KR20120118992A - Circuit for protecting speaker line of digital audio amplifier - Google Patents

Abstract

PURPOSE: A protecting circuit for a speaker line of a digital audio amplifier is provided to prevent damage to a drive circuit of an audio amplifier by preventing inflow of leakage power with an AC component. CONSTITUTION: A first gate drive circuit part(100) changes an analog audio signal into a digital PWM(Pulse Width Modulation) signal. A phase inversion circuit part(150) generates an inverted analog audio signal by phase-inverting the analog audio signal. A second gate drive circuit part(100') changes the inverted analog audio signal into the inverted digital PWM signal. A first switching part(200) is switched by the digital PWM signal. A second switching part(200') is switched by the inverted digital PWM signal. An output circuit part(300) outputs an output signal through a speaker line. An over current detecting circuit part detects a switch on-resistance value of the first and second switching part. [Reference numerals] (100) First gate drive circuit part; (100') Second gate drive circuit part

Description

Speaker line protection circuit of digital audio amplifier {CIRCUIT FOR PROTECTING SPEAKER LINE OF DIGITAL AUDIO AMPLIFIER}

The present invention relates to a loudspeaker line protection circuit of a digital audio amplifier, and more particularly, to a driving circuit by preventing an overcurrent caused by a short circuit of an internal circuit or a short circuit of an AC component in a loudspeaker line which is an output terminal of a class D digital audio amplifier. The present invention relates to a speaker line protection circuit of a digital audio amplifier, which can prevent breakage of the circuit.

In general, audio output amplifiers for converting and outputting an audio signal digitally are classified into Class-A, Class B, Class AB, and Class-D types according to their types.

For example, in the case of the Class-AB type audio output amplifier, the audio signal outputted from the amplifier is fed back and signal compensation is performed for the output variation. Since the audio amplifier takes the difference between the voltage and the output voltage, the signal loss is large.

In contrast, the Class-D type audio output amplifier is a digital amplifier that converts an input signal into a pulse width modulation (PWM) signal, which makes signal amplification easier than other amplifiers. It is mainly used because of its good efficiency.

That is, as shown in Figure 1, a conventional Class-D type digital (PWM) audio amplifier converts an analog signal into a PWM signal having a corresponding pulse width, but through a switching driver (switching driver) Analog output waveforms generated as shown in FIG. 2 by switching the switching FETs at intervals corresponding to the pulse widths according to the statically amplified PWM signals and passing the amplified PWM waveforms through a low pass filter (LPF). By converting to a digital audio signal, the analog audio signal is finally obtained.

However, in the conventional digital audio amplifier as described above, the driving circuit of the audio amplifier is generated because an overcurrent occurs due to a short to ground at the output line, a short between the + and-ends of the speaker, or a leakage current of AC component. There is a problem that breaks.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to prevent damage to a driving circuit of an audio amplifier in advance by preventing an overcurrent caused by a short circuit of an internal circuit or a short circuit in a speaker line which is an output terminal of a digital audio amplifier. It is to provide a speaker line protection circuit of a digital audio amplifier which can be prevented.

The speaker line protection circuit of the digital audio amplifier according to the present invention for achieving the above object, the first gate driving circuit unit 100 for receiving an analog audio signal and converting it into a digital PWM signal, the phase inversion of the analog audio signal A phase inverting circuit unit 150 for generating an inverted analog audio signal and a second gate driving circuit unit 100 for receiving the inverted analog audio signal from the phase inverting circuit unit 150 and converting the inverted digital audio signal into an inverted digital PWM signal. '), The first switching unit 200 switched by the digital PWM signal of the first gate driving circuit unit 100 and the inverted digital PWM signal of the second gate driving circuit unit 100'. Outputs the second switching unit 200 'to be switched and the output signals from the first switching unit 200 and the second switching unit 200' through the speaker line. A circuit for protecting a loudspeaker line of a digital audio amplifier including an output circuit unit 300, which detects switch-on resistance values of the first and second switching units 200 and 200 'and generates an abnormal signal due to overcurrent. And an overcurrent detection circuit unit 400 for stopping the operation of the first and second gate driving circuit units 100 and 100 '.

