CN209964021U - Protection circuit for power amplifier during short-circuit protection test - Google Patents
Protection circuit for power amplifier during short-circuit protection test Download PDFInfo
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- CN209964021U CN209964021U CN201920879718.0U CN201920879718U CN209964021U CN 209964021 U CN209964021 U CN 209964021U CN 201920879718 U CN201920879718 U CN 201920879718U CN 209964021 U CN209964021 U CN 209964021U
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Abstract
The utility model discloses a protection circuit for power amplifier when carrying out short-circuit protection test, including current sampling circuit, operational amplifier circuit and detection circuitry, current sampling circuit carries out circuit connection through first resistance and operational amplifier circuit, and operational amplifier circuit and detection circuitry carry out circuit connection, and current sampling circuit produces voltage to send into the operational amplifier circuit through first resistance and send into after amplifying detection circuitry; the detection circuit comprises an overload voltage limit control circuit, a precise rectifying circuit and a first operational amplifier, wherein the output end of the first operational amplifier is connected with the precise rectifying circuit, the precise rectifying circuit is connected with the overload voltage limit control circuit, and the overload voltage limit control circuit is connected with the output current sampling input pin of a single chip microcomputer in the power amplifier. The utility model discloses the power amplifier can detect load current when carrying out the short-circuit protection test, and the amplitude of control output gain ensures that the power amplifier can not cause the damage of power amplifier in the short circuit.
Description
Technical Field
The utility model relates to a power amplifier technical field, concretely relates to a technique that is used for protection circuit of power amplifier when carrying out short-circuit protection test.
Background
At present, a digital power amplifier circuit applied to a professional class D power amplifier product is mainly applied on the basis of an IR driving chip, for example, the IR IRS20957S driving chip is a digital audio driving chip, an overcurrent protection circuit is integrated in the driving chip, different power amplifier output powers are designed, external parameters need to be adjusted to match different MOS (metal oxide semiconductor) tubes, and the sensitivity of a protection circuit is very difficult to adjust because the overcurrent protection and the RDS temperature rise of an external MOS have a close relation. Therefore, the power amplifier can be damaged when the output end of the power amplifier is subjected to long-term short circuit test. Therefore, a protection circuit needs to be designed for the power amplifier, a single chip microcomputer is used as a core, and the power amplifier is dynamically tracked by monitoring the output voltage and the output current of the power amplifier, the output frequency, the power supply voltage of the power amplifier and the temperature of the power MOS tube, so that the power amplifier is protected in a full range to work in a safe state.
SUMMERY OF THE UTILITY MODEL
In order to overcome the defects of the prior art, the utility model aims to provide a protection circuit for power amplifier when carrying out short-circuit protection test detects load current, controls the amplitude of output gain, ensures that the power amplifier can not cause the damage of power amplifier in the short circuit.
In order to achieve the purpose, the utility model adopts the following technical proposal:
a protection circuit for a power amplifier during a short-circuit protection test is characterized in that: the protection circuit for the power amplifier during short-circuit protection test comprises a current sampling circuit, an operational amplifier circuit and a detection circuit, wherein one end of the current sampling circuit is connected with the negative end of a loudspeaker, the other end of the current sampling circuit is connected with the positive end of the loudspeaker, the negative end of the loudspeaker is also connected with a first resistor, the current sampling circuit is used for detecting the output current of the power amplifier, the current sampling circuit is in circuit connection with the operational amplifier circuit through the first resistor, the operational amplifier circuit is in circuit connection with the detection circuit, the output current of the power amplifier generates voltage after passing through the current sampling circuit and is sent to the operational amplifier circuit through the first resistor, and the operational amplifier circuit amplifies an alternating current signal and sends the amplified alternating current signal to the detection circuit;
the detection circuit comprises an overload voltage limit control circuit, a precise rectifying circuit and a first operational amplifier, wherein the output end of the first operational amplifier is connected with the precise rectifying circuit, the precise rectifying circuit is connected with the overload voltage limit control circuit, the overload voltage limit control circuit is connected with the output current sampling input pin of a single chip microcomputer in the power amplifier, and the precise rectifying circuit rectifies an alternating current signal and then sends the rectified alternating current signal to the overload voltage limit control circuit; the overload voltage limit control circuit is used for controlling the output voltage of the power amplifier to be reduced by controlling the output amplitude of the input stage gain of the power amplifier to be reduced so as to achieve the purpose of overload voltage limit; the single chip microcomputer of the power amplifier is used for sending an instruction to close an output PWM (pulse width modulation) level signal of the power amplifier when monitoring an overcurrent signal of the power amplifier, and repeatedly carrying out periodic control to ensure that the power amplifier cannot be damaged when in short circuit; the output end of the first operational amplifier is connected with an output current sampling input pin of a singlechip in the power amplifier through an amplifying circuit and is used for finishing the monitoring function of the output current when the output load is overloaded.
