Pulse Frequency Modulation (PFM)
Pulse Frequency Modulation Operation (PFM) is a derivative of Switch-Mode Operation that improves power conversion efficiency of a switching regulator at light load currents. This feature is especially useful for systems operating in a “standby” mode where that power consumption is orders of magnitude lower than the fully active mode. When the output current drops below a pre-determined threshold the regulator begins to “skip” pulses which reduces “switching losses”. At light output currents these switching losses tend to dominate the overall losses for the regulator circuit. Figure 4 shows a comparison between PWM and PFM mode operation for a 1A switching regulator. It can be seen that the PFM mode can increase a 20% efficiency operation to >60% efficiency. This light load efficiency can dramatically improve real world performance such as standby time for mobile phones.

Figure 4 - PWM vs. PFM Operation


Summit’s PFM technology is featured in the following products:

SMB122
SMB135