12v driver 24v h-bridge
Whether your circuit is good depends on whether your 12 volt power supplies are fully isolated or not. While good ones usually are, if you're going with cheap Chinese models there is no guarantee - and just because the supply carries a sticker proclaiming that it conforms to some standard or UL doesn't mean it's true.

I suggest you test your power supplies to make sure that if you stack them there is no unwanted current flowing.