AC/DC and DC/DC power supplies usually are relatively rugged in regular operation. Nonetheless, some protection features are built into most of these units to ensure that they do not “self-destruct” or damage associated circuitry – primarily their loads – in the event of a failure or out-of-spec operational mode. (note: in strict terms, a power […]
basics
Power Status: battery monitors matter
For battery powered systems it can be useful to know something about the state of the battery in order to predict remaining battery life. With specific charge/discharge information, you could also manage battery consuming resources to maximize battery life. There are integrated circuits to help with either approach. For simple charge or discharge information, a […]
Stray current and parasitic capacitance in circuits at RF
Strange things can happen at high frequencies. It begins with stray current in your printed circuit board (PCB). What is stray current? Stray current starts with stray voltage, relating through Ohm’s Law (V=IR). Stray voltage refers to a situation where between two points, there exists a voltage potential that should not be there (and wouldn’t […]
What is inrush current?
Inrush (in-rush) current is a sudden large flow of current that exceeds the usual, steady-state operating current, and can be a problem for any circuit. Inrush is most often associated with turning on equipment. Inrush current can be caused by large-capacity decoupling capacitors that draw a lot of current as they initially get charged up. […]
Dimming LEDs
As the use of LEDs for area lighting has grown dramatically, with both the use of LED-based replacement bulbs as well as LED-based fixtures for new construction (called luminaires in the trade), the issue of dimming these LEDs becomes more critical. LEDs require a very different technique for dimming than the conventional legacy incandescent bulb. […]
How to power and configure LEDs
LEDs – light-emitting diodes – have largely supplanted other sources of light in many applications. They are used in applications ranging from small on/off power indicators, to small and large alphanumeric displays, to screen backlighting, and even for area and street illumination. It’s well known that LEDs are far more efficient than venerable incandescent lighting, […]
What is a charge pump and why is it useful? (Part 2)
(Part 1 looked at the basic function and operation of the charge-pump switched-capacitor voltage doubler. This versatile topology has some additional interesting considerations and permutations.) What about the capacitor? When MOSFET switches are used, the capacitor is sometimes called a “flying capacitor.” This is a designation which is a holdover from early days of electronics, […]
What is a charge pump and why is it useful? (Part 1)
It’s a very common challenge in circuits to need to convert an available DC source to a lower or higher voltage. For the high-to-low conversion, one option to use a low dropout regulator (LDO), but how to easily transform a lower voltage into a higher one? For AC voltages, the answer is well-known: use a […]
What’s the difference between current sourcing and sinking?
Current can flow in two different ways with respect to the load. Sensors often provide real-world, analog input for embedded applications. MCUs rely on sensors to be their electronic “senses” and actuators to physically interact with world. Interfacing with external devices requires some planning on the part of the designer to ensure efficient operation. One […]
What are amplifier classes and their relation to power efficiency (Part 2)?
In Part 1, we looked at Class A, B, AB, C, and D amplifiers. These designations are standardized, fully defined, and widely recognized. Now we’ll look at a few other topologies which are less well known but also used. The Class G amplifier is similar to the Class AB amplifier except that is uses two […]