SWITCHING POWER SUPPLY UNIT WITH CURRENT APPROXIMATING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To improve efficiency in switching power supply unit. SOLUTION: A switching power supply unit includes a switch M1 in which an input voltage Vin is applied, a coil L connected with the switch M1, and an output capacitor Cout connected with the output terminal. A dividing circuit 1 divides the output voltage Vout and generates a voltage feed-back signal Vfb. An air amplifier 2 generates a current instruction signal Iinst based on the voltage feed-back signal Vfb. A current approximating circuit 3 generates a coil current approximating value Iap by using a voltage feed-back signal Vfb. The switch M1 is controlled according to the current command signal Iinst and the coil current approximating value Iap.