For output voltages that must be higher or lower than the input, there are other topologies like buck-boost, Ćuk, or SEPIC. In general, DC-DC converters can change their pulse duty cycle to modify the amount of energy transferred per switching cycle, and use a closed-loop control architecture to handle changes in input or output conditions. The control loop has a very fast bandwidth (usually hundreds of kHz) and can quickly respond to input voltage spikes or load transients.