Preferably, the overcurrent detecting circuit 400 is a high level voltage for detecting a change in the switch-on resistance value when + power (+ VBB) is supplied to the first and second switching units 200 and 200 '. A sensing unit 410 and a low-level voltage sensing unit 420 which senses a change in a switch-on resistance value when a power supply (-VEE) is supplied to the first and second switching units 200 and 200 '. And an operation signal for stopping an operation of the first and second gate driving circuit units 100 and 100 ′ by sending an abnormality detection signal according to the detection of the high level voltage detector 410 and the low level voltage detector 420. It includes a blocking unit 450.

More preferably, the overcurrent detection circuit 400 may detect the abnormal signal through the high level voltage detector 410 and the low level voltage detector 420. And a signal switching unit 430 for immediately stopping the operation of 100 ').

In addition, the overcurrent detection circuit unit 400, when detecting an abnormal signal through the high level voltage detector 410 and the low level voltage detector 420, a warning message notification to issue a warning message through the light emitting diode (LED1) It is preferable to further include a portion 440.

In addition, the output terminals of the first and second switching units 200 and 200 ′ may filter external leakage currents to prevent breakage of the first and second gate driving circuit units 100 and 100 ′. It is preferable that two earth leakage blocking filters 250 and 250 'are connected, respectively.

On the other hand, it is preferable that the limiter circuit 500 is connected to block the supply of more than the reference voltage to the input terminal (INT) of the digital audio amplifier.

Preferably, the limiter circuit unit 500 distributes the voltage through distribution resistors R8 and R9 connected in series when a voltage equal to or greater than a reference voltage is input, and through a capacitor C5 connected between the distribution resistors R8 and R9. The DC component is removed and full-wave rectified by the capacitor C4 grounded by the diode D3 and the cathode of the diode D3, the anode and the cathode of which are sequentially connected to the capacitor C. After the conversion, a bias voltage is supplied to a transistor Q3 having a base connected to the cathode of the diode D3 to turn on the transistor Q3, and at the same time, an operating voltage is supplied to the laser diode resistor LDR1 so that an output voltage is increased. It is configured to prevent the supply above the reference input voltage.

According to the loudspeaker line protection circuit of the digital audio amplifier according to the present invention, by providing a limiter circuit portion at the input terminal of the amplifier driving circuit and an overcurrent detecting circuit portion at one side of the driving circuit, a short from the speaker line to ground or a speaker There is an advantage in that it is possible to prevent the occurrence of overcurrent by short between both ends of + and-to prevent damage to the driving circuit of the audio amplifier.

In addition, by providing a CR filter at the output terminal of the amplifier driving circuit, it is possible to block the leakage current of the AC component to prevent damage to the driving circuit of the audio amplifier.

Other objects and advantages of the present invention in addition to the above object will be apparent from the detailed description of the embodiments with reference to the accompanying drawings.

1 is a circuit diagram schematically showing a conventional class D type digital audio amplifier.
FIG. 2 is a diagram illustrating a switching waveform of the class D amplifier of FIG. 1 and an output waveform obtained by filtering the same. FIG.
3 is a conceptual diagram of a digital audio amplifier of an embodiment applied to the present invention.
4 is a schematic circuit diagram of a digital audio amplifier to which an earth leakage blocking filter 250 or 250 ′, which is a CR filter, according to an embodiment of the present invention is applied.
FIG. 5 is a detailed circuit diagram of the first gate driving circuit unit 100 of FIG. 4.
FIG. 6 is a detailed circuit diagram of the second gate driving circuit part 100 ′ of FIG. 4.
7 is a detailed circuit diagram of the phase inversion circuit unit 150 of FIG.
8 is a detailed circuit diagram of an overcurrent detection circuit 400 according to an embodiment of the present invention.
9 is a detailed circuit diagram of the limiter circuit unit 500 according to an embodiment of the present invention.

Hereinafter, a speaker line protection circuit of a digital audio amplifier according to the present invention will be described in detail with reference to the accompanying drawings.

For reference, Patent No. 10-993788 (Digital Audio Amplification Circuit), filed and registered by the present applicant, is referred to herein.

First, it should be noted that, in the drawings, the same components or parts have the same reference numerals as much as possible. In addition, in describing the present invention, a detailed description of related known functions or configurations will be omitted in order not to obscure the subject matter of the present invention.

