EC simulates LED parasitic capacitance such that the LED lights up when the current flows through the parasitic capacitor even if there is minimal actual voltage, whereas a true LED will only light up upon sufficient voltage being applied and current beginning flowing through the LED crystal rather than seeming to flow through it via its parasitic capacitance.
On the left are two circuits showing the LED unrealistically lighting up from current flowing through the parasitic capacitor. In the CCS example, the parasitic capacitor starts discharged but as it charges up from the current flowing it causes the LED to light up even when insufficient voltage is supplied and no current flows through the LED crystal itself. In the AC example, an ultra high frequency low voltage AC source causes some current to flow through the parasitic capacitor unrealistically causing the LED to light up even though the voltage only ever reaches up to 100mV, far too little to make current flow through the LED crystal itself.
On the right, the LED parasitic capacitor has been removed and an external capacitor added. The LED only lights up when current flows through the LED crystal itself and not when insufficient voltage is supplied and current is only flowing through the external capacitor.
