Download DC/DC Converter with Transparent Electronics for application on

Master of Electrical and Computers Engineering
DC/DC Converter with Transparent
Electronics for application on Photovoltaic
Panels
Supervisor: Vitor Grade Tavares
Second Supervisor: Pedro Miguel Cândido Barquinha
Second Supervisor: Pydi Ganga Bahubalindruni
Romano Torres
19th July 2013
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Outline
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Motivation
Objectives
a-IGZO TFTs
DC/DC Converter
Amplifier
Regulator
Fabrication
Conclusions
Future Work
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Motivation
• To construct circuits on flexible substracts, such as
plastic, glass:
– Possible to embody in photovoltaic panels.
• Low cost fabrication at room temperature.
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Objectives
• Design of a boost DC/DC converter using transparent
electronics in order to have an increased and stable
voltage level with direct current.
– Vout > 1.5*Vin;
– Efficiency >= 40%
• Fabrication of the circuit in CENIMAT/UNL.
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a-IGZO TFTs
Problems:
• High parasitic resistance;
• P-type transistors with low performance;
• Threshold voltage shift.
Staggered bottom-gate TFT structure
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Voltage Boosting Stage – DC/DC converter
• Indutors are avoided due to
their low performance in
transparent technology;
• Capacitor is used to save
charge in electric field;
• Vdd < Vout < 2*Vdd
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Voltage Boosting Stage - out of phase
clock signals
Lower variation of Vout level.
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2 Voltage Boosting Stages in Cascade
• To increase the voltage
level twice;
• Parasitic effects reduce
the efficiency;
• 4 TFTs of 320 μm in
parallel for each diodeconnection are used;
• Vdd < Vout << 3*Vdd
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Separation between Boosting Stages
• Allow a stable voltage
level at node E;
• Avoid clock
feedthrough in TFT1 and
TFT2.
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3 Boosting Stages in Cascade
• Proposed DC/DC
converter includes 3
Voltage Boosting
Stages;
• Settling time is
increased.
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Bootstrapping Stage – Proposed DC/DC converter
• Bootstrapping stage is used
to reduce the settling time of
the circuit;
• Power consumption is
negligble;
• Small capacitors and
transistors can be used.
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Comparison with previous DC/DC
converters in the same technology
DC/DC converter from other authors
Proposed DC/DC converter
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DC/DC Converter - Simulation
Output voltage
Bootstrapping
Cross-connected
With Load
Without Load
I_load = 162 μA
Vout=16.37 V
Vout=35.5 V
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Efficiency
• The supplied current of each voltage source is measured
(I_in=167 μA);
• The currents multiplied by the supplied voltage (Vin=10V) are
added, resulting in the input power;
• With the same current for each voltage source, efficiency is:
• The current supplied in bootstrapping stage is very low
(I_bs=0.12μA);
• The efficiency is: 39.93%
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3 Voltage Boosting Stages - Simulation
Voltage levels for each stage
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DC/DC converter - Layout
3068.55 μm
5793.55 μm
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10 DC/DC converters in parallel
- The equivalent resistance of 10 converters
in parallel is lower than with only one
converter.
Output voltage
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Final circuit with regulation
Circuit specifications:
• Vdd = 10 V
• R1 and R2 >> RL
Objectives:
• Vout ≃ 20 V
• 50% lower ΔV
Advantage:
• More stable voltage level
even with load variation.
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Proposed Amplifier – Block diagram
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Amplifier
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Differential Stage
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Positive Feedback Stage
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Source-Follower Stages
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Common-Source Stages
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Phase Compensation
-In order to have higher phase margin.
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Gain and Phase Response
Gain: 36.7dB
Phase Margin:
83.79°
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Proposed Amplifier - Layout
2383.8 μm
2450 μm
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Regulator
Voltage levels
Vout = 17.65 V
The voltage variation with the load decreased 80%.
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Final Circuit - Layout
14557.1 μm
18709.55 μm
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Fabrication
DC/DC converter with bootstrapping and 2 boosting stages
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Conclusions
• DC/DC converter:
– Wide transistors reduce parasitic resistance;
– Bootstrapping stage decreases settling time;
– 10 converters in parallel reduce the parasitic
resistance and allow more voltage boosting stages,
increasing the output voltage level.
• Amplifier:
– Good phase margin was achieved;
– Voltage gain is enough for the regulation;
• Regulator:
– 80% lower fluctuation of the voltage level with load
variations.
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Future Work
• Improve the design of the amplifier to
increase the gain;
• PWM regulation with duty-cycle variation.
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The End
Thank you!
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