AN L5991-BASED CONVERTER WITH TEMPORARY EXTRA POWER CAPABILITY
Claudio Adragna · 2003
In some applications the SMPS, normally supposed to deliver a certain amount of power, from time to time undergoes load peaks that can be even two or more times as much. Such peaks are often too long to be properly handled by oversizing the output capacitors, but short if compared to the thermal time constants of the power components. Typical examples of such loads are motors and audio systems. In this case, designing the SMPS for the peak power demand from the load would lead to a poorly used and more expensive system. It is more cost-effective to design for the maximum continuous power and allow the peak power to pass. However, if for any reason the load demands such peak power level for a long time, some of the power components, not sized for withstanding this, will definitely fail unless the system is stopped somehow. In this application note a design example of such a system, based on the ST's advanced PWM control- ler L5991, is carried out.