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[SOLVED] Output Ripple Voltage in Buck Converter for Discontinuous Conduction Mode

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darkseid

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Dear All

How do we derive the equation for calculating the Ripple Voltage in Buck Converter for Discontinuous Conduction Mode. I believe we cant use the equation for continuous mode in discontinuous mode also.
 

If voltage ripple on ESR of output capacitor is neglected, the ripple can be calculated as:
(Ip-Io)/2*(Ip-Io)/Ip*(d1+d2)*Ts/C.
Here, Ip is the inductor peak current, Io is the load current, d1*Ts is the on time of main switch, d2*Ts is inductor current falling time, Ts is the switching period, C is the capacitance of output capacitor.
 
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Thanks Leo. The equation works great. Can you please tell me how to derive this equation (or the source of the equation). I tried deriving the equation by calculating the charge i.e. (area under the inductor ripple current graph considering it as a triangle wave) but I was not getting the right equation for discontinuous mode.

Again thanks for your reply
Darkseid
 

Tx1/(d1.Ts)=(Ip-Io)/Ip, Tx2/(d2.Ts)=(Ip-Io)/Ip,
ripple=(Ip-Io)/2*(Tx1+Tx2)/C
Then you got it.
44_1297071140.gif
 
Thanks Leo. Really appreciate it

regards
Darkseid
 

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