Power Supply Block DiagramPower Supply Block Diagram H. Chan; Mohawk College 1 HalfHalf--Wave RectifierWave Rectifier 7.0V2V SP −= ⎟ ⎟ ⎞ ⎜ ⎜ ⎛ −= Pd 00833.0 1VV V ⎟ ⎠ ⎜ ⎝ FL Pdc CR V00480 FL P r CR V0048.0 V = H. Chan; Mohawk College 2 FL t FullFull--Wave RectifierWave Rectifier 7.0V707.0V sP −= ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −= Pdc CR 00417.0 1VV V ⎟ ⎠ ⎜ ⎝ FL Pdc CR V00240 V FL P r CR V0024.0 V = t H. Chan; Mohawk College 3 FL CR t BridgeBridge--Type RectifierType Rectifier 4.1V2V sP −= ⎟ ⎟ ⎞ ⎜ ⎜ ⎛ −= Pdc 00417.0 1VV V ⎟ ⎠ ⎜ ⎝ FL Pdc CR V00240 V FL P r CR V0024.0 V = t H. Chan; Mohawk College 4 FL CR t More Equations . . . More Equations . . . Rithi ti V V + 1 736 V Rearranging the previous equations: V P = V dc + 1.736 V r The ripple voltage as a percentage of the dc voltage is: V 100% x V V ripple dc r = The diode(s) must be rated to withstand the surge current: P V where R W is the transformer winding’s W P surge R V I = W g resistance given by: FLNL W I VV R − = H. Chan; Mohawk College 5 FL I Comparison of Different Types of RectifiersComparison of Different Types of Rectifiers  Half-wave rectifier needs only a single diode but ripple is twice those of the other types. ll ifi i d  Full-wave rectifier requires a centre-tapped transformer and its output voltage is about half those of the other types.those of the other types.  Bridge-type rectifier is best overall even though it requires four diodes because the diode bridge is often available in a single package. However, if a single diode in the bridge is defective, the whole package has to be replaced H. Chan; Mohawk College 6 whole package has to be replaced. Line RegulationLine Regulation is a measure of the effectiveness of a voltage regulatoris a measure of the effectiveness of a voltage regulator to maintain the output dc voltage constant despite chan ges in the supply voltage. o V VmVregulationLine Δ =)/( gppyg i V VmVregulationLine Δ )/( i o V x V V regulationline 100 % Δ Δ = H. Chan; Mohawk College 7 oi VVΔ Load RegulationLoad Regulation i f th bilit f l t t i t iis a measure of the ability of a regulator to maintain a constant dc output despite changes in the load current. o I V AmVregulationLoad Δ Δ =)/( L I g Δ )( V 100 Δ oL o V x I V regulationload 100 % Δ Δ = H. Chan; Mohawk College 8 Other SpecificationsOther Specifications A d fi iti f lt l ti iA common definition for voltage regulation is: 100(%) x VV regulationVoltage FLNL − =() V gg FL The ability to reduce the output ripple voltage is: )( )( log20)( inr outr V V dBrejectionRipple −= )(inr Source resistance of regulator is: ΩΩ Δ Δ = mor I V R o s H. Chan; Mohawk College 9 g ΔI L Zener Diode Voltage RegulatorZener Diode Voltage Regulator I-V Characteristic Circuit I ZM H. Chan; Mohawk College 10 ZM [...]... H Chan; Mohawk College 30 78XX Regulator with Pass Transistor 0 7 R1 = I max 0 7 R2 = I R2 H Chan; Mohawk College Q1 starts to conduct when VR2 = 0.7 V R2 is typically chosen so that max IR2 is 0.1 A Power dissipation of Q1 is i P = (Vi - Vo)IL Q2 is for current limiting protection It conducts when VR1 = 0.7 V Q2 must be able to pass ; max 1 A; but note that max VCE2 is only 1.4 V 31 78XX Floating... a variable regulator by replacing R2 with a pot However, However there are several disadvantages: Minimum output voltage is Vreg instead of 0 V IQ is relatively large and varies from chip to chip chip Power dissipation in R2 can in some cases be quite large resulting in bulky and expensive equipment A variety of 3-terminal variable regulators are available, e.g LM317 (for +ve output) or LM 337 (for . Power Supply Block DiagramPower Supply Block Diagram H. Chan; Mohawk College 1 HalfHalf--Wave RectifierWave. regulator to maintain the output dc voltage constant despite chan ges in the supply voltage. o V VmVregulationLine Δ =)/( gppyg i V VmVregulationLine Δ )/(