Protection circuit capable of realizing rapid shutdown, muting and impact prevention

Abstract

The utility model provides a quick shutdown mute anti-impact protection circuit, which comprises a transformer, a first circuit, a second circuit and a third circuit, the first circuit is connected with the second circuit through a resistor R3, the output end of the transformer is respectively connected with one end of the first circuit and one end of the second circuit, and the other end of the first circuit is connected with the third circuit. And two ends of the third circuit are respectively connected with the other end of the first circuit and the other end of the second circuit, and the third end of the third circuit is an output end, so that impact sound emitted by the loudspeaker in the shutdown process can be effectively prevented, rapid mute is realized, and the reliability is good.

Description

Technical Field

[0001] The utility model relates to the technical field of audio circuits, and particularly relates to a protection circuit for quick shutdown, silent operation and shock prevention. Background Art

[0002] Nowadays, there is a great variety of electronic products, which are all applied in daily life, such as televisions, refrigerators, electric fans, audio systems, etc. Before using an audio system, it needs to be powered on, and after use, it needs to be powered off. When a user turns on or off the audio system, there will be a "bang" impact sound. The main reason is that when powering on and off, due to the inconsistent power-on and power-off timings, the instantaneous change of the electrical signal in the circuit constitutes an impact on the circuit. After being output through the amplification circuit, the loudspeaker emits noise, which may damage the loudspeaker, and at the same time, it will bring a very bad user experience to the user and even affect the human ear's hearing system.

[0003] At present, some technical solutions have been proposed in China to solve the above problems. For example, the patent document with the Chinese patent number 201710966409.2 and the publication date of December 15, 2020 discloses an audio power-on / off shock prevention and output short-circuit protection circuit, including a voltage stabilization circuit, a delay circuit, an electronic switch, a mute circuit, a short-circuit detection circuit, a shutdown discharge circuit, and a negative voltage circuit; the voltage stabilization circuit is composed of diode N1, diode N2, diode N3, resistor R1, resistor R2, resistor R3, and capacitor C1 to provide stable voltage for the circuit; the delay circuit is composed of resistor R4, resistor R5, resistor R6, capacitor C2, capacitor C3, diode N4, and triode T2 for power-on delay.

[0004] In the above document, when shutting down, resistor R2 discharges. Since the capacitance of capacitor C1 is very small, triode T1 conducts immediately, and triode T2 immediately loses its operating voltage, and triode T3 immediately cuts off, thus avoiding the occurrence of sound and realizing shock prevention; however, in this circuit, when shutting down, it needs to rely on resistor R2 for discharging and it is necessary to ensure that the capacitance on capacitor C1 is small. Moreover, discharging through resistor R2 cannot achieve quick discharge, and if the capacitance of capacitor C1 is affected by the outside and is not small, it cannot more reliably ensure quick discharge. In addition, since there are capacitor components such as capacitor C2 between triode T1 and triode T2, when triode T1 cuts off, due to the existence of capacitor C2, triode T2 cannot cut off instantaneously, thus making it impossible to reliably achieve the quick mute function. Summary of the Invention

[0005] The purpose of the utility model is to provide a protection circuit for quick shutdown, silent operation and shock prevention, which can effectively prevent the impact sound emitted by the loudspeaker during the shutdown process, realize quick mute, and has high reliability.

[0006] To achieve the above object, the present utility model provides a protection circuit for fast shutdown, silent operation and impact prevention, which includes a transformer, a first circuit, a second circuit and a third circuit. The first circuit is connected to the second circuit through a resistor R3. The output terminals of the transformer are respectively connected to one end of the first circuit and one end of the second circuit. Both ends of the third circuit are respectively connected to the other end of the first circuit and the other end of the second circuit. The third end of the third circuit is set as the output terminal;

[0007] The second circuit converts the voltage output by the transformer into a positive voltage for the second circuit and the third circuit, and provides a negative voltage for the second circuit. The first circuit supplies voltage to the third circuit only when the device is turned off. The capacitance value in the first circuit is smaller than the capacitance value in the second circuit;

