DC/DC converter with inductor current sensing capability

• US 7,196,499 B1
• Filed: 09/21/2006
• Issued: 03/27/2007
• Est. Priority Date: 09/27/2005
• Status: Active Grant

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro Incorporated
• Inventors: Lipcsei, Laszlo
• Primary Examiner(s): Vu; Bao Q.
• Application Number:
  US11/524,862
• Publication Number:
  US 20070069699A1
• Time in Patent Office: 187 Days
• Field of Search: 323/222, 323/282, 323/284, 323/283, 323/285
• US Class Current: 323/222
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• 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

A DC/DC converter for converting an input voltage to an output voltage comprises a switch, an inductor, two voltage dividers, a capacitor, and a controller. The switch coupled to the input voltage. The inductor having a parasitic direct current resistance is used for coupling the switch to an output node of the DC/DC converter so as to generate the output voltage at the output node. The first voltage divider is coupled to the output node for generating a divided voltage of the output voltage. The second voltage divider is coupled to the switch and ground. The capacitor coupled to the first voltage divider and the second divider to measure the current through the inductor by sensing a voltage across the capacitor. The controller coupled to the first switch for enabling and disenabling it so as to discontinuously providing power from the input voltage to the inductor.

Claims

1. A DC/DC converter for converting an input voltage to a predetermined output voltage at an output node, comprising:

a first switch for receiving said input voltage;

an inductor for coupling said first switch to said output node of said DC/DC converter such that said output voltage being generated at said output node;

a first voltage divider coupled to said output node for generating a divided voltage;

a second voltage divider coupled between said first switch and ground;

a capacitor coupled between said first voltage divider and said second voltage divider, the capacitor being capable of measuring a current passing through said inductor by sensing a voltage across said capacitor, and

a controller coupled to said first switch for enabling and disenabling said first switch such that power being discontinuously provided from said input voltage to the inductor and said output voltage being adjusted to a predetermined level.

2. The DC/DC converter of claim 1, wherein said controller being capable of receiving said divided voltage, said divided voltage serving as a feedback signal from said output voltage to said controller.

3. The DC/DC converter of claim 2, wherein said controller being capable of sensing a voltage across said capacitor such that said current passing through said inductor being determined.

4. The DC/DC converter of claim 3, wherein said controller being capable of generating a PWM signal for enabling said switch.

5. The DC/DC converter of claim 1, further comprising a second switch for coupling said first switch and said inductor to ground such that a discharging path being provided.

6. The DC/DC converter of claim 5, wherein said controller being coupled to said second switch for enabling and disenabling said second switch.

7. The DC/DC converter of claim 6, wherein said controller being capable of generating a second PWM signal for enabling said second switch.

8. The DC/DC converter of claim 1, wherein said first voltage divider further comprises:

a first resistor coupled to said output node of said DC/DC converter, and

a second resistor for coupling said first resistor to ground.

9. The DC/DC converter of claim 1, wherein said second voltage divider comprises:

a third resistor having a resistance that is substantially larger than a resistance of said first resistor, said third resistor being coupled to said first switch, and

a fourth resistor having a resistance that is substantially larger than a resistance of said second resister, said fourth resistor coupling said third resistor to ground.

10. The DC/DC converter of claim 9, wherein a ratio between said third resistor and said forth resistor being equal to a ratio between said first resistor and said second resistor.

11. The DC/DC converter of claim 1, further comprising:

an output capacitor coupled to said output node of said DC/DC converter for reducing a ripple voltage at said output node.

12. A method for converting an input DC voltage to a predetermined DC voltage at an output terminal, comprising the steps of:

receiving an input DC voltage at a first switch;

controlling said first switch to discontinuously coupling said input DC voltage to an inductor for generating an output DC voltage;

generating a feedback voltage signal at a first voltage divider coupled to said output terminal, wherein said feedback voltage signal being proportional to a voltage at said output terminal;

generating a feedback current signal at a capacitor coupled to said first voltage divider and a second voltage divider, wherein said second voltage divider being coupled to said inductor, and wherein said feedback current signal being proportional to a current through said inductor; and

receiving said feedback voltage signal and said feedback current signal such that said output DC voltage being adjusted to a predetermined level.

13. The method of claim 12, further comprising the step of:

reducing a ripple voltage at said output terminal by coupling an output capacitor to said output terminal.

14. The method of claim 12, wherein said step of controlling said first switch further comprises the step of:

controlling said switch with a PWM signal.

15. The method of claim 12, further comprising the step of:

providing a discharging path by coupling a second switch to said first switch and ground.

16. The method of claim 12, wherein a time constant of said inductor matches with a time constant of said capacitor and said second voltage divider.

17. The method of claim 16, wherein said first voltage divider comprises a first resistor coupled to said output terminal, and a second resistor for coupling said first resistor to ground such that said feedback voltage signal being generated at a node between said first and said second resistors.

18. The method of claim 17, wherein said second voltage divider comprises a third resistor coupled to said inductor and a fourth resistor for coupling said third resistor to ground, said capacitor coupled to said first, said second, said third, and said fourth resistors, and said feedback current signal being a voltage across said inductor.

19. The method of claim 18, wherein a ratio between said third resister and said fourth resistor being equal to a ratio between said first resister and said second resistor.