Voltage converter for supplying a semiconductor light source, in particular a LED lamp

• US 8,928,252 B2
• Filed: 07/09/2010
• Issued: 01/06/2015
• 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
• Primary Examiner(s): Vu, Jimmy
• Assistant Examiner(s): YANG, AMY X
• Application Number:
  US12/833,280
• Publication Number:
  US 20110006691A1
• Time in Patent Office: 1,642 Days
• Field of Search: 315/185.R, 315/291, 315/294, 315/192
• US Class Current: 315/294
• 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 disclosure 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. A voltage converter for supplying a semiconductor light source, comprising:

at least an input terminal coupled to a power supply reference;

an output terminal providing a current signal to said semiconductor light source;

a voltage reference;

at least a step-down block inserted between a switching node and to said output terminal and coupled to said voltage reference; and

an input block coupled to said input terminal, as well as to a first input node and to a first output node of a control circuit, in turn coupled to said switching node and to said voltage reference;

wherein said input block is a pre-regulator input block and includes at least a switching component coupled 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 coupled to said first output node; and

wherein said control circuit further includes a supplying pre-regulation block which is directly coupled to a third input node and is also coupled to said first input node by means of a regulation diode, said first input node being also coupled 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.

2. The voltage converter according to claim 1, wherein said control circuit further comprises a gate driver block coupled 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.

3. The voltage converter according to claim 2, wherein said control circuit further comprises a synchronization block coupled to said gate driver block and synchronizing the latter with said supply voltage reference to optimize the current consumption.

4. The voltage converter according to claim 3, 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 coupled to a second output node of said control circuit.

5. The voltage converter according to claim 4, wherein said control circuit further comprises a protection block coupled 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 coupled 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.

6. The voltage converter according to claim 2, wherein said control circuit further comprises a step-down driver block coupled 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.

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

8. The voltage converter according to claim 6, wherein said step-down driver block has an input terminal coupled to a logic block, in turn coupled 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.

9. The voltage converter according to claim 8, wherein said control circuit further comprises a dimming block coupled to a fourth input node of said control circuit and to a peak detection block, in turn coupled 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 coupled 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.

10. The 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.

11. Voltage converter according to claim 10, further comprising at least one power device also integrated in said one single chip.

12. A method for supplying a semiconductor light source, the method comprising:

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

converting said preregulated voltage signal, which has a ripple, into a switching voltage which has less 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 coupled to said capacitive block.

13. The method according to claim 12, 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.

14. The method according to claim 13, 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.

15. The method according to claim 14, wherein said step of driving said switching component is synchronized with said power supply reference.

16. The method according to claim 13, 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.

17. A converter, comprising:

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

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

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

a second regulator coupled to the at least one output node and to the first regulator and configured 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; and

a feedback circuit coupled to the output node through a load and configured to provide the feedback signal to the first regulator.

18. The converter of claim 17 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 configured to provide the intermediate power signal.

19. The converter of claim 17 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 configured to provide the intermediate power signal.

20. The converter of claim 17,

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 configured to provide the intermediate power signal; and

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

21. The converter of claim 17,

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 configured 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.

22. The converter of claim 17,

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 configured to provide the intermediate power signal; and

a synchronizer configured 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.

23. The converter of claim 17,

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 configured to provide the intermediate power signal; and

a synchronizer configured 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.

24. The converter of claim 17,

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 configured to provide the intermediate power signal; and

a synchronizer configured 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.

25. The converter of claim 17 wherein the second regulator comprises a buck converter.

26. The converter of claim 17 wherein the second regulator comprises a pulse width modulated buck converter.

27. The converter of claim 17, further comprising:

an integrated circuit die; and

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

28. The converter of claim 17, further comprising a sense circuit that, in response to the intermediate power signal having a voltage that is below a threshold, is configured 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.

29. The converter of claim 17, further comprising a dimming circuit coupled to the second regulator and configured to adjust the second voltage level.

30. The converter of claim 17, further comprising a fuse coupled between the input node and the first regulator.

31. The converter of claim 17 wherein the output power signal comprises a DC power signal.

32. A system, comprising:

at least one load; and

a converter, comprising;

at least one input node configured 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 configured to convert the AC power signal into an intermediate power signal having a first voltage level in response to the AC power signal and a feedback signal;

a second regulator coupled to the at least one output node and to the first regulator, configured 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; and

a feedback circuit coupled to the output node through a load and configured to provide the feedback signal to the first regulator.

33. The system of claim 32 wherein the at least one load comprises at least one LED.

34. The system of claim 32 wherein the at least one load comprises multiple loads coupled in series.

35. The system of claim 32 wherein the at least one load comprises multiple loads coupled in parallel.

36. The system of claim 32 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.

37. The system of claim 32 wherein the converter is disposed on an integrated circuit.