Unwanted spikes in Simulink with Matlab R2013a

I am trying a simulation of a power electronics circuit using simulink of Matlab R2013a. I am able to get correct output but the output contains many unwanted spikes. When I zoom into one of the spikes to the maximum possible limit then also the spike shows like just as a line. The spike is not getting enlarged when I zoom to the maximum level that is possible in scope. I have also checked by changing the "Model Configuration Parameters" but it didn't help. But When I tried the same program with Matlab R2010a then the output is perfect with no spike at all. So I whats the difference between the two version of Matlab and what settings has to be changed to make R2013a to get a spike free output.

[Luciano Alves]

Try to use "enable use of ideal switching devices": go to Powergui Block --> Configure Parameters --> Simulation type (continuous) and enable use of ideal switching devices.