First, 5VSB, PS-ON, PW-OK control signal
] 5VSB is a power supply for host systems in ATX standby state, and the working power supply of open and closing automatic management and remote wake-up communication contact related circuitry, in standby and controlled start-up state, its output voltage is 5V high, use The purple line is taken from the ATX plug (Figure 1). PS-ON is a control signal for the host to turn off the power or network computer, the power supply of the power supply, the different models of the ATX switching power supply, the voltage value is 3V, 3.6V, and 4.6V vary. When pressing the Power switch of the host panel or realizes the network wake up remote boot, the control startup is grounded by the electronic switch of the motherboard, using the green line from the ATX plug 14 pin. PW-OK is the output signal for the main panel to detect the power supply, using the gray line by the ATX plug
8 foot is quoted, the standby state is zero level, and the controlled start voltage output is stable to 5V high level.
Offline charging detection ATX power supply, first measuring PS-ON and PW-OK signals in standby mode, the former is high, the latter is low, the plug 9 pin output 5VSB, no other Voltage. The second is to wake up the ATX switching power unit, use a wire to put the ATX plug 14 foot PS-ON signal, and short in one foot in any place end (3, 5, 7, 13, 15, 16, 17), This step is the key to detect, wake up the ATX power from the standby state to start a controlled state. At this time, the PS-ON signal is low, the PW-OK, 5VSB signal is high, ATX plug 3.3V, ± 5V, ± 12V has output, switching power supply fan rotation. The above operation can also be used as a method of optional an ATX switching power supply offline.
Second, the working principle of the control circuit
ATX switching power supply, circuitry according to its composition function into: AC input rectification filter circuit, pulse semi-bridge power conversion circuit, auxiliary power supply circuit, pulse width modulation control circuit, PS-ON and PW-OK generation circuit, automatic stability and protection Control circuit, multi-channel DC voltage regulator output circuit. Please refer to Figure 2.
1. Auxiliary power supply circuit
As long as there is an exchange of electric input, the ATX switching power supply has been working regardless of whether it is turned on, and its auxiliary power supply has been working, providing a working voltage for the switching power control circuit. The city is electrically rectified, filtered, outputting about 300V DC pulsation voltage, all the way to R72, R76 to the auxiliary power switch tube Q15 base, and the primary winding of the T3 switch transformer is added to the Q15 collector, so that Q15 is turned on. T3 feedback winding induction potential (upper negative negative) is added to Q15 base by positive feedback branch C44, R74, so that Q15 is saturated. The feedback current is charged with the capacitance C44 by R74, R78, Q15 B, E pole equivalent resistance, as the C44 charging voltage increases, flowing through the Q15 base current gradually decrease, T3 feedback winding sensing potential reverse phase (upper negative ), Is superimposed to the C44 voltage to the Q15 base, the Q15 base potential is grease, and the switch tube is rapidly closed.
When Q15 is cut off, ZD6, D30, C41, R70 forms a Q15 base negative bias cutoff circuit. The positive end of the feedback winding induction potential is formed by the C41, R70, D41 to the inductive potential negative end, and the C41 negative electrode negative voltage, Q15 base potential due to D30, ZD6 is turned on, is compared to C41 negative voltage. 6.8 V (diode pressure drop and voltage regulator value) negative potential. At the same time, the charging voltage of the feedback branch C44 is transmitted by the T3 feedback windings, R78, Q15 B, E pole equivalent resistance, and R74 form a discharge circuit. As the C41 charging current gradually decreases, the UB potential rises. When the UB potential is increased to the B, the E-pole is turned on again, the Q15 is turned on again, and the oscillation of the next cycle is entered.
