Inductorless Switching Regulator Boosts Input Voltage
Figure 1. Substituting the diode-capacitor network shown for an inductor allows this switching-regulator IC to deliver 2mA at comparable line and load regulation, with somewhat reduced efficiency.
Feedback from the R1/R2 voltage divider enables IC1 to set the regulated-output level. (As shown, the circuit derives 12V from a 5-to-12V input and produces as much as 2mA of output current.) Adding a non-inverting MOS drivers (Figure 2) boosts the available output current to 20mA.
Figure 2. Introducing a MOS driver (IC2) enables the Figure 1 circuit to deliver as much as 20mA.
No-load quiescent current is roughly proportional to VIN for both circuits. Both draw 130µA at VIN= 4.5V. At 12V, the Figure 1 circuit draws 225µA and the Figure 2 circuit draws 380µA. Full-load efficiency is highest for low VIN in both cases: Efficiencies range from 74.4% at 4.5V to 36.8% at 12V (Figure 1), and from 72.4% at 4.5V to 43.9% at 12V (Figure 2).