Class-d audio amplifier with improved idle-state power consumption and public address system using the same

Abstract

A Class-D amplifier is disclosed, comprising: a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage (the first DC voltage and the second DC voltage are applied to the Class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, wherein the DC level of the first DC voltage is higher than the DC level of the second DC voltage); a low-pass filter circuit (including an inductor); a first additional switching circuit coupled between the switching circuit and the inductor; a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the Class-D amplifier; an amplifier controller that controls the Class-D amplifier to operate in an idle state based on the absence of an input audio signal to the Class-D amplifier (control includes keeping the first additional switching circuit and the second additional switching circuit off during the idle state); and an idle state conduction forming two different circuit paths leading from the second voltage terminal through the inductor to the first voltage terminal, each in a different direction between the two terminals of the inductor. It includes a circuit (in which, during operation of the Class-D amplifier in the idle state, one of two different circuit paths provides conduction from the second voltage terminal through the inductor to the first voltage terminal).

Description

Technology Field

[0001] The present disclosure relates to a Class-D audio amplifier with improved power consumption in the idle state and a public address system using the same. Background Technology

[0002] A Public Address (PA) system is installed in environments such as buildings or complexes—e.g., apartment complexes, schools, government offices, large buildings, airports, shopping malls, etc.—and is configured to broadcast sounds, such as announcements or background music, over a wide area. A PA system may also be equipped with the function of performing emergency broadcasts to notify of emergency situations (e.g., fire, explosion, flooding, power outage, earthquake, etc.) occurring within or near the environment in which it is installed.

[0003] A conventional PA system (100) as illustrated in FIG. 1 includes a power supply unit (110) (which includes, for example, a switching mode power supply (SMPS)), a class-D audio amplifier (which may be abbreviated as class-D amplifier below) (150) that amplifies an audio signal with direct current (DC) power supplied from the power supply unit (110), and a speaker (190) coupled to the class-D amplifier (150) to be driven by an amplified audio signal (for example, a low-pass filtered version of an amplified pulse signal) output from the class-D amplifier (150). Additionally, as depicted in FIG. 1, a power supply unit (110) (e.g., SMPS) includes a power converter (120), and a Class-D amplifier (150) includes a switching circuit (160), a low-pass filter (LPF) circuit (170), and an amplifier controller (180).

[0004] The power converter (120) of the power supply unit (110) (e.g., SMPS) receives an input voltage (V) through the input terminal of the power converter (120). in )(e.g., AC voltage (V) applied to a power supply unit (110) from a grid power source (e.g., mains power source), for example, through an Electromagnetic Interference (EMI) filter) AC ) is the input voltage (V in The DC voltage applied to the power supply (110) from a DC power source, such as a backup battery or rectified into ) is the input voltage (V in Power conversion is performed on the (boosted to ) to obtain a predetermined DC level output voltage (V) as the output of the power supply device (110). DC It generates ). As illustrated in FIG. 1, the output voltage (V) of the power supply (110) DC ) is a capacitor (C a The supply voltage (V) appearing across ) a ) and capacitor(C b The supply voltage (V) appearing across ) b It can be applied to a Class-D amplifier (150) as a capacitor (C a ) is the high-voltage output terminal (T) of the power converter (120). a Having one end coupled to ) and the other end grounded, capacitor (C b ) is the low-voltage output terminal (T) of the power converter (120). b It has one end coupled to ) and the other end grounded. For example, a capacitor (C a ) and capacitor(C b ) can have the same capacitance value, and the supply voltage (V a ) and supply voltage (V b ) are each high-voltage output terminals (T aThe positive supply voltage (e.g., +HV) appearing at ) and its inverted level at the low voltage output terminal (T -b It may be a negative supply voltage (e.g., -HV) appearing in ).

[0005] The switching circuit (160) of the Class-D amplifier (150) is a terminal (T a , T b A switch (M) coupled in series between ) a , M b )(e.g., includes a switching element such as a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET)). As previously described, for power supply to the switching circuit (160), the output voltage (V) of the power supply device (110) DC ) is applied to the switching circuit (160), and the switching circuit (160) is terminal (T a ) and terminal (T b Through ), each voltage (V a )(e.g., constant supply voltage such as +HV) and voltage (V b )(e.g., a negative supply voltage such as -HV) can be received. Accordingly, the switching circuit (160) can receive the applied voltage (V a , V b Audio signal amplification is performed using ) as the bias voltage.

