In succession to the preceding article, we explain the selection of peripheral circuit components for the BM1R00147F power supply IC that was previously selected. Here, we focus on C1 and R3 at the MAX_TON pin and on the VCC pin.
In the case of the High Side Type, the secondary-side GND and the IC GND pin SR_GND are not common, and so a separate power supply must be provided by adding an auxiliary power supply circuit as in VCC power supply method example 2, or by providing auxiliary windings on the transformer secondary side as in VCC power supply method example 3.
For stable IC operation, a VCC pin capacitor CVCC of 1 μF or above should be selected. If an extremely large capacitance is used, the startup time is lengthened, so caution should be exercised. In this design example, a 10 μF capacitor is employed.
・A capacitor and resistor are connected in series at the MAX_TON pin of the BM1R00147F to reduce noise.
・The above capacitor and resistor are also used for phase compensation at the MAX_TON pin, and so they must always be connected.
・In the case of a Low Side Type design, power can be easily supplied to the VCC pin of the BM1R00147F from the secondary-side VOUT pin.
・In the case of the High Side Type, a separate power supply must be provided by adding an auxiliary power supply circuit or by providing auxiliary windings on the transformer secondary side.