A power amplifier protection circuit

Abstract

The application provides a power amplifier protection circuit, which comprises an input filter unit, a detection unit, a protection unit and an output filter unit. The input filter unit is connected to the output filter unit through the protection unit, the input filter unit is connected to the detection unit, and the detection unit is connected to the protection unit. The input filter unit is used for primary filtering of an input power supply to eliminate high-frequency noise and reduce low-frequency noise and ripple amplitude. The detection unit is used for detecting a power supply signal output by the input filter unit and sending a control signal to the protection unit according to the detection. The protection unit is used for controlling the output of the input filter unit to the output filter unit to supply power to the power amplifier according to the control signal. The output filter unit is used for secondary filtering of the power supply signal output by the input filter unit and passing through the protection unit to further eliminate high-frequency noise and low-frequency ripple. The circuit has the characteristics of comprehensive protection function, high sensitivity detection and simplified design structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic circuits, and relates to a power amplifier, in particular to a power amplifier protection circuit. BACKGROUND

[0002] At present, power amplifiers are widely used in electronic devices, and some power amplifiers have strict requirements for the specific operation sequence of power-on and power-off of the power supply. When the operation is improper and the sequence is wrong, problems such as instantaneous excessive current and voltage overshoot are easily caused, which may lead to damage of the internal circuit of the power amplifier, such as transistor breakdown and capacitor damage, thereby shortening the service life of the power amplifier, causing device failure and increasing maintenance cost.

[0003] In the prior art, a single current detection resistor or a voltage comparator is usually used to determine whether the power amplifier is in an abnormal working state, but there are some defects, such as a large number of detection and control elements are needed for the design based on discrete components, which increases the circuit complexity and the difficulty of design and debugging, some circuits can only provide a single protection function (such as overcurrent protection or short circuit protection), which cannot meet the demand of comprehensive protection, the sensitivity of the detection circuit is not enough, which leads to the power amplifier cannot be quickly cut off when the fault occurs, and there is a risk of damage. CONTENT OF THE UTILITY MODEL

[0004] In order to solve the above problems of the prior art, the application provides a power amplifier protection circuit which has the characteristics of comprehensive protection function, high sensitivity detection and simplified design structure.

[0005] In order to achieve the above purpose, the utility model adopts the following technology:

[0006] A power amplifier protection circuit, comprising an input filter unit, a detection unit, a protection unit and an output filter unit, the input filter unit is connected to the output filter unit through the protection unit, the input filter unit is connected to the detection unit, and the detection unit is connected to the protection unit;

[0007] The input filter unit is used for primary filtering of the input power supply to eliminate high-frequency noise and reduce low-frequency noise and ripple amplitude;

[0008] The detection unit is used for detecting the power supply signal output by the input filter unit and sending a control signal to the protection unit according to the detection;

[0009] The protection unit is used for controlling the output of the input filter unit to the output filter unit to supply power to the power amplifier according to the control signal;

[0010] The output filter unit is used for secondary filtering of the power supply signal output by the input filter unit and passing through the protection unit to further eliminate high-frequency noise and low-frequency ripple.

[0011] Further, the detection unit comprises resistors R1, R2, R3, R4 and a triode D1; the protection unit comprises a field effect tube U1, and the field effect tube U1 adopts VBZA4425;

[0012] One end of the resistors R1 and R2 is connected to the output end of the input filter unit, the other end of the resistor R1 is connected to one end of the resistor R4, the other end of the resistor R4 is connected to a reference voltage and the b electrode of the triode D1, the other end of the resistor R2 is connected to the c electrode of the triode D1 and one end of the resistor R3, and the e electrode of the triode D1 is connected to GND.

[0013] The other end of the resistor R3 is connected to the 4 pin of the field effect tube U1, the 1 pin, 2 pin and 3 pin of the field effect tube U1 are connected together and connected to the output end of the input filter unit, and the 5 pin, 6 pin, 7 pin and 8 pin of the field effect tube U1 are connected together and connected to the input end of the output filter unit.

[0014] Further, the input filter unit comprises capacitors C1 and C2 and an inductor L1, one end of the capacitor C1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to one end of the capacitor C2, the other end of the capacitor C1 and the other end of the capacitor C2 are respectively connected to GND, one end of the inductor L1 is used for connecting an input power supply, and the other end of the inductor L1 is used as an output end of the input filter unit and is used for connecting the detection unit and the protection unit.

[0015] Further, the output filter unit comprises capacitors C3 and C4 and an inductor L2, one end of the capacitor C3 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the capacitor C4, the other end of the capacitor C3 and the other end of the capacitor C4 are respectively connected to GND, one end of the inductor L2 is used as an input of the output filter unit and is used for connecting the protection unit, and the other end of the inductor L2 is used as an output end of the output filter unit.

