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I am having trouble understanding the advantage of the following switched capacitor circuit that divides the input voltage by 2. enter image description here

When the switch is in its initial position, C1 and C2 are in series and form a simple capactive voltage divider. Heres my attempt to express this mathematically $$ v_{in} = \frac{Q}{C_{tot}}, \qquad v_{out}=\frac{Q}{C_1} \\\\ v_{out}=\frac{C_{tot}}{C_1}v_{in} \\\\ v_{out}=\frac{C_2}{C_1+C_2}v_{in} $$ Assuming that C1 and C2 are equal we then get $$v_{out}=\frac{v_{in}}{2}$$ .

Now if the switch is in the second position the two charged capacitors are noe connected in parallel. Each of the two capacitors holds the charge Q which means that the output voltage across the two parallel capacitors is now $$ v_{out} = \frac{Q_{tot}}{C_{tot}}=\frac{2Q}{C_1+C_2} $$ Assuming that C1 and C2 are equal this again results in $$ v_{out}=\frac{v_{in}}{2} $$ Now heres my question: Assuming that my math is correct, whats the advantage of using this circuit instead of simply using a capacitive voltage divider (or even one with simple resistors)?

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Assuming that my math is correct, whats the advantage of using this circuit instead of simply using a capacitive voltage divider (or even one with simple resistors)?

If you have a load on the output capacitor (as you would with this type of circuit), charge is continuously being removed hence, the complexity of the circuit is to overcome that problem. In other words, the switches moving back and forth will keep the output at nominally Vin/2 even under serious load currents.

Of course you have to design the circuit so that output ripple voltage remains to an acceptable level under extreme loads but, that is largely down to increasing the switch toggle rate into the hundreds of kHz.

A simple capacitive or resistive divider cannot really cope with anything but extremely light loading.

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  • \$\begingroup\$ I see, so by continously loading my cap I'm circumventing that effect? \$\endgroup\$ Commented Jun 4, 2024 at 12:55
  • \$\begingroup\$ By continually recharging the circuit (due to the switching action) you are replenishing the charge in the output capacitor against problems of load current @Axodarap \$\endgroup\$ Commented Jun 4, 2024 at 13:16

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