L4960 by a monolithic switching power supply

  
As shown in FIG constituted by L4960 + 5 ~ + 40V switching power supply circuit. AC 220V voltage through the step-down transformer, bridge rectifier and filter DC voltage Vi, i
L4960 by a monolithic switching power supply - schematic

nput L4960 O feet, under the action of L4960 internal soft-start circuit, the output voltage gradually increased. When the entire internal circuit is functioning normally, the output voltage in R3, R4 after sampling returned feet, internal error amplifier is compared with a 5.1V reference voltage to obtain the error voltage, then the magnitude of the error voltage to control the PWM comparator the pulse width, the power output stage after amplification and step-down output circuits (constituted by L, VD, C6 and C7), the output voltage Vo remains constant. L4960 7 feet get is power pulse modulation signal, which is high (L4960 internal switching power MOSFET) when, in addition to the load, as well as part of the energy stored in L and C6, C7, in which case freewheeling VD deadline. When power low-power pulse signal (switching power MOSFET is off) when, VD conduction, stored in L on through the loop formed by VD configured to load discharge, thereby maintaining the output voltage Vo constant. Figure (c) shows a current spreading circuit L4960. This circuit uses an external power transistor approach. The output current is extended to 10A. And over-current protection circuit is provided by the VT2, VT3 and R5, R6, R7, R8, R9 other components, when the output current is greater than 10A, the protection circuit, the potential of the L4960 foot clamp to 0V, closed PWM comparator terminates the output current.




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