3 is a conceptual diagram of a digital audio amplifier of an embodiment applied to the present invention, and FIG. 4 is a schematic circuit diagram of a digital audio amplifier to which a CR filter according to an embodiment of the present invention is applied.

5 is a detailed circuit diagram of the first gate driver circuit part 100 of FIG. 4, FIG. 6 is a detailed circuit diagram of the second gate driver circuit part 100 ′ of FIG. 4, and FIG. 7 is a phase inversion circuit part of FIG. 4. Detailed circuit diagram of 150 is shown.

First, as shown in FIG. 3, in the digital audio amplifier according to the present invention, the PWM signal is amplified in the first gate driving circuit unit 100 by the switching FET1 and FET2 of the first switching unit 200. The first low pass filter 240, which is an LC low pass filter including the first inductor L1 and the first capacitor C8, is converted into an analog signal and outputted through a speaker of the output circuit unit 300. .

On the other hand, the PWM signal is converted into a PWM signal inverted by the phase inversion circuit unit 150, the inverted PWM signal is switched FET4 of the second switching unit 200 'in the second gate driving circuit unit 100'. And converted into an analog signal by the second low pass filter 240 ', which is an LC low pass filter composed of the second inductor L2 and the second capacitor C17, and amplified while being switched by the FET5. It is also output through the speaker.

Here, the above configuration will be described in detail with reference to FIGS. 4 to 7.

First, an analog output is input to the input terminal INT of FIG. 4, which is first pulse-code-modulated (PCM) through the first gate driving IC (110 of FIG. 5) of the first gate driving circuit unit 100. By way of example, it is converted into a PWM signal of 384 kHz + 6V, which turns ON / OFF the switching FET1 and FET2 of the first switching unit 200.

At this time, the resistor R2 (R2 in Fig. 5) is a device for adjusting gain, and the rest are peripheral elements of the first gate driving IC.

Now, the PWM signal amplified at 384 kHz + 85V while being switched by the switching FET1 and FET2 of the first switching unit 200 is, for example, a first surge compensation circuit unit of an RC series circuit connected in parallel with the FET1 and FET2 ( The surge signal is compensated by the 220, and is output through the contact point X. For example, the first low pass filter 240, which is an LC low pass filter including the inductor L1 and the capacitor C8 of FIG. The signal is converted into an analog signal of + 50V and output through the speaker of the output circuit unit 400 through the first snubber circuit unit 260.

On the other hand, a phase inversion circuit unit 150 for inverting the phase of the input audio signal is connected to the input terminal INT of FIG. 4. A detailed circuit of the phase inversion circuit unit 150 is shown in FIG. The signal OUT is input to the second gate driving circuit unit 100 ′ of FIG. 4.

The inverted analog signal is also converted into a PWM signal of 384 kHz -6V by the pulse-code-modulation (PCM) method through the second gate driving IC (110 'of FIG. 6) of the second gate driving circuit unit 100'. The inverted PWM signal turns on / off the switching FET4 and FET5 of the second switching unit 200 '.

Also at this time, the resistor R2 (R2 in Fig. 6) is a device for adjusting gain, and the rest are peripheral elements of the second gate driving IC.

Also, the PWM signal amplified at 384 kHz -85V while being switched by the switching FETs 4 and FET 5 of the second switching unit 200 ′ is a second surge compensation circuit unit of an RC series circuit connected in parallel with the FET 4 and FET 5. By the second low pass filter 240 ', which is an LC low pass filter composed of the inductor L2 and the capacitor C17 of FIG. For example, it is converted into an analog signal of 20 kHz -50 V, and is output through the speaker of the output circuit unit 300 through the second snubber circuit unit 260 '. The final output audio signal is an audible frequency of 20 Hz to 20 kHz. An example is an audio signal amplified with a signal-to-noise ratio of 100-105 dBm.

At this time, as shown in Figure 4, the output terminal of the first and second low pass filter unit 240 and 240 ′, the first and second ground fault interrupting filter 250 and 250 which is a CR filter according to an embodiment of the present invention ') Is installed to prevent breakage of the first and second gate driving circuit parts 100 and 100' due to an external leakage current.

