Two-switch buck-boost converter

PURPOSE: To obtain a controller for a two-switch buck-boost converter which controls one switch only in one operation, without using a level shift circuit by a method, wherein an analog error signal and an inverse signal of the analog error signal are compared with a voltage which is equal to the voltage fluctuation limit of a timing lamp signal. CONSTITUTION: A triangular wave oscillator 10 outputs a voltage lamp signal (timing lamp signal) with a constant frequency between 2 voltages, applied to input terminals B and C. An error signal is applied to a terminal A, and the voltage lamp signal is compared with the error signal by a 1st comparator 12. On the other hand, the voltage lamp signal is compared with the output of an operational amplifier 16 by a 2nd comparator 14. The operational amplifier 16 is constructed so as to obtain the negative gain of the error signal applied to the terminal A, and the positive input of the operational amplifier 16 is controlled by a same reference as the reference of the control of the peak voltage (voltage applied to the terminal B) of the voltage lamp signal. As a result of this, a level shift circuit can be omitted. COPYRIGHT: (C)1995,JPO