Current rating of the over current protection device must be ≤ 5 A. Maximum VA must be ≤ 250. Maximum marked output power rating of 5 A * Vmax. Maximum marked output current rating of 5 A. Dc voltages > 20 Vdc and ≤ 60 Vdc and substantially sinusoidal ac voltages > 20 VACrms and ≤ 30 VACrms. Goal is to find suitable values for the resistors and the right BJTs. 1) Q1: Assuming the power supply is working at its limit, on Q1 we will have a Ic=1.5A and Vce=Vcc-Vq2be=30-.7=29.3V. A suitable BJT able to support this values could be the D44H8. 2) Value of R1: The D44H8 has a worst case current gain of 10. To summarize the situation, the switching power supply designer is faced with a dilemma. He can design the current limit circuitry for high gain to obtain a sharp limiting knee, and large bandwidth One method frequently used to stabilize the supply is to narrowband the current limit amplifier. For the case where s d = (Eq. 3) 2 s a + s c Six countermeasures to limit startup surge current of SMPS. The inrush current of the switching power supply refers to the peak current flowing into the power supply equipment at the instant the power is turned on as shown in the below figure. Since the input filter capacitor of the charger quickly charges, the peak current is much larger than .

power supply with current limit