A power amplifier based on adaptive overcurrent protection

Abstract

The present application discloses a power amplifier based on adaptive overcurrent protection, the power amplifier at least includes: a first amplifier circuit, an overcurrent protection circuit and a control circuit, the first amplifier circuit is used to amplify the input signal to generate a first output signal; the overcurrent protection circuit is coupled to the output end of the first amplifier circuit, and is used to generate an overcurrent signal when it is determined that the output current of the first amplifier circuit is greater than the overcurrent protection threshold, wherein the overcurrent protection threshold changes with the first output signal; the control circuit is coupled to the overcurrent protection circuit and the first amplifier circuit respectively, and is used to control the first amplifier circuit to disconnect according to the overcurrent signal. In the above manner, the present application can adaptively adjust the overcurrent protection threshold to prevent the power amplifier from being burned due to overcurrent.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to a power amplifier based on adaptive overcurrent protection. Background Art

[0002] Class AB power amplifier chips often encounter abnormal situations during operation, such as output short circuit, which can easily cause the power tube to burn out due to overcurrent, so an overcurrent protection circuit needs to be set. Common overcurrent protection usually adopts a fixed overcurrent threshold, but its overcurrent threshold is difficult to set, especially when the power supply voltage changes or the chip output voltage changes. If the overcurrent threshold is set too small, it will affect the normal output function of the Class AB power amplifier chip. If the overcurrent threshold is set too large, the power of the chip's output power tube will change greatly. When the power tube is at high power, it is easy to burn the chip.

[0003] One of the overcurrent protection measures used in the prior art is to use a fixed overcurrent protection threshold. This method is relatively simple. When the power supply voltage and the chip output voltage change, the overcurrent protection threshold of the chip remains unchanged, and a fixed overcurrent protection threshold is always used. However, when the power supply voltage and the chip output voltage change in a large range, the voltage applied to both ends of the power tube of the Class AB power amplifier chip also changes greatly. When the Class AB power amplifier chip works normally, the power change range of both ends of its power tube is very large; the other is that the overcurrent protection threshold changes adaptively with the power supply voltage, which is to multiply the power supply voltage variable by a certain coefficient and introduce it into the overcurrent protection circuit, so that the overcurrent protection threshold is different at different power supply voltages. However, when the Class AB power amplifier chip works at a certain power supply voltage, its overcurrent protection threshold is fixed. For the Class AB power amplifier chip, when there is a large input signal, its output voltage changes synchronously with the input signal. Especially at a high power supply voltage, the chip output voltage changes greatly, and the voltage at both ends of the power tube also changes greatly. If the overcurrent protection threshold does not change adaptively with the voltage at both ends of the power tube, it is easy to affect the normal function of the chip or burn the chip. Summary of the invention

[0004] The main problem to be solved by the present application is to provide a power amplifier based on adaptive overcurrent protection, which can adaptively adjust the overcurrent protection threshold to prevent the power amplifier from being burned due to overcurrent.

[0005] In order to solve the above technical problems, the technical solution adopted in the present application is: to provide a power amplifier based on adaptive overcurrent protection, the power amplifier at least includes: a first amplifier circuit, an overcurrent protection circuit and a control circuit, the first amplifier circuit is used to amplify the input signal and generate a first output signal; the overcurrent protection circuit is coupled to the output end of the first amplifier circuit, and is used to generate an overcurrent signal when it is judged that the output current of the first amplifier circuit is greater than the overcurrent protection threshold, wherein the overcurrent protection threshold changes with the first output signal; the control circuit is coupled to the overcurrent protection circuit and the first amplifier circuit respectively, and is used to control the first amplifier circuit to disconnect according to the overcurrent signal.

[0006] Through the above scheme, the beneficial effect of the present application is: the first amplifier circuit is protected by an overcurrent protection circuit, and the overcurrent protection threshold can be automatically adjusted following the signal output by the power amplifier. When the output current of the first amplifier circuit exceeds the overcurrent protection threshold, the overcurrent protection circuit is turned on, an overcurrent signal is generated, and the overcurrent signal is sent to the control circuit, so that the control circuit controls the first amplifier circuit to disconnect, prevents the input signal from entering the first amplifier circuit, and avoids burning the first amplifier circuit due to overcurrent. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0008] Figure 1 It is a schematic diagram of the structure of the output stage of a power amplifier in the prior art;

[0009] Figure 2 It is a structural schematic diagram of an embodiment of a power amplifier based on adaptive overcurrent protection provided by the present application;

[0010] Figure 3 is a structural schematic diagram of another embodiment of a power amplifier based on adaptive overcurrent protection provided by the present application;

[0011] Figure 4 yes Figure 3 Another schematic diagram of the structure of the power amplifier in the embodiment shown;

[0012] Figure 5 yes Figure 3 A schematic structural diagram of a first overcurrent detection circuit in the embodiment shown;

[0013] Figure 6 yes Figure 3 A schematic diagram of the structure of a second overcurrent detection circuit in the embodiment shown;

[0014] Figure 7 yes Figure 3 A schematic diagram of the structure of the current generating circuit in the embodiment shown;

[0015] Figure 8 yes Figure 3 A schematic diagram of a simulation curve of an overcurrent protection threshold corresponding to a PMOS power tube in the embodiment shown;

