Mobile QR Code QR CODE : The Transactions of the Korean Institute of Electrical Engineers

  1. (Dept. of Electrical Electronic & Control Engineering, Hankyong National University, Korea)



LED converter, LLC resonant converter, 120Hz ripple current, Feed forward, Compensator

1. ์„œ ๋ก 

LED ์กฐ๋ช…์€ ์ˆ˜๋ช…์ด ๊ธธ๋ฉฐ ๋†’์€ ํšจ์œจ์„ ๋‹ฌ์„ฑํ•  ์ˆ˜ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ๋‹ค์–‘ํ•œ ๋ถ„์•ผ์—์„œ ์‚ฌ์šฉ๋˜๋ฉฐ ์‘์šฉ๋ถ„์•ผ์˜ ๋ฒ”์œ„๊ฐ€ ์ ์ฐจ ๋Š˜์–ด๋‚˜๊ณ  ์žˆ๋‹ค. LED ์กฐ๋ช…์šฉ ๊ตฌ๋™ํšŒ๋กœ๋Š” ๊ณ ์กฐํŒŒ ๋ฐ ์ƒ์šฉ ์ „์› ๊ทœ์ œ๋ฅผ ๋งŒ์กฑํ•˜๊ธฐ ์œ„ํ•˜์—ฌ PFC(Power Factor Correction)์™€ LED ์— ํ๋ฅด๊ฒŒ ๋˜๋Š” ์ „์›์„ ์ œ์–ดํ•  ์ˆ˜ ์žˆ๋Š” DC/DC ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๊ตฌ์„ฑํ•˜๋Š” ๊ฒƒ์ด ์ผ๋ฐ˜์ ์ด๋‹ค. DC/DC ์ปจ๋ฒ„ํ„ฐ๋Š” ์•ˆ์ „๊ทœ๊ฒฉ์„ ๋งŒ์กฑํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์šฉ๋Ÿ‰์— ๋”ฐ๋ผ Flyback ์ปจ๋ฒ„ํ„ฐ์™€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๊ฐ€ ๋งŽ์ด ์‚ฌ์šฉ๋˜๋Š” ์ถ”์„ธ์ด๋‹ค. ์ด์ค‘ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋Š” ๊ณต์ง„ ํšŒ๋กœ๋ฅผ ํ†ตํ•ด ๊ณ ํšจ์œจ ๋ฐ ๋†’์€ ์ „๋ ฅ๋ฐ€๋„๋ฅผ ๋‹ฌ์„ฑํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ์žฅ์ ์œผ๋กœ ์‚ฌ์šฉ์ด ๋Š˜์–ด๋‚˜๊ณ  ์žˆ๋‹ค(1)-(4). ์œ„์™€ ๊ฐ™์ด ์ผ๋ฐ˜์ ์œผ๋กœ ์ „์› ๊ณต๊ธ‰์žฅ์น˜๋ฅผ ๊ตฌ์„ฑํ•  ๊ฒฝ์šฐ PFC ์ปจ๋ฒ„ํ„ฐ์™€ DC/DC ์ปจ๋ฒ„ํ„ฐ๋ฅผ Two-stage ๋กœ ๊ตฌ์„ฑํ•˜๊ฒŒ ๋˜๋Š”๋ฐ ์ด๋•Œ DC link ์ปคํŒจ์‹œํ„ฐ์— ์ƒ์šฉ์ „์›์„ ์ •๋ฅ˜ํ•˜๋Š” ๊ณผ์ •์—์„œ 120Hz ์ „์•• ๋งฅ๋™์ด ๋ฐœ์ƒํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋ ‡๊ฒŒ ๋ฐœ์ƒ๋œ ์ „์•• ๋งฅ๋™์€ DC link ์—๋งŒ ๋จธ๋ฌผ์ง€ ์•Š๊ณ  DC/DC ์ปจ๋ฒ„ํ„ฐ ์ถœ๋ ฅ์—๋„ ์ „๋ฅ˜ ๋งฅ๋™์„ ์•ผ๊ธฐํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋ ‡๊ฒŒ ๋ฐœ์ƒ๋œ ์ถœ๋ ฅ ๋งฅ๋™์€ LED์˜ ์„ฑ๋Šฅ ์ €ํ•˜ ๋ฐ ์ˆ˜๋ช…์„ ๋‹จ์ถ•์‹œํ‚ฌ ์ˆ˜ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ์ด๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์ด ํ•„์š”ํ•˜๋‹ค(5).

๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” 120Hz ๋งฅ๋™ ์ „๋ฅ˜๋ฅผ ๊ฐ–๋Š” LED ์กฐ๋ช…์šฉ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ œ์–ด๊ธฐ๋ฒ•์— ๊ด€ํ•œ ์—ฐ๊ตฌ๋กœ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ œ์–ด๋ฅผ ํ†ตํ•˜์—ฌ ์ตœ์ข…์ถœ๋ ฅ ์ „๋ฅ˜์— ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ์—ฐ๊ตฌํ•œ๋‹ค. ๋งฅ๋™์ „๋ฅ˜ ์ €๊ฐ ๊ธฐ๋ฒ•์€ ๊ธฐ์กด ์ œ์–ด๊ธฐ์— ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ํ†ตํ•˜์—ฌ ๋งฅ๋™์„ ์ €๊ฐํ•˜๋Š” ๋ฐฉ๋ฒ•์ด๋‹ค. ์ด๋Ÿฌํ•œ ๋ฐฉ๋ฒ•์„ ์„ค๋ช…ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋จผ์ € ๊ธฐ์กด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ œ์–ด ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๊ณ  ์ด๋ฅผ ํ†ตํ•˜์—ฌ ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ์„ค๋ช…ํ•œ๋‹ค. ๋˜ํ•œ ๊ธฐ์กด์˜ ๋งฅ๋™์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๊ธฐ๋ฒ•๊ณผ ๋น„๊ตํ•˜์—ฌ ๋ณธ ๋…ผ๋ฌธ์—์„œ ์ œ์•ˆํ•˜๋Š” ์ œ์–ด๊ธฐ๋ฒ•์˜ ํšจ๊ณผ ๋ฐ ํŠน์ง•์„ ํ™•์ธํ•˜๊ฒŒ ๋œ๋‹ค. ์ œ์•ˆ๋œ ์ œ์–ด๊ธฐ๋ฒ•์˜ ๋™์ž‘์€ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ฐ ์‹คํ—˜์„ ํ†ตํ•˜์—ฌ ๊ฒ€์ฆํ•˜๊ฒŒ ๋œ๋‹ค.

2. ๋ณธ ๋ฌธ

2.1 LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ

LED ์ „์›์— ์‚ฌ์šฉ๋˜๋Š” ์ „์›์žฅ์น˜์šฉ ์ปจ๋ฒ„ํ„ฐ๋กœ๋Š” ์ผ๋ฐ˜์ ์œผ๋กœ Flyback ์ปจ๋ฒ„ํ„ฐ์™€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๊ฐ€ ์šฉ๋Ÿ‰์— ๋”ฐ๋ผ ์ ์šฉ๋˜๊ณ  ์žˆ๋Š” ์ถ”์„ธ์ด๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๊ธฐ์ค€์œผ๋กœ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๊ธฐ๋ฒ•์„ ์„ค๋ช…ํ•˜๊ธฐ ๋•Œ๋ฌธ์— ๋จผ์ € LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ํŠน์„ฑ์„ ๋ถ„์„ํ•  ํ•„์š”๊ฐ€ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 1. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ

Fig. 1. LLC resonant converter

../../Resources/kiee/KIEE.2019.68.12.1557/fig1.png

๊ทธ๋ฆผ 1์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๊ธฐ๋ณธ ํšŒ๋กœ์ด๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋Š” ๊ณ ํšจ์œจ ๋ฐ ๋†’์€ ์ „๋ ฅ๋ฐ€๋„๋ฅผ ๋‹ฌ์„ฑํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ๋‹ค์–‘ํ•œ ์žฅ์ ์œผ๋กœ ์ธํ•˜์—ฌ ๋งŽ์€ ๋ถ„์•ผ์— ์‚ฌ์šฉ๋˜๊ณ  ์žˆ๋Š” ํ† ํด๋กœ์ง€ ์ด๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋Š” ์ธ๋•ํ„ด์Šค์™€ ์ปคํŒจ์‹œํ„ด์Šค์˜ ๊ณต์ง„ํŠน์„ฑ์œผ๋กœ ์ธํ•˜์—ฌ ZVS(Zero voltage switching) ์™€ ๊ฐ™์€ ์†Œํ”„ํŠธ ์Šค์œ„์นญ์„ ํ†ตํ•˜์—ฌ ๋†’์€ ํšจ์œจ์„ ๋‹ฌ์„ฑํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ๊ณต์ง„์— ์ ์šฉ๋˜๋Š” ๊ณต์ง„ ์ธ๋•ํ„ด์Šค๋ฅผ ๋ณ„๋„์˜ ์ถ”๊ฐ€ ์—†์ด ๋ณ€์••๊ธฐ ๋ˆ„์„ค์ธ๋•ํ„ด์Šค๋ฅผ ์ ์šฉํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๊ฐ„ํŽธํ•˜๊ฒŒ ๊ตฌ์„ฑ์ด ๊ฐ€๋Šฅํ•˜๋‹ค๋Š” ํŠน์ง•์„ ๊ฐ–๊ฒŒ ๋œ๋‹ค(6)-(7). ๊ทธ๋ฆผ 1 ์˜ ์ œ์–ด ๋ธ”๋ก๋„๋Š” ์ปจ๋ฒ„ํ„ฐ์˜ ์ „๋ฅ˜ ILED๋ฅผ ์ „๋ฅ˜ ์ง€๋ น์น˜ ILED_ref ์™€ ๋น„๊ตํ•˜์—ฌ ์ œ์–ด๊ธฐ๋ฅผ ๋™์ž‘์„ ํ†ตํ•ด PWM์„ ์ƒ์„ฑํ•˜๋Š” ๊ตฌ์กฐ์ด๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ๋ณด์ƒ๊ธฐ๋ฅผ ํ†ตํ•˜์—ฌ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ์„ค๋ช…ํ•˜๊ฒŒ ๋œ๋‹ค.

