PFC and EMI filtering

Transkript

1 PFC and EMI filtering Alex Snijder Field Application Engineer Wurth Elektronik Nederland B.V. November 2017

2 EMC Standards Power Factor Correction Conducted emissions Radiated emissions 2

3 Overview of standard covering SMPS dbµv/m 100 CISPR11, EN55011 for industrial, medical, scientific applications CISPR13, EN55013 for consumer applications CISPR14, EN55014 for home appliances, power tools, CISPR15, EN55015 for lighting equipment CISPR22, EN55022 for computing applications MHz Frequency (MHz) 1GHz 3

4 Low Frequency Conducted EMC (CISPR15) 62kHz +6dB 4

5 LED Driver 5

6 PFC/ Harmonic standard EN To avoid reactive power on power network, a PFC circuit is needed with most switch mode power solutions It is required by law Used for electrical regulated Loads Switching power supplies Electronic Engine regulation Lighting dimmer Problems of high peak current Peak current of the loads occur at the same time occur nearly at the voltage peak 6

7 EN Classes Class A 3-phase devices White goods All devices which are not mentioned in other Classes Class B Portable Tools Class C Lighting equipment Class D PC PF requirement also for small power Screen TV- Radio equipment with input power of < 600W 7

8 What is PFC and what does a PFC (choke) do? What does PFC mean? PFC means power factor correction PFC choke forms the input current in phase to the mains voltage Why PFC? To avoid reactive power which have to be provided by energy providers Reactive power Active power Source: 8

9 Passive PFC Passive PFC Choke and Cap. (Low-Pass-Filter) Advantage: Cost effective (Component) Passive Disadvantage: Required too much space on PCB Power Factor between 0,7-0,8 typical characteristic on the PCB big toroidal core at the input 9

10 Active PFC Active Active PFC Choke with Bias winding for the IC ( not for all a Bias winding ) Controlled by an IC Advantage: Required less space on PCB Power Factor close to 1 Universal input regulation Better EMI compatibility Disadvantage: Cost intensive 10

11 Different PFC Solutions Input Characteristics of PC Power Supplies with PFC Types ( None, Passive and Active ) Source: 11

12 WE Standard PFC parts RM series Small footprint Good EMC behaviour due to shielded and grounded core Low proximity losses due to litz wire EFD series Flat design Low proximity losses due to litz wire 12

13 Common Mode noise 13 I cm 2 I dm L1 N I cm 2 PE I cm Parasitic capacities e.g.: collector to cooling element 13

14 Differential mode calculation example 14 I dm L1 N PE I = 2A Duty Cycle = 50% F sw = 150Khz ESR = 50mΩ Check ClassB 150Khz : Allowed 66 dbµv = 2mV 2 I Harmonic1 = = 450mA rms Vc = I Harmonic1 ESR = 23mV π 2 V V = C measured 5mV 2 =11, 14

15 Still noisy 15

16 Common mode noise calculation example L1 I cm 2 N I cm 2 PE I cm V = 400V Duty Cycle = 50% F sw = 150Khz C = 50 pf Check ClassB 150Khz : Allowed 66 dbµv = 2mV 2 V V max Harmonic1 = = 180V rms I f C V ma π hamonic1 = 2. π... Harmonic1 = 8, 4 2 V = 25 Ω. I = mv measured cm

17 «Block & Bypass» examples 17

18 Effective frequency range CMB NC 70 WE-CMB MnZn WE-CMB NiZn 14 µh µh 47 µh 100 µh 50 1 mh attenuation [db] mh 10 mh 20 mh 39 mh , frequency [MHz] 18

19 X-Y capacitors 19

20 20