EEL 3923C JD/ Module 2 Power Supply Design & Construction Prof

EEL 3923C JD/ Module 2 Power Supply Design & Construction Prof. T. Nishida Fall 2010 II. General Power Supply • Converts ac powerline voltage into DC voltage of required magnitude and stability for the electronic system    

Diode Voltage Filter Rectiﬁer Regulator

120 V(rms) 60 Hz ac line input Ref: Section 3.5, Sedra and Smith, Microelectronic Circuits, 5th Ed., Oxford, 2004. EEL 3923C, Fall 2010, T. Nishida 2 General Power Supply Design • Useful reference on power supply design

Ref: http://www.st.com/stonline/books/pdf/docs/1707.pdf

EEL 3923C, Fall 2010, T. Nishida 3 II.1 Transformer • Ideal loss-less transformer – No dissipation

– Voltage step-up/down determined ratio of coil turns on secondary/ primary

– Current has inverse ratio

– Impedance transformation Ref: http://www.mpdigest.com/issue/Articles/2009/oct/Mini/Default.asp EEL 3923C, Fall 2010, T. Nishida 4 Real Transformer • Real transformer

– Series resistance in windings, Rs, Rp

– Stray leakage inductance, Xs, Xp – Core losses

• Eddy current, Rc

• Magnetization, Xm

EEL 3923C, Fall 2010, T. Nishida 5 Module 2 Transformer Specs • EI30 series laminated transformer

Ref: http://ww2.pulseeng.com/products/datasheets/LT2010.pdf

EEL 3923C, Fall 2010, T. Nishida 6 LT SPICE Transformer Model

Ref: hp://ltspice.linear.com/soware/scad3.pdf

EEL 3923C, Fall 2010, T. Nishida 7 Module 2 Transformer LTSPICE Model • 8:1 transformer with series resistance • Output voltage depends on load current

File: Module2_Transformer_+_RL.asc

EEL 3923C, Fall 2010, T. Nishida 8 Module 2 Transformer Implementation • Sealed case, switch, LED power indicator, and fuse for safety (supplied in JD lab)

EEL 3923C, Fall 2010, T. Nishida 9 II.2 Diode Rectiﬁer • Purpose: Convert ac transformer output into waveform with non-zero DC component • What is DC component?

EEL 3923C, Fall 2010, T. Nishida 10 P/N Junction Rectiﬁer Diode • I-V characteristics i

• Equivalent circuit

Reverse bias Forward bias

EEL 3923C, Fall 2010, T. Nishida 11 General Purpose Rectiﬁer Diodes • Module 2 diode

Ref: http://www.fairchildsemi.com/ds/1N%2F1N4001.pdf

EEL 3923C, Fall 2010, T. Nishida 12 Module 2 Diode LTSPICE Model • Add 1N4004 diode model to LTSPICE diode model library – Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp – Open standard.dio using notepad or by double-clicking and using LTSPICE – Insert the following into the ﬁle .MODEL 1N4004 D(IS = 3.699E-09 RS = 1.756E-02 N = 1.774 XTI = 3.0 EG = 1.110 CJO = 1.732E-11 M = 0.3353 VJ = 0.3905 FC = 0.5 ISR = 6.665E-10 NR = 2.103 BV = 400 IBV = 1.0E-03 Iave=1000m Vpk=400 mfg=Fairchild type=silicon) – Close and restart LTSPICE • Insert a generic diode into your schematic • Right-click the diode; you should see a dialog box – Click ‘Pick New Diode’ – Select 1N4004 from the list of possible diodes – The diode should now look like:

Ref: http://www.fairchildsemi.com/models/PSPICE/Discrete/Diode.html

EEL 3923C, Fall 2010, T. Nishida 13 Half Wave Rectiﬁer • Circuit (LTSPICE)

EEL 3923C, Fall 2010, T. Nishida 14 Half Wave Rectiﬁer • Equivalent circuit using constant voltage model

• Effect of forward voltage drop

• Peak inverse voltage

EEL 3923C, Fall 2010, T. Nishida 15 Full Wave Rectifier • Disadvantages of half-bridge rectifier: maximum conduction angle of 180º • Possible fixes: • Use two half-bridge rectifiers (basic concept of center-tapped transformer approach) • Bridge rectifier (similar to Wheatstone bridge circuit)

EEL 3923C, Fall 2010, T. Nishida 16 Full Wave Rectiﬁer • Center-tapped transformer approach Where are the half-bridge rectiﬁers?

vS(t), vO(t)

PIV=2VS-VD t Ref. Sedra & Smith, Fig. 3.26

EEL 3923C, Fall 2010, T. Nishida Note: Effect of VD drop. 17 Full Wave Rectiﬁer • Bridge rectiﬁer approach

(a) Positive half-cycle (b) Negative half-cycle Which diodes are forward-biased? vS(t), vO(t)

