[0021] Embodiment 1, this embodiment proposes a loudspeaker protection circuit, such as figure 1 As shown, it includes a first switch and a second switch respectively connected to the two-way differential audio signal lines of the loudspeaker, and also includes a comparison circuit for comparing whether the two-way signals of the two-way differential audio signals are the same, and the same as the A switch control circuit connected to the comparison circuit, the comparison circuit sends a comparison signal to the switch control circuit, and the switch control circuit generates a control signal for controlling the conduction states of the first switch and the second switch according to the comparison signal and sent to the first switch and the second switch. In the speaker protection circuit of the present invention, by setting the first switch and the second switch on the differential audio signal transmission line of the speaker, a control command for controlling the first switch and the second switch is generated according to whether the two signals of the differential audio signal are the same, Furthermore, when the two signals are different, the transmission line of the differential audio signal can be disconnected, so as to protect the speaker and prevent it from being burned.
[0022] As a preferred embodiment, in this embodiment, as figure 2 As shown, the first switch includes a first PMOS transistor Q1, the second switch includes a second PMOS transistor Q2, and the source of the first PMOS transistor Q1 and the source of the second PMOS transistor Q2 are respectively connected to the On the two-way speaker differential audio signal line, the two-way signal speaker+ and speaker- of the differential audio signal are received, and the drain of the first PMOS tube and the drain of the second PMOS tube are respectively connected to the two-way differential audio of the speaker. The signal input terminals in- and in+ are connected in one-to-one correspondence, and one of the gates of the first PMOS transistor Q1 and the second PMOS transistor Q2 is connected to the switch control circuit to receive the control signal sent by the switch control circuit, The other path is connected to the ground terminal through the second resistor R2. Depend on figure 2 It can be seen from the figure that when the two signals of the differential audio signal are the same, the switch control circuit outputs a low level to the gates of the first PMOS transistor Q1 and the second PMOS transistor Q2, and the first PMOS transistor Q1 and the second PMOS transistor Q2 are turned on. , the differential audio signal transmission line of the speaker is turned on, so the speaker can normally receive the two signals speaker+ and speaker- of the differential audio signal. When the two signals of the differential audio signal are different, the switch control circuit sends the first PMOS tube Q1 The gate of the second PMOS transistor Q2 outputs a high level, and the first PMOS transistor Q1 and the second PMOS transistor Q2 are cut off, so the differential audio signal transmission line of the speaker is disconnected, and the speaker cannot receive the two signals speaker+ and speaker of the differential audio signal -, to protect the speaker and prevent it from being burned.
[0023] In this example, if figure 2As shown, the comparison circuit includes a first comparator U1, a second comparator U2, and an OR gate circuit U3, and the inverting input terminal of the first comparator U1 is connected to one of the differential audio signal transmission lines of the speaker Such as speaker-connection, the non-inverting input terminal of the first comparator U1 is connected with another line of the differential audio signal transmission line of the speaker such as speaker+ through an inverting amplifier U4, and the non-inverting input terminal of the second comparator U2 is connected with The inverting input terminal of the first comparator U1 is connected, the inverting input terminal of the second comparator U2 is connected with the non-inverting input terminal of the first comparator U1, and the output terminal of the first comparator U1 The output terminals of the second comparator U2 are respectively connected to the two input terminals of the OR circuit U3, and the output terminals of the OR circuit U3 are connected to the control signal input terminals of the switch control circuit. Since the phases of the two signals of the differential audio signal are completely opposite, by inverting the phase of one of the signals of the differential audio signal, the two signals input to the first comparator U1 and the second comparator U2 are two signals of the same phase, Since the working principle of the comparator is to output a high level when the input level of the non-inverting input terminal is higher than the input level of the inverting input terminal, and output a low level when the input level of the non-inverting input terminal is lower than or equal to the input level of the inverting input terminal, When the differential audio signal transmission line is normal, the two signals input to the first comparator U1 and the second comparator U2 are the same, and the output terminals of the first comparator U1 and the second comparator U2 output a low level, so or The gate circuit U3 outputs a low level. At this time, the switch control signal outputs a low level to the gates of the first PMOS transistor Q1 and the second PMOS transistor Q2. At this time, the gate of the first PMOS transistor Q1 and the gate of the second PMOS transistor Q2 The gate is connected to the ground terminal through the second resistor R2, and is at low level, so the first PMOS transistor Q1 and the second PMOS transistor Q2 are turned on, and the speaker can normally receive the two signals speaker+ and speaker- of the differential audio signal. When the two signals input to the first comparator U1 or the second comparator U2 are different, the audio signal fails, which is reflected in the fact that the level of one of the two lines of the differential audio signal is higher than the level of the other, Therefore, it must appear that the level of one of the non-inverting input terminals of the first comparator U1 or the second comparator U2 is higher than the level of the inverting input terminal, so one of the comparators must output a high level, so the OR gate circuit U3 outputs At this time, the switch control signal outputs a high level to the gates of the first PMOS transistor Q1 and the second PMOS transistor Q2, so the first PMOS transistor Q1 and the second PMOS transistor Q2 are cut off, and the speaker cannot receive the differential audio signal. Two signals speaker+ and speaker-.
