Integrated device and method for driving lighting loads with a brightness compensation
AssigneesSTMicroelectronics S.r.l., Stmicroelectronics Application GmbH
InventorsManuel Gaertner, Sergio Lecce, Giovanni Luca Torrisi
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Abstract
An integrated device for driving a lighting load, such as a LED, has a first memory element, configured to store a nominal duty-cycle at a nominal supply voltage. An actual voltage acquisition element is configured to detect an actual supply voltage. A processing unit is coupled to the first memory element and to the actual voltage acquisition element and configured to calculate a voltage compensated duty-cycle. A driver unit is coupled to the processing unit and is configured to be supplied according to the voltage compensated duty-cycle.
Claims24
An integrated device for driving a lighting load, the integrated device comprising:
- a first memory element configured to store a nominal duty-cycle at a nominal supply voltage;
- an actual voltage acquisition element configured to detect an actual supply voltage;
- a processing unit coupled to the first memory element and to the actual voltage acquisition element, the processing unit configured to calculate a voltage compensated duty-cycle;
- a driver unit coupled to the processing unit and configured to be supplied according to the voltage compensated duty-cycle;
- a second memory element coupled to the processing unit and configured to store the voltage compensated duty-cycle;
- and
- a third memory element coupled to the processing unit, the third memory element configured to store a load characteristic value;
- wherein the processing unit is configured to calculate a voltage compensated duty-cycle DCC according to equation:
- DC
- C
- =
- V
- th
- -
- V
- LED
- V
- B
- -
- V
- LED
-
- DC
- n
- wherein DCN is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is the load characteristic value, and VB is the actual supply voltage.
An integrated device for driving a lighting load, the integrated device comprising:
- a supply voltage node;
- an analog-to-digital converter with an analog input coupled to the supply voltage node;
- a nominal duty cycle register that stores a nominal duty-cycle at a nominal supply voltage;
- a hardwired logic circuit coupled to a digital output of the analog-to-digital converter and to the nominal duty cycle register, the hardwired logic circuit configured to implement a state machine to calculate a voltage compensated duty-cycle;
- a characteristic register coupled to the hardwired logic circuit and configured to store a load voltage drop;
- a compensated duty-cycle register coupled to the hardwired logic circuit to store the voltage compensated duty-cycle;
- a driver element coupled to the supply voltage node and the compensated duty-cycle register;
- and
- a load terminal configured to be connected to a lighting load;
- wherein the integrated device is configured to calculate the voltage compensated duty-cycle DCC according to equation:
- DC
- C
- =
- V
- th
- -
- V
- LED
- V
- B
- -
- V
- LED
-
- DC
- n
- wherein DCN is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is a load characteristic value, and VB is an actual supply voltage.
An LED driver comprising:
- a first output terminal configured to be coupled to a first LED;
- a first driver circuit coupled to the first output terminal;
- and
- a brightness control device configured to:
- receive a nominal duty-cycle at a nominal supply voltage,
- receive an actual supply voltage,
- calculate a voltage compensated duty-cycle based on the nominal duty-cycle and the actual supply voltage, and
- control switching of a voltage of the first output terminal with pulse width modulation based on the voltage compensated duty-cycle, wherein calculating the voltage compensated duty-cycle comprises calculating the voltage compensated duty-cycle according to equation:
- D
-
-
- C
- C
- =
- V
- th
- -
- V
- LED
- V
- B
- -
- V
- LED
-
-
- D
-
-
- C
- n
- ,
- wherein DCn is the nominal duty-cycle, VTH is the nominal supply voltage, VLED is a load characteristic value, and VB is the actual supply voltage.
Dependencies are inferred from the claim text.