That is, when the leakage current flows into the digital audio amplifier applied to the present invention, since the PWM switching carrier frequency 384 kHz is AC, when the leakage current is shorted with the AC, the AC and the large potential AC collide with each other to generate a potential The high leakage current flows into the loudspeaker output line, and the first and second gate driving circuit units 100 and 100 'are destroyed. Therefore, in order to prevent this, the first and second ground fault interrupting filters 250 and 250 ′, which are CR filters, are installed so that the output energy of the audio amplifier is transmitted to the output line of the speaker, and the ground fault component from the outside is audio. It blocks the inflow into the amplifier.

Specifically, the PWM switching output charges the capacitors C22H and C23L of the first and second short-circuit cutoff filters 250 and 250 'to the + (high) potential and discharges them to the-(low) potential to output the speaker. While allowing output energy to be delivered to the line side, no charge is delivered to the audio amplifier even though AC leakage current flows into the-(low) potential through the speaker lines of the capacitors C22H and C23L. At this time, the charge is changed from the + (high) potential to the-(low) potential, and the discharge is reversed.

On the other hand, the resistors R50H and R51L of the first and second short circuit breaker filters 250 and 250 'perform two functions. First, a PWM switching output is charged with the capacitors C22H and C23L. Since the discharge capacity is too low, the output impedance of the audio amplifier is low when the resistance capacitance value is too low. Therefore, even if the resistance capacitance value is high, the discharge potential of the capacitors C22H and C23L is high. Second, the ground (GND) because the AC component is the-(low) potential of the capacitors (C22H and C23L) through the speaker line when an AC leakage current is introduced into the audio amplifier. Bypasses the function.

For reference, the first and second gate driving circuit units 100 and 100 ′ shown in FIG. 4 are shown in FIGS. 5 and 6, respectively, and the first and second gate driving ICs 110 and 110 ′ are shown in FIG. 5 and 6, the digital audio amplifier can directly drive the power MOSFET of the class D output stage with a pulse width modulation (PWM) signal having an amplitude of 3 to 5V. The PWM signal must be amplified or timing adjusted.

That is, the first and second gate driving ICs 110 and 110 ′ respectively modulate an analog audio signal into a digital PWM signal and output a reference potential of the modulated digital PWM signal to the output terminal of the output terminal (Vs of FIG. 4). ), A dead time generating circuit 113 for generating a dead time for generating a delay when the PWM input signal rises, and a first and second switching unit 200 and 200 '. A gate driver 114 for switching the FETs of the FET, and a protection control circuit unit for controlling the operation of the entire audio amplifier by stopping the shift operation of the modulation and level shifter 112 when an abnormal signal is detected by the limiter circuit unit and the overcurrent detection circuit unit 115, a bootstrap circuit (e.g., D3, R5, C10 in FIG. 5), a comparator 111, and the like.

That is, the digital audio amplifying circuit of one embodiment applied to the present invention is a BTL full bridge type PWM signal switching voltage high efficiency SMPS supply step-up amplification driving circuit, and the FET at the output of the class D digital audio amplifying circuit operates like an ON / OFF switch. The pulsed input signal is applied to the gate and the output current increases from 0A to the maximum value (V _BB /RL).When switched on, the maximum current passes through the MOSFET, but the resistance value between the drain and source is very high. The loss is zero in principle, and the loss is zero because no current flows when the switch is turned off. Thus, the loss is very small and high amplification can be achieved even at a small voltage.

On the other hand, the overcurrent detection circuit 400 according to an embodiment of the present invention connected to the digital audio amplifier configured as described above will be described with reference to FIG.

FIG. 8 is a detailed circuit diagram of the overcurrent detection circuit unit 400 according to an embodiment of the present invention. The first gate driving circuit unit 100 (refer to FIG. 5) and the second gate driving circuit unit 100 ′ of the audio amplifier of FIG. 6 is connected to one side.

First, the overcurrent detection circuit 400 according to an embodiment of the present invention includes a short to ground in a speaker line, which is an output terminal of the audio amplifier of FIG. 4, a short between + and − ends of a speaker, or an AC electric leakage component. When is inflowed, an overcurrent flows between the drain D and the source S of the switching FETs of the first and second switching units 200 and 200 ', and is destroyed. And stops the operation of the second gate driving circuit units 100 and 100 'to protect the entire circuit.

