電力電子元件簡介 Introduction to Power Electronic Devices C. M. Liaw Department of Electrical Engineering National Tsing Hua University Hsinchu, Taiwan, ROC. 兩段式電熱控制 ( 應用 Power diode) 無段式電熱控制 ( 應用 SCR) AC source Power diode AC source SCR P Load Load Firing circuit Diode: Uncontrolled turn-on and turn-off 不可控制交流輸出電壓故控制性能較差 SCR: Controlled turn-on and uncontrolled turn-off 可控制交流輸出電壓故控制性能較佳 Page 1
常用功率半導體元件之額定 ( 表二 ) Voltage/current ratings Switching frequency (speed) Switching time On-state resistance (or on-state voltage/current) 功率半導體元件 (A) 閘流體 (Thyristor) 或矽控整流器 (Silicon Controlled Rectifier, SCR) : Controlled turn-on, uncontrolled turn-off (B) 雙向閘流體 (Bidirectional Thyristor 或 TRIAC) (C) TO (ate Turn-off Thysistor) (D) 基體閘換向閘流體 (Integrated ate-commutated Thyristor, ICT): It is introduced by ABB in 1997. It is a high-voltage, hard-driven, asymmetrical-blocking TO with unity gain. The gate drive circuit is built-in on the device module. (E) 功率電晶體 (Power BJT) : Current control device (F) IBT (Insulated ate Bipolar Transistor): -Combines the conduction characteristic of BJT and the control characteristic of the MOSFET () MOS 控制閘流體 (MOS -controlled Thyristor, MCT): -Combines the load characteristic of the thyristorand the control characteristic of the MOSFET - Low on-state voltage (H) 功率金氧半電晶體 (Power MOSFET) : Voltage control device (I) 其它 耐壓耐流 操作速度 Page 2
功率半導體元件之控制特性 (1) Uncontrolled turn-on and off: (diode) (2) Controlled turn-on and uncontrolled turn-off: (SCR) (3) Controlled turn-on and off (Controllable switches): (TO, ICT, MCT, BJT, IBT, MOSFET) (4) Continuous gate signal requirement: (ICT, BJT, IBT, MOSFET) (5) Pulse gate signal requirement: (MCT, SCR, TRIAC, TO) (6) Bipolar voltage-withstanding capability: (SCR) (7) Unipolar voltage-withstanding capability: (TO, ICT, MCT, BJT, IBT, MOSFET) (8) Bidirectional current capability: (TRIAC) (9) Unidirectional current capability: (SCR, TO, ICT, MCT, BJT, IBT, MOSFET, diode) Power Semiconductors Classification of state-of-the-art Power Semiconductors SiC Page 3
常用功率半導體元件之符號及操作特性 功率換流器之典型結構 型式 : Power source (AC, DC) Input filter ( 濾波及 / 或功因控制 ) Command ( 強電 ) Power Converter Switching Control Signal enerator ( 弱電 ) Output filter ( 隔離 驅動 ) Feedback Output source (to load) Loads: Power supplies Motor drives 交流至交流交流至交流換流器 (Cycloconverter) ( 含交流至直流至交流換流器 ) 交流至直流換流器 (Converter): Phase control, integral cycle control 直流至交流換流器 (Inverter): VVVF, VVFF 直流至直流換流器 (Chopper): PWM control, FM control Page 4
如何設計一個電力電子設備? (1) 由機械負載特性選定馬達及換流器之型式 (2) 設計組裝電力電路 : 選定功率半導體元件 組裝換流器及其保護電路 (3) 決定並設計適當之換流器切換控制方式及電路 (4) 設計邏輯決策電路 隔離電路及觸發驅動電路 (5) 設計輸入及輸出濾波電路 ( 功因控制電路 ) (6) 感測元件及其信號放大處理電路之組立 (7) 電力電子系統之動態模式建立 : 推導或由量測估算得之 (8) 閉迴路控制系統之設計及實作 (9) 組裝 ( 注意接地與屏蔽等考量安排設計 ) 常用功率半導體簡介 Power diodes: eneral purpose (for high-power rectification) High speed (for switching application) Schottky(for extra-low voltage rectification) Thyristors Power transistors Page 5
SCR ( 矽控整流器 ) 閘流體 (Thyristor)- 矽控整流器 (Silicon Controlled Rectifier, SCR) : Controlled turn-on, uncontrolled turn-off Construction, symbol, equivalent circuit, triggering control, v-i characteristics: A A A A P P K N P N N N P P N i = i Q1 c1 b2 i c2 b1 Q2 = i K K K Two-transistor model Page 6
SCR 之逆偏 vak > VRB ( VRWM ) Breakdown A i AK 0 i AK K P N P N RB FB RB V RB ( V RWM ) IH i > i > i 1 2 3 V FB ( V BO ) v AK SCR 之順偏 順偏 : i AK A i AK i K K P N P N FB RB FB V RB ( V RWM ) IH i > i > i 1 2 3 V FB ( V BO ) v AK Page 7
