Circuits & Schematics Supply - 20

Stepper motors are synchronous motors that step at the pulse rate of the driving signal. For the motor to move quickly, the stepping rate must be fast. However, because of motor and load inertia, the motor often cannot go from 0 rpm to the desired ...

A perennial challenge in power-supply design is the safe and speedy discharge, or “dump,” at turn-off of the large amount of energy stored in the postrectification filter capacitors. This energy, CV 2 /2, can usually reach tens of ...

In a standard dc-dc converter, a resistor divider typically defines a fixed output voltage. However, applications like programmable output voltage power supplies and motor control circuits require dynamic control of the dc-dc converter's output ...

Speed controllers have long exploited the reverse-EMF characteristics of dc motors to control their speed. These linear driver circuits use power op amps to create a negative resistance drive to the motor that counteracts the voltage drop in the ...

The circuit in Figure 1 serves as a variable, current-sink load for testing voltage sources. You use digital commands to set the load current of the device under test over a wide range, independently of the device under test's output voltage. ...

The circuit in Figure 1 derives its power from a USB port and produces 5 and 3.3 V supply rails for portable devices, such as digital cameras, MP3 players, and PDAs. The circuit allows the port to maintain communications while, for example, ...

This Design Idea describes an enhancement to a previous one ( Reference 1 ). The circuit in Figure 1 uses a normally open SPST pushbutton switch, S 1 , instead of the SPDT switch that the original design required. You can use a membrane switch to ...

I recently needed to control nine seven-segment displays for a microcontroller's serial port. The complication I faced was the need to provide a continuous brightness adjustment for all the digits from completely dark to fully bright. I ...

In dc/dc-converter applications in which the input voltage may be lower or higher than the output voltage, you can use either a flyback converter or a SEPIC (single-ended-primary-inductor converter). SEPICs offer lower input-current ripple and ...

It is always desirable to use a low-battery indicator that consumes as little power as possible. For a 9 V, 450-mAhr alkaline battery, a 50-µA low-battery indicator can by itself run the battery down in a little more than a year. ...