PIV=VS-VD t

Ref. Sedra & Smith, Fig. 3.27 EEL 3923C, Fall 2010, T. Nishida What is the voltage drop?18 Module 2 Full Wave Rectiﬁer • Note the importance of the ground reference

EEL 3923C, Fall 2010, T. Nishida 19 II.3 Filter • Purpose: Reduce voltage ripple

• Need shunt capacitor to pass DC and ﬁlter ac frequencies EEL 3923C, Fall 2010, T. Nishida 20 Half Wave Rectiﬁer With Filter Cap • Goal: First order smoothing of output • Approach: Filter capacitor • Assume capacitor

initially uncharged, vC (t=0)=0V • Assume ideal diode for vS(t), vO(t) simplicity (i.e. neglect V T D Vr drop)

EEL 3923C, Fall 2010, T. Nishida 21 Half Wave Rectiﬁer With Filter Cap • Approximate Analysis C charges up from t=0 to t=T/4

iD=iC+iL

where iL=vO/R and iC=Cdvs/dt

Diode turns off at peak. Why?

vO(t=T/4) =VSpeak C discharges through R delivering load vO(t) current.

-t/RC vO=VSpeake Stops discharging when vO(t) less than vs t (t). vS (t)

EEL 3923C, Fall 2010, T. Nishida 22 Half Wave Rectiﬁer With Filter Cap • Approximate Analysis

Deﬁne ripple voltage, Vr: -T/R C VSpeak-Vr ≅VSpeake L

Assuming CR>>T,

Vr ≅ VSpeak(T/RLC)

Vr ≅VO (T/C)(IL/VO) v (t), v (t) 0.05VO ≅ IL T/C S O T Vr • Similar analysis for full wave rectiﬁer with ﬁlter capacitor • What changes? t

EEL 3923C, Fall 2010, T. Nishida 23 Capacitors Types Temperature Capacitor types Capacitance range Accuracy Leakage Comments stability Polarised capacitor - widely used in power Electrolyc 0.1 µF - ~1 F V poor V poor Poor supplies for smoothing, and bypass where accuracy, etc is not required. Exact performance of capacitor depends to a Ceramic 10 pF - 1 µF Variable Variable Average large extent on the ceramic used. Polarised capacitor - very high capacitance Tantalum 0.1 µF - 500 µF Poor Poor Poor density. Rather expensive and large - not widely used Silver mica 1 pF - 3000 pF Good Good Good these days except when small value accurate capacitors are needed. Polyester Inexpensive, and popular for non-demanding 0.001 µF - 50 µF Good Poor Good (Mylar) applicaons. High quality, oen used in filters and the like Polystyrene 10 pF - 1 µF V good Good V good where accuracy is needed. Used in many high tolerance and hash Polycarbonate 100 pF - 20 µF V good V good Good environmental condions. Supply now restricted. Polypropylene 100pF - 50 µF V good Good V good High performance and low dielectric absorpon. Teflon 100 pF - 1 µF V good V v good V v good High performance - lowest dielectric absorpon. Excellent for very harsh environments while Glass 10 pF - 1000 pF Good Good V good offering good stability. Very expensive. Porcelain 100 pF - 0.1 µF Good Good Good Good long term stability Oen used as variable capacitors in transmiers Vacuum and air 1 pF - 10 000 pF as a result of their very high voltage capability. EEL 3923C, Fall 2010, T. Nishida Ref: hp://www.radio-electronics.com/info/data/capacitor/capacitor_types.php 24 Capacitor Applications

Applicaon Suitable types Reasons Power supply smoothing Aluminium electrolyc High capacity, high ripple current High capacitance Aluminium electrolyc High capacitance, small size Audio frequency coupling Tantalum Cheap, but values not as high as Polyester / polycarbonate electrolycs Small, cheap, low loss Ceramic COG Small cheap, but higher loss than RF coupling Ceramic X7R COG

Polystyrene Very low loss, but larger than ceramic Small, low loss. Values limited to Ceramic COG around 1000 pF RF decoupling Small, low loss, higher values Ceramic X7R available than for COG types Close tolerance, low loss Silver mica Tuned circuits Close tolerance, low loss, Ceramic COG although not as good as silver mica Ref: hp://www.radio-electronics.com/info/data/capacitor/capacitor_types.php

EEL 3923C, Fall 2010, T. Nishida 25 Module 2 LTSPICE Simulation Half Wave with Filter Cap • Caution: Make sure + terminal of electrolytic capacitor is connected to positive secondary voltage lead • Select standard value capacitance by right- clicking capacitor

EEL 3923C, Fall 2010, T. Nishida 26 Module 2 LTSPICE Simulation Half Wave with Filter Cap • Note: Need to simulate long enough to reach steady-state – Start to save data after steady-state is reached

