Comparators update when power is shut

I was building a contraption that i had testfor commands in. I powered it and the comparator was turned on. Behind the comparator i had a command that used setblock to set the command block to the same command(Just so the comparator should turn off.) But when the power that went into the command block got unpowered, the comparator turned on for some reason. I know this is proberly because it was a different command block. But it should only power the command block WHEN it gets powered.