DC/DC converter with improved stability

• US 7,446,516 B2
• Filed: 08/11/2006
• Issued: 11/04/2008
• Est. Priority Date: 08/19/2005
• Status: Expired due to Fees

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Lipcsei, Laszlo, Hornet, Sorin
• Primary Examiner(s): Laxton; Gary L
• Application Number:
  US11/502,904
• Publication Number:
  US 20070040538A1
• Time in Patent Office: 816 Days
• Field of Search: 323/224, 323/271, 323/282, 323/285
• US Class Current: 323/282
• CPC Class Codes: H02M 1/143 using compensating arrangements for reducing noise from the supply in transmission systems H04B15/005
• 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

The DC/DC converter according to one embodiment includes a switch, an inductor, a capacitor, a resistor, and a voltage divider. The switch is coupled to the input voltage. The inductor is used for coupling the first switch to an output node of the DC/DC converter so as to generate the output voltage at the output node. The capacitor is coupled to the output voltage. The resistor is coupled to the capacitor in series, and is coupled to ground. The voltage divider is coupled across the capacitor so as to reduce the zero frequency of the DC/DC converter.

Claims

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

a first switch coupled to said input voltage;

an inductor for coupling said first switch to an output node of said DC/DC converter so as to generate said output voltage at said output node;

a capacitor coupled to said output voltage;

a first resistor coupled between said capacitor and ground for determining a zero frequency of said DC/DC converter; and

a voltage divider coupled to said capacitor in parallel and coupled to said first resistor in series and for determining said zero frequency of said DC/DC converter.

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

a controller coupled to said first switch and said voltage divider wherein said voltage divider generates a feedback voltage in response to said output voltage and said controller controls the state of said first switch in response to said feedback voltage.

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

a second resistor; and

a third resistor coupled to said second resistor in series for generating a feedback voltage in response to said output voltage.

4. The DC/DC converter of claim 3, further comprising:

a controller coupled to said first switch and receiving said feedback voltage so as to control the state of said first switch in response to said feedback voltage.

5. The DC/DC converter of claim 3, wherein said first resistor, said second resistor and said third resistor are coupled in series.

6. The DC/DC converter of claim 1, wherein said capacitor comprises a ceramic capacitor.

7. The DC/DC converter of claim 1, wherein said first switch comprises a MOS transistor.

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

a second switch for coupling said first switch to ground.

9. The DC/DC converter of claim 8, further comprising:

a controller coupled to said first switch, said second switch, and said voltage divider,

wherein said voltage divider generates a feedback voltage in response to said output voltage and said controller controls the state of said first switch and the state of said second switch in response to said feedback voltage.

10. The DC/DC converter of claim 9, wherein said controller generates a first PWM signal, and said first PWM signal is transmitted to said first switch for controlling the state of said first switch.

11. The DC/DC converter of claim 10, wherein said controller generates a second PWM signal, and said second PWM signal is transmitted to said second switch for controlling the state of said second switch.

12. The DC/DC converter of claim 8, wherein said second switch comprises a diode.

13. The DC/DC converter of claim 8, wherein said second switch comprises a MOS transistor.

14. A method for controlling a DC/DC converter for converting an input voltage to an output voltage, comprising:

receiving said input voltage;

coupling a first switch to said input voltage;

coupling an inductor to said first switch so as to discontinuously transmit power from said input voltage to said inductor;

coupling a capacitor to a first resistor in series and to said inductor;

coupling said first resistor between said capacitor and ground;

coupling a voltage divider in parallel to said capacitor and in series to said first resistor;

achieving a specified zero frequency of said DC/DC converter according to said first resistor and said voltage divider;

generating a feedback voltage signal by said voltage divider; and

generating a PWM signal to discontinuously enable said first switch so as to discontinuously transmit power from said input voltage to said inductor.

15. The method as claimed in claim 14, wherein said generating said PWM signal further comprises:

generating said PWM signal in response to said feedback voltage signal.

16. The method as claimed in claim 14, wherein said capacitor comprises a ceramic capacitor.

17. The method as claimed in claim 14, wherein said generating said feedback voltage signal further comprises:

coupling a second resistor and a third resistor in series so as to form a voltage divider; and

coupling said voltage divider across said capacitor.

18. The method as claimed in claim 17, further comprising:

coupling said first resistor, said second resistor and said third resistor in series.

19. The method as claimed in claim 14, further comprising:

coupling a second switch to said first switch for coupling said first switch to ground; and

generating a second PWM signal to discontinuously enable said second switch.