The current sampling circuit comprises resistors connected in parallel, and two ends of the resistors connected in parallel are used for obtaining sampling voltage.
The operational amplifier circuit comprises a first operational amplifier and a second operational amplifier, wherein an output end pin of the first operational amplifier is directly connected with a negative electrode input end pin of the second operational amplifier, the negative electrode input end pin of the first operational amplifier is connected with a first resistor, and the first operational amplifier is provided with a floating power supply circuit.
The floating power supply loop comprises a first voltage stabilizing diode, a second voltage stabilizing diode, a third voltage stabilizing diode, a fourth voltage stabilizing diode, a first triode and a second triode, wherein the cathode of the second voltage stabilizing diode is connected with the anode of the first voltage stabilizing diode, the cathode of the second voltage stabilizing diode is further connected with the anode of the third voltage stabilizing diode, the cathode of the second voltage stabilizing diode is further connected with the cathode of the fourth voltage stabilizing diode, two ends of the first voltage stabilizing diode are connected with capacitors in parallel, and two ends of the second voltage stabilizing diode are connected with capacitors in parallel; the high-voltage-ratio operational amplifier comprises a first operational amplifier, a second operational amplifier, a third voltage-stabilizing diode, a first triode, a second triode, a third triode, a fourth triode, a first triode, a resistor, a collector, an emitter, a power supply pin of the first triode, an emitter of the first triode, a base of the second triode, a collector of the first triode, an emitter of the first triode, a power supply pin of the first operational amplifier, a cathode of the second voltage-stabilizing diode, an input terminal pin of the first operational amplifier and an anode input terminal pin of the second operational amplifier.
The overload voltage limit control circuit comprises a transconductance amplifier, a pin at the positive input end of the transconductance amplifier is connected with a precise rectifying circuit through a second resistor, the second resistor converts input current into input voltage, a pin at the negative input end of the transconductance amplifier is grounded through a resistor, a pin at the control end of the transconductance amplifier is connected with a third resistor, a fifth voltage stabilizing diode and a fourth resistor, the negative electrode of the fifth voltage stabilizing diode is connected with one end of the fourth resistor, one end of the fourth resistor is connected with one end of the third resistor, the other end of the third resistor is connected with the positive electrode of the fifth voltage stabilizing diode and then connected with the pin at the control end of the transconductance amplifier, the third resistor is the input resistor at the pin at the control end of the transconductance amplifier, and the fifth voltage stabilizing diode and the fourth resistor form a threshold damping network, when the amplitude of the input voltage of the fourth resistor is larger than the amplitude of the voltage stabilization of the fifth voltage stabilization diode, the fifth voltage stabilization diode is conducted; the transconductance amplifier is connected to an input circuit of the power amplifier, and controls the output amplitude of the input stage gain of the power amplifier to be smaller, so that the output voltage of the power amplifier is controlled to be smaller, and the purpose of overload voltage limit is achieved.
The precise rectifying circuit comprises a first rectifying diode, a second rectifying diode, a fifth resistor, a sixth resistor, a seventh resistor and a rectifying chip, the anode of the first rectifier diode is connected with the cathode of the second rectifier diode, the anode of the first rectifier diode is the current input end of the precision rectifier circuit, the negative electrode of the first rectifying diode is connected with the fifth resistor and then grounded, the negative electrode of the first rectifying diode is connected with the pin of the positive input end of the rectifying chip, the cathode of the second rectifier diode is connected with one end of the sixth resistor, the other end of the sixth resistor is connected with the pin of the cathode input end of the rectifier chip, and the seventh resistor is connected between a negative input end pin and an output end pin of the rectifying chip, and the precision rectifying circuit is used for providing accurate and interference-free reference voltage.
The amplifying circuit connected between the output end of the first operational amplifier and the output current sampling input pin of the singlechip in the power amplifier comprises a differential amplifying circuit which is composed of an eighth resistor, a first capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, a second capacitor and a second operational amplifier.
