Open loop LED driving circuit
View Patent ↗The present invention discloses an open loop LED driving circuit, having a turn-on period and a turn-off period, the circuit comprising: a power stage, used to store a magnetic energy supplied from a voltage source during the turn-on period and deliver the magnetic energy to a set of LEDs during the turn-off period; and a control unit, having a turn-off period control terminal coupled to the voltage source, and a channel of which a first terminal is coupled to the power stage and a second terminal is coupled to a reference ground, wherein the channel is switched on at a time according to the voltage of the voltage source to determine the turn-off period.
1. An open loop LED driving circuit, having a turn-on period and a turn-off period, said circuit comprising:
a power stage, used to store a magnetic energy supplied from a voltage source during said turn-on period and deliver said magnetic energy to a set of LEDs during said turn-off period; and
a control unit, having a turn-off period control terminal coupled to said voltage source, and a channel of which a first terminal is coupled to said power stage and a second terminal is coupled to a reference ground, wherein said channel is switched on at a time according to the voltage of said voltage source to determine said turn-off period,
wherein said turn-off period control terminal is coupled to said voltage source via a resistive network so that the increment of said turn-off period caused by a voltage increment of said voltage source is determined by said resistive network.
2. The open loop LED driving circuit as claim 1 , wherein said power stage comprises an inductive element and a diode, wherein said diode is used to form a discharging current path for said inductive element during said turn-off period.
3. The open loop LED driving circuit as claim 1 , wherein said voltage source is rectified from an AC power.
4. The open loop LED driving circuit as claim 1 , wherein an end of said turn-off period occurs later as the voltage of said voltage source increases.
5. The open loop LED driving circuit as claim 1 , wherein said second terminal is coupled to said reference ground via a resistor.
6. An open loop LED driving circuit, having a turn-on period and a turn-off period, said circuit comprising:
a power stage, used to store a magnetic energy supplied from a voltage source during said turn-on period and deliver said magnetic energy to a set of LEDs during said turn-off period;
a control unit, having a turn-off period control terminal and a channel of which a first terminal is coupled to said power stage and a second terminal is coupled to a reference ground; and
a resistive network, coupled between said voltage source and said turn-off period control terminal,
wherein said channel is switched on at a time according to the voltage of said voltage source to determine said turn-off period in a way that the increment of said turn-off period caused by a voltage increment of said voltage source is determined by said resistive network.