2.2 LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ํŠน์„ฑ๋ถ„์„

LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋™์ž‘ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๊ธฐ ์œ„ํ•œ ์—ฐ๊ตฌ๋Š” ์ด๋ฏธ ๋งŽ์€ ์„ ํ–‰ ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋˜์–ด ์žˆ๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๋ถ„์„ํ•˜๋Š” ๊ฐ€์žฅ ์ผ๋ฐ˜์ ์ธ ๋ฐฉ๋ฒ•์€ FHA(First harmonic approximation) ๋ฐฉ๋ฒ•์ด๋‹ค. FHA๋ฐฉ๋ฒ•์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๊ณ ์ฐจ์„ฑ๋ถ„์„ ๋ฌด์‹œํ•˜๊ณ  ๊ธฐ๋ณธํŒŒ ์„ฑ๋ถ„๋งŒ์œผ๋กœ ์ปจ๋ฒ„ํ„ฐ์˜ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๋Š” ๋ฐฉ๋ฒ•์ด๋‹ค. ์ด๋Š” ์ง๋ ฌ๊ณต์ง„ ํŠน์„ฑ์„ ์ž˜ ๋ณด์—ฌ์ค€๋‹ค๋Š” ์žฅ์ ์œผ๋กœ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๋Š”๋ฐ ๋„๋ฆฌ ์‚ฌ์šฉ๋˜๊ณ  ์žˆ๋‹ค(8)-(9).

๊ทธ๋ฆผ 2๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋“ฑ๊ฐ€ํšŒ๋กœ๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. FHA ๋ฐฉ๋ฒ•์˜ ๊ณผ์ •์€ ๋จผ์ € (a) ์™€ ๊ฐ™์ด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๊ธฐ๋ณธ ๋“ฑ๊ฐ€ํ™” ํ•œ๋‹ค. ๊ธฐ๋ณธ ๋“ฑ๊ฐ€ํšŒ๋กœ์—๋Š” ๋“ฑ๊ฐ€ ์ž…๋ ฅ์ „์•• Vg, ๋“ฑ๊ฐ€ ์ถœ๋ ฅ์ „๋ฅ˜ ios ๊ทธ๋ฆฌ๊ณ  ๋“ฑ๊ฐ€๋ถ€ํ•˜์ €ํ•ญ Ro'๋กœ ํ‘œํ˜„๋˜๋ฉฐ, ์ด๋•Œ ๋“ฑ๊ฐ€ํšŒ๋กœ์˜ ์ž…๋ ฅ ์ „์••๊ณผ ์ถœ๋ ฅ์ „์••์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๊ณ ์ฐจ ๊ณ ์กฐํŒŒ ์„ฑ๋ถ„์„ ๋ชจ๋‘ ํฌํ•จํ•˜๊ณ  ์žˆ๋‹ค. ์—ฌ๊ธฐ์„œ ๊ทธ๋ฆผ (b) ์™€ ๊ฐ™์ด ๊ณ ์ฐจ ๊ณ ์กฐํŒŒ ์„ฑ๋ถ„์„ ๋ชจ๋‘ ์ œ๊ฑฐํ•˜๊ณ  ๊ธฐ๋ณธํŒŒ ์„ฑ๋ถ„๋งŒ์œผ๋กœ ์ •๋ฆฌ๋œ ๋“ฑ๊ฐ€ํšŒ๋กœ๋ฅผ ๊ตฌ์„ฑํ•˜๋Š” ๊ณผ์ •์„ ํ†ตํ•˜๊ฒŒ ๋œ๋‹ค. ๊ธฐ๋ณธํŒŒ ๋“ฑ๊ฐ€ํšŒ๋กœ๋Š” ๋“ฑ๊ฐ€ํ™”์— ๋”ฐ๋ฅธ ๊ธฐ๋ณธํŒŒ ๋“ฑ๊ฐ€ ์ž…๋ ฅ์ „์•• Vge, ์ถœ๋ ฅ์ „์•• Voe, ์ถœ๋ ฅ์ „๋ฅ˜ ioe ๊ทธ๋ฆฌ๊ณ  ๋ถ€ํ•˜์ €ํ•ญ Re๋กœ ํ‘œํ˜„๋œ๋‹ค. ์ด๋•Œ FHA ๋“ฑ๊ฐ€ํšŒ๋กœ์˜ ๋“ฑ๊ฐ€ ์ž…๋ ฅ์ „์••๊ณผ ์ถœ๋ ฅ์ „์••, ์ถœ๋ ฅ์ „๋ฅ˜๋Š” ํ‘ธ๋ฆฌ์— ๊ธ‰์ˆ˜ ๋ณ€ํ™˜์„ ํ†ตํ•˜์—ฌ ๊ฐ„๋‹จํ•˜๊ฒŒ ๊ธฐ๋ณธํŒŒ ์„ฑ๋ถ„๋งŒ์œผ๋กœ ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๊ฒŒ ๋œ๋‹ค.

(1)
$V_{g e}(t)=\dfrac{2}{\pi}\times V_{dc}\times\sin(2\pi f_{s}t)$

๊ทธ๋ฆผ. 2. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ๋“ฑ๊ฐ€ํšŒ๋กœ (a) ๊ธฐ๋ณธ ๋“ฑ๊ฐ€ํšŒ๋กœ (b) FHA ๋“ฑ๊ฐ€ํšŒ๋กœ

Fig. 2. Equivalent circuit of LLC resonant converter

../../Resources/kiee/KIEE.2019.68.12.1557/fig2.png

(2)
$V_{o e}(t)=\dfrac{4}{\pi}\times n\times V_{o}\times\sin(2\pi f_{s}t)$

(3)
$i_{o e}(t)=\dfrac{\pi}{2}\times\dfrac{1}{n}\times I_{o}\times\sin(2\pi f_{s}t)$

์—ฌ๊ธฐ์„œ n ์€ ๋ณ€์••๊ธฐ ํ„ด ๋น„ ์ด๋‹ค.

์œ„ ์ˆ˜์‹์€ ์ˆœ์„œ๋Œ€๋กœ ๋“ฑ๊ฐ€ ์ž…๋ ฅ์ „์••, ์ถœ๋ ฅ์ „์••, ์ถœ๋ ฅ ์ „๋ฅ˜๋ฅผ ํ‘ธ๋ฆฌ์— ๊ธ‰์ˆ˜ ๋ณ€ํ™˜์„ ํ†ตํ•˜์—ฌ ๊ธฐ๋ณธํŒŒ ์„ฑ๋ถ„๋งŒ์„ ํ‘œํ˜„ํ•œ ๊ฒƒ์ด๋‹ค. ์ด๋ ‡๊ฒŒ ์ •๋ฆฌ๋œ ๋“ฑ๊ฐ€ํšŒ๋กœ๋ฅผ ํ†ตํ•˜์—ฌ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ž…์ถœ๋ ฅ ๊ด€๊ณ„์‹์„ ์ •๋ฆฌํ•  ์ˆ˜ ์žˆ๊ฒŒ ๋œ๋‹ค.

(4)
$M_{g}=\dfrac{V_{oe}}{V_{g e}}=\left |\dfrac{(jw L_{m})||R_{e}}{(jw L_{m})||R_{e}+jw L_{r}+\dfrac{1}{jw C_{r}}}\right |$

์ด๋ ‡๊ฒŒ ๊ณ„์‚ฐ๋œ ์ž…์ถœ๋ ฅ ๊ด€๊ณ„์‹์€ ๋ณ€์ˆ˜๋ฅผ ์ •๋ฆฌํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‹ค์‹œ ํ•œ ๋ฒˆ ์ •๊ทœํ™” ํ•  ์ˆ˜ ์žˆ๋‹ค.

(5)
$M_{g}=\left |\dfrac{L_{n}\times f_{n}^{2}}{[(L_{n}+1)\times f_{n}^{2}-1]+j[(f_{n}^{2}-1)\times f_{n}\times Q_{e}\times L_{n}]}\right |$

์—ฌ๊ธฐ์„œ $Q_{e}=\sqrt{L_{r}/C_{r}}/R_{e}$, $f_{n}=f_{s}/f_{r}$, $L_{n}=L_{m}/L_{r}$ ์ด๋‹ค. ๊ณ„์‚ฐ๋œ ์ด๋“์ˆ˜์‹์€ ์ผ๋ฐ˜์ ์ธ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ ์ˆ˜์‹์ด ๋œ๋‹ค. ์ˆ˜์‹์„ ํ†ตํ•ด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ ๊ณก์„ ์„ ์–ป์„ ์ˆ˜ ์žˆ๊ฒŒ ๋œ๋‹ค.

๊ทธ๋ฆผ 3์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ๊ณก์„  ์ด๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ ๊ณก์„ ์€ ์ •๊ทœํ™” ์ฃผํŒŒ์ˆ˜ fn ์— ๋”ฐ๋ฅธ ์ด๋“์˜ ํฌ๊ธฐ๋กœ ํ‘œํ˜„ํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ ๋ถ€ํ•˜ํŠน์„ฑ Q ์— ๋”ฐ๋ผ ๊ฐ๊ธฐ ๋‹ค๋ฅธ ๊ณก์„ ์„ ๊ทธ๋ฆด ์ˆ˜ ์žˆ๋‹ค. ํŠน์„ฑ ๊ณก์„ ์„ ํ†ตํ•ด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋Š” ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜๋ฅผ ์กฐ์ ˆํ•˜๋Š” ๊ฒƒ์œผ๋กœ ์ด๋“์„ ์กฐ์ ˆํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 3. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ด๋“ํŠน์„ฑ๊ณก์„ 

Fig. 3. Gain characteristics curve of LLC resonant converter

../../Resources/kiee/KIEE.2019.68.12.1557/fig3.png

2.3 120Hz ๋งฅ๋™์ „๋ฅ˜ ์ €๊ฐ๊ธฐ๋ฒ•

๊ธฐ์กด์˜ 120Hz ๋งฅ๋™ ์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๊ธฐ๋ฒ•์œผ๋กœ๋„ ๋‹ค์–‘ํ•œ ๋ฐฉ๋ฒ•์ด ์‚ฌ์šฉ๋  ์ˆ˜ ์žˆ๋‹ค. ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์œผ๋กœ๋Š” ํฌ๊ฒŒ 3๊ฐ€์ง€ ๋ฐฉ๋ฒ•์„ ์˜ˆ๋กœ ๋“ค ์ˆ˜ ์žˆ๋‹ค(5).