The utility model discloses following beneficial effect has:
the utility model designs the current sampling circuit, the operational amplifier circuit and the detection circuit, the current sampling circuit finishes the current sampling of the output current of the output load, the voltage is generated by the first resistor, and is sent to the operational amplifier circuit, the operational amplifier circuit amplifies the alternating current signal and sends the amplified alternating current signal to the detection circuit, a precision rectification circuit in the detection circuit rectifies the alternating current signal and sends the rectified alternating current signal to an overload voltage limit control circuit, the overload voltage limit control circuit is used for controlling the output amplitude of the input stage gain of the power amplifier to be reduced, when the singlechip of the power amplifier monitors an overcurrent signal of the power amplifier, the singlechip sends an instruction to close an output PWM (pulse width modulation) level signal of the power amplifier, and the power amplifier is controlled repeatedly and periodically to ensure that the power amplifier cannot be damaged in the short circuit process; the output end of the first operational amplifier is connected with an output current sampling input pin of a singlechip in the power amplifier through an amplifying circuit and is used for finishing the monitoring function of the output current when the output load is overloaded. Therefore, the utility model discloses a protection circuit of power amplifier when carrying out the short-circuit protection test detects load current, and the amplitude of control output gain ensures that the power amplifier can not cause the damage of power amplifier in the short circuit. The utility model discloses well output load embodiment indicates loudspeaker.
In particular, the operational amplifier circuit of the present invention has high resistance to common mode input due to the two-stage operational amplifier and the floating power supply of the first operational amplifier; the differential modulus is not attenuated; thereby accurately detecting the load current. The reference point of the floating power supply in the floating power supply circuit of the first operational amplifier is the reference point of the power amplifier output end, but not the reference point of the ground, so the ground is floating relative to the actual ground. The principle of the floating power supply is that the output power supplies of the first voltage stabilizing diode and the second voltage stabilizing diode are all established by the output end, because the output end is connected to the positive end of the loudspeaker through the sampling resistor and then returns to the ground of the power supply from the negative end of the loudspeaker, voltage is generated on the sampling resistor, and thus the reference point is changed voltage and is floating. Because the voltage generated on the sampling resistor changes along with the input of the signal, the first operational amplifier needs to be powered by a floating power supply, so that the problem that the power supply of the first operational amplifier is unstable due to the change of the reference point voltage caused by the input current of the sampling resistor is solved. Because the first operational amplifier solves the problem of reference point voltage change caused by the sampling resistor, the second operational amplifier does not use a floating power supply for power supply, and the circuit structure is simple.
Especially the utility model discloses overload voltage limit control circuit among the detection circuitry has set up the input circuit that transconductance amplifier is connected to the power amplifier, consequently, the output amplitude of transconductance amplifier control power amplifier input stage gain diminishes, thereby the output voltage of control power amplifier diminishes, reach the purpose of overload voltage limit, that is to say can detect output current when the output load transships like this, control output gain's amplitude, thereby make the output amplitude have a process that diminishes, thereby reach the power amplifier reliable work under the safe condition. Therefore, when the single chip microcomputer automatically monitors the overcurrent signal of the power amplifier during long-term short-circuit protection test, the single chip microcomputer operation control pin enables the power amplifier to output a PWM (pulse width modulation) level automatic closing signal, and repeated periodic control is carried out, so that the power amplifier is prevented from being damaged during short circuit.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic block diagram of the present invention;
fig. 2 is a circuit diagram of the operational amplifier circuit of the present invention;
fig. 3 is a circuit structure diagram of the detection circuit of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments with reference to the accompanying drawings.
Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; for a better understanding of the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not indicated or implied that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are used only for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms will be understood by those skilled in the art according to the specific circumstances.
As shown in fig. 1-3, the present invention is used for a protection circuit of a power amplifier during a short-circuit protection test, which includes a current sampling circuit, an operational amplifier circuit and a detection circuit. ATTINY861A-SU singlechip 0001 in FIG. 1 is a singlechip in the power amplifier, pin 17 of the singlechip 0001 is an SD output control pin, and is connected with SD execution circuit 0009 in FIG. 1, and SD is a shutdown pin. The output current sampling + overload voltage limiting circuit is 0004, wherein the output current sampling refers to a current sampling circuit, the overload voltage limiting circuit refers to an overload voltage limiting control circuit in a detection circuit, and a pin 13 of the single chip microcomputer 0001 is an output current sampling input pin.
