Switching Regulator Circuit
This example introduces the switch D. C. regulated power supply circuit of buck-mode +5V series. It is composed of power supply circuit, impulsator, voltage sampling or pulse width modulation circuit, buffering driver circuit and it is showed as the picture 5-38. The input converting circuit consists of mains transformer, T, commutation diode VD1-VD4, fi
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lter capacitor C1, current-limiting resistor and voltage regulator diode VS. The impulsator consists of time-base integrated circuit IC, resistor, R1, R2 and capacitor, C2, C5. The voltage sampling or pulse width modulation circuit is composed of capacitor, C3, resistor, R3-R5, R11-R13 and transistor V4 and V5. (View) The switch D. C. regulated power supply circuit introduced in the example can supply 3-15V D. C. voltage and its maximum current is 150mA, which meet the miniaturized electronics` power supply. Work`s Principle of the CircuitThe switch D. C. regulated power supply circuit is composed of rectifying and wave-filtering circuit, switch control circuit and voltage regulator circuit and it is showed as the picture 5-37. The rectifying and wave-filtering bridge, UR, commutation diode, VD1, VD2 and filter capacitor, C1 and C3. The switch control circuit consists of resistor, R2 and R4, voltage regulator diode, VS1 and field effect transistor, VF. The voltage regulator circuit is composed of resistor R1, R3, R5, voltage regulator diode VS2, transistor, V, diode, VD3, filter capacitor C2 and three-terminal integrated regulator IC1 and IC2. (View) When it isbeingused, it`s not proper to take voltage from C5 directly. It`s imposible to allow short circuit happened, otherwise it`ll burn V1 and V2. Because when short circuit takes place, the electric currentin coil LO of flyback transformer B1 will increase rappidly. The...