Low cost power supply circuit and method

• US 8,754,587 B2
• Filed: 06/29/2010
• Issued: 06/17/2014
• Est. Priority Date: 07/03/2009
• Status: Expired due to Fees

• Current Assignee: Philips Lighting Holding BV (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Van Der Veen, Geert Willem, Snelten, Jeroen
• Primary Examiner(s): Hammond, Crystal L
• Application Number:
  US13/381,980
• Publication Number:
  US 20120112657A1
• Time in Patent Office: 1,449 Days
• Field of Search: None
• US Class Current: 315/291
• 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 3/335 using semiconductor devices only
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• 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 power supply circuit has an LLC converter stage for converting a DC voltage input into a DC voltage output, and at least one hysteretic converter stage. Each hysteretic converter stage has a DC voltage input coupled to the DC voltage output of the LLC converter stage, and a DC current output. The LLC converter stage lacks a feedback control, and is operated at its load independent point. A ripple on the DC voltage output of the LLC converter does not affect the output current of the hysteretic converter stage. The stable DC current output of the hysteretic converter stage is coupled to a load having one or more LED strings.

Claims

1. A power supply circuit for supplying a stable DC current output, the power supply circuit comprising:

an LLC converter stage for converting a DC voltage input into a DC voltage output; and

at least one hysteretic converter stage having a DC voltage input coupled to the DC voltage output of the LLC converter stage, and having a DC current output,

wherein the LLC converter stage lacks a feedback control.

2. The power supply circuit of claim 1, wherein the LLC converter stage is configured to operate at a predetermined frequency.

3. The power supply circuit of claim 2, wherein the LLC converter stage is configured to operate at a load independent point of the predetermined frequency.

4. The power supply circuit of claim 1, wherein voltage at the DC current output of the hysteretic converter stage is lower than voltage at the DC voltage input of the hysteretic converter stage.

5. The power supply circuit of claim 4, wherein the hysteretic converter stage comprises a buck converter.

6. The power supply circuit of claim 1, further comprising:

a mains converter stage for converting an AC mains voltage into a DC voltage output, wherein the DC voltage input of the LLC converter stage is coupled to the DC voltage output of the mains converter stage.

7. A lighting arrangement comprising:

the power supply circuit of claim 1; and

a LED lighting module, wherein the DC current output of the at least one hysteretic converter stage is coupled to the LED lighting module.

8. A method of supplying a stable DC current to at least one load, the method comprising:

converting a DC voltage input into a DC voltage output by an LLC converter stage operated at a predetermined frequency;

converting the DC voltage output of the LLC converter stage into at least one DC current output by at least one hysteretic converter stage; and

supplying the at least one DC current output to the at least one load.

9. The method of claim 8, wherein the LLC converter stage is operated at a load independent point thereof.

10. A power supply circuit for supplying a stable DC current output, the power supply circuit comprising:

an LLC converter stage for converting DC input voltage into a DC output voltage, the LLC converter stage comprising;

input terminals configured to receive the DC input voltage;

output terminals configured to output the DC output voltage;

a first switch and a second switch connected in series between the input terminals;

a series arrangement of at least one inductor and a capacitor connected in parallel with one of the first switch and the second switch; and

a control circuit configured to control a switching frequency of the first and second switches to operate at a predetermined frequency; and

a hysteretic converter stage having input terminals coupled to the output terminals of the LLC converter to receive the DC output voltage, and having output terminals to output a DC output current to a corresponding load.

11. The power supply circuit of claim 10, wherein the control circuit does not provide feedback control to the LLC converter stage.

12. The power supply circuit of claim 10, wherein the at least one inductor comprises a first inductor and a second inductor connected in series between the one of the first and second switches and the capacitor.

13. The power supply circuit of claim 12, wherein the second inductor is a transformer.

14. The power supply circuit of claim 13, wherein the LLC converter stage further comprises:

a rectifier circuit coupled to the second inductor and configured to isolate and filter the DC output voltage output at the output terminals.