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Single chip switching power supply design
Source: | Author:pmodcd779 | Published time: 2014-10-11 | 1828 Views | Share:
Switching power supply has high efficiency, light weight, small size, wide voltage range and other prominent advantages, since the mid-20th century, the development of extremely rapid, in the computer, communications, aerospace, office and household appliances, etc., has been widely used, great potential to replace the linear voltage regulator. To improve the integration of circuit is one of the pursuits of switching power supply. Switch integrated voltage regulator refers to the integration of the control circuit, power switch tube and protection circuit in a chip, and the switch power supply composed by the switch integrated voltage regulator is called the single-chip switch power supply. American PI company's single - chip switching power supply series is its prominent representative.

TOPSwitch -- the 250W switching power supply circuit designed by GX is shown in figure 1. The dc voltage is added to the drain electrode D of TOPSwitch -- GX through the primary side of the transformer; The frequency selection terminal F and the limit current setting terminal X are connected with the source electrode S, so the functions of both ends are useless. In other words, the limit current is not set externally, and the internal self-protection current ILIMIT is automatically set. The switching working frequency is 132K. The control pole is connected with the optical coupling LTV817 and receives feedback signals to control the duty ratio of the internally integrated high-voltage power MOS tube. Line detection side through a 2 L m Ω resistance and dc input connected to the positive side of high in order to realize the over-voltage, owe line-to-line voltage feedforward line detection. Capacitor C1 is the high-frequency filtering capacitor; Transient voltage suppressor P6KE200 BYV26C constitute and super fast recovery diode clamping circuit, and the RC absorption circuit in series with the (R2, R3 and C6), so in addition to being able to absorb the energy in the leakage inductance of the part, also can be in 200 v voltage clamp, can make the switch power supply in the case of a start or overload TOPSwitch - GX internal integration MOS tube drain voltage not over 700 v. The secondary output of high-frequency transformer T1 is filtered by MURl640CT rectifier and C9, C10 and C11, and then filtered by magnetic beads L1 and C12 to get the output voltage. VD4 and C14 constitute soft - start circuit.

The single chip switching power supply has the significant advantages of single chip integration, the simplest peripheral circuit, the best performance index, and the ability to achieve complete isolation with no power frequency transformer, which is our ideal choice for the design of switching power supply below 290W.