Power amplifier sensitivity switching circuit

Abstract

The utility model provides a power amplifier sensitivity switching circuit which comprises a signal amplification circuit and a sensitivity switching circuit, the signal amplification circuit is used for amplifying input signal level amplitude, and the sensitivity switching circuit is used for switching sensitivity input; the signal amplification circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C5, an operational amplifier U1A and an operational amplifier U1B, one end of the resistor R1, one end of the resistor R2 and one end of the capacitor C2 are connected with a pin 2 of the reverse input end of the operational amplifier U1A, the other end of the resistor R2, the other end of the capacitor C2 and one end of the resistor R4 are connected with a pin 1 of the output end of the operational amplifier U1A, and the other end of the resistor R3 is connected with a pin 2 of the reverse input end of the operational amplifier U1A. According to the utility model, the switching is controlled by an external control signal, and compared with a traditional dial switch switching device, the switching device has the advantages of remote operation, convenient operation, and no switching failure caused by oxidation of the switching device.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, and in particular to a power amplifier sensitivity switching circuit. Background Art

[0002] In RF power amplifiers (PAs), especially saturated PAs, a power control circuit is needed to control the output power of the PA. There are generally two ways of power control: collector power control ( Figure 1 ) and base power control ( Figure 2 ).

[0003] A schematic diagram of collector power control is shown in Figure 1 As shown, the amplifier tube Q is a power transistor, which can be BJT, GaAs, LDMOS, etc. The RF input signal is connected to the base of the amplifier tube Q through the DC blocking capacitor Cl, and the base of the amplifier tube Q is also connected to a fixed bias voltage vb provided by the base bias circuit. The emitter of the amplifier tube Q is connected to the ground through the impedance Zc, and the collector of Q is connected to the output Vcc of the LDO (linear regulator) through the impedance Zc. The collector of the amplifier tube Q is also connected to the DC blocking capacitor C2. The LDO controls the output voltage Vcc according to the power control voltage Vramp, thereby controlling the saturated output power of the power amplifier.

[0004] The advantage of collector power control is good power control accuracy, because the output voltage Vcc of the LDO can be accurately controlled by its input control voltage Vramp. The disadvantage of collector power control is that the power added efficiency is relatively low, because there is a certain voltage difference between the input and output of the LDO. When the output power is large, the LDO flows a large current and its own power consumption is relatively large.

[0005] In view of the diversification of audio broadcast power amplifiers in use, it is necessary to match the corresponding speaker power to avoid the high-power amplifier burning out the low-power speaker. The specially designed sensitivity switching circuit controls the output power by controlling the input sensitivity.

[0006] Therefore, it is necessary to provide a power amplifier sensitivity switching circuit to solve the above technical problems. Utility Model Content

[0007] In order to solve the above technical problems, the utility model provides a power amplifier sensitivity switching circuit. The present invention controls the switching by an external control signal. Compared with the traditional dip switch switching device, it has the advantages of remote operation, convenient operation, and will not be unable to switch due to problems such as oxidation of the switch device.

[0008] The utility model provides a power amplifier sensitivity switching circuit, comprising a signal amplifying circuit and a sensitivity switching circuit, wherein the signal amplifying circuit is used to amplify the input signal level amplitude, and the sensitivity switching circuit is used to switch the size of the sensitivity input;

[0009] The signal amplification circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C5, an operational amplifier U1A and an operational amplifier U1B, one end of the resistor R1, one end of the resistor R2 and one end of the capacitor C2 are connected to the reverse input terminal 2 pin of the operational amplifier U1A, the other end of the resistor R2, the other end of the capacitor C2 and one end of the resistor R4 are connected to the output terminal 1 pin of the operational amplifier U1A, the other end of the resistor R1 is connected to one end of the capacitor C1, the positive input terminal of the operational amplifier U1A is grounded, and the other end of the capacitor C1 is connected to an external input sound source;

[0010] The sensitivity switching circuit includes resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, transistor Q2, transistor Q3, and field effect transistor Q1. One end of the resistor R7 and the other end of the resistor R4 are connected to the other end of the resistor R3, the other end of the resistor R7 is connected to pin 2 of the field effect transistor Q1, pin 1 of the field effect transistor Q1 is grounded, pin 3 of the field effect transistor Q1 is connected to one end of the resistor R9, the other end of the resistor R9 and one end of the resistor R12 are connected to pin 3 of the transistor Q2, and pin 1 of the transistor Q2 and one end of the resistor R8 are connected to one end of the resistor R10.