That is, the overcurrent detecting circuit 400 detects a switch-on resistance value between the drain D and the source S of the switching FETs of the first and second switching units 200 and 200 ′, and thus, the short and ground fault electric When an abnormal signal such as inflow is detected, the operation of the audio amplifier is stopped by stopping the PWM modulation of the first and second gate driving ICs 110 and 110 ', and resuming the operation of the audio amplifier in a normal state. 8, the high level voltage detector 410, the low level voltage detector 420, the signal switch 430, the warning message notifier 440, and the operation signal cutoff unit. It consists of 450.

Here, the high level voltage detector 410 is a means for detecting a change in the value of the switch-on resistance as a voltage applied to the drain (D) of the switching FET of the switching unit 200 and 200 'by the power supply (+ VBB). to be.

That is, since the switch-on resistance value is several tens of mΩ, if an overcurrent flows between the drain D and the source S of the FET, the switch-on resistance value is destroyed, when the switch-on resistance value becomes small. Since the voltage applied to the drain D of the FET is momentarily lowered to a very small voltage, the high-level voltage detector 410 compensates for the small voltage to increase the sensed voltage. It is an amplification circuit.

In detail, the high level voltage detector 410 drops a large voltage of + VBB applied through the high input terminal FET-H from the drain D of the FET through the zener diode D13H. The bias voltage of the transistor Q21 having a base connected between the resistors R43 and R44 is set through the divided voltages of the resistors R43 and R44 connected in series with the anode of the zener diode D13H.

In this case, the amplification gain G of the transistor Q21 is determined as the division (G = R39 / R40) of the resistors R39 and R40 connected to the collector and emitter of the transistor Q21, respectively. The bias current compensation of Q21 is made through a resistor R41 connected to the base and the collector and a resistor R42 connected to the base and the ground.

Subsequently, the low level voltage sensing unit 420 means for detecting a change in the value of the switch-on resistance as a voltage applied to the source S of the switching FET of the switching units 200 and 200 'by the power supply (-VEE). to be.

That is, since the switch-on resistance value is several tens of mΩ, if an overcurrent flows between the drain D and the source S of the FET, the switch-on resistance value is destroyed, when the switch-on resistance value becomes small. Since the voltage applied to the source S of the FET is momentarily lowered to a very small voltage, the low-level voltage sensing unit 420 compensates for the small voltage to increase the sensed voltage. It is an amplification circuit.

In detail, the low level voltage detector 420 lowers a large voltage of -VEE applied through the low input terminal FET-L from the source S of the FET through the zener diode D17. -Through the resistor (R36) and the zener diode (D16) connected in parallel to the cathode of the zener diode (D17) to make a potential difference of the voltage to make a voltage to supply a + voltage having a high potential difference, the zener diode (D17) A bias of the transistor Q22 having a base connected to the resistor R34 through a divided voltage of a resistor R34 connected in series with a cathode and resistors R36 and R37 connected to and grounded in series with the resistor R34. Configured to set the voltage.

In this case, the amplification gain G of the transistor Q22 is determined by dividing (G = R45 / R46) of the resistors R45 and R46 connected to the collector and emitter of the transistor Q22, respectively. The bias current compensation of Q22) is made through a resistor R47 connected to the base and the collector and a resistor R48 connected to the base and the ground.

Meanwhile, for example, Zener constant voltage diodes D12 and D14 of 5.1 V are connected to the high level voltage detector 410 and the low level voltage detector 420, respectively. Since the voltage amplification degree of Q21 and transistor Q22 of the low level voltage sensing unit 420 is 5.1V or more, when the switch-on resistance falls due to overcurrent, the sensing voltage distribution value (resistance value set to the division voltage R43, R44, R34, R36, and R37)) cause the Zener constant voltage diodes D12 and D14 to be 5.1V or less, which causes no operation.

Subsequently, the signal switching unit 430 is connected to the anodes of the Zener constant voltage diodes D12 and D14 through the resistors R23 and R33, and the resistors R23 and R33 are connected to the base transistors Q17 and Q19. Is a bias resistor of and is connected between the resistor R23 and the transistor Q17 to ground off the transistors Q17 and Q19 quickly when the switch-on resistance falls, and the time constants R22 and C10 connected to ground. And the time constants R32 and C15 connected between the resistor R33 and the transistor Q19 and grounded.

