PWM DC-DC Controllers with Built-In Start-Up Regulators Simplify Switching Power Supply Design

摘要

Although PWM DC-DC switching power converters are based on simple topologies, making practical power supplies out of them requires the addition of various functions such as start-up bias, soft-start, switch driving, regulation, short circuit protection, over-voltage protection, over-temperature protection, etc. Today, most of these functions are usually implemented within a compact DC-DC PWM controller integrated circuit. However, the problem of starting the DC-DC converter in telecom and other high-voltage applications (i.e., where the input voltage exceeds about 15V) is often not addressed. The controller requires a bias supply voltage to run from so that it can produce gate drive pulses and other required signals. But at turn-on the only voltage available is the input voltage, which, if it is greater than 15V, is typically too high to be used as the, bias and gate drive supply voltage.