[0016] Fig. 9 yes Figure 3 A schematic diagram of a simulation curve of an overcurrent protection threshold corresponding to an NMOS power tube in the embodiment shown;

[0017] Fig.10 yes Figure 3 A schematic diagram of a simulation curve of an overcurrent protection threshold corresponding to a PMOS power tube under different power supply voltages in the embodiment shown;

[0018] Fig.11 yes Figure 3 The embodiment shown is a schematic diagram of a simulation curve of the over-current protection threshold corresponding to the NMOS power tube under different power supply voltages. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] The output stage of Class AB power amplifier chip is as follows Figure 1 As shown, it includes a PMOS (Positive channel Metal Oxide Semiconductor) power tube close to the power side and an NMOS (Negative channel Metal Oxide Semiconductor) power tube close to the ground side, the ground voltage is VSS, the connection end of the PMOS power tube and the NMOS power tube is the output end of the Class A and B power amplifier chip, Von_p is the minimum on-state voltage at both ends of the PMOS power tube, and Von_n is the minimum on-state voltage at both ends of the NMOS power tube.

[0021] The product of the voltage across the power tube and the current flowing through the power tube is the power applied to the power tube. Limited by the maximum power and heat dissipation capacity, the power tube must be able to work normally. The power applied to the power tube has a limit value, namely the safe working power. The current and voltage area corresponding to the safe working power is the safe working area. In the prior art, due to the large power variation across the power tube, the requirements for the safe working area of ​​the power tube are relatively high.

[0022] When the power supply voltage VDD is a fixed value, when the voltage Vout at the output end changes between VSS+Von_n and VDD-Von_p, if the overcurrent protection threshold does not change with the output voltage, when the overcurrent protection threshold is designed too small, it is easy to limit the output power when the voltage at both ends of the power tube is small, affecting the normal function of the chip; when the overcurrent protection threshold is designed too large, it is easy to cause the power at both ends of the PMOS power tube or the NMOS power tube to be too large when the voltage at both ends of the power tube is large, burning the chip; when the output voltage Vout is fixed to half of the power supply voltage VDD, when the power supply voltage VDD increases, the voltage applied to both ends of the PMOS power tube and the NMOS power tube increases. If the overcurrent protection adopts a fixed threshold and does not change with the power supply voltage VDD, when the overcurrent protection threshold is designed too small, it is easy to limit the output power when the power supply voltage VDD is low; when the overcurrent protection threshold is designed too large, it is easy to cause the power at both ends of the PMOS power tube or the NMOS power tube to be too large when the power supply voltage VDD is high, burning the chip.

[0023] See also Figure 2 , Figure 2 It is a structural schematic diagram of an embodiment of a power amplifier based on adaptive overcurrent protection provided in the present application. The power amplifier at least includes: a first amplifying circuit 10, an overcurrent protection circuit 20 and a control circuit 30.

[0024] The first amplifier circuit 10 is used to amplify an input signal to generate a first output signal. The input signal is a signal to be amplified, and the first output signal is a signal obtained by amplifying the signal to be amplified.

[0025] The overcurrent protection circuit 20 is coupled to the output end of the first amplifier circuit 10 and is used to generate an overcurrent signal when it is determined that the output current of the first amplifier circuit 10 is greater than an overcurrent protection threshold. The overcurrent protection threshold changes with the first output signal.

[0026] When the first output signal or input signal is relatively large, the output current of the first amplifier circuit 10 may be greater than the overcurrent protection threshold, thereby triggering the overcurrent protection circuit 20, causing the overcurrent protection circuit 20 to work, generate an overcurrent signal, and output the overcurrent signal to the control circuit, so that the first amplifier circuit 10 is normally shut down; when the first output signal or input signal is relatively small, the output current of the first amplifier circuit 10 is less than the overcurrent protection threshold, and the overcurrent protection circuit 20 cannot be triggered, the overcurrent protection circuit 20 cannot enter the working state, and the first amplifier circuit 10 works normally.

[0027] The control circuit 30 is coupled to the overcurrent protection circuit 20 and the first amplifier circuit 10 respectively, and is used to control the first amplifier circuit 10 to disconnect according to the overcurrent signal; when the overcurrent protection circuit 20 outputs the overcurrent signal to the control circuit 30, the control circuit 30 outputs the control signal to the first amplifier circuit 10, and controls the first amplifier circuit 10 to disconnect, so that the input signal can no longer be processed by the first amplifier circuit 10, thereby ensuring that when the current is too large, the first amplifier circuit 10 cannot work normally, avoiding damage to the first amplifier circuit 10 caused by overcurrent.

[0028] When the first output signal is short-circuited, the overcurrent protection circuit 20 sends an overcurrent signal to the control circuit 30 to shut down the power amplifier and enter a protection state; when the voltage of the first output signal returns to normal, the overcurrent signal disappears and the power amplifier returns to normal operation; the scheme in this embodiment can be applied to high-power chips operating in the saturation zone, including but not limited to Class A, Class B or Class AB audio power amplifier chips.

