atx power core circuitry
the main atx power conversion circuit at the same power, but also "excited" circuit of double-barreled half-bridge PWM (pulse width modulation) controller uses the same tl494 control chip, but canceled the mains switch. drive pin
Just plug in the power cord, due to the cancellation of the mains switch on conversion circuit there will be +300 v DC voltage, while the auxiliary power supply voltage to tl494 work, ready to turn on the power.
atx power supply is characterized by the dead drive control tl494 chip 4 feet, when the pin voltage is +5 v tl494 9,11 feet output pulse, the two switches are off, the power is in standby state, no voltage output. 0v 4 feet, tl494 there trigger pulse to switch the power supply into the normal working state. Send tl494, all the way to the output of the auxiliary power supply and other output by the divider circuit "+5 vsb" and "ps-on" signal voltage of +5 v. , "+5 Vsb" output connected to atx motherboard power monitoring components "asked" +5 vsb ", as its operating voltage, the output can provide operating current of 10ma. Connected to the output of the power monitoring components "and" ps-on "in the trigger button switch (non-locking switch) is not pressed, ps-on" +5 v, it is connected to the positive phase input voltage comparator u1 of u1 negative phase input voltage is about 4.5v, so the input of the volt age comparator u1 +5 v sent the tl494 of "death-drive control pin" atx power in the standby. When the press motherboard power monitoring trigger button switch (mounted on the main chassis panel) ps-on goes low, the output of the voltage comparator u1 0v make atx host power on. Press the trigger button switch on the front panel, so that "ps-on" again becomes +5 v, which turn off the power. Also available procedures to control the output of the power monitoring components, so "ps-on" becomes +5 v automatically turn off the power. Win9x platform, issue the shutdown command, the atx power is automatically shut down. power point free down load
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