[0006] The LPF circuit (170) of the Class-D amplifier (150) is interposed between the switching circuit (160) and the speaker (190). The LPF circuit (170) is an inductor (L f ) and capacitor(C f It includes an inductor (L f One part of ) is the switch (M a , M b Coupled to the common terminal of ), and capacitor (C f One end of ) is grounded, and the inductor (Lf The other end of ) and the capacitor (C f The other ends of ) are coupled to each other. The speaker (190) is a capacitor (C f It is coupled between these two terminals of ).

[0007] The amplifier controller (180) of the Class-D amplifier (150) receives the input audio signal (S in )(This has a low frequency component signal of, for example, 20 Hz to 20 kHz) and a carrier signal (S car )(This is, for example, a triangular wave signal or a sawtooth wave signal having a high frequency of 200 kHz to 550 kHz) compared to a Pulse Width Modulation (PWM) signal (S PWM ) generates. The gate driver (161) of the switching circuit (160) switches (M) according to the PWM signal. a , M b Drives ) (e.g., switch(M a , M b Each of them turns on (i.e., conducts) when a "high" voltage is applied to its gate and turns off (i.e., cuts off) when a "low" voltage is applied to its gate). In particular, the gate driver (161) is a switch (M a , M b Set an appropriate gate voltage for the switch (M) so that it operates complementarily. a , M b ) can be applied to each (e.g., switch (M a While ) is on, the switch (M b Leave ) off, and switch (M b While ) is on, the switch (M a Leave ) off). In this way, the switch (M a , M bAs the operation proceeds, the switching circuit (160) switches between a power rail of high voltage (e.g., positive supply voltage such as +HV) and a power rail of low voltage (e.g., negative supply voltage such as -HV) to input audio signal (S in A series of higher level voltage pulses (S) compared to ) PT ) generates. The LPF (170) generates this amplified pulse signal (S PT By removing high-frequency components of the output audio signal (S out ) generates. Then, the speaker (190) outputs an audio signal (S out It is driven by ).

[0008] Class-D audio amplifiers for PA systems, such as the Class-D amplifier (150) of the PA system (100), typically have varying usage frequencies depending on the usage environment. Generally, a Class-D audio amplifier for PA can be designed to enter an idle state when usage frequency is low (e.g., when no audio signal is input for a while). While operating in the idle state, the Class-D amplifier for PA can continue to perform its switching operation (e.g., the switching operation of the switching circuit (160) of the Class-D amplifier (150)) together with, for example, the switching operation to supply DC power to this amplifier (e.g., the switching operation of the SMPS of the power supply unit (110). Power may be consumed in the idle state by such switching operation.

[0009] Despite this power consumption, users typically avoid turning off Class-D audio amplifiers for PAs that are not frequently used in order to avoid the following problems: turning the amplifier off and then back on takes a considerable amount of time, which causes a delay in public address announcements in the event of an emergency, such as an unexpected accident.

[0010] Specifically, in an example where an integrated circuit (IC), such as the driver IC chip IRS2052M available from Infineon Technologies, is used to drive the switching circuit (160) of the SMPS and Class-D amplifier (150) of the power supply unit (110) of the PA system (100), such a driver IC may be equipped with an overcurrent protection (OCP) circuit (designed to take a certain amount of time from restart to normal operation of the SMPS and Class-D amplifier (150) in order to prevent damage to the switching elements of the SMPS and the switching circuit (160) in the event of an overcurrent), if the output of each of the SMPS and Class-D amplifier (150) is large (and thus the capacitance on each output side is large), turning off both the SMPS and Class-D amplifier (150) and then turning them on is a soft start time involved in the OCP operation sequence. It can be extended. This is because the soft start time is associated with the OCP circuit, and increases proportionally with the capacity due to the heat generated by the switching element. In this situation, as both the SMPS and the Class-D amplifier (150) operate normally, it may take at least a few seconds, or up to tens of seconds, until the audio signal is properly output to the speaker (190) and the public address is announced. The problem to be solved