[0008] The third circuit includes a diode D3, a zener diode DZ1, transistors Q1, Q2 and Q3, resistors R6, R8, R9, and a capacitor C6. One end of the resistor R9, one end of the resistor R6 and the emitter of the transistor Q3 are all connected to the second circuit. The diode D3 is connected in parallel across the resistor R6. The other end of the resistor R6 is respectively connected to the collector of the transistor Q1, the negative electrode of the zener diode DZ1 and one end of the capacitor C6. The base and emitter of the transistor Q1 are both connected to the first circuit. The positive electrode of the zener diode DZ1 is respectively connected to the base of the transistor Q2. The other end of the resistor R9 is respectively connected to the base of the transistor Q3. The collector of the transistor Q2 is connected to the other end of the resistor R9. The collector of the transistor Q3 is connected to the negative electrode of the zener diode DZ2. One end of the zener diode DZ2 is connected to the output terminal. The emitter of the transistor Q1, the other end of the capacitor C6, the emitter of the transistor Q2 and the positive electrode of the zener diode DZ2 are all grounded.

[0009] In the above circuit, when the audio is powered on, the transformer is connected to the second circuit, thereby conducting the second circuit, enabling the second circuit to output a +31V voltage to the third circuit. At this time, the first circuit connected to the transformer cannot output a normal voltage to the third circuit. The output voltage of the second circuit charges the capacitor C6 after passing through the resistor R6 in the third circuit. After the voltage of the capacitor C6 reaches 7.5V, the zener diode DZ1 connected to the capacitor C6 is reversely conducted, thereby enabling the triode Q2 to conduct. After the triode Q2 conducts, the output voltage of the second circuit is connected to the base of the triode Q3 after passing through the resistor R9, enabling the triode Q3 to conduct. After the triode Q3 conducts, a high level is output to the output terminal through the resistor R10, thereby enabling the audio to start working normally; when the audio is powered off, the transformer cannot output voltage to the first circuit and the second circuit. At this time, the diode D1 in the first circuit and the diodes VD1 and VD2 in the second circuit cannot conduct. The capacitors in the first circuit and the second circuit start to discharge to the third circuit. Since the total capacitance in the second circuit is greater than the total capacitance in the first circuit, the discharge of the second circuit is relatively slow compared to the first circuit, while the capacitor in the first circuit quickly completes the discharge, enabling the triode Q1 connected to the first circuit to conduct. After the triode Q1 conducts, the capacitor C6 discharges through the triode Q1. At the same time, the discharge voltage output from the second circuit to the third circuit, after passing through the resistor R6, directly discharges to the ground due to the conduction of the triode Q1 and no longer charges the capacitor C6, thereby enabling the triode Q2 to cut off. After the triode Q2 cuts off, the resistors R8 and R9 connected to the triode Q2 cannot conduct, thereby enabling the triode Q3 to cut off. Finally, the output terminal connected to the triode Q3 outputs a low level, the audio is turned off, enabling the entire circuit to have no impact sound output, completing the shutdown, thereby effectively preventing the impact sound emitted by the speaker during the shutdown process, achieving fast muting. Since it fully considers the discharge of capacitors in multiple circuits, it realizes fast muting by making full use of the discharge of capacitors in multiple circuits, and has good reliability.

[0010] Further, the third circuit further includes resistors R7, R8, R9, R11 and capacitors C7, diode D3. One end of the resistor R7 is connected to the base of the triode Q2. Both ends of the resistor R8 are respectively connected to the other end of the resistor R9 and the collector of the triode Q2. The other end of the capacitor C7 and the other end of the resistor R8, one end of the capacitor C7 is connected to one end of the resistor R9. The collector of the triode Q3 is connected to one end of the resistor R10. The other end of the resistor R8 and the negative electrode of the zener diode DZ2 are both connected to the output terminal. A resistor R11 is connected in parallel across both ends of the zener diode DZ2. The other end of the resistor R7 is grounded. Both ends of the diode D3 are respectively connected to both ends of the resistor R6.