์ฒซ ๋ฒˆ์งธ๋Š” DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ์šฉ๋Ÿ‰์„ ํ†ตํ•˜์—ฌ DC ๋งํฌ ์ „์•• ๋งฅ๋™์„ ์ €๊ฐํ•˜๋Š” ๊ฒƒ์œผ๋กœ ์ตœ์ข… ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๋Š” ๋ฐฉ๋ฒ•์ด๋‹ค. ์ •๋ฅ˜๋ฅผ ํ†ตํ•ด ๋ฐœ์ƒํ•˜๋Š” DC ๋งํฌ ์ „์••์˜ ๋งฅ๋™์€ DC ๋ง์ปค ์ปคํŒจ์‹œํ„ฐ์˜ ์šฉ๋Ÿ‰์„ ํ‚ค์šฐ๊ฒŒ ๋˜๋ฉด ๊ฐ„๋‹จํžˆ ์ €๊ฐ๋˜๊ธฐ ๋•Œ๋ฌธ์— ๊ฒฐ๊ตญ ์ตœ์ข… ์ถœ๋ ฅ์ด ๋˜๋Š” ์ „๋ฅ˜ ๋งฅ๋™ ๋˜ํ•œ ์ €๊ฐ๋˜๊ฒŒ ๋œ๋‹ค. ์ด ๋ฐฉ๋ฒ•์€ ์†์‰ฝ๊ฒŒ ๋งฅ๋™์„ ์ €๊ฐํ•  ์ˆ˜ ์žˆ์ง€๋งŒ, ๋น„์šฉ์ฆ๊ฐ€ ๋ฐ ์ „์ฒด ์‹œ์Šคํ…œ์˜ ๋ถ€ํ”ผ ์ฆ๊ฐ€๋กœ ์ด์–ด ์งˆ ์ˆ˜ ์žˆ๋‹ค๋Š” ๋‹จ์ ์ด ์žˆ๋‹ค.

๋‘ ๋ฒˆ์งธ๋Š” DC/DC ์ปจ๋ฒ„ํ„ฐ์˜ ์ œ์–ด๊ธฐ๋กœ ์ถœ๋ ฅ์˜ ๋งฅ๋™์„ ์ค„์ด๋Š” ๋ฐฉ๋ฒ•์ด ์žˆ๋‹ค. ์ด ๋ฐฉ๋ฒ•์€ ๋ณ„๋„์˜ ์ถ”๊ฐ€ ์—†์ด ์ œ์–ด๊ธฐ ์„ค๊ณ„๋งŒ์œผ๋กœ ์ œ์–ด๊ฐ€ ๊ฐ€๋Šฅํ•˜์ง€๋งŒ, ์ผ๋ฐ˜์ ์œผ๋กœ ์†Œ์‹ ํ˜ธ ๋ชจ๋ธ ์ด๋“์ด ์ž‘์€ ๊ฒฝ์šฐ PI ์ œ์–ด๊ธฐ๋งŒ์œผ๋กœ๋Š” 120Hz์˜ ์ด๋“์„ ๋†’์ด๋Š” ๊ฒƒ์— ์–ด๋А ์ •๋„ ํ•œ๊ณ„๊ฐ€ ์กด์žฌํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์–ด๋ ค์›€์ด ์žˆ๋‹ค. ๋˜ ๋‹ค๋ฅธ ๋ฐฉ๋ฒ•์œผ๋กœ๋Š” ๊ธฐ์กด์˜ ์ œ์–ด๊ธฐ์— ์ถ”๊ฐ€์ ์ธ ๋ณด์ƒ๊ธฐ๋ฅผ ์„ค๊ณ„ํ•ด ๋งฅ๋™์„ ์ €๊ฐํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ์ƒ๊ฐํ•ด ๋ณผ ์ˆ˜ ์žˆ๋‹ค. ๋จผ์ € ์‰ฝ๊ฒŒ ์ƒ๊ฐํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐฉ๋ฒ•์€ DC ๋งํฌ ์ „์••์„ DC/DC ์ปจ๋ฒ„ํ„ฐ ์ œ์–ด๊ธฐ์— ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐฉ๋ฒ•์ด๋‹ค. ์ด ๋ฐฉ๋ฒ•์€ ์ „๋ฅ˜ ๋งฅ๋™์˜ ์›์ธ์ด ๋˜๋Š” DC ๋งํฌ ์ „์••์„ ํ†ตํ•˜์—ฌ ์ง์ ‘ ๋ณด์ƒํ•˜๊ธฐ ๋•Œ๋ฌธ์— ๋งฅ๋™ ์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ์— ์ ํ•ฉํ•˜๋‹ค๊ณ  ๋ณผ ์ˆ˜ ์žˆ๋‹ค. ํ•˜์ง€๋งŒ ์ด ๋ฐฉ๋ฒ•์€ DC ๋งํฌ ์ „์••์„ ํ†ตํ•˜์—ฌ ๋งฅ๋™์„ ๋ณด์ƒํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์‹ค์‹œ๊ฐ„์œผ๋กœ ์ด๋ฅผ ์ธก์ •ํ•  ์ˆ˜ ์žˆ๋Š” ํšŒ๋กœ๋ฅผ ๊ฐ–์ถ”์–ด์•ผ ํ•œ๋‹ค๋Š” ํŠน์ง•์„ ๊ฐ–๋Š”๋‹ค. LED ์ „์›๊ณผ ๊ฐ™์€ ์กฐ๊ด‘์ „์›์—๋Š” ์„ผ์„œ๋ฆฌ์Šค ์™€ ๊ฐ™์ด DC ๋งํฌ ์ „์••์˜ ๋ณ„๋„์˜ ์ธก์ •์„ ์‚ฌ์šฉํ•˜์ง€ ์•Š๋Š” ์—ฐ๊ตฌ ๋˜ํ•œ ๋‹ค์–‘ํ•˜๊ฒŒ ์ง„ํ–‰ ๋˜๊ณ  ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ์ƒํ™ฉ์— ๋”ฐ๋ผ์„œ ์ด๋Ÿฌํ•œ ๊ฒฝ์šฐ์—๋Š” ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋ณ„๋„์˜ ์ „์•• ๋งฅ๋™์„ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•œ ํšŒ๋กœ๊ฐ€ ์ถ”๊ฐ€๋˜์–ด์•ผ ํ•œ๋‹ค๋Š” ๋‹จ์ ์„ ๊ฐ€์งˆ ์ˆ˜ ์žˆ๋‹ค(10).

2.4 120Hz ๋งฅ๋™์ „๋ฅ˜ ์ง์ ‘ ๋ณด์ƒ๋ฐฉ๋ฒ•

๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” LED ์šฉ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ 120Hz ๋งฅ๋™์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ถœ๋ ฅ๋‹จ์˜ ๋งฅ๋™์ „๋ฅ˜๋ฅผ ํ†ตํ•ด ์ œ์–ด๊ธฐ์— ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ์„ค๋ช…ํ•œ๋‹ค. ์ด๋ ‡๊ฒŒ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•˜์—ฌ ์ง์ ‘ ๋ณด์ƒํ•  ๊ฒฝ์šฐ ์ „๋ฅ˜ ๋งฅ๋™์„ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ํฌ๊ธฐ๋ฅผ ํ‚ค์šฐ์ง€ ์•Š์•„๋„ ๋˜๋ฉฐ, ์ถ”๊ฐ€์ ์ธ ํšŒ๋กœ ์—†์ด ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ์žฅ์ ์„ ๊ฐ€์งˆ ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ 4์—์„œ๋Š” 120Hz ๋งฅ๋™์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ์ œ์–ด ๊ตฌ์„ฑ๋„๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ์ผ๋ฐ˜์ ์œผ๋กœ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ถœ๋ ฅ์„ ์ œ์–ดํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ถœ๋ ฅ ์ „๋ฅ˜๋ฅผ ํ”ผ๋“œ๋ฐฑ ๋ฐ›์•„ ๋น„๋ก€์ ๋ถ„ ์ œ์–ด๊ธฐ๋ฅผ ํ†ตํ•ด PWM ์ปจํŠธ๋กค์„ ์‹ค์‹œํ•˜๊ฒŒ ๋œ๋‹ค. ์—ฌ๊ธฐ์„œ ์ด๋ฏธ ํ”ผ๋“œ๋ฐฑ์„ ๋ฐ›๊ณ  ์žˆ๋Š” ์ถœ๋ ฅ์ „๋ฅ˜์—์„œ 120Hz ๋งฅ๋™ ์„ฑ๋ถ„๋งŒ์„ ํ•„ํ„ฐ๋ง ํ•œ ํ›„์— ๊ทธ๊ฒƒ์„ ๊ธฐ์กด์˜ ๋น„๋ก€ ์ ๋ถ„ ์ œ์–ด๊ธฐ์— ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ์‚ฌ์šฉํ•˜๊ฒŒ ๋œ๋‹ค.

๊ทธ๋ฆผ 4๋Š” ์ „๋ฅ˜ ๋งฅ๋™ ์ €๊ฐ ์ œ์–ด ๋ณด์ƒ๊ธฐ์˜ ๊ตฌ์„ฑ๋„ ์ด๋‹ค. ์‹ค์‹œ๊ฐ„ ๊ฒ€์ถœ ๋œ LED ์ „๋ฅ˜์—์„œ 120Hz ์„ฑ๋ถ„๋งŒ์„ ๋ณด์ƒํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ํ•˜์ดํŒจ์Šค ํ•„ํ„ฐ๋ฅผ ํ†ตํ•ด ํ•„ํ„ฐ๋ง ํ•˜๊ฒŒ ๋œ๋‹ค. ๊ฒ€์ถœ๋œ ์ถœ๋ ฅ ์ „๋ฅ˜์˜ 120Hz ๋ฆฌํ”Œ ์„ฑ๋ถ„์€ ๊ธฐ์กด์˜ ๋น„๋ก€์ ๋ถ„ ์ œ์–ด๊ธฐ์— ์ „ํ–ฅ ๋ณด์ƒ๋˜๊ฒŒ ๋œ๋‹ค. ์ด๋•Œ ๋ณด์ƒ๊ฒŒ์ธ Kc ๋ฅผ ํ†ตํ•ด ๊ฒŒ์ธ์ด ์กฐ์ ˆ๋œ ํ›„์— ์ œ์–ด๊ธฐ์— ๋ณด์ƒ๋˜๊ฒŒ ๋œ๋‹ค. ๋งฅ๋™ ์ €๊ฐ ์ œ์–ด ๋ณด์ƒ๊ธฐ๋Š” ํ•˜์ดํŒจ์Šค ํ•„ํ„ฐ๋ฅผ ํ†ตํ•ด ์œ„์ƒ์ง€์—ฐ์„ ๊ฐ–๊ธฐ ๋•Œ๋ฌธ์— ๋”œ๋ ˆ์ด D๋ฅผ ํ†ตํ•ด ์ด๋ฅผ ๋ณด์ƒํ•ด์ฃผ๊ฒŒ ๋ฉ๋‹ˆ๋‹ค. ๋”œ๋ ˆ์ด D๋Š” ํ•˜์ดํŒจ์Šค ํ•„ํ„ฐ ๋ฐ ์‹ค์ œ ํ•˜๋“œ์›จ์–ด ๋”œ๋ ˆ์ด๊ฐ€ ์กด์žฌํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์‹œํ–‰์ฐฉ์˜ค ๋ฒ•์„ ํ†ตํ•˜์—ฌ ์ ์ ˆํ•˜๊ฒŒ ์กฐ์ •ํ•ด์ฃผ๊ฒŒ ๋œ๋‹ค.

