way to squelch transients
Modern dc-dc converters can double as compact transient suppressors in vehicular electrical systems characterized by a lot of hash on the battery power lines. By TIMOTHY HEGARTY, Non-isolated Power Solutions, Texas Instruments, Inc. THE proliferation of electronic subsystems in vehicles has created a need for small, inexpensive and highly reliable electronics able to operate in […]
Bumpless control for power factor correction
It can be difficult to correct for power factor in converters that have different conduction modes. A special technique can make corrections smoothly. By Joel Steenis, Alex Dumais, MICROCHIP TECHNOLOGY, INC. DESIGNERS of power factor correction (PFC) circuits will invariably notice distortion as the input current approaches zero. The distortion problem becomes progressively worse at […]
Wireless charging efficiency: how to measure in the real world
by John Perzow, Wireless Power Consortium When it comes to energy efficiency, there are significant differences in competing wireless charging methods. There are a lot of claims made about the energy efficiency of wireless charging schemes. Engineers are understandably skeptical. After all, it is hard to envision how two induction coils sitting some distance away from each […]
Multiple charging modes from a single amplifier
by Michael A. de Rooij, VP, Applications Engineering, Efficient Power Conversion Though there are two standards for charging appliances wirelessly, a single circuit can be devised to serve as a charging node for both of them. The good news about wireless charging techniques is that they do away with messy wiring that tethers phones and […]
Ceramic or electrolytic output capacitors in DC/DC converters – Why not both?
By Michael Score, Texas Instruments Switching power supplies are used in almost every end-equipment that needs a long battery life, low heat generation, or to meet ENERGY STAR® guidelines. When designing a switching power supply, it is difficult to decide which output capacitor type to use. Electrolytic capacitors have high equivalent series resistance (ESR), making […]
