Soft start function of power adapter TOP Switch-GX series

　　Compared with the TOP Switch-FX series, the GX series has a new soft start function. The soft start function enables the TOP Switch GX series to start working after being powered on, and the internal soft start circuit causes the maximum duty cycle to increase linearly from 0 to 10ms. To 78%. At the same time, the current limit value also linearly increases from 85% of the set value to 100%. In the automatic restart mode, each time the automatic restart, the soft-start process is repeated, eliminating the need for the output capacitor during the startup process. The power stress and output voltage overshoot of the TOPSwitch and the output rectifier diode caused by the charging of the TOPSwitch; due to the soft-start function, the TOP Switch series can be used in the forward converter topology recommended in the data, and the TOP Switch-GX series without soft-start The formed forward converter cannot be used in AC220V power adapter.

　　Peripheral current limit function

　　The function of accurately setting the current limit value of the external circuit can use a resistor to accurately set the current limit value to any value between 30% and 100% of the maximum current limit value, as shown in Figure 15-18, which can make the GX series "derate" "At the same time, by accurately setting the current limit value, the maximum output power of the power adapter is limited to protect other components in the TOP Switch power adapter and the external load from the impact of excessive overload current to improve reliability. The current value can be limited. This is achieved by changing the external current limiting resistor at the X end, as shown in Figure 15-19. When the external resistance is less than 6k, the current limit value does not change. When the external resistance is 6k0, the current limit value gradually decreases. Figure 1518, Figure 15-19 The current limit value is based on T0244G, and other models can be converted by the scale factor in the figure. The figure also shows that as the current limit value decreases, the rise rate of the main switch's turn-on current also decreases. In this way, the electromagnetic interference of the switching process of the TOP Switch-GX during derating can also be reduced.

　　The output power given in the data sheet of POWER Int

　　Compared with the TOP Switch series, the GX series has the following advantages: the minimum on-resistance is further reduced, the maximum current limit value is increased, and the external circuit is accurately set to set the current limit value, soft start, frequency jitter, over/under voltage protection, external setting Functions such as working frequency and frequency reduction at light load.

　　The on-resistance is reduced, the on-resistance of ToP227 with the smallest on-resistance in the TOP SwitchⅡ series is 50 at a junction temperature of 100℃, and the smallest on-resistance in the GX series is 2.15Ω (T0P249). The on-resistance is reduced When the output power of the TOP Switch increases, the amount of heat generated decreases.

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