[0011] With the above settings, by setting resistor R8 at the base of triode Q3 and resistor R10 at the collector, the stability of the base of triode Q3 is ensured. By setting capacitor C7, resistor R9 and capacitor C7 form a filter circuit to ensure the stability of the input. Resistor R11 is set at both ends of zener diode DZ2 to ensure the stability of the output voltage.

[0012] Further, the first circuit includes capacitor C1, diodes D2 and D1, resistor R2, resistor R4, and resistor R1. The negative electrode of diode D1 is connected to the output terminal of the transformer. The positive electrode of diode D1 is respectively connected to one end of capacitor C1, one end of resistor R1, and one end of resistor R2. The other end of capacitor C1 and the other end of resistor R1 are both grounded. The other end of resistor R2 is respectively connected to one end of resistor R3 and the positive electrode of diode D2. The negative electrode of diode D2 is connected to one end of resistor R4. The other end of resistor R4 is connected to the base of triode Q1. Both ends of resistor R5 are respectively connected between the base and the emitter of triode Q1.

[0013] With the above settings, after the first circuit is connected to the output terminal of the transformer, the first circuit cannot output a normal voltage to the third circuit, and only the capacitor C1 in the first circuit can be charged through the transformer.

[0014] Further, the second circuit includes diodes VD1, VD2, VD3, and VD4, and capacitors C2, C3, C4, and C5. One end of diode VD1 is connected to the output terminal of the transformer. One end of diode VD2 is connected to the output terminal of the transformer. The negative electrodes after the parallel connection of the two diodes VD1 are respectively connected to one end of capacitor C3, one end of capacitor C5, and the other end of resistor R3. The negative electrodes after the parallel connection of the two diodes VD2 are respectively connected to the output terminal of the transformer. The positive electrodes after the parallel connection of the two diodes VD2 are respectively connected to one end of capacitor C2 and one end of capacitor C4. The other ends of capacitor C3, capacitor C5, capacitor C2, and capacitor C4 are all grounded.

[0015] With the above settings, after the second circuit is connected to the output terminal of the transformer, diode VD1 is turned on, and a +31V voltage is output to the third circuit, and capacitors C3 and C5 are charged at the same time. Diode VD2 is reversely connected. After diode VD2 is turned on, only capacitors C2 and C4 can be charged, and a normal voltage cannot be output to the first circuit through resistor R3, thereby turning on triode Q1 in the third circuit.

[0016] Further, the positive electrodes after the parallel connection of the two diodes VD1 are also connected to one end of resistor R9, one end of capacitor C7, one end of resistor R6, and the emitter of triode Q3.

[0017] The above settings facilitate directly inputting a +31V voltage to the input end of the third circuit after the diode VD1 conducts.

[0018] Furthermore, both the triode Q1 and the triode Q2 are NPN-type triodes, and the triode Q3 is a PNP-type triode.

[0019] With the above settings, during the shutdown process, after the triode Q1 conducts, the capacitor C6 can be discharged, thereby causing the triode Q2 to cut off, and then causing the triode Q3 to cut off.

[0020] Furthermore, the resistor R6 is a current-limiting resistor.

[0021] With the above settings, during the startup process, the current flowing through the resistor R6 is restricted, thereby preventing the charging current of the capacitor C6 connected to the resistor R6 from being too high. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic circuit connection diagram of the present invention.

[0023] Figure 2 is a schematic circuit connection diagram of the first circuit in the present invention.

[0024] Figure 3 is a schematic circuit connection diagram of the second circuit in the present invention.

[0025] Figure 4 is a schematic circuit connection diagram of the third circuit in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0027] As Figures 1-4 shown, a protection circuit for fast shutdown, mute, and anti-shock includes a transformer 4, a first circuit 1, a second circuit 2, and a third circuit 3. The first circuit 1 is connected to the second circuit 2 through a resistor R3. The output end of the transformer 4 is respectively connected to one end of the first circuit 1 and one end of the second circuit 2. Both ends of the third circuit 3 are respectively connected to the other end of the first circuit 1 and the other end of the second circuit 2. The third end of the third circuit 3 is set as the output end MUTE OUT.

