Switching power supply with high efficiency, light weight, small size, wide voltage range of other advantages, since the mid-20th century, the advent of extremely rapid development in computer, communications, aerospace, office and household appliances has been widely applied, much to replace linear power supply potential. Improve the circuit integration is one of the pursuit of the switching power supply, switching power supply for small and medium is to realize monolithic integration. Integrated Switching Regulator refers to the control circuit, a power switch and protection circuits integrated on a single chip, but by switching the power switch integrated regulator constituted call it chip switching power supply. American PI's chip switching power supply series is its remarkable representative.
TOPSwitch-GX 250W switching power supply circuit design shown in Figure 1. DC voltage is applied to the primary side of the transformer by the TOPSwitch-GX drain D; frequency selection terminal F and limiting current setting terminal X and the source S is connected, the function of the two ends of no use, that does not set the limit from the outside current, internal automatic self-protection current setting ILIMIT, the switching frequency is 132K; optocoupler LTV817 connected to the control electrode and accept feedback signal in order to achieve internal integration of high-voltage power MOS duty cycle control; terminal L line detection through a 2MΩ the resistance and the positive terminal is connected to the DC high voltage input to achieve overvoltage, undervoltage line before the line voltage feed-forward voltage detection. Capacitor C1 is a high-frequency filter capacitor; transient voltage suppressors P6KE200 and ultrafast recovery diode clamp circuit BYV26C form, and in which the string into the RC snubber circuit (by R2, R3 and C6 form), so in addition to absorb some of the leakage inductance outside of energy, but also the voltage clamp at 200V, switching power supply can start or in the case of overload drain voltage TOPSwitch-GX integrated MOS transistor does not exceed 700V; secondary output high-frequency transformer T1 through MURl640CT after rectification and C9, C10 and C11 filter, then through the bead L1 and C12 filter out the switching noise, get the output voltage; VD4 and C14 constitute the soft-start circuitry.
Chip switching power supply with a single integrated, most simple peripheral circuit, optimum performance, can not achieve complete electrical frequency transformer isolation and other significant advantages, we design 290W Switching Power ideal choice.
