Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03F—AMPLIFIERS
  • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
  • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
  • H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
  • H03F3/217—Class D power amplifiers; Switching amplifiers
  • H03F3/2173—Class D power amplifiers; Switching amplifiers of the bridge type

Definitions

• the present invention relates to a device for amplifying a voltage representative of audiophonic information from a source for the attack of an acoustic load.
• the present invention relates to such a device comprising a class D amplification chain capable of delivering at least one amplified electrical signal for driving the load as a function of the voltage representative of the audiophonic information.
• a class D amplification chain capable of delivering at least one amplified electrical signal for driving the load as a function of the voltage representative of the audiophonic information.
• Such devices are known to be used in mass-produced equipment, such as mobile phones for example.
• the sound quality is generally unsatisfactory due to the low bandwidth of these amplification devices.
• the object of the present invention is to solve the above problem.
• the subject of the invention is a device for amplifying the power of a voltage representative of an audiophonic information originating from a source for the attack of an acoustic load, the device comprising an amplification chain.
• class D capable of delivering at least one amplified electrical signal for driving the load as a function of the voltage representative of the acoustic information, characterized in that it further comprises:
• the device comprises one or more of the following features:
• the first correction loop comprises:
• the correction means comprise means for controlling the measurement voltage on the voltage delivered at the input of the amplification system;
• the amplifier chain comprises a class D power amplifier and at least one low-pass filter arranged at the output of the amplifier, and the measuring means are suitable for measuring the output current of the or each pass filter; low;
• the amplifier chain comprises a class D power amplifier and at least one low-pass filter arranged at the output of the amplifier, and the measuring means are capable of measuring the input current of the or each pass filter; low.
• the measuring means are chosen to have a frequency behavior substantially equal to that of the or each low-pass filter
• the amplification system comprises a half-bridge type amplifier
• the amplification system comprises an H-bridge type amplifier; the measuring means are suitable for measuring a single current flowing in the amplification chain;
• the measuring means are suitable for measuring two currents flowing in the amplification chain
• the conversion means comprise means for subtracting the two measured currents and means for transforming the currents subtracted into the measurement voltage;
• amplification chain means for measuring at least one voltage of the amplification chain; and a second correction loop, external to the first correction loop, adapted to correct the amplified electrical signal as a function of the or each measured voltage;
• the second correction loop comprises means for controlling the or each voltage measured on the voltage representative of the audiophonic information
• the amplification chain comprises a class D power amplifier and at least one low-pass filter arranged at the output of the amplifier, and the means for measuring the or each voltage are suitable for measuring the voltage at the output of the amplifier; or each low-pass filter;
• the amplifier chain comprises a class D power amplifier and at least one low-pass filter arranged at the output of the amplifier, and the means for measuring the or each voltage are suitable for measuring the input voltage of the amplifier; or each low-pass filter; the means for measuring the at least one voltage are suitable for measuring a single voltage of the amplification chain;
• the means for measuring the or each voltage are suitable for measuring the difference of two amplification system voltages
• the second external correction loop comprises means for correcting a voltage delivered at the input of the first loop; correction based on the difference of these two voltages.
• FIG. 1 is a schematic view of a first embodiment of the device according to the invention.
• FIG. 2 is a schematic view of a second embodiment of the device according to the invention
• FIG. 3 is a schematic view of a third embodiment of the device according to the invention.
• FIG. 4 is a schematic view of a fourth embodiment.
• FIG. 1 there is illustrated generally a first embodiment of a device for amplifying an analog voltage Ve representative of an audiophonic information item and delivered by a source 12, such as for example a reader musical CD-ROMs, a microphone, a mobile phone antenna or others.
• the device 10 drives an electromechanical-acoustic load 14, such as a loudspeaker, using the amplified voltage.