๊ทธ๋ฆผ. 4. ๋งฅ๋™์ „๋ฅ˜ ์ €๊ฐ ์ œ์–ด ๊ตฌ์„ฑ๋„

Fig. 4. Control diagram for reducing ripple current

../../Resources/kiee/KIEE.2019.68.12.1557/fig4.png

LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๊ฒฝ์šฐ ๊ทธ๋ฆผ 3์„ ํ†ตํ•ด ๋ถ„์„ํ•œ ๋‚ด์šฉ๊ณผ ๊ฐ™์ด ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜๋ฅผ ํ†ตํ•œ ์ด๋“์„ ์ œ์–ดํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์ œ์–ด๊ธฐ์˜ ์ถœ๋ ฅ์€ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜ fs ๊ฐ€ ๋˜๋ฉฐ ์ด๋ฅผ ํ†ตํ•ด PWM ๋™์ž‘ํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋ ‡๊ฒŒ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์— ๊ฒ€์ถœ๋œ ์ถœ๋ ฅ ์ „๋ฅ˜ 120Hz ๋งฅ๋™์„ฑ๋ถ„์„ ๋ณด์ƒํ•˜๊ฒŒ ๋œ๋‹ค๋ฉด ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์— 120Hz ๋งฅ๋™ ์„ฑ๋ถ„์ด ์ถ”๊ฐ€๋˜์–ด ์ตœ์ข…์ ์œผ๋กœ ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์ด ์ €๊ฐ๋˜๊ฒŒ ๋  ๊ฒƒ์ด๋‹ค.

๊ทธ๋ฆผ 5๋Š” ๋งฅ๋™์ €๊ฐ ๋™์ž‘ ํŒŒํ˜•์œผ๋กœ ๋งฅ๋™์ €๊ฐ ๋ณด์ƒ์„ ํ•˜์ง€ ์•Š์•˜์„ ๊ฒฝ์šฐ์™€ ํ–ˆ์„ ๊ฒฝ์šฐ์— DC ๋งํฌ ์ „์••๊ณผ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜ ๊ทธ๋ฆฌ๊ณ  LED ์ „๋ฅ˜๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ๋ณด์ƒ๊ธฐ ์—†์ด ๊ธฐ์กด์˜ ์ œ์–ด๊ธฐ ๋งŒ์„ ์‚ฌ์šฉํ•œ ๊ฒฝ์šฐ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ž…๋ ฅ์ „์•• ์ฆ‰ DC ๋งํฌ ์ „์•• ๋ฆฌํ”Œ์— ์˜ํ•ด ๋ฐœ์ƒ๋˜๋Š” 120Hz ๋งฅ๋™์ด ์ถœ๋ ฅ์ „๋ฅ˜์—๋„ ๋ฐœ์ƒํ•˜๊ฒŒ ๋œ๋‹ค. ์—ฌ๊ธฐ์„œ 120Hz ๋งฅ๋™์„ ๋ณด์ƒํ•˜๊ฒŒ ๋œ๋‹ค๋ฉด, ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์— 120Hz ๋ฆฌํ”Œ์ด ์ „ํ–ฅ ๋ณด์ƒ๋˜๊ธฐ ๋•Œ๋ฌธ์— ์ถœ๋ ฅ ์ „๋ฅ˜ ๋ฆฌํ”Œ์ด ์ €๊ฐ๋  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 5. ๋งฅ๋™ ์ €๊ฐ ๋™์ž‘ ํŒŒํ˜• (a) ๋งฅ๋™ ๋ณด์ƒ ์ „, (b) ๋งฅ๋™ ๋ณด์ƒ ํ›„

Fig. 5. Ripple reduction operation waveform

../../Resources/kiee/KIEE.2019.68.12.1557/fig5.png

ํ•˜์ง€๋งŒ ์ถœ๋ ฅ์ „๋ฅ˜๋ฅผ ํ†ตํ•ด ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์€, ์ „๋ฅ˜ ๋ฆฌํ”Œ์ด ์ €๊ฐ๋œ๋‹ค๋ฉด ์ œ์–ด๊ธฐ์— ๋ณด์ƒ๋˜๋Š” ๊ฐ’ ๋˜ํ•œ ์ž‘์•„์ง€๊ธฐ ๋•Œ๋ฌธ์— ์–ด๋А ์ •๋„ ์ˆ˜์ค€์— ๋„๋‹ฌํ•˜๋ฉด ๋” ์ด์ƒ ๋งฅ๋™์ด ์ €๊ฐ๋˜์ง€ ์•Š์•„ ์™„๋ฒฝํ•˜๊ฒŒ ๋งฅ๋™์„ ์ €๊ฐํ•  ์ˆ˜ ์—†๊ฒŒ ๋œ๋‹ค. ๊ทธ๋ ‡๊ธฐ ๋•Œ๋ฌธ์— ์–ดํ”Œ๋ฆฌ์ผ€์ด์…˜ ์ƒํ™ฉ์— ์•Œ๋งž๊ฒŒ ๋ณด์ƒ๊ฒŒ์ธ Kc๋ฅผ ์„ ์ •ํ•ด์•ผ ํ•œ๋‹ค.

์ „๋ฅ˜ ๋งฅ๋™์„ฑ๋ถ„์˜ ๋ณด์ƒ๊ฒŒ์ธ Kc๋Š” ์ „๋ฅ˜๋‹จ์œ„์˜ ๋ ˆ๋ฒจ์—์„œ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜๋ฅผ ์ œ์–ดํ•˜๊ธฐ ์œ„ํ•œ ํฌ๊ธฐ๋กœ ์Šค์ผ€์ผ์„ ์กฐ์ ˆํ•˜๊ธฐ ์œ„ํ•ด ์‚ฌ์šฉ๋œ๋‹ค. ๊ฒฐ๊ตญ ๋ณด์ƒ๊ฒŒ์ธ Kc๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ด๋“ํŠน์„ฑ์— ๋”ฐ๋ผ ๊ณ ๋ ค๋˜์–ด์•ผ ํ•œ๋‹ค.

๊ทธ๋ฆผ 6์€ ๊ทธ๋ฆผ 3์˜ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ด๋“ ํŠน์„ฑ๊ณก์„  ์ผ๋ถ€ ๋™์ž‘ ๋ฒ”์œ„๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๊ฐ€ ๋™์ž‘ ํ•  ์ˆ˜ ์žˆ๋Š” ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์˜ ๋ฒ”์œ„์—์„œ ์ด๋“์˜ ๋ณ€ํ™”๋Š” ์ฃผํŒŒ์ˆ˜์™€ ์„ ํ˜•์ ์ธ ๊ด€๊ณ„๋ฅผ ๊ฐ–์ง€ ์•Š๋Š”๋‹ค. ๋•Œ๋ฌธ์— ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์— ๋”ฐ๋ฅธ ์ด๋“์˜ ๋ณ€ํ™”๋ฅผ ํ†ตํ•ด ๋ณด์ƒ๊ฒŒ์ธ Kc๋ฅผ ์กฐ์ ˆํ•ด ์ค„ ํ•„์š”๊ฐ€ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 6. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ด๋“ ํŠน์„ฑ๊ณก์„ 

Fig. 6. Gain characteristic curve of LLC resonant converter

../../Resources/kiee/KIEE.2019.68.12.1557/fig6.png

LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“์€ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜๊ฐ€ ์ฆ๊ฐ€ํ•˜๋ฉด ๋‚ฎ์•„์ง€๊ฒŒ ๋˜๋ฉฐ, ์ด์™€ ๋ฐ˜๋Œ€๋กœ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜๊ฐ€ ๊ฐ์†Œํ•˜๊ฒŒ ๋˜๋ฉด ์ด๋“์ด ์ฆ๊ฐ€ํ•˜๋Š” ํŠน์„ฑ์„ ๊ฐ€์ง€๊ณ  ์žˆ๋‹ค. ์ด๋•Œ ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์ด๋“์˜ ๋ณ€ํ™”์œจ์ด ์ผ์ •ํ•˜์ง€ ์•Š๊ณ  ๋ณ€ํ™”ํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋Ÿฌํ•œ ํŠน์„ฑ์„ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•ด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ๊ณก์„ ์˜ ๋ณ€ํ™”์œจ์„ ํ™•์ธํ•  ํ•„์š”๊ฐ€ ์žˆ๋‹ค.

์ด๋“์˜ ๋ณ€ํ™”์œจ์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ๊ณก์„  ์ˆ˜์‹ (5)๋ฅผ ๋ฏธ๋ถ„ํ•˜๋Š” ๊ฒƒ์œผ๋กœ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

(6)
$\dfrac{d}{df}[M_{g}]$ $=\dfrac{d}{df}\left[\dfrac{L_{n}\times f_{n}^{2}}{[(L_{n}+1)\times f_{n}^{2}-1]+j[(f_{n}^{2}-1)\times f_{n}\times Q_{e}\times L_{n}]}\right]$

์œ„ ์ˆ˜์‹์„ ๊ณ„์‚ฐํ•˜๊ฒŒ ๋˜๋ฉด

(7)
$\dfrac{d}{df}[M_{g}]=\dfrac{L_{n}}{j L_{n}Qf_{n}^{2}+(L_{n}+1)f_{n}-j L_{n}Q-1}$ $-\dfrac{L_{n}f_{n}(2j L_{n}Qf_{n}+L_{n}+1)}{(j L_{n}Qf_{n}^{2}+(L_{n}+1)f_{n}-j L_{n}Q-1)^{2}}$

๊ณผ ๊ฐ™์ด ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด ์ˆ˜์‹์„ ์ •๋ฆฌํ•˜๋ฉด ์ตœ์ข…์ ์œผ๋กœ

(8)
$\dfrac{d}{df}[M_{g}]=\dfrac{-L_{n}(L_{n}j Qf_{n}^{2}+L_{n}j Q+1)}{(L_{n}jqf_{n}^{2}+(L_{n}+1)f_{n}-L_{n}jq-1)^{2}}$

๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

์ˆ˜์‹ (8)์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ํŠน์„ฑ ์ˆ˜์‹์˜ ๋ณ€ํ™”์œจ์„ ๊ณ„์‚ฐํ•œ ๊ฐ’์œผ๋กœ ๊ฐ ์ฃผํŒŒ์ˆ˜ ๋™์ž‘์˜์—ญ์— ๋”ฐ๋ฅธ ์ด๋“์˜ ๋ณ€ํ™”์œจ์„ ์˜๋ฏธํ•˜๊ฒŒ ๋œ๋‹ค. ๊ณ„์‚ฐ๋œ ์ˆ˜์‹์„ ํ†ตํ•ด ๊ณก์„ ์„ ๊ทธ๋ ค๋ณด๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์— ๋”ฐ๋ผ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“ ๋ณ€ํ™”์œจ์˜ ์ •๋„๊ฐ€ ์–ด๋–ป๊ฒŒ ๋˜๋Š”์ง€ ํ™•์ธํ•  ์ˆ˜ ์žˆ๊ฒŒ ๋œ๋‹ค.

