A linear power amplifier static operating point adjustment and self-recovery protection circuit

Abstract

The present invention proposes a linear power amplifier static operating point conditioning and self-recovery protection circuit, which belongs to the technical field of amplifiers and amplification control. The circuit includes a static operating point feedback conditioning circuit and an output overcurrent protection circuit. The static operating point feedback conditioning circuit includes an operational amplifier U11, a capacitor C11, a resistor R11, a resistor R13, and a resistor R19. The output overcurrent protection circuit includes an operational amplifier U11, a transistor T12, a transistor T13, a resistor R17, and a resistor R18. The two parts share the same operational amplifier. The circuit is simple and efficient, ensuring a stable static operating point of the linear power tube and output overcurrent protection and protection self-recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of amplifiers and amplification control, and in particular to a linear power amplifier static operating point adjustment and self-recovery protection circuit. Background Art

[0002] The power amplifier uses a linear high-frequency amplifier. A stable quiescent operating point is a prerequisite for the proper functioning of a linear amplifier. This quiescent operating point must be set so that the linear power tube maintains a constant quiescent current, maintaining constant amplification. A low quiescent operating point current can cause cutoff distortion for low-amplitude signals. A high quiescent operating point results in high quiescent current, increasing losses and causing saturation distortion for high-amplitude signals.

[0003] Furthermore, all losses in linear power amplifiers are converted into heat generated by the linear power transistors in the power output stage. When the load impedance is low or a short circuit occurs, the circuit's output current is excessive, easily damaging the linear power transistors. To protect the power output stage, existing linear power amplifiers incorporate output current protection circuitry. When the output current exceeds a preset current limit, the power transistors are permanently shut down or the output current is limited to a preset value, thereby protecting them.

[0004] The existing static operating point conditioning circuit is open-loop control, the static operating point is unstable, the error is large, and the overcurrent protection circuit cannot self-recover. Summary of the Invention

[0005] The present invention aims to provide a linear power amplifier static operating point conditioning and self-recovery protection circuit, which can not only automatically adjust the static operating point, but also perform self-recovery protection when the output current is too large.

[0006] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0007] A linear power amplifier static operating point conditioning and self-recovery protection circuit, including a static operating point feedback conditioning circuit and an output overcurrent protection circuit;

[0008] The static operating point feedback conditioning circuit includes an operational amplifier U11, a capacitor C11, a resistor R11, a resistor R13, and a resistor R19. The inverting input terminal of the operational amplifier U11 is respectively connected to one end of the resistor R11 and the capacitor C11. The voltage at the other end of R11 is -VBB, where VBB is the static operating point voltage. The other end of C11 is connected to the output terminal of U11. The non-inverting input terminal of U11 is connected to GND_OUT. The output terminal of U11 is connected to the gate of the linear power tube T11. The drain of the linear power tube T11 is connected to +VCC, and the source is respectively connected to one end of the resistor R19 and the resistor R13. The other end of R19 is connected to GND_OUT, and the other end of R13 is connected to the inverting input terminal of U11. GND_OUT is the connection point between the circuit reference ground and the positive electrode of the output Vo, where Vo is the output voltage of the linear power amplifier.

[0009] Furthermore, the output overcurrent protection circuit includes a transistor T12, a transistor T13, a resistor R17, and a resistor R18. The collector of the transistor T13 is connected to the inverting input terminal of U11, the emitter of T13 is connected to the output terminal of U11, the base of T13 is connected to the collector of the transistor T12, the emitter of T12 is connected to GND_OUT, the base of T12 is connected to one end of the resistor R17 and the resistor R18 respectively, the other end of R17 is connected to the source of the linear power tube T11, and the other end of R18 is connected to GND_OUT.

[0010] Furthermore, it also includes a diode D11, a voltage-stabilizing diode D12, a 0-ohm resistor R12, a resistor R14, a resistor R15, a resistor R16, and a capacitor C12. The positive electrode of the diode D11 is connected to GND_OUT, the negative electrode of D11 is connected to the non-inverting input terminal of U11, the resistor R12 is connected between the non-inverting input terminal of U11 and GND_OUT, the positive electrode of the voltage-stabilizing diode D12 is connected to the inverting input terminal of U11, the negative electrode of D12 is connected to the output terminal of U11, one end of the resistor R14 is connected to the base of T13, and the other end is connected to the output terminal of U11, R15 is connected between the output terminal of U11 and the gate of T11, R16 is connected between the gate of T11 and the source of T11, and C12 is connected between the base of T12 and GND_OUT.

