This is one of the application for low voltage feedback in PWM. This circuit is called as synchronous buck feedback. This circuit is proposes an alternate method for feeding back an output voltage lower than the PWM internal error amplifier reference voltage. This is the figure of the circuit.
Normally the output voltage is higher than the error amplifier reference, and so a simple resistive divider between VOUT and ground sets the regulated voltage at the non-inverting input of the PWM error amplifier. However, when VOUT is less than the error amplifier reference voltage, the feedback voltage must be divided up instead of down. Dividing up implies that some additional voltage must be added to the feedback from another regulated voltage source.[Schematic’s source: Texas Instrument Notes].
Normally the output voltage is higher than the error amplifier reference, and so a simple resistive divider between VOUT and ground sets the regulated voltage at the non-inverting input of the PWM error amplifier. However, when VOUT is less than the error amplifier reference voltage, the feedback voltage must be divided up instead of down. Dividing up implies that some additional voltage must be added to the feedback from another regulated voltage source.[Schematic’s source: Texas Instrument Notes].