๊ทธ๋ฆผ 7์€ ์ฃผํŒŒ์ˆ˜์— ๋”ฐ๋ฅธ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ด๋“์˜ ๋ณ€ํ™”์œจ,

๊ทธ๋ฆผ. 7. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ด๋“ ๋ณ€ํ™”๊ณก์„ 

Fig. 7. Gain variation curve of LLC resonant converter

../../Resources/kiee/KIEE.2019.68.12.1557/fig7.png

์ฆ‰ ๊ธฐ์šธ๊ธฐ๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๊ทธ๋ฆผ 6๊ณผ ๊ฐ™์ด LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋Š” ์ฃผํŒŒ์ˆ˜ ์กฐ์ ˆ์— ๋”ฐ๋ผ ๋‚ฎ์€ ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์—์„œ ์ด๋“์˜ ๋ณ€ํ™”๊ฐ€ ๋” ํฌ๋ฉฐ, ๋†’์€ ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์—์„œ ์ด๋“์˜ ๋ณ€ํ™”๊ฐ€ ๋” ์ž‘๋‹ค. ๊ฒฐ๊ตญ ๋ณ€ํ™”์œจ์€ ๋‚ฎ์€ ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์—์„œ ์Œ์œผ๋กœ ๋” ํฐ ๊ฐ’์„ ๊ฐ–์œผ๋ฉฐ, ๋†’์€ ์ฃผํŒŒ์ˆ˜ ์˜์—ญ์—์„œ๋Š” ๋ณ€ํ™”์œจ์ด ์ž‘์•„์ง€๊ฒŒ ๋œ๋‹ค. ๋•Œ๋ฌธ์— ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒ ํ•˜๊ฒŒ ๋  ๊ฒŒ์ธ ๋˜ํ•œ ๋™์ž‘์˜์—ญ์— ๋”ฐ๋ผ ์ ์ ˆํ•œ ๊ฐ’์„ ์„ ์ •ํ•ด์•ผ ํ•œ๋‹ค. ๊ณก์„ ๊ณผ ๊ฐ™์ด ๋‚ฎ์€ ์˜์—ญ์—์„œ๋Š” ์ฃผํŒŒ์ˆ˜์กฐ์ ˆ์— ๋”ฐ๋ผ ์ด๋“์˜ ๋ณ€ํ™”๋Ÿ‰์ด ์ฆ๊ฐ€ํ•  ๊ฒƒ์ด๋ฉฐ ๋†’์€ ์ฃผํŒŒ์ˆ˜์—์„œ๋Š” ์ฃผํŒŒ์ˆ˜ ๋ณ€ํ™”์— ๋”ฐ๋ฅธ ์ด๋“์˜ ๋ณ€ํ™”๊ฐ€ ๋” ์ž‘๊ฒŒ ์ ์šฉ๋  ๊ฒƒ์ด๋‹ค.

2.5 ์‹œ๋ฎฌ๋ ˆ์ด์…˜

์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ฐ ์‹คํ—˜์„ ํ†ตํ•˜์—ฌ 120Hz ๋งฅ๋™ ์ „๋ฅ˜๋ฅผ ๊ฐ–๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์ œ์–ด๊ธฐ๋ฒ•์˜ ๋™์ž‘์„ ํ™•์ธํ•ด ๋ณด์•˜๋‹ค.

ํ‘œ 1์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ํšŒ๋กœ์˜ ํŒŒ๋ผ๋ฏธํ„ฐ ๊ฐ’๊ณผ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ฐ ์‹คํ—˜์‹œ ํ…Œ์ŠคํŠธ ์กฐ๊ฑด์„ ๋ณด์—ฌ์ค€๋‹ค. ์‹ค์ œ ์‹คํ—˜์„ ์œ„ํ•˜์—ฌ LED ์ „์›์žฅ์น˜๋Š” Two-Stage ๊ตฌ์กฐ๋กœ ๊ตฌ์„ฑํ•˜์˜€๋‹ค. PFC ์ปจ๋ฒ„ํ„ฐ๋Š” ์ผ๋ฐ˜์ ์œผ๋กœ ์‚ฌ์šฉํ•  ์ˆ˜ ์žˆ๋Š” ๊ธฐ๋ณธ์ ์ธ Boost ์ปจ๋ฒ„ํ„ฐ๋ฅผ ์‚ฌ์šฉํ•˜์˜€์œผ๋ฉฐ, DC/DC ์ปจ๋ฒ„ํ„ฐ๋กœ๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๊ตฌ์„ฑํ•˜์˜€๋‹ค. ๋จผ์ € ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•˜์—ฌ ๋™์ž‘์„ ํ™•์ธํ•˜์˜€๋‹ค. ์‹œ๋ฎฌ๋ ˆ์ด์…˜์€ PSIM ํ”„๋กœ๊ทธ๋žจ์„ ํ†ตํ•˜์—ฌ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

ํ‘œ 1. ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ฐ ์‹คํ—˜ ์‹œ ํ…Œ์ŠคํŠธ ์กฐ๊ฑด

Table 1. Simulation & Experimental test condition

Parameter

Value

Input Voltage

220V/60Hz

DC link Voltage, VDC

350 V

Switching Frequency, fs

55~100 kHz

Resonant Inductance, Lr

202.42 uH

Magnetizing Inductance, Lm

1.05 mH

Resonant Capacitance, Cr

33 nF

Resonant frequency, fr

61 kHz

LED Module

30 V/0.6 A (x5)

Power

90 W

LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํ…Œ์ŠคํŠธ ์กฐ๊ฑด์€ ์‹คํ—˜์— ์‚ฌ์šฉํ•˜๊ฒŒ ๋  ์‹ค์ œ ํ•˜๋“œ์›จ์–ด ์ŠคํŽ™์„ ํ†ตํ•ด ๊ฒฐ์ •ํ•˜๊ฒŒ ๋˜์—ˆ๋‹ค.

PSIM ํ”„๋กœ๊ทธ๋žจ์„ ํ†ตํ•˜์—ฌ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํšŒ๋กœ๋ฅผ ๊ตฌ์„ฑํ•˜์˜€์Šต๋‹ˆ๋‹ค. ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํšŒ๋กœ๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๋ฅผ ๊ตฌ์„ฑํ•˜์˜€์œผ๋ฉฐ DC ์ž…๋ ฅ ์ „์••์€ 120Hz ๋งฅ๋™์„ ํ‘œํ˜„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ DC ์†Œ์Šค์™€ AC ์†Œ์Šค ์ „์••์„ ์ง๋ ฌ๋กœ ์—ฐ๊ฒฐํ•œ ๊ตฌ์กฐ๋กœ ํ‘œํ˜„ํ•˜์˜€๋‹ค. ๋ถ€ํ•˜๋Š” ์‹คํ—˜์— ์‚ฌ์šฉํ•˜๊ฒŒ ๋  30V LED ๋ถ€ํ•˜๊ฐ€ 5๊ฐœ ์ง๋ ฌ๋กœ ์—ฐ๊ฒฐํ•œ ๊ตฌ์กฐ์ด๊ธฐ ๋•Œ๋ฌธ์— ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ์—์„œ๋Š” 150V LED ๋ถ€ํ•˜๋ฅผ ๊ตฌ์„ฑํ•˜์—ฌ ์‹คํ—˜๊ณผ ์ผ์น˜ํ•˜๋Š” ์กฐ๊ฑด์œผ๋กœ ํ™•์ธํ•˜์˜€๋‹ค.

์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๊ณผ์ •์€ ๊ธฐ์กด์— ์ œ์–ด๊ธฐ๋งŒ์„ ํ†ตํ•ด ๋ฐœ์ƒํ•˜๋Š” 120Hz LED ์ „๋ฅ˜ ๋งฅ๋™์„ ํ™•์ธ ํ•œ ํ›„์— 120Hz ๋งฅ๋™ ์ €๊ฐ๊ธฐ๋ฒ•์ด ๋ณด์ƒ๋œ ํŒŒํ˜•์„ ๋น„๊ตํ•˜๊ฒŒ ๋œ๋‹ค.

๊ทธ๋ฆผ. 8. ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํŒŒํ˜• (a) 120Hz ๋งฅ๋™ ๋ณด์ƒ ์ „ (b) ์ „๋ฅ˜๋ฅผ ํ†ตํ•œ 120Hz ๋ณด์ƒ ํ›„

Fig. 8. Simulation waveform

../../Resources/kiee/KIEE.2019.68.12.1557/fig8-1.png../../Resources/kiee/KIEE.2019.68.12.1557/fig8-2.png

๊ทธ๋ฆผ 8 ์€ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๊ฒฐ๊ณผ ํŒŒํ˜•์ด๋‹ค. LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ 120Hz ์ „๋ฅ˜ ๋งฅ๋™์„ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ž…๋ ฅ ์ „์••์ด ๋˜๋Š” DC ๋งํฌ ์ „์••์„ ์ธก์ •ํ•˜๊ณ , 120Hz ๋งฅ๋™์„ ๊ฒ€์ถœํ•œ ๋ณด์ƒ๊ธฐ ์ถœ๋ ฅ ๊ฐ’, LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ๊ฐ€ ๋™์ž‘ํ•˜๋Š” ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜, ๊ทธ๋ฆฌ๊ณ  ์ถœ๋ ฅ์ „๋ฅ˜ ์ฆ‰ LED ์ „๋ฅ˜๋ฅผ ์ธก์ •ํ•ด ๋ณด์•˜๋‹ค. ๊ทธ๋ฆผ (a) ๋Š” 120Hz ์ „๋ฅ˜ ๋งฅ๋™ ์ €๊ฐ๊ธฐ๋ฒ• ์—†์ด ๊ธฐ์กด์˜ ์ œ์–ด๊ธฐ๋งŒ์œผ๋กœ ๋™์ž‘์‹œํ‚จ ํŒŒํ˜•์ด๋ฉฐ, ๊ทธ๋ฆผ (b) ๋Š” ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™ ์„ฑ๋ถ„์„ ์ธก์ •ํ•ด ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ๋ณด์ƒํ•œ ํŒŒํ˜•์ด๋‹ค. ๊ธฐ์กด์˜ ์ œ์–ด๊ธฐ๋งŒ์œผ๋กœ ๋™์ž‘ํ•œ ๊ฒฝ์šฐ ์ถœ๋ ฅ๋‹จ์— ๋ฐœ์ƒํ•˜๋Š” 120Hz ๋งฅ๋™์„ ๊ฒ€์ถœํ•˜์ง€ ์•Š์•˜๊ธฐ ๋•Œ๋ฌธ์— ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์— ๋ณด์ƒ๋˜์ง€ ์•Š์•„ ์ž…๋ ฅ ์ „์•• ๋งฅ๋™์— ์˜ํ•ด ์ถœ๋ ฅ์—๋„ ์ „๋ฅ˜ ๋งฅ๋™์ด ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ๋งฅ๋™ ์ €๊ฐ๊ธฐ๋ฒ•์„ ์ ์šฉ ํ•  ๊ฒฝ์šฐ ์ถœ๋ ฅ๋‹จ์— ๋ฐœ์ƒ๋˜๋Š” ๋งฅ๋™์„ ๊ฒ€์ถœํ•ด ์Šค์œ„์นญ ์ฃผํŒŒ์ˆ˜์— ๋ณด์ƒ๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์— ์ž…๋ ฅ ์ „์•• ๋งฅ๋™์ด ์กด์žฌํ•˜๋”๋ผ๋„ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์ด ํฌ๊ฒŒ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

