Boost converter is a kind of DC / DC switching power supply, which raises the non regulated DC input voltage to achieve a stable high output voltage. Similar to buck converters, boost converters rely on inductors, diodes, capacitors and switches to regulate the output voltage, but their configurations are different. The following simplified circuit diagram shows the current path during switching of the boost converter.

    In the step-up converter, the output voltage changes according to the ratio of the PWM signal to the on switch, which is equal to or greater than the input voltage. Since power is saved, a boost converter that provides three times the input voltage can only provide one third of the current. However, boost converters are very common in battery powered equipment, for example, a set of 3V battery voltage supplies 5V circuits.

    The buck boost converter can provide a stable DC voltage output regardless of whether the input voltage is higher or lower than the output voltage. Buck boost converter circuits combine elements of buck converters and boost converters, but they are usually larger in size than both. The simplified circuit diagram below shows the common current paths during switching of the buck boost converter.

    You may find that the polarity of the output voltage in the circuit diagram is opposite to the input voltage, which will complicate the design. Buck boost converters also require more expensive devices because they have to withstand both high voltage when the highest voltage is input and high current when the lowest voltage is input. However, the buck boost converter is very suitable for a variety of applications, the most common of which is high-power LED lighting. For example, lead-acid batteries provide a nominal 9-14v voltage for a 12V LED constant load.