Two-transistor model ib ic ib ic (Current is cumulatively amplified) Normally triggered: 當 v > 0 AK 時, 加以適當之 i > 0 S Abnormally triggered: High dv/dt High temperature v AK > V FB i = i A c1 b2 Q1 Q2 i = i c2 b1 K 觸發控制 Turn on: 當 v > 0 時, 加以適當之 i > 0 AK S Turn off: i I H ( Holding current ) AK < 在使用時, 須注意外加之電壓正負峰值不可大於順向崩潰電壓 V FB 及逆向崩潰電壓 V RB i AK V RB ( V RWM ) I H i > i > i 1 2 3 v AK V FB ( V BO ) Page 8
沒有 ate 之 SCR 蕭克萊二極體 (Shockley diode) on 及 off: v V ON, i < I OFF AK FB AK H 符號 : A K Triac (AC Thyristor) A three-terminal, five layer, bilateral semiconductor device. Bidirectional TRIode AC thyristor. TRIAC T 1 T 2 Tab electrically connected to T2 Page 9
Triac 之簡易測試 Power supply TRIAC - - IT48TH T1T2 TRIAC A three-terminal, five layer, bilateral semiconductor device. T 2 T 1 : P N 2 2 P N 1 1 T 2 P N3 2 T T 1 2 : P N 1 2 P N 2 3 N 2 N 1 P 1 N 4 T1 Page 10
TRIAC: 為兩個反並接之 SCR, 可於正負半週觸發導通, 為具 bidirectional current capability 之元件 符號 : 觸發控制 Turn on: Turn off: T 1 ( A ) T 2 ( K ) 當 當 AK v > 0 AK v < 0 AK T 1 時, 加以適當之 時, 加以適當之 i < IH ( Holding current) T 2 i K > 0 i K < 0 i AK i = v = v T T2 T1 - T 2 T 1 i T T 2 T 1 i V RB I H i > i > i 1 2 3 V FB v T2 T1 ( v AK ) Typical Applications of SCR and TRIAC Converter power control (1) Phase control (2) Integral cycle control SSR (Solid State Relay) or AC Switch Page 11
可控開關 (Controllable Switches) 元件 :(1) Forced-commutated SCR (2) BJT, MOSFET, IBT, MCT,... 所欲之特性 : 穩態 : 暫態 : (1) Off : Leakage current v T Control signal i T Switching speed Switching losses i T v T - p T = v T i T (2) On :, RON V ON p T = v T i T i T V ON t RON V ON Conduction loss turn-on turn-off (Switching losses) Power BJT Current-controlled device I B C B I C E Turn on: I B I C,sat / β min Page 12
Power BJT Voltage ratings: (primary breakdown) BV SUS, BV CEO, BV CBO V CB,max (E is open circuited) V CE,max (B is open circuited) V CE, max when I C 0 Secondary breakdown: Caused by large di/dt at turn-on instant. Power BJT β is smaller compared with small-signal BJTs. Hard saturation and quasi-saturation: Quasi-saturation: I B = I C,sat / β Hard-saturation: min i C I B Conduction loss Switching speed v CE I B > I C,sat / β min Page 13
Power MOSFET Voltage-controlled device Turn on: v i S > v S, th, steady state 0 (very small) v S D v S v S, th Parasitic C S Power MOSFET v S,max > v > S v S, th v S R = k DS,on i BV D,sat 2.5 ~ 2.7 DS, R on, P switching Light load: Switching loss dominant : v P = Q v f S g g S Q g = total gate charge Heavy load: sw Conduction loss dominant : v R S DS,on i D 1/ R on v > v S2 v S1 i > i D2 i D1 D1 v DS S1 Page 14
Cool MOSFET It is a new revolutionary technology for high voltage power MOSFETs. It implements a compensation structure in the vertical drift region of a MOSFET in order to improve the on-state resistance. R DS,on, Q g, θ JA slightly higher (~ 10%) Pulse current rating is lower. Page 15
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Power MOSFET 與 Power BJT 之比較 Power MOSFET (Enhancement mode) v S - S D Power BJT I B B C E I C 觸發控制 Turn on: 導通特性 : 觸發控制 Turn on: 導通特性 : { { { { v > v, i 0( very small ) S S, th steady, state 為電壓控制元件需有特殊驅動電路以加速 switching speed V ON = 0, R ON 較大, 但綜合導通損較大 電阻之溫度係數為正, 無 Thermal run away 問題, 並聯分流特性佳 I B> ICsat, / βmin, 為電流控制元件 需有電流放大之驅動電路, switching speed 比 MOSFET 慢 V ON = VCE, sat, RON 較小, 但綜合導通損較 MOSFET 小 電阻之溫度係數為負, 有 Thermal run away 問題, 不易並聯分流 RON V ON Page 20
