VOLTAGE CONVERTER FOR SUPPLYING A SEMICONDUCTOR LIGHT SOURCE, IN PARTICULAR A LED LAMP

• US 20110006691A1
• Filed: 07/09/2010
• Published: 01/13/2011
• Est. Priority Date: 07/10/2009
• Status: Active Grant

• Current Assignee: Stmicroelectronics Design And Application S.R.O. (STMicroelectronics NV)
• Original Assignee: Stmicroelectronics Design And Application S.R.O. (STMicroelectronics NV)
• Inventors: BLAHA, Karel, MILSIMER, Jan
• Granted Patent: US 8,928,252 B2
• Time in Patent Office: Days
• US Class Current: 315/185.R
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

An embodiment of the invention relates to a voltage converter for supplying a semiconductor light source and having at least an input terminal connected to a power supply reference, namely an AC mains voltage reference, and an output terminal providing a current signal to said semiconductor light source, the converter being also connected to a voltage reference and comprising at least a step-down block inserted between a switching node and to the output terminal and connected to the voltage reference and an input block connected to the input terminal, as well as to a first input node and to a first output node of a control circuit, in turn connected to the switching node and to the voltage reference. The input block is a pre-regulator input block and comprises at least a switching component connected to the input terminal and to a capacitive block, in turn inserted between a second input node of the control circuit and the voltage reference, such a switching component having a control terminal connected to the first output node.

Claims

1. Voltage converter for supplying a semiconductor light source and having at least an input terminal connected to a power supply reference, namely an AC mains voltage reference, and an output terminal providing a current signal to said semiconductor light source, the converter being also connected to a voltage reference and comprising at least a step-down block inserted between a switching node and to said output terminal and connected to said voltage reference and an input block connected to said input terminal, as well as to a first input node and to a first output node of a control circuit, in turn connected to said switching node and to said voltage reference, wherein said input block is a pre-regulator input block and comprises at least a switching component connected to said input terminal and to a capacitive block, in turn inserted between a second input node of said control circuit and said voltage reference, said switching component having a control terminal connected to said first output node.

2. Voltage converter according to claim 1, wherein said control circuit further comprises a supplying pre-regulation block which is directly connected to a third input node and is also connected to said first input node by means of a regulation diode, said first input node being also connected to said voltage reference by means of a regulation resistor, said supplying pre-regulation block stabilizing a voltage value at said first input node when a voltage value on said second input node coming from said pre-regulator input block is under a predefined first threshold value, while, when said voltage value on said second input node is higher than said predefined first threshold value, said supplying pre-regulation block cuts a supplying from said first input node and switches a supply path of said control circuit to said second input node.

3. Voltage converter according to claim 2, wherein said control circuit further comprises a gate driver block connected to said first output node as well to said first input node and able to drive said control terminal of said switching component in such a way that said voltage value in absolute value on said second input node is all the time between a second and a third predetermined threshold values.

4. Voltage converter according to claim 3, wherein said control circuit further comprises a synchronization block connected to said gate driver block and synchronizing the latter with said supply voltage reference to optimize the current consumption.

5. Voltage converter according to claim 3, wherein said control circuit further comprises a step-down driver block connected to said second input node and to said switching node of said step-down block and able to convert said voltage value on said second input node, which has a big ripple and comes from said pre-regulator input block to a voltage value on said switching node, which has a very low ripple and is suitable to be applied to said step-down block for the supplying of said semiconductor light source.

6. Voltage converter according to claim 5, wherein said step-down driver block has a high value switching frequency, for example equal to 1.8 Mhz.

7. Voltage converter according to claim 5, wherein said step-down driver block has an input terminal connected to a logic block, in turn connected to a locking block, said logic block driving said step-down driver block according to an internal state-machine to guarantee a proper operation of said control circuit, and said locking block stopping the operation of said control circuit when a voltage value being detected on a third input node of said control circuit is under a lockout voltage value.

8. Voltage converter according to claim 7, wherein said control circuit further comprises a dimming block connected to a fourth input node of said control circuit and to a peak detection block, in turn connected to said first input node of said control circuit, said peak detection block detecting peak voltage values on said supply voltage reference by detecting a voltage value on said first input node, in turn connected to said input terminal of the converter and reconstructing the RMS or Root mean square value of said supply voltage reference, providing it to said dimming block, which works with the information coming from said peak detection block and from said fourth input node.

9. Voltage converter according to claim 4, wherein said pre-regulator input block further comprises a fuse component inserted between said input terminal and said switching component and having a control terminal connected to a second output node of said control circuit.

10. Voltage converter according to claim 9, wherein said control circuit further comprises a protection block connected to said second output node of said control circuit and able to drive said fuse component of said pre-regulator input block to protect said semiconductor light source connected to said voltage converter as well as an user thereof from high voltage values of said supply voltage reference, said protection block being able to detect any failure on said supply voltage reference during its normal working or during the assembly/manufacturing of said voltage converter.

11. Voltage converter according to claim 1, wherein said control circuit is integrated in one single chip, the whole voltage converter being a System in Package.

12. Voltage converter according to claim 11, wherein power devices associated to said control circuit are also integrated in said one single chip.

13. Method for supplying a semiconductor light source starting from a power supply reference, namely an AC mains voltage reference to provide a current signal to said semiconductor light source, the method comprising the steps of:

preregulating said power supply reference into a preregulated voltage signal by means of a capacitive block which decreases the power supply reference voltage to said preregulated voltage signal;

converting said preregulated voltage signal, which has a big ripple, into a switching voltage which has a very low ripple and is suitable to be applied to a step-down block for the supplying of said semiconductor light source; and

feeding back said preregulated voltage signal by suitably driving the switching on of a switching component connected to said capacitive block.

