Controller for DC to DC converter

• US 7,098,642 B2
• Filed: 01/18/2005
• Issued: 08/29/2006
• Est. Priority Date: 11/12/2002
• Status: Expired due to Term

• Current Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Lipcsei, Laszlo, Popescu, Serban-Mihai
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US11/037,598
• Publication Number:
  US 20050134247A1
• Time in Patent Office: 588 Days
• Field of Search: 323282-288, 323/351, 323/222, 323/224, 323/225, 323/268, 323/272, 363/16, 363/17, 363/20, 363/19, 363/21.7
• US Class Current: 323/284
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/088 for the simultaneous control of series or parallel connected semiconductor devices
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• 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 method includes starting a time count of a time interval at a start of a state change of a switch of a DC to DC converter; monitoring if the switch is in a skip mode; and disabling the skip mode in response to an expiration of the time interval so that the switch changes states at a frequency rate greater than an audible frequency for humans.

Claims

1. A switching circuit comprising:

at least one switch; and

a controller configured to control a state of said at least one switch, said controller having a skip mode wherein said controller maintains said at least one switch in an OFF state, said controller responsive to a timer, said timer configured to count for a time interval, said controller responsive to expiration of said time interval to disable said skip mode so that said at least one switch changes states at a frequency rate greater than an audible frequency limit for humans.

2. The switcbing circuit of claim 1, wherein said timer is coupled to an output terminal of said controller.

3. The switching circuit of claim 1, wherein said timer is an internal component of said controller.

4. The switching circuit of claim 1, wherein said controller is configured to control said state of said at least one switch with a periodic control signal, and wherein said timer is configured to count for said time interval upon a start of a period of said periodic control signal.

5. The switching circuit of claim 4, wherein said periodic control signal comprises a pulse width modulated signal.

6. A method comprising:

starting a time count of a time interval at a start of a state change of a switch of a DC to DC converter;

monitoring if said switch is in a skip mode; and

disabling said skip mode in response to an expiration of said time interval so that said switch changes states at a frequency rate greater than an audible frequency for humans.

7. The method of claim 6, wherein said switch comprises a high side switch of a DC to DC converter, and said DC to DC converter also comprises a low side switch, said low and high side switch being open in said skip mode.

8. The method of claim 7, wherein said disabling said skip mode in response to expiration of said time interval comprises closing said low side switch so that said high side switch changes states at said frequency rate greater than said audible frequency for humans.

9. The method of claim 8, further comprising controlling said high and low side switches with a periodic control signal, and wherein said closing of said low side switch causes discharging of an output capacitor of said DC to DC converter.

10. The method of claim 9, wherein said periodic control signal comprises a pulse width modulated signal, and wherein a new pulse of said pulse width modulated signal is generated to turn on said high side switch when a voltage level of said output capacitor decreases to a set voltage level.

11. A DC to DC converter comprising:

a high side and low side switch and

a controller configured to control a state of said high side and low side switch, said controller having a skip mode wherein said low side and high side switch are open, said controller responsive to a timer, said timer configured to count for a time interval, said controller responsive to expiration of said time interval to disable said skip mode so that said high side switch changes states at a frequency rate greater than an audible frequency limit for humans.

12. The DC to DC convener of claim 11, wherein said controller disables said skip mode in response to expiration of said time interval by closing said low side switch.

13. The DC to DC converter of claim 12, wherein said controller controls said state of said high and low side switches with aperiodic control signal, and wherein said closing of said low side switch causes discharging of an output capacitor of said DC to DC converter.

14. The DC to DC converter of claim 13, wherein said periodic control signal comprises a pulse width modulated signal, and wherein a new pulse of said pulse width modulated signal is generated to turn on said high side switch when a voltage level of said output capacitor decreases to a set voltage level.

15. The DC to DC convener of claim 11, wherein said timer is coupled to an output terminal of said controller.

16. The DC to DC convener of claim 11, wherein said timer is an internal component of said controller.