Application Note
R01AN6652EJ0100 Rev.1.00 Page 1 of 17
Dec.27.22
RL78/I1A
IPD-less Digital Switching Power Circuit Using RL78/I1A
Introduction
This application note provides an exampl e for achieving an IPD-less auxiliar y power circuit using an AC/DC
switching control IC RL78/I1A to reduce the cost of an AC/DC switching power circuit.
As an example, the following parts can be redu ced by removing IPD from TPW-RL78I1A-2C.
Increase/decrease in the number of parts after removing IPD from TPW-RL78I1A-2C
IC
One LYT0006D (Power Integrations) removed
Capacitor
4 capacitors removed
Diode
One diode removed
Inductor
One inductor removed
Resistor
3 resistors increased
Target Device
RL78/I1A
When applying the sample program covered in this application note to another micro computer, modify the
program according to the specifications f or the target microcomputer and conduct an ext ensive evaluati on of
the modified program.
RL78/I1A IPD-less Digit al Switching Power Circuit Using RL7 8/I1A
R01AN6652EJ0100 Rev.1.00 Page 2 of 17
Dec.27.22
Contents
1. Introduction ................................................................................................................................ 3
2. Overview of Circuit .................................................................................................................... 4
2.1 Overall Circuit .......................................................................................................................................... 4
3. Details of Circuit ........................................................................................................................ 5
3.1 Overall Configurati on of Auxiliary Po wer Circuit ..................................................................................... 5
3.1.1 Resistive Voltage Di vider Circuit ........................................................................................................... 7
3.1.1.1 Designing Resistance Values R1, R2, and R3 ................................................................................... 8
3.1.1.2 Capacitance C1 ................................................................................................................................... 8
3.1.2 LDO Operation Control ........................................................................................................................ 10
3.1.3 Power Supply Circuit Using PFC Transformer Auxiliary Winding ....................................................... 11
4. Example of Circuit Constant Design for Application ................................................................ 14
4.1 Design Example of Resistive Voltage Division Ratio and Ca pacitance (V
DD
current = 15 mA) ............ 14
4.2 Notes ..................................................................................................................................................... 15
4.2.1 V
CC
Voltage Generated by Resistive Voltage Divider Circuit .............................................................. 15
4.2.2 Considerations for Commercial Voltage Phase .................................................................................. 15
4.2.3 Selection of LDO ................................................................................................................................. 15
5. Reference Documents ............................................................................................................. 16
Revision History .............................................................................................................................. 17