• the device 10 comprises for this purpose an amplification chain 16 comprising a class D amplifier 18 of the half bridge type in series with a low-pass filter 20.
• the amplifier 18 comprises a modulator 22 in pulse width (PWM) consisting of a comparator 24 connected to a clock 26 delivering to an inverting terminal 28 thereof a triangular voltage Vt of predetermined frequency and amplitude.
• PWM pulse width
• the modulator 22 modulates in pulse width an analog voltage Vni that receives the comparator 24 on a non-inverting terminal 30 and thus generates on an output 32 of the comparator 24 a voltage VmIi modulated in pulse width, as is known in FIG. itself.
• the amplifier 18 also comprises a logic control circuit 34 connected to the output 32 of the comparator 24 and controlling, as a function of the voltage VmI 1, a half-bridge arrangement 36 consisting of a MOSFET transistor.
• the half-bridge assembly 36 thus delivers on an output 42 an amplification of the voltage Vni in the form of an amplified voltage Va.
• the amplifier 18 is. finally connected to a power supply (not shown) switching for the supply of electrical energy of these components.
• the low-pass filter 20 for example constituted by an LC circuit, is connected to the output 42 of the half-bridge assembly 36 and outputs an average Vs of amplified voltage Va.
• the load 14 is connected on one of its terminals to the output of the low-pass filter 20 and on the other of its terminals to ground.
• the device 10 further comprises a current sensor 44 arranged at the output of the low-pass filter 20, for example a current sensor based on transistors of the MAX47ESA type from the company Maxim Integrated Products Inc.
• the current sensor 44 measures the current Is at the output of the low-pass filter and is connected to a correction loop 46 of the charge voltage Vs of the load 14.
• This loop 46 is a feedback loop comprising a current converter / voltage 48 connected to the current sensor 44 and generating a measurement voltage Vim image of the current Is measured by it.
• the converter 46 consists of a predetermined impedance resistance.
• the current sensor and the current / voltage converter consist of a predetermined impedance resistor arranged in series with the low-pass filter 20 and at the output thereof and of a voltage sensor measuring the voltage at the terminals of said resistor.
• the correction loop 46 also comprises a subtractor 50 and a corrector 52.
• the subtracter 50 is connected to the converter 48 and to the source 12, and outputs the difference ⁇ c of these two voltages, hereinafter referred to as "error of current control ".
• the corrector 52 is connected to the output of the subtractor 50 and determines, as a function of the servocontrol error ⁇ c, the analog voltage Vni.
• the corrector 52 implements a predetermined control law of the measurement voltage Vim on the voltage Ve, such as for example an integral proportional law (P1) or a derivative integral proportional law (PID), having the effect of substantially canceling the servocontrol error ⁇ c and to obtain stability and performance conditions required for the correction loop.
• a predetermined control law of the measurement voltage Vim on the voltage Ve such as for example an integral proportional law (P1) or a derivative integral proportional law (PID), having the effect of substantially canceling the servocontrol error ⁇ c and to obtain stability and performance conditions required for the correction loop.
• the corrector 52 is implemented in the form of an analog circuit, or alternatively comprises a digital signal processing unit such as a DSP for example.
• the current sensor 44 is arranged between the amplifier
• the current sensor 44 behaves substantially as a low-pass filter and the current sensor 44 is chosen so that its frequency behavior is substantially equal to that of the low-pass filter 20.
• the cut-off frequency of the sensor 44 is chosen so as not to differ from that of the filter 20 by more than 10 percent.
• the corrector 52 is arranged between the converter 48 and the subtractor 50.
• the transistors 38, 40 of the half-bridge arrangement are insulated gate bipolar transistors (IGBTs) when large signal powers are required.
• the low-pass filter 20 is omitted.
• Figure 2 there is illustrated under the general reference a second embodiment of the device according to the invention. This second embodiment differs essentially from that of FIG. 1 in that the assembly 36 of transistors of the amplifier 18 is an H-bridge or "H-bridge" assembly, which provides electrical symmetry and signals. of the entire device.
• the amplifier 36 comprises two half-bridge arrangements 36, 62 each consisting of an N-channel MOSFET 38, 64, and a common source P-channel MOSFET 40, 66. These assemblies 36, 62 are identical to that of FIG. 1. A first assembly 36 is directly connected to the output of the logic control circuit 34 and a second assembly is connected thereto through an inverter 68.
