VOLTAGE CONVERTER WITH COMBINED BUCK CONVERTER AND CAPACITIVE VOLTAGE DIVIDER

• US 20090033289A1
• Filed: 07/23/2008
• Published: 02/05/2009
• Est. Priority Date: 08/01/2007
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Miller, Greg J., Xing, Kun
• Granted Patent: US 8,427,113 B2
• Time in Patent Office: Days
• US Class Current: 320/140
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 7/4837 Flying capacitor converters
• CPC Class Codes: Y02B 40/00 Technologies aiming at improving the efficiency of home appliances, e.g. induction cooking or efficient technologies for refrigerators, freezers or dish washers
• 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 voltage converter including a buck converter and a capacitive voltage divider. The converter includes four capacitors, a switch circuit, an inductor and a controller. A first capacitor is coupled between a reference node and a first output node which develops a first output voltage. A second capacitor is coupled between an input node and either the reference node or the first output node. The switch circuit couples a third capacitor between the reference and first output nodes in a first state of a PWM signal, and couples the third capacitor between the first output and input nodes in a second PWM signal state. The inductor is coupled to the third capacitor and provides a second output node coupled to the fourth capacitor providing a second output voltage. The controller controls the duty cycle of the PWM signal to regulate the second output voltage to a predetermined level.

Claims

1. A voltage converter, comprising:

a first capacitor coupled between a reference node and a first output node wherein said first output node develops a first output voltage;

a second capacitor coupled between an input node and either one of said reference and first output nodes;

a third capacitor having first and second ends;

a first switch circuit which couples said first and second ends of said third capacitor to said reference node and said first output node, respectively, in a first state of a pulse width modulation signal, and which couples said first and second ends of said third capacitor to said first output node and said input node, respectively, in a second state of said pulse width modulation signal;

an inductor having a first end coupled to said first end of said third capacitor and having a second end forming a second output node providing a second output voltage;

a fourth capacitor coupled between said second output voltage and said reference node; and

a controller which controls duty cycle of said pulse width modulation signal between said first and second states to regulate said second output voltage to a predetermined voltage level.

2. The voltage converter of claim 1, wherein said controller comprises:

a regulator having an input sensing said output voltage and an output providing said pulse width modulation signal; and

a switch driver circuit receiving said pulse width modulation signal and an output controlling said first switch circuit.

3. The voltage converter of claim 1, further comprising an external power source which provides an input voltage to said input node.

4. The voltage converter of claim 3, wherein said external power source comprises an AC to DC adapter.

5. The voltage converter of claim 1, further comprising:

an external power source which provides an input voltage to said input node;

a rechargeable battery;

a second switch circuit which selectively couples said output of said external power source to said input node and which selectively couples said rechargeable battery to said first output node; and

a battery charger and control circuit having a power input coupled to said input node, a first output coupled to said rechargeable battery, and having a second output for controlling said second switch circuit.

6. The voltage converter of claim 5, wherein:

when said external power source provides said input voltage, said battery charger and control circuit controls said second switch circuit to couple said output of said external power source to said input node; and

wherein when said external power source does not provide said input voltage, said battery charger and control circuit controls said second switch circuit to couple said rechargeable battery to said first output node.

7. The voltage converter of claim 1, further comprising:

said second capacitor being coupled between said input node and said first output node; and

a fifth capacitor coupled between said input node and said reference node.

8. An electronic device, comprising:

a combined buck converter and capacitor voltage divider, comprising;

a first capacitor coupled between a reference node and a first power node wherein said first power node develops a first source voltage;

a second capacitor coupled between an input node and either one of said reference and first power nodes;

a third capacitor having first and second ends;

a first switch circuit which couples said first and second ends of said third capacitor to said reference node and said first power node, respectively, in a first state of a pulse width modulation signal, and which couples said first and second ends of said third capacitor to said first power node and said input node, respectively, in a second state of said pulse width modulation signal;

an inductor having a first end coupled to said first end of said third capacitor and having a second end forming a second power node providing a second source voltage;

a fourth capacitor coupled between said reference node and said second power node; and

a controller which controls duty cycle of said pulse width modulation signal between said first and second states to regulate said second source voltage to a predetermined voltage level;

a power source node for receiving an input voltage; and

functional circuitry which receives said first and second source voltages and which performs functions of the electronic device.

9. The electronic device of claim 8, further comprising an external power source having an output for coupling to said power source node for providing said input voltage.

10. The electronic device of claim 9, wherein said external power source comprises an AC to DC adapter.

11. The electronic device of claim 8, further comprising:

a battery node; and

a control circuit which selectively couples said power source node to said input node when said input voltage is provided, and which selectively couples said battery node to said first power node when said input voltage is not provided.

12. The electronic device of claim 11, further comprising a battery charger having a power input coupled to said input node and having an output coupled to said battery node.

13. The electronic device of claim 12, wherein said combined buck converter and capacitor voltage divider, said power source node, said battery node, said battery charger, said control circuit, and said functional circuitry are incorporated onto a printed circuit board.

14. The electronic device of claim 13, wherein said printed circuit board is provided within a notebook computer.

15. The electronic device of claim 12, further comprising a rechargeable battery having a terminal coupled to said battery node.

16. A method of converting an input voltage to a first output voltage and a second output voltage, comprising:

providing the input voltage to an input node relative to a reference node;

coupling a capacitor loop between the input node, the reference node, and a first output node developing the first output voltage;

toggling coupling of a fly capacitor based on duty cycle of a pulse width modulation signal, wherein the fly capacitor is charged between the input node and the first output node and discharged between the first output node and a reference node;

selectively toggling a first end of an inductor between the first output node and the reference node based on the duty cycle of the pulse width modulation signal;

coupling the second end of the inductor to a second output node which develops a second output voltage; and

controlling the duty cycle of the pulse width modulation signal to regulate the second output voltage to a predetermined level.

17. The method of claim 16, further comprising:

monitoring the second output voltage and adjusting the duty cycle of the pulse width modulation signal to maintain the second output voltage at the predetermined level; and

converting the pulse width modulation signal to drive signals for controlling electronic switches for said toggling coupling of the fly capacitor.

18. The method of claim 16, further comprising receiving voltage from an external power source and providing the received voltage to the input node.

19. The method of claim 16, further comprising:

providing a battery node; and

providing a battery charger which converts the input voltage to charge current provided to the battery node.

20. The method of claim 16, further comprising coupling a battery between the first output node and the reference node when the input voltage is not provided.

21. The method of claim 16, wherein:

said coupling a capacitor loop comprises;

coupling a second capacitor between the first output node and the reference node; and

coupling a first end of a third capacitor to the input node and coupling the second end of the third capacitor to one of the first output node and the reference node;

wherein said toggling coupling of a fly capacitor comprises switchably coupling the fly capacitor between the input node and the first output node in a first state of the pulse width modulation signal and between the first output node and the reference node in a second state of the pulse width modulation signal; and

wherein said selectively toggling a first end of an inductor comprises coupling the first end of the inductor to the second end of the fly capacitor.