LED capacitance discharge with limited current
View Patent ↗This invention relates to a driver ( 10 ′) for light emitting devices with an associated capacitance, comprising:—a first switch (S 2 ′) coupled to a first terminal ( 11 a ′) of a light emitting device ( 11 ′) included in a two dimensional array of light emitting devices, the first switch (S 2 ′) being coupled for allowing discharging of the associated capacitance ( 12 ′) of the light emitting device ( 11 ′) upon closing of the first switch (S 2 ′); and—a current limiting circuit ( 31 ) coupled to the first switch (S 2 ′) and to a reference voltage for discharging the associated capacitance ( 12 ′) with a limited current. Further, the current limiting circuit ( 31 ) comprises a first discharge circuit ( 50 ) and a second discharge circuit. As a result, the discharge current is controlled in an efficient manner during discharging of the associated capacitance ( 12 ′).
1. A driver for light emitting devices with an associated capacitance, comprising:
a first switch coupled to a first terminal of a light emitting device included in a two dimensional array of light emitting devices,
the first switch being coupled for allowing discharging of the associated capacitance of the light emitting device upon closing of the first switch; and
a current limiting circuit coupled to the first switch and to a reference voltage for discharging the associated capacitance with a limited current
wherein the current limiting circuit includes:
a first current path that includes a first discharging circuit having a positive resistance value that is coupled to the first switch,
the positive resistance value being selected to limit the current during discharging of the associated capacitance, and
a second current path including a second discharge circuit,
said second discharge circuit being coupled to the first switch and to the light emitting device, the second discharge circuit including;
a second resistor;
another discharge switch coupled in series with the second resistor; and
the series connection of the second resistor and the other switch being coupled between the light emitting device and the reference voltage.
2. The driver of claim 1 , wherein the other switch is arranged to be activated after the closing of the first switch.
3. The driver of claim 2 , wherein the other switch is arranged to be activated when the discharge current has reached a predetermined value, which value is lower than the value of the initial discharge current.