[0028] As Figure 2As shown, the first circuit 1 includes a capacitor C1, diodes D2 and D1, a resistor R2, a resistor R4, and a resistor R1. The negative electrode of the diode D1 is connected to the output terminal pin 10 of the transformer. The positive electrode of the diode D1 is respectively connected to one end of the capacitor C1, one end of the resistor R1, and the negative voltage in the second circuit. The negative voltage is connected to one end of the resistor R2. The other end of the capacitor C1 and the other end of the resistor R1 are both grounded. The other end of the resistor R2 is respectively connected to one end of the resistor R3 and the positive electrode of the diode D2. The negative electrode of the diode D2 is connected to one end of the resistor R4. The other end of the resistor R4 is connected to the base of the triode Q1. Both ends of the resistor R5 are respectively connected between the base and the emitter of the triode Q1. Thus, after the first circuit 1 is connected to the output terminal of the transformer 4, since the negative electrode of the diode D1 is connected to the output terminal of the transformer, the output of the transformer 4 cannot enter the first circuit 1. When the second circuit provides a positive voltage, the positive electrode of the diode D2 becomes a negative voltage due to the voltage division on the resistor R2, so the diode cannot conduct, and thus the first circuit 1 cannot output a normal voltage to the third circuit 3. Only the capacitor C1 in the first circuit 1 can be charged through the transformer 4.

[0029] As Figure 3As shown, the second circuit 2 includes diodes VD1, VD2, VD3, and VD4, and capacitors C2, C3, C4, and C5. One end of diode VD1 is connected to the output terminal 10 of the transformer, and one end of diode VD2 is connected to the output terminal 12 of the transformer. In this embodiment, after the other end of diode D1 is connected to the other end of diode VD2, it is connected to one end of resistor R9, one end of capacitor C7, one end of resistor R6, and the emitter of triode Q3 in the third circuit 3, and is also connected to one end of capacitor C3, one end of capacitor C5, and the other end of resistor R3 in the first circuit 1. One end of diode VD3 and one end of diode VD4 are respectively connected to the output terminal pins 11 and 12 of the transformer. After the other ends of diode VD3 and diode VD4 are connected, they are respectively connected to one end of capacitor C2 and one end of capacitor C4. The other ends of capacitor C3, capacitor C5, capacitor C2, and capacitor C4 are all grounded. In this embodiment, the other ends of diodes VD1 and VD2 are the negative poles, capacitors C3 and C2 are polarized capacitors, and one end of capacitor C3 is the positive pole, and one end of capacitor C2 is the positive pole. The other ends of diodes VD3 and VD4 are the positive poles. After the second circuit 2 is connected to the output terminal of the transformer 4, diodes VD1 and VD2 are turned on, and then after rectification and filtering through capacitors C3 and C5, a +31V voltage is output to the third circuit 3, and at the same time, capacitors C3 and C5 are charged. Thus, one end of capacitor C3 is the positive pole, and thus a voltage can be output to the first circuit 1 through resistor R3. However, diode VD2 is reversely connected. After diode VD2 is turned on, only capacitors C2 and C4 can be charged, and a normal voltage cannot be output to the first circuit 1 through resistor R3, and then triode Q1 in the third circuit 3 is turned on.

[0030] In this embodiment, the total capacitance of capacitors C2, C3, C4, and C5 in the second circuit 2 is greater than the capacitance of capacitor C1 in the first circuit 1.

[0031] As Figure 4As shown, the third circuit 3 includes a diode D3 and voltage stabilizing diodes DZ1, DZ2, resistors R8, R9, R10, capacitors C6, C7, and transistors Q1, Q2, Q3. One end of resistor R9, one end of capacitor C7, one end of resistor R6, and the emitter of transistor Q3 are all connected to the second circuit 2. Diode D3 is connected in parallel across resistor R6. The other end of resistor R6 is respectively connected to the collector of transistor Q1, the negative electrode of voltage stabilizing diode DZ1, and one end of capacitor C6. The base of transistor Q1 is connected to the first circuit. The emitter of transistor Q1 is on the one hand connected to the first circuit 1 through resistor R5. The positive electrode of voltage stabilizing diode DZ1 is respectively connected to the base of transistor Q2 and one end of resistor R7. The other end of resistor R9 is respectively connected to the base of transistor Q3 and one end of resistor R8. The collector of transistor Q2 is respectively connected to the other end of capacitor C7 and the other end of resistor R8. The emitter of transistor Q3 is connected to one end of resistor R10. The other end of resistor R10 and the negative electrode of voltage stabilizing diode DZ2 are both connected to the output terminal. A resistor R11 is connected in parallel across voltage stabilizing diode DZ2. The emitter of transistor Q1, the other end of capacitor C6, the other end of resistor R7, the emitter of transistor Q2, and the positive electrode of voltage stabilizing diode DZ2 are all grounded.

