I want to drive my LED circuit at 40-60% duty cycle to reduce the power consumption. How can I do this without using any microcontroller? Is there any switching IC to do this?

Input voltage to the LED panel is 5 volts.
Every LED has a series resistor. And then they are connected in parallel.
4 LEDs: 3 volts, 20 mA.

EDIT: I don't want to use many components. Something like op-amp ICs; we can just select two resistors based on the gain requirements to amplify the signal.


closed as unclear what you're asking by brhans, Voltage Spike, uint128_t, Andrew, ThreePhaseEel Jan 29 '17 at 4:30

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    \$\begingroup\$ Here's a great, but not very cheap, single chip solution. \$\endgroup\$ – uint128_t Jan 26 '17 at 23:46
  • \$\begingroup\$ I think the transistor flashers Gilhad mentioned are as simple as is humanly possible, it's only needs three components, a resistor, a capacitor and a transistor wired in backwards (not including the power source and the LED). \$\endgroup\$ – Sam Jan 26 '17 at 23:48
  • \$\begingroup\$ You could use a 555 OR A microcontroller. No need to use both. \$\endgroup\$ – Passerby Jan 27 '17 at 0:18

Why not just increase the current-limiting resistor values? No additional components required.

  • \$\begingroup\$ I wanted to know any simple method I could use. I could use your suggestion for LEDs. But, If I want them to vary over time as I want then it may not be possible. \$\endgroup\$ – user5311361 Jan 29 '17 at 7:57

You can use just transistor or two and some resistors/capacitors to adjust the duty cycle and frequency


eventually you can send your signal on/off as a power source of such oscilators.

Alternativelly you can restrict the current with something like



A simple circuit would be to use a Schmitt-trigger oscillator to generate a square wave with 1 resistor and 1 capacitor to get 50% duty cycle.

And then use this to drive the gate of an N-channel MOSFET or base of an NPN to switch.

If you want just a single Schmitt-trigger inverter in a small size, just Google "TinyLogic" (Fairchild's series) or "Little Logic" (TI's series).

enter image description here

Schematic is from http://electronics-course.com/schmitt-trigger-oscillator which has a good explanation of how this simple oscillator works.

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    \$\begingroup\$ I thought about suggesting a 74x14 to meet his (not overly sensible) minimalist spec. Fun to see somebody beat me to it. LS probably not the best choice. HC arguably better or even HCT .Most LEDs will need an output buffer. His 20 mA may be per LED or for 4. Jelly bean FET suffices. \$\endgroup\$ – Russell McMahon Jan 27 '17 at 11:18
  • \$\begingroup\$ Thanks Russell. Glad you mentioned HC; that would be my preference. Some inverter ICs can even drive the LED directly. For example the TI "Little Logic" one can drive 32 mA with output 0.55V to the rail at 4.5V power supply. Can also use several in parallel for higher output drive. Up the OP to research and/or ask more questions. \$\endgroup\$ – Vince Patron Jan 27 '17 at 18:18
  • \$\begingroup\$ The 74xx14 is amongst my favourite devices. I've used variants since pre LS, when a TTL 7414 was about all that was available. CMOS versions greatly improved their utility. I've used them for oscillators (of course), delays, mono stables, PWM generation, Audio amps (! :-) ), and probably several other things. ... \$\endgroup\$ – Russell McMahon Jan 27 '17 at 19:14
  • \$\begingroup\$ Give me a few 74xC14, LM324, TL431, BC337/327 (and power MOSFETs as requisite) and a place to stand and I can move the earth :-). (Well, maybe not quite). \$\endgroup\$ – Russell McMahon Jan 27 '17 at 19:14

There are many ways to generate own . Without knowing what you consider better or best, it is hard to suggest.

I would use anpamp (like audio or headphone amplifiers) if I were you.

  • \$\begingroup\$ Please see my edit. I want to use minimal components. Few resistors should be good to generate PWM. \$\endgroup\$ – user5311361 Jan 26 '17 at 23:38
  • \$\begingroup\$ Resistors only cannot create PWM. But you can restrict the current with the resistors \$\endgroup\$ – gilhad Jan 26 '17 at 23:39

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