[0029] The present embodiment provides a power amplifier based on adaptive overcurrent protection. When the output current of the first amplifier circuit 10 exceeds the overcurrent protection threshold, the overcurrent protection circuit 20 is triggered, so that the overcurrent protection circuit 20 generates an overcurrent signal. The overcurrent signal is input to the control circuit 30. The control circuit 30 controls the first amplifier circuit 10 to disconnect according to the overcurrent signal, thereby preventing the input signal from entering the first amplifier circuit 10. The overcurrent protection threshold can change with the change of the first output signal. When the output power is large, the overcurrent protection threshold can be automatically adjusted in time to prevent the power amplifier from being burned due to overcurrent.

[0030] See also Figure 3 , Figure 3 It is a structural schematic diagram of another embodiment of a power amplifier based on adaptive overcurrent protection provided in the present application, and the power amplifier at least includes: a first amplifier circuit 10, an overcurrent protection circuit 20, a control circuit 30 and a second amplifier circuit 40.

[0031] The second amplifier circuit 40 is coupled to the output end of the control circuit 30, and is used to process the input signal, output the first amplified signal and the second amplified signal to the first amplifier circuit 10, and stop working when receiving the control signal output by the control circuit 30; the second amplifier circuit 40 can receive the input signal, amplify the received input signal, generate the first amplified signal and the second amplified signal, and send them to the first amplifier circuit 10.

[0032] The first amplifier circuit 10 includes: a first driving power amplifier circuit 11 and a second driving power amplifier circuit 12. The first driving power amplifier circuit 11 is coupled to the output end of the control circuit 30 and the output end of the second amplifier circuit 40 respectively, and is used to amplify the first amplified signal; the second driving power amplifier circuit 12 is coupled to the output end of the control circuit 30, the output end of the second amplifier circuit 40 and the output end of the first driving power amplifier circuit 11 respectively, and is used to amplify the second amplified signal. The first amplified signal and the second amplified signal have the same amplitude and opposite phase.

[0033] In a specific embodiment, Figure 4 As shown, the first driving power amplifier circuit 11 includes: a first driving circuit 111 and a first power tube T1, and the second driving power amplifier circuit 12 includes: a second driving circuit 121 and a second power tube T2.

[0034] The first driving circuit 111 is coupled to the output end of the second amplifying circuit 40 and the output end of the control circuit 30 respectively, and is used to output a first driving signal to the first power tube T1 to drive the first power tube T1; the first power tube T1 includes a first end, a second end and a third end, the first end of the first power tube T1 is coupled to the output end of the first driving circuit 111, the second end of the first power tube T1 is coupled to the power supply end (not marked in the figure), and the voltage amplitude of the power supply end is VDD; specifically, the first power tube T1 is a PMOS power tube, and the first end, the second end and the third end are a gate, a source and a drain respectively.

[0035] The second driving circuit 121 is coupled to the output end of the second amplifier circuit 40 and the output end of the control circuit 30 respectively, and is used to output a second driving signal to the second power tube T2 to drive the second power tube T2; the second power tube T2 includes a first end, a second end and a third end, the first end of the second power tube T2 is coupled to the output end of the second driving circuit 121, the second end of the second power tube T2 is coupled to the ground end (not marked in the figure), the third end of the second power tube T2 is coupled to the third end of the first power tube T1, and the voltage amplitude of the ground end is VSS; specifically, the second power tube T2 is an NMOS power tube, and the first end, the second end and the third end are respectively a gate, a source and a drain.

[0036] The amplitude of the first output signal is the output voltage Vout. When the output voltage Vout increases, the voltage across the PMOS power tube decreases, and the voltage across the NMOS power tube increases. While ensuring normal operation, the current allowed to pass through the PMOS power tube increases, and the current allowed to pass through the NMOS power tube decreases; when the output voltage Vout decreases, the voltage across the PMOS power tube increases, and the voltage across the NMOS power tube decreases. While ensuring normal operation, the current allowed to pass through the PMOS power tube decreases, and the current allowed to pass through the NMOS power tube increases.

[0037] The input signal is pre-amplified by the second amplifier circuit 40 to generate a first amplified signal and a second amplified signal, which are transmitted to the first drive circuit 111 and the second drive circuit 121 respectively, thereby driving the PMOS power tube and the NMOS power tube, so that the first output signal changes synchronously with the input signal; when the input signal is large, the output voltage Vout changes between (VSS+Von_n) and (VDD-Von_p); the overcurrent protection threshold changes with the first output signal and the power supply voltage VDD.

[0038] The overcurrent protection threshold includes a first overcurrent protection threshold and a second overcurrent protection threshold, the overcurrent signal includes a first overcurrent signal and a second overcurrent signal, and the overcurrent protection circuit 20 includes: a first overcurrent detection circuit 21 and a second overcurrent detection circuit 22 .

[0039] The input end of the first overcurrent detection circuit 21 is coupled to the third end of the first power tube T1, and is used to detect whether the output current of the first power tube T1 is greater than the first overcurrent protection threshold. If the output current of the first power tube T1 is greater than the first overcurrent protection threshold, a first overcurrent signal is generated; the input end of the second overcurrent detection circuit 22 is coupled to the third end of the second power tube T2, and is used to detect whether the input current of the second power tube T2 is greater than the second overcurrent protection threshold. If the input current of the second power tube T2 is greater than the second overcurrent protection threshold, a second overcurrent signal is generated.

