This paper illustrates how special converters equipped with PassThru™ mode can be useful when the circuit’s input voltage is too high or too low to power a load. It gives examples of how PassThru mode is used with buck-boost regulators and boost regulators to increase power supply efficiency and improve EMC behavior.

In some applications, an existing supply voltage can drive a load directly without the use of an additional voltage converter. At certain times, when unusual operating states occur, the supply voltage may be too high or too low to supply a load directly. In these cases, special voltage converters that have been optimized for this type of operation can be used. An example of an application is an industrial 24 V system. Let’s assume a load requires a 24 V supply voltage, but the available 24 V voltage rail can sometimes go up to 38 V or drop to 15 V. These voltages fall outside of the permissible supply voltage range of the load. For these applications, classic boost regulators or buck-boost regulators can be used…