[0011] Furthermore, pin 2 of the transistor Q2 and the other end of the resistor R8 are connected to an external voltage of +12V, and the other end of the resistor R12 is connected to an external voltage of -12V.

[0012] Furthermore, the other end of the resistor R10 is connected to pin 3 of the transistor Q3, pin 1 of the transistor Q3 is connected to one end of the resistor R11, pin 2 of the transistor Q3 is grounded, and the other end of the resistor R11 is connected to an external control point.

[0013] Furthermore, one end of the resistor R3, one end of the resistor R5, and one end of the capacitor C5 are connected to the direction input terminal 6 of the operational amplifier U1B.

[0014] Furthermore, the other end of the resistor R5, one end of the resistor R6, and the other end of the capacitor C5 are connected to the output terminal 7 pin of the operational amplifier U1B, the positive input terminal 5 pin of the operational amplifier U1B is grounded, and the other end of the resistor R6 is connected to the external output sound source.

[0015] Compared with the related art, the power amplifier sensitivity switching circuit provided by the utility model has the following advantages:

[0016] Beneficial effects:

[0017] The utility model controls the switching by an external control signal, and compared with the traditional dial switch switching device, it has the advantages of remote operation, convenient operation, and no problem of switching failure due to oxidation of the switch device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a common RF power amplifier using collector power control;

[0019] Figure 2 It is a common RF power amplifier using base power control;

[0020] Figure 3 The utility model provides a circuit diagram of a power amplifier sensitivity switching circuit. DETAILED DESCRIPTION

[0021] The utility model is further described below in conjunction with the accompanying drawings and implementation modes.

[0022] In this application, reference is made to Figure 1-3As shown, a power amplifier sensitivity switching circuit includes a signal amplification circuit and a sensitivity switching circuit, the signal amplification circuit is used to amplify the input signal level amplitude, and the sensitivity switching circuit is used to switch the size of the sensitivity input; the signal amplification circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C5, an operational amplifier U1A and an operational amplifier U1B, one end of the resistor R1, one end of the resistor R2, and one end of the capacitor C2 are connected to the reverse input terminal 2 of the operational amplifier U1A The other end of the resistor R2, the other end of the capacitor C2, and one end of the resistor R4 are connected to the output terminal 1 of the operational amplifier U1A, the other end of the resistor R1 is connected to one end of the capacitor C1, the positive input terminal of the operational amplifier U1A is grounded, and the other end of the capacitor C1 is connected to the external input sound source; the sensitivity switching circuit includes resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, transistor Q2, transistor Q3, and field effect transistor Q1, one end of the resistor R7, the other end of the resistor R4 and the other end of the resistor R3 The other end of the resistor R7 is connected to the 2nd pin of the field effect tube Q1, the 1st pin of the field effect tube Q1 is grounded, the 3rd pin of the field effect tube Q1 is connected to one end of the resistor R9, the other end of the resistor R9 and one end of the resistor R12 are connected to the 3rd pin of the transistor Q2, the 1st pin of the transistor Q2 and one end of the resistor R8 are connected to one end of the resistor R10, the 2nd pin of the transistor Q2 and the other end of the resistor R8 are connected to the external voltage +12V, the other end of the resistor R12 is connected to the external voltage -12V, and the other end of the resistor R10 is connected to the external voltage +12V. Connected to pin 3 of transistor Q3, pin 1 of transistor Q3 is connected to one end of resistor R11, pin 2 of transistor Q3 is grounded, the other end of resistor R11 is connected to an external control point, one end of resistor R3, one end of resistor R5, and one end of capacitor C5 are connected to pin 6 of the direction input terminal of op amp U1B, the other end of resistor R5, one end of resistor R6, and the other end of capacitor C5 are connected to pin 7 of the output terminal of op amp U1B, pin 5 of the forward input terminal of op amp U1B is grounded, and the other end of resistor R6 is connected to the external output sound source.

[0023] As an embodiment of the utility model: when the external control signal KEY is at a low level, the input sound source is amplified by the operational amplifier U1A and the operational amplifier U1B, and then output to the power amplifier; when the external control signal KEY is at a high level, the transistor Q3, the transistor Q2 and the field effect transistor Q1 are turned on, and the field effect transistor Q1 is connected to the ground. When the input sound source is amplified by the operational amplifier U1A and reaches the connection between the resistor R4 and the resistor R7, voltage division is achieved, and the input sensitivity level signal is reduced, so that the operational amplifier U1B amplifies the signal and then outputs it to the power amplifier;

[0024] When Q1 is turned on and R7 divides the voltage, the input sensitivity voltage entering the power amplifier is reduced, and the output power of the power amplifier is reduced to protect the speaker. The KEY signal can be a signal controlled by the I / O port of the microcontroller. When the I / O port 1 of the microcontroller U1 outputs a high level, the sensitivity switching circuit works. Two transistors Q2, Q3 and one field effect transistor Q1 act as switches here. When KEY is a high-level signal, transistor Q3 is turned on. At this time, the base voltage of pin 1 of transistor Q2 changes, which is lower than the emitter voltage of pin 2 +12V. Then transistor Q2 is turned on. After turning on, the collector voltage of pin 3 is the power supply voltage. At this time, the field effect transistor Q1 is turned on, which is equivalent to one end of resistor R7 being grounded, so resistors R7 and R4 form a voltage divider circuit. (For example: according to the circuit parameters, when the voltage of the input sensitivity passing through resistor R4 is 1V, after Q1 is turned on, the voltage of the input sensitivity passing through resistor R4 is 0.5V.)

[0025] In a power amplifier, the amplification factor of the power amplifier part is fixed. To change its output power, it is necessary to change the input sensitivity. For example, the rated output power of the power amplifier is 500W, and the rated power of the speaker is 200W. By switching the input sensitivity through the sensitivity switching circuit, the rated output power of the power amplifier becomes 200W, thus preventing the speaker from being burned.

[0026] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" etc. indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0027] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A power amplifier sensitivity switching circuit, comprising a signal amplification circuit and a sensitivity switching circuit, characterized in that: The signal amplification circuit is used to amplify the input signal level amplitude, and the sensitivity switching circuit is used to switch the sensitivity input size; The signal amplification circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C1, a capacitor C2, a capacitor C5, an operational amplifier U1A and an operational amplifier U1B, one end of the resistor R1, one end of the resistor R2 and one end of the capacitor C2 are connected to the reverse input terminal 2 pin of the operational amplifier U1A, the other end of the resistor R2, the other end of the capacitor C2 and one end of the resistor R4 are connected to the output terminal 1 pin of the operational amplifier U1A, the other end of the resistor R1 is connected to one end of the capacitor C1, the positive input terminal of the operational amplifier U1A is grounded, and the other end of the capacitor C1 is connected to an external input sound source; The sensitivity switching circuit includes resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, transistor Q2, transistor Q3, and field effect transistor Q1. One end of the resistor R7 and the other end of the resistor R4 are connected to the other end of the resistor R3, the other end of the resistor R7 is connected to pin 2 of the field effect transistor Q1, pin 1 of the field effect transistor Q1 is grounded, pin 3 of the field effect transistor Q1 is connected to one end of the resistor R9, the other end of the resistor R9 and one end of the resistor R12 are connected to pin 3 of the transistor Q2, and pin 1 of the transistor Q2 and one end of the resistor R8 are connected to one end of the resistor R10.

2. A power amplifier sensitivity switching circuit according to claim 1, characterized in that: Pin 2 of the transistor Q2 and the other end of the resistor R8 are connected to an external voltage of +12V, and the other end of the resistor R12 is connected to an external voltage of -12V.

3. The power amplifier sensitivity switching circuit according to claim 1, characterized in that: The other end of the resistor R10 is connected to the pin 3 of the transistor Q3, the pin 1 of the transistor Q3 is connected to one end of the resistor R11, the pin 2 of the transistor Q3 is grounded, and the other end of the resistor R11 is connected to an external control point.

4. The power amplifier sensitivity switching circuit according to claim 1, characterized in that: One end of the resistor R3, one end of the resistor R5, and one end of the capacitor C5 are connected to the direction input terminal 6 of the operational amplifier U1B.

5. The power amplifier sensitivity switching circuit according to claim 1, characterized in that: The other end of the resistor R5, one end of the resistor R6, and the other end of the capacitor C5 are connected to the output terminal 7 pin of the operational amplifier U1B, the positive input terminal 5 pin of the operational amplifier U1B is grounded, and the other end of the resistor R6 is connected to the external output sound source.

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