High Performance Audio Amplifier

Abstract

The invention relates to a high-performance audio amplifier (102) intended to control at least one loudspeaker (R44), the amplifier comprising a preamplification stage (301) receiving an input signal (S1), a power amplification stage (302) connected to the preamplification stage (301) and a feedback delivering an image of an output signal (3) to the preamplification stage (301), the power amplification stage (302) comprising two power supply circuits (155a, 155b) including MOSFET transistors (M1, M2). The invention is characterized in that it comprises a sub-circuit for assisting in charging, a sub-circuit for assisting in discharging and a voltage shift sub-circuit for the MOSFET transistors (M1, M2).

Description

[Technical field]

[0001] The present invention relates to the field of amplifiers, and in particular to high-power audio amplifiers intended to control at least one loudspeaker.

[0002] High power amplifiers have particular application in providing sound in recording studios or concert halls: they are particularly used to power electrodynamic loudspeakers.

[0003] The present invention advantageously makes it possible to obtain a high-power audio amplifier having better efficiency than prior art amplifiers while guaranteeing low distortion. [Background technology]

[0004] Conventionally, a high-power amplifier includes at least one active component, such as a transistor or a tube, that makes it possible to amplify the power of a signal received as input while preserving the shape of the input signal.

[0005] A high-power amplifier circuit generally comprises a preamplification stage followed by a power amplification stage. More precisely, the output of the power amplification stage is fed back to the preamplification stage, which detects over time the difference between the output signal and the input signal, for example by means of a differential pair. This difference detected in the preamplification stage is then amplified in the power amplification stage to form an output signal, which is conventionally transmitted to at least one loudspeaker.

[0006] 1 illustrates a high-power amplifier 100 whose input signal is applied at point S1. The output of the high-power amplifier 100 powers a loudspeaker, represented by resistor R44 connected between point 3 and ground.

[0007] The diagram of the high-power amplifier 100 is symmetrical: it comprises an upper part 140a and a lower part 140b, the upper part 140a amplifying the positive half-wave of the input signal S1 and the lower part 140b amplifying the negative half-wave of the input signal S1.

[0008] In the example of FIG. 1, the high power amplifier 100 is powered by a single voltage level of + / -65V.

[0009] The preamplification stage 201 includes two differential pairs 110a, 110b, each including two transistors Q1, Q2 and Q3, Q4, assembled in mirror of each other, such that the emitters of the transistors Q1, Q2 are connected to the -65V power bus via resistors R2, R3 and a first constant current source I, while the emitters of the transistors Q3, Q4 are connected to the +65V power bus via resistors R4, R5 and a second current source I of the same value.

[0010] The collectors of transistors Q2, Q4 are connected to the +65V and -65V power buses, respectively, while the collectors of transistors Q1, Q3 are connected to the +65V and -65V power buses through resistors R1, R11, respectively. In the absence of feedback, the gain of the preamplifier stage 201 depends on the resistor ratios R1 / R2 and R11 / R4.

[0011] The bases of the transistors Q1 and Q3 and the bases of the transistors Q2 and Q4 are connected to each other and are powered by the input signal S1. The bases of the transistors Q2 and Q4 are connected to the loudspeaker R44 via the resistor R18 to form a feedback applied to the preamplification stage. The collectors of the transistors Q1 and Q3 ensure the coupling of the preamplification stage 201 with the power amplification stage 202.

[0012] The power amplifier stage 202 includes two transistors Q8, Q9 connected by their respective bases to the preamplifier stage 201 through resistors R23, R57. A voltage source T1 is also placed between resistors R23 and R57 to bias the transistors Q8, Q9 in class AB. This voltage source T1 makes it possible to provide a voltage equal to the sum of the voltages required to turn on the transistors Q8 and Q9.

[0013] Also, the transistors Q8, Q9 are connected by their collectors to the +65V and -65V power buses, respectively. The emitters of the transistors Q8, Q9 are connected to the loudspeaker R44 through resistors R16, R17. These resistors R16, R17 are added to control the quiescent current (i.e. the value of the current conducted by the amplifier when it receives no input signal). Without these resistors R16, R17, the quiescent current would depend on the characteristics and temperature of the transistors Q8 and Q9, which would be prohibited.

[0014] In addition, the circuit in FIG. 1 has a particularity in the bases of the transistors Q2 and Q4. In fact, the latter is connected to a protection line 403, which includes a resistor R28 assembled in series with a capacitor C4 connected to ground. This assembly is a voltage divider, such that the voltage at point S2 is equal to R28 / (R18+R28) multiplied by the voltage of the output signal 3 in AC. In fact, the capacitor C4 behaves like a short circuit when the voltage through the circuit is AC. On the other hand, when the voltage through the circuit is DC, the capacitor C4 behaves like an open circuit. In this case, the output signal 3 of the high-power amplifier 100 is connected directly to point S2. The voltage gain of the high-power amplifier 100 is then equal to 1, which makes it possible to limit possible undesirable DC components on the voltage applied to the terminals of the loudspeaker R44.

[0015] In this type of amplifier, the voltage measured at point S1 relative to ground and the voltage measured at point S2 relative to ground are equal. In other words, the gain of the high power amplifier 100 is equal to the ratio of the resistor values ​​(R18+R28) / R28.

[0016] Thus, Figure 1 illustrates a high output voltage amplifier, and there is another category, the high output current amplifier, as shown in Figure 2.

[0017] This category of high power current amplifiers 101 has the same topology as for the high output voltage amplifiers 100 , namely a preamplification stage 201 coupled to an amplification stage 203 .

[0018] 1, a current measuring resistor R6 is inserted between the loudspeaker R44 and ground. Furthermore, the current amplifier 101 does not have a protection line 403. The bases of the transistors Q2 and Q4 are connected to an interconnection point P1 that is located between the resistor R6 and the loudspeaker R44.

[0019] In this configuration, the image of the current applied at point S2 in Figure 3 thus intersects loudspeaker R44. It follows that the transconductance (i.e. the ratio between the output current passing through loudspeaker R44 and the input voltage applied at point S1 of amplifier 101) is equal to 1 / R6 A / V. For a loudspeaker with impedance Z, the voltage gain is Z / R6.

[0020] The voltage or current amplifier assemblies are therefore similar, especially with regard to the preamplification and power amplification stages. They only differ with regard to the loudspeaker connections and feedback.

[0021] In the prior art below, other classes of amplifiers will be described with reference to voltage amplifiers, however the invention is not limited to this type of amplifier.

[0022] A class system can be used to characterize different high power amplifier topologies. The class system assigns letters based on the relationship between the shape of the input signal and the shape of the output signal, and based on the duration that active components are used during amplification of the input signal.

[0023] Among the existing amplifier classes, class A amplifiers have a topology in which the active components conduct a high current, approximately 50% of the maximum output current, in the absence of an input signal. This is called the quiescent current. During modulation, the quiescent current is superimposed on top of the output current. This type of amplifier is capable of providing good sound quality, but it has the disadvantage of generating significant heat dissipation. The energy efficiency (defined by the ratio between the useful output power and the absorbed power) of this class of amplifiers is therefore approximately 10%.

[0024] Class B amplifiers are characterized by a topology in which, when a sinusoidal input signal is applied as input, the active components conduct for more than 50% of the input signal period. For this class of amplifiers, the quiescent current is zero. The efficiency of this type of amplifier is higher than that of class A amplifiers, but the distortion characteristics of the output signal are significantly deteriorated compared to class A amplifiers. Class B amplifiers therefore produce a poorer quality of sound. Nowadays, manufacturers rarely use this class of amplifiers.

[0025] Class AB amplifiers are characterized by a topology in which the active components conduct more than 100% of the input signal period, but with a low quiescent current of approximately 1% of the maximum output current. This type of amplifier has a higher energy efficiency than class A amplifiers, typically between 30% and 50%, but a lower sound quality. Class AB amplifiers are therefore a good compromise between performance and energy efficiency.

[0026] For class D amplifiers, a technology is used in which active components are operated like switches. The signal is then converted by pulse width modulation. This system increases the energy efficiency to approximately 70%. On the other hand, the output signal contains more noise and distortion, and it is difficult to reproduce high frequencies by this class of amplifier.

[0027] Class G amplifiers have several power buses and can be switched from one to another depending on the power output requirements, which allows to increase the energy efficiency by reducing the power dissipated in the active components.

[0028] Class H amplifiers use a power bus whose supply voltage "snaps" or is modulated by the input signal. Typically, they have two power buses, like Class G's, but only the highest supply voltage is modulated. Modulated power supplies are commonly achieved using Class D amplifiers.

[0029] The subject of the present invention is particularly concerned with these last two categories of amplifiers.

[0030] 3 illustrates an upper part of the power amplifier stage 204. The latter is connected to a power supply circuit 150. Naturally, this power amplifier stage also includes a lower part (not shown) mirroring the upper part with an equivalent power supply circuit. Likewise, the circuit also includes a preamplifier stage, which is connected, for example, to an independent power supply or to a powerful power bus, which is also connected to the power supply circuit 150.

[0031] The power supply circuit 150 makes it possible to select a power level of the power amplifier stage 204 that is adapted to the amplifier power requirements. Thus, when the amplifier voltage is greater than a threshold, a first, stronger power bus must be used, whereas when the amplifier voltage is lower than this threshold, a second, weaker power bus can be used. The use of a lower power bus aspect improves the overall efficiency of the amplifier compared to class A, B and AB amplifiers.

[0032] Furthermore, the power supply circuit 150 has an independent structure for the preamplification stage 201 and the power amplification stage 204. In the example of Fig. 3, the power amplification stage 204 includes a transistor Q10, whose base is connected to the emitter of the transistor Q8. This so-called "Darlington" configuration allows to increase the current gain. The emitters of the transistors Q8 and Q10 are coupled to the loudspeaker R44 by their respective resistors R16 and R19. They have respective quiescent currents, for example, equal to 6 mA for the transistor Q8 and 75 mA for the transistor Q10.

[0033] The power amplifier stage 204 is connected to a power supply circuit 150 at the collectors of the transistors Q8 and Q10. This power supply circuit 150 is connected to two voltage buses with separate levels V+, V++. It therefore makes it possible to select one or the other of these voltage levels depending on the amplification requirements. Typically, the first power bus delivers 65V and the second power bus delivers 35V. The second power bus is intended to be used to power the power amplifier stage 204 when the output signal to be generated does not have a very high voltage (typically less than 32V).

[0034] Due to the relatively low current passing through transistor Q8 (typically less than 10% of the current passing through transistor Q10), the collector of transistor Q8 can be directly connected to the first power bus V++, which does not cause significant additional power dissipation. This embodiment can improve the stability of the amplifier, whose operation as a current amplifier tends to be weakened.

[0035] To select the appropriate voltage level, the MOSFET transistor M1 is connected by its drain directly to the first power bus V++ and by its source through a fourth diode D3 to the second power bus V+. The MOSFET transistor M1 typically switches about a threshold of 27V, and then it operates linearly above this threshold. It passes the first power bus V++ when a control voltage greater than the threshold is applied to it. This voltage is controlled by the association of a first diode D8, D10 (which is connected between the gate of the MOSFET transistor M1 and the loudspeaker R44) and a second resistor R8, R27 (which is connected between the drain and gate of the MOSFET transistor M1).

[0036] Diode D15 is connected between the collector of transistor Q10 and loudspeaker R44, with the cathode of the diode connected to the collector of transistor Q10.

[0037] The different signals acquired by this assembly are illustrated in FIG.

[0038] Thus, the signal numbered 1 in Figures 3 and 4 represents the gate signal of the MOSFET transistor M1. The output signal numbered 3 in Figures 3 and 4 represents the output signal of the amplifier, i.e. the signal at the terminals of the loudspeaker R44. The output signal numbered 2 in Figures 3 and 4 represents the output signal of the power supply circuit 150. We therefore notice that the output signal 3 is distorted. In fact, the top of the sine curve is flattened and a shift occurs around 27 μs. This saturation of the output signal 3 is explained by the fact that the supply voltage of the MOSFET transistor M1 is insufficient for the amplifier to be able to correctly deliver an output voltage.

[0039] Similarly, signal 2 has an abnormal voltage peak between 40 μs and 47 μs, which corresponds to an overvoltage at the gate of MOSFET transistor M1, leading to a loss of power and a degradation of the amplifier's efficiency. Summary of the Invention [Problem to be solved by the invention]

[0040] The technical problem that the invention proposes to solve is therefore to obtain a high-power audio amplifier that makes it possible to limit the distortions identified on the signal, thus improving the efficiency of the amplifier and reducing its saturation. [Means for solving the problem]

[0041] To solve this problem, the present invention proposes a power supply circuit including a MOSFET transistor controlled by a sub-circuit for assisting charging, a sub-circuit for assisting discharging and a voltage shifting sub-circuit, which makes it possible to obtain a better efficiency of the amplifier while limiting the saturation and distortion of the amplifier output signal.

[0042] In other words, the invention relates to a high-power audio amplifier intended to control at least one loudspeaker, comprising: a preamplification stage for receiving an input signal; - a power amplification stage connected to a preamplification stage and providing an output signal intended to power said at least one loudspeaker, the preamplification stage and the power amplification stage having mirror-mounted upper and lower parts; - feedback to provide an image of the output signal to a preamplification stage; an upper power supply circuit connected to an upper part of the power amplification stage and enabling it to be powered by a first or a second power bus; a lower power supply circuit, the lower power supply circuit being connected to a lower part of the power amplification stage and enabling it to be powered by a first or a second power bus; Including, - for a high power audio amplifier, each power supply circuit includes a MOSFET transistor and a monitoring means, the MOSFET transistor being controlled by the monitoring means to perform switching between one or the other of two power buses, the MOSFET transistor being connected to the second power bus via a fourth diode, a first terminal of the fourth diode being connected to a source of the MOSFET transistor, and a drain of the MOSFET transistor being connected to the first power bus.

[0043] The present invention relates to a power supply circuit, - a sub-circuit for assisting charging the MOSFET transistor, the sub-circuit for assisting charging including at least a first resistor, a first terminal of the first resistor being connected to a gate of the MOSFET transistor and a second terminal of the first resistor being connected to an interconnection point; - a sub-circuit for assisting in discharging said MOSFET transistor, the sub-circuit for assisting in discharging including at least second and third resistors and a bipolar transistor, the base of the bipolar transistor being connected to a first terminal of the third resistor, the emitter of the bipolar transistor being connected to the gate of the MOSFET transistor and the collector of the bipolar transistor being connected to the source of the MOSFET transistor via the second resistor, the second terminal of the third resistor being connected to the interconnection point; a voltage shifting subcircuit including a first diode mounted in parallel with a first capacitor, a first terminal of the first diode and a first terminal of the first capacitor being connected to a first interconnection node, and a second terminal of the first diode and a second terminal of the first capacitor being connected to a second interconnection node; The present invention is characterized by further comprising:

[0044] In particular, the subcircuit for assisting charging allows the MOSFET transistor to charge faster. Indeed, it first of all includes a first resistor, which preferably has a high value resistance (i.e. approximately 15 kΩ) so as not to exchange too much energy with the amplifier output and generate more distortion. This first resistor allows only a low current to flow to charge or discharge the gate of the MOSFET transistor. The gate behaves like a capacitor, but the combination of the MOSFET transistor and the first resistor increases the duration of the charging and discharging times.

[0045] The subcircuit for assisting discharging allows the MOSFET transistor to discharge faster. The bipolar transistor allows the gate of the MOSFET transistor to discharge, especially when the sinusoidal input signal is in its decay phase.

[0046] The voltage shift subcircuit ensures that the gate potential of the MOSFET transistor is always higher than the amplifier output. Typically, the gate potential of the MOSFET transistor can be 15V higher than that of the amplifier output. The voltage shift subcircuit also compensates for the voltage drop across the MOSFET transistor.

[0047] According to a second embodiment, the voltage shift subcircuit further includes at least a fourth resistor and a second diode mounted in parallel, a first terminal of the second diode and a terminal of the fourth resistor being connected to the first interconnection node, and a second terminal of the fourth resistor and a second terminal of the second diode being connected to a third interconnection node.

[0048] The addition of these components makes it possible to reduce the distortion observed on the amplifier output signal. This improvement in distortion is effective for sinusoidal input signals, which are of relatively low frequency (i.e., around 1 kHz).

[0049] Advantageously, according to the third embodiment, the sub-circuit for assisting charging further comprises a fifth resistor, the fifth resistor being mounted in series with the third diode, the fifth resistor and the third diode being mounted in parallel with the branch of the sub-circuit for assisting charging comprising the first resistor.

[0050] The third diode, which is mounted in parallel with the first resistor, allows the current intended to charge the gate of the MOSFET transistor to flow and blocks the current intended to discharge the gate of the MOSFET transistor. The fifth resistor is preferably of low value (i.e., approximately 300 Ω). This fifth resistor allows the gate of the MOSFET transistor to be charged faster, since its charging time constant is equal to the product of the resistance and the capacitance.

[0051] The addition of these components here again makes it possible to improve the distortion for sinusoidal input signals up to frequencies of 20 kHz. The distortion is therefore improved across the entire frequency spectrum. The sound reproduction of the loudspeakers connected to the amplifier of the invention is therefore improved. The listener perceives less distortion compared to the amplifiers of the prior art.

[0052] According to a fourth embodiment, the voltage shift subcircuit further comprises a second capacitor and a third capacitor, the second capacitor being mounted in parallel with the first capacitor and the first diode, and the third capacitor being mounted in parallel with the third diode and the fifth resistor. These additional components make it possible to limit disturbances (i.e. interference signals superimposed on the expected output signal).

[0053] In practice, each power supply circuit includes a first protection diode, a first terminal of which is connected to the source of the MOSFET transistor, and a second terminal of which is connected to the gate of the MOSFET transistor, and similarly, each power supply circuit further includes a second protection diode connected between the source and drain of the MOSFET transistor.

[0054] The first protection diode is added to protect the MOSFET transistor from overvoltage on its gate (which could damage it or even render it unusable) by breaking down the insulation between the gate and channel, which can only withstand + / -20V continuously and + / -30V transiently.

[0055] The role of the second protection diode is to protect the MOSFET transistor from reverse drain-source voltages that can occur if the voltage on the first power bus appears only after the voltage on the second power bus. The different power buses each have their own transformer windings and smoothing capacitors, and therefore different time constants.

[0056] According to a fifth embodiment, each power supply circuit further comprises a capacitor mounted in parallel with the fourth diode. This capacitor makes it possible to eliminate interference peaks generated by the diode when the MOSFET transistor switches, the first terminal of the diode being connected to the source of the MOSFET transistor. The total harmonic distortion (THD) is also improved. This total harmonic distortion is a measure of the linearity of the processing carried out. It is calculated by comparing the output signal of the device with a perfectly sinusoidal input signal.

[0057] In practice, the preamplification stages are connected to the first power bus of the respective power supply circuit via a circuit for damping power fluctuations of said first power bus, said power fluctuation damping circuit comprising at least one capacitor and at least one resistor mounted as a low-pass filter, in other words a resistor connected in series with a capacitor, the capacitor being connected to ground.

[0058] This assembly makes it possible to isolate noise and voltage dips, which occur especially when high-voltage amplifiers deliver high currents. The capacitor then acts as an energy store.

[0059] Advantageously, the power fluctuation damping circuit further comprises an additional capacitor mounted in parallel with the at least one capacitor. The parallel mounted capacitor is of a more modest value (typically 10 3 It has a bandwidth of 100 MHz (3x lower), which makes it possible to suppress high-frequency interference.

[0060] According to a particular embodiment of the invention, the feedback applied to the preamplification stage provides a signal proportional to the current passing through the loudspeaker. This embodiment makes it possible to obtain a high-power current amplifier. As explained with reference to FIG. 2 of the prior art, this category of high-power current amplifiers has the same topology as for the high-output voltage amplifiers (i.e. a preamplification stage coupled to an amplification stage). However, the feedback applied to the preamplification stage is different.

[0061] By using the power supply circuit of the present invention for a high output current amplifier, the high output current amplifier has a very limited consumption.

[0062] In fact, when the amplifier delivers a low voltage, the power supply circuit of the present invention will not be active. Thus, the power delivered by the power supply will be equal to the output current times the voltage delivered by the lower power power bus, instead of the maximum voltage delivered by a single power bus for a standard class AB amplifier. At equal power, and assuming for example that the voltage delivered by the lower power power bus is equal to half that of the higher power power bus, half the power will be delivered by the power supply. The transistors, which dissipate the difference between the power delivered by the power supply and the power delivered to the loudspeaker, will heat up significantly less.

[0063] The manner in which the invention is embodied and the advantages resulting therefrom will become clearly apparent from the following description of embodiments, supported by the accompanying drawings. [Brief description of the drawings]

[0064] [Figure 1] 1 is an electrical diagram of a prior art high output voltage amplifier. [Diagram 2] 1 is an electrical diagram of a prior art high power current amplifier. [Diagram 3] 1 is an electrical diagram of a prior art high output voltage amplifier including a power supply stage. [Figure 4] 4 is a graph showing the evolution of the gate voltage of a MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 3; [Figure 5a] 1 is an electrical diagram of a high output voltage amplifier according to one embodiment of the present invention. [Figure 5b] 1 is an electrical diagram of a high output voltage amplifier according to one embodiment of the present invention. [Figure 6] 4 is an electrical diagram of a power supply circuit of a high-power amplifier according to a second embodiment; [Figure 7] 7 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 6 with a sine curve at the input with a frequency of 20 kHz; [Figure 8] 7 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 6 with a sine curve of frequency 1 kHz at the input. [Figure 9] 11 is an electrical diagram of a power supply circuit of a high-power amplifier according to a third embodiment; [Figure 10] 10 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 9 with a sine curve at the input with a frequency of 20 kHz; [Figure 11] 10 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 9 with a sine curve of frequency 1 kHz at the input. [Figure 12] 11 is an electrical diagram of a power supply circuit of a high-power amplifier according to a fourth embodiment. [Figure 13]13 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 12 with a sine curve at the input with a frequency of 20 kHz; [Figure 14] 10 is an electrical diagram of a power supply circuit of a high-power amplifier according to a fifth embodiment. [Figure 15] 15 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 14 with a sine curve at the input with a frequency of 20 kHz; [Figure 16] 6 is an electrical diagram of the power supply circuit of the high-power amplifier according to the first embodiment of FIG. 5; [Figure 17] 17 is a graph showing the evolution of the gate voltage of the MOSFET transistor, the output voltage of the amplifier and the output signal of the power supply circuit for the circuit of FIG. 16 with a sine curve at the input with a frequency of 20 kHz; [Figure 18a] 1 is an electrical diagram of a high power current amplifier according to an embodiment of the present invention. [Figure 18b] 1 is an electrical diagram of a high power current amplifier according to an embodiment of the present invention. [Figure 19] 1 is an electrical diagram of a protection structure for a high power current amplifier according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] As shown in Figures 5a-5b, the high-power amplifier 102 of the present invention is symmetrical, which includes an upper part and a lower part, where the upper part amplifies the positive half-wave of the input signal S1 and the lower part amplifies the negative half-wave of the input signal S1.

[0066] The high-power amplifier 102 includes a preamplification stage which receives the input signal S1 and also supplies, via a network consisting of resistors R23, R57 (mounted in parallel with capacitors C7, C8), signals coming from the collectors of transistors Q5, Q6. These signals are supplied to a power amplification stage 302 based on transistors Q8, Q9. The latter supplies an output signal 3 intended to power the loudspeaker R44. A feedback supplies an image of the output signal 3 to the preamplification stage 201.

[0067] The high power amplifier 102 also includes an upper power supply circuit 155a and a lower power supply circuit 155b, where the upper power supply circuit 155a is connected to the upper part of the power amplification stage 302 and the lower power supply circuit 155b is connected to the lower part of the power amplification stage 302.

[0068] The preamplification stage 301 includes two differential pairs 110a, 110b, each including two transistors Q1, Q2 and Q3, Q4 mounted in mirror of each other, such that the emitters of the transistors Q1, Q2 are connected to the -65V power bus via resistors R2, R3 and a first constant current source I1, while the emitters of the transistors Q3, Q4 are connected to the +65V power bus via resistors R4, R5 and a second current source I2 of the same value.

[0069] The current sources I1 and I2 include transistors Q23 and Q24, the collectors of which are connected to resistors R2, R3 and R4, R5, respectively. The emitters of the transistors Q23 and Q24 are connected to resistors R6 and R10. The second terminal of the resistor R6 is connected to the -65V power bus on the one hand and to ground on the other hand through a capacitor C11 mounted in series with a resistor R46. The second terminal of the resistor R10 is connected to the +65V power bus on the one hand and to ground on the other hand through a capacitor C12 mounted in series with a resistor R48.

[0070] Diodes D1, D2 are mounted between the bases of transistors Q23, Q24 and the second terminals of resistors R6, R10, while resistors R45, R47 are mounted between the bases of transistors Q23, Q24 and the interconnection points between capacitors C11, C12 and resistors R46, R48.

[0071] The collectors of transistors Q2, Q4 may be directly connected to the +65V and -65V power buses, respectively. Alternatively, the collectors of transistors Q2, Q4 may be connected to the +65V and -65V power buses, respectively, through power fluctuation damping circuits 304, 305.

[0072] The power fluctuation damping circuits 304, 305 include resistors R52, R55 mounted in series with capacitors C15, C19 connected to ground. The second terminals of the resistors R52, R55 are connected to the + / -65V power bus. Advantageously, further capacitors C16, C20 can be mounted in parallel with the capacitors C15, C19. In practice, the capacitors C15, C19 have a value between 150 μF and 300 μF, while the capacitors C16, C20 have a value between 150 nF and 300 nF.

[0073] The collectors of transistors Q1, Q3 are connected to the +65V and -65V power buses, respectively, via resistors R1, R11 and, advantageously, via power fluctuation damping circuits 304, 305. In the absence of feedback, the gain of the first preamplification stage 102 depends on the resistor ratios R1 / R2 and R11 / R4.

[0074] The bases of the transistors Q1 and Q3 are connected to each other and to ground via a resistor R7. The bases of the transistors Q2 and Q4 are also connected to each other. The bases of the transistors Q1 and Q3 are supplied with an input signal S1. A voltage source V1 (connected between the point S1 and ground) represents the generator of the input signal S1. An intermediate filter circuit can be inserted between the input signal S1 and the bases of the transistors Q1 and Q3. This circuit includes, for example, a band-pass filter, which includes a resistor R9 and a capacitor C10 (which is connected to ground), as well as two capacitors C1, C6 mounted in parallel.

[0075] The bases of transistors Q2 and Q4 are connected via resistor R18 to loudspeaker R44, so as to form a feedback applied to the preamplification stage 301. The collectors of transistors Q1 and Q3 ensure the coupling of the preamplification stage 301 to the circuits 306, 303, 307 and resistors R12, R13.

[0076] The power amplifier stage 302 includes two transistors Q8, Q9 which are connected by their respective bases to the preamplifier stage 301 via circuits 306, 307.

[0077] The circuits 306, 307 include transistors Q5, Q6, whose emitters are connected to the + / -65V voltage bus via resistors R12, R13, and whose bases are connected to the collectors of transistors Q1, Q3. Capacitors C2, C3 are connected between the base and collectors of transistors Q5, Q6 to improve the stability of the amplifier. The collectors of transistors Q5, Q6 are connected on the one hand to resistors R57, R23, which are mounted in parallel with capacitors C8, C7, and on the other hand to a bias circuit 303. The bias circuit 303 includes a transistor Q7, whose emitter is connected to the collector of transistor Q5, and whose collector is connected to the collector of transistor Q6. A resistor R14 is mounted between the collector and base of transistor Q7, and another resistor R15 is mounted between the emitter and base of transistor Q7. Finally, a capacitor C5 (e.g., having a value of 1 μF) is connected between the emitter and collector of transistor Q7. This capacitor C5 improves the stability of the amplifier. Alternatively, resistors R13, R12 can be connected to the +65V and −65V power buses via power fluctuation damping circuits 304, 305, respectively.

[0078] The circuits 306, 307 perform a second voltage amplification. The gain of this amplification is proportional to the ratio of the resistance "seen by the collector" to the resistance present above the emitters of Q5, Q6. When one of the transistors Q5, Q6 conducts, its dual is cut off. The conducting transistor therefore sees a very high resistance and therefore a very large voltage gain.

[0079] The power amplification stage 302 further comprises two transistors Q10, Q11, whose bases are connected to the emitters of the transistors Q8 and Q9, respectively. This so-called "Darlington" configuration allows to increase the current gain. The emitters of the transistors Q8 and Q10 are coupled to the loudspeaker R44 by their respective resistors R16 and R19, while the emitters of the transistors Q9 and Q11 are coupled to the loudspeaker R44 by their respective resistors R17 and R20. They have respective quiescent currents, for example, equal to 6 mA for the transistors Q8, Q9 and equal to 75 mA for the transistors Q10, Q11.

[0080] The power amplifier stage 302 is connected to two power supply circuits 155a, 155b at the site of the collectors of the transistors Q8 to Q11. These power supply circuits 155a, 155b are connected to two voltage buses with respective levels V+, V++. The power supply circuits 155a, 155b therefore make it possible to select one or the other of these voltage levels depending on the amplification requirements. Typically, the first power bus delivers + / - 65V and the second power bus delivers + / - 35V. The second power bus is intended to be used to power the power amplifier stage 302 when the output signal to be generated does not have a very high voltage (typically less than 27V).

[0081] Due to the relatively low current passing through the transistors Q8 and Q9 (typically less than 10% of the current passing through the transistors Q10 and Q11), the collectors of Q8 and Q9 can be directly connected to the first power bus V++, which does not cause significant additional power dissipation. This embodiment improves the stability of the amplifier in terms of its phase margin and its gain margin.

[0082] In addition, the bases of the transistors Q2 and Q4 are connected to a protection line, which includes a resistor R28 mounted in series with a capacitor C4 connected to ground. This assembly is a voltage divider. In fact, the capacitor C4 behaves like a short circuit when the voltage through the circuit is AC. On the other hand, when the voltage through the circuit is DC, the capacitor C4 behaves like an open circuit. In this case, the output of the high-power amplifier 100 is directly connected to the point S2. The voltage gain of the high-power amplifier 100 is then equal to 1, which makes it possible to limit possible undesirable DC components on the voltage applied to the terminals of the loudspeaker R44.

[0083] Several embodiments are possible for the power supply circuits 151 to 155, 155a, 155b.

[0084] For all the following embodiments, the signals numbered 1 represent the gate signals of the MOSFET transistors M1, M2. The output signals numbered 3 represent the output signals of the amplifier, i.e. the signals at the terminals of the loudspeaker R44. The output signals numbered 2 represent the output signals of the power supply circuits 151-155, 155a, 155b, i.e. the signals present on the collectors of the transistors Q8 and Q10.

[0085] In the remainder of the description, only the upper power supply circuit is illustrated, but FIGS. 5a-b make it possible to understand the positioning of the corresponding components for the lower power supply circuit.

[0086] As illustrated in Fig. 6, in the first embodiment, the power supply circuit 151 includes MOSFET transistors M1, M2, which are connected by their drains directly to the first power bus V++ and by their sources to the second power bus V+ through fourth diodes D3, D11, which can be conventional or Schottky diodes. In practice, the anode of the fourth diode D3 is connected to the second power bus V+ and its cathode is connected to the output signal numbered 2, which represents the output signal of the power supply circuit 151-155, 155a, 155b. The cathode of the fourth diode D11 is connected to the second power bus V+. The MOSFET transistors M1, M2 operate linearly, blocking for voltages below a threshold (typically 35V) and then switching above this threshold. The MOSFET transistors M1, M2 allow the first power bus V++ to pass when a control voltage greater than a threshold is applied to it, which voltage is controlled by the association of a sub-circuit for assisting charging 131, a sub-circuit for assisting discharging 141, and a voltage shifting sub-circuit 161.

[0087] The sub-circuit 131 for assisting charging includes first resistors R24, R31 connected between the gates of the MOSFET transistors M1, M2 and the interconnection points A1, A2.

[0088] The subcircuit 141 for supporting discharging includes transistors Q12, Q13, the emitters of which are connected on the one hand to the gates of the MOSFET transistors M1, M2 and on the other hand to the subcircuit 131 for supporting charging. The collectors of the transistors Q12, Q13 are connected to the output signal 2 of the power supply circuit 151 via second resistors R8, R27. The bases of the transistors Q12, Q13 are connected to the interconnection points A1, A2 via third resistors R21, R39.

[0089] The voltage shift subcircuit 161 includes a first capacitor C18, C23 mounted in parallel with a first diode D8, D10. The cathode of the first diode D8 is connected to a first interconnection node N1 and the anode of the first diode D8 is connected to a second interconnection node N2. The diode D10 is connected in reverse as shown in Figures 5a-5b, i.e., its cathode is connected to the interconnection node N3 and its anode is connected to the interconnection node N4. The first interconnection node is connected to the interconnection point A1 and the second interconnection node is connected to the loudspeaker R44.

[0090] The voltage shift subcircuit ensures that the gate potential of MOSFET transistor M1 is always 15V higher than that of the amplifier output.

[0091] In addition, the Darlington circuit consisting of transistors Q8 and Q10 requires a dropout voltage of 5V (i.e., a voltage equal to the difference between the input voltage on the collector of transistor Q8 and the output voltage on the emitter of transistor Q10). On the other hand, MOSFET M1 requires a dropout voltage of 10V (i.e., a voltage equal to the difference between the input voltage on its gate and the output voltage on its source in the case where the current is maximum and it is saturated). Therefore, the voltage shift subcircuit must compensate for the voltage drops of the two bipolar transistors Q8 and Q10 as well as the voltage drop of MOSFET M1 (i.e., 5+10=15V).

[0092] The power supply circuit 151 advantageously includes a first protection diode D5, D13. The anode of the diode D5 is connected to the output signal 2 of the power supply circuit 151 and its cathode is connected to the gate of the MOSFET transistor M1. The cathode of the diode D13 is connected to the output of the power supply circuit 155b and its anode is connected to the gate of the MOSFET transistor M2. Similarly, the power supply circuit 151 includes a second protection diode D4, D12. The cathode of the diode D4 is connected to the source of the MOSFET transistor M1 and its anode is connected to the source of the MOSFET transistor M1. The cathode of the diode D12 is connected to the source of the MOSFET transistor M2 and its anode is connected to the drain of the MOSFET transistor M2.

[0093] The different signals obtained with such an assembly are illustrated in FIGS.

[0094] The signal shown in FIG. 7 corresponds to the signal obtained by a sinusoid of frequency 20 kHz fed at the input of the high-power amplifier 102 .

[0095] We therefore notice that the output signal 3 is distorted at the apexes of the sine curve, which have a triangular appearance. It is therefore not possible to correctly reproduce the 20 kHz sine curve. On the other hand, we do not observe any abnormal voltage peaks. The power losses are therefore limited.

[0096] The signal shown in FIG. 8 corresponds to the signal obtained by a sinusoid of frequency 1 kHz fed at the input of the high-power amplifier 102 .

[0097] We therefore notice that the output signal 3 is less distorted than at 20 kHz. To the naked eye, the sinusoid of the output signal 3 even appears to be perfectly reproduced. However, it turns out that the total harmonic distortion (THD) is greater than 0.1%.

[0098] As shown in Fig. 9, in the second embodiment, the voltage shift subcircuit 162 of the power supply stage 152 further includes a second diode D6, D29 mounted in parallel with the fourth resistor R22, R26. The cathode of the second diode D6 is connected to the interconnection point N1 and the anode of the second diode D6 is connected to the third interconnection node N10. The diode D29 is connected in reverse, as shown in Figs. 5a-5b, i.e. its cathode is connected to the interconnection node N20 and its anode is connected to the interconnection node N4.

[0099] The different signals obtained by such an assembly are illustrated in Figures 10 and 11. The signal illustrated in Figure 10 corresponds to the signal obtained by a sinusoid of frequency 20 kHz fed at the input of the high power amplifier 102.

[0100] We therefore notice that the output signal 3 is distorted at the apexes of the sine curve which have a triangular appearance. It is therefore not possible to reproduce the 20 kHz sine curve correctly.

[0101] The signal illustrated in FIG. 11 corresponds to the signal obtained by a sinusoid of frequency 1 kHz fed at the input of the high-power amplifier 102 .

[0102] To the naked eye, the sinusoid of the output signal 3 appears perfectly reproduced on the positive half-wave and slightly distorted on the negative half-wave. The harmonic distortion THD is equal to 0.45%, since the observed distortion corresponds to the occurrence of harmonics.

[0103] Therefore, the addition of these components does not help to reduce the distortion observed on the amplifier output signal. The addition of the second diode D6, D29 and the fourth resistor R22, R26 degrades the dynamic performance of the circuit. For these components to be beneficial, i.e., for them to improve the low and high frequency degradation, a more complex circuit is required. It is possible to add other elements around the transistors Q12, Q13 to obtain performance gains.

[0104] As shown in Fig. 12, in the third embodiment, the subcircuit 132 for supporting charging of the power supply stage 153 further includes a circuit branch, which includes a third diode D9, D14 in series with a fifth resistor R29, R30, which is mounted in parallel with the first resistor R24, R31. The cathode of the third diode D9 is connected, for example, to the gate of the MOSFET transistor M1. The anode of the third diode D14 is connected to the gate of the MOSFET transistor M2. Alternatively, the components D9, R29 and D14, R30 can be reversed, such that the third diode D9, D14 is connected to the gate of the MOSFET transistor M1, M2 via the resistor R29, R30.

[0105] The different signals obtained by such an assembly are illustrated in Figure 13. The latter corresponds to the signal obtained by a sinusoid of frequency 20 kHz provided at the input of the high-power amplifier 102.

[0106] We observe that the output sinusoid corresponding to the output signal numbered 3 is well restored. On the other hand, output signal 2 (representing the output voltage of the power supply circuit 153) has distortions between 0 μs and 5 μs and between 18 μs and 20 μs. The THD is equal to 0.26%. The addition of these components now makes it possible to improve the distortion for sinusoidal input signals up to a frequency of 20 kHz.

[0107] As shown in FIG. 14, in the fourth embodiment, the voltage shift sub-circuit of the power supply stage 154 further includes a third capacitor C21, C24 and a second capacitor C17, C22, the third capacitor C21, C24 being mounted in parallel with a fourth resistor R22, R26 and a second diode D6, D29, and the second capacitor C17, C22 being mounted in parallel with a first diode D8, D10 and a first capacitor C18, C23.

[0108] The different signals obtained by such an assembly are illustrated in Figure 15. The latter corresponds to the signal obtained by a sinusoid of frequency 20 kHz fed at the input of the high-power amplifier 102.

[0109] Thus, we observe that although signal 2 is less disturbed, the switching of the fourth diode D3 still generates interference, especially between 45 μs and 50 μs.

[0110] Indeed, the second capacitors C17, C22 (using for example electrochemical technology) have a significant value (typically between 5 μF and 15 μF) and constitute the energy storage, while the first capacitors C18, C23 (using for example electrochemical plastic film technology) have a lower value (typically between 50 nF and 150 nF) and make it possible to smooth out high frequency interferences. The THD is reduced to 0.21%.

[0111] This association allows the circuit to be more efficient during the transient phases of signal growth and decay.

[0112] As shown in Figures 5a-5b and 16, in the fifth embodiment, the power supply stage 155, 155a, 155b further includes a fourth capacitor C14, C25 mounted in parallel with the fourth diode D3, D11.

[0113] The different signals obtained by such an assembly are illustrated in Figure 17. The latter corresponds to the signal obtained by a sinusoid of frequency 20 kHz fed at the input of the high-power amplifier 102.

[0114] We observe that the interference generated by the fourth diode D3, D11 disappears between 45 μs and 50 μs, which results in a slight drop in THD from 0.21% to 0.2%.

[0115] Although the invention has been described above with reference to Figures 5a-b to 17 in relation to a high-power audio amplifier 102 making it possible to supply a voltage to a loudspeaker R44, it is also possible to use the power supply circuit of the invention for a high-output current audio amplifier, i.e. for supplying a current to a loudspeaker.

[0116] To do this, as illustrated in Figures 18a-b, a current measuring resistor R61 is inserted between the loudspeaker R44 and ground. Furthermore, the current amplifier 103 does not have a protection line 403. The bases of the transistors Q2 and Q4 are connected via a capacitor C40 to an interconnection point located between the resistor R61 and the loudspeaker R44. This capacitor C40 therefore allows only the AC component of the signal to pass.

[0117] Thus, in this configuration, loudspeaker R44 is traversed by an AC current, whose image is applied to point S2. It follows that the transconductance of the amplifier is equal to 1 / R61 for AC signals.

[0118] Alternatively, a resistor can be added in the feedback between point S2 and the output of amplifier 3 to protect the loudspeaker R44 and the amplifier itself. In case there is a DC component at the terminals of the loudspeaker R44, it is applied at the bases of the transistors Q2 and Q4 via resistor R18. The feedback will tend to cancel this DC component. In addition, resistor R18 helps to limit the gain of the amplifier in the absence of the loudspeaker R44 and prevents it from oscillating.

[0119] When the current is alternating, the capacitor C40 has a negligible impedance compared to the value of the resistor R18. During normal operation, i.e. when there is no DC component and when the loudspeaker R44 is actually present at the amplifier output, the resistor R18 has almost no effect. On the other hand, in the absence of the loudspeaker R44 at the amplifier output, we can consider that the point S2 is connected on the one hand to the amplifier output via the resistor R18 and on the other hand to ground via the resistor R61. This is because the capacitor C40 behaves like an alternating current short circuit. The voltage amplification will therefore be limited to (R18+R61) / R61. This is because the amplifier output voltage multiplied by R61 / (R18+R61) is compared with the input voltage applied at point S1 by the differential pair formed by the transistors Q1 / Q2 and Q3 / Q4. The amplifier will then not deliver its maximum output voltage, which could be dangerous. Similarly, when a DC component is present and when loudspeaker R44 is present or absent at the output of the amplifier, the capacitor behaves like an open circuit and therefore the DC component is reinjected at point S2 via resistor R18. The voltage gain is therefore limited to 1 for DC voltages, which does not risk damaging loudspeaker R44.

[0120] In another variant, a current amplifier protection circuit can be added. To do this, as shown in FIG. 19, the interconnection point P1, located between the resistor R61 and the loudspeaker R44, is connected to a first terminal of a resistor R70. In this embodiment, the second terminal of the resistor R70 is connected to the collector of the transistor Q16, which is also connected to the base of the second transistor Q15. A voltage divider is made up of resistors R71 and R72, making it possible to adapt the current threshold, from which the protection circuit starts to act. A first terminal of the resistor R71 is connected to a second power bus V+, which has a value of 32V. A second terminal of the resistor R71 is connected to the base of the transistor Q15 and to the collector of the transistor Q16. A first terminal of the resistor R72 is connected to the second terminal of the resistor R70, and a second terminal of the resistor R72 is connected to ground. The conduction threshold voltage of transistor Q15 is therefore shifted by V+*R72 / (R71+R72), which makes it possible to increase the sensitivity, i.e. the current threshold at which the protection operates is lowered.

[0121] Preferably, the transistor Q15 is a Darlington transistor. This makes it possible to limit the distortion caused by the circuit by drawing a lower current at the terminals of the measuring resistor R61 while maintaining a sufficient sensitivity due to the divider network R71 / R72. Another divider bridge, consisting of resistors R73 and R74, is inserted between point 3 and ground. A first terminal of the resistor R73 is connected to point 3. A second terminal of the resistor R73 is connected to the base of the transistor Q16 and to a first terminal of the resistor R74, the second terminal of which is connected to ground. Thus, a voltage threshold is adapted, from which the current protection is initiated and neutralized. The emitters of the transistors Q16 and Q15 are connected together and to ground, and the collector of the transistor Q15 is connected to the base of the transistor Q8 through a diode D21, the cathode of which is connected to the collector of the transistor Q15.

[0122] This circuit must be mirrored to manage current protection during the negative half-wave, then the NPN transistor is replaced by a PNP transistor.

[0123] This circuit makes it possible to limit the risk of power failure of the current amplifier, in particular when it is overloaded or when its output is short-circuited: in fact, in these cases, the product of the output current and the voltage of the power bus will be completely dissipated by the transistors, which may be damaged.

[0124] 19, if the current in the current measuring resistor R61 is sufficient to turn on the transistor Q15, the latter is able to shunt the signal coming from the base of the transistor Q8 towards ground, via the diode D21, blocking it. On the other hand, if the voltage at the terminals of the loudspeaker R44 is sufficient to turn on the transistor Q16, the signal coming from the base of the transistor Q15 will be diverted to ground, and it is the latter transistor that will be blocked. Thus, the protection circuit is neutralized when there is a sufficient voltage at the amplifier output.

[0125] In conclusion, the invention makes it possible to obtain a high-power audio amplifier that makes it possible to limit the distortions identified on the signal, thus improving the efficiency of the amplifier and reducing saturation. [Explanation of symbols]

[0126] 1 Gate signal of MOSFET transistor M1 2. Output signal of power supply circuit 150 3 Amplifier output signal, signal at the terminals of loudspeaker R44 100 High Power Amplifier 101 Current Amplifier 102 High-power amplifier 103 Current Amplifier 110a, 110b differential pair 131 Subcircuit for assisting in charging 132 Subcircuit for assisting in charging 140a Upper part 140b Lower part 141 Subcircuit for assisting in discharging 150 Power supply circuit 151 Power supply circuit 152 Power Supply Stage 153 Power Supply Stage 154 Power Supply Stage 155 Power Supply Stage 155a Power supply circuit 155b Power supply circuit 161 Voltage Shift Subcircuit 162 Voltage Shift Subcircuit 163 Voltage Shift Subcircuit 201 Preamplification Stage 202 Power Amplification Stage 203 Amplification Stage 204 Power Amplification Stage 301 Preamplification Stage 302 Power Amplification Stage 303 Bias Circuit 304 Power Fluctuation Damping Circuit 305 Power Fluctuation Damping Circuit 306 Circuit 307 Circuit 403 Protection Line A1 Interconnection Point A2 Interconnection Point C1 Capacitor C2 Capacitor C3 Capacitor C4 Capacitor C6 Capacitor C7 Capacitor C8 Capacitor C10 Capacitor C11 Capacitor C12 Capacitor C14 4th capacitor C15 Capacitor C16 Capacitor C17 Second Capacitor C18 First Capacitor C19 Capacitor C20 Capacitor C21 Third Capacitor C22 Second Capacitor C23 First Capacitor C24 3rd Capacitor C25 4th Capacitor D1 Diode D2 Diode D3 Fourth diode D4 Second protection diode D5 First protection diode D6 Second Diode D8 First Diode D9 Third Diode D10 First Diode D11 4th diode D12 Second protection diode D13 First protection diode D14 Third Diode D15 Diode D29 Second Diode I First constant current source, second current source I1 First constant current source I2 Second current source M1 MOSFET transistor M2 MOSFET transistor N1 First interconnection node N2 Second interconnection node N3 Interconnection Node N4 Interconnection Node N10 3rd Interconnection Node N20 Interconnection Node P1 Interconnect Point Q1 Transistor Q2 Transistor Q3 Transistor Q4 Transistor Q5 Transistor Q6 Transistor Q7 Transistor Q8 Transistor Q9 Transistor Q10 Transistor Q11 Transistor Q12 Transistor Q13 Transistor Q15 Transistor Q16 Transistor Q23 Transistor Q24 Transistor R1 resistor R2 resistor R3 resistor R4 resistor R5 resistor R6 resistor R7 resistor R8 Second resistor R9 resistor R10 resistor R11 resistor R12 resistor R13 Resistor R14 resistor R15 resistor R16 resistor R17 resistor R18 resistor R19 resistor R20 resistor R21 resistor R22 4th resistor R23 resistor R24 First Resistor R26 4th resistor R27 Second resistor R28 resistor R29 5th resistor R30 5th resistor R31 First resistor R39 resistor R44 Loudspeaker R45 resistor R46 resistor R47 resistor R48 resistor R52 resistor R55 resistor R57 resistor R61 resistor S1 point, input signal S2 Points T1 Voltage source V1 voltage source

Claims

1. A high-power audio amplifier (102) intended to control at least one loudspeaker (R44), said amplifier comprising: a preamplification stage (201, 301) receiving an input signal (S1); - a power amplification stage (202-203, 302) connected to said preamplification stage (201, 301) and supplying an output signal (3) intended to power said at least one loudspeaker (R44), said preamplification stage (201, 301) and said power amplification stage (202-203, 302) comprising an upper part and a lower part mounted mirroring each other; - a feedback providing an image of said output signal (3) to said preamplification stage (201, 301); an upper power supply circuit (151-155, 155a) connected to the upper part of the power amplification stage (202-203, 302) and enabling it to be powered by a first or a second power bus (V++, V+); a lower power supply circuit (155b) connected to the lower part of the power amplification stage (202-203, 302) and enabling it to be powered by a first or a second power bus; Including, a high power audio amplifier (102), each power supply circuit (151-155, 155a, 155b) comprising a MOSFET transistor (M1, M2) and a monitoring means, the MOSFET transistor (M1, M2) being controlled by the monitoring means to perform switching between one or the other of the two power buses (V++, V+), the MOSFET transistor (M1, M2) being connected to the second power bus (V+) via a fourth diode (D3, D11), a first terminal of which is connected to the source of the MOSFET transistor (M1, M2), the drain of which is connected to the first power bus (V++); Each of the power supply circuits (151 to 155, 155a, 155b) a sub-circuit (131-133) for supporting charging said MOSFET transistors (M1, M2), said sub-circuit (131-133) for supporting charging comprising at least a first resistor (R24, R31), a first terminal of said first resistor (R24, R31) being connected to the gates of said MOSFET transistors (M1, M2) and a second terminal of said first resistor (R24, R31) being connected to an interconnection point (A1); a subcircuit (141) for assisting in discharging the MOSFET transistors (M1, M2), the subcircuit (141) for assisting in discharging comprising at least second and third resistors (R8, R27, R21, R39) and a bipolar transistor (Q12, Q13), the base of which is connected to a first terminal of the third resistor (R21, R39), the emitter of which is connected to the gate of the MOSFET transistor (M1, M2) and the collector of which is connected to the source of the MOSFET transistor (M1, M2) via the second resistor (R8), the second terminal of which is connected to the interconnection point (A1, A2); a voltage shift subcircuit (161-163) comprising a first diode (D8, D10) mounted in parallel with a first capacitor (C18, C23), a first terminal of the first diode (D8, D10) and a first terminal of the first capacitor (C18, C23) being connected to a first interconnection node (N1, N4), the first interconnection node (N1, N4) itself being a voltage shift subcircuit (161-163) connected to the interconnection point (A1, A2) of the subcircuit (141) for assisting the discharging, a second terminal of the first diode (D8, D10) and a second terminal of the first capacitor (C18, C23) are connected to a second interconnection node (N2, N3), the second interconnection node (N2, N3) itself being connected to the output signal (3); A high power audio amplifier (102), further comprising:

2. 2. The amplifier of claim 1, wherein the voltage shift subcircuit (161-163) further comprises at least a fourth resistor (R22, R26) and a second diode (D6, D29), the fourth resistor (R22, R26) and the second diode (D6, D29) being mounted in parallel, a first terminal of the second diode (D6, D29) and a terminal of the fourth resistor (R22, R26) being connected to the interconnection point (A1, A2), and a second terminal of the fourth resistor (R22, R26) and a second terminal of the second diode (D6, D29) being connected to a third interconnection node (N10).

3. 3. The amplifier according to claim 1 or 2, characterized in that the sub-circuit (131-133) for assisting charging further comprises a fifth resistor (R29, R30), the fifth resistor (R29, R30) being mounted in series with a third diode (D9, D14), the fifth resistor (R29, R30) and the third diode (D9, D14) being mounted in parallel with the branch of the sub-circuit (131-133) for assisting charging that comprises the first resistor (R24, R31).

4. 4. The amplifier according to claim 1, wherein the voltage shift subcircuit (161-163) further comprises a second capacitor (C17, C22) and a third capacitor (C21, C24), the second capacitor (C17, C22) being mounted in parallel with the first capacitor (C18, C23) and the first diode (D8, D10), and the third capacitor (C21, C24) being mounted in parallel with the second diode (D6, D29) and the fifth resistor (R22, R26).

5. 5. The amplifier according to claim 1, wherein each power supply circuit (151 to 155, 155a, 155b) comprises a first protection diode (D5, D13), a first terminal of the first protection diode (D5, D13) being connected to the source of the MOSFET transistor (M1, M2) and a second terminal of the first protection diode (D5, D13) being connected to the gate of the MOSFET transistor (M1, M2).

6. 6. The amplifier according to claim 1, wherein each power supply circuit (151-155, 155a, 155b) further comprises a second protection diode (D4, D12) connected between the source and the drain of the MOSFET transistor (M1, M2).

7. 7. The amplifier according to claim 1, wherein each power supply circuit (151-155, 155a, 155b) further comprises a fourth capacitor (C14, C25) mounted in parallel with the fourth diode (D3, D11).

8. 8. The amplifier according to claim 1, wherein the preamplification stage (201, 301) is connected to the first power bus (V++) of the respective power circuit (151-155, 155a, 155b) by a power fluctuation damping circuit (304, 305) of the first power bus (V++), the power fluctuation damping circuit (304, 305) comprising at least one capacitor (C15, C19) and at least one resistor (R52, R55) mounted as a low pass filter.

9. 9. The amplifier of claim 8, wherein the power fluctuation damping circuit (304, 305) further comprises an additional capacitor mounted in parallel with the at least one capacitor (C16, C20).

10. 10. An amplifier according to any one of the preceding claims, characterized in that the feedback applied to the pre-amplification stage provides a signal proportional to the current passing through the loudspeaker.

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