Internal cubic block diagram of switching power supply integrated circuit 5M0269R

Internal cubic block diagram of switching power supply integrated circuit 5M0269R

5M02659R is a low-power offline switching power supply integrated circuit , and its internal circuit block diagram is shown in the figure.
    1. The switching oscillation circuit AC
    220 V mains power is rectified and filtered to generate a DC voltage of about 300 V. The DC voltage passes through the switching transformer Tl01
@~④ windings and is added to the ①, @, ⑦, @ pins of IC101. The other way passes through the starting resistor Rl01 to charge C105 and C106. As the charging
progresses - the Iclol@ pin voltage rises. When the voltage rises to 14 V above the threshold voltage, the internal functional circuits start to work. At this time, the switch
tube enters the switching state. After the circuit starts oscillating, as long as the @ pin voltage is not lower than 8.2 V, the circuit will be locked in the normal working state. . After the power supply is turned on.
(The high-frequency induced pulse voltage generated by the switching transformer @~① winding is instead supplied with a DC voltage of about 16 V after being adjusted by D106, current limiting by R103 and filtered by c105 and C106
to meet the requirements of IC101 during normal operation. Power supply requirements.
    After the power supply is working, the pulse voltage on each secondary winding is outputted through its own rectifier and filter circuit respectively -24 V, F+, F- voltage to power the
fluorescent display screen; +12 V, -12 V for the main board The +5 V DC voltage supplies power to the mainboard servo drive circuit and various chips
. The +5 V voltage also generates a +3.3 V voltage through the mainboard voltage stabilizing circuit to supply power to the decompression chip.
    2. The voltage stabilizing circuit
    should be powered by some kind of When the output voltage rises due to reasons, the +5 V output voltage will also rise. The voltage divided by the sampling resistors R1()8 and R107 and then
added to the IC103 control terminal pin ① will also rise accordingly, causing the voltage flowing through ICl( }3 As the current of sundial pin ⑤ increases, the light emitting diode inside IC102
increases, and the voltage of pin ④ decreases. After being processed by the internal circuit of ICI01, the conduction time of the switch tube becomes shorter, the energy storage of the switching transformer
decreases, and the output The voltage decreases to achieve the purpose of stabilizing the output voltage. If the output voltage decreases, the voltage stabilization control process is opposite to the above process.
    3. Protection circuit
    (1) Overvoltage protection
    When the grid voltage rises or the voltage stabilization control circuit loses control, the output voltage When it is too high, the voltage on the ②~① windings of the switching transformer will also
increase accordingly. After being rectified by D106 and filtered by C105, the voltage added to the 1C101@ pin will also increase accordingly. When the voltage amplitude of the ③ pin exceeds the threshold voltage of
25 V, The internal overvoltage protection circuit of ICIOI starts and the switch tube is turned off.
    (2) Undervoltage protection
    When the input AC voltage is too low, the voltage amplitude on the switching transformer @~① winding will also decrease accordingly. After being rectified by DJ 06 and
filtered by C105 The voltage applied to pin ③ of 1C101 also decreases accordingly. When the voltage of pin ③ is lower than 8.2 V, the internal undervoltage protection circuit of IC101 operates and the switch
tube is turned off.
    (3) Overload protection
    ICI01 has an internal overload (overcurrent) protection circuit. If the peak current of the switch tube exceeds 0.9A due to overload or other reasons
, the overload protection circuit will operate and the switch tube will be cut off.
    (4) Over-ripe protection
    IC101 has an overheat protection circuit integrated inside it. When the internal tube of IC101 is overheated When the temperature exceeds 1600C, the overheat protection circuit starts, and the switch tube
is cut off and closed to achieve the purpose of overheat protection. In addition, the power supply also has a drain spike of the switch tube composed of C103, R102, C104, and D105 indirectly from the winding of
    the switching transformer Tl01⑥~④ Voltage absorption circuit to protect the switching tube.