In this case, if the values of the time constants C10 and C15 are reduced, the potential quickly bypasses to the ground through the resistors R22 and C10 during charging and discharging, and the switching FETs of the first and second switching units 200 and 200 '. Maintains the normal switch-on resistance, the transistors Q17 and Q19 are in an on state because the operating voltages of the Zener constant voltage diodes D12 and D14 are 5.1V or more.

Here, the collector of the transistor Q17 is provided with a PNP transistor Q16A having an emitter connected thereto, and the transistor Q15 having a base connected to the collector of the transistor Q16A is provided, and a PNP transistor Q18A having an emitter connected to the collector of the transistor Q19 is provided. A transistor Q16 having a base connected to the collector of the transistor Q18A is provided so that the transistors Q16A and Q18A supply a smooth bias voltage of the transistors Q14 and Q15. If so, the operating voltages of the Zener constant voltage diodes D12 and D14 are 5.1 V or more, so that the transistors Q17 and Q19 are turned on and the transistors Q14 and Q15 are turned off, and the transistors Q15 and Q14 are turned off. Diodes D10 and D11 respectively connected to the output voltage, so that the output contact (D) It is on.

However, when the switching FET has a low switch-on resistance due to overcurrent, the Zener constant voltage diodes D12 and D14 are not operated because the operating voltage is 5.1 V or less, so that the transistors Q17 and Q19 are off. The transistors Q14 and Q15 are turned on so that the diodes D10 and D11 do not output, so the output contact D is turned off. In this case, the diodes D10 and D11 separately detect the overcurrent inputs of the upper wave and the lower wave of the switching FET.

On the other hand, the warning message notification unit 440 is the protection control circuit 115 and through the output terminal (CSD) when the overcurrent is detected or the first and second gate driving IC (110, 110 ') is abnormal due to external causes 115 ') is an error detection signal and a means of informing a warning message through the light emitting diode LED1.

That is, when the output terminal CSD of the point A is a high signal, the warning message notification unit 440 becomes a signal in phase with the VCC voltages of the source S and the drain D of the FET3 serving as the switching means. Since the low output signal is sent, the transistor Q10 whose base is connected to the gate G of the FET3 is turned off, and the light emitting diode LED1 connected between the FET3 and the transistor Q10 does not operate.

At this time, when the transistor Q10 is off, the transistor Q11 connected to the base of the collector of the transistor Q10 is turned on, and the transistor Q13 connected to the base of the collector of the transistor Q11 is turned off to output an output contact point D of the signal switching unit 430. ) Is off.

In addition, when an overcurrent is detected or the first and second gate driving ICs 110 and 110 ′ become abnormal due to external causes, the output terminal CSD of the A point is the transistor Q20 of the sensing signal transmitter 450 described later. By switching from high to low, the signal becomes in phase with the VCC voltage of the source S and the drain D of the FET3. Therefore, the gate G of the FET3 sends a high output signal, so that the transistor Q10 of the warning message notification unit 440 is turned on to operate the light emitting diode LED1. When the transistor Q10 is turned on, Q11 is off and Q13. Since is turned on, the potential of the output contact (D) of the signal switching unit 430 is bypassed to the ground.

On the other hand, when the overcurrent is detected or the first and second gate driving ICs 110 and 110 'are abnormal due to external causes, the operation signal blocking unit 450 may protect the circuit 115 through the output terminal (CSD). And an abnormality detection signal to 115 " to stop the operation of the first and second gate driving circuit portions 100 and 100 '.

That is, when the overcurrent is detected in the switching FET, the operation signal blocking unit 450 converts the output contact point D of the signal switching unit 430 from high to low state. Since the transistor Q22A connected with the base is on and the transistor Q20 connected with the base is connected to the collector of the transistor Q22A, the output terminal CSD goes from the high state to the low state. Therefore, when the operation signal blocking unit 450 cuts off the signal, since the protection control circuits 115 and 115 'are changed from a high state to a low state, the switching of the first and second switching units 200 and 200' is performed. The FET is stopped.

