Datasheet

(a) Current Paths when MOSFETs are Turned On
(b) Current Paths when MOSFETs are Turned Off
V
IN
V
OUT
ON
ON
V
IN
V
OUT
OFF
OFF
LM5015
www.ti.com SNVS538C –NOVEMBER 2007–REVISED APRIL 2013
Figure 17. Operating Modes of Two-Switch Forward Converter
Note that the power transformer primary receives the voltage of the nearly equal magnitude but opposite
polarities during the ON and OFF period of the power MOSFETs. In order to ensure the volt-second balance
between the magnetizing and demagnetizing intervals, the LM5015 limits the maximum duty cycle less than
50%. Therefore, an LM5015 Two-Switch Forward regulator always achieves a complete reset of the power
transformer during each switching cycle.
The LM5015 can also be used to implement a Two-Switch Flyback regulator (Figure 26). The voltage across the
MOSFETs employed in the Two-Switch Flyback converter is also clamped to the input voltage, allowing the input
voltage range to approach the rating of the MOSFETs. Generally the Flyback converter is simpler and costs less
than the Forward converter. However, the Flyback converter will have higher ripple current and voltages, and the
conversion efficiency is typically lower.
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