SWITCHING POWER SUPPLY SYSTEM FOR OPTICAL SOURCES OR A LOAD REQUIRING A CONTROLLED SUPPLY CURRENT

• US 20100164400A1
• Filed: 12/21/2009
• Published: 07/01/2010
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: ADRAGNA, Claudio
• Granted Patent: US 8,330,389 B2
• Time in Patent Office: Days
• 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 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching power supply for supplying a load requiring a controlled current includes a PFC pre-regulator for receiving an input voltage and providing an output voltage, and a DC-DC switching converter for receiving at input the voltage output by the pre-regulator and for providing at output a supply voltage of said load. The switching DC-DC converter operates at a fixed and constant operating frequency, is a resonant converter and includes an LLC resonant circuit.

Claims

1. A switching power supply for supplying a load requiring a controlled current, comprising:

a PFC pre-regulator for receiving an input voltage and providing an output voltage;

a DC-DC switching converter, which operates at a fixed and constant operating frequency, for receiving at input the voltage output by the pre-regulator and for providing at output a supply voltage of said load, wherein said switching DC-DC converter includes a resonant converter comprising an LLC resonant circuit.

2. A switching power supply according to claim 1, wherein said fixed operating frequency is a series resonant frequency of said LLC resonant circuit.

3. A switching power supply according to claim 1 wherein said PFC pre-regulator operates at a fixed operating frequency which substantially equals the operating frequency of said LLC converter.

4. A switching power supply according to claim 3, further comprising a synchronization system for interlocking the operating frequency of said PFC pre-regulator with the operating frequency of said DC-DC converter.

5. A switching power supply according to claim 4, wherein said DC-DC converter is a half-bridge converter and said LLC resonant circuit comprises a capacitor, a resonant inductance and a magnetizing inductance which are series connected.

6. A switching power supply according to claim 5, wherein said LLC resonant circuit comprises a control circuit comprising two series connected switches, also comprising a controller of said switches, for generating a first control signal and a second control signal for driving the first and second switch, respectively, the control signals being square wave signals, such as when one of the switches is conducting, the other of such switches is interdicted and vice versa, one of said switches, or low-side switch, when in a conduction state, being parallel connected to LLC resonant circuit represented by said capacitor and said inductances connected in series, and wherein said synchronization system is such as to provide said frequency interlocking based on the control signal of said low-side switch.

7. A switching power supply according to claim 1 wherein said PFC pre-regulator is a FF-CCM (Fixed Frequency-Continuous Conduction Mode) type boost converter.

8. A switching power supply according to claim 1, further comprising a current regulator provided between said DC-DC converter and said load.

9. A switching power supply according to claim 8, comprising a synchronization system for synchronizing said current regulator at the operating frequency of said DC-DC converter.

10. A switching power supply according to claim 1, wherein said load comprises one or more power LED diodes.

11. A switching power supply according to claim 1, wherein said resonant converter operates in a open loop operating mode.

12. A switching power supply according to claim 1, wherein said fixed frequency is not controlled by any feedback loop connected to said load.

13. A lighting apparatus comprising one or more strings of power LED diodes which are parallel connected and a switching power supply according to claim 1, wherein said load comprises said one or more strings of power LED diodes.

14. A lighting apparatus according to claim 13, further comprising a PLM modem employing a frequency band between f_min and f_max, wherein f_min is minor than f_max, said operating frequency of DC-DC converter being at a lower value than f_min if f_max/f_min≦

2 and at a higher than f_max if f_max/f_min>

2.