Regulated Linear Power Supply

Dual-Output Adjustable Linear Regulated Power

Supply

Block Diagram

Simple Description

• Transformer: “Downconvert” the AC line voltage to a smaller peak voltage Vm, usually about 2-3 Volts larger than the ultimately desired DC output.

• Diode Rectifier Circuit: produce a waveform with large DC component.

• Filter: smooth out the rectified sinusoid. • Regulator: eliminate residual ripple

Tin

Half-Wave Rectifier

Cause of ripple: the capacitor is discharged for almost an entire period.

inversion

Ripple Reduction: Do not allow the capacitor to discharge so frequently

An Inverting Half-Wave Rectifier

If Vin >0, D1 and D2 are off.If Vin <0, D1 and D2 are on and Vout>0.

An Non-Inverting Half-Wave Rectifier

If Vin >0, D1 and D2 are on, Vout>0.If Vin <0, D1 and D2 are off.

Full-Wave Rectifier

Inverting

Non-Inverting

Full-Wave RectifierAlternative Drawing

Inverting Non-InvertingFull-Wave A.K.A. Bridge Rectifier

Using Constant Voltage Diode Model

Vout=-Vin-2VD, on Vout=Vin-2VD, on

Input versus Output

|Vin|<2VD,on

Addition of the Smoothing Capacitor

Modification of Ripple Estimation Formula

Modification:1.Turn-on voltage2.1/2 to account for inversion of negativepeaks.

Maximum Reverse Voltage

VB=VD,on

VA=VP

VAB=VP-VD,on

Maximum reverse voltage is approximately Vp

Vp is the amplitude of Vin

Compare Maximum Reverse Bias Voltage to Half-Wave Rectifier

A reverse diode voltagemust sustain larger reverse bias voltage

Currents as a function of time

Application of Bridge Rectifier

Summary

A Voltage Regulator Circuit

Schematic

Full-Wave RectifierAlternative Drawing

Inverting Non-InvertingFull-Wave A.K.A. Bridge Rectifier

Rectified Waveform

Smoothing Capacitor

LM317/LM337

Without Load Resistance (CL=100 uF)

9.36 V and -9.36 V

Load Assumption

• Assume that the load draws 0.2 A of current

• Load resistance: 9.36V/0.2A=36.5 Ohms

Each capacitor is 100 uF.Resistor is 37.5 Ohms

Use Reload update curves

Increase capacitor from 100uF to 470 uF.

Reduced ripples

Extra Slides

I-V Characteristic of LED