Safety considerations: low power boost converters

In most battery powered applications the system voltages need to be generated with voltage regulation circuits, since battery voltage levels can vary over a wide range. Well designed power supply circuits should be able to deal with all possible error conditions specific for their configuration. All circuits require a certain level of supply voltage to operate their internal control circuitry. The behavior of the converter, as well as the output voltage level, cannot be predicted. For this reason, undervoltage lockout circuits are implemented in well designed power supply circuits. Generally, the current limit is implemented in the active switch which turns off the switch, if the current gets too high. Limiting the switch current in a boost converter can be effective only when the output voltage is higher than the input voltage. Should the input voltage get higher than the output voltage, a standard boost converter will operate with the rectifier always turned on.