Software solutions to mitigate the EM emission of power modules

Transcription

1 Sofware soluions o miigae he EM emission of power modules Franco Fiori Elecronics and Telecom Dp. (DET), Poliecnico di Torino, Ialy franco.fiori@polio.i

2 Ouline An inroducion o EMI filering in power modules A echnique for cheaing EMI sandards Time delay compensaion echnique Passive and Acive snubbers Quesion ime 11/27/2018 franco.fiori@polio.i 2

3 Differenial Mode (DM) i HS dbua A V LISN i HS db i d i HS A = 2i HS0 DC V LISN Ls f 3 f 1 f 2 f f 1 = 1 πt on = f sw πdc V LISN dbuv f 2 = 1 π r i d f 3 = 2π 1 L S C D i HS T f 3 f 1 f 2 f I HS0 V LISN = 2I HS0 L S f sw T 11/27/2018 on franco.fiori@polio.i 3

4 DM filers i HS V LISN i HS db Ls DM filer Filers are usually bulky and expensive and.. mos of all hey do no perform as expeced 11/27/2018 franco.fiori@polio.i 4

5 Common Mode (CM) v X Trap wave V LISN C p C p 0V i cm i cm 10 pf < C p < 100pF 0V The CM curren becomes dominan in he frequency range 1MHz 100 MHz 11/27/2018 franco.fiori@polio.i 5

6 Common Mode (con d) V X,M = 2V X0 DC V X dbuv In he frequency range f 1 f 2 V X,M V LISN V X db f 1 = f sw πdc f 2 = 1 π r f V X = 2V X0 DC f 1 f = 2V f sw X0 πf f 1 f 2 and being i cm C p dv X d V LISN dbuv we ge V LISN = 4V X0 f sw R LISN C p f f 1 f 2 11/27/2018 franco.fiori@polio.i 6

7 CM Filers Trap wave L c clear V LISN V X V LISN db wih C cm only L c C cm C cm Even wih EMI filers, emissions can exceed he limis in some frequency bands Tha s frusraing for he designer!!! wih C cm and L c 11/27/2018 franco.fiori@polio.i 7

8 Spread Specrum Modulaion (SSM) IN f sw + f sw V m Modulaing signal HS f sw f sw - f sw EMI filers gae drivers X OUT T V pwm LS V pwm Modulaed PWM V pwm C C RC2 T sw + _ v V osc _ + R C1 V ref T sw f m = 1 T frequency of he modulaing sgn V osc v m f = Δf sw 11/27/2018 franco.fiori@polio.i 8 f m Modulaion index

9 The energy of each harmonic is spread over a band ha increases wih he harmonic order (n) ΔV peak,db B n = 2nΔf sw The frequency bands of he harmonics overlap when nδf sw + n + 1 Δf sw f sw B is known as he Carson s band B B n n ovlp = ceil f sw 2Δf sw 1 2 f m ΔV peak,db = 20 log n Δf sw f m for n < n ovlp f ΔV peak,db = 20 log n ovlp Δf sw f m for n > n ovlp f Lin scale sw 11/27/2018 franco.fiori@polio.i 9

10 EMI receiver block diagram From he sandard we know RBW, herefore we choose f m fm < RBW: he EMI receiver is no able o disinguish individual sideband harmonics, so, several harmonics excie he receiver simulaneously fm > RBW: he EMI receiver is able o measure each individual sideband harmonic waning o keep measured peaks a he minimum, we choose fm > RBW 11/27/2018 franco.fiori@polio.i 10

11 On balance - Waning o chea he EMI receiver f m mus be greaer han RBW - An excessive incremen of Δf sw can affec he conrol circui especially when muliple loops are implemened 10 < Δf sw f m < 20 is a good compromise o address boh issues - The specral overlap, which akes place for n > n ovlp limis is effeciveness a high frequency - The mehod is no effecive or even dangerous in resonan or quasi resonan DC-DC converers 11/27/2018 franco.fiori@polio.i 11

12 A real reducion of he Common Mode curren LISN 50 Y C D X 50 i cm 11/27/2018 franco.fiori@polio.i 12

13 v X v X v Y τ d v Y no aligned usually i cm,x i cm,x i cm,y i cm,y i cm i cm 11/27/2018 franco.fiori@polio.i 13

14 Time delay compensaion τ d i cm i cm i cm 11/27/2018 franco.fiori@polio.i 14

15 Time delay compensaion (con d) cables DM EMI filer inverer cables LISN MOTOR U 50 V gae drivers W 50 11/27/2018 franco.fiori@polio.i 15

16 Time delay compensaion (con d) Acually, he rising and he falling edges differ one anoher, hus he emission canno be zeroed even wih τ d close o zero. M. Peroi, F. Fiori, Invesigaing he EMI Miigaion in Power Inverers Using Delay Compensaion IEEE Transacion on Power Elecronics, /27/2018 franco.fiori@polio.i 16

17 Weaknesses of he proposed approach 11/27/

18 IN Snubbers L p before X OUT C x,p C sn R sn afer GND - Incremen of he power dissipaion - C sn mus be an high volage capacior 11/27/2018 franco.fiori@polio.i 18

19 Acive snubbers IN L p Gae driver R on R on OUT C x,p Insead of damping he L p C x,p resonance wih addiional componens GND we are aiming o do ha wih he HS swich Research projec carried ou wihin he Power Elecronics Innovaion Cener (PEIC) 11/27/2018 franco.fiori@polio.i 19

20 Quesion ime! 11/27/