One end of the current sampling circuit is connected with the negative end of the horn, the other end of the current sampling circuit is connected with the positive end of the horn, the negative end of the horn is further connected with the first resistor, the current sampling circuit is used for detecting the output current of the power amplifier, the current sampling circuit is in circuit connection with the operational amplifier circuit through the first resistor R58, the operational amplifier circuit is in circuit connection with the detection circuit, the output current of the power amplifier generates voltage after passing through the current sampling circuit and is sent into the operational amplifier circuit through the first resistor R58, and the operational amplifier circuit amplifies an alternating current signal and sends the amplified alternating current signal into the detection circuit. The detection circuit comprises an overload voltage limit control circuit, a precision rectification circuit and a first operational amplifier IC1A, wherein the output end of the first operational amplifier IC1A is connected with the precision rectification circuit, the precision rectification circuit is connected with the overload voltage limit control circuit, the overload voltage limit control circuit is connected with an output current sampling input pin 13 of a single chip microcomputer in the power amplifier, the precision rectification circuit rectifies an alternating current signal and then sends the alternating current signal to the overload voltage limit control circuit, and the overload voltage limit control circuit is used for controlling the output amplitude of the input stage gain of the power amplifier to be reduced so as to control the output voltage of the power amplifier to be reduced and achieve the purpose of overload voltage limit; the single chip microcomputer of the power amplifier is used for sending an instruction to close an output PWM (pulse width modulation) level signal of the power amplifier when monitoring an overcurrent signal of the power amplifier, and repeatedly carrying out periodic control to ensure that the power amplifier cannot be damaged when in short circuit; the output end of the first operational amplifier IC1A is connected to the output current sampling input pin 13 of the single chip in the power amplifier through an amplifying circuit, so as to complete the monitoring function of the output current when the output load is overloaded. The current sampling circuit comprises resistors connected in parallel, and two ends of the resistors connected in parallel are used for obtaining sampling voltage. PWM refers to pulse width modulation, in which the output voltage is controlled by changing the pulse width and the output frequency is controlled by changing the period.
The operational amplifier circuit comprises a first operational amplifier IC6 and a second operational amplifier IC4, wherein a pin 1 of an output end pin of the first operational amplifier IC6 is directly connected with a pin 3 of a negative input end pin of the second operational amplifier IC4, a pin of a negative input end pin of the first operational amplifier IC6 is connected with a first resistor R58, a first resistor R58 is connected with the current sampling circuit in series, and the first operational amplifier IC6 is provided with a floating power supply loop.
As shown in fig. 2: the operational amplifier circuit comprises a floating power supply circuit of a first operational amplifier IC6, a second operational amplifier IC4 and a first operational amplifier IC6, wherein the first operational amplifier IC6 is an AD629 precision differential amplifier of ANALOG corporation, has a very high input common-mode voltage range, can accurately measure differential signals under the condition of high common-mode voltage of +/-270V at most, and the second operational amplifier IC4 is an LMP7707MF precision operational amplifier. The pin 1 of the output end of the first operational amplifier IC6 is directly connected with the pin 3 of the negative input end of the second operational amplifier IC4, the floating power supply loop comprises a first voltage-stabilizing diode D51, a second voltage-stabilizing diode D50, a third voltage-stabilizing diode D12, a fourth voltage-stabilizing diode D13, a first triode TR1 and a second triode TR2, the negative electrode of the second voltage-stabilizing diode D50 is connected with the positive electrode of the first voltage-stabilizing diode D51, the negative electrode of the second voltage-stabilizing diode D50 is further connected with the positive electrode of the third voltage-stabilizing diode D12, the negative electrode of the second voltage-stabilizing diode D50 is further connected with the negative electrode of the fourth voltage-stabilizing diode D13, the two ends of the first voltage-stabilizing diode D51 are connected with capacitors, namely a capacitor C110 and a capacitor C111 which are connected in parallel, and the two ends of the second voltage-stabilizing diode D50 are connected with capacitors, namely a capacitor C107 and a capacitor C108 which are connected in parallel. A resistor R60 is connected between the cathode of the first zener diode D51 and the cathode of the third zener diode D12, a resistor R61 is connected between the anode of the second zener diode D50 and the anode of the fourth zener diode D13, the anode of the third zener diode D12 is connected to the base of the first transistor TR1, the cathode of the first zener diode D51 is connected to the collector of the first transistor TR1, the emitter of the first transistor TR1 is connected to the positive power supply pin of the first operational amplifier IC6, the anode of the fourth zener diode D13 is connected to the base of the second transistor TR2, the anode of the second zener diode D50 is connected to the collector of the first transistor TR1, the emitter of the first transistor TR1 is connected to the negative power supply pin of the first operational amplifier IC6, and the cathode of the second zener diode D50 is connected to the positive power supply pin of the first operational amplifier IC6, The positive input pin of the second operational amplifier IC6 is connected. The first triode TR1 and the second triode TR2 are NPN + PNP complementary triodes, and are integrated and packaged to form a packaging piece T8, so that the consistency is better, and the linear voltage stabilizing function is realized.
