Controlled on-time buck PFC

• US 8,922,189 B2
• Filed: 11/18/2008
• Issued: 12/30/2014
• Est. Priority Date: 11/18/2008
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Neidorff, Robert A., Lu, Bing
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): LEE III, HENRY E
• Application Number:
  US12/273,460
• Publication Number:
  US 20100123448A1
• Time in Patent Office: 2,233 Days
• Field of Search: 323/299, 323/224, 323/282, 323/284
• US Class Current: 323/299
• CPC Class Codes: G05F 1/70 Regulating power factor; Regulating reactive current or power
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 1/4291 by using a Buck converter to switch the input current
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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

An apparatus for generating an output voltage from an input voltage is provided. The apparatus comprises a switch that receives the input voltage, an inductor that is coupled to the switch, a capacitor coupled to the inductor with the output voltage being output from a node between the inductor and the capacitor, a measuring circuit that receives and measures the input voltage, and a controller that is coupled to the switch and to the measuring circuit. Additionally, the controller receives the measured input voltage and calculates an on-time for the switch based on the measured input voltage and actuates the switch for the on-time.

Claims

1. An apparatus for generating an output voltage from an input voltage, the apparatus comprising:

a full wave bridge rectifier having a positive rail as an output of the full wave bridge rectifier and a negative rail as an input of the full wave bridge rectifier;

a switch that receives the input voltage minus a voltage drop across a diode of the full wave bridge rectifier on the positive rail;

an inductor that is coupled to an output of the switch;

a capacitor coupled to the inductor, wherein the output voltage is output from between;

a) a node between the inductor and the capacitor and

b) the negative rail;

a measuring circuit that receives and measures a voltage difference of the voltage between the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier, the negative rail also coupled to the measuring circuit and the capacitor; and

a controller that is coupled to both the switch and to the measuring circuit, wherein the controller receives the measured voltage difference between the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier and calculates an on-time for the switch attributed to the measured voltage difference of the positive rail and the negative rail, and wherein the controller actuates the switch for the on-time,

wherein the controller and the measuring circuit operate in an open loop control system due to the measured voltage difference between the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier.

2. The apparatus of claim 1, wherein the on-time is proportional to the square of the input voltage divided by the difference between the input voltage and the output voltage.

3. The apparatus of claim 1, wherein the on-time is proportional to the input voltage.

4. The apparatus of claim 1, wherein the apparatus further comprises a second switch that is coupled between the first switch and ground, wherein the controller is adapted to actuate the second switch.

5. The apparatus of claim 4, wherein the first and second switches are NMOS FETs.

6. The apparatus of claim 1, wherein a reverse bias diode is coupled between the switch and ground.

18. The apparatus of claim 1, wherein an input of a full bridge rectifier is coupled to the negative rail, and an output of the full bridge rectifier is coupled to the positive rail.

21. The apparatus of claim 1, wherein the input voltage is generated by an alternating current source.

7. An apparatus for generating an output voltage from an input voltage, the apparatus comprising:

a full wave bridge rectifier that receives the input voltage having a positive rail as an output of the full wave bridge rectifier and a negative rail as an input of the full wave bridge rectifier;

a switch half bridge coupled to the positive rail and the negative rail, including;

a) a first switch that receives the input voltage minus a voltage drop across a diode of the full wave bridge rectifier on the positive rail;

b) a second switch that is coupled to an output of the first switch and having an output that is coupled to the negative rail;

an inductor that is coupled to a node between the first switch and the second switch;

a capacitor coupled to the inductor, wherein the output voltage is output between;

a) a node between the inductor and the capacitor; and

b) the negative rail;

a measuring circuit that receives and measures the voltage difference between a coupled the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier, the negative rail further coupled to the capacitor; and

a controller that is coupled to both the bridge, and is further coupled to the first switch and the second switch, and to the measuring circuit, wherein the controller receives the measured input voltage difference and calculates an on-time, and wherein the on-time is a function of the measured voltage difference between the positive rail and the negative rail, and wherein the controller actuates the bridge for the on-time,

wherein the controller and the measuring circuit operate in an open loop control system due to the measured voltage difference between the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier.

8. The apparatus of claim 7, wherein the on-time is proportional to the square of the input voltage divided by the difference between the input voltage and the output voltage.

9. The apparatus of claim 7, wherein the on-time is proportional to the input voltage.

10. The apparatus of claim 7, wherein the bridge further comprises:

a first FET that receives the input voltage at its drain, that is adapted to receive a first actuation signal at its gate from the controller, and that is coupled to the inductor at its source; and

a second FET that is coupled to the source of the first FET at its drain, that is adapted to receive a second actuation signal at its gate, and that is coupled to ground at its source.

11. The apparatus of claim 10, wherein the first and second FETs are NMOS FETs.

12. The apparatus of claim 7, wherein the bridge further comprises

a FET that receives the input voltage at its drain, that is adapted to receive a first actuation signal at its gate from the controller, and that is coupled to the inductor at its source;

and

a reverse bias diode coupled between the source of the FET and ground.

13. The apparatus of claim 12, wherein the FET is an NMOS FET.

15. The method of claim 11, wherein the on-time is proportional to the square of the input voltage divided by the difference between the input voltage and the output voltage.

19. The apparatus of claim 7, wherein the bridge is a full bridge rectifier, and an input of the full bridge rectifier is coupled to the negative rail, and an output of the full bridge rectifier is coupled to the positive rail.

22. The apparatus of claim 7, wherein the input voltage is generated by an alternating current source.

14. A method for generating an output voltage from an input voltage, the method comprising:

receiving the input voltage by a full wave bridge rectifier having a positive rail as an output of the full wave bridge rectifier and an negative rail as an input to the full wave rectifier;

receiving the input voltage minus a voltage drop across a diode of the full wave bridge rectifier on the positive rail at;

a) an input to a switch and

b) by a measuring circuit on a positive rail;

measuring the input voltage difference between the positive rail and the negative rail, the negative rail coupled the measuring circuit and a capacitor, with the measuring circuit;

calculating an on-time for the switch, wherein the on-time is a function of the measured input voltage difference between the positive rail and the negative rail;

actuating the switch for the on-time; and

supplying an input current and the input voltage to an inductor, the inductor coupled to the capacitor,

wherein the controller and the measuring circuit operate in an open loop control system due to the measured voltage difference between the positive rail output by the full wave bridge rectifier and the negative rail input into the full wave bridge rectifier.

16. The method of claim 14, wherein the on-time is proportional to the input voltage.

17. The method of claim 14, wherein the method further comprises actuating a second switch that is coupled to the inductor.

20. The method of claim 14, wherein an input of a full bridge rectifier is coupled to the negative rail, and an output of the full bridge rectifier is coupled to the positive rail.

23. The method of claim 14, wherein the input voltage is generated by an alternating current source.