US-12627226-B2 - Switched capacitor converter with tap-change capability

Abstract

A switched capacitor converter battery charging circuit can include an input that receives an input current, an output that delivers an integer multiple of the input current to a battery, a plurality of flying capacitor stages disposed between the input and output, and controller circuitry coupled to the flying capacitor stages that selectively enables or disables one or more of the flying capacitor stages to select the integer multiple responsive to a voltage supplied at the input. The flying capacitor stages can include a first plurality of flying capacitor stages forming a first phase of the converter and a second plurality of flying capacitor stages forming a second phase of the converter. The first and second phases can be operated in an interleaved manner to reduce current or voltage ripple. The converter can include three flying capacitor stages, providing for selection of integer multiples of 4×, 3×, 2×, or 1×.

Inventors

• Vijay G Phadke

Assignees

• APPLE INC.

Dates

Publication Date

20260512

Application Date

20221219

Claims (18)

1. 1 . A switched capacitor converter battery charging circuit comprising: an input configured to receive an input current; an output configured to deliver an integer multiple of the input current to a battery; a plurality of flying capacitor stages disposed between the input and output, wherein each of the plurality of flying capacitor stages comprises: a flying capacitor; a high side complementary switch pair; and a low side complementary switch pair; and controller circuitry coupled to the plurality of flying capacitor stages that selectively enables or disables one or more of the plurality of flying capacitor stages to select the integer multiple responsive to a voltage supplied at the input.
2. 2 . The switched capacitor converter battery charging circuit of claim 1 wherein the plurality of flying capacitor stages includes a first plurality of flying capacitor stages forming a first phase of the switched capacitor converter battery charging circuit and a second plurality of flying capacitor stages forming a second phase of the switched capacitor converter battery charging circuit, wherein the first and second phases are operated in an interleaved manner to reduce current or voltage ripple.
3. 3 . The switched capacitor converter battery charging circuit of claim 1 wherein the controller circuitry operates the high side complementary switch pair and the low side complementary switch pair of a selectively enabled flying capacitor stage to alternate between connecting the flying capacitor in series with the battery and in parallel with the battery.
4. 4 . The switched capacitor converter battery charging circuit of claim 3 wherein the controller operates switching devices of the respective complementary switch pairs with a 50% duty cycle.
5. 5 . The switched capacitor converter battery charging circuit of claim 1 wherein the controller circuitry operates selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging.
6. 6 . The switched capacitor converter battery charging circuit of claim 5 wherein the controller circuitry operates selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging by operating the low side complementary switch pair as always off, operating one of the high side complementary switch pair as always on, and operating another of the high side complementary switch pair with a 50% duty cycle.
7. 7 . The switched capacitor converter battery charging circuit of claim 5 wherein the controller circuitry disables all flying capacitor stages by operating a high side complementary switch pair as both always on and operating all other switching devices as always off.
8. 8 . The switched capacitor converter battery charging circuit of claim 1 wherein the switched capacitor converter battery charging circuit comprises three flying capacitor stages, providing for selection of integer multiples of 4×, 3×, 2×, or 1×.
9. 9 . A switched capacitor converter battery charging circuit comprising: an input configured to receive an input current; an output configured to deliver an integer multiple of the input current to a battery; a plurality of phases with each phase comprising a plurality of flying capacitor stages disposed between the input and output, wherein the plurality of phases are operated in an interleaved manner to reduce current or voltage ripple, wherein each of the plurality of flying capacitor stages comprises; a flying capacitor; a high side complementary switch pair; and a low side complementary switch pair; and controller circuitry coupled to the plurality of flying capacitor stages that selectively enables or disables one or more of the plurality of flying capacitor stages to select the integer multiple responsive to a voltage supplied at the input.
10. 10 . The switched capacitor converter of claim 9 wherein the controller circuitry operates the high side complementary switch pair and the low side complementary switch pair of a selectively enabled flying capacitor stage to alternate between connecting the flying capacitor in series with the battery and in parallel with the battery.
11. 11 . The switched capacitor converter of claim 10 wherein the controller operates switching devices of the respective complementary switch pairs with a 50% duty cycle.
12. 12 . The switched capacitor converter of claim 9 wherein the controller circuitry operates selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging.
13. 13 . The switched capacitor converter of claim 12 wherein the controller circuitry operates selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging by operating the low side complementary switch pair as always off, operating one of the high side complementary switch pair as always on, and operating another of the high side complementary switch pair with a 50% duty cycle.
14. 14 . The switched capacitor converter of claim 12 wherein the controller circuitry disables all flying capacitor stages by operating a high side complementary switch pair as both always on and operating all other switching devices as always off.
15. 15 . The switched capacitor converter of claim 9 wherein the switched capacitor converter comprises three flying capacitor stages, providing for selection of integer multiples of 4×, 3×, 2×, or 1×.
16. 16 . A method of operating a switched capacitor converter battery charger, the method comprising: selectively enabling or disabling one or more flying capacitor stages of the switched capacitor converter to select an integer multiple applied to an input current of the battery charger to produce an output current supplied to the battery, wherein each of the one or more flying capacitor stages comprises: a flying capacitor; a high side complementary switch pair; and a low side complementary switch pair; wherein the integer multiple is selected in response to an input voltage of the switched capacitor converter battery charger.
17. 17 . The method of claim 16 wherein selectively enabling one or more flying capacitor stages comprises operating a plurality of switching devices with a 50% duty cycle to alternate between connecting flying capacitors of the one or more flying capacitor stages in series with the battery and in parallel with the battery.
18. 18 . The method of claim 16 wherein selectively disabling one or more flying capacitor stages comprises operating one or more switching devices as always on and one or more switching devices always off to prevent flying capacitors of the one or more flying capacitor stages from charging and discharging.