EEL 3923C, Fall 2010, T. Nishida 27 Module 2 LTSPICE Simulation Half Wave with Filter Cap • Note: Positive current deﬁned down in RL • Calculate percent ripple in output voltage

– Percent ripple = 100(Vr /VOmax )

EEL 3923C, Fall 2010, T. Nishida 28 Module 2 LTSPICE Simulation Full Wave with Filter Cap • Caution: Make sure + terminal of electrolytic capacitor is connected to positive secondary voltage lead

EEL 3923C, Fall 2010, T. Nishida 29 II.4 Regulator • Purpose: Active circuit to achieve nearly constant output voltage up to a max load current • Approaches – Open-circuit • Zener diode – Closed-circuit • Op-amp, transistor • Specialized regulator ICs

EEL 3923C, Fall 2010, T. Nishida 30 Operation at Reverse Breakdown— Zener Diodes • Operation at reverse bias i • Deﬁne VZ and IZ with opposite polarity -V -V • Circuit symbol Z ZK v -I • I-V characteristic ZK

-IZT

Figure 3.21, Sedra & Smith EEL 3923C, Fall 2010, T. Nishida 31 Zener Diodes • Parameters: Identify on I-V characteristic

• Q point (i=IZT and v=VZ)

• Zz= incremental resistance (slope = 1/Zz)

• ΔV=Zz Δ I

• IZK = minimum reverse current for operation in breakdown region • Equivalent circuit (piece-wise linear)

• VZ = VZ0 + ZzIZ for IZ > IZK

VZ _

EEL 3923C, Fall 2010, T. Nishida 32 Zener Shunt Regulator • Zener diode placed in parallel with load (shunt)

Ref: http://www.st.com/stonline/books/pdf/docs/1707.pdf EEL 3923C, Fall 2010, T. Nishida 33 Zener Shunt Regulator

• Line regulation: Deﬁned as change in output voltage, VO for change in line voltage, V+, for no load + • ΔVO=(rz/(rz+R)) ΔV • What is the effect of connecting a load?

• Load regulation: Deﬁned as ΔVo per 1mA when RL chosen to draw IL=1mA

• If ΔIL=+1mA, what is ΔIZ?

• Effect of ΔIZ on ΔVO? Check zener I-V curve.

• ΔVO = Zz ΔIZ

• What limits the lowest RL for the shunt regulator?

EEL 3923C, Fall 2010, T. Nishida 34 1N4728A – 1N4758A Zener Diodes

Ref: http://www.fairchildsemi.com/ds/1N%2F1N4745A.pdf

EEL 3923C, Fall 2010, T. Nishida 35 Module 2 Zener Diode LTSPICE Model • Add 1N4733A zener diode model to LTSPICE diode model library – Navigate to C:\Program Files\LTC\LTspiceIV\lib\cmp – Open standard.dio using notepad or by double-clicking and using LTSPICE – Insert the following into the ﬁle * 1N4733 * Motorola 5.1V 1W Si Zener pkg:DO-41 1,2 .MODEL 1N4733 D(IS=7.03E-16 RS=0.871 TT=5.01E-8 CJO=1.89E-10 VJ=0.75 M=0.33 BV=5.059 IBV=0.049 Vpk=5.1 mfg=Fairchild type=zener) – Close and restart LTSPICE • Insert a generic diode into your schematic • Right-click the diode; you should see a dialog box – Click ‘Pick New Diode’ – Select 1N4733 zener diode from the list of possible diodes – The zener diode should now look like:

Ref: http://www.duncanamps.com/spice/diodes/zener.mod

EEL 3923C, Fall 2010, T. Nishida 36 Module 2 Zener LTSPICE Model • Zener diode placed in parallel with load (shunt)

Ref: http://www.st.com/stonline/books/pdf/docs/1707.pdf EEL 3923C, Fall 2010, T. Nishida 37 LM2940 Low Dropout Pos Regulator

EEL 3923C, Fall 2010, T. Nishida Ref: http://www.national.com/ds/LM/LM2940.pdf 38 LM2940 Low Dropout Pos Regulator

Ref: http://www.national.com/ds/LM/LM2940.pdf EEL 3923C, Fall 2010, T. Nishida 39 LT1086 Low Dropout Pos Regulator

EEL 3923C, Fall 2010, T. Nishida Ref: hp://cds.linear.com/docs/Datasheet/1086ﬀs.pdf40 LT1086 Low Dropout Pos Regulator

EEL 3923C, Fall 2010, T. Nishida Ref: hp://cds.linear.com/docs/Datasheet/1086ﬀs.pdf41 LM2940 Standard Pos Regulator

EEL 3923C, Fall 2010, T. Nishida Ref: http://www.fairchildsemi.com/ds/LM/LM7805.pdf 42 LM3940 Regulator 5V to 3.3V Converter

EEL 3923C, Fall 2010, T. Nishida Ref: http://www.national.com/ds/LM/LM3940.pdf 43