IX0689 power supply

Relevant key device information applied in this article: IX0689 D313 IX0689 power supply is widely used in TA two-chip computers of various domestic brands, and is one of the most commonly used power supplies in domestic machines. After the 300V DC voltage of the oscillation circuit is divided by R707 and R724, it is then added to pin (12) of N701 by C735 and L701. Pin (12) of IX0689 is the B pole of the internal switch tube, so the switch tube starts to conduct, and the current flows from It flows in from the C pole of (15) and flows out from the E pole of (13), passing through R714 and R710 to the hot ground. Pins (3) and (5) of T701 are positive feedback windings. When the switch is turned on, the polarity of the positive feedback voltage is (5) positive (3) negative. The voltage at pin (5) is added by V735, R713 and L701. to the (12) pin of N701, which further increases the current of the switch tube, and this cycle makes the switch tube quickly saturated. During the saturation period of the switch tube, the electrical energy is converted into magnetic energy in T701. As the current flowing out of the N701 (13) pin continues to increase, the voltage drop across R710 also continues to increase. When the voltage drop on R710 reaches about 1V, the switching tube begins to exit the saturated state. Once the switching tube exits saturation, the polarity of the induced voltage in each winding of T701 will all reverse. The polarity of the positive feedback winding (3) and (5) pins is (3) positive (5) negative. The negative voltage of (5) pin is passed through C713 , R713, and L701 are added to pin (12) of IX0689 to further reduce the current of the internal switch tube. This cycle makes the switch tube quickly cut off. During the cut-off period of the switching tube, the rectifier diodes of each secondary winding of the switching transformer are all turned on, converting the magnetic field energy stored in the switching transformer into electrical energy for each load of the machine. At the same time, the (1) and (6) windings of T701 It forms an oscillation circuit with C717, C718, R710 and C706. After oscillating for half a cycle, make pin (6) of T701 positive (pin 1) negative again, and couple it to the windings (3) and (5) to make the switch tube reset. conduction. During the voltage stabilization process, when the switching tube is turned off, the voltage on the windings of T701 (3) and (4) turns on the internal rectifier of pins IX0689 (2) and (3), and a DC voltage of about 27V is established on C711. The voltage is added to the internal sampling reference comparison circuit of pins (10) and (2) of IX0689. When the power grid is unstable or the 115V output fluctuates, the voltage on C711 also fluctuates. After internal sampling and comparison, it is finally output from pin (9), and the conduction period of the switch tube is automatically adjusted to stabilize the 115V output voltage. 1. When the switch tube is over-current, the voltage drop at both ends of R710 must also be large. This voltage is added to pins (7) and (8) of IX0689 through R712, causing the internal protection tube to conduct, and the switch tube is connected through pin (9). The B-pole current shunts, that is to say, the current of the switch tube is limited. 2. When the grid voltage increases, the current rise rate of the T701 primary winding will increase during the saturation period of the switch tube, thereby increasing the positive feedback voltage of the (3) and (5) windings of T701, and V736 will break down and conduct. , the internal tube of pin (7) of IX0689 is turned on, and the current of the B pole of the switch tube is shunted through pin (9), which protects the switch tube. 3. The 115V output terminal is connected to a voltage regulator tube V738. When the output voltage is greater than 130V, V738 breaks down, causing the switching power supply to stop oscillating.