[0016] The utility model has the advantages that:

[0017] 1. The detection unit detects the power supply signal output by the input filter unit and sends a control signal to the protection unit according to the detection result, and the protection unit turns on or off the power supply signal to the output filter unit according to the control signal, so that the protection mechanism of the power amplifier is realized;

[0018] 2. The detection unit can quickly respond when a fault occurs through the cooperation of the voltage division network and the triode, and the field effect tube is used for power supply disconnection, and the field effect tube adopts the VBZA4425 chip to realize multiple protection mechanisms such as overcurrent, short circuit, overheating and undervoltage, thereby improving the safety and reliability of the power amplifier operation;

[0019] 3. Compared with the discrete component design of the prior art, the number of components is reduced, and the design difficulty and cost are reduced;

[0020] 4. By using an LC filter circuit for two-stage filtering, the purity of the output signal can be significantly improved, avoiding ripples and noise interference. Attached Figure Description

[0021] Figure 1 This is a block diagram of the power amplifier protection circuit according to an embodiment of this application. Detailed Implementation

[0022] To make the objectives, technical solutions and advantages of the present utility model clearer, the implementation methods of the present utility model will be described in detail below with reference to the accompanying drawings. However, the embodiments described in the present utility model are only some embodiments of the present utility model, and not all embodiments.

[0023] This application provides a power amplifier protection circuit, such as... Figure 1 As shown, it includes an input filtering unit, a detection unit, a protection unit, and an output filtering unit. The input filtering unit is connected to the output filtering unit through the protection unit, the input filtering unit is connected to the detection unit, and the detection unit is connected to the protection unit.

[0024] The input filtering unit performs initial filtering on the input power supply to eliminate high-frequency noise and reduce low-frequency noise and ripple amplitude; the detection unit detects the power signal output by the input filtering unit and sends a control signal to the protection unit based on the detection; the protection unit controls the output of the input filtering unit to the output filtering unit to supply power to the power amplifier based on the control signal; the output filtering unit performs secondary filtering on the power signal output by the input filtering unit and passed through the protection unit to further eliminate high-frequency noise and low-frequency ripple.

[0025] Specifically, the detection unit includes resistors R1, R2, R3, and R4, and transistor D1; the protection unit includes field-effect transistor U1, which is a VBZA4425.

[0026] One end of resistors R1 and R2 is connected to the output of the input filter unit. The other end of resistor R1 is connected to one end of resistor R4. The other end of resistor R4 is connected to a reference voltage and the base (b) of transistor D1. The other end of resistor R2 is connected to the collector (c) of transistor D1 and one end of resistor R3. The emitter (e) of transistor D1 is connected to GND. The other end of resistor R3 is connected to pin 4 of MOSFET U1. Pins 1, 2, and 3 of MOSFET U1 are connected together and connected to the output of the input filter unit. Pins 5, 6, 7, and 8 of MOSFET U1 are connected together and connected to the input of the output filter unit.

[0027] The resistance R1 and the resistance R2 divide the voltage of the primary filtered power supply signal, and then provide to the b electrode of the triode D1. When the voltage signal or the current signal after the voltage division exceeds the set threshold value, the b electrode of the triode D1 reaches the conduction threshold value, the triode D1 is turned on, and the voltage of the 4 pin of the field effect transistor U1 is pulled down to GND through the resistance R3. When the voltage is lower than a certain threshold value, the field effect transistor U1 is turned off, and the transmission of the power supply signal from the output end of the input filter unit to the input end of the output filter unit is interrupted, so that the protection of the power amplifier is realized. When the voltage signal or the current signal after the voltage division changes, so that the triode D1 is restored to the off state, the resistance R3 is only connected with the other end of the resistance R2, the voltage of the 4 pin of the field effect transistor U1 is pulled up, the field effect transistor U1 is turned on, and the transmission of the power supply signal from the output end of the input filter unit to the input end of the output filter unit is restored.

[0028] Since the field effect transistor U1 uses the VBZA4425 chip, it has the following functions:

[0029] Overcurrent protection (OCP): detecting whether the output current exceeds the set threshold value of the chip; short circuit protection (SCP): when the output end is short-circuited, the power amplifier output is quickly cut off; overheat protection (OTP): the internal temperature sensor of the chip monitors the overheat condition and triggers the protection; under-voltage protection (UVP): when the input voltage is lower than the set value, the output work is stopped.

[0030] On this basis, preferably, the b electrode of the triode D1 is also connected with GND through the resistance R5, which reserves a debugging bit for the circuit and can be used as an adjustment feedback voltage division ratio (in cooperation with the resistance R6).

[0031] On this basis, preferably, the 5 pin of the field effect transistor U1 is also connected with GND through the resistance R6, which plays a role of current negative feedback.

