# US 11,444,578 B2 · Single-supply multi-level envelope tracker for RF power amplifier efficiency enhancement

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- Number: US 11,444,578 B2
- Document ID: US11444578B2
- Status: Granted
- Kind: B2
- Application number: 17/053,679
- Filed: 2019-05-07
- Published: 2021-04-22
- Granted: 2022-09-13
- Earliest claimed: 2018-05-07
- Assignees: The Regents of the University of Colorado, a body corporate
- Applicants: The Regents of the University of Colorado, a body corporate; Alma Mater Studiorum—Università di Bologna
- Inventors: Tommaso Cappello; Corrado Florian; Zorana Popovic
- Web page: https://patentgrep.com/patent/US11444578B2

## CPC

- H02M 7/483: Converters with outputs that each can have more than two voltages levels
- H03F 1/0227: {using supply converters}
- H03F 3/189: High-frequency amplifiers, e.g. radio frequency amplifiers
- H03F 3/245: {with semiconductor devices only}
- 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}
- H02M 7/4833: {Capacitor voltage balancing}
- H03F 2200/432: Two or more amplifiers of different type are coupled in parallel at the input or output, e.g. a class D and a linear amplifier, a class B and a class A amplifier
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H03F: AMPLIFIERS

## Abstract

A multi-level supply modulator for RF power amplifiers requires only a single independent voltage supply along with one or more flying capacitors to achieve multiple output levels. The flying capacitor is used to store the intermediate voltage level between the DC supply level and ground. A switch network is connected between the DC voltage supply and the power amplifier and is configured to provide power at variable, discrete DC voltages, for example the DC voltage supply level, ground, and a level halfway between the DC voltage supply level and ground. The flying capacitor is connected to switches in the switch network, and a sensing circuit detects the voltage across the flying capacitor and generates a feedback signal. Control circuitry controls the switch network (and thus the power supplied to the amplifier) based on the feedback signal.

## Claims

### Claim 1

A multi-cell supply modulator for providing variable-voltage DC power to an RF power amplifier comprising:
a single independent DC voltage supply supplying power at a DC supply voltage;
a switch network connected between the DC voltage supply and the power amplifier and configured to provide power at variable, discrete DC voltages to the power amplifier;
a flying capacitor connected to switches in the switch network;
a sensing circuit for detecting a flying voltage across the flying capacitor and providing a feedback signal based on the flying voltage;
control circuitry for controlling the switch network based upon the feedback signal;
wherein the switch network is configured to provide at least three different DC voltage levels to the RF power amplifier, and a second flying capacitor connected to switches in the switch network and wherein the switch network is configured to provide at least four different DC voltage levels to the RF power amplifier.

### Claim 2 (depends on 1)

The supply modulator of claim 1 wherein the variable discrete DC supply voltages substantially vary between the DC supply voltage, a ground voltage, and a level halfway between the DC supply voltage and the ground voltage.

### Claim 3 (depends on 1)

The supply modulator of claim 1 wherein the sensing circuit comprises a comparator with hysteresis.

### Claim 4 (depends on 1)

The supply modulator of claim 1 wherein the sensing circuit comprises a comparator with hysteresis.

### Claim 5 (depends on 1)

The supply modulator of claim 1 wherein the switch network comprises three nested half bridges.

### Claim 6 (depends on 1)

The supply modulator of claim 1 wherein the switch network comprises N nested half bridges and N−1 flying capacitors, and wherein the switch network is configured to provide at least N+1 different DC voltage levels to the RF power amplifier.

### Claim 7 (depends on 1)

The supply modulator of claim 1 wherein the switch network comprises three series half bridges.

### Claim 8 (depends on 1)

The supply modulator of claim 1 wherein the switch network comprises N series half bridges and N−1 flying capacitors, and wherein the switch network is configured to provide at least N+1 different DC voltage levels to the RF power amplifier.

### Claim 9 (depends on 1)

The supply modulator of claim 1 wherein the switch network, the flying capacitor, and the sensing circuit are integrated on a single chip.

### Claim 10 (depends on 9)

The supply modulator of claim 9 wherein the single chip is GaN architecture.

### Claim 11 (depends on 1)

The supply modulator of claim 1 further comprising a digital baseband configured to supply an IF signal to be upconverted to RF and amplified by the RF amplifier.

### Claim 12 (depends on 11)

The supply modulator of claim 11 wherein the sensing circuit comprises a comparator with hysteresis.

### Claim 13 (depends on 11)

The supply modulator of claim 11 wherein the digital baseband is further configured to perform digital predistortion on the IF signal.

### Claim 14 (depends on 11)

The supply modulator of claim 11 wherein the control logic and the digital baseband comprise a digital baseband processor.