[0040] In a specific embodiment, Figure 5As shown, the first overcurrent detection circuit 21 includes a first current comparator C1, the first input end of the first current comparator C1 is used to receive the first current signal Ip_p, and the second input end of the first current comparator C1 is used to receive the first reference current signal Iref_p; when the first current signal Ip_p is greater than the first reference current signal Iref_p, the first current comparator C1 outputs a first overcurrent signal, the first current signal Ip_p includes a first sampling current signal Isense_p and a first adjustable current signal Ic_p, the first sampling current signal Isense_p is obtained by sampling the output current of the first power tube T1, that is, the first sampling current signal Isense_p is proportional to the output current of the first power tube T1, the first adjustable current signal Ic_p is the adjustable current in the first overcurrent detection circuit 21, which is proportional to the power supply voltage VDD and inversely proportional to the output voltage Vout. The input signals of the first over-current detection circuit 21 are respectively the first adjustable current signal Ic_p, the first sampling current signal Isense_p and the first reference current signal Iref_p, and the output signal is the first over-current signal.

[0041] The first current signal Ip_p is formed by superimposing the first sampling current signal Isense_p and the first adjustable current signal Ic_p; when the power supply voltage VDD and the output voltage Vout are fixed, the first adjustable current signal Ic_p can be superimposed on the first sampling current signal Isense_p to obtain the first current signal Ip_p=Isense_p+Ic_p; the first current signal Ip_p and the first reference current signal Iref_p are input to the first current comparator C1 for comparison, and when Isense_p+Ic_p>Iref_p, the first current comparator C1 outputs a first overcurrent signal to shut down the power amplifier to prevent the power amplifier from burning out.

[0042] When the power supply voltage VDD changes, the overcurrent protection threshold value changes adaptively following the power supply voltage VDD. Specifically, the overcurrent protection threshold value corresponding to the first power tube T1 is inversely proportional to the power supply voltage VDD. If the power supply voltage VDD increases, the first adjustable current signal Ic_p increases, the first reference current signal Iref_p remains unchanged, and the overcurrent protection threshold value corresponding to the PMOS power tube decreases accordingly; if the power supply voltage VDD decreases, the first adjustable current signal Ic_p decreases, while the first reference current signal Iref_p remains unchanged, and the overcurrent protection threshold value corresponding to the PMOS power tube increases accordingly.

[0043] When the output voltage Vout changes, the overcurrent protection threshold value changes adaptively following the output voltage Vout; specifically, the overcurrent protection threshold value corresponding to the first power tube T1 is proportional to the output voltage Vout. If the output voltage Vout increases, the voltage across the PMOS power tube decreases, and the current that can be allowed to flow increases; in the first overcurrent detection circuit 21, the output voltage Vout increases, the first adjustable current signal Ic_p decreases, the first reference current signal Iref_p remains unchanged, and the overcurrent protection threshold value corresponding to the PMOS power tube increases accordingly; if the output voltage Vout decreases, the first adjustable current signal Ic_p increases, the first reference current signal Iref_p remains unchanged, and the overcurrent protection threshold value corresponding to the PMOS power tube decreases accordingly, thereby ensuring that the power amplifier works normally and is not burned due to overcurrent in abnormal situations.

[0044] like Figure 6 As shown, the second overcurrent detection circuit 22 includes a second current comparator C2, the first input end of the second current comparator C2 is used to receive the second current signal Ip_n, and the second input end of the second current comparator C2 is used to receive the second reference current signal Iref_n; when the second current signal Ip_n is greater than the second reference current signal Iref_n, the second current comparator C2 outputs a second overcurrent signal, the second current signal Ip_n includes a second sampled current signal Isense_n and a second adjustable current signal Ic_n, the second sampled current signal Isense_n is obtained by sampling the input current of the second power tube T2, that is, the second sampled current signal Isense_n is proportional to the input current of the second power tube T2, the second adjustable current signal Ic_n is the adjustable current in the second overcurrent detection circuit 22, and it is proportional to the output voltage Vout. The input signals of the second overcurrent detection circuit 22 are respectively the second adjustable current signal Ic_n, the second sampled current signal Isense_n and the second reference current signal Iref_n, and the output signal is the second overcurrent signal.

[0045] The second current signal Ip_n is formed by superimposing the second sampling current signal Isense_n and the second adjustable current signal Ic_n; when the power supply voltage VDD and the output voltage Vout are fixed, the second adjustable current signal Ic_n can be superimposed on the second sampling current signal Isense_n to obtain the second current signal Ip_n=Isense_n+Ic_n; the second current signal Ip_n and the second reference current signal Iref_n are input to the second current comparator C2 for comparison, and when Isense_n+Ic_n>Iref_n, the second current comparator C2 outputs a second overcurrent signal to shut down the power amplifier to prevent the power amplifier from burning out.

[0046] When the power supply voltage VDD changes, the overcurrent protection threshold value changes adaptively following the power supply voltage VDD. Specifically, the overcurrent protection threshold value corresponding to the second power tube T2 is inversely proportional to the power supply voltage VDD. If the power supply voltage VDD increases, the second adjustable current signal Ic_n increases, the second reference current signal Iref_n remains unchanged, and the overcurrent protection threshold value corresponding to the NMOS power tube decreases accordingly; if the power supply voltage VDD decreases, the second adjustable current signal Ic_n decreases, while the second reference current signal Iref_n remains unchanged, and the overcurrent protection threshold value corresponding to the NMOS power tube increases accordingly.

[0047] When the output voltage Vout changes, the overcurrent protection threshold value changes adaptively following the output voltage Vout; specifically, the overcurrent protection threshold value corresponding to the second power tube T2 is inversely proportional to the output voltage Vout. If the output voltage Vout increases, the voltage across the NMOS power tube increases, and the current that can be allowed to flow decreases; in the second overcurrent detection circuit 22, the output voltage Vout increases, the second adjustable current signal Ic_n increases, the second reference current signal Iref_n remains unchanged, and the overcurrent protection threshold value corresponding to the NMOS power tube decreases accordingly; if the output voltage Vout decreases, the second adjustable current signal Ic_n decreases, the second reference current signal Iref_n remains unchanged, and the overcurrent protection threshold value corresponding to the NMOS power tube increases accordingly, thereby ensuring that the power amplifier works normally and is not burned in abnormal situations.

[0048] In a specific embodiment, the first adjustable current signal Ic_p is formed by the product of the power supply voltage VDD and the first preset coefficient and the product of the first output signal and the second preset coefficient; the second adjustable current signal Ic_n is formed by the product of the power supply voltage VDD and the third preset coefficient and the product of the first output signal and the fourth preset coefficient; wherein the first preset coefficient, the third preset coefficient and the fourth preset coefficient are positive proportional coefficients less than 1, which can be designed according to actual needs, and the second preset coefficient is a negative proportional coefficient less than 0, which can be designed according to actual needs.

[0049] In another specific embodiment, Figure 4 As shown, the overcurrent protection circuit 20 further includes a current generating circuit 23, and the current generating circuit 23 is used to generate a first adjustable current signal Ic_p and a second adjustable current signal Ic_n, such as Figure 7 As shown, the current generating circuit 23 includes: a first amplifier A1, a second amplifier A2 and a third amplifier A3.

[0050] The first amplifier A1 includes a first input terminal, a second input terminal, a first output terminal and a second output terminal. The first input terminal of the first amplifier A1 is used to receive a reference voltage signal Vref. The second input terminal of the first amplifier A1 is coupled to a first auxiliary power supply (not shown in the figure). The first output terminal of the first amplifier A1 is coupled to a second auxiliary power supply (not shown in the figure) through a first resistor R1. The second output terminal of the first amplifier A1 is coupled to an auxiliary output terminal (not shown in the figure) through a second resistor R2. The first auxiliary power supply is used to generate a first auxiliary power supply voltage VDD. The second auxiliary power supply is used to generate a second auxiliary power supply voltage VDD. The first auxiliary power supply voltage VDD is a ratio of the power supply voltage VDD to a fifth preset coefficient. The second auxiliary power supply voltage VDD is a ratio of the power supply voltage VDD to a sixth preset coefficient. The auxiliary output terminal is used to output a second output signal. The second output signal is a ratio of the first output signal to a seventh preset coefficient.

[0051] Furthermore, the resistance value of the first resistor R1 is the same as that of the second resistor R2, the voltage difference across the first resistor R1 is the same as that across the second resistor R2, the first auxiliary power supply voltage VDD is a voltage divider of the power supply voltage VDD, and its voltage value is VDD / A, A is a fifth preset coefficient, which is an integer constant; the first auxiliary power supply voltage VDD and the reference voltage signal Vref are input into the first amplifier A1 to generate voltages V1 and V2, respectively, wherein V1=(Vout / B)+△V, V2=(VDD / C)+△V, and △V is the voltage difference across the first resistor R1.

[0052] The second amplifier A2 includes a first input terminal, a second input terminal and an output terminal. The first input terminal of the second amplifier A2 is coupled to the second auxiliary power supply. The second input terminal of the second amplifier A2 is coupled to the second output terminal of the first amplifier A1. The output terminal of the second amplifier A2 is used to output the first adjustable current signal Ic_p.

[0053] Furthermore, the second amplifier A2 is a voltage-to-current amplifier, and the second auxiliary power supply voltage VDD is a divided voltage of the power supply voltage VDD, whose voltage value is VDD / C, and C is a sixth preset coefficient, which is an integer constant, and the constant A and the constant C may be equal or different; the voltage VDD / C and the voltage V2 are input to the second amplifier A2 to generate a first adjustable current signal Ic_p.

[0054] The third amplifier A3 includes a first input terminal, a second input terminal and an output terminal. The first input terminal of the third amplifier A3 is coupled to the auxiliary output terminal. The second input terminal of the third amplifier A3 is coupled to the first output terminal of the first amplifier A1. The output terminal of the third amplifier A3 is used to output the second adjustable current signal Ic_n.

[0055] Furthermore, the third amplifier A3 is a voltage-to-current amplifier, and the second output signal is the divided voltage of the output voltage Vout, whose voltage value is Vout / B, and B is the seventh preset coefficient, which is an integer constant, and its value can be designed according to actual needs; the voltage Vout / B and the voltage V1 are input to the third amplifier A3 to generate a second adjustable current signal Ic_n.

[0056] The first adjustable current signal Ic_p and the second adjustable current signal Ic_n can be generated using the power supply voltage VDD and the output voltage Vout; the voltage difference is inversely proportional to the power supply voltage VDD, the first adjustable current signal Ic_p is proportional to the power supply voltage VDD, the first adjustable current signal Ic_p is inversely proportional to the output voltage Vout, and the second adjustable current signal Ic_n is proportional to the power supply voltage VDD and the output voltage Vout respectively.

[0057] The voltage VDD / A and the reference voltage signal Vref are input into the first amplifier A1, forming two currents, which flow through the first resistor R1 and the second resistor R2 respectively. The voltage difference △V decreases as the power supply voltage VDD increases, and increases as the power supply voltage VDD decreases; when the power supply voltage VDD increases, the first adjustable current signal Ic_p increases, and when the output voltage Vout increases, the first adjustable current signal Ic_p increases; when the power supply voltage VDD increases, the voltage difference △V decreases, and at the same time, the output voltage Vout also increases with the power supply voltage VDD. When the increase in the voltage Vout / B is greater than the increase in the voltage (VDD / C)+△V, the second adjustable current signal Ic_n increases; when the output voltage Vout increases, the second adjustable current signal Ic_n increases.

[0058] The control circuit 30 is used to generate a control signal after receiving an overcurrent signal to control the second amplifier circuit 40, the first drive circuit 111 and the second drive circuit 121 to shut down; specifically, once an overcurrent occurs, the control circuit 30 receives the overcurrent signal and sends a signal to the first drive circuit 111 and the second drive circuit 121 to control the power tube to shut down, so as to protect the power tube and prevent the power tube from burning out; at the same time, the control circuit 30 can also control the second amplifier circuit 40 to shut down, so that the input signal cannot enter the subsequent circuit, thereby achieving double-layer protection.

[0059] When the output of the power amplifier is abnormal, such as short-circuited to the power supply, that is, the output voltage Vout is close to the amplitude VDD of the power supply voltage VDD, the voltage across the PMOS power tube is small, the voltage across the NMOS power tube is large, and the NMOS power tube is overcurrent; or short-circuited to the ground, that is, the output voltage Vout is close to the amplitude VSS of the ground signal, the voltage across the NMOS power tube is small, the voltage across the PMOS power tube is large, and the PMOS power tube is overcurrent, thereby triggering the overcurrent protection circuit 20, the overcurrent protection circuit 20 sends an overcurrent signal to the control circuit 30, the control circuit 30 controls the second amplification circuit 40 to shut down, no longer receives the input signal, and acts on the first drive circuit 111 and the second drive circuit 121 at the same time, turning off the PMOS power tube and the NMOS power tube to prevent the power tube from being burned; when the output of the power amplifier returns to normal, the overcurrent protection circuit 20 no longer generates an overcurrent signal, and the entire power amplifier returns to normal operation.

[0060] In order to ensure the normal operation of the entire power amplifier, the first output signal can be fed back to the second amplifier circuit 40 through the feedback circuit 50, that is, Figure 4 As shown, the power amplifier also includes a feedback circuit 50, the output end of the feedback circuit 50 is coupled to the input end of the second amplifier circuit 40, and is used to process the received first output signal, generate a feedback signal, and input the feedback signal to the second amplifier circuit 40; the second amplifier circuit 40 is also used to adjust the amplitudes of the first amplified signal and the second amplified signal after receiving the feedback signal, so that the amplitude of the first output signal is within a preset amplitude range.

[0061] In a specific embodiment, the overcurrent protection structure in this embodiment is used for simulation, and the following is obtained: Figure 8-Figure 10 The simulation results shown; Figure 8 It is a simulation curve of the overcurrent protection threshold corresponding to the PMOS power tube when the power supply voltage VDD is fixed, Vsd is the voltage between the source and the drain of the PMOS power tube, Vsd=VDD-Vout, the power supply voltage VDD is 16V, when the output voltage Vout=2V, that is, Vsd=14V, the voltage across the PMOS power tube is large, and the overcurrent protection circuit 20 adaptively adjusts the overcurrent protection threshold to a relatively small value: 2.0678A; when the output voltage Vout=14V, that is, Vsd=2V, the voltage across the PMOS power tube is small, and the overcurrent protection circuit 20 adaptively adjusts the overcurrent protection threshold to a relatively large value: 4.6293A, thereby achieving a larger output power and ensuring that the power tube is not burned.

[0062] Fig. 9It is the over-current protection threshold simulation curve corresponding to the NMOS power tube when the power supply voltage VDD is fixed, Vds is the voltage between the drain and the source of the NMOS power tube, Vds=Vout-VSS, the voltage VSS is 0V, the power supply voltage VDD is 16V, when the output voltage Vout=2V, that is, Vds=2V, the voltage across the NMOS power tube is small, and the over-current protection circuit 20 adaptively adjusts the over-current protection threshold to a relatively large value: 4.6468A; when the output voltage Vout=14V, that is, Vds=14V, the voltage across the NMOS power tube is large, and the over-current protection circuit 20 automatically adjusts the over-current protection threshold to a relatively small value: 2.3799A, thereby achieving a larger output power and ensuring that the power tube is not burned.

[0063] Fig.10 is the overcurrent protection threshold of the PMOS power tube under different power supply voltages VDD. The "+" line represents the case where the power supply voltage VDD is 10V, and the "□" line represents the case where the power supply voltage VDD is 16V. From the simulation results, it can be seen that when the voltages at both ends of the PMOS power tube are equal, for example, when Vsd is 2V, the lower the power supply voltage VDD, the higher the overcurrent protection threshold.

[0064] Fig.11 is the over-current protection threshold of the NMOS power tube under different power supply voltages VDD. The "+" line represents the case where the power supply voltage VDD is 10V, and the "□" line represents the case where the power supply voltage VDD is 16V. From the simulation results, it can be seen that when the voltages at both ends of the NMOS power tube are equal, such as when Vds is 2V, the lower the power supply voltage VDD, the higher the over-current protection threshold.

[0065] When the output voltage Vout of the power amplifier is close to the power supply voltage VDD, the voltage across the PMOS power tube is relatively small, and the voltage across the NMOS power tube is relatively large. To ensure that the power of the power tube is not too large and avoid burning the power amplifier, the overcurrent protection circuit 20 can adaptively increase the overcurrent protection threshold It_p of the PMOS power tube according to the power supply voltage VDD and the output voltage Vout, and adaptively reduce the overcurrent protection threshold It_n of the NMOS power tube. At this time, the maximum output current (It_p-It_n) at the output end of the power amplifier can be as large as possible without burning the power amplifier, thereby increasing the output power; similarly, when the output voltage Vout of the power amplifier is close to the voltage VSS, the overcurrent protection circuit 20 adaptively adjusts the overcurrent protection threshold of the power tube according to the power supply voltage VDD and the output voltage Vout, so that the output power becomes larger; therefore, the maximum power output by the power amplifier can be maximized at different power supply voltages VDD and output voltages Vout, while ensuring that the power tube is not burned.

[0066] In this embodiment, the power supply voltage VDD and the output voltage Vout are introduced into the overcurrent protection circuit 20, so that the overcurrent protection threshold is adaptively adjusted following the power supply voltage VDD and the voltage at both ends of the power tube. When the power supply voltage VDD increases, the overcurrent protection threshold is adaptively reduced. When the voltage at both ends of the power tube increases, the overcurrent protection threshold is adaptively reduced, so that the maximum power output of the power amplifier becomes larger, which can not only ensure the normal output function of the power amplifier, but also prevent the power amplifier from being burned due to excessive power of the power tube. In addition, when the power supply voltage VDD and the output are different, the maximum power limit on the power tube changes less, and the power change at both ends of the power tube can be kept relatively fixed under the application conditions of a large range of power supply changes and a large output swing, thereby reducing the requirements on the extreme parameters of the power tube (such as the safe working area).

[0067] The above are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A power amplifier based on adaptive overcurrent protection, characterized in that: At least: A first amplifier circuit, used to amplify an input signal to generate a first output signal; an overcurrent protection circuit, coupled to the output end of the first amplifier circuit, and configured to generate an overcurrent signal when it is determined that the output current of the first amplifier circuit is greater than an overcurrent protection threshold, wherein the overcurrent protection threshold changes with the first output signal; a control circuit, coupled to the overcurrent protection circuit and the first amplifying circuit respectively, and configured to control the first amplifying circuit to be disconnected according to the overcurrent signal; Wherein, the first amplifier circuit includes a first driving power amplifier circuit; The first driving power amplifier circuit comprises: A first driving circuit coupled to the control circuit; a first power tube, comprising a first end, a second end and a third end, wherein the first end of the first power tube is coupled to the first driving circuit, the second end of the first power tube is coupled to a power supply end, and the first driving circuit is used to output a first driving signal to the first power tube to drive the first power tube; The overcurrent protection circuit includes: a first current comparator, wherein the first input end of the first current comparator is used to receive a first current signal, and the second input end of the first current comparator is used to receive a first reference current signal; when the first current signal is greater than the first reference current signal, the first current comparator outputs a first overcurrent signal, wherein the first current signal includes a first sampled current signal and a first adjustable current signal, the first sampled current signal is obtained by sampling the output current of the first power tube, the first adjustable current signal is formed by superimposing the product of the power supply voltage and a first preset coefficient and the product of the first output signal and a second preset coefficient, the first adjustable current signal is proportional to the power supply voltage, and the first adjustable current signal is inversely proportional to the first output signal.

2. The power amplifier based on adaptive overcurrent protection according to claim 1, characterized in that: The power amplifier further comprises: a second amplifier circuit coupled to the output end of the control circuit, used for processing the input signal, outputting the first amplified signal and the second amplified signal to the first amplifier circuit, and stopping working when receiving the control signal output by the control circuit; the first drive circuit is coupled to the second amplifier circuit and the control circuit respectively; The first amplifying circuit further includes: The second driving power amplifier circuit is coupled to the control circuit, the second amplifier circuit and the first driving power amplifier circuit respectively, and is used to amplify the second amplified signal, wherein the first amplified signal and the second amplified signal have the same amplitude and opposite phase.

3. The power amplifier based on adaptive overcurrent protection according to claim 2, characterized in that: The second driving power amplifier circuit comprises: A second driving circuit is coupled to the second amplifying circuit and the control circuit respectively; a second power tube, comprising a first end, a second end and a third end, wherein the first end of the second power tube is coupled to the second driving circuit, the second end of the second power tube is coupled to the ground end, the third end of the second power tube is coupled to the third end of the first power tube, and the second driving circuit is used to output a second driving signal to the second power tube to drive the second power tube; Wherein, the control circuit is also used to generate the control signal after receiving the overcurrent signal to control the second amplifying circuit, the first driving circuit and the second driving circuit to be turned off, and the overcurrent protection threshold also changes with the power supply voltage.

4. The power amplifier based on adaptive overcurrent protection according to claim 3, characterized in that: The overcurrent protection threshold includes a first overcurrent protection threshold and a second overcurrent protection threshold, the overcurrent signal includes a first overcurrent signal and a second overcurrent signal, and the overcurrent protection circuit includes: a first overcurrent detection circuit, the first overcurrent detection circuit comprising the first current comparator, coupled to the third end of the first power tube, and used to detect whether the output current of the first power tube is greater than the first overcurrent protection threshold, and if so, generate the first overcurrent signal; The second overcurrent detection circuit is coupled to the third end of the second power tube and is used to detect whether the input current of the second power tube is greater than the second overcurrent protection threshold. If so, the second overcurrent signal is generated.

5. The power amplifier based on adaptive overcurrent protection according to claim 4, characterized in that: The second overcurrent detection circuit comprises a second current comparator, a first input terminal of the second current comparator is used to receive a second current signal, and a second input terminal of the second current comparator is used to receive a second reference current signal; When the second current signal is greater than the second reference current signal, the second current comparator outputs the second overcurrent signal, wherein the second current signal includes a second sampled current signal and a second adjustable current signal, and the second sampled current signal is obtained by sampling the input current of the second power tube; The second adjustable current signal is formed by superimposing the product of the power supply voltage and a third preset coefficient and the product of the first output signal and a fourth preset coefficient, and the second adjustable current signal is proportional to the power supply voltage and the first output signal respectively.

6. The power amplifier based on adaptive overcurrent protection according to claim 5, characterized in that: The overcurrent protection circuit further includes a current generating circuit, and the current generating circuit is used to generate the first adjustable current signal and the second adjustable current signal, and the current generating circuit includes: A first amplifier, comprising a first input terminal, a second input terminal, a first output terminal and a second output terminal, wherein the first input terminal of the first amplifier is used to receive a reference voltage signal, the second input terminal of the first amplifier is coupled to a first auxiliary power supply, the first output terminal of the first amplifier is coupled to a second auxiliary power supply through a first resistor, and the second output terminal of the first amplifier is coupled to an auxiliary output terminal through a second resistor, wherein the first auxiliary power supply is used to generate a first auxiliary power supply voltage, the second auxiliary power supply is used to generate a second auxiliary power supply voltage, the first auxiliary power supply voltage is a ratio of the power supply voltage to a fifth preset coefficient, the second auxiliary power supply voltage is a ratio of the power supply voltage to a sixth preset coefficient, and the auxiliary output terminal is used to output a second output signal, and the second output signal is a ratio of the first output signal to a seventh preset coefficient; a second amplifier, comprising a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the second amplifier is coupled to the second auxiliary power supply, the second input terminal of the second amplifier is coupled to the second output terminal of the first amplifier, and the output terminal of the second amplifier is used to output the first adjustable current signal; The third amplifier includes a first input terminal, a second input terminal and an output terminal. The first input terminal of the third amplifier is coupled to the auxiliary output terminal, the second input terminal of the third amplifier is coupled to the first output terminal of the first amplifier, and the output terminal of the third amplifier is used to output the second adjustable current signal.

7. The power amplifier based on adaptive overcurrent protection according to claim 6, characterized in that: The voltage difference across the first resistor is the same as the voltage difference across the second resistor, the voltage difference across the first resistor is inversely proportional to the power supply voltage, and the voltage difference across the second resistor is inversely proportional to the power supply voltage.

8. The power amplifier based on adaptive overcurrent protection according to claim 5, characterized in that: The overcurrent protection threshold corresponding to the first power tube is proportional to the first output signal, and the overcurrent protection threshold corresponding to the first power tube is inversely proportional to the power supply voltage; The over-current protection threshold corresponding to the second power tube is inversely proportional to the first output signal, and the over-current protection threshold corresponding to the second power tube is inversely proportional to the power supply voltage.

9. The power amplifier based on adaptive overcurrent protection according to claim 3, characterized in that: The power amplifier further comprises: A feedback circuit is coupled to the second amplifier circuit, and is used to process the received first output signal, generate a feedback signal, and input the feedback signal to the second amplifier circuit; the second amplifier circuit is also used to adjust the amplitudes of the first amplified signal and the second amplified signal after receiving the feedback signal, so that the amplitude of the first output signal is within a preset amplitude range.

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