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MALVINO Electronic PRINCIPLES SIXTH EDITION Regulated Power Supplies Chapter 24 Power supply regulation Vline Vout RL VNL - VFL Load regulation = x 100% VFL VHL - VLL Line regulation = x 100% VLL A zener diode shunt voltage regulator RS Power supply Vin VZ RL Vout Vout = VZ Vin - Vout IS = RS IL = Vout RL IZ = I S - IL Improved shunt voltage regulator RS Power supply Vin VZ RL Vout Vout = VZ + VBE Vin - Vout IS = RS IL = Vout RL IC IS - IL Zener follower is a series voltage regulator. Power supply RS Vin PD (Vin - Vout)IL Vout = VZ + VBE VZ RL Vout Two-transistor voltage regulator Vout = R3 + R4 R4 (VZ + VBE) +Vin R1 R2 Q2 R3 Q1 VZ RL R4 Vout Improved voltage regulator Vout = R2 + R3 R3 VZ +Vin R2 R1 RL VZ R3 Vout Regulator with current limiting Vout = Q1 R2 + R3 R3 VZ +Vin R4 R1 R5 VZ R2 Q2 RL VBE ISL = R4 R3 Vout VL Simple current-limiting Vreg Constant current region VBE(Q2) 0.6 V ISL IL Foldback current limiting Q1 +Vin R7 K= R6 +R7 VBE ISL = KR4 R4 R6 R1 R7 R2 RL R5 VZ Q2 R3 (1-K)Vout Imax = ISL + KR4 Foldback current-limiting VL Vreg Foldback current region ISL Imax IL Monolithic regulator with current booster Vin Q1 1 R1 LM78XX 3 2 Vout RL Current booster with current limiting R2 Q2 Vin Q1 1 R1 LM78XX 3 2 Vout RL DC-to-DC converter +Vin R1 Q2 T1 vin Q1 Q3 R2 RL Switching regulators • The pass transistor is switched between cutoff and saturation. • Better efficiency than linear. • Topologies: – Buck: steps the voltage down – Boost: steps the voltage up – Buck-boost: inverts the input voltage Buck regulator Q L +Vin D C RL R2 PWM Vout = DVin VREF R1 Boost regulator Vkick Vp +Vin L Q D C RL R2 PWM Vp = Vin + Vkick VREF R1 Buck-boost regulator Q +Vin L D C RL R2 PWM VREF R1 Monolithic buck regulator 5 IN OUT 4 L +Vin D LT1074 C1 C3 RL R2 COMP 2 FB 3 R1 R3 C2 1 Vout = R1 + R2 R1 (2.21 V) Using the charge pump of the MAX633 IC +15 V +Vin 4 IN OUT CP MAX633 5 C3 6 -12 V C1 D2 1,3,7 D1 C2