The negative input terminal pin of the first operational amplifier IC6 is connected to a first resistor R58, and the first resistor R58 is connected in series with a current sampling circuit: the current sampling circuit is characterized in that one end of the current sampling circuit is connected with the negative end of the loudspeaker, the other end of the current sampling circuit is connected with the positive end of the loudspeaker, and a pin of the negative input end of the first operational amplifier IC6 is connected with the negative end of the loudspeaker through a first resistor R58, namely the first resistor R58 is connected with the end, connected with the negative end of the loudspeaker, of the current sampling circuit.
The current sampling circuit comprises resistors connected in parallel, such as four resistors, namely a resistor R211, a resistor R218, a resistor R219 and a resistor R224, wherein the resistor R211, the resistor R218, the resistor R219 and the resistor R224 are connected in parallel, and two ends of the parallel-connected resistors are used for obtaining a sampling voltage. The output pin of the first operational amplifier IC6 is also connected in series with a first resistor R58 through a resistor R59. The output power of the first voltage stabilizing diode D51 and the second voltage stabilizing diode D50 is established by an output end, and the output end is connected to the positive end of the horn through a resistor connected in parallel.
The operational amplifier circuit in the utility model has high resistance to common mode input due to the design of two-stage operational amplifier; the differential modulus is not attenuated, and the load current is accurately detected. Based on that first operational amplifier IC6 is ANALOG's AD629 is a precision differential amplifier, has very high input common mode voltage range, can be in the high common mode voltage condition of highest 270V accurate measurement difference signal, as in the figure, first operational amplifier IC6 is passed through resistance R59/R58 and is enlargied 33 times weak alternating current signal earlier, and then send to second operational amplifier IC 4's 3 feet, then enlargies the alternating current model again through first operational amplifier IC6, ensures that the linear integrity of the alternating current signal of enlarging does not have the signal of distortion, consequently the utility model discloses so used two-stage operational amplifier.
The utility model discloses the reference point of the floating power supply in the floating power supply return circuit of first operational amplifier IC6 in the operational amplifier circuit is with the power amplifier output as the reference point, and not with ground as the reference point, so for actually ground, this ground is floated. The principle of the floating power supply is that the output power supplies of the first voltage stabilizing diode D51 and the second voltage stabilizing diode D50 are all established by the output end of the power amplifier, wherein the output end of the power amplifier corresponds to the positive end of the loudspeaker, and the output end is connected to the positive end of the loudspeaker through the sampling resistor R211, the resistor R218, the resistor R219 and the resistor R224, and then returns to the ground of the power supply from the negative end of the loudspeaker, so that voltage is generated on the sampling resistor, and thus the reference point is changed voltage, and is floating. The floating power supply of the first operational amplifier IC6 has the advantage of improving the power supply ripple rejection ratio PSRR of the operational amplifier IC6, where PSRR is a quantity used to describe the influence of the power supply on the output signal, and the larger the PSRR, the smaller the influence of the power supply on the output signal. An unstable supply voltage tends to affect the waveform of the output signal, the magnitude of which depends on the PSRR. Therefore, the design of decoupling design and power supply of operational amplifier etc. is emphasized, as mentioned above, the utility model discloses in use R229, D51, R230, D20, C110, C111, C107, C108 to constitute the power supply circuit of floating power supply, through the circuit that T8, D12, D13, R60, R61 constitute after the voltage is stabilized from the main voltage to voltage reduction, supply power to first operational amplifier IC6 after the linear constant current of triode in T8, provide a stable DC power supply system of low ripple for first operational amplifier IC6, even ensure that first operational amplifier IC6 is under the power amplifier output and then the voltage that supply power voltage suddenly changes low fluctuation, the power supply of first operational amplifier IC6 is still stable, even under the power amplifier output is under the condition of big dynamic output, still have very high power supply rejection ratio, thereby ensure the measurement accuracy of first operational amplifier IC 6. And then the working stability of the power amplifier is improved. Operational amplifier is short for operational amplifier, and power amplifier is short for amplifier. PSRR is an abbreviation of Power Supply Rejection Ratio, and chinese contains meaning "Power Supply ripple Rejection Ratio". That is, PSRR represents the ratio of the two voltage gains obtained when the input and power sources are considered as two independent signal sources.
