Circuits & Schematics - Supply

Switching power supplies can be notorious noise generators. You should prevent this noise, which is conducted, radiated, or both, from returning to the input source, where it can potentially wreak havoc on other devices operating from the same ...

LM317 fans will recognize Figure 1 as the traditional LM317 constant current source topology. It closely regulates I OUT = V ADJ /R S by forcing the OUTPUT pin to be V ADJ = 1.25 V positive relative to the ADJ pin. Thus, I OUT = V ADJ /R S to a ...

The circuit of Figure 1 is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3 V source and adjusts the total LED current from 1 to ...

When designing devices with microcontrollers (MCU), I like to use some of the analog-to-digital converter (ADC) inputs to measure onboard voltages along with all the required sensors inputs. This means I often run out of ADC inputs. So presented ...

There’s been a lot of interesting conversation and DI teamwork lately devising circuits for ON/OFF power control using inexpensive momentary-contact switches (See Ref. 1 Ref. 4 ). Most of these designs have incorporated edge triggered ...

A stable voltage from an input supply that is higher and lower than the output is often required. A common solution is to use a boost converter followed by an LDO as shown in Figure 1. The boost converter is configured to accept voltages ranging ...

It’s remarkable how many switching regulator chips use the same basic two-resistor network for output voltage programming. Figure 1 illustrates this feature in a typical (buck type) regulator. See R 1 and R 2 where: Quantitatively, the V ...

This design idea reprises another “1 A, 20 V, PWM controlled current source” ( Ref. 1 ). Like the earlier circuit, this design integrates an LM3x7 adjustable regulator with a PWM DAC to make a programmable 20 V, 1 A current source. It ...

Rheostats Rheostats are simple and ubiquitous circuit elements, usually comprising a potentiometer connected as an adjustable two terminal resistor. The availability of manual pots with resistances spanning ohms to megohms makes the optimum choice ...

This design idea revisits another: “PWM power DAC incorporates an LM317” ( Ref. 1 ). Like the earlier circuit, this one implements a power DAC by integrating an LM317 positive regulator into a mostly passive PWM topology. It exploits ...