VOLTAGE REGULATOR WITH SWITCHING AND LOW DROPOUT MODES

• US 20150042300A1
• Filed: 08/07/2014
• Published: 02/12/2015
• Est. Priority Date: 08/09/2013
• Status: Active Grant

• Current Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Inventors: Peker, Arkadiy, Drexler, Bernard, Rajan, Reghu, Reshef, Tamir
• Granted Patent: US 10,320,290 B2
• Time in Patent Office: Days
• US Class Current: 323/274
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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 voltage regulator includes an input terminal, an output terminal, a control circuitry, a buck mode switching converter, and a low dropout regulator circuit. The buck mode switching converter is arranged to convert a voltage signal received at the input terminal to a first voltage signal at the output terminal responsive to a first predetermined signal output from the control circuitry. The buck mode switching converter includes an electronically controlled switch in communication with an energy storage element. The low dropout regulator circuit is coupled between the input terminal and the output terminal and includes a linear circuit and is arranged to control a voltage drop across the linear circuit so as to provide a second voltage signal at the output terminal responsive to a second predetermined signal output from the control circuitry.

Claims

1. A voltage regulator comprising:

an input terminal;

an output terminal;

a control circuitry;

a buck mode switching converter arranged to convert a voltage signal received at the input terminal to a first voltage signal at the output terminal responsive to a first predetermined signal output from the control circuitry, the buck mode switching converter comprising an electronically controlled switch in communication with an energy storage element; and

a low drop out regulator circuit coupled between the input terminal and the output terminal, the low drop out regulator circuit comprising a linear circuit and arranged to control a voltage drop across the linear circuit so as to provide a second voltage signal at the output terminal responsive to a second predetermined signal output from the control circuitry.

2. The voltage regulator of claim 1, wherein:

the first electronically controlled switch of the buck mode switching converter comprises a first transistor coupled between the input terminal and the output terminal;

the energy storage element is coupled between the first transistor and the output terminal;

the voltage regulator further comprises an error amplifier operable to generate an error signal based on a difference between an output voltage signal at the output terminal and a reference voltage signal;

the buck mode switching converter further comprises a switching circuit coupled to the first transistor and operable to provide a switching signal to the first transistor for charging the energy storage device using an the voltage signal received at the input terminal, the switching signal provided responsive to the error signal; and

wherein the linear circuit of the low dropout regulator circuit includes the first transistor and the linear circuit is operable to provide a linear signal based on the error signal for operating the first transistor in a linear mode responsive to the second predetermined signal output from said control circuitry.

3. The voltage regulator of claim 2, wherein the buck mode switching converter further comprises a second transistor coupled between the first transistor and a ground reference terminal, and the switching circuit comprises:

an oscillator operable to generate the switching signal;

a latch operable to receive the switching signal and generate a first drive signal coupled to a first gate terminal of the first transistor and a second drive signal, complimentary with respect to the first drive signal, coupled to a second gate terminal of the second transistor.

4. The voltage regulator of claim 3, wherein the control circuitry is operable to enable the latch in the buck mode and disable the latch in the low dropout mode.

5. The voltage regulator of claim 3, wherein the error amplifier comprises a current error amplifier operable to generate an output signal having a current having a magnitude based on the difference, and the voltage regulator further comprises:

a current source;

a switch coupled between the current source and a gain terminal of the error amplifier; and

logic operable to selectively close the switch during a startup period associated with entering the buck mode to increase a gain of the error amplifier.

6. The voltage regulator of claim 2, wherein the linear circuit comprises:

a second transistor coupled to a first gate terminal of the first transistor and having a gate input coupled to the error amplifier to receive the error signal and generate the linear signal responsive to the error signal; and

a switch coupled between the error amplifier and the gate input of the second transistor, wherein the control circuitry is operable to open the switch in the buck mode and close the switch in the low dropout mode.

7. The voltage regulator of claim 6, wherein the energy storage element comprises:

a capacitor coupled to the output terminal; and

an inductor coupled between the first transistor and the output terminal,

wherein the linear circuit further comprises a third transistor coupled between the first transistor and the output terminal, and the controller is operable to enable the third transistor to short the inductor in the low dropout mode.

