Isolated Power Supplies for PLC I/O Modules. Industrial Systems - Factory Automation and Control

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Pierce Marshall
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1 Isolated Power Supplies for PLC I/O Modules Industrial Systems - Factory Automation and Control 1

2 Agenda Where and why? What are my choices? Fly-Buck - How does it work, what is important? Working principle Why duty cycles of 40-60% should be chosen Effects of leakage inductance 2

3 Where and why? Where: PLC modules where only limited power is required (1-4 W) Why: Isolated supplies for Multiplexer, Amplifier, ADC, Reference, Isolator Example Group Isolated Analog Input Module Isolated DC/DC power supply 15 LDO 3.3/5 DC/DC -15 LDO Isolated DC/DC 24 Backplane Protection REF Protection Protection MUX AMP ADC Data Isolation MCU Main System Protection 3

4 What are my choices? Push-Pull (SN650x) + Simple to use + Low cost - No regulation (especially critical for transformers with high turn ratios) Flyback (UCC28xxx) + Mid power (5W-100W) + Single primary switch + Wide in range + Good regulation (if secondary side regulated) - Needs optocoupler Fly-Buck (LM5xxx, TPS55010) + Low power (<10W) + Primary side regulation (no optocoupler) + Non-isolated + isolated outputs + Wide input range - Bad regulation Active Clamp, Half & Full Bridge oversized for power requirements (mostly used for >50W) 4

5 Fly-Buck How does it work, what is important? 5

6 Topology S 1 L t on out = in D = in t on + t off D L C + out out in C in S 2 GND C out out N = N sec N pri S 1 L pri L sec D 1 C sec sec in C in S 2 C pri pri GND iso t on pri = in D = in t on + t off GND sec = pri N D1 6

7 Working Principle t on - S 1 closed, S 2 open: Current flows through L pri, secondary side voltage / D 1 is reversed biased in No current flowing C in S 1 sw S 2 I pri L pri L sec D 1 D I sec C sec GND iso sec t off - S 1 open, S 2 closed: oltage across L pri and L sec reverses Current flowing GND C pri pri in sw 0 t I pri 0A t I 0,pri N* pri D 0 sec t -N*( in - pri ) I sec 0A I 0,sec t T on T off T on T off 7

8 Why duty cycles of 40-60% should be chosen I pri 0A t S 1 sw I pri L pri L sec D 1 D I sec C sec sec I 0,pri in C in S 2 GND iso I sec 0A I 0,sec t C pri pri T on T off GND t on D = t on + t off I pri t on = I sec t off N I pri = I sec N 1 D D Too low or too high duty cycles lead to short energy charge or energy transfer times. => High peak currents on primary or secondary side => Transformer needs high saturation current rating I pri 10 8 N=1 I sec ,2 0,4 0,6 0,8 1 D 8

9 Effects of Leakage Inductance Lleak S 1 L pri L sec D 1 C sec sec in C in S 2 GND C pri pri GND iso Example 1: Output voltage over duty factor for different leakage inductance Lower leakage inductance Higher peak currents Higher voltage drop across D 1 N = 1 Higher leakage inductance High currents increase effect of already high leakage inductance Bad regulation Robert Kollman, 9

Effects of Leakage Inductance Example 2: Peak currents for increasing leakage inductance High leakage inductance leads to too slow system Example 3: oltage drop across diode

10 Effects of Leakage Inductance Example 2: Peak currents for increasing leakage inductance High leakage inductance leads to too slow system Example 3: oltage drop across diode for increasing forward current Robert Kollman, Fig. 2 10

11 Resources TI Information Selective Disclosure 11

LM5017 Fly-Buck: Top Industrial Applications Factory Automation PLCs and Motor Drives Smart Grid E-meters & Solar Inverters Other Industrial Power Supplies & E-bikes Bias

controller bias (UCD3k) ebikes: system bias supply PMP7993.1: ±5 & ±15 outputs PMP10535.

E-meter PMP4394: 1W isolated SIP module PMP8581: 48in, synchronous buck power supply in TO-220 footprint Further TI Designs Ultra-Small 1W, 12-36 Iso Power Supply for

12 LM5017 Fly-Buck: Top Industrial Applications Factory Automation PLCs and Motor Drives Smart Grid E-meters & Solar Inverters Other Industrial Power Supplies & E-bikes Bias power from main bus +/- bias voltage rails Analog/digital I/O isolation Bias power for RS485 Bias power for PLC/Relay Inverter system bias supply Power Modules: Digital PWM controller bias (UCD3k) ebikes: system bias supply PMP7993.1: ±5 & ±15 outputs PMP : ±5 & ±12, low profile TIDA-00174: IGBT driver bias for AC motor drive PMP9461: Microinverter Gate Drive and System Bias PMP9310: Non-isolated offline power supply for E-meter PMP4394: 1W isolated SIP module PMP8581: 48in, synchronous buck power supply in TO-220 footprint Further TI Designs Ultra-Small 1W, Iso Power Supply for Analog Prog Logic Controller Modules Reference Design (TIDA-00237) 1W Isolated Power Supply with Planar Transformer Reference Design (TIDA-00688) Small Footprint Isolated Analog DC/DC Converter Reference Design (TIDA-00689) TI Information Selective Disclosure 12 12

LM5160A Fly-Buck Application-based TI Designs Industrial PLCs

Camera/IP Phone Application Needs 24 input bus typical 18-32

Reference Design Isolated triple output 5@1A, +/-15@200mA

Design Isolated 8 outputs 15/-8@150mA for 3-phase IGBT bias

multiple outputs Up to 6W total output Reference Design 3

bus Application Needs 48in typical 36-57 in range Isolated or

Design 12W POE solution LM5160+TPS2378 PMP10532 PMP10531

13 LM5160A Fly-Buck Application-based TI Designs Industrial PLCs Industrial AC Motor Drive IGBT Bias E/HE Bias POE Powered IP Camera/IP Phone Application Needs 24 input bus typical in range Isolated multiple outputs Up to 15W total output Reference Design Isolated triple output Application Needs 24 input bus typical in range Isolated multiple outputs Up to 15W total output Reference Design Isolated 8 outputs 15/-8@150mA for 3-phase IGBT bias Application Needs 12 battery, 6-16in range Isolated single or multiple outputs Up to 6W total output Reference Design 3 designs: Isolated +15@150mA, -9/150mA, and 5/200mA for CAN bus Application Needs 48in typical in range Isolated or non isolated 12 or 5 output Up to 12W output power Reference Design 12W POE solution LM5160+TPS2378 PMP10532 PMP10531 PMP10588 PMP

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Generating Isolated Supplies for Industrial Applications Using the SiC462 in an Isolated Buck Topology

Generating Isolated Supplies for Industrial Applications Using the SiC462 in an Isolated Buck Topology VISHAY SILICONIX www.vishay.com ICs By Ron Vinsant INTRODUCTION Industrial power applications typically require a high input voltage. Standard voltage rails are 4 V, 36 V, and 48 V. The DC/DC step-down