A buck-boost converter circuit includes a mode selection circuit that asserts a buck enable signal if an input voltage is higher than a lower threshold, and asserts a boost enable signal if the input voltage is lower than an upper threshold. A control circuit asserts a buck PWM signal upon a pulse in a buck clock and de-asserts the buck PWM signal if a buck ramp is higher than a buck control signal, and it keeps the buck PWM signal asserted if the buck enable signal is de-asserted. The control circuit asserts a boost PWM signal upon a pulse in a boost clock and de-asserts the boost PWM signal if a boost ramp is higher than a boost control signal, and it keeps the boost PWM signal de-asserted if the boost enable signal is de-asserted.