[0024] Alternatively, the inverting amplifier U4 can also be set on the non-inverting input line of the first comparator U1, since the phases of the two signals speaker+ and speaker- of the differential audio signal of the speaker are opposite, it is only necessary to invert any one of them , which can realize that the two signals are exactly the same. For the first comparator U1 and the second comparator U2, it only detects whether the two input signals are the same. Therefore, the inverting amplifier U4 is set in the first comparator U1 The principle of setting it on the line of the non-inverting input end of the first comparator U1 is the same as that of setting it on the line of the inverting input end of the first comparator U1, and has the same effect, so it will not be repeated here.
[0025] In this embodiment, the switch control circuit includes a third NMOS transistor Q3 and a fourth PMOS transistor Q4, the gate of the third NMOS transistor Q3 is connected to the output terminal of the OR circuit U3, and the third The gate of the NMOS transistor Q3 is connected to the cathode of a reverse diode D1, the anode of the reverse diode D1 is connected to the drain of the fourth NMOS transistor, and the reverse diode D1 is used when the OR circuit U3 outputs a high level , to prevent the current from directly flowing from the OR gate circuit U3 to the first PMOS transistor Q1 and the second PMOS transistor Q2, the source of the third NOMS transistor Q3 is connected to the ground terminal, and the drain of the third NMOS transistor Q3 is connected to the The gate of the fourth PMOS transistor Q4 is connected, the source of the fourth PMOS transistor Q4 is connected to a DC power supply, and one of the drains of the fourth PMOS transistor Q4 is connected to the first PMOS transistor Q1 and the second PMOS transistor Q1 respectively. The gate connection of transistor Q2. The working principle of this circuit is that when the two signals input to the first comparator U1 are the same as the two signals of the second comparator U2, the audio signal is normal, and the output terminal of the OR gate circuit U3 outputs a low level. The third NMOS transistor Q3 is turned off, so the gate of the fourth PMOS transistor Q4 is at a high level, and the fourth PMOS transistor Q4 is turned off. At this time, the gate of the first PMOS transistor Q1 and the gate of the second PMOS transistor Q2 pass through the second resistor R2 Connected to the ground terminal, it is low level, so the first PMOS transistor Q1 and the second PMOS transistor Q2 are turned on, and the speaker can normally receive the two signals speaker+ and speaker- of the differential audio signal. When the two-way signals input to the first comparator U1 are different from the two-way signals of the second comparator U2, the audio signal fails, and the output terminal of the OR gate circuit U3 outputs a high level, at this time the third NMOS transistor Q3 is turned on, the fourth PMOS transistor Q4 is turned on, the fourth PMOS transistor Q4 is turned on, and outputs a high level to the gates of the first PMOS transistor Q1 and the second PMOS transistor Q2, so the first PMOS transistor Q1 and the second PMOS transistor When Q2 is off, the speaker cannot receive the two signals speaker+ and speaker- of the differential audio signal. In the speaker protection circuit of this embodiment, if speaker+ is short-circuited to ground, the input of the inverter U1 is 0, and the output is also 0, and Speaker- still has a forward voltage. In this way, there is a difference between the two signals of the first comparator U1 and the input terminal of the second comparator U2, and the output of the OR gate circuit U3 becomes high level, and the first PMOS transistor Q1 and the second PMOS transistor Q2 are cut off, thereby turning off the The driving signal of the loudspeaker prevents the burning of the loudspeaker.
[0026] In this embodiment, it is preferable that the drain of the fourth PMOS transistor Q4 is connected to the gate of the third NMOS transistor Q3 in another way, by connecting the gate of the third NMOS transistor Q3 to the cathode of a reverse diode D1, The anode of the reverse diode D1 is connected to the drain of the fourth PMOS transistor Q4, so once the fourth PMOS transistor Q4 outputs a protection high level to the first PMOS transistor Q1 and the second PMOS transistor Q2 through the drain, at the same time the protection The other high level is output to the third NMOS transistor Q3, which has been supplied to the gate of the third NMOS transistor Q3 with a high level, so the third NMOS transistor Q3 is always turned on, ensuring the control of the first PMOS transistor Q1 and the second PMOS transistor Q2 Continuous disconnection, at this time, the main board circuit needs to be powered again to remove the protection.
