Power Supply Design PPT
Transcript of Power Supply Design PPT
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Introduction to Power supply topologiesBy Manish
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AGENDA : Power supply design
Introduction
Basic requirements
Regulator Classification
Switching Topologies
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INTRODUCTION
Power converter
Transfers energy One V * I format to another V * I format.
A circuitry monitors Vout deviations related to Vin, I-out, T° etc.
If Vout deviates from its target, an error is created and fed-back
to the power stage for action.
The action is a change in the control variable: duty-cycle (VM),
peak current (CM) or the switching frequency.
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INTRODUCTION CONTD.
Applications Overview
Analog + High speed design : PLL ( Low noise, low voltage) Dc motors ( High current ) Television Display LED / LCD drivers ( Very high voltage) Digital (Low voltages , Higher power – Load regulation )
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Characteristics
Basic Design requirement
Voltage input Voltage Output Current Output Line regulation Load regulation Thermal Stability Efficiency Output Ripple voltage limit Source reflected Noise : EMI /EMC
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Classification
Shunt regulator Series regulator Linear dropout regulator (LDO) Non-Isolated Switching topology
-Buck regulator-Boost regulator-Buck-Boost regulator-Inverting regulator
Isolated Switching topology-Fly back regulator-Push pull regulator-Full bridge regulator
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BUCK topology
BUCK topology
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Non Isolated topologies
BUCK topology BOOST topology
Inverting topology BUCK - BOOST topology
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Isolated Topologies
FLYBACK topology
PUSH-PULL topology
FULL BRIDGE topology
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Switching regulator parameter
Switching frequency Dynamic response Noise
Power dissipation Static power dissipation Dynamic power dissipation
Galvanic Isolation
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Case study of Buck topology
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Modulator
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Case study continued
Error amplifier
* Generates Loop-back control voltage * Loop back gain
* Also contribute to stability of Supply control loop.
Output LC filter Detailed in next section
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Basic Design Equation
Filter Inductor equation:
VOUT (VIN(MAX) - VOUT)L = ======================
VIN(MAX) x f x IOUT x LIR
where: f = switching frequency IOUT = maximum DC load current LIR = ratio of AC to DC inductor current,typically 0.3.
The peak current can be calculated by: VOUT * (VIN(MAX) - VOUT)
IPEAK = ILOAD + ——————————— 2 x f x L x VIN(MAX)
Filter Capacitor equation:
VNOISE(p-p) = IRIPPLE x (RESR + 1 / (2 x pi x f x CF))
Current sense resistors: Rsense = Vsense / Ipeak.
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Modern regulator feature
Modern regulator feature
- Logic Shut-down control
- Synchronization control
- Soft-start
- Power sequencing
- Accurate Digital voltage control / Monitoring through communication protocol like I2C
- Self voltage monitored outputs
- Thermal / Over current / Short circuit protection
- High power ( low voltage ,High current , High Effi > 95% )
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Advantages- Greater efficiency - Other advantages include smaller size and lighter weight
lower heat generation due to higher efficiency.
Disadvantages- Greater complexity,- Switching Noises back to main power.
Advantage & disadvantages
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Buck: used the reduce a DC voltage to a lower DC voltage. Boost: provides an output voltage that is higher than the
input. Buck-Boost (invert): an output voltage is generated
opposite in polarity to the input. Flyback: an output voltage that is less than or greater than
the input can be generated, as well as multiple outputs. Also, some multiple-transistor converter topologies will be
presented: Push-Pull: A two-transistor converter that is especially
efficient at low input voltages. Half-Bridge: A two-transistor converter used in many off-
line applications. Full-Bridge: A four-transistor converter (usually used in off-
line designs) that can generate the highest output power of all the types listed.