Shown in Figure P12.36 is a “charge pump” circuit for a switched-mode power supply (with all transistors acting in the switched mode). A 555-timer chip drives the two inputs, which are the timer’s clock (CLK), and its inverse, clock-not . is low whenever CLK is high, and conversely. Assuming that the frequency of the clock is relatively high, determine the voltage across a high resistance load R.

Question

Answer 1

Analysis:



When CLK is high, the lower capacitor sees 12 V. When is high, the upper capacitor sees 12 V.

If the frequency is high, the load will see an almost constant voltage of 24 V.