• a low-pass filter 20, 70 is connected to the output of each mounting 36, 62.
• These low-pass filters are identical to the base-pass filter of FIG. 1 and deliver averaged voltages to the load 14 which is thus attacked symmetrically.
• the device just described comprises two current sensors identical to the sensor 44 and arranged at the output of the low-pass filters 20, 70.
• the correction loop 46 then comprises, arranged between the two current sensors and the converter current / voltage 48, a circuit forming the difference between the two measured currents, dividing this difference by 2 and transforming the result of this operation into the measurement voltage.
• Such an average circuit therefore the drive current Is and filters the noise.
• the current sensor (s) are arranged at the input of the low-pass filters and each current sensor is chosen to have a frequency behavior substantially equal to that of the low-pass filters, as described previously.
• the low-pass filters 20 and 70 are omitted.
• correction loops described above are based on a measurement of one or two currents of the amplification chains, and that the correction is performed as a function of an image signal of the current or currents measured. which is not equivalent, especially in terms of impedance, to a correction loop based on a measurement of one or more amplification chain voltages. It is thus found that these correction loops have the effect of substantially increasing the bandwidth of the amplification chains and substantially improve the overall stability and accuracy of the amplification.
• FIG 3 is a schematic view of a third embodiment of the device according to the invention. Designated under the general reference 80, this device includes all the elements of that of Figure 1 and a voltage sensor 82 measuring the voltage Vs at the output of the low-pass filter 20 and an additional correction loop 84.
• the additional correction loop 84 is a feedback loop correcting the measured voltage Vs.
• the loop 84 is external to the correction loop 46 and comprises a second subtractor 86 and a second corrector 88 connected to the output of the second subtractor 86.
• the second subtracter 86 is connected to the source 12 and the voltage sensor 82 and forms the difference of the voltage Ve and the measured voltage Vs, the difference ⁇ v hereinafter referred to as "voltage control error".
• the second corrector 88 determines, as a function of the voltage control error ⁇ v, the analog input voltage of the subtractor 50 of the internal correction loop 46, as illustrated in FIG. 3.
• the second corrector 88 implement a predetermined servo law of the voltage Vs on the voltage Ve, such as an integral proportional law (P1) or a derivative integral proportional law (PID), having the effect of substantially canceling the servo error ⁇ v voltage and to obtain stability and performance conditions required for the correction loop.
• P1 integral proportional law
• PID derivative integral proportional law
• the second corrector 88 is implemented in the form of an analog circuit, or alternatively comprises a digital signal processing unit such as a DSP for example.
• the voltage sensor measures the input voltage of the low-pass filter 20 and is chosen to have a frequency behavior substantially equal to that of the low-pass filter.
• the second corrector 8B is arranged between the voltage sensor 82 and the second subtracter 86.
• FIG. 4 is a schematic view of a fourth embodiment 100 of the device according to the invention.
• This embodiment comprises all the elements of the embodiment of FIG. 2 as well as a voltage sensor 48 and a second correction loop 84 similar to the voltage sensor 48 and the second correction loop 84 of the device.
• the voltage sensor 48 of the fourth embodiment differs from that of the third embodiment in that it measures the difference of the voltages at the output of the low-pass filters 20, 70, that is to say tell the voltage across the load 14.
• the voltage sensor 48 of the fourth embodiment is identical to that of the third embodiment and measures the output voltage of the band-pass filter 20.
• the voltage sensor of the fourth embodiment measures the difference of the input voltages of the low-pass filters 20, 70 and is chosen to have a frequency behavior substantially equal to those of the low-pass filters 20, 70.
• the second corrector 88 is arranged between the voltage sensor 82 and the second subtractor 86.
• the outer loop further improves the stability and accuracy of the amplification.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Amplifiers (AREA)

Applications Claiming Priority (2)

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• 2005
  • 2005-09-07 FR FR0509131A patent/FR2890500B1/fr not_active Expired - Fee Related
• 2006
  • 2006-09-06 US US12/066,082 patent/US20090115510A1/en not_active Abandoned
  • 2006-09-06 EP EP06808083A patent/EP1922807A1/de not_active Withdrawn
  • 2006-09-06 WO PCT/FR2006/002056 patent/WO2007028897A1/fr active Application Filing

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