SYSTEM AND METHOD FOR CURRENT SENSING WITHIN A VOLTAGE REGULATOR

• US 20120229107A1
• Filed: 10/18/2011
• Published: 09/13/2012
• Est. Priority Date: 03/11/2011
• Status: Abandoned Application

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: CHEN, SICHENG, HUANG, CONGZHONG, PETRICEK, SHEA
• Application Number:
  US13/275,761
• Publication Number:
  US 20120229107A1
• Time in Patent Office: Days
• US Class Current: 323/271
• 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 current sense amplifier includes a high-side current sense amplifier and a low-side current sense amplifier. The high-side current sense amplifier provides a current sense voltage signal for use with a voltage regulator and generates the current sense voltage signal responsive to a first current sensed through a high-side switching transistor in a first mode when the high-side switching transistor is turned on and the low-side switching transistor is turned off. The high-side current sense amplifier generates the current sense voltage signal responsive to a second current through the low-side switching transistor in a second mode when the low-side switching transistor is turned on and the high-side switching transistor is turned off. The low-side current sense amplifier senses the second current through the low-side switching transistor and generates a current control signal to the high-side current sense amplifier in the second mode.

Claims

1. An apparatus, comprising:

a voltage regulator for generating a regulated output voltage responsive to an input voltage and drive control signals, the voltage regulator including a high-side switching transistor and a low-side switching transistor;

a driver circuit for generating the drive control signals responsive to a PWM control signal;

a PWM controller for generating the PWM control signal responsive to an error voltage and a ramp voltage;

a error amplifier for generating the error voltage responsive to a reference voltage, the regulated output voltage and a current sense voltage signal;

a low-side current sense amplifier for sensing a first current through the low-side switching transistor and generating a first current sense signal responsive thereto in a first mode of operation when the low-side switching transistor is turned on and the high-side switching transistor is turned off; and

a high-side current sense amplifier for providing the current sense voltage signal responsive to the first current sense signal in the first mode of operation and for sensing a second current through the high-side switching transistor and providing the current sense voltage signal responsive thereto in a second mode of operation when the high-side switching transistor is turned on and the low-side switching transistor is turned off.

2. The apparatus of claim 1, further including a plurality of switches for connecting the high-side current sense amplifier to monitor the second current through the high-side switching transistor in the second mode of operation and for connecting the high-side current sense amplifier and the low-side current sense amplifier to monitor the first current through the low-side switching transistor in the first mode of operation.

3. The apparatus of claim 1, wherein the high-side current sense amplifier further comprises:

a first transistor;

a first error amplifier for forcing a first voltage across the first transistor equal to a second voltage across the high-side switching transistor plus an offset voltage in the second mode of operation; and

a voltage source for generating the offset voltage.

4. The apparatus of claim 3, wherein the first current through the high-side switching transistor is mirrored to the first transistor of the high side current sense amplifier.

5. The apparatus of claim 4 wherein the current sense output is generated responsive to the mirrored current through the first transistor.

6. The apparatus of claim 3, wherein the low-side current sense amplifier further comprises:

a second transistor;

a third transistor;

a second amplifier for forcing a third voltage across the second transistor equal to a fourth voltage across the low-side switching transistor plus a second offset voltage and generates a first current through the third transistor, wherein the second amplifier further mirrors the first current through the third transistor to equal a second current through the first transistor in the first mode of operation.

7. The apparatus of claim 6 wherein the current sense output is generated responsive to the mirrored current through the first transistor.

8. A current sense amplifier, comprising:

a high-side current sense amplifier for providing a current sense voltage signal for use with a voltage regulator, the high-side current sense amplifier generating the current sense voltage signal responsive to a first current sensed through a high-side switching transistor of the voltage regulator in a first mode of operation when the high-side switching transistor is turned on and the low-side switching transistor of the voltage regulator is turned off, the high-side current sense amplifier generating the current sense voltage signal responsive to a second current through the low-side switching transistor in a second mode of operation when the low-side switching transistor is turned on and the high-side switching transistor is turned off;

a low-side current sense amplifier for sensing a the second current through the low-side switching transistor of the voltage regulator and generating a current control signal to the high-side current sense amplifier in the second mode of operation.

9. The current sense amplifier of claim 8, further including a plurality of switches for connecting the high-side current sense amplifier to monitor the first current through the high-side switching transistor in the first mode of operation and for connecting the high-side current sense amplifier and the low-side current sense amplifier to monitor the second current through the low-side switching transistor in the second mode of operation.