14. Method according to claim 13, further comprising a step of cutting the supplying from said power supply reference when said pre-regulated voltage signal is higher than a predefined first threshold value and switching the supply path in such a way to use said pre-regulated voltage signal.

15. Method according to claim 14, further comprising a step of driving said switching component in such a way that the voltage value in absolute value of said pre-regulated voltage signal is between a second and a third predetermined threshold values.

16. Method according to claim 15, wherein said step of driving said switching component is synchronized with said power supply reference.

17. Method according to claim 14, further comprising a step of dimming said current signal provided to said semiconductor light source according to the value of said power supply reference and to an external dimming signal.

18. A converter, comprising:

at least one input node operable to receive an AC power signal;

at least one output node operable to provide an output power signal;

a first regulator coupled to the at least one input node and operable to convert the AC power signal into an intermediate power signal having a first voltage level having a first magnitude; and

a second regulator coupled to the at least one output node and to the first regulator and operable to convert the intermediate power signal into the output power signal having a second voltage level having a second magnitude that is lower than the first magnitude.

19. The converter of claim 18 wherein the first regulator comprises:

a switch having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch and operable to provide the intermediate power signal.

20. The converter of claim 18 wherein the first regulator comprises:

a switch having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch and operable to provide the intermediate power signal.

21. The converter of claim 18, further comprising:

wherein the first regulator comprises;

a switch component having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch component and operable to provide the intermediate power signal; and

a synchronizer operable to cause the switch component to switch synchronously with the AC power signal.

22. The converter of claim 18, further comprising:

wherein the first regulator comprises;

a switch component having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch component and operable to provide the intermediate power signal; and

a synchronizer operable to cause the switch component to turn on only in response to an instantaneous voltage level of the AC power signal being greater than a threshold.

23. The converter of claim 18, further comprising:

wherein the first regulator comprises;

a switch component having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch component and operable to provide the intermediate power signal; and

a synchronizer operable to cause the switch component to turn on only in response to an instantaneous voltage level of the AC power signal having a magnitude that is greater than a threshold.

24. The converter of claim 18, further comprising:

wherein the first regulator comprises;

a switch component having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch component and operable to provide the intermediate power signal; and

a synchronizer operable to cause the switch component to turn on only in response to an instantaneous voltage level of the AC power signal being within a range.

25. The converter of claim 18, further comprising:

wherein the first regulator comprises;

a switch component having a first node coupled to the at least one input node and having a second node; and

at least one capacitor coupled to the switch component and operable to provide the intermediate power signal; and

a synchronizer operable to cause the switch component to turn on only in response to an instantaneous voltage level of the AC power signal having a magnitude that is within a range.

26. The converter of claim 18 wherein the second regulator comprises a buck converter.

27. The converter of claim 18 wherein the second regulator comprises a pulse-width modulated buck converter.

28. The converter of claim 18, further comprising:

an integrated-circuit die; and

wherein the input node, output node, first regulator, and second regulator are disposed on the die.

29. The converter of claim 18, further comprising a sense circuit that, in response to the intermediate power signal having a voltage that is below a threshold, is operable to couple the AC power signal to the second regulator and to cause the second regulator to generate the output power signal from the AC power signal.

30. The converter of claim 18, further comprising a dimming circuit coupled to the second regulator and operable to adjust the second voltage level.

31. The converter of claim 18, further comprising a fuse coupled between the input node and the first regulator.

32. The converter of claim 18 wherein the output power signal comprises a DC power signal.

33. A system, comprising:

at least one load; and

a converter, comprising;

at least one input node operable to receive an AC power signal;

at least one output node coupled to the at least one load;

a first regulator coupled to the at least one input node and operable to convert the AC power signal into an intermediate power signal having a first voltage level; and

a second regulator coupled to the at least one output node and to the first regulator, operable to convert the intermediate power signal into an output power signal having a second voltage level that is lower than the first voltage level, and operable to provide the output power signal to the output node.

34. The system of claim 33 wherein the at least one load comprises at least one LED.

35. The system of claim 33 wherein the at least one load comprises multiple loads coupled in series.

36. The system of claim 33 wherein the at least one load comprises multiple loads coupled in parallel.

37. The system of claim 33 wherein:

at least one component of the converter is disposed on an integrated circuit; and

at least one component of the converter is disposed external to the integrated circuit die.

38. The system of claim 33 wherein the converter is disposed on an integrated-circuit.

39. A method, comprising:

converting an AC voltage having a first magnitude into an intermediate voltage having a second magnitude that is lower than the first magnitude;

converting the intermediate voltage into an output voltage having a third magnitude that is lower than the first and second magnitudes in response to the second magnitude having being higher than a first threshold; and

converting the AC voltage into the output voltage in response to the second magnitude being lower than the first threshold.

40. The method of claim 39 wherein the first magnitude comprises a peak magnitude.

41. The method of claim 39 wherein the first magnitude comprises a root-mean-square magnitude.

42. The method of claim 39 wherein the second and third magnitudes comprise respective DC magnitudes.

43. The method of claim 39 wherein the second magnitude comprises an average DC magnitude.

44. The method of claim 39 wherein the second magnitude comprises a root-mean-square magnitude.

45. The method of claim 39, further comprising powering at least one LED with the output voltage.

46. The method of claim 39, further comprising adjusting the third magnitude of the output voltage in response to an adjust signal.

47. The method of claim 39, further comprising adjusting the third magnitude of the output voltage in response to an adjust signal and the first magnitude.

48. The method of claim 39, further comprising, in response to the first magnitude exceeding a second threshold, uncoupling the AC power signal from a circuit that converts the AC power signal into the intermediate power signal.

49. The method of claim 39, further comprising, in response to the first magnitude being less than a second threshold, disabling generation of the output voltage.