Converter device, in particular an emergency lighting converter, for operating from an energy storage device, the converter device comprising a charger circuit configured to charge the energy storage device, a driver circuit including a switch, and the converter device further comprises a microcontroller circuit configured to control the charger circuit, and the microcontroller circuit is further configured to generate a switch drive signal (boost_drv) from a first signal (boost_cs) and a second signal (boost_zx) to control the switch in a mode in which the driver circuit is operated from the energy storage device, and that the driver circuit is configured to provide to an input of a first analogue comparator of the microcontroller circuit the first signal (boost_cs) as an analogue signal containing information on a discharge current of the energy storage device, and the driver circuit is configured to provide to an input of a second analogue comparator of the microcontroller circuit the second signal (boost_zx) as an analogue signal containing information when a current through an inductor of the driver circuit reaches zero, wherein the microcontroller circuit is configured to control the driver circuit in a boundary conduction mode to maintain a predetermined current value of the discharge current (I BATT) from the energy storage device characterized in that the microcontroller circuit is configured to provide to an inverting input of the first comparator circuit of the microcontroller circuit a first analogue reference signal (boost_CS_ref), wherein an analogue-digital converter of the microcontroller circuit is configured to convert the analogue first signal (boost_CS) into a digital first signal (boost_CS) and to provide the digital first signal (boost_CS) to a CS reference generator of the microcontroller circuit, and the CS reference generator is configured to use the digital first signal (boost_CS) to generate the digital first reference signal (boost_CS_ref) and to provide the digital first reference signal (boost_CS_ref) to a digital-analogue converter of the microcontroller circuit, and the digital-analogue converter of the microcontroller circuit is configured to convert the digital first reference signal (boos_CS_ref) into the analogue first reference signal (boos_CS_ref) and to provide the analogue first reference signal (boost_CS_ref) to the inverting input of the first comparator. a charger circuit configured to charge the energy storage device, a driver circuit including a switch, and the converter device further comprises a microcontroller circuit configured to control the charger circuit, and the microcontroller circuit is further configured to generate a switch drive signal (boost_drv) from a first signal (boost_cs) and a second signal (boost_zx) to control the switch in a mode in which the driver circuit is operated from the energy storage device, and that the driver circuit is configured to provide to an input of a first analogue comparator of the microcontroller circuit the first signal (boost_cs) as an analogue signal containing information on a discharge current of the energy storage device, and the driver circuit is configured to provide to an input of a second analogue comparator of the microcontroller circuit the second signal (boost_zx) as an analogue signal containing information when a current through an inductor of the driver circuit reaches zero, wherein the microcontroller circuit is configured to control the driver circuit in a boundary conduction mode to maintain a predetermined current value of the discharge current (I BATT) from the energy storage device characterized in that the microcontroller circuit is configured to control the driver circuit in a boundary conduction mode to maintain a predetermined current value of the discharge current (I BATT) from the energy storage device characterized in that the microcontroller circuit is configured to provide to an inverting input of the first comparator circuit of the microcontroller circuit a first analogue reference signal (boost_CS_ref), wherein an analogue-digital converter of the microcontroller circuit is configured to convert the analogue first signal (boost_CS) into a digital first signal (boost_CS) and to provide the digital first signal (boost_CS) to a CS reference generator of the microcontroller circuit, and the CS reference generator is configured to use the digital first signal (boost_CS) to generate the digital first reference signal (boost_CS_ref) and to provide the digital first reference signal (boost_CS_ref) to a digital-analogue converter of the microcontroller circuit, and the digital-analogue converter of the microcontroller circuit is configured to convert the digital first reference signal (boos_CS_ref) into the analogue first reference signal (boos_CS_ref) and to provide the analogue first reference signal (boost_CS_ref) to the inverting input of the first comparator.