Boost converter

Like a buck, a boost converter uses an inductor and fast switching, but arranged so the output voltage is higher than the input. It lets a product run from one or two cells, hold a constant output as the battery discharges, or drive LEDs, displays and small motors.

Input current is higher than output current, because power in roughly equals power out plus losses, so the battery, connectors and traces must handle that higher current. A basic boost circuit cannot fully disconnect the load when switched off, since current can flow straight through from input to output, unless the chip has a true-shutdown feature.

Buck-boost converters handle cases where the input can be above or below the output, such as a lithium-ion cell powering a 3.3 V rail across its whole discharge range.