Voltage converter with combined buck converter and capacitive voltage divider

• US 8,427,113 B2
• Filed: 07/23/2008
• Issued: 04/23/2013
• Est. Priority Date: 08/01/2007
• Status: Expired due to Fees

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Xing, Kun, Miller, Greg J.
• Primary Examiner(s): Muralidar, Richard V
• Application Number:
  US12/178,050
• Publication Number:
  US 20090033289A1
• Time in Patent Office: 1,735 Days
• Field of Search: 320/166, 320/167, 320/140, 320/141, 320/145, 320/164, 323/282, 323/283
• US Class Current: 320/145
• 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 capacitor loop coupled between an input node, a reference node, and a first output node which develops a first output voltage;

a fly capacitor coupled between first and second intermediate nodes;

a switch circuit comprising a first switch having current terminals coupled between said input node and said first intermediate node, a second switch having current terminals coupled between said first intermediate node and said first output node, a third switch having current terminals coupled between said first output node and said second intermediate node, and a fourth switch having current terminals coupled between said second intermediate node and said reference node;

an inductor having a first end coupled to said second intermediate node and having a second end coupled to a second output node which develops a second output voltage;

an output capacitor coupled between said second output node and said reference node;

a battery charger and controller operative to selectively couple an external power source node to said input node when said external power source node receives a DC voltage to provide an input voltage on said input node, to selectively couple a rechargeable battery node to said first output node when said external power source node does not receive said DC voltage, and which controls said switch circuit based on a pulse width modulation signal to regulate said second output voltage to a predetermined voltage level;

wherein when said external power source node receives said DC voltage, said battery charger and controller controls said switch circuit based on said pulse width modulation signal to toggle coupling of said first intermediate node between said input node and said first output node and to toggle coupling of said second intermediate node between said first output node and said reference node; and

wherein when said external power source node does not receive a DC voltage, said battery charger and controller turns off said first and second switches and controls said third and fourth switches based on said pulse width modulation signal to toggle coupling of said second intermediate node between said first output node and said reference node.

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

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

a switch driver circuit having an input receiving said pulse width modulation signal and having a plurality of outputs controlling said first, second, third and fourth switches.

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

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

5. The voltage converter of claim 1, wherein said capacitor loop comprises:

a first capacitor coupled between said first output node and said reference node; and

a second capacitor coupled between said input node and either one of said reference node and said first output node.

6. The voltage converter of claim 5, wherein:

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

further comprising a third capacitor coupled between said input node and said reference node.

7. The voltage converter of claim 1, wherein said battery charger and controller comprises a sense and switch circuit which detects said DC voltage provided on said external power node and activates an isolation switch to couple said external power source node to said input node.

8. The voltage converter of claim 1, wherein said battery charger and controller charges a battery coupled to said rechargeable battery node when said battery is detected and when an input voltage is detected on said input node.

9. 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 which develops a first source voltage;

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

a third capacitor coupled between first and second intermediate nodes;

a switch circuit, comprising a first switch having current terminals coupled between said input node and said first intermediate node, a second switch having current terminals coupled between said first intermediate node and said first source node, a third switch having current terminals coupled between said first source node and said second intermediate node, and a fourth switch having current terminals coupled between said second intermediate node and said reference node;

an inductor having a first end coupled to said second intermediate node and having a second end forming a second power node which develops a second source voltage;

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

a battery charger and controller operative to selectively couple an external power source node to said input node when said external power source node receives a DC voltage to provide an input voltage on said input node, to selectively couple a rechargeable battery node to said first source node when said external power source node does not receive said DC voltage, and to control said switch circuit based on a pulse width modulation signal to regulate said second source voltage to a predetermined voltage level;

wherein when said external power source node receives said DC voltage, said battery charger and controller controls said switch circuit based on said pulse width modulation signal to toggle coupling of said first intermediate node between said input node and said first output node and to toggle coupling of said second intermediate node between said first output node and said reference node; and

wherein when said external power source node does not receive said DC voltage, said battery charger and controller turns off said first and second switches and controls said third and fourth switches based on said pulse width modulation signal to toggle coupling of said second intermediate node between said first source node and said reference node; and

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

10. The electronic device of claim 9, further comprising:

a first connector electrically interfaced with said external power source node; and

an AC to DC adapter having a second connector for mating with said first connector to provide said DC voltage.

11. The electronic device of claim 9, wherein said battery charger and controller comprises a sense and switch circuit which detects a DC voltage provided on said external power node and activates an isolation switch to couple said external power source node to said input node.

12. The electronic device of claim 9, wherein said battery charger and controller has a power input coupled to said input node and has an output coupled to said rechargeable battery node, wherein said battery charger and controller charges a battery coupled to said rechargeable battery node when said battery is detected and when said DC voltage is provided.

13. The electronic device of claim 9, wherein said combined buck converter and capacitor voltage divider 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 9, 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.

16. A method of operating a power circuit providing first and second output voltages, comprising:

coupling a first switch between an input node and a first intermediate node, coupling a second switch between the first intermediate node and a first output node which develops the first output voltage, coupling a third switch between the first output node and a second intermediate node, and coupling a fourth switch between the second intermediate node and a reference node;

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

coupling a fly capacitor between the first and second intermediate nodes;

coupling an inductor between the second intermediate node and a second output node which develops the second output voltage;

controlling the duty cycle of a pulse width modulation signal for regulating the second output voltage to a predetermined level;

detecting whether a DC voltage is provided to an external power node;

when the DC voltage is provided to the external power node, coupling the external power node to the input node and controlling the first, second, third and fourth switches based on the pulse width modulation signal to toggle coupling of the first intermediate node between the input node and the first output node and to toggle coupling of the second intermediate node between the first output node and the reference node; and

when the DC voltage is not provided to the external power node, coupling a battery node to the first output node, turning off the first and second switches, and controlling the third and fourth switches based on the pulse width modulation signal to toggle coupling of the second intermediate node between the first output node and the reference node.

17. The method of claim 16, further comprising:

monitoring the second output voltage and adjusting the duty cycle of the pulse width modulation signal; and

controlling at least two of the first, second, third and fourth switches based on the pulse width modulation signal.

18. The method of claim 16, further comprising converting an input voltage provided on the input node to a charge current to charge a battery coupled to the battery node when the DC voltage is provided to the external power node.

19. The method of claim 16, further comprising detecting a battery coupled to the battery node when the DC voltage is not provided and when the battery node is coupled to the first output node, and discharging the battery via the first output node.

20. 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 a second end of the third capacitor to one of the first output node and the reference node.