[0011] Furthermore, T12 is an NPN transistor, and T13 is a PNP transistor.

[0012] Furthermore, in steady state, IBO=VBB / R11, IFO=Vsat / R13, taking R11=R13, then IFO=IBO, Vsat=VBB, Isat=Vsat / R19, Vsat=VBB, and Isat = VBB / R19;

[0013] Among them, VBB is the static operating point voltage of the linear power tube T11, IBO is the static operating current of the conditioning circuit, IFO is the static operating feedback current of the conditioning circuit, Vsat is the static operating feedback voltage, and Isat is the static operating current of the linear power tube T11.

[0014] At startup, Isat = 0, Vsat = 0, IFO = 0, -VBB is a negative voltage, the current of C11 flows from the output terminal of the operational amplifier U11 to the inverting input terminal, C11 is charged to the conduction threshold of T11, T11 begins to conduct, and the circuit starts;

[0015] Among them, IFO is the static working feedback current of the conditioning circuit, Vsat is the static working feedback voltage, and Isat is the static working current of the linear power tube T11.

[0016] The dynamic adjustment process is:

[0017] In steady state, IFO=IBO, and the charge and discharge current on C11 is dynamically zero;

[0018] When Isat is too small, IFO is too small, C11 is charged, the output voltage of U11 increases, the linear conduction degree of T11 increases, and Isat increases;

[0019] When Isat is too large, IFO is too large, C11 discharges, the output voltage of U11 decreases, the linear conduction degree of T11 becomes smaller, and Isat decreases.

[0020] The output overcurrent protection process is:

[0021] Define the output current as io, V T12 is the conduction threshold of transistor T12, , T12 is turned on, the base voltage of T13 becomes zero, T13 is turned on, C11 discharges from the emitter to the collector through T13, the voltage of C11 drops to zero, the output voltage of U11 drops to zero, the driving voltage Vgs of T11 is reduced to zero, T11 is turned off, Isat+io=0, T12 is turned off, T13 is turned off, the circuit returns to the startup state and begins to self-recover.

[0022] Furthermore, the linear power tube T11 is an N-type IGBT or a P-type IGBT of a MOS tube, an IGBT, or a MOS tube composite circuit or structure.

[0023] The advantages of the present invention are: providing a linear power amplifier static operating point conditioning circuit and a self-recovery protection circuit, the two parts share the same operational amplifier circuit, which is simple and efficient, ensuring the stable static operating point of the linear power tube and output overcurrent protection and protection self-recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a circuit diagram of the linear power amplifier static operating point adjustment and self-recovery protection circuit of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0026] Example 1

[0027] This embodiment discloses a linear power amplifier static operating point conditioning and self-recovery protection circuit, including a static operating point feedback conditioning circuit and an output overcurrent protection circuit. For specific circuits, please refer to Figure 1 .

[0028] The static operating point feedback conditioning circuit includes an operational amplifier U11, a capacitor C11, a resistor R11, a resistor R13, and a resistor R19. The inverting input of the operational amplifier U11 is connected to one end of the resistor R11 and the capacitor C11 respectively. The voltage at the other end of R11 is -VBB, where VBB is the static operating point voltage. The other end of C11 is connected to the output of U11. The non-inverting input of U11 is connected to GND_OUT. The output of U11 is connected to the gate of the linear power tube T11. The drain of the linear power tube T11 is connected to +VCC, and the source is connected to one end of the resistor R19 and the resistor R13 respectively. The other end of R19 is connected to GND_OUT, and the other end of R13 is connected to the inverting input of U11. GND_OUT is the connection point between the circuit reference ground and the positive electrode of the output Vo, where Vo is the output voltage of the linear power amplifier.

[0029] The output overcurrent protection circuit includes a transistor T12, a transistor T13, a resistor R17, and a resistor R18. The collector of the transistor T13 is connected to the inverting input terminal of U11, the emitter of T13 is connected to the output terminal of U11, the base of T13 is connected to the collector of the transistor T12, the emitter of T12 is connected to GND_OUT, the base of T12 is connected to one end of the resistor R17 and the resistor R18 respectively, the other end of R17 is connected to the source of the linear power tube T11, and the other end of R18 is connected to GND_OUT.

[0030] The anode of diode D11 is connected to GND_OUT, the cathode of D11 is connected to the non-inverting input of U11, the resistor R12 is connected between the non-inverting input of U11 and GND_OUT, the anode of Zener diode D12 is connected to the inverting input of U11, the cathode of D12 is connected to the output of U11, one end of resistor R14 is connected to the base of T13, and the other end is connected to the output of U11, R15 is connected between the output of U11 and the gate of T11, R16 is connected between the gate of T11 and the source of T11, and C12 is connected between the base of T12 and GND_OUT.

[0031] Linear power transistor T11 is an N-type or P-type IGBT, a MOS transistor, IGBT, or a MOS transistor composite circuit or structure. T12 is an NPN transistor, T13 is a PNP transistor, R12 is a 0-ohm resistor, D12 is a Zener diode, VCC is the linear power transistor bus voltage, Vo is the linear power amplifier output voltage, and RL is the load resistor. GND_OUT is the connection point between the circuit reference ground and the positive terminal of the output Vo, and COM is the reference ground for +VCC and Vo.

[0032] Example 2

[0033] U11, C11, R11, R13 and R19 constitute the static operating point negative feedback conditioning circuit.

[0034] In steady state, IBO = VBB / R11, IFO = Vsat / R13, R11 = R13, IFO = IBO, Vsat = VBB, and Isat = Vsat / R19. Vsat = VBB. Ultimately, adjusting the value of R19 can adjust the quiescent operating current Isat of linear power transistor T11: Isat = VBB / R19. VBB is the quiescent operating point voltage of linear power transistor T11, IBO is the quiescent operating current of the conditioning circuit, IFO is the quiescent operating feedback current of the conditioning circuit, Vsat is the quiescent operating feedback voltage, and Isat is the quiescent operating current of linear power transistor T11.

[0035] At startup: Isat = 0, Vsat = 0, IFO = 0, -VBB is a negative voltage, the current of C11 flows from the output end of the op amp U11 to the inverting input end, C11 is charged to the conduction threshold of T11, T11 starts to turn on, and the circuit starts.

[0036] The dynamic adjustment process is:

[0037] In steady state, IFO = IBO, and the charge and discharge currents on C11 are dynamically zero. When Isat is low, Vsat = / Isat R19, Vsat is too low, and IFO = Vsat / R13. With low IFO, the current through C11 flows from the output of op amp U11 to the non-inverting input, charging C11, increasing the op amp output voltage, increasing the linear conduction of T11, and increasing Isat. When Isat is high, Vsat = / Isat R19, Vsat is too high, IFO = Vsat / R13, and IFO is too low. The current through C11 flows from the non-inverting input of op amp U11 to the output, discharging C11, decreasing the op amp output voltage, decreasing the linear conduction of T11, and decreasing Isat. Ultimately, the system returns to steady state, with Isat = VBB / R19.

[0038] Example 3

[0039] U11, T12, and T13 form a self-recovery protection circuit. The output overcurrent protection process is as follows:

[0040] Define the output current as io, V T12 is the conduction threshold of transistor T12, When , T12 is turned on, the base voltage of T13 becomes zero, T13 is turned on, C11 discharges from the emitter to the collector through T13, the voltage of C11 drops to zero, the output voltage of U11 drops to zero, the driving voltage Vgs of T11 decreases to zero, T11 is turned off, and after T11 is turned off, Isat+io=0, T12 is turned off, T13 is turned off, the circuit returns to the startup state, and starts self-recovery, and T11 recovers from the overcurrent state to the normal working state.

[0041] The above circuit only takes the N-type linear working tube as an example, and the principle is also applicable to the P-type linear power tube.

[0042] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A linear power amplifier static operating point conditioning and self-recovery protection circuit, characterized in that: Including static operating point feedback conditioning circuit and output overcurrent protection circuit; The static operating point feedback conditioning circuit includes an operational amplifier U11, a capacitor C11, a resistor R11, a resistor R13, and a resistor R19. The inverting input terminal of the operational amplifier U11 is connected to one end of the resistor R11 and the capacitor C11 respectively. The voltage of the other end of R11 is -VBB, where VBB is the static operating point voltage. The other end of C11 is connected to the output terminal of U11. The non-inverting input terminal of U11 is connected to GND_OUT. The output terminal of U11 is connected to the gate of the linear power tube T11. The drain of the linear power tube T11 is connected to +VCC. The source is connected to one end of the resistor R19 and the resistor R13 respectively. The other end of R19 is connected to GND_OUT. The other end of R13 is connected to the inverting input terminal of U11. GND_OUT is the connection point between the circuit reference ground and the positive electrode of the output Vo. Vo is the output voltage of the linear power amplifier. In steady state, IBO=VBB / R11, IFO=Vsat / R13, take R11=R13, then IFO=IBO, Vsat=VBB, Isat=Vsat / R19, Vsat=VBB, and Isat = VBB / R19; Wherein, VBB is the static operating point voltage of the linear power tube T11, IBO is the static operating current of the conditioning circuit, IFO is the static operating feedback current of the conditioning circuit, Vsat is the static operating feedback voltage, and Isat is the static operating current of the linear power tube T11; The dynamic adjustment process is: In steady state, IFO=IBO, and the charge and discharge current on C11 is dynamically zero; When Isat is too small, IFO is too small, C11 is charged, the output voltage of U11 increases, the linear conduction degree of T11 increases, and Isat increases; When Isat is too large, IFO is too large, C11 discharges, the output voltage of U11 decreases, the linear conduction degree of T11 decreases, and Isat decreases.

2. The linear power amplifier static operating point conditioning and self-recovery protection circuit according to claim 1, characterized in that: The output overcurrent protection circuit includes a transistor T12, a transistor T13, a resistor R17, and a resistor R18. The collector of the transistor T13 is connected to the inverting input terminal of U11, the emitter of T13 is connected to the output terminal of U11, the base of T13 is connected to the collector of the transistor T12, the emitter of T12 is connected to GND_OUT, the base of T12 is connected to one end of the resistor R17 and the resistor R18 respectively, the other end of R17 is connected to the source of the linear power tube T11, and the other end of R18 is connected to GND_OUT.

3. The linear power amplifier static operating point conditioning and self-recovery protection circuit according to claim 1 or 2, characterized in that: It also includes a diode D11, a voltage-stabilizing diode D12, a 0-ohm resistor R12, a resistor R14, a resistor R15, a resistor R16, and a capacitor C12. The positive electrode of the diode D11 is connected to GND_OUT, the negative electrode of D11 is connected to the non-inverting input terminal of U11, the resistor R12 is connected between the non-inverting input terminal of U11 and GND_OUT, the positive electrode of the voltage-stabilizing diode D12 is connected to the inverting input terminal of U11, the negative electrode of D12 is connected to the output terminal of U11, one end of the resistor R14 is connected to the base of T13, and the other end is connected to the output terminal of U11, R15 is connected between the output terminal of U11 and the gate of T11, R16 is connected between the gate of T11 and the source of T11, and C12 is connected between the base of T12 and GND_OUT.

4. The linear power amplifier static operating point conditioning and self-recovery protection circuit according to claim 2, characterized in that: The T12 is an NPN transistor, and T13 is a PNP transistor.

5. The linear power amplifier static operating point conditioning and self-recovery protection circuit according to claim 1, characterized in that: At startup, Isat = 0, Vsat = 0, IFO = 0, -VBB is a negative voltage, the current of C11 flows from the output terminal of the operational amplifier U11 to the inverting input terminal, C11 is charged to the conduction threshold of T11, T11 begins to conduct, and the circuit starts; Among them, IFO is the static working feedback current of the conditioning circuit, Vsat is the static working feedback voltage, and Isat is the static working current of the linear power tube T11.

6. The linear power amplifier static operating point adjustment and self-recovery protection circuit according to claim 2, characterized in that: The output overcurrent protection process is: Define the output current as io, V T12 is the conduction threshold of transistor T12, , T12 is turned on, the base voltage of T13 becomes zero, T13 is turned on, C11 discharges from the emitter to the collector through T13, the voltage of C11 drops to zero, the output voltage of U11 drops to zero, the driving voltage Vgs of T11 is reduced to zero, T11 is turned off, Isat+io=0, T12 is turned off, T13 is turned off, the circuit returns to the startup state and begins to self-recover.

7. The linear power amplifier static operating point conditioning and self-recovery protection circuit according to claim 1 or 2, characterized in that: The linear power tube T11 is a MOS tube, an IGBT or a composite circuit of a MOS tube structure.

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