8. The voltage regulator of claim 1, wherein the control circuitry is operable to assert one of the first predetermined signal output or the second predetermined signal output based on a comparison between the input voltage and the output voltage.

9. The voltage regulator of claim 1, wherein the control circuitry is operable to assert one of the first predetermined signal output or the second predetermined signal output based on an operating mode of a device receiving power from the voltage regulator.

10. A wireless sensor module, comprising:

a sensor; and

a voltage regulator coupled to receive an input voltage signal and operable to generate an output voltage signal for powering a radio, the voltage regulator comprising;

a first transistor coupled between an input terminal and an output terminal;

an energy storage element coupled to the output terminal; and

a control circuitry, comprising;

an error amplifier operable to generate an error signal based on a difference between an output voltage signal at the output terminal and a reference voltage signal;

a switching circuit coupled to the first transistor and operable to provide a switching signal to the first transistor for charging the energy storage device using an input voltage signal received on the input terminal based on the error signal; and

a linear circuit coupled to the first transistor and operable to provide a linear signal for operating the first transistor in a linear mode for charging the energy storage device using the input voltage signal based on the error signal; and

a controller operable to selectively enable the switching circuit in a buck mode for generating the output voltage signal or to enable the linear circuit in a low dropout mode for generating the output voltage signal responsive to an operating mode of the radio.

11. The wireless sensor module of claim 10, wherein the voltage regulator further comprises a second transistor coupled between the first transistor and a ground reference terminal, and the switching circuit comprises:

an oscillator operable to generate the switching signal;

a latch operable to receive the switching signal and generate a first drive signal coupled to a first gate terminal of the first transistor and a second drive signal, complimentary with respect to the first drive signal, coupled to a second gate terminal of the second transistor.

12. The wireless sensor module of claim 11, wherein the controller is operable to enable the latch in the buck mode and disable the latch in the low dropout mode.

13. The wireless sensor module of claim 11, wherein the error amplifier comprises a current error amplifier operable to generate an output signal having a current having a magnitude based on the difference, and the voltage regulator further comprises:

a current source;

a switch coupled between the current source and a gain terminal of the error amplifier; and

logic operable to selectively close the switch during a startup period associated with entering the buck mode to increase a gain of the error amplifier.

14. The wireless sensor module of claim 10, wherein the linear circuit comprises:

a second transistor coupled to a first gate terminal of the first transistor and having a gate input coupled to the error amplifier to receive the error signal and generate the linear signal responsive to the error signal; and

a switch coupled between the error amplifier and the gate input of the third transistor, wherein the controller is operable to open the switch in the buck mode and close the switch in the low dropout mode.

15. The wireless sensor module of claim 14, wherein the energy storage device comprises:

a capacitor coupled to the output terminal; and

an inductor coupled between the first transistor and the output terminal,

wherein the linear circuit further comprises a third transistor coupled between the first transistor and the output terminal, and the controller is operable to enable the third transistor to short the inductor in the low dropout mode.

16. The wireless sensor module of claim 10, wherein the controller is operable to operate the voltage regulator in the low dropout mode during a receive mode of the radio.

17. The wireless sensor module of claim 10, wherein the controller is operable to select one of the buck mode or the low dropout mode based on a comparison between the input voltage and the output voltage.

18. The wireless sensor module of claim 17, wherein the controller is operable to select the low dropout mode responsive to the input voltage signal being greater than the output voltage signal by less than a predetermined threshold.

19. A method for powering a wireless sensor module, comprising:

generating an output voltage signal at a voltage regulator for powering a sensor and a radio in the wireless sensor module; and

selectively operating the voltage regulator in one of a low dropout mode or a buck mode to generate the output voltage signal responsive to a control signal provided to the voltage regulator.

20. The method of claim 19, further comprising generating the control signal based on a difference between an input voltage signal to the voltage regulator and the output voltage.

21. The method of claim 20, further comprising generating the control signal to operate the voltage regulator in the buck mode responsive to the difference being greater than a predetermined threshold.

22. The method of claim 19, further comprising generating the control signal based on an operating mode of the radio.

23. The method of claim 21, wherein generating the control signal comprises generating the control signal to operating the voltage regulator in the low dropout mode responsive to the radio operating in a receive mode.