IBT (Insulated-ate Bipolar Transistor) MOSTFET BJT IBT (Insulated ate Bipolar Transistor): -Combines the conduction characteristic of BJT and the control characteristic of the MOSFET Symbol and equivalent circuit: C(D) C(D) E(S) C(D) E(S) C(D) E(S) E(S) v S C(D) Printed circuit board 絞線以防電磁耦合干擾, 線短且勿太細 E(S) Damping filter Page 21
MCT (MOS-controlled Thyristor) MOSTFET Thyristor Combines the load characteristic of thyristor and the control characteristic of MOSFET Low on-state voltage Symbol A(Anode) K (Cathode) Turn on: 加負脈衝 VA 使 p-ch MOSFET M1 導通, 提供 BJT Q2 之基極電流, 使 MCT on Turn off: 加正脈衝 VA 使 n-ch MOSFET M2 導通, 將 BJT Q1 之基極與射極短接, 使 MCT off. Thyristor A D2 M2 S2 Q1 Q2 K S1 D1 M1 - Page 22
Triggering Devices ( 觸發元件 ) 產生觸發控制脈波, 以觸發功率半導體開關 蕭克萊二極體 (Shockley diode), Four-layer diode DIAC UJT (Uni-junction Transistor) PUT (Programmable Uni-junction Transistor) SUS (Silicon Unilateral Switch) SBS (Silicon Unilateral Switch) 其他 蕭克萊二極體 (Shockley diode) 沒有 ate 之 SCR on 及 off: v V ON, i < I OFF AK FB AK H 符號 : A K Page 23
DIAC ( 沒有 ate 之 TRIAC) on 及 off: v > 0: v V ON, i < I OFF AK AK FB AK H v < 0: v V ON, i < I OFF AK AK RB AK H 符號 : i AK T 1 T 2 V RB I H v AK I H V FB 單接面電晶體 (Uni-Junction Transistor, UJT) E B 2 B 2 r B 2 p n E V D I E r B1 B 1 V EB - B 1 TO-18 package B 1 E B 2 B2 electrically connected to case Page 24
Emitter Characteristic Curve B 2 IE ( ma ) V EB - E I E B 1 V BB I V V V V I E V EB P VEB ( V ) V P Peak voltage V V = D r rb1 r V = V ηv p B2, B1 D B2, B1 B1 B2 r η = B1 : ( Intrinsic standoff ratio, 本質分立比 ) rb1 rb2 Application: Relaxation OSC. ( 鬆弛振盪器 ) V C1 V P V V t R 1 E T 2 B V 2 BB C 1 V C1 R 2 R 3 B 1 V o1 V o2 T 1 V o1 V o2 T T R 1 C 1 R 1 C 1 t Positive going pulse t Page 25
Programmable UnijunctionTransistor, PJT) P N Pn A A Q1 A N Q2 K K K V p = V D R3 R R 2 3 V BB = V D ηv BB η 可由外加之電阻定之 V p = V D R3 R R 2 3 V BB = V D ηv BB R 1 R 2 A V V o3 o1 V o 2 V BB K C 1 R R 3 4 T 2 T 1 Page 26
SiC(Silicon Carbide) Power Devices Page 27
Introduction to SiC Silicon Carbide (SiC) is a wide-bandgap semiconductor, which has been intensively studied in the recent years, due to its physical properties, such as high breakdown field, high saturated drift velocity and high thermal conductivity. This characteristics make SiCa very good candidate for the applications in which high temperature, high radiation intensity, high voltage or highpower dissipation are involved, such as temperature sensors, nuclear radiation detectors, UV detectors, microwave devices and power devices. Although of the high potential of this material for the use in the electronic industry, the SiC technology shows some limitations and requires further study in order to obtain electronic devices of the same quality standards as Sitechnology: the bulk growth of SiC is still very expensive and material quality is still lower than device production requirements; the epitaxialgrowth is necessary to obtain device-quality material, but it requires high temperature processes; selective doping of SiC layers requires the use of ion implantation, since the diffusion coefficients for the doping species are too small for practical applications; the realization of ohmiccontacts on SiCis difficult and requires high temperature processes; the thermal oxidation of SiCis difficult due to the high temperature needed and the qualityof the material obtained is still lower respect to Sioxidation. These limitations underline the need of further study in the SiCfield. In particular, the growth of epitaxiallayers is a first-step process for the realization of a wide variety of electronic devices. Page 28