[0011] A Class-D amplifier with improved power consumption in idle state and a public address system using the same are disclosed in this document. means of solving the problem

[0012] In the example, the class-D amplifier comprises a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage (the first DC voltage and the second DC voltage are applied to the class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, wherein the DC level of the first DC voltage is higher than the DC level of the second DC voltage), a low-pass filter (LPF) circuit (the LPF circuit includes an inductor), a first additional switching circuit coupled between the switching circuit and the inductor, a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the class-D amplifier, an amplifier controller that controls the class-D amplifier to operate in an idle state based on the absence of an input audio signal to the class-D amplifier (control includes keeping the first additional switching circuit and the second additional switching circuit off during the idle state), and two different circuit paths (these Each includes an idle state conduction circuit that forms a second voltage terminal through the inductor to the first voltage terminal in each of the two different directions between the two terminals of the inductor (during operation of the Class-D amplifier in the idle state, one of two different circuit paths provides conduction from the second voltage terminal through the inductor to the first voltage terminal).

[0013] The foregoing overview is provided to introduce, in a simplified form, some aspects that will be further described later in the detailed description. This overview is not intended to identify important or essential features of the claimed subject matter, nor is it intended to be used to define the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to any or all advantageous implementations discussed herein. Effects of the invention

[0014] According to the present disclosure, even if a Class-D amplifier continuously performs switching operations, it can consume a smaller amount of power, particularly during an idle state where there is no input audio signal.

[0015] A public address system using a Class-D amplifier according to the present disclosure can reduce power consumption compared to conventional public address systems while operating continuously to prevent excessive delay in public address announcements such as the occurrence of emergency situations. Brief explanation of the drawing

[0016] Figure 1 is a schematic diagram of a conventional PA system. Figure 2 schematically shows an example of a PA system including an exemplary Class-D amplifier. Figure 3 is an equivalent illustration of Figure 2 while the Class-D amplifier of Figure 2 is operating in a normal state. Figure 4 is a timing diagram schematically showing exemplary simulated waveforms of voltage and current appearing in some parts of the Class-D amplifier of Figure 2 while it is operating in a steady state. FIG. 5 is a circuit diagram showing an exemplary circuit configuration of the first additional switching circuit of FIG. 2. Figure 6 shows an example in which each of the four switching elements of the idle state conduction circuit of the Class-D amplifier of Figure 2 is configured as a diode. FIG. 7 schematically depicts an example of conduction occurring along one of two different circuit paths while the Class-D amplifier of FIG. 6 is operating in an idle state, in an equivalent diagram to FIG. 6. FIG. 8 schematically depicts an example in which conduction occurs along one of two different circuit paths while the Class-D amplifier of FIG. 6 is operating in an idle state, in an equivalent illustration to FIG. 6. Specific details for implementing the invention

[0017] The various terms used in this disclosure are selected from the conventions of common terminology in consideration of their function within this document, as they may be perceived differently depending on the intent, practices, or emergence of new technology of those skilled in the art. In specific instances, some terms may be given meanings as set forth in the detailed description. Accordingly, terms used in this document should be defined consistently with their meaning in the context of this disclosure, rather than merely by their names.

[0018] In this document, terms such as "include," "have," etc., are used to specify the presence of the elements listed below, e.g., certain features, numbers, steps, actions, components, information, or combinations thereof. Unless otherwise indicated, these terms and variations thereof are not intended to exclude the presence or addition of other elements.

[0019] As used in this document, terms “first,” “second,” etc. are intended to identify several similar elements. Unless otherwise stated, such terms are not intended to impose limitations, such as a specific order of use of these elements or their elements, but are used merely to refer to several elements separately. For example, while an element may be referred to as the term “first” in one example, the same element may be referred to by a different ordinal number, such as “second” or “third,” in another example. In such examples, these terms do not limit the scope of this disclosure. Furthermore, the use of the term “and / or” in a list of elements includes any one or more of the listed items, as well as all possible combinations of these items. Moreover, expressions in the singular form include the meaning of the plural form unless explicitly stated otherwise.

[0020] Certain examples of the present disclosure will now be described in detail with reference to the attached drawings. However, the present disclosure may be embodied in many different forms and should not be construed as being limited to the examples set forth in this document. Rather, these examples are provided to provide a better understanding of the scope of the present disclosure.

