The more efficient option when input voltage always exceeds the LED voltage is a step-down or buck regulator. As with linear regulators, this must be an adjustable type, and the same method can be used to turn almost any buck regulator into a constant current source for LEDs. Buck regulators enjoy high efficiency and eliminate the need for a heatsink, at the cost of a more complex circuit and the addition of switching noise. Many recent buck regulators switch at 1 MHz and above, making their external components so small that at currents under 1A they may actually use less space than a linear regulator.
National offers a diverse portfolio of constant-current regulators for driving high power LEDs
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| Product ID | VIN Range (V) | VOUT (V) | ILED (A) | No. of LED | Topology | Key Features |
| LM3409/HV | 6.0 to 42/6.0 to 75 | Up to 42/75 | 3.0+ | 1 to 9/15 | Buck | External high-side P-FET current source with differential current sensing and analog current adjust |
| LM3421 | 4.5 to 75 | Adjustable | 3.0+ | 1 to 16 | Floating Buck | 20 mV to 1.235V adjustable differential current sense voltage, 50 kHz max PWM dimming |
| LM3423 | 4.5 to 75 | Adjustable | 3.0+ | 1 to 16 | Floating Buck | 20 mV to 1.235V adjustable differential current sense voltage, 50 kHz max PWM dimming; fault timer; LED ready flag; high-side dimming |
| LM3429 | 4.5 to 75 | Adjustable | 3.0+ | 1 to 20 | Buck | 50 mV to 1:25 adjustable high-side current-sense voltage, analog and PWM dimming |
| LM3445 | 80 to 270 | Adjustable | 1+ | 1 to 14+ | Floating Buck | Integrated TRIAC dim decoder circuit for LED dimming. Adaptive programmable offline allows for constant ripple current. No 120/100 Hz flicker |