Lesson 9 - Power Supply Circuits - Presentation.pdf
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Chapter 30 Power Supply Circuits Topics Covered in Chapter 30 30-1: The Power Supply Sub-System 30-2: Half-wave rectifier 30-3: Transformer 30-...
Chapter 30 Power Supply Circuits Topics Covered in Chapter 30 30-1: The Power Supply Sub-System 30-2: Half-wave rectifier 30-3: Transformer 30-4: Full-wave rectifier 30-5: Bridge rectifier © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, 30-2 Topics Covered in Chapter 30 30-6: Power Supply Filtering 30-7: Peak Inverse Voltage 30-8: Other Power Supply Topics 30-9: Troubleshooting 30-10: Voltage Multipliers © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-3 30-1: The Power Supply Sub- System All electronic products, equipment and systems have a power supply. The power supply is the main sub-system that makes the rest of the circuits and equipment work. A power supply is a collection of components and circuits that supply one or more DC voltages to the circuits. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-1: The Power Supply Sub- 30-4 System Types of power supplies include: Battery with battery charger AC operated power supply High-frequency AC © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-5 30-1: The Power Supply Sub- System Figure 30-1 below shows a block diagram of an AC operated power supply. Figure 30-1 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-1: The Power Supply Sub- 30-6 System In Figure 30-1 (previous slide): The main power source is the AC 120 V 60 Hz. The input voltage is filtered to prevent high frequency spikes and noise and to block high-frequency signals. The filtered AC is supplied to a transformer to step up or step down the voltage. A rectifier then converts a sine wave into DC pulses at a 60 Hz rate. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-7 30-1: The Power Supply Sub- System In Figure 30-1: Next the DC pulses are passed to a filter which smoothes the pulses into a constant DC voltage. This output can be used for some applications. In most applications, this DC voltage is further processed with a regulator circuit. Many power supplies generate multiple DC voltages. Multiple DC voltages are produced from the main filtered DC using multiple regulators or with DC-DC converters. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-8 30-2: The Half-Wave Rectifier Half-wave rectifier Has a diode in series with the load resistor Load voltage is a half-wave output © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-9 30-2: The Half-Wave Rectifier Figure 30-4 (a) shows input to half-wave rectifier; (b) circuit; (c) output of half-wave rectifier. Figure 30-4 Ideal: VP(in) = VP(out) © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-10 30-2: The Half-Wave Rectifier Half-wave rectifier signals The dc value of the output is the average value. Vdc = VP/p fout = fin Second approximation: VP(out) = VP(in) - 0.7 V © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-11 30-3: The Transformer Input transformer Step down Voltage steps down Current steps up Secondary voltage equals the primary voltage divided by the turns ratio © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-12 30-3: The Transformer When the turns ratio (N1/N2) is greater than 1, the primary voltage is stepped down. When the turns ratio is less than 1, the primary voltage is stepped up. Dotted ends have the same instantaneous phase. Full-wave rectifiers require a winding with a center tap. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-13 30-4: The Full-Wave Rectifier Full-wave rectifier Has a center-tapped transformer with two diodes and a load resistor Load voltage is a full-wave signal whose peak is half of the secondary voltage © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-14 30-4: The Full-Wave Rectifier Figure 30-7 (a) shows a full-wave rectifier circuit. Figure 30-7 (a) © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-15 30-4: The Full-Wave Rectifier Figure 30-7 (b) shows the equivalent circuit for positive half cycle Figure 30-7 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-16 30-4: The Full-Wave Rectifier Figure 30-7 (c) shows the equivalent circuit for negative half cycle Figure 30-7 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-17 30-4: The Full-Wave Rectifier Figure 30-7 (d) shows full-wave output Figure 30-7 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-18 30-4: The Full-Wave Rectifier The dc value of the output is the average value. Vdc = 2VP/p fout = 2fin The input to each diode is half the secondary voltage. Second approximation: VP(out) = VP(in) - 0.7 V © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-19 30-5: The Bridge Rectifier Bridge rectifier Has four diodes Load voltage is a full-wave signal with peak value equal to the secondary voltage © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-20 30-5: The Bridge Rectifier Figure 30-8 (a) shows a bridge rectifier circuit. Figure 30-8 (a) © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-21 30-5: The Bridge Rectifier Figure 30-8 (b) shows equivalent circuit for positive half cycle Figure 30-8 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-22 30-5: The Bridge Rectifier Figure 30-8 (c) shows equivalent circuit for negative half cycle Figure 30-8 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-23 30-5: The Bridge Rectifier Figure 30-8 (d) shows full-wave output Figure 30-8 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-24 30-5: The Bridge Rectifier The dc value of the output is the average value. Vdc = 2VP/p fout = 2fin Second approximation: VP(out) = VP(in) - 1.4 V © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-25 30-5: The Bridge Rectifier Choke-input filter LC voltage divider XL >> XC The average value of a rectified signal passes to the load resistor © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-26 30-5: The Bridge Rectifier L. Vin C RL Vout When XL >> XC: XC Vout @ Vin XL © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-27 30-6: Power Supply Filtering The purpose of the filter in a power supply is to take the DC pulses produced by the rectifier and smooth them into a constant DC voltage. The two ways to visualize the filtering process are in the: Frequency domain Time domain © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-28 30-6: Power Supply Filtering In frequency domain analysis, rectifier output pulses as non-sinusoidal signals are viewed. These pulses are comprised of a fundamental sine wave and an infinite number of harmonics. Half and full wave rectified sine waves are made up of a fundamental sine wave and even harmonic sine waves. With 60 Hz pulses of the half-wave rectifier, 60 Hz and harmonics of 120, 240, 360, 480, and other even numbered sine waves are produced. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-29 30-6: Power Supply Filtering To eliminate the generated harmonics, a low-pass filter is the obvious choice. A cutoff frequency of well below the base pulse frequency of 60 Hz or 120 Hz is selected and the attenuation will be high enough to eliminate most harmonics. Figure 30-9 (next slide) shows a frequency domain plot of the output of a full-wave rectifier showing the fundamental and harmonic components. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-30 30-6: Power Supply Filtering Frequency domain plot Figure 30-9 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-31 30-6: Power Supply Filtering In Figure 30-9 (previous slide), note the overlaid low- pass filter response curve showing how the filter will attenuate the harmonics and fundamental frequency. The result is near constant DC voltage. Because of the gradual slope of the filter, not all harmonics are filtered out. Some residual signal called ripple will still be present. The ripple signal is typically a low value and will not be a problem. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-32 30-6: Power Supply Filtering Time domain analysis is a more common way to analyze a filter. This analysis makes use of RC and LR time constants. By considering the capacitor charge-discharge curve, the time constant and the pulse frequency, values can be selected to remove the ripple. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-33 30-6: Power Supply Filtering Capacitor-input filter Most widely used The peak value of the rectified signal passes to the load resistor With a large capacitor, ripple is small © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-34 30-6: Power Supply Filtering Figure 30-12 (next slide) shows the details for the capacitor charge and discharge process. The capacitor charges to the peak of the sine wave less any diode drops. Then, as the diode turns off and the capacitor discharges through the load. On the next DC pulse, the diode turns on and the capacitor recharges to the peak and the process is repeated. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-35 30-6: Power Supply Filtering Capacitor charge and discharge process Figure 30-12 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-36 30-7: Peak Inverse Voltage Peak inverse voltage Maximum voltage across the nonconducting diode of a rectifier circuit Voltage must be less than diode breakdown voltage © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-37 30-7: Peak Inverse Voltage Diode ratings Half-wave rectifier with capacitor-input filter: PIV = 2VP Idiode = Idc Full-wave rectifier with capacitor-input filter: PIV = VP Idiode = 0.5Idc Bridge rectifier with capacitor-input filter: PIV = VP Idiode = 0.5Idc © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-38 30-8: Other Power Supply Topics Real transformers usually specify secondary voltage at a rated load current Slow-blow fuses are often used to protect against surge current Average diode current in a half-wave rectifier equals the dc load current In a full-wave or bridge, the average current in any diode is half the dc load current © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-39 30-8: Other Power Supply Topics A regulator keeps the output constant at a desired level and provides the added bonus of reducing the ripple. The simplest form of regulator is the zener diode. In most applications, the regulator is an integrated circuit (IC) that automatically adjusts the output voltage if input AC line voltage or load changes occur. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-40 30-9: Troubleshooting Almost every piece of electronics equipment has a power supply. If a piece of electronics equipment is not working properly, start your troubleshooting with the power supply. More often than not, equipment failure is caused by troubles in the power supply. © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-41 30-9: Troubleshooting Typical bridge supply problems No output - - blown fuse, two or more diodes open, load shorted Low output/extra ripple - - bad filter, open diode, shorted winding, overload Full-wave signal at output - - open filter capacitor Half-wave ripple frequency - - open diode © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-42 30-10: Voltage Multipliers Voltage multipliers A voltage doubler is similar to the peak-to-peak detector but uses rectifier diodes instead of small- signal diodes Voltage triplers and quadruplers multiply the input peak by factors of 3 and 4 © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-43 30-10: Voltage Multipliers Half-wave voltage doubler VP C1 D2 D1 C2 2VP © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-44 30-10: Voltage Multipliers Full-wave voltage doubler VP 2VP VP © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part. 30-45 Effects on voltage and current Ac line regulation can have an effect Bulk resistance of rectifiers causes a voltage drop Resistance of transformer windings causes a voltage drop Ac ripple increases and average dc decreases when load current increases © 2014 by McGraw-Hill Education. This is proprietary material solely for authorized instructor use. Not authorized for sale or distribution in any manner. This document may not be copied, scanned, duplicated, forwarded, distributed, or posted on a website, in whole or part.