[0021] FIG. 2 is a schematic diagram of an exemplary PA system (200).

[0022] In the illustrated example, the PA system (200) includes a Class-D amplifier (250) and a speaker (290), the Class-D amplifier (250) can amplify an input audio signal with DC power supplied (e.g., from a power supply (e.g., SMPS)) and output it as a speaker driving signal, and the speaker (290) can be coupled to the Class-D amplifier (250) and driven by the speaker driving signal output from the Class-D amplifier (250).

[0023] Specifically, as illustrated in FIG. 2, the Class-D amplifier (250) includes a switching circuit (260), an LPF circuit (270), an amplifier controller (280), a first additional switching circuit (231), a second additional switching circuit (232), and an idle state conduction circuit (240).

[0024] The switching circuit (260) performs switching between a first DC voltage and a second DC voltage to generate a switched DC voltage. The first DC voltage and the second DC voltage are applied to a Class-D amplifier (250) (in particular, the switching circuit (260)) through a DC voltage terminal (T1) (which may also be referred to as the first voltage terminal) and a DC voltage terminal (T2) (which may also be referred to as the second voltage terminal) (e.g., from an SMPS), such that the DC level of the first DC voltage is higher than the DC level of the second DC voltage. In the example of FIG. 2, the first DC voltage is the DC voltage at the other end of the capacitor (C1) relative to the grounded end of the capacitor (C1), that is, the DC voltage appearing at the first voltage terminal (T1) (e.g., a positive supply voltage of +HV as depicted in FIG. 2), and the second DC voltage is the DC voltage at the other end of the capacitor (C2) relative to the grounded end of the capacitor (C2), that is, the voltage appearing at the second voltage terminal (T2) (e.g., a negative supply voltage of -HV having the same magnitude as the positive supply voltage and opposite polarity as depicted in FIG. 2).

[0025] The switching circuit (260) may include several switches, each of which may be an n-type MOSFET, a p-type MOSFET, or any other suitable semiconductor switching element. For example, as shown in FIG. 2, the switching circuit (260) may include switches (M1) and switches (M2) in a half-bridge topology, where these two switches (M1, M2) have a common terminal (T) coupled to a first additional switching circuit (231). M It has a switching circuit (260) (thereby providing a switched DC voltage from the switching circuit (260)) and has other terminals coupled to the first voltage terminal (T1) and the second voltage terminal (T2), respectively. In another example, the switching circuit (260) may alternatively include four switches in a full-bridge topology.

[0026] The aforementioned switching of the switching circuit (260) may involve turning on and turning off each of these switches (e.g., switches M1 and M2) according to an audio signal input to the Class-D amplifier (250) (particularly, amplifier controller (280)) (e.g., by performing PWM on the input audio signal and using such modulated audio signal), thereby performing switching between a power rail of a first DC voltage and a power rail of a second DC voltage, e.g., generating a DC voltage switched between +HV and -HV.

[0027] The LPF circuit (270) is illustrated in FIG. 2 as comprising a first filter circuit portion (271) and a second filter circuit portion (272), wherein the first filter circuit portion (271) comprises an inductive element (which is depicted as an inductor (L) in FIG. 2), and the second filter circuit portion (272) comprises an additional filter element, for example, an output terminal (T) for outputting a speaker drive signal from a Class-D amplifier (250) in FIG. 2. O It includes a capacitive element or other type of filter element described as a capacitance (C) coupled to ).

[0028] The first additional switching circuit (or abbreviated as SW1) (231) is the terminal (T) of the switching circuit (260) (T M )) and the first terminal (T) of the inductor (L) (of the first filter circuit portion (271) of the LPF circuit (270) L1 )) coupled between, and the second additional switching circuit (or abbreviated as SW2) (232) is coupled to the second terminal (T) of the inductor (L) (of the LPF circuit (270). L2 )) and output terminal (T OSW1 (231) and SW2 (232) can be turned on or turned off by the amplifier controller (280) (e.g., sequentially) so that the Class-D amplifier (250) enters a predetermined state (e.g., normal state or idle state), as will be discussed in more detail below.