Briefly describing the operation of the configuration, in the normal operation, the high input terminal (FET-H) of the high-level voltage detector 410 and the low input terminal (FET) of the low-level voltage detector 420 of FIG. AC output is applied, and since Q21 and Q22 of FIG. 8 are 'on', the emitter ground voltage amplifier circuit is amplified to generate an output voltage of 5.1V at D12 and D14.

Then, since Q17 and Q19 of the signal switching unit 430 are 'on' and Q15 and Q14 are 'off', D10 and D11 are operated so that the output contact D is 'on', so the operation signal blocking unit 450 Q21 and Q22 are turned on and Q20 is turned off so that the output terminal CSD is in a high state, the first and second gate driving circuit units 100 and 100 perform normal operation.

At the same time, since the gate G outputs a low signal because the drain D and the source S of the FET3 of the warning message notification unit 440 are in phase with the VCC voltage, the light emitting diode LED1 does not operate. In this case, Q10 is 'off', Q11 is 'on' and Q13 is 'off' so that the signal switching unit 430 is 'off'.

On the other hand, the high-level voltage detector of FIG. 8 when a short with the ground, a short between the + and-ends of the speaker, or a short circuit of AC component flows and an over current flows. Since Q21 and Q22 connected to the high input terminal FET-H of 410 and the low input terminal FET-L of the low level voltage sensing unit 420 are 'off', D12 and D14 operate.

Then, since Q17 and Q19 of the signal switching unit 430 are 'off' and Q15 and Q14 are 'on', D10 and D11 do not operate and the output contact D becomes 'off', so the operation signal Since the Q21 and Q22 of the blocking unit 450 are 'off' and Q20 is' on ', and the output terminal CSD is' low', the first and second gate driving circuit units 100 and 100 'do not operate. Will not.

At the same time, since the drain D and the source S of the FET3 of the warning message notification unit 440 are out of phase with the VCC voltage and the gate G outputs a high signal, the light emitting diode LED1 is operated. A warning message is issued, where Q10 is 'on', Q11 is 'off' and Q13 is 'on' so that the output contact D is at ground level.

Hereinafter, the limiter circuit portion connected to the input terminal INT of the audio amplifier of FIG. 4 will be described with reference to FIG. 9.

9 is a detailed circuit diagram of the limiter circuit unit 500 according to an embodiment of the present invention.

First, when the limiter circuit unit 500 is supplied with a voltage equal to or greater than a reference input voltage of 1 Vrms to the input terminal INT of FIG. 4, and the first and second gate driving circuit units 100 and 100 ′ are amplified above the peak value, When the speaker line, which is an output terminal, is shorted, an overcurrent flows instantaneously through the first and second gate driving circuit units 100 and 100 'and is destroyed. In order to prevent the breakdown, the input terminal INT of the digital audio amplifier exceeds the reference voltage. Blocking this supply protects the entire circuit.

That is, the limiter circuit unit 500 distributes the voltage through the distribution resistors R8 and R9 connected in series when the output side voltage becomes 1 Vrms or more. In this case, the voltage coming through the capacitor C5 connected between the distribution resistors R8 and R9 is an audio signal of an AC component, and the capacitor C5 removes the DC component from the audio signal.

Here, the AC component through the capacitor C5 is full-wave rectified by a diode D3 having an anode and a cathode sequentially connected to the capacitor C5, and a capacitor C4 connected with the cathode of the diode and grounded. After the signal is converted to an effective value, a bias voltage is supplied to a transistor Q3 having a base connected to the cathode of the diode D3 to turn on the transistor Q3 and simultaneously supply an operating voltage to the laser diode resistor LDR1. This prevents the output voltage from being supplied above the reference input voltage.

At this time, the base of the transistor Q2 is connected to the collector of the transistor Q3, the anode and the cathode are sequentially connected to the zener diode D1 to the emitter of the transistor Q2, and the transistor Q2 Is connected to the collector of the transistor Q1, the cathode and the anode are sequentially connected to the base of the transistor Q1, and the grounded zener diode D2 is connected to the collector of the transistor Q1. Is further configured with a constant voltage circuit configured to be connected to the laser diode resistor LDR1 so that the laser diode resistor LDR1 can supply sufficient current of several tens of mA.