[0032] Specifically, the input filter unit includes a capacitor C1, a capacitor C2 and an inductor L1. One end of the capacitor C1 is connected with one end of the inductor L1, the other end of the inductor L1 is connected with one end of the capacitor C2, the other end of the capacitor C1 and the other end of the capacitor C2 are respectively connected with GND, one end of the inductor L1 is used for connecting the input power supply, and the other end of the inductor L1 is used as the output end of the input filter unit and is used for connecting the detection unit and the protection unit.

[0033] Among them, the capacitor C1 and the capacitor C2 are used to reduce the low-frequency noise and the ripple amplitude, and the inductor L1 is used to hinder the high-frequency noise to eliminate the high-frequency noise and improve the purity of the input power supply. When designing, the rated current of the inductor L1 must be greater than the maximum load current to avoid magnetic saturation; the voltage withstand value of the capacitor C1 and the capacitor C2 needs to be higher than the input power supply voltage, and it is recommended to leave at least 30% margin.

[0034] Specifically, the output filter unit includes a capacitor C3, a capacitor C4, and an inductor L2, one end of the capacitor C3 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the capacitor C4, the other end of the capacitor C3 and the other end of the capacitor C4 are respectively connected to GND, one end of the inductor L2 is used as an input of the output filter unit and is used for connecting the protection unit, and the other end of the inductor L2 is used as an output end of the output filter unit.

[0035] The capacitor C3 is used for further eliminating low-frequency ripple, the capacitor C4 is used for further eliminating high-frequency noise, and the inductor L2 is used for suppressing high-frequency interference and improving output signal quality. The inductor L2 is selected to be a low DC resistance and high-current-resistant element, and the capacitance values of the parallel filter capacitors C3 and C4 are reasonably matched to avoid resonance problems.

[0036] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application.

Claims

1. A power amplifier protection circuit, characterized by, The input filter unit, the detection unit, the protection unit and the output filter unit are connected in series, the input filter unit is connected to the detection unit, and the detection unit is connected to the protection unit; The input filter unit is used to filter the input power supply to eliminate high-frequency noise and reduce low-frequency noise and ripple amplitude; The detection unit is used to detect the power supply signal output by the input filter unit and send a control signal to the protection unit according to the detection; The protection unit is used to control the output of the input filter unit to the output filter unit to supply power to the power amplifier according to the control signal; The output filter unit is used to filter the power supply signal output by the input filter unit and passed through the protection unit to further eliminate high-frequency noise and low-frequency ripple.

2. The power amplifier protection circuit of claim 1, wherein, The detection unit includes resistors R1, R2, R3, R4, and a triode D1. The protection unit includes a field effect tube U1, which is VBZA4425; One end of the resistors R1 and R2 is connected to the output end of the input filter unit, the other end of the resistor R1 is connected to one end of the resistor R4, the other end of the resistor R4 is connected to a reference voltage and the b electrode of the triode D1, the other end of the resistor R2 is connected to the c electrode of the triode D1 and one end of the resistor R3, the e electrode of the triode D1 is connected to GND. The other end of the resistor R3 is connected to the 4 pin of the field effect tube U1, the 1 pin, 2 pin and 3 pin of the field effect tube U1 are connected together and connected to the output end of the input filter unit, the 5 pin, 6 pin, 7 pin and 8 pin of the field effect tube U1 are connected together and connected to the input end of the output filter unit.

3. The power amplifier protection circuit of claim 2, wherein, The b electrode of the triode D1 is also connected to GND through the resistor R5.

4. The power amplifier protection circuit of claim 2, wherein, The 5 pin of the field effect tube U1 is also connected to GND through the resistor R6.

5. The power amplifier protection circuit of claim 1, wherein, The input filter unit includes capacitors C1 and C2, and an inductor L1, one end of the capacitor C1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to one end of the capacitor C2, the other end of the capacitor C1 and the other end of the capacitor C2 are respectively connected to GND, one end of the inductor L1 is used to connect the input power supply, and the other end of the inductor L1 is used as the output end of the input filter unit and is connected to the detection unit and the protection unit.

6. The power amplifier protection circuit of claim 5, wherein, The capacitors C1 and C2 are used to reduce low-frequency noise and ripple amplitude, and the inductor L1 is used to hinder high-frequency noise to eliminate high-frequency noise.

7. The power amplifier protection circuit of claim 1, wherein, The output filter unit includes capacitors C3 and C4, and an inductor L2, one end of the capacitor C3 is connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the capacitor C4, the other end of the capacitor C3 and the other end of the capacitor C4 are respectively connected to GND, one end of the inductor L2 is used as the input of the output filter unit and is connected to the protection unit, and the other end of the inductor L2 is used as the output end of the output filter unit.

8. The power amplifier protection circuit of claim 7, wherein, The capacitor C3 is used to further eliminate low-frequency ripple, the capacitor C4 is used to further eliminate high-frequency noise, and the inductor L2 is used to suppress high-frequency interference.

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