AUTO CASCODE BUCK VOLTAGE CONVERTER

• US 20120007572A1
• Filed: 07/06/2010
• Published: 01/12/2012
• Est. Priority Date: 07/06/2010
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Oddoart, Ludovic
• Granted Patent: US 8,797,009 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H03K 17/102 in field-effect transistor switches
• CPC Class Codes: H03K 17/6872 using complementary field-effect transistors
• 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 converter includes a power switch having respective charging and discharging control terminals, and an output terminal coupled to a series connected inductor and capacitor. The voltage converter also includes a charging switch coupled to the charging control terminal of the power switch, a discharging switch coupled to the discharging control terminal of the power switch, and a feedback circuit coupling the power switch, charging switch and discharging switch to a node at which the capacitor and inductor are connected. During a charging phase, the charging switch couples the capacitor to the charging control terminal of the power switch, and during a discharging phase, the discharging switch couples the capacitor to the discharging control terminal of the power switch.

Claims

1. A voltage converter comprising:

a power switch, coupled between a source of battery potential and a source of reference operating potential, the power switch having respective charging and discharging control terminals configured to receive respective charging and discharging control signals, and an output terminal;

an inductor connected in series with a capacitor, the series connected inductor and capacitor being coupled between the output terminal of the power switch and the source of reference operating potential;

a charging switch having an output terminal coupled to the charging control terminal of the power switch;

a discharging switch having an output terminal coupled to the discharging control terminal of the power switch; and

a feedback circuit connecting a node at which the capacitor and inductor are connected to the power switch, charging switch and discharging switch,

wherein during a charging phase, the charging switch electrically couples the capacitor to the charging control terminal of the power switch, whereby the power switch charges the inductor, and

wherein during a discharging phase, the discharging switch electrically couples the capacitor to the discharging control terminal of the power switch, whereby the power switch discharges the inductor.

2. The voltage converter of claim 1, further comprising:

a voltage regulator circuit having an output terminal coupled to the capacitor, whereby the voltage regulator is turned on during a pre-charging phase to charge the capacitor to a predetermined value, and the power switch is turned off.

3. The voltage converter of claim 2, further comprising:

a regulator power switch for turning off the voltage regulator when the capacitor voltage reaches the predetermined value.

4. The voltage converter of claim 2, further comprising:

an isolation switch for, during the charging phase, routing the electrical current flowing through the charging switch through the feedback circuit to the capacitor, the isolation switch blocking the electrical current from flowing through the voltage regulator circuit.

5. The voltage converter of claim 2, further comprising:

an isolation switch for, during the discharging phase, routing electrical current flowing through the capacitor through the feedback circuit to the discharging switch, the isolation switch blocking the electrical current from flowing through the voltage regulator circuit.

6. The voltage converter of claim 1, wherein

the power switch includes a charging cascode switch and a discharging cascode switch having respective charging and discharging control terminals connected to the feedback circuit.

7. A voltage converting method of operating a voltage converter, the voltage converter comprising a charging switch, a discharging switch, a power switch coupled between a source of battery potential and a source of reference operating potential, a series-connected inductor and capacitor coupled between the power switch and the source of reference operating potential, and a feedback circuit coupling the charging switch, the discharging switch and the power switch to a node at which the capacitor is connected to the inductor, the voltage converting method comprising:

applying, via the feedback circuit and during a charging phase, a capacitor voltage from the capacitor to a charging control terminal of the power switch, causing the power switch to apply a charging potential from the source of battery potential to the inductor; and

applying, via the feedback circuit and during a discharging phase, the capacitor voltage from the capacitor to a discharging control terminal of the power switch, causing the power switch to apply a discharging potential from the source of reference operating potential to the inductor.

8. The method of claim 7 wherein the voltage converter further includes a start-up regulator having an output terminal connected to the feedback circuit, the method further comprising:

applying potentials to the charging and discharging control terminals of the power switch to isolate the inductor from the charging and discharging potentials;

applying power to the startup regulator; and

pre-charging the output capacitor to a predetermined voltage responsive to the predetermined voltage provided by the startup regulator.

9. The method of claim 8, further comprising the steps of:

turning off the power to the startup regulator when the capacitor voltage reaches the predetermined voltage; and

applying the predetermined voltage from the capacitor to the charging and discharging control terminals of the power switch.

10. The method of claim 7, further comprising the steps of:

alternately applying the charging and discharging potentials to the inductor responsive to an error signal representing a difference between the capacitor voltage and a reference voltage.