As shown in fig. 3, the detection circuit includes an overload voltage limit control circuit, a precision rectifying circuit, and a first operational amplifier IC 1A. The overload voltage limit control circuit comprises a transconductance amplifier IC9A, a pin of a positive electrode input end of the transconductance amplifier IC9A is connected with the precision rectifying circuit through a second resistor R82, and the second resistor converts input current into input voltage.
A pin of a negative input end of the transconductance amplifier IC9A is grounded through a resistor R83, a pin 2 of a control end of the transconductance amplifier IC9A is connected with a third resistor R233, a fifth voltage-stabilizing diode D53 and a fourth resistor R236, a negative electrode of the fifth voltage-stabilizing diode D53 is connected with one end of the fourth resistor R236, one end of the fourth resistor R236 is connected with one end of the third resistor R233, the other end of the third resistor R233 is connected with an anode of the fifth voltage-stabilizing diode D53 and is further connected with a pin 2 of a control end of the transconductance amplifier IC9A, an input resistor of the pin 2 of the control end of the transconductance amplifier R233 is connected with the third resistor R233, the fifth voltage-stabilizing diode D53 and the fourth resistor R236 form a threshold damping network, and when the amplitude of the input voltage of the fourth resistor R236 is greater than the amplitude of the voltage-stabilizing diode D53, the fifth voltage-stabilizing diode D53 is turned on; the transconductance amplifier IC9A is connected to the input circuit of the power amplifier, and the transconductance amplifier controls the output amplitude of the input stage gain of the power amplifier to be smaller, so as to control the output voltage of the power amplifier to be smaller, thereby achieving the purpose of overload voltage limit. The overload voltage limit is a process of controlling the amplitude of output gain by detecting the output current when the output load is overloaded, so that the output amplitude of the output gain is reduced, and the power amplifier can reliably work in a safe state. The threshold damping network formed by the fifth zener diode D53 and the fourth resistor R236 means that the input amplitude reaches a certain state, which depends on the regulated voltage value of the fifth zener diode D53, and when the amplitude regulator tube with a voltage larger than that of the fifth zener diode D53 is turned on.
The precise rectifying circuit comprises a first rectifying diode D1, a second rectifying diode D2, a fifth resistor R6, a sixth resistor R8, a seventh resistor R9 and a rectifying chip IC1B, wherein the anode of the first rectifying diode D1 is connected with the cathode of the rectifying diode D2, the anode of the first rectifying diode D1 is a current input end of the precise rectifying circuit, the cathode of the first rectifying diode D1 is connected with the fifth resistor R6 and then grounded, the cathode of the first rectifying diode D1 is connected with the anode input end pin of the rectifying chip IC1B, the cathode of the second rectifying diode D2 is connected with one end of the sixth resistor R8, the other end of the sixth resistor R8 is connected with the cathode input end pin of the rectifying chip IC1B, the seventh resistor R9 is connected between the cathode input end pin of the rectifying chip IC1B and the output end pin, and the precise rectifying circuit is used for providing accurate and interference-free reference voltage; the output end of the rectifying chip IC1B is further connected with two triodes of a packaged constant current source connection method, and the output end pin of the transconductance amplifier IC9A is also connected with the two triodes of the packaged constant current source connection method for controlling the internal voltage of the transconductance amplifier. The model of the precision rectifier specifically illustrated to provide a more accurate reference voltage IC1B for the subsequent overcurrent limiting circuit is TL074C by the company TI. The precise rectifying circuit can complete the level conversion of the effective value after sampling the output waveform, rectify the pulsating AC-changed voltage waveform into smooth output DC voltage and provide more precise, more reliable and non-interference reference voltage. Therefore, the reference is made for the following control circuit, for example, when the power amplifier outputs 1V alternating current, the output direct current voltage corresponding to the precise rectification circuit is 0.045V direct current voltage.
The current input end of the precise rectifying circuit is connected with an operational amplifier IC1A, the positive electrode input end of the operational amplifier IC1A is used for inputting a voltage signal of a load, and a feedback loop resistor is arranged between the negative electrode input end and the output end of the operational amplifier IC1A and used for changing the in-phase amplification factor of the operational amplifier IC 1A. The feedback loop resistor comprises a sixth resistor 12 and a seventh resistor 13 which are connected in series, the two ends of the seventh resistor 13 are connected with a rheostat VR1, and the change of VR1 is equivalent to the change of the amplification factor of the operational amplifier IC 1A.