๊ทธ๋ฆผ 9๋Š” ์ „๋ฅ˜ ์ง€๋ น์น˜๋ฅผ ๋ณ€๊ฒฝํ•˜๋Š” ๊ณผ๋„์ƒํƒœ์—์„œ์˜ 120Hz ๋งฅ๋™ ์ €๊ฐ์„ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์ด๋‹ค. ์ „๋ฅ˜๋Š” 0.4A์—์„œ 0.8A๋กœ ์ง€๋ น์น˜๋ฅผ ๋ณ€๊ฒฝํ•˜๋ฉฐ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์ด ์‹ค์‹œ๋˜์—ˆ๋‹ค. ๊ธฐ๋ณธ์ ์œผ๋กœ ์ „๋ฅ˜ ์ง€๋ น์น˜์— ๋”ฐ๋ผ ๊ฐ๊ธฐ ๋‹ค๋ฅธ ๋ณด์ƒ ๊ฒŒ์ธ์„ ๊ฐ€์ง€๊ฒŒ ๋˜๊ธฐ ๋•Œ๋ฌธ์— ์ด์ „ ๋ณด์ƒ๊ธฐ๊ฐ€ ๊ทธ๋Œ€๋กœ ์ ์šฉ๋œ ์ƒํƒœ์—์„œ ์ง€๋ น์น˜๊ฐ€ ๋ณ€๊ฒฝ๋  ๊ฒฝ์šฐ ์›ํ•˜๋Š” ์ถœ๋ ฅ์„ ์ž˜ ์ถ”์ข…ํ•˜์ง€ ๋ชปํ•˜๊ฒŒ ๋˜๋Š” ๋ฌธ์ œ๊ฐ€ ๋ฐœ์ƒํ•  ์ˆ˜ ์žˆ๋‹ค. ์ด์— ์ œ์–ด๊ธฐ๊ฐ€ ์•ˆ์ •์ ์ธ ๊ตฌ๊ฐ„์— ๋„๋‹ฌํ•  ๊ฒฝ์šฐ ๊ฐ ์ง€๋ น์น˜์— ๋งž๋Š” ๋ณด์ƒ ๊ฒŒ์ธ์ด ์ ์šฉ๋˜๋„๋ก ๊ตฌ์„ฑํ•˜์˜€์œผ๋ฉฐ 120Hz ๋งฅ๋™์ด ์ž˜ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 9. ๊ณผ๋„์ƒํƒœ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํŒŒํ˜•

Fig. 9. Transient simulation waveform

../../Resources/kiee/KIEE.2019.68.12.1557/fig9.png

2.6 ์‹คํ—˜

๋‹ค์Œ์€ ์‹คํ—˜์„ ํ†ตํ•œ 120Hz ์ „๋ฅ˜ ๋งฅ๋™์„ ๊ฐ–๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋™์ž‘์„ ํ™•์ธํ•ด ๋ณด์•˜๋‹ค. ์‹ค์ œ ํ•˜๋“œ์›จ์–ด ๊ตฌ์„ฑ์„ ํ†ตํ•˜์—ฌ ์‹คํ—˜์„ ์ง„ํ–‰ํ•˜์˜€๋‹ค.

ํ…Œ์ŠคํŠธ ์กฐ๊ฑด์€ ํ‘œ 1๊ณผ ๊ฐ™์€ ์กฐ๊ฑด์„ ํ†ตํ•˜์—ฌ ํ•˜๋“œ์›จ์–ด๊ฐ€ ๊ตฌ์„ฑ๋˜์—ˆ๋‹ค. ์‹œ๋ฎฌ๋ ˆ์ด์…˜๊ณผ ๋™์ผํ•˜๊ฒŒ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ ์ „์••์€ 350V ๋กœ ์ œ์–ด๋˜๋ฉฐ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ํ•˜๋“œ์›จ์–ด ์ŠคํŽ™์€ ์‹œ๋ฎฌ๋ ˆ์ด์…˜๊ณผ ๋™์ผํ•˜๋‹ค. ๋˜ํ•œ ๋ถ€ํ•˜๊ฐ€ ๋˜๋Š” LED ๋ชจ๋“ˆ์€ 30V 0.6A ์ŠคํŽ™์— ๋ชจ๋“ˆ 5๊ฐœ๋ฅผ ์ง๋ ฌ ์—ฐ๊ฒฐํ•ด ์‚ฌ์šฉํ•˜์˜€๋‹ค.

๊ทธ๋ฆผ 10์€ ์‹คํ—˜ ํšŒ๋กœ๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ํ‘œ 1 ์™€ ๊ฐ™์€ ์ŠคํŽ™์˜ ํ•˜๋“œ์›จ์–ด๊ฐ€ ๊ตฌ์„ฑ๋˜์—ˆ์œผ๋ฉฐ ์ปจํŠธ๋กค๋Ÿฌ๋Š” DSP 28335 ๋ฅผ ์‚ฌ์šฉํ•œ ๋””์ง€ํ„ธ์ œ์–ด๊ธฐ๋กœ ๊ตฌ์„ฑ๋˜์—ˆ๋‹ค.

๊ทธ๋ฆผ 11๋Š” 120Hz ๋งฅ๋™์ „๋ฅ˜๋ฅผ ๊ฐ–๋Š” LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์‹คํ—˜ ํŒŒํ˜•์ด๋‹ค. ์‹คํ—˜ํŒŒํ˜•์€ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ž…๋ ฅ์ธ DC ๋งํฌ ์ „์•• ํŒŒํ˜• ๋ฐ ์ถœ๋ ฅ LED ์ „๋ฅ˜๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ์‹คํ—˜์€ ํฌ๊ฒŒ 4๊ฐ€์ง€ ๋กœ ์ง„ํ–‰ํ•˜์˜€๋‹ค. ๋จผ์ € ๊ทธ๋ฆผ (a) ๋Š” ๊ธฐ์กด์˜ PI ์ œ์–ด๊ธฐ๋งŒ์„ ๋™์ž‘์‹œํ‚จ ํŒŒํ˜•์œผ๋กœ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ์ถœ๋ ฅ ์ „๋ฅ˜๋Š” ์ž…๋ ฅ DC ๋งํฌ ์ „์••์˜ ๋งฅ๋™์œผ๋กœ ์ธํ•˜์—ฌ ์ถœ๋ ฅ ์ „๋ฅ˜์—ญ์‹œ 120Hz ๋งฅ๋™์ด ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋‘ ๋ฒˆ์งธ ๊ทธ๋ฆผ (b) ๋Š” (a) ์™€ ๊ฐ™์ด ๊ธฐ์กด์˜ PI ์ œ์–ด๊ธฐ๋งŒ์„ ๋™์ž‘์‹œํ‚จ ํŒŒํ˜•์ด์ง€๋งŒ ์ž…๋ ฅ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ๋ฅผ 50uF์—์„œ 200uF์œผ๋กœ ์šฉ๋Ÿ‰์„ ์ฆ๊ฐ€์‹œํ‚จ ํŒŒํ˜•์ด๋‹ค. DC ๋งํฌ ๋งฅ๋™์ด ์ €๊ฐ๋˜๋ฉด์„œ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™ ๋˜ํ•œ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๊ทธ๋ฆผ (c) ๋Š” ๊ธฐ์กด ์ œ์–ด๊ธฐ์— DC ๋งํฌ ์ „์•• ๋งฅ๋™์„ ๊ฒ€์ถœํ•ด ๋ณด์ƒ๊ธฐ๋ฅผ ์‚ฌ์šฉํ•œ ํŒŒํ˜•์ด๋‹ค. DC ๋งํฌ ๋งฅ๋™์€ ๋‚จ์•„์žˆ์ง€๋งŒ ์ œ์–ด๊ธฐ ๋™์ž‘์„ ํ†ตํ•œ ๋ณด์ƒ์œผ๋กœ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋ฆฌํ”Œ์ด ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ๊ทธ๋ฆผ (d) ๋Š” ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์„ ๊ฒ€์ถœํ•ด ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ์‹คํ—˜ํ•œ ํŒŒํ˜•์ด๋‹ค. ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ ์ „์••์— ๋งฅ๋™์ด ์กด์žฌํ•˜์ง€๋งŒ ์ถœ๋ ฅ์ „๋ฅ˜ ๋ฆฌํ”Œ์ด ์—ญ์‹œ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 10. ์‹คํ—˜ ํšŒ๋กœ

Fig. 10. Experiment circuit

../../Resources/kiee/KIEE.2019.68.12.1557/fig10.png

๊ทธ๋ฆผ. 11. ์‹คํ—˜ ํŒŒํ˜• (a) ๊ธฐ์กด์˜ PI์ œ์–ด๊ธฐ ๋™์ž‘ํŒŒํ˜•(C:50uF), (b) ๊ธฐ์กด์˜ PI์ œ์–ด๊ธฐ ๋™์ž‘ํŒŒํ˜•(C:200uF), (c) ์ „์••๋งฅ๋™์„ ํ†ตํ•œ ๋ณด์ƒํŒŒํ˜•(C:50uF), (d) ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•œ ๋ณด์ƒํŒŒํ˜•(C:50uF)

Fig. 11. Experiment waveform

../../Resources/kiee/KIEE.2019.68.12.1557/fig11-1.png../../Resources/kiee/KIEE.2019.68.12.1557/fig11-2.png