11. The method of claim 7, further comprising the steps of:

routing electrical current, flowing from the charging switch, through the feedback circuit to a load coupled to the capacitor; and

producing by the capacitor voltage, electrical current flowing through the discharging switch via the feedback circuit.

12. A voltage converter comprising:

a power switch, coupled between a source of battery potential and a source of reference operating potential, the power switch having respective charging and discharging control terminals configured to receive respective charging and discharging control signals, and an output terminal;

an inductor connected in series with a capacitor, the series connected inductor and capacitor being coupled between the output terminal of the power switch and the source of reference operating potential;

a low voltage charging switch having an output terminal coupled to the charging control terminal of the power switch;

a high voltage charging switch having an output terminal coupled to the charging control terminal of the power switch;

a discharging switch having an output terminal coupled to the discharging control terminal of the power switch;

a controller coupled to control terminals of the low voltage and high voltage charging switches, the controller being coupled to the source of battery potential for controlling the low and high voltage charging switches; and

a feedback circuit connecting the power switch, low voltage charging switch, high voltage charging switch and discharging switch to a node at which the capacitor is connected to the inductor,

wherein, during a low voltage charging phase, when a battery potential provided by the source of battery potential is determined by the controller to be less than or equal to a predetermined threshold, the low voltage charging switch couples the source of reference operating potential to the charging control terminal of the power switch, whereby the power switch charges the inductor,

wherein, during a high voltage charging phase, when the battery potential is determined by the controller to be greater than the predetermined threshold, the high voltage charging switch couples the capacitor, via the feedback circuit, to the charging control terminal of the power switch, whereby the power switch charges the inductor, and

wherein, during a discharging phase, the discharging switch couples the capacitor, via the feedback circuit, to the discharging control terminal of the power switch, whereby the power switch discharges the inductor.

13. The voltage converter of claim 12, further comprising:

a voltage regulator circuit having an output terminal coupled to the capacitor;

wherein, during a pre-charging phase, the voltage regulator is turned on to charge the capacitor to a predetermined value, and the power switch, low voltage charging switch, high voltage charging switch and discharging switch are turned off, and

wherein when the capacitor voltage reaches the predetermined value, the voltage regulator is turned off and the power switch, low voltage charging switch, high voltage charging switch and discharging switch are turned on.

14. The voltage converter of claim 12, further comprising:

a battery monitor coupled to the battery for determining if the battery voltage is less than or equal to a predetermined value and for providing a control signal to the controller to control the low voltage charging switch and the high voltage charging switch.

15. The voltage converter of claim 14, further wherein:

the battery monitor is coupled to the controller,

when the battery voltage is less than or equal to the predetermined value, the controller controls the low voltage charging switch to couple the source of reference operating potential to the charging control terminal of the power switch, and

when the battery voltage is greater than the predetermined value, the controller controls the high voltage charging switch to couple the capacitor to the charging control terminal of the power switch.

16. The voltage converter of claim 14, further comprising:

a selector switch for controlling the low voltage charging switch and the power switch, the selector switch coupled to the battery monitor,

when the battery voltage is less than or equal to the predetermined value, the selector switch controls the low voltage charging switch and power switch to turn fully on, and

when the battery voltage is greater than the predetermined value, the selector switch controls the low voltage charging switch and power switch to turn partially on.

17. The voltage converter of claim 14, further comprising:

a pulse width modulator (PWM) coupled to the controller,

wherein the controller selectively applies PWM signals from the PWM controller to the control terminals of the low voltage charging switch and high voltage charging switch responsive to the output of the battery monitor to control the charging of the capacitor.

18. The voltage converter of claim 14, wherein the power switch includes a low voltage power switch and high voltage power switch having respective charging control terminals, and respective output terminals coupled to the inductor.

19. The voltage converter of claim 18, wherein

the output terminal of the low voltage charging switch is coupled to the charging control terminal of the low voltage power switch, and the output terminal of the high voltage charging switch is coupled to the charging control terminal of the high voltage power switch.

20. The voltage converter of claim 19, wherein

when the battery voltage is less than or equal to the predetermined value, the controller controls the low voltage charging switch to control the low voltage power switch to couple the inductor to the source of battery potential,

when the battery voltage is greater than the predetermined value, the controller controls the high voltage charging switch to control the high voltage power switch to couple the inductor to the source of battery potential, and

wherein the low voltage power switch has a lower impedance than the high voltage power switch.

21. The voltage converter of claim 12, wherein the low voltage charging switch has a lower impedance than the high voltage charging switch.

22. The voltage converter of claim 12, wherein

the power switch includes a charging cascode switch and a discharging cascode switch having respective charging and discharging control terminals connected to the feedback circuit.