Regardless of what electronic design projects, first of all have a stable and reliable power supply as a support, the power load capacity, ripple, fluctuation noise, directly related to the circuit performance is good or bad.

In order to produce a power enough, excellent performance of the switching power supply, after access to information, PI's TOP223 chip and its application circuit has become our main choice.

First of all, to a grand introduction to our protagonist - PT223Y.

D pin (3 feet) with power switch N-channel MOSFET drain, switching current limiting comparator, starting with high voltage current source Ih.b and so on. C pin (1 foot) is the only control end. Which is to control the duty cycle to change the error amplifier and feedback current input, the internal parallel regulator adjustment to provide normal operation within the bias current, but also overvoltage protection "latch off" trigger input, also used as a high road compensation External capacitor connection point.

C pin (1 pin) Normal minimum bias current of about 2.5mA, as small as 1.2mA will enter the automatic restart standby mode, the red up to 45mA, so that overvoltage protection work, so that the switch into the repeated action (automatic Restart) mode, and the TOP switch N-MOSFET cut-off (off) protection.

C pin (1 pin) voltage down to the boot reset threshold (about 3.3V ± 1V) below, and then to the normal boot state. S pin (2 feet) connected to the power switch N-channel MOSFET source, but also the switching current return side, the internal circuit and the primary circuit common ground or reference point.

A1 for overvoltage protection Overwrite "latch off", reset by the power-on reset circuit.

A2 is used for current limiting latch and leading edge blank and minimum on delay control. The clock pulse CK starts from each cycle and is reset by PWM comparator output during normal operation.

The internal oscillation clock generator 100 kHz clock pulse CK also generates a PWM sawtooth wave SA and a maximum duty ratio control signal DM.

Its functions include power MOSEFT, pulse width modulator, high voltage start circuit parts, loop compensation and fault automatic protection circuit.

TOP223 only need to cooperate with a small amount of external components, with the use of optocoupler, you can quickly design a good enough performance parameters of high power switching power supply.

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