๊ทธ๋ฆผ 12๋Š” ๊ทธ๋ฆผ 11 ์˜ ๋งฅ๋™์ „๋ฅ˜ ๋ณด์ƒ ์‹คํ—˜ํŒŒํ˜•์„ ๋น„๊ตํ•˜๊ธฐ์œ„ํ•ด ๋ณด์ƒ๊ธฐ๋ฅผ ์ ์šฉํ•˜์ง€ ์•Š์€ ์ƒํƒœ์—์„œ ์ถœ๋ ฅ ์ „๋ฅ˜๋งฅ๋™์„ ํ†ตํ•œ ๋ณด์ƒ๊ธฐ๋ฅผ ์ ์šฉํ•œ ํ›„์˜ ๋ณ€ํ™”๋ฅผ ์ธก์ •ํ•œ ํŒŒํ˜•์ด๋‹ค. ํŒŒํ˜•์€ ๋งˆ์ฐฌ๊ฐ€์ง€๋กœ DC ๋งํฌ ์ž…๋ ฅ ์ „์••, ์ถœ๋ ฅ LED ์ „๋ฅ˜๋ฅผ ์ธก์ •ํ•˜์˜€๋‹ค. ๋จผ์ € ๊ธฐ์กด์˜ PI ์ œ์–ด๊ธฐ๋งŒ์œผ๋กœ ๋™์ž‘ํ•  ๊ฒฝ์šฐ 120Hz ์ „๋ฅ˜ ๋งฅ๋™์ด ํฌ๊ฒŒ ๋ฐœ์ƒํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ์—ฌ๊ธฐ์„œ ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•œ ๋ณด์ƒ๋ฐฉ๋ฒ•์„ ์ ์šฉํ•œ ๊ฒฝ์šฐ ์ถœ๋ ฅ ์ „๋ฅ˜ ๋งฅ๋™์ด ๋ˆˆ์— ๋„๊ฒŒ ํฌ๊ฒŒ ๊ฐ์†Œํ•˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ. 12. 120Hz ๋งฅ๋™์ „๋ฅ˜ ๋ณด์ƒ์‹คํ—˜ ํŒŒํ˜•

Fig. 12. 120Hz ripple reduction experiment waveform

../../Resources/kiee/KIEE.2019.68.12.1557/fig12.png

ํ‘œ 2์€ 120Hz ๋งฅ๋™์ „๋ฅ˜ ๋ณด์ƒ ์‹คํ—˜ ๊ฒฐ๊ณผํ‘œ์ด๋‹ค. ๋ณด์ƒ๋ฐฉ๋ฒ•์„ ์ ์šฉํ•˜์ง€ ์•Š์€ ๋ฐฉ๋ฒ•๋ถ€ํ„ฐ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ์šฉ๋Ÿ‰์„ ํ†ตํ•ด ์ €๊ฐํ•˜๋Š” ๋ฐฉ๋ฒ•, DC ๋งํฌ ์ „์••๋งฅ๋™์„ ํ†ตํ•ด ์ œ์–ด๊ธฐ๋ฅผ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ• ๊ทธ๋ฆฌ๊ณ  ์ถœ๋ ฅ ์ „๋ฅ˜๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ• ๊ฐ๊ฐ์˜ ๋งฅ๋™๋ฅ ์„ ๋ณด์—ฌ์ค€๋‹ค.

ํ‘œ 2. ์‹คํ—˜ ๊ฒฐ๊ณผ

Table 2. Experiment result

DC Link Capacitance, Cdc

LED Current Ripple Rate

๊ธฐ๋ณธ PI ์ œ์–ด๊ธฐ

50 uF

14.4 %

๊ธฐ๋ณธ PI ์ œ์–ด๊ธฐ

200 uF

7.1 %

Vdc ๋ฅผ ํ†ตํ•œ ๋ณด์ƒ๊ธฐ

50 uF

4.8 %

ILED ๋ฅผ ํ†ตํ•œ ๋ณด์ƒ๊ธฐ

50 uF

6.5 %

์‹คํ—˜๊ฒฐ๊ณผ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ํฌ๊ธฐ๋ฅผ 4 ๋ฐฐ๋กœ ๋Š˜๋ฆด ๊ฒฝ์šฐ ๊ธฐ์กด์— ๋ฐœ์ƒํ•˜๋Š” 120Hz LED ์ „๋ฅ˜ ๋งฅ๋™์„ ๊ธฐ์ค€์œผ๋กœ ๋งฅ๋™๋ฅ ์„ ์ ˆ๋ฐ˜์ •๋„ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋˜ํ•œ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์ด ๊ฐ€์žฅ ํฐ ๋งฅ๋™ ์ €๊ฐ๋ฅ ์„ ๋ณด์˜€์œผ๋ฉฐ ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์€ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ์ „์•• ๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•๊ณผ ๋น„์Šทํ•œ ์ €๊ฐ๋ฅ ์„ ๋ณด์˜€๋‹ค.

DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ์šฉ๋Ÿ‰์„ ๋” ์ฆ๊ฐ€ ์‹œํ‚จ๋‹ค๋ฉด ๋งฅ๋™์ด ๋” ์ €๊ฐ๋  ์ˆ˜ ์žˆ์ง€๋งŒ ๊ทธ๋งŒํผ ์‹œ์Šคํ…œ์˜ ๋ถ€ํ”ผ์ฆ๊ฐ€ ๋ฐ ๋น„์šฉ์ฆ๊ฐ€์˜ ๋ถ€๋‹ด์„ ๊ฐ–๊ฒŒ ๋œ๋‹ค. ๋˜ํ•œ ์œ„์™€ ๊ฐ™์€ ์กฐ๊ฑด์—์„œ DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒํ•  ๊ฒฝ์šฐ ๊ฐ€์žฅ ์ข‹์€ ๊ฒฐ๊ณผ๋ฅผ ์–ป์„ ์ˆ˜ ์žˆ์—ˆ์ง€๋งŒ ์•ž์—์„œ ์„œ์ˆ ํ•œ ๊ฒƒ๊ณผ ๊ฐ™์ด DC ๋งํฌ ์ „์••์„ ์ธก์ •ํ•ด LED ์ „๋ฅ˜๋ฅผ ์ œ์–ดํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์‹ค์‹œ๊ฐ„์œผ๋กœ ์ „์••์„ ์ธก์ •ํ•˜๊ธฐ ์œ„ํ•œ ์ถ”๊ฐ€ ๊ฒ€์ถœ ํšŒ๋กœ๋ฅผ ํ•„์š”๋กœ ํ•˜๊ฒŒ ๋œ๋‹ค. ๋งˆ์ง€๋ง‰์œผ๋กœ ๋ณธ ๋…ผ๋ฌธ์—์„œ ์„ค๋ช…ํ•˜๊ณ  ์žˆ๋Š” ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์€ ์ถœ๋ ฅ LED ์ „๋ฅ˜๋ฅผ ์ œ์–ดํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ์ด๋ฏธ ๊ฒ€์ถœํ•˜๊ณ  ์žˆ๋Š” ์„ฑ๋ถ„์—์„œ ๋งฅ๋™์„ฑ๋ถ„์„ ์ด์šฉํ•˜๊ธฐ ๋•Œ๋ฌธ์— ์ถ”๊ฐ€์ ์ธ ๊ฒ€์ถœํšŒ๋กœ๋ฅผ ํ•„์š”๋กœ ํ•˜์ง€ ์•Š๋Š”๋‹ค. ๋˜ํ•œ ๋ณด์ƒ๋ฐฉ๋ฒ•๋“ค ์ค‘ ๊ฐ€์žฅ ๋งฅ๋™ ์ €๊ฐ๋ฅ ์ด ์ข‹๋‹ค๊ณ  ๋ณผ ์ˆ˜ ๋Š” ์—†์ง€๋งŒ DC ๋งํฌ ์ „์•• ๋งฅ๋™์„ ํ†ตํ•ด ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•๊ณผ ๊ฐ™์ด ์šฐ์ˆ˜ํ•œ ์„ฑ๋Šฅ์˜ ๋งฅ๋™ ์ €๊ฐ๋ฅ ์„ ๋ณด์ด๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

๋‹ค์Œ์€ ๋™์ž‘์˜์—ญ์— ๋”ฐ๋ฅธ LED ์ „๋ฅ˜์˜ ๋งฅ๋™์ €๊ฐ์„ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•œ ์‹คํ—˜์„ ์‹ค์‹œํ•˜์˜€๋‹ค. ์‹คํ—˜์€ ์ „๋ฅ˜ ๋ ˆ๋ฒจ์„ ๋ณ€๊ฒฝํ•˜๋ฉฐ ๊ฐ ์ „๋ฅ˜ ๋งฅ๋™ํŒŒํ˜•์„ ์ธก์ •ํ•˜๊ณ , ๊ฐ ๋ ˆ๋ฒจ์— ๋งž๊ฒŒ ๋งฅ๋™์ €๊ฐ ๊ธฐ๋ฒ•์˜ ๊ฒŒ์ธ์„ ์„ธํŒ…ํ•˜๋Š” ๋ฐฉ์‹์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ๊ทธ๋ฆผ 13์€ ์ „๋ฅ˜๋ ˆ๋ฒจ์— ๋”ฐ๋ผ ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ์ง์ ‘ ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์— ๋Œ€ํ•œ ์‹คํ—˜ ํŒŒํ˜•์„ ๋ณด์—ฌ์ค€๋‹ค. ๊ทธ๋ฆผ (a)๋Š” ์ „๋ฅ˜ ๋ ˆ๋ฒจ 0.8A ์—์„œ์˜ ๋งฅ๋™์ €๊ฐ ๊ธฐ๋ฒ•์„ ์ ์šฉํ•˜๊ธฐ ์ „๊ณผ ์ €๊ฐ๊ธฐ๋ฒ•์„ ์ ์šฉํ•œ ํ›„์˜ ์‹คํ—˜ํŒŒํ˜•์ด๋ฉฐ ๊ทธ๋ฆผ (b)๋Š” ์ „๋ฅ˜ ๋ ˆ๋ฒจ 0.4A ์—์„œ์˜ ์‹คํ—˜ํŒŒํ˜•์ด๋‹ค. ๊ทธ๋ฆผ (b) ์˜ ๊ฒฝ์šฐ ์ถœ๋ ฅ์ด ์ค„์–ด๋“ค๊ธฐ ๋•Œ๋ฌธ์— DC ๋งํฌ ์ปคํŒจ์‹œํ„ฐ์˜ ์ „์•• ๋งฅ๋™ ๋˜ํ•œ ์ €๊ฐ๋˜์–ด ๋ณด์ด๊ฒŒ ๋œ๋‹ค. ์ „๋ฅ˜ ๋ ˆ๋ฒจ์„ ๋ณ€๊ฒฝํ•ด๋„ ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ์ง์ ‘ ์ €๊ฐํ•˜๋Š” ๋ฐฉ๋ฒ•์œผ๋กœ ์ „๋ฅ˜๋งฅ๋™์ด ํฌ๊ฒŒ ์ €๊ฐ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ๋˜ํ•œ ๊ฐ ์ „๋ฅ˜๋ ˆ๋ฒจ์— ๋”ฐ๋ผ ๋งฅ๋™์„ ๋ณด์ƒํ•˜๊ธฐ ์œ„ํ•œ ๋ณด์ƒ ๊ฒŒ์ธ์„ ํ™•์ธํ•ด ๋ณด์•˜๋‹ค.

