682q boost converter lecture 1
TRANSCRIPT
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EE682 Group Project Design
Prof. Ali Keyhani
Boost DC/DC Converter Design
Lecture #1 Power Switch Design
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Boost Converter Review
1. Circuit topology
Power Switch Design
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Boost Converter Review
2. Continuous conducting mode (CCM)
Current slope: VL/LWhere VL is inductor
voltage
Power Switch Design
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Boost Converter Review
3. Discontinuous conducting mode (DCM)
Inductor current is notcontinuous
Power Switch Design
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Design Tasks
1. Power switch design
2. Inductor design
3. Capacitor design
4. Drive circuit
Power Switch Design
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Design Specifications
1. Input voltage: 24 V
2. Output voltage: 48 V
3. Output power: 240 W
4. Inductor current ripple: 15 %
5. Capacitor voltage ripple: 0.1 %
Power Switch Design
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Power Switch Design
1. Power BJTs, Power MOSFETs, and IGBTs
1. BJTs greater capacity, low ON state loss
2. MOSFETs fast switching, voltage driven
3. IGBTs combined modules, powerful and expensive
Power Switch Design
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Power Switch Design
Illustrate the design procedures with a design example:
Design requirement:
A 240-watt DC/DC boost converter with Vin
=24V and
Vout=48V.
Power Switch Design
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Power Switch Design
1. Current and voltage rating requirements
Design:
Peak transistor current equals to
Iin=P/Vin=240W/24V=10A
Voltage rating requirements
VTmax
=Vout
+VF(diode)
=48+0.7V=48.7V
Power Switch Design
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Power Switch Design
2. Device selection based on the requirements
Design:
Candidate I: BJT 2N6547
IC
=15A>10A and VCE
=400V>48V
Candidate II: power MOSFET HUFA75307D3
ID=15A>10A and VDS=55V>48V
Power Switch Design
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Power Switch Design
Datesheet 2N6547
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Power Switch Design
Datesheet HUFA75307D3
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Power Switch Design
3. Base/Gate drive requirements
2N6547: For IC=15A, must have IB>=3A, not desirable
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Power Switch Design
3. Base/Gate drive requirements (contd)
HUFA75307D3 is voltage driven:
Threshold (mininum ON) gate-source voltage VGSth =4V
Maximum gate-source voltage VGSmax=20V
Can be driven by TTL (+5V) or CMOS logic +15V digital
circuits
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Power Switch Design
4. Transient performances
2N6547
Rise time: tr=1.0s
Fall time: tf=1.5s
HUFA75307D3
Rise time: tr=40ns
Fall time: tf=45ns
Power Switch Design
P S i h D i
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Power Switch Design
5. Selection
Power MOSFET HUFA75307D3
6. Switching loss
( ) ( )
( ) W768.01010060
1020
12
1048
2
1
9
3
___
=+
=
+=+==
OFFONdds
OFFlossONlossloss
lossSW ttT
IVWW
TT
WP
Power Switch Design
P S it h D i
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Power Switch Design
7. ON state loss
1. ON state time
2. ON state loss
( )
( ) W684.81073.25075.015
1020
1
1
1
62
3
1)(2_
_
=
=
==
trITT
WP ONDSDlossONlossON
s73.25sec48
247.048
1020
1131
=
+
=
+=
out
inFout
V
VVV
ft
Power Switch Design
P S it h D i
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Power Switch Design
8. Overall loss
Power Switch Design
9.452W__ =+= lossONlossSWloss PPP < PD = 45 W
(see the datasheet of HUFA75307D3)
P S it h D ig
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Power Switch Design
Calculation of junction to sink temperature difference
JCJClossJC
RtZPtT
)()(%)50(
=
C175TC2.31W452.9C/W3.3 jmax =
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Power Switch Design
HUFA75307D3 ON-resistance and turn-on and turn-off time
Power Switch Design