PURPOSE: A slope compensating circuit of a boost converter is provided to improve space efficiency by decreasing the number of transistors without using an amplifier. CONSTITUTION: A capacitor(C21) and a resistor(Rs) are connected between a source terminal and a power terminal of second and third PMOS transistors(PM22,PM23) comprising a current mirror. A first PMOS transistor(PM21) is turned on by a gate pulse(GP) and controls the charging voltage of the capacitor. The drain terminals of the second and third PMOS transistors are connected to a current source and a slope current terminal.
