Buck-boost converter: switching circuit
* example of Section B.1.4

Vg 1 0 15V
Sq1 1 2 5 0 switch
D1 3 2 diode 
RL 2 4 0.1
L1 4 0 15uH ic=0
C1 3 0 50uF ic=0
R 3 0 20

Vc 5 0 pulse 
+(0 10V 0us 100ns 100ns 7.9us 10us) 

.model switch vswitch 
+(Ron=0.05 Roff=10meg Von=6V Voff=4V)
.model diode d (Is=1e-12)

.tran 1u 1.2m 0m uic
.probe

.end