During the Q15 saturation, the induction potential of the T3 secondary winding output is negative, the rectifier tube is turned off, and the conduction current flowing through the primary winding is stored in the T3 auxiliary power supply transformer in the form of magnetic energy. When Q15 is cut off by saturate, the secondary winding of the induction potential of the secondary winding is positive, and the magnetic energy stored in T3 is converted to the electric energy to be rectified by the BD5, BD6. Where the BD5 rectifier output voltage is supplied with Q16 three-end regulator 7805, Q16 outputs 5VSB. If the voltage is lost, the motherboard does not automatically wake up the ATX power supply. The BD6 rectified output voltage supply IC1 pulse width modulated TL494 12 foot power input, the chip 14 pin output voltage regulator 5V, provides an ATX switching power supply control circuit all components of the operating voltage. 2. PS-ON and PW-OK, pulse width modulation circuit
When the PS-ON signal controls the 4 foot of the IC1, when standby, the electronic switch of the motherboard opening and closing control circuit is open, the PS-ON signal is 3.6V, the UR potential of the IC10 precision regulator circuit WL431 rises, UK potential The decrease, Q7 is turned on, and the voltage regulator 5V is fed into the 4 pin of IC1 through Q7 E, C poles, R80, D25, and D40. When the 4 foot voltage exceeds 3V, the modulation pulse width output of the 8, 11 pin is blocked, so that T2 Push the transformer, the T1 main power switch transformer is stopped, and the output voltage of 3.3V, ± 5V, ± 12V is stopped. After the controlled startup, the PS-ON signal is grounded by the electronic switch of the motherboard, and the UR of the IC10 is zero potential. The UK potential is rised to 5V, Q7 is closed, and the C is extremely zero potential, and the 4 foot of IC1 is low. Allow 8, 11 pin output pulse width modulation signals. The output mode of the IC1 control terminal 13 pin is voltageable 5V, the pulse width modulator is a pulse width modulation control signal of the 8, 11 pin output phase difference 180 degrees, the output frequency is 5, 6 foot external connections of IC1 Half of the oscillation frequency of the constant reactor element, the C-pole connected T2 of Q3, Q4, push the excitation oscillation of the transformer primary winding, T2 secondary oscillating generated induction potential acting on the T1 main power switch transformer once winding, two The induction potential of the second winding forms 3.3V, ± 5V, ± 12V output voltage.
The D17, D18, and C17 connected to the push tube Q3, Q4 emitter are used to raise Q3, Q4 emitter level, so that Q3, Q4 base is low, and the low level pulse can be reliably turned off. The C31 is used to energize the 8, 11 foot output pulse of the IC1, and the ATX power supply is generated. Since the voltage of the C31 cannot be mutated, the 4 foot of IC1 appears high, and the 8, 11 foot is free of drive pulse output. As the charging of C31, the start of IC1 is controlled by PS-ON signal.
The PW-OK generating circuit consists of IC5 voltage comparator LM393, Q21, C60, and its peripheral components. When the standby, the feedback control terminal of IC1 is low, Q21 saturation is turned on. The 3 foot terminal of IC5 inputs low potential, less than 2 foot negative end input, 1 foot low potential, PW-OK direction The host output zero level power self-test signal, the host stops work in a leisure state. The 3 foot potential of IC1 after controlled startup, Q21 is turned on by saturated into the amplification state, and the E-pole potential is established by R104. With the C604, as C60 is gradually performed, IC5 3 foot control level Gradually rise, once the 3 foot potential of IC5 is greater than 2 pin fixed partial pressure ratio, the hysteresis comparator with positively feedback, and the pin outputs a high level PW-OK signal. This signal corresponds to the PG signal of the AT power supply, and then delayed by several hundred milliseconds after the switching power supply output voltage is stabilized by zero level to 5V, the host detects the PW-OK power supply to start the system. When the main unit is powered down or when the user is turned off, the ATX switching power supply 5V output voltage must fall, and the feedback signal whose amplitude becomes smaller is sent to the voltage sampling amplifier of the IC1 component. It will cause the following chain reaction: so that the feedback control terminal 3 foot potential of the IC1 is lowered, and the base of the Q21 is coupled to the base of the Q21, as the Q21 base potential is lowered, once the E, the B pole potential of Q21 reaches 0.7V, Q21 saturation Tong, the 3 foot potential of IC5 is rapidly declining. When the 3 foot potential is less than 2 pin fixed voltage level, the output terminal of IC5 will immediately jump to zero levels from 5V, and the PW-OK output signal is more The ATX switching power supply 5V output voltage disappears in advance, inform the host trigger system automatically shuts down before the power is powered off, prevent sudden power-off the hard disk magnetic head from moving to the land area and scratches the hard disk.
3. Automatic regulator control circuit
pro 1, 2 foot voltample amplifier positive, negative input, sampling resistors R31, R32, R33 constitute 5V, 12V automatic voltage regulator circuit. When the output voltage is increased ( 5V or 12V), the R31 acquires the sampling voltage to the 1 pin of the sampling voltage to the IC1, and the output error voltage and the oscillating pulse of the zipper wave generating circuit in the chip are in the PWM comparator. The comparison is amplified, so that the 8, 11 foot output pulse width is reduced, and the output voltage falls into the standard value, and the opposite is reversed, so that the switching power supply output voltage is stabilized. IC1's current sample amplifier negative end input 15 foot recessed voltage 5V, positive input 16 foot ground, the current sample amplifier is not used in the pulse width modulation control circuit.