[0029] The idle state conduction circuit (240) forms two different circuit paths, a first circuit path and a second circuit path, each of which is from the second voltage terminal (T2) to the two terminals (T) of the inductor (L) L1 , T L2 Each of the inductors (L) is connected to the first voltage terminal (T1) via the inductor (L) in its respective different direction. As depicted in FIG. 2, the idle state conduction circuit (240) may include the following four switching elements (each of which may include, for example, a unidirectional conduction element, such as a diode, or another type of semiconductor switch): the first terminal (T1) of the inductor (L). L1 A first switching element (241) coupled between ) and a first voltage terminal (T1); a second terminal (T) of an inductor (L). L2 A second switching element (242) coupled between ) and the first voltage terminal (T1); the first terminal (T) of the inductor (L). L1 A third switching element (243) coupled between ) and a second voltage terminal (T2); and the second terminal (T) of the inductor (L). L2A fourth switching element (244) coupled between the second voltage terminal (T2). Then, the first circuit path may be formed by the fourth switching element (244), an inductor (L), and the first switching element (241), and the second circuit path may be formed by the third switching element (243), an inductor (L), and the second switching element (242). In particular, as discussed in more detail below, while the Class-D amplifier (250) is operating in an idle state, one of the first circuit path and the second circuit path may provide conduction from the second voltage terminal (T2) through the inductor (L) to the first voltage terminal (T1). Additionally, while the Class-D amplifier (250) is operating in a normal state, each of the first circuit path and the second circuit path may be formed to prevent such conduction. Additionally, the first circuit path and the second circuit path can each be formed to prevent conduction from the first voltage terminal (T1) through the inductor (L) to the second voltage terminal (T2).

[0030] The amplifier controller (280) processes the input audio signal to control the switching operation of the switching circuit (260). Such control may include generating an amplifier switching control signal based on the input audio signal and providing it to the switching circuit (260), for example, providing a carrier signal (e.g., a triangular wave signal or a sawtooth wave signal) modulated (e.g., pulse width modulated) as the input audio signal to the gate driver (261) of the switching circuit (260) as the amplifier switching control signal, for example, as depicted in FIG. 2. Then, the gate driver (261) can drive the switches (e.g., switches M1 and M2) of the switching circuit (260) according to the amplifier switching control signal by applying an appropriate gate voltage to each of the switches (M1, M2) so that the switches (M1 and M2) operate complementarily. Accordingly, the switching circuit (260) can switch the DC voltage (e.g., terminal (T MIt can provide an amplified level pulse signal appearing in ).

[0031] The amplifier controller (280) can determine whether an audio signal is input to the Class-D amplifier (250). For example, the amplifier controller (280) can determine that an audio signal is input to the Class-D amplifier (240) when the Class-D amplifier (250) receives an audio signal of a level higher than a predetermined level, and can determine that the input audio signal to the Class-D amplifier (240) is absent when it does not.

[0032] Based on the result of such determination, the amplifier controller (280) can switch the operating state of the Class-D amplifier (250). For example, in response to an audio signal being input to the Class-D amplifier (250), the amplifier controller (280) can control the Class-D amplifier (250) to operate in a normal state, such control can keep SW1 (231) and SW2 (232) each closed (i.e., on) during the normal state of the Class-D amplifier (250) so that the terminal (T) of the switching circuit (260) M ) as an output terminal (T) for outputting the speaker driving signal O By coupling with ), the terminal (T M ) and output terminal (T O It includes providing conduction between ) via an inductor (L). Accordingly, while the Class-D amplifier (250) is operating in a normal state, the switching of the switching circuit (260) can be controlled by a carrier signal modulated by the input audio signal, and the LPF circuit (270) outputs an amplified version of the input audio signal to the output terminal (T O The switched DC voltage from the switching circuit (260) can be filtered to be provided as a speaker driving signal, and the speaker (290) can be driven by such a speaker driving signal.

[0033] FIG. 3 is an equivalent illustration to FIG. 2 while the Class-D amplifier (250) is operating in a steady state (with both SW1 (231) and SW2 (232) kept ON, as described above). FIG. 4 schematically shows exemplary simulated waveforms of voltage and current appearing in some parts of the Class-D amplifier (250) during the operