An inverter LED bulb is essentially an emergency LED bulb. Actually, such products are somewhat confusing because there is no inversion process (DC to AC, or vice versa) involved in the circuits where these are used.
The technology used in these bulbs enables them to automatically turn on the LED light during a power cut and automatically charge the internal battery when AC mains is available. Basically, inverter LED bulb is a two-in-one bulb. That is, when there is AC mains power, it works as a normal light bulb but when there is a power cut, it works as an emergency light bulb.
Most inverter LED bulbs have lithium-ion batteries that provide three- to four-hour backup. These internal batteries require three to four hours of charging time to fully charge.
Thereafter the charging voltage is automatically cut to protect the battery from getting overcharged. The bulb is designed to charge the internal battery even during normal operation.
However, most inverter LED bulbs come with charge-only mode. This mode is used to charge the internal battery with the LED bulb off.
When AC mains power goes off, this inverter bulb automatically switches on to act as a DC emergency light. It can be switched off when not required.
The features of an inverter LED bulb include fully automatic control, low power consumption, and high efficiency. Since it has internal backup power source and electronic control circuit, it can detect the switch state even during power cut.