A dynamic temperature drift compensation system for an audio power amplifier

Abstract

The utility model discloses a kind of dynamic temperature drift compensation systems for audio power amplifier, belong to electronic circuit technical field, to solve the problem of static operating point drift caused by temperature variation of existing amplifier. The circuit includes output stage, drive stage and bias circuit;The drive stage includes driving transistor, for driving including power transistor output stage;The bias circuit includes the base bias resistor connected to the base of driving transistor. The utility model is by using the characteristic that resistance value of thermistor drops with temperature rise, dynamically pulls low the base voltage of driving transistor, to compensate temperature drift reversely, can stabilize static operating point in real time, effectively suppress output distortion, improve the reliability of amplifier. The scheme simple structure, low cost, easy to implement.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a dynamic temperature drift compensation system for an audio power amplifier. Background Technology

[0002] Audio power amplifiers, especially Class AB amplifiers, are an indispensable core component of audio systems. The realization of their high-fidelity sound quality largely depends on the precise and stable static operating point setting of the output stage power transistors. This static operating point directly determines the magnitude of crossover distortion in the output signal and the overall efficiency of the amplifier.

[0003] However, power transistors generate a significant amount of heat due to power consumption during prolonged high-load operation, causing a substantial increase in the temperature of the transistor itself and surrounding components. The physical characteristics of semiconductor transistors are extremely sensitive to temperature; an increase in temperature will predictably cause a decrease in their base-emitter voltage.

[0004] In traditional fixed-bias circuits, this drop in base-emitter voltage directly disrupts the original bias balance, causing the quiescent operating current to increase uncontrollably and rapidly. This phenomenon is known as quiescent operating point drift, which not only introduces severe crossover distortion and degrades sound quality, but in extreme cases can even trigger thermal runaway, ultimately burning out expensive power transistors.

[0005] To suppress this temperature drift effect, existing technologies often employ static compensation measures, such as using fixed resistor voltage divider networks or simple thermistors. However, these static or passive compensation methods have fixed compensation characteristics and cannot track the actual temperature changes of power transistors in real time and accurately. They suffer from fundamental defects such as response lag and insufficient compensation accuracy, making it difficult to provide ideal compensation effects over a wide range of operating temperatures and loads.

[0006] Therefore, this invention proposes a temperature drift compensation technology for audio power amplifiers to address the shortcomings of existing technologies. Utility Model Content

[0007] To overcome the above deficiencies, this utility model provides a dynamic temperature drift compensation system for audio power amplifiers. It aims to improve the problem in the prior art where the bias circuit of an audio power amplifier cannot dynamically respond to the operating temperature, causing the static operating point to drift as the temperature rises, which in turn degrades the sound quality and poses a risk of thermal runaway.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a dynamic temperature drift compensation system for an audio power amplifier, comprising: an output stage, the output stage including a power transistor; a drive stage, the drive stage including a drive transistor; a bias circuit, the bias circuit including a base bias resistor; and a negative temperature coefficient thermistor.

[0009] The output terminal of the driving transistor is electrically connected to the input terminal of the power transistor to form a bias path for setting the static operating point of the power transistor.

[0010] The base bias resistor is connected between the base of the driving transistor and the reference potential, and the negative temperature coefficient thermistor is combined with the base bias resistor in parallel.

[0011] Preferably, the negative temperature coefficient thermistor is physically attached to the power transistor or a heat sink configured for the power transistor.

[0012] Preferably, the power transistors of the output stage form a push-pull output circuit.

[0013] Preferably, the power transistor includes an NPN power transistor and a PNP power transistor, which together form a complementary output structure.

[0014] Preferably, the dynamic temperature drift compensation system for the audio power amplifier further includes a first emitter resistor and a second emitter resistor, wherein the emitter of the NPN power transistor is connected to the output terminal through the first emitter resistor, and the emitter of the PNP power transistor is connected to the output terminal through the second emitter resistor.

[0015] Preferably, the dynamic temperature drift compensation system for the audio power amplifier further includes a Miller compensation capacitor connected between the base and collector of the driving transistor.

[0016] Preferably, the dynamic temperature drift compensation system for the audio power amplifier further includes a global negative feedback network, which is used to feed back the output signal of the output stage to the input of the driver stage.

[0017] Conveniently, the global negative feedback network includes a feedback resistor led out from the output terminal of the output stage and a grounding resistor connected to the input terminal of the drive stage.

[0018] Preferably, at ambient temperature, the nominal resistance value of the negative temperature coefficient thermistor is greater than the resistance value of the base bias resistor.

[0019] This utility model has the following beneficial effects: 1. In this utility model, by connecting a negative temperature coefficient thermistor in parallel with a base bias resistor in the base bias circuit of the driving transistor, the problem of the bias circuit being unable to dynamically adjust with temperature changes, causing the amplifier's static operating point to drift, is solved. This achieves the technical effect of real-time dynamic compensation for temperature drift and stabilization of the static operating point, significantly improving the amplifier's working stability and reliability.

[0020] 2. In this utility model, by using a negative temperature coefficient thermistor to sense the temperature in real time and adjust the bias voltage in reverse, the problem of increased crossover distortion caused by the amplifier's static operating point deviating from the optimal region due to temperature rise is solved, achieving the technical effect of effectively suppressing output signal distortion and ensuring consistent audio output quality. Attached Figure Description

[0021] Figure 1 The present invention provides a circuit diagram of a dynamic temperature drift compensation system for an audio power amplifier. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] Reference Figure 1 The present invention provides an embodiment of a dynamic temperature drift compensation system for an audio power amplifier, which aims to solve the problem of static operating point drift caused by the lack of a dynamic temperature compensation structure in existing audio power amplifiers.

[0024] like Figure 1As shown, the dynamic temperature drift compensation system for an audio power amplifier includes an output stage, a driver stage, and a bias circuit that provides bias for the driver stage. The driver stage is electrically connected to the output stage to drive the output stage. The driver stage includes a driver transistor Q3, and the output stage includes power transistors Q1 and Q2. The output terminal of the driver transistor Q3 is electrically connected to the input terminals of the power transistors Q1 and Q2 to form a bias path for setting the quiescent operating point of the power transistors Q1 and Q2. The driver stage includes a base bias resistor R6 and a negative temperature coefficient thermistor R7. The base bias resistor R6 is connected to... The negative temperature coefficient thermistor R7 and the base bias resistor R6 are connected in parallel between the base of the driving transistor Q3 and the reference potential, forming a parallel resistor network that is sensitive to temperature changes. When the temperature of the power transistors Q1 and Q2 or the driving transistor Q3 increases due to operation, the resistance of the negative temperature coefficient thermistor R7 will decrease accordingly, thereby causing the total resistance of the entire parallel resistor network to decrease, which in turn lowers the base voltage of the driving transistor Q3. Finally, the bias path suppresses the increasing trend of the static operating current of the power transistors Q1 and Q2, realizing dynamic compensation for temperature drift.

[0025] The mounting position of the negative temperature coefficient thermistor R7 is such that it is physically and tightly attached to the power transistor Q1 or Q2, or physically and tightly attached to the heat sink configured for the power transistors Q1 and Q2. This ensures that the negative temperature coefficient thermistor R7 can sense the temperature change of the power transistor, which is the main heat source of the circuit, in real time and accurately, thereby providing a precise temperature input signal for dynamic compensation. Specifically, the power transistors in this output stage form a push-pull output circuit. Specifically, the power transistors include an NPN power transistor Q1 and a PNP power transistor Q2. The NPN power transistor Q1 and the PNP power transistor Q2 together form a complementary output structure. The emitter of the NPN power transistor Q1 is connected to the output terminal VOUT through a first emitter resistor R1, and the emitter of the PNP power transistor Q2 is connected to the same output terminal VOUT through a second emitter resistor R2. This push-pull complementary structure can amplify the power of the positive and negative half-cycles of the signal respectively. The setting of the first emitter resistor R1 and the second emitter resistor R2 provides local current negative feedback for power transistors Q1 and Q2, enhancing the stability of the static operating point.

[0026] To ensure the stability of the amplifier at high frequencies and prevent self-oscillation, the circuit also includes a Miller compensation capacitor C1. This Miller compensation capacitor C1 is connected between the base and collector of the driving transistor Q3. Through the Miller effect, it introduces a dominant pole in the circuit, thereby optimizing the frequency response characteristics of the amplifier.

[0027] To improve the amplifier's linearity and stabilize the closed-loop gain, a global negative feedback network is also included in the circuit. This global negative feedback network is used to feed back the output signal of the output stage to the input of the driver stage. Specifically, the global negative feedback network includes a feedback resistor R11 and a grounding resistor R12. The feedback resistor R11 is led out from the output terminal VOUT of the output stage and connected to the input terminal of the driver stage, while the grounding resistor R12 is connected to the input terminal of the driver stage and to the circuit's reference ground. The closed-loop gain of the amplifier is determined by the ratio of the resistance values ​​of the feedback resistor R11 to the grounding resistor R12.

[0028] In another preferred embodiment, at ambient temperature, the nominal resistance of the negative temperature coefficient thermistor R7 is greater than the resistance of the base bias resistor R6. For example, the nominal resistance of the negative temperature coefficient thermistor R7 is 1.2 kΩ, while the resistance of the base bias resistor R6 is 120 Ω.

[0029] Working principle: In the initial state or when operating at low temperature, the negative temperature coefficient thermistor R7 exhibits a high resistance value, and its total resistance value after being connected in parallel with the base bias resistor R6 is also high. This total resistance value sets the base bias voltage of the driving transistor Q3, thereby establishing a suitable initial static operating current in the power transistors Q1 and Q2 through the bias path.

[0030] When the audio power amplifier operates at high power for a long time, the power transistors Q1 and Q2, as the main heat sources, will have a significant increase in temperature. Since the negative temperature coefficient thermistor R7 is physically in close contact with the power transistor or its heat sink, its own temperature will also rise rapidly, resulting in a significant decrease in its resistance value. As the resistance value of the negative temperature coefficient thermistor R7 decreases, its total resistance value after being connected in parallel with the base bias resistor R6 also decreases.

[0031] The reduction in the total parallel resistance directly lowers the base voltage of the driving transistor Q3. This reduction in base voltage alters the operating state of the driving transistor Q3, weakening its bias driving capability for power transistors Q1 and Q2. This weakened bias driving precisely offsets the increasing trend of static current caused by the decrease in the base-emitter voltage of the power transistors due to rising temperature. This dynamically stabilizes the static operating point within a preset ideal range, effectively suppressing thermal drift and avoiding the deterioration of crossover distortion and the risk of thermal runaway.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A dynamic temperature drift compensation system for an audio power amplifier, characterized in that, It includes: Output stage, the output stage including power transistors; A driving stage, comprising a driving transistor, wherein the output of the driving transistor is electrically connected to the input of the power transistor to form a bias path for setting the static operating point of the power transistor; A bias circuit, the bias circuit including a base bias resistor connected between the base of the driving transistor and a reference potential; The bias circuit also includes a negative temperature coefficient thermistor, which is connected in parallel with the base bias resistor.

2. The dynamic temperature drift compensation system for an audio power amplifier according to claim 1, characterized in that, The negative temperature coefficient thermistor is physically attached to the power transistor or a heat sink configured for the power transistor.

3. The dynamic temperature drift compensation system for an audio power amplifier according to claim 1, characterized in that, The power transistors of the output stage form a push-pull output circuit.

4. The dynamic temperature drift compensation system for an audio power amplifier according to claim 3, characterized in that, The power transistors include NPN type power transistors and PNP type power transistors, which together form a complementary output structure.

5. The dynamic temperature drift compensation system for an audio power amplifier according to claim 4, characterized in that, The emitter of the NPN power transistor is connected to the output terminal through a first emitter resistor, and the emitter of the PNP power transistor is connected to the output terminal through a second emitter resistor.

6. The dynamic temperature drift compensation system for an audio power amplifier according to claim 1, characterized in that, It also includes a Miller compensation capacitor, which is connected between the base and collector of the driving transistor.

7. The dynamic temperature drift compensation system for an audio power amplifier according to claim 1, characterized in that, It also includes a global negative feedback network, which is used to feed back the output signal of the output stage to the input of the driver stage.

8. The dynamic temperature drift compensation system for an audio power amplifier according to claim 7, characterized in that, The global negative feedback network includes a feedback resistor drawn from the output terminal of the output stage and a grounding resistor connected to the input terminal of the drive stage.

9. The dynamic temperature drift compensation system for an audio power amplifier according to claim 1, characterized in that, At ambient temperature, the nominal resistance of the negative temperature coefficient thermistor is greater than the resistance of the base bias resistor.

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