Description

BACKGROUND Switched capacitor converters, also known by various other names such as “SwCap converters” or “flying capacitor converters” or simply “charge pumps” may be used in fast charging of the battery of portable devices, for example using a USB-C/USB-PD Programmable Power Source (PPS). Use of switched capacitor converters can overcome a current-carrying limitation of charging port of the adapter and/or charging cable. For example, some devices may have a current limit of about 3 A, while higher current levels may be desired for battery charging. In such a charging configuration, an external AC/DC adapter may be operated as effectively a current source. The current from the adapter can be provided to the switched capacitor converter located in the portable device. A capacitor can placed at the input of the switched capacitor converter for filtering purpose. The switched capacitor converter can have a transformer like operation, i.e., it steps down the output voltage, while stepping up the output current in the same proportion. Thus, according to the example, the 3 A current that is available from the AC/DC adapter can be stepped up based on the switched capacitor converter step down ratio. In this mode, the switched capacitor converter can be considered as a current multiplier that delivers higher current to the battery for fast charging. Some switched capacitor converters may not be capable of independent voltage regulation. In other words, there may be a fixed proportional relationship between the input voltage and the output voltage. In the given example of a battery charger, the voltage at the input of the switched capacitor converter is an integer multiple of the battery voltage. Thus, the AC/DC adapter can regulate the charging current with the output voltage of the adapter (input voltage of the switched capacitor converter) being effectively clamped at a level based on the conversion ratio of the switched capacitor converter. SUMMARY One aspect of such configurations that may be undesirable in some applications is the fixed ratio between the battery charging voltage and input voltage into the switched capacitor converter. Thus, it may be desirable to provide a switched capacitor converter that can operate with different conversion ratios and therefore accommodate a wider range of input voltages (e.g., different voltages supplied by an AC/DC adapter). A switched capacitor converter battery charging circuit can include an input configured to receive an input current, an output configured to deliver an integer multiple of the input current to a battery, a plurality of flying capacitor stages disposed between the input and output, and controller circuitry coupled to the plurality of flying capacitor stages that selectively enables or disables one or more of the flying capacitor stages to select the integer multiple responsive to a voltage supplied at the input. The plurality of flying capacitor stages can include a first plurality of flying capacitor stages forming a first phase of the converter and a second plurality of flying capacitor stages forming a second phase of the converter. The first and second phases can be operated in an interleaved manner to reduce current or voltage ripple. Each of the plurality of flying capacitor stages can include a flying capacitor, a high side complementary switch pair, and a low side complementary switch pair. The switched capacitor converter can include three flying capacitor stages, providing for selection of integer multiples of 4×, 3×, 2×, or 1×. The controller can operate the high side complementary switch pair and the low side complementary switch pair of a selectively enabled flying capacitor stage to alternate between connecting the flying capacitor in series with the battery and in parallel with the battery. Switching devices of the respective complementary switch pairs can be operated with a 50% duty cycle. The controller can operate selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging. The controller can operate selected switching devices of a selectively disabled flying capacitor stage as always on or always off to prevent a corresponding flying capacitor from charging and discharging by operating the low side complementary switch pair as always off, operating one of the high side complementary switch pair as always on, and operating another of the high side complementary switch pair with a 50% duty cycle. The controller can disable all flying capacitor stages by operating a high side complementary switch pair as both always on and operating all other switching devices as always off. A switched capacitor converter battery charging circuit can include an input configured to receive an input current, an output configured to deliver an integer multiple of the input current to a battery, a plurality of phases each phase comprising a