10. The current sense amplifier of claim 8, wherein the high-side current sense amplifier further comprises:

a first transistor;

a first error amplifier for forcing a first voltage across the first transistor equal to a second voltage across the high-side switching transistor plus an offset voltage in the first mode of operation; and

a voltage source for generating the offset voltage.

11. The current sense amplifier of claim 10, wherein the first current through the high-side switching transistor is mirrored to the first transistor of the high side current sense amplifier.

12. The current sense amplifier of claim 11 wherein the current sense output is generated responsive to the mirrored current through the first transistor.

13. The current sense amplifier of claim 10, wherein the low-side current sense amplifier further comprises:

a second transistor;

a third transistor;

a second amplifier for forcing a third voltage across the second transistor equal to a fourth voltage across the low-side switching transistor plus a second offset voltage and generates a first current through the third transistor, wherein the second amplifier further mirrors the first current through the third transistor to equal a second current through the first transistor in the second mode of operation.

14. The current sense amplifier of claim 13 wherein the current sense output is generated responsive to the mirrored current through the first transistor.

15. A method for sensing a current in a voltage regulator, comprising:

sensing a first current through a high-side switching transistor of the voltage regulator in a first mode of operation when the high-side switching transistor is turned on and a low-side switching transistor is turned off;

generating a sensed current voltage signal responsive to the first current in the first mode of operation;

sensing a second current through a low-side switching transistor in a second mode of operation when the low-side switching transistor is turned on and the high-side switching transistor is turned off;

generating a current control signal responsive to the sensed second current; and

generating the sensed current voltage signal responsive to the current control signal in the second mode of operation.

16. The method of claim 15, further including:

connecting a high-side current sense amplifier to monitor the first current through the high-side switching transistor in the first mode of operation; and

connecting the high-side current sense amplifier and a low-side current sense amplifier to monitor the second current through the low-side switching transistor in the second mode of operation.

17. The method of claim 15, wherein sensing the first current further comprises forcing a first voltage across a first transistor in the high-side current sense amplifier equal to a second voltage across the high-side switching transistor plus an offset voltage in the first mode of operation.

18. The method of claim 17, further including mirroring the first current through the high-side switching transistor to the first transistor of the high side current sense amplifier.

19. The method of claim 18, wherein generating the current sense output further comprises generating the current sense output responsive to the mirrored current through the first transistor.

20. The method of claim 15, wherein sensing the second current further comprises:

forcing a third voltage across a transistor within the low-side current sense amplifier equal to a voltage across the low-side switching transistor plus a second offset voltage;

generating a first current through a second transistor within the low-side current sense amplifier; and

mirroring the first current through the second transistor within the low-side current sense amplifier to equal a second current through the first transistor within the high-side current sense amplifier in the second mode of operation.

21. The method of claim 20, wherein generating the current sense output further comprises generating the current sense output responsive to the mirrored current through the first transistor within the high-side current sense amplifier.

22. The method of claim 15, further including:

generating an error voltage responsive to the sensed current voltage signal, a reference voltage and a regulated output voltage;

generating a PWM control signal responsive to the error voltage signal and a ramp voltage signal;

generating drive control signals responsive to the PWM control signal; and

providing the regulated output voltage by controlling the high-side switching transistor and the low-side switching transistor responsive to the drive control signals and an input voltage.

23. A system, comprising:

a voltage regulator for generating a regulated output voltage responsive to an input voltage and drive control signals, the voltage regulator including a high-side switching transistor and a low-side switching transistor;

a driver circuit for generating the drive control signals responsive to a PWM control signal;

a PWM controller for generating the PWM control signal responsive to an error voltage and a ramp voltage;

a error amplifier for generating the error voltage responsive to a reference voltage, the regulated output voltage and a current sense voltage signal;

a high-side current sense amplifier for providing the current sense voltage signal, the high-side current sense amplifier generating the current sense voltage signal responsive to a first current sensed through the high-side switching transistor in a first mode of operation when the high-side switching transistor is turned on and the low-side switching transistor of the voltage regulator is turned off, the high-side current sense amplifier generating the current sense voltage signal responsive to a second current through the low-side switching transistor in a second mode of operation when the low-side switching transistor is turned on and the high-side switching transistor is turned off;

a low-side current sense amplifier for sensing the second current through the low-side switching transistor of the voltage regulator and generating a current control signal to the high-side current sense amplifier in the second mode of operation; and

a load coupled to the output of the voltage regulator.

24. The system of claim 23, wherein the load is selected from a group consisting of a processor, a memory, an input device, an output device and a storage device.