# US 10,483,914 B2 · Very high fidelity audio amplifier

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- Number: US 10,483,914 B2
- Document ID: US10483914B2
- Status: Granted
- Kind: B2
- Application number: 15/322,936
- Filed: 2015-06-30
- Published: 2017-07-20
- Granted: 2019-11-19
- Earliest claimed: 2014-06-30
- Assignees: Devialet
- Applicants: Devialet
- Inventors: Pierre-Emmanuel Calmel
- Web page: https://patentgrep.com/patent/US10483914B2

## CPC

- H03F 1/02: Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
- H03F 3/181: Low-frequency amplifiers, e.g. audio preamplifiers
- H03F 3/183: with semiconductor devices only
- H03F 3/217: Class D power amplifiers; Switching amplifiers
- H03F 3/45475: {using IC blocks as the active amplifying circuit}
- H03F 2200/03: the amplifier being designed for audio applications
- H03F 2200/351: Pulse width modulation being used in an amplifying circuit
- H03F 2200/391: the output circuit of an amplifying stage comprising an LC-network
- 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 2200/534: Transformer coupled at the input of an amplifier
- H03F: AMPLIFIERS

## Abstract

Disclosed is the audio amplifier comprising an input for an audio signal to be amplified and an output for powering a load on the basis of the amplified audio signal; a generator of reference voltage of very high linearity and low output impedance, able to receive, as input, the audio signal to be amplified; a power current generator comprising a power voltage generator whose output is connected to the output of the reference voltage generator through a coupling impedance. The coupling impedance comprises two coupling inductances mounted in series between the output of the reference generator and the output of the power voltage generator and an attenuation impedance linking a mid-point between the two coupling inductances and a reference potential, wherein the attenuation impedance includes an attenuation inductance.

## Claims

### Claim 1

An audio amplifier comprising:
an input for an audio signal to be amplified and an output for powering a load on the basis of the amplified audio signal;
a generator of reference voltage of very high linearity and low output impedance, able to receive, as input, the audio signal to be amplified;
a power current generator comprising a power voltage generator whose output is connected to the output of the reference voltage generator through a coupling impedance;
the coupling impedance comprising two coupling inductances mounted in series between the output of the reference generator and the output of the power voltage generator and an attenuation impedance linking a mid-point between the two coupling inductances and a reference potential,
wherein the attenuation impedance comprises an attenuation inductance.

### Claim 2 (depends on 1)

The amplifier according to claim 1, wherein the value of the attenuation inductance is much lower than the individual value of the two coupling inductances.

### Claim 3 (depends on 2)

The amplifier according to claim 2, wherein this value of the attenuation inductance is less than 1/10th of the individual value of the coupling inductances.

### Claim 4 (depends on 1)

The amplifier according to claim 1, wherein the attenuation impedance comprises a capacitor mounted in series with the attenuation inductance.

### Claim 5 (depends on 4)

The amplifier according to claim 4, wherein the capacity of the capacitor is such that the ratio at 1/|jCω| is much lower than the value |jL3ω| of the inductance attenuation impedance L3, where ω is the angular frequency of the signal, for angular frequency values comprised between 1/10·2π·fPWM and 10·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 6 (depends on 5)

The amplifier according to claim 5, wherein the capacity of the capacitor is such that the ratio at 1/|jCω| is greater than the impedance of the load, where ω is the angular frequency of the signal less than 1/10·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 7 (depends on 1)

The amplifier according to claim 1, wherein the attenuation impedance comprises a resistance mounted in series with the attenuation inductance.

### Claim 8 (depends on 7)

The amplifier according to claim 7, wherein the value of the resistance is greater than |jL2ω|, where L2 is the minimum value of the coupling inductance and ω is the angular frequency of the signal, for angular frequency values below 1/100·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 9 (depends on 1)

The amplifier according to claim 1, wherein the attenuation impedance is a RLC circuit.

### Claim 10 (depends on 1)

The amplifier according to claim 1, wherein the attenuation impedance comprises a resistance mounted in parallel with the attenuation inductance.

### Claim 11 (depends on 10)

The amplifier according to claim 10, wherein the value of the resistance is significantly greater than |jL3ω|, where L3 is the value of the inductance and ω is the angular frequency of the signal, for angular frequency values comprised between 1/10·2π·fPWM and 10·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 12 (depends on 1)

The amplifier according to claim 1, wherein the attenuation impedance comprises resistance mounted in parallel with the capacitor.

### Claim 13 (depends on 1)

The amplifier according to claim 1, wherein the power current generator comprises several power voltage generators receiving, as input, the same phase-shifted signals and at least one autotransformer connecting the outputs of the power voltage generators to one another and whose output is connected to the coupling impedance.

### Claim 14 (depends on 4)

The amplifier according to claim 4, wherein the capacity of the capacitor is such that the ratio at 1/|jCω| is less than 1/10th of the value |jL3ω| of the inductance attenuation impedance L3, where ω is the angular frequency of the signal, for angular frequency values comprised between 1/10·2π·fPWM, fPWM and 10·2πfPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 15 (depends on 5)

The amplifier according to claim 5, wherein the capacity of the capacitor is such that the ratio at 1/|jCω| is more than 10 times the impedance of the load, where ω is the angular frequency of the signal less than 1/10·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 16 (depends on 7)

The amplifier according to claim 7, wherein the value of the resistance is more than 10 times |jL2ω|, where L2 is the minimum value of the coupling inductance and ω is the angular frequency of the signal, for angular frequency values below 1/100·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.

### Claim 17 (depends on 10)

The amplifier according to claim 10, wherein the value of the resistance is greater than ten times |jL3ω|, where L3 is the value of the inductance and ω is the angular frequency of the signal, for angular frequency values comprised between 1/10·2π·fPWM and 10·2π·fPWM, fPWM being the fundamental frequency of a current ripple in the coupling inductance.