[0032] The working principle of this circuit is as follows: When the audio is powered on, the transformer 4 outputs alternating current. During the positive cycle, it makes the diodes VD1 and VD2 in the second circuit 2 conduct. Then, after filtering through capacitors C3 and C5, the second circuit 2 outputs a +31V voltage to the third circuit 3. At this time, for the first circuit 1 connected to the transformer 4, the negative pole of the diode D1 in the first circuit 1 is connected to the positive output terminal of the transformer 4, so that the second circuit provides positive and negative voltages to the first circuit. Then, voltage division is carried out by resistors R3 and R2. Since one end of the resistor R2 is connected to a negative voltage, one end of the resistor R2 is at a negative voltage, so the diode D2 cannot conduct, and thus cannot output a normal voltage to the third circuit 3. The output voltage of the second circuit 2 charges the capacitor C6 after passing through the resistor R6 in the third circuit 3. When the voltage of the capacitor C6 reaches 7.5V, a small current exists at the negative end of the zener diode DZ1, which makes the zener diode DZ1 conduct in reverse, and then makes the triode Q2 conduct. After the triode Q2 conducts, the output voltage of the second circuit 2 is connected to the base of the triode Q3 through the resistor R9, making the triode Q3 conduct. After the triode Q3 conducts, a high level is output to the output terminal MUTE OUT through the resistor R10, so that the audio starts to work normally; When the audio is powered off, the transformer 4 cannot output voltage to the first circuit 1 and the second circuit 2. At this time, the diode D1 in the first circuit 1 and the diodes VD1, VD2, VD3, and VD4 in the second circuit 2 cannot conduct. The capacitors in the first circuit 1 and the second circuit 2 start to discharge to the third circuit 3. Since the total capacitance in the second circuit 2 is greater than that in the first circuit 1, the discharge of the second circuit is slower than that of the first circuit, while the capacitor in the first circuit quickly completes the discharge. The capacitor C1 in the first circuit discharges, making the voltage drop of the negative voltage zero. However, the capacitor in the second circuit discharges for a long time, so that there is current in the diode D2, making the diode D2 conduct, and making the triode Q1 connected to the first circuit 1 conduct. After the triode Q1 conducts, the capacitor C6 discharges through the triode Q1. At the same time, the discharge voltage output from the second circuit 2 to the third circuit 3, after passing through the resistor R6, directly discharges to the ground due to the conduction of the triode Q1 and no longer charges the capacitor C6, so that the triode Q2 is cut off. After the triode Q2 is cut off, the resistors R8 and R9 connected to the triode Q2 cannot conduct, so that the triode Q3 is cut off. Finally, the output terminal MUTE OUT connected to the triode Q3 outputs a low level, and the audio is turned off, so that there is no impact sound output in the whole circuit, completing the shutdown, effectively preventing the impact sound emitted by the speaker during the shutdown process, and realizing fast muting.