That is, when the output voltage is higher than the reference voltage, the limiter circuit unit 500 supplies the operating voltage to the laser diode resistor LD1 while the transistor Q3 is turned on, so that the voltage and output are not supplied above the reference voltage. Is a feedback circuit that compares each other, and prevents the first and second gate driving circuit portions 100 and 100 'from being damaged. In this case, reference numeral 510 is a comparator (ICB) for comparing the reference voltage and the output voltage.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Of course.

100: first gate driver circuit part 100 ': second gate driver circuit part
150: phase inversion circuit unit 200: first switching unit
200 ': second switching unit 300: output circuit unit
400: overcurrent detection circuit unit 410: high level voltage detection unit
420: low level voltage detection unit 430: signal switching unit
440: warning message notification unit 450: operation signal blocking unit
500: limiter circuit

Claims (7)

A first gate driving circuit unit 100 which receives an analog audio signal and converts it into a digital PWM signal, a phase inversion circuit unit 150 for generating an inverted analog audio signal by phase inverting the analog audio signal, and the phase inversion circuit unit A second gate driving circuit unit 100 ′ which receives the inverted analog audio signal from the input unit 150 and converts the inverted analog audio signal into an inverted digital PWM signal, and switches by the digital PWM signal of the first gate driving circuit unit 100. A first switching unit 200 to be switched, a second switching unit 200 'switched by the inverted digital PWM signal of the second gate driving circuit unit 100', the first switching unit 200 and A circuit for protecting a speaker line of a digital audio amplifier including an output circuit unit 300 for outputting an output signal from the second switching unit 200 'through a speaker line,
Detecting the switch-on resistance of the first and second switching unit (200 and 200 ') to detect the over-current to stop the operation of the first and second gate driving circuit unit (100 and 100') when an abnormal signal is generated due to overcurrent Speaker line protection circuit of a digital audio amplifier comprising a circuit unit (400). The method of claim 2,
The overcurrent detection circuit 400,
A high level voltage detector 410 for detecting a change in a switch-on resistance value when + power (+ VBB) is supplied to the first and second switching units 200 and 200 ';
A low level voltage sensing unit 420 for detecting a change in the value of the switch-on resistance when the power source (-VEE) is supplied to the first and second switching units 200 and 200 ';
An operation signal blocking unit for stopping an operation of the first and second gate driving circuit units 100 and 100 ′ by sending an abnormal detection signal according to the detection of the high level voltage detector 410 and the low level voltage detector 420. Speaker line protection circuit of a digital audio amplifier, characterized in that it comprises a (450). The method of claim 2,
The overcurrent detection circuit 400,
Signal switching unit for immediately stopping the operation of the first and second gate driving circuit unit (100, 100 ') when detecting the abnormal signal through the high level voltage detector 410 and the low level voltage detector 420 Speaker line protection circuit of the digital audio amplifier, characterized in that it further comprises (430). 4. The method according to claim 2 or 3,
The overcurrent detection circuit 400,
When the detection of the abnormal signal through the high-level voltage detector 410 and the low-level voltage detector 420, further comprises a warning message notification unit 440 for emitting a warning message through the light emitting diode (LED1). Speaker line protection circuit of digital audio amplifier. The method of claim 1,
At the output terminals of the first and second switching units 200 and 200 ′, first and second short circuits are provided to filter external leakage electricity to prevent damage to the first and second gate driving circuit units 100 and 100 ′. An electrical cut-off filter (250 and 250 ') is connected to the speaker line protection circuit of the digital audio amplifier, characterized in that. The method of claim 1,
And a limiter circuit unit 500 is connected to the input terminal INT of the digital audio amplifier to block supply of more than a reference voltage. The method according to claim 6,
The limiter circuit unit 500,
When a voltage above the reference voltage comes in, the voltage is distributed through the distribution resistors R8 and R9 connected in series, the DC component is removed through the capacitor C5 connected between the distribution resistors R8 and R9, and the capacitor C5 An anode and a cathode are sequentially connected to the diode D3 and the cathode of the diode D3 and rectified by a grounded capacitor C4 to convert the DC signal into an effective value, and then the cathode of the diode D3. By supplying a bias voltage to the transistor (Q3) connected to the base to turn on the transistor (Q3) and at the same time supplying an operating voltage to the laser diode resistor (LDR1) to prevent the output voltage is supplied above the reference input voltage Speaker line protection circuit of a digital audio amplifier, characterized in that.

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