The one thing that you can be relatively sure of is that the input components (diodes, switching transistors, or whatever) will be carrying twice the current to get the same power on the output side going to the LEDs. Only the manufacturer knows whether they can handle that double current or not. Long term thermal damage to semiconductors is quite possible even though they may appear initially to work fine.
OP did feed the switching transformer with 240 volts which is lower than nameplate rating of 347 volt minimum.
By OHM's Law, we could infer that current will go up because of low input voltage. . . theoretically correct.
Most newer design switching power supplies have both constant voltage (CV) and constant current
output capability. Depending on the condition of the input voltage, the TTL (transistor Logic) could be deployed in the circuit to utilize either CV or CC in order to work in a closed loop control of the switching transistor.
The output is constantly monitored for any changes outside the design premise. If for instance there is an anomaly that will cause instability of the output, either CV or CC will selectively (automatically) switch to proper mode in order to correct the problem.
The low voltage (240 Volts) instead of 347 v that OP is trying (or had already tried) evidently worked.
The reason that it works is; the switching transistor enables the charging capacitor to charge and discharge due to the opening and closing of the switch. Charging when open, discharging when closed.
This charging/discharging routine is what raises the voltage to almost in parity with the needs of the electronic components.
Since most switching power supplies are designed for universal use, the wide range certainly make economic sense.
Some countries operate at 250 volts. The 347 v volt name plate rating is measured at the emitter and base junction of the power transistor. So, when fed from a 240 volt source the peak reading would be 339.0 volts.
The 347 v volt nameplate is the theoretical PP (250 volt X Sq rt of 2) which is roughly 353 v peak.
Bottom line is, it will work but at a reduced luminescent. You have to go through the power supply and NOT hook the LEDs directly to a 240v wall plug. This way you still get the advantage of a modulated power source.
One way to check if it operates in CV mode is; if at this low input voltage the LEDs flicker.. . .usually when in constant current mode flickering is unnoticeable because of the rapid response in controlling the output.