Claims

1. A protection circuit for fast shutdown mute and anti-shock, comprising a transformer, a first circuit, a second circuit and a third circuit. The first circuit is connected to the second circuit through a resistor R3. The output terminals of the transformer are respectively connected to one end of the first circuit and one end of the second circuit. The two ends of the third circuit are respectively connected to the other end of the first circuit and the other end of the second circuit. The third end of the third circuit is set as the output terminal; characterized in that: The second circuit converts the voltage output by the transformer into a positive voltage for the second circuit and the third circuit, and provides a negative voltage for the second circuit. The first circuit supplies voltage to the third circuit only when the device is shut down, and the capacitance value in the first circuit is smaller than the capacitance value in the second circuit; The third circuit includes a diode D3 and a zener diode DZ1, transistors Q1, Q2 and Q3, resistors R6, R8, R9, and a capacitor C6. One end of resistor R9, one end of resistor R6 and the emitter of transistor Q3 are all connected to the second circuit. Diode D3 is connected in parallel across resistor R6. The other end of resistor R6 is respectively connected to the collector of transistor Q1, the negative electrode of zener diode DZ1 and one end of capacitor C6. The base and emitter of transistor Q1 are both connected to the first circuit. The positive electrode of zener diode DZ1 is respectively connected to the base of transistor Q2. The other end of resistor R9 is respectively connected to the base of transistor Q3. The collector of transistor Q2 is connected to the other end of resistor R9. The collector of transistor Q3 is connected to the negative electrode of zener diode DZ2. One end of zener diode DZ2 is connected to the output terminal. The emitter of transistor Q1, the other end of capacitor C6, the emitter of transistor Q2 and the positive electrode of zener diode DZ2 are all grounded.

2. The protection circuit for quick shutdown, silent operation and shock prevention according to claim 1, characterized in that: The third circuit further includes resistors R7, R8, R9, R11 and a capacitor C7, a diode D3. One end of resistor R7 is connected to the base of transistor Q2. The two ends of resistor R8 are respectively connected to the other end of resistor R9 and the collector of transistor Q2. The other end of capacitor C7 and the other end of resistor R8, one end of capacitor C7 is connected to one end of resistor R9. The collector of transistor Q3 is connected to one end of resistor R10. The other end of resistor R8 and the negative electrode of zener diode DZ2 are both connected to the output terminal. A resistor R11 is connected in parallel across the two ends of zener diode DZ2. The other end of resistor R7 is grounded. The two ends of diode D3 are respectively connected to the two ends of resistor R6.

3. The protection circuit for quick shutdown, silent mode, and anti-shock according to claim 1, wherein: The first circuit includes a capacitor C1 and diodes D2 and D1, resistors R2, R4, R1. The negative electrode of diode D1 is connected to the output terminal of the transformer. The positive electrode of diode D1 is respectively connected to one end of capacitor C1, one end of resistor R1 and one end of resistor R2. The other end of capacitor C1 and the other end of resistor R1 are both grounded. The other end of resistor R2 is respectively connected to one end of resistor R3 and the positive electrode of diode D2. The negative electrode of diode D2 is connected to one end of resistor R4. The other end of resistor R4 is connected to the base of transistor Q1. The two ends of resistor R5 are respectively connected between the base and emitter of transistor Q1.

4. The protection circuit for quick shutdown, silent operation and shock prevention according to claim 1, characterized in that: The second circuit includes diodes VD1, VD2, VD3 and VD4 and capacitors C2, C3, C4, C5. One end of diode VD1 is connected to the output terminal of the transformer, and one end of diode VD2 is connected to the output terminal of the transformer. The negative electrodes after the parallel connection of the two diodes VD1 are respectively connected to one end of capacitor C3, one end of capacitor C5 and the other end of resistor R3. The negative electrodes after the parallel connection of the two diodes VD2 are respectively connected to the output terminal of the transformer. The positive electrodes after the parallel connection of the two diodes VD2 are respectively connected to one end of capacitor C2 and one end of capacitor C4. The other ends of capacitor C3, capacitor C5, capacitor C2 and capacitor C4 are all grounded.

5. The protection circuit for fast shutdown, silent operation and shock prevention according to claim 4, characterized in that: The positive electrode after the parallel connection of the two diodes VD1 is further connected to one end of resistor R9, one end of capacitor C7, one end of resistor R6 and the emitter of triode Q3.

6. The protection circuit for fast shutdown, silent operation and shock prevention according to claim 1, characterized in that: Both the triode Q1 and the triode Q2 are NPN-type triodes, and the triode Q3 is a PNP-type triode.

7. A protection circuit for quick shutdown, silent operation, and shock prevention according to claim 1, characterized in that: The resistor R6 is a current-limiting resistor.

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