๊ทธ๋ฆผ. 13. ์ „๋ฅ˜ ๋ ˆ๋ฒจ์— ๋”ฐ๋ฅธ ์‹คํ—˜ ํŒŒํ˜• (a) 0.8A ๋ ˆ๋ฒจ, (b) 0.4A ๋ ˆ๋ฒจ

Fig. 13. Experiment waveform by current level

../../Resources/kiee/KIEE.2019.68.12.1557/fig13.png

๊ทธ๋ฆผ. 14. ์ „๋ฅ˜ ๋ ˆ๋ฒจ์— ๋”ฐ๋ฅธ ๋ณด์ƒ๊ฒŒ์ธ ๊ทธ๋ž˜ํ”„

Fig. 14. Graph of compensation gains by current level

../../Resources/kiee/KIEE.2019.68.12.1557/fig14.png

๊ทธ๋ฆผ 14๋Š” ์ „๋ฅ˜ ๋ ˆ๋ฒจ์— ๋”ฐ๋ฅธ ๋ณด์ƒ ๊ฒŒ์ธ์„ ๊ทธ๋ž˜ํ”„๋กœ ๋‚˜ํƒ€๋‚ธ ๊ฒƒ์ด๋‹ค. LED ์ „๋ฅ˜ ๋ ˆ๋ฒจ์€ 0.4A์—์„œ 0.8A ๊นŒ์ง€ ํ™•์ธํ•˜์˜€์œผ๋ฉฐ, LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋™์ž‘ ์ฃผํŒŒ์ˆ˜๋Š” ๋†’์€ ์ด๋“์—์„œ ๋‚ฎ์€ ๊ฐ’์„ ๊ฐ–๊ธฐ ๋•Œ๋ฌธ์— ๋ถ„์„์˜ ํŽธ์˜๋ฅผ ์œ„ํ•ด 0.8A๋ถ€ํ„ฐ ๊ทธ๋ž˜ํ”„๋ฅผ ํ‘œ์‹œํ•˜์˜€๋‹ค. ๋ณด์ƒ๊ฒŒ์ธ Kc ๋Š” ์ •๊ฒฉ์ด ๋˜๋Š” 0.6A ์—์„œ์˜ ๋ณด์ƒ ๊ฒŒ์ธ์„ 1 ๋กœ ๊ธฐ์ค€ํ•˜์—ฌ ํ‘œ์ค€ํ™” ํ•˜์˜€๋‹ค. ๊ทธ๋ž˜ํ”„๋Š” 0.6A๋ฅผ ๊ธฐ์ค€์œผ๋กœ ์ด๋“์ด ๋†’์•„์ง€๋ฉด ๋ณด์ƒ ๊ฒŒ์ธ์„ ๋” ๋‚ฎ๊ฒŒ ์„ค์ •ํ•ด ์ฃผ์–ด์•ผ ์ „๋ฅ˜ ๋งฅ๋™์ด ์ ์ ˆํžˆ ๋ณด์ƒ๋˜์—ˆ์œผ๋ฉฐ ๋ฐ˜๋Œ€๋กœ ์ด๋“์„ ๋‚ฎ์ถœ ๊ฒฝ์šฐ ๋ณด์ƒ๊ฒŒ์ธ์„ ๋” ์ถฉ๋ถ„ํžˆ ๋†’์—ฌ์ฃผ์–ด์•ผ LED ์ „๋ฅ˜ ๋งฅ๋™์ด ์ถฉ๋ถ„ํžˆ ๋ณด์ƒ๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ์ด๋Š” ์œ„์—์„œ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋™์ž‘ํŠน์„ฑ์„ ๋ถ„์„ํ•œ ๋‚ด์šฉ์—์„œ ์•Œ ์ˆ˜ ์žˆ๋“ฏ ๋™์ž‘์˜์—ญ์— ๋”ฐ๋ผ ์ฃผํŒŒ์ˆ˜ ๋ณ€ํ™”๊ฐ€ ์ด๋“์„ ๊ฐ€๋ณ€ํ•˜๋Š”๋ฐ ์ฐจ์ด๋ฅผ ๋ณด์ด๊ธฐ ๋•Œ๋ฌธ์— ์ด์— ๋งž๋Š” ๊ฒŒ์ธ์„ ์„ ์ •ํ•ด์•ผํ•œ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค.

3. ๊ฒฐ ๋ก 

๋ณธ ๋…ผ๋ฌธ์€ LED ์กฐ๋ช…์šฉ ์ „์›์žฅ์น˜๋กœ ์ด์šฉ๋˜๋Š” LLC ๊ณต์ง„์ปจ๋ฒ„ํ„ฐ์— ๋ฐœ์ƒํ•˜๋Š” 120Hz ๋งฅ๋™์ „๋ฅ˜๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ์ œ์–ด๊ธฐ๋ฒ•์— ๊ด€ํ•˜์—ฌ ์—ฐ๊ตฌํ•˜์˜€๋‹ค. ๋‹ค์–‘ํ•œ ๋ถ„์•ผ์—์„œ ์‚ฌ์šฉ๋˜๋Š” LED ์กฐ๋ช…์˜ ์ „์›์žฅ์น˜๋Š” ๊ตฌ์กฐ์ƒ ์ •๋ฅ˜๊ณผ์ •์—์„œ ๋ฐœ์ƒํ•˜๋Š” 120Hz DC ๋งํฌ ๋งฅ๋™ ์ „์••์— ์˜ํ•ด LED ์ถœ๋ ฅ ์ „๋ฅ˜์—ญ์‹œ 120Hz ๋งฅ๋™์ด ๋ฐœ์ƒํ•˜๊ฒŒ ๋œ๋‹ค. ์ด๋Ÿฌํ•œ ์ „๋ฅ˜ ํ’ˆ์งˆ ์ €ํ•˜๋Š” LED ์„ฑ๋Šฅ ์ €ํ•˜ ๋ฐ ์ „์ฒด ์‹œ์Šคํ…œ ์„ฑ๋Šฅ์—๋„ ์˜ํ–ฅ์„ ๋ผ์น  ์ˆ˜ ์žˆ๊ธฐ ๋•Œ๋ฌธ์— ์ด๋ฅผ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋…ธ๋ ฅ์„ ํ•„์š”ํ•˜๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ์ œ์–ด๊ธฐ๋ฒ•์„ ํ†ตํ•œ 120Hz ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•˜์—ฌ LLC ๊ณต์ง„ ์ปจ๋ฒ„ํ„ฐ์˜ ๋™์ž‘ ๋ฐ ์ œ์–ด ํŠน์„ฑ์— ๋Œ€ํ•˜์—ฌ ๋ถ„์„ํ•˜์˜€๋‹ค. ๋˜ํ•œ ๊ธฐ์กด์˜ ๋ฐฉ๋ฒ•์„ ํ†ตํ•œ 120Hz ์ „๋ฅ˜ ๋งฅ๋™ ์ €๊ฐ๋ฒ•์„ ์„ค๋ช…ํ•˜์˜€์œผ๋ฉฐ, ๊ธฐ์กด์˜ ์ „๋ฅ˜ ๋งฅ๋™์„ ์ €๊ฐํ•˜๊ธฐ ์œ„ํ•œ ๋ฐฉ๋ฒ•์€ ์‹œ์Šคํ…œ ๋ถ€ํ”ผ ๋ฐ ๋น„์šฉ์ฆ๊ฐ€, ๊ทธ๋ฆฌ๊ณ  ์ถ”๊ฐ€ ๊ฒ€์ถœ ํšŒ๋กœ๋“ฑ์„ ์ถ”๊ฐ€ํ•ด์•ผ ํ•œ๋‹ค๋Š” ๋‹จ์ ์„ ๊ฐ€์ง€๊ณ  ์žˆ๋‹ค๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋Ÿฌํ•œ ๋ฌธ์ œ์˜ ๋Œ€์•ˆ์œผ๋กœ 120Hz ์ถœ๋ ฅ์ „๋ฅ˜ ๋งฅ๋™์„ ํ†ตํ•ด ์ง์ ‘ ์ œ์–ด๊ธฐ์— ๋ณด์ƒํ•˜๋Š” ๋ฐฉ๋ฒ•์— ๋Œ€ํ•˜์—ฌ ์„ค๋ช…ํ•˜์˜€๋‹ค. ์ด๋ ‡๊ฒŒ ๋˜๋ฉด ์ถ”๊ฐ€์ ์ด ํšŒ๋กœ ์—†์ด ์ถœ๋ ฅ์ „๋ฅ˜์˜ ๋งฅ๋™์„ ์ €๊ฐํ•  ์ˆ˜ ์žˆ๋‹ค๋Š” ์žฅ์ ์„ ๊ฐ€์ง€๊ฒŒ ๋œ๋‹ค. ์ด๋Ÿฌํ•œ ๋งฅ๋™ ์ €๊ฐ๊ธฐ๋ฒ•์€ PSIM ํ”„๋กœ๊ทธ๋žจ์œผ๋กœ ํ†ตํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๋ฐ ์‹ค์ œํ•˜๋“œ์›จ์–ด ๊ตฌ์„ฑ์„ ํ†ตํ•œ ์‹คํ—˜์œผ๋กœ ์„ฑ๋Šฅ์„ ํ™•์ธํ•˜์˜€๋‹ค.

Acknowledgements

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (No. NRF-2017R1D1A1B03031532).

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์ €์ž์†Œ๊ฐœ

๊ถŒ๋ฏผ์ค€ (Min-Jun Kwon)
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He received the B.S. and M.S. degrees in electrical engineering from Hankyong National University, Ansung, Korea, in 2015, 2017, res- pectively.

He is currently a Ph.D course student in the School of Electrical, Electronic and Control Engineering at Hankyong National University.

His research interests are in the areas of power converter, PFC, inverter, and electrical drives.

์ด์šฐ์ฒ  (Woo-Cheol Lee)
../../Resources/kiee/KIEE.2019.68.12.1557/au2.png

He received the B.S. and M.S. and Ph.D. degrees in electrical engineering from Hanyang University, Seoul, Korea, in 1987, 1989, 2001, respectively.

From 1988 to 1998, he was with the R&D Institute, Hyosung Industries Company Ltd., as a Senior Researcher, Seoul, Korea. He was a Visiting Professor in the department of Electrical Engineering at Virginia Polytechnic Institute and State University, Virginia, USA from 2007 to 2009.

Since 2002, he has been with Hankyong National University, Ansung, Korea, where he is a Professor with the Department of Electrical, Electronic and Control Engineering.

His research interests are in the areas of power converter, APF, UPS, and electrical drives.