Circuits & Schematics Light

One option for driving high-brightness LEDs uses the standard stepdown buck converter (Figure 1). The sense resistor, R S , generates a feedback voltage, V FB , that sets the desired LED current, I LED , according to the equation Figure 1. A ...

This circuit of only a few components is powered by two AA batteries and features a mode that extends its power savings. Imagine a smart light switch which not only automatically turns itself on when it gets dark, but also adjusts its level of ...

Testing the system Testing was done at various sunlight intensities. For any given sunlight intensity, V PV , I PV , V M , I M , etc., are measured. Figure 5 shows the variation of PV power (P PVON ), converter power (P M ), and total power (P TOT ...

The PV-pushback-effect with solar panels can control backup power and provide constant light output. Solar day lamps (SDLs) are made by simply connecting an LED array to a solar photovoltaic (PV) panel. SDLs represent a highly cost-effective way of ...

Using a blue LED can pose problems when available power-supply voltages don't meet or exceed the LED's 3 V forward-voltage drop. This Design Idea shows how to drive a blue LED from a 3 V battery or another power supply. The circuit in ...

As the latest generation of new LEDs achieves higher levels of power and efficiency, use of these devices extends to new areas, such as flashlights and vehicular applications. High-power LEDs are finding use even in ambient lighting, long the sole ...

Streetlights, emergency lights, and security lights must automatically turn on when it gets dark. You base the control circuit on the resistance of a photoresistor or another LDR (light-dependent resistor) that varies with light intensity. An ...

Many portable appliances and other products that must operate from a single cell are restricted to working at very low voltages. It is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5 V. The ability to flash the ...

Self-powered isolation amplifiers, which need no external isolated power supply, provide versatile and convenient interfaces in many applications that require galvanic isolation of the signal source. Examples of such applications include circuits ...

Whether you use them as indicators or to provide illumination, LEDs are hard to beat in efficiency, reliability, and cost. White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages ...