Audio power amplifier startup noise suppression circuit
By combining field-effect transistors and delay circuits, the smooth rise of the power supply voltage of the audio power amplifier chip is controlled, which solves the problem of startup noise in the audio power amplifier and achieves noiseless startup and improved reliability.
Patent Information
- Authority / Receiving Office
- CN ยท China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SICHUAN ILINK TECH CO LTD
- Filing Date
- 2025-09-19
- Publication Date
- 2026-07-31
AI Technical Summary
In existing technologies, the POP noise problem caused by sudden changes in power supply voltage during startup of audio power amplifiers is difficult to suppress effectively, especially in older models or low-cost chips.
The combination of first and second field-effect transistors, current-limiting resistors, and delay circuits is used. By cooperating with the field-effect transistors, the power supply voltage of the power amplifier chip is controlled to rise smoothly, and the reliability of the circuit is improved by voltage regulation and discharge diodes.
It achieves the elimination of complex programming timing or additional control chips, physically avoids the impact of power supply voltage surges on audio amplifiers, completely eliminates startup noise, and improves circuit reliability and response speed.
Smart Images
Figure CN224583156U_ABST
Abstract
Description
Technical Field
[0001] This utility model mainly relates to the field of circuit design, and in particular to an audio power amplifier startup noise suppression circuit. Background Technology
[0002] Audio amplifiers are widely used in various audio devices due to their high efficiency. However, their working principle causes significant transient voltages at the output terminal during the power-on initialization phase due to sudden changes in the power supply voltage and the energization process of the internal modulator. After being filtered and restored, this voltage drives the speaker and produces an unpleasant "bang" or "click" sound, commonly known as pop noise or impact noise.
[0003] In existing technologies, most solutions rely on soft-start and mute circuits integrated within the power amplifier chip. These circuits suppress noise by controlling the chip's enable pin via an MCU and following a specific power-on sequence. However, for some older chips or chips with inherently weak noise reduction capabilities, the noise reduction effect is not ideal. Furthermore, some low-cost solutions may lack these functionalities entirely. Therefore, a universal, effective external circuit solution that is independent of specific chip architecture is needed to fundamentally solve the startup noise problem of audio power amplifiers. Utility Model Content
[0004] The technical problem to be solved by this utility model is to provide an audio power amplifier startup noise suppression circuit for eliminating audio power amplifier startup noise caused by sudden changes in power supply voltage.
[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: An audio power amplifier startup noise suppression circuit is provided. The circuit includes a first field-effect transistor, a second field-effect transistor, a current-limiting resistor, and a delay circuit. The source of the first transistor is connected to the power input terminal through the delay circuit, the drain is connected to the power input terminal of the power amplifier chip, the gate is connected to the drain of the second transistor, the gate of the second transistor is connected to the signal output terminal of the power amplifier chip MCU through the current-limiting resistor, and the source is grounded.
[0006] Furthermore, the first field-effect transistor is a P-channel field-effect transistor.
[0007] Furthermore, the second field-effect transistor is an N-channel field-effect transistor.
[0008] Furthermore, the delay circuit is an RC circuit.
[0009] Furthermore, the circuit also includes a discharge diode, with its anode grounded and its cathode connected to the gate of the first field-effect transistor.
[0010] Furthermore, the circuit also includes a Zener diode, the cathode of which is connected to the gate of the first field-effect transistor, and the anode is grounded.
[0011] Furthermore, the second field-effect transistor is a small-signal transistor.
[0012] The beneficial effects of this utility model are: (1) By using the delay circuit in conjunction with the first and second field-effect transistors, the first field-effect transistor is used as the main switch for the power amplifier power input signal, and the second field-effect transistor is used as the low-voltage control switch. This controls the power supply voltage of the power amplifier chip to achieve a linear and smooth rise. No complex programming timing or additional control chip is required. This physically avoids the impact of sudden power supply voltage changes on the audio power amplifier chip, thereby fundamentally eliminating the POP noise generated during power-on. (2) Add a Zener diode to clamp the gate voltage of the first field-effect transistor to prevent breakdown. At the same time, add a discharge diode to accelerate the turn-off process of the first field-effect transistor, so that the power supply voltage of the power amplifier chip can be quickly cut off, thereby improving the reliability of the circuit. Attached Figure Description
[0013] Figure 1 Here is a schematic diagram of the audio power amplifier startup noise suppression circuit described in this utility model: In the attached diagram: Q1 is the first field-effect transistor, Q2 is the second field-effect transistor, R1 is the first resistor, R2 is the second resistor, and C1 is the first capacitor. Detailed Implementation
[0014] like Figure 1 As shown, the audio power amplifier startup noise suppression circuit of this utility model includes a first field-effect transistor Q1 and a second field-effect transistor Q2, a current-limiting resistor R1, and a delay circuit. The source (S) of the first transistor Q1 is connected to the power input terminal (+VCC) through the delay circuit, and the drain (D) outputs a controlled voltage (VCC_AMP) to the power supply pin of the power amplifier chip. The gate (G) is connected to the drain of the second field-effect transistor. The gate of the second field-effect transistor is connected to the signal output terminal of the power amplifier chip MCU through the second resistor R2. The source of the second field-effect transistor Q2 is grounded. The second resistor R2 is used to limit the maximum current of the gate to prevent the pin of the MCU from being damaged by the surge current.
[0015] As a preferred embodiment, considering cost and performance, the first field-effect transistor Q1 is a P-type field-effect transistor and the second field-effect transistor Q2 is an N-type field-effect transistor. Furthermore, since the second field-effect transistor Q2 is controlled by the GPIO pin level signal of the MCU, the second field-effect transistor Q2 is preferably a small-signal transistor.
[0016] The delay circuit is an RC delay circuit, which consists of a first resistor R1 and a first capacitor C1 connected in series. One end of the first resistor R1 is connected to the power input terminal, and the other end is connected to one end of the first capacitor C1. The connection point is also connected to the gate of the first field-effect transistor Q1, and the other end of the first capacitor C1 is grounded.
[0017] When the MCU signal output control signal (MCU_CTRL) is low, the second field-effect transistor Q2 is turned off, the first capacitor C1 is charged through the first resistor R1, the gate voltage of the first field-effect transistor Q1 is equal to the power supply voltage, the gate-source voltage difference Vgs=0V, and the first field-effect transistor Q1 is in the off state. When the MCU signal output control signal is high, the second field-effect transistor Q2 is turned on, which causes the RC delay circuit to start discharging. Since the voltage of the first capacitor C1 cannot change abruptly, the gate voltage of the first field-effect transistor Q1 slowly decreases after the RC delay circuit starts discharging, allowing it to slowly enter the linear region and eventually the saturation region from the cutoff region. This enables the power amplifier chip's supply voltage (VCC_AMP) to rise smoothly and linearly from 0V to the power supply voltage, and the current of the power amplifier chip increases slowly, allowing the current in each unit circuit inside to conduct smoothly, thus completely avoiding the impact noise caused by voltage change.
[0018] Preferably, the audio power amplifier startup noise suppression circuit of this utility model further includes a discharge diode and a Zener diode; the anode of the discharge diode is grounded and the cathode is connected to the gate of the first field-effect transistor Q1, which is used to accelerate the turn-off process of the first field-effect transistor Q1, so that the power supply voltage of the power amplifier chip can be quickly cut off, thereby improving the response speed of the circuit; the cathode of the Zener diode is connected to the gate of the first field-effect transistor Q1 and the anode is grounded, which is used to clamp the gate voltage of the first field-effect transistor Q1 to prevent breakdown.
Claims
1. An audio power amplifier startup noise suppression circuit, characterized by, The circuit includes a first field-effect transistor, a second field-effect transistor, a current-limiting resistor, and a delay circuit. The source of the first transistor is connected to the power input terminal through the delay circuit, the drain is connected to the power input terminal of the power amplifier chip, the gate is connected to the drain of the second transistor, the gate of the second transistor is connected to the signal output terminal of the power amplifier chip MCU through the current-limiting resistor, and the source is grounded.
2. The audio power amplifier startup noise suppression circuit of claim 1, wherein, The first field-effect transistor is a P-channel field-effect transistor.
3. The audio power amplifier startup noise suppression circuit of claim 2, wherein, The second field-effect transistor is an N-channel field-effect transistor.
4. The audio power amplifier startup noise suppression circuit of any one of claims 1-3, wherein, The delay circuit is an RC circuit.
5. The audio power amplifier startup noise suppression circuit according to any one of claims 1-3, characterized in that, The circuit also includes a discharge diode, with its anode grounded and its cathode connected to the gate of the first field-effect transistor.
6. The audio power amplifier startup noise suppression circuit according to any one of claims 1-3, characterized in that, The circuit also includes a Zener diode, the cathode of which is connected to the gate of the first field-effect transistor, and the anode is grounded.
7. The audio power amplifier startup noise suppression circuit according to any one of claims 1-3, characterized in that, The second field-effect transistor is a small-signal transistor.