Cheap PSUs can always be risky, because they don't have the safety features of better ones, let alone whether they will perform well under load (ie keeping steady power levels).
What's likely happening is that your PSU has overdraw protection, and when the graphics card is asking for more power than the PSU can supply, the PSU is shutting down. You don't want to be running any system where those protection features are constantly being triggered, as it means you're pushing the PSU too far. Sooner or later, the protection circuits may fail and you'll get a surge into your motherboard.
It's like trying to pull too much power through a plug socket. Things get hot, wires melt, breakers pop, fuses blow. The safety features work, but you don't want to be relying on them, or ignoring the source of the problem that keeps activating the safety features.
What's likely happening is that your PSU has overdraw protection, and when the graphics card is asking for more power than the PSU can supply, the PSU is shutting down. You don't want to be running any system where those protection features are constantly being triggered, as it means you're pushing the PSU too far. Sooner or later, the protection circuits may fail and you'll get a surge into your motherboard.
It's like trying to pull too much power through a plug socket. Things get hot, wires melt, breakers pop, fuses blow. The safety features work, but you don't want to be relying on them, or ignoring the source of the problem that keeps activating the safety features.