The output end of the first operational amplifier is also provided with a monitoring circuit of output current, namely an amplifying circuit connected between the output end of the first operational amplifier and an output current sampling input pin of a singlechip in the power amplifier, the monitoring circuit comprises an eighth resistor R56, a first capacitor C27, a ninth resistor R63, a tenth resistor R57, an eleventh resistor R64, a second capacitor C29 and a second operational amplifier IC8B to form a differential amplifying circuit, the pin of the positive input end of the second operational amplifier IC8B is connected with the eighth resistor R56 to form the input end of the amplifying circuit, the pin of the positive input end of the second operational amplifier IC8B is also connected with one end of the ninth resistor R63, the other end of the ninth resistor R63 is grounded, two ends of the ninth resistor R63 are connected with the first capacitor C27 in parallel, the pin of the negative input end of the second operational amplifier IC8B is grounded through the tenth resistor R57, and the eleventh resistor R64 is connected between the negative input end of the second operational amplifier IC8B, the second capacitor C29 is connected in parallel to two ends of the eleventh resistor R64. Wherein R56 is input resistance, R63 is divider resistance, C27 is bypass high frequency interference, R57 is ground divider resistance, R64 is the feedback resistance of operational amplifier, C29 feedback capacitance, IC8 is TL074C of TI company.
It should be noted that the above embodiments are only preferred embodiments of the present invention and the technical principles applied, and any changes or substitutions which can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the protection scope of the present invention.
Claims (7)
1. A protection circuit for a power amplifier during a short-circuit protection test is characterized in that: the protection circuit for the power amplifier during short-circuit protection test comprises a current sampling circuit, an operational amplifier circuit and a detection circuit, wherein one end of the current sampling circuit is connected with the negative end of a loudspeaker, the other end of the current sampling circuit is connected with the positive end of the loudspeaker, the negative end of the loudspeaker is also connected with a first resistor, the current sampling circuit is used for detecting the output current of the power amplifier, the current sampling circuit is in circuit connection with the operational amplifier circuit through the first resistor, the operational amplifier circuit is in circuit connection with the detection circuit, the output current of the power amplifier generates voltage after passing through the current sampling circuit and is sent to the operational amplifier circuit through the first resistor, and the operational amplifier circuit amplifies an alternating current signal and sends the amplified alternating current signal to the detection circuit;
the detection circuit comprises an overload voltage limit control circuit, a precise rectifying circuit and a first operational amplifier, wherein the output end of the first operational amplifier is connected with the precise rectifying circuit, the precise rectifying circuit is connected with the overload voltage limit control circuit, the overload voltage limit control circuit is connected with the output current sampling input pin of a single chip microcomputer in the power amplifier, and the precise rectifying circuit rectifies an alternating current signal and then sends the rectified alternating current signal to the overload voltage limit control circuit; the overload voltage limit control circuit is used for controlling the output voltage of the power amplifier to be reduced by controlling the output amplitude of the input stage gain of the power amplifier to be reduced so as to achieve the purpose of overload voltage limit; the single chip microcomputer of the power amplifier is used for sending an instruction to close an output PWM (pulse width modulation) level signal of the power amplifier when monitoring an overcurrent signal of the power amplifier, and repeatedly carrying out periodic control to ensure that the power amplifier cannot be damaged when in short circuit; the output end of the first operational amplifier is connected with an output current sampling input pin of a singlechip in the power amplifier through an amplifying circuit and is used for finishing the monitoring function of the output current when the output load is overloaded.
2. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 1, wherein: the current sampling circuit comprises resistors connected in parallel, and two ends of the resistors connected in parallel are used for obtaining sampling voltage.
3. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 1, wherein: the operational amplifier circuit comprises a first operational amplifier and a second operational amplifier, wherein an output end pin of the first operational amplifier is directly connected with a negative electrode input end pin of the second operational amplifier, the negative electrode input end pin of the first operational amplifier is connected with a first resistor, and the first operational amplifier is provided with a floating power supply circuit.
4. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 3, wherein: the floating power supply loop comprises a first voltage stabilizing diode, a second voltage stabilizing diode, a third voltage stabilizing diode, a fourth voltage stabilizing diode, a first triode and a second triode, wherein the cathode of the second voltage stabilizing diode is connected with the anode of the first voltage stabilizing diode, the cathode of the second voltage stabilizing diode is further connected with the anode of the third voltage stabilizing diode, the cathode of the second voltage stabilizing diode is further connected with the cathode of the fourth voltage stabilizing diode, two ends of the first voltage stabilizing diode are connected with capacitors in parallel, and two ends of the second voltage stabilizing diode are connected with capacitors in parallel; the high-voltage-ratio operational amplifier comprises a first operational amplifier, a second operational amplifier, a third voltage-stabilizing diode, a first triode, a second triode, a third triode, a fourth triode, a first triode, a resistor, a collector, an emitter, a power supply pin of the first triode, an emitter of the first triode, a base of the second triode, a collector of the first triode, an emitter of the first triode, a power supply pin of the first operational amplifier, a cathode of the second voltage-stabilizing diode, an input terminal pin of the first operational amplifier and an anode input terminal pin of the second operational amplifier.
5. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 4, wherein: the overload voltage limit control circuit comprises a transconductance amplifier, a pin at the positive input end of the transconductance amplifier is connected with a precise rectifying circuit through a second resistor, the second resistor converts input current into input voltage, a pin at the negative input end of the transconductance amplifier is grounded through a resistor, a pin at the control end of the transconductance amplifier is connected with a third resistor, a fifth voltage stabilizing diode and a fourth resistor, the negative electrode of the fifth voltage stabilizing diode is connected with one end of the fourth resistor, one end of the fourth resistor is connected with one end of the third resistor, the other end of the third resistor is connected with the positive electrode of the fifth voltage stabilizing diode and then connected with the pin at the control end of the transconductance amplifier, the third resistor is the input resistor at the pin at the control end of the transconductance amplifier, and the fifth voltage stabilizing diode and the fourth resistor form a threshold damping network, when the amplitude of the input voltage of the fourth resistor is larger than the amplitude of the voltage stabilization of the fifth voltage stabilization diode, the fifth voltage stabilization diode is conducted; the transconductance amplifier is connected to an input circuit of the power amplifier, and controls the output amplitude of the input stage gain of the power amplifier to be smaller, so that the output voltage of the power amplifier is controlled to be smaller, and the purpose of overload voltage limit is achieved.
6. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 1, wherein: the precise rectifying circuit comprises a first rectifying diode, a second rectifying diode, a fifth resistor, a sixth resistor, a seventh resistor and a rectifying chip, the anode of the first rectifier diode is connected with the cathode of the second rectifier diode, the anode of the first rectifier diode is the current input end of the precision rectifier circuit, the negative electrode of the first rectifying diode is connected with the fifth resistor and then grounded, the negative electrode of the first rectifying diode is connected with the pin of the positive input end of the rectifying chip, the cathode of the second rectifier diode is connected with one end of the sixth resistor, the other end of the sixth resistor is connected with the pin of the cathode input end of the rectifier chip, and the seventh resistor is connected between a negative input end pin and an output end pin of the rectifying chip, and the precision rectifying circuit is used for providing accurate and interference-free reference voltage.
7. The protection circuit for the power amplifier when performing the short-circuit protection test according to claim 1, wherein: the amplifying circuit connected between the output end of the first operational amplifier and the output current sampling input pin of the singlechip in the power amplifier comprises a differential amplifying circuit which is composed of an eighth resistor, a first capacitor, a ninth resistor, a tenth resistor, an eleventh resistor, a second capacitor and a second operational amplifier.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920879718.0U CN209964021U (en) | 2019-06-12 | 2019-06-12 | Protection circuit for power amplifier during short-circuit protection test |
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| CN201920879718.0U CN209964021U (en) | 2019-06-12 | 2019-06-12 | Protection circuit for power amplifier during short-circuit protection test |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111277940A (en) * | 2020-01-23 | 2020-06-12 | 西安广和通无线通信有限公司 | Loudspeaker detection circuit, method and loudspeaker circuit |
| CN111766508A (en) * | 2020-07-21 | 2020-10-13 | 深圳宝龙达信创科技股份有限公司 | Short-circuit protection testing device |
| CN112180147A (en) * | 2020-09-25 | 2021-01-05 | 加特兰微电子科技(上海)有限公司 | Power amplifier output impedance abnormity detection method, detection device and related device |
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2019
- 2019-06-12 CN CN201920879718.0U patent/CN209964021U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111277940A (en) * | 2020-01-23 | 2020-06-12 | 西安广和通无线通信有限公司 | Loudspeaker detection circuit, method and loudspeaker circuit |
| CN111766508A (en) * | 2020-07-21 | 2020-10-13 | 深圳宝龙达信创科技股份有限公司 | Short-circuit protection testing device |
| CN112180147A (en) * | 2020-09-25 | 2021-01-05 | 加特兰微电子科技(上海)有限公司 | Power amplifier output impedance abnormity detection method, detection device and related device |
| CN112180147B (en) * | 2020-09-25 | 2022-12-23 | 加特兰微电子科技(上海)有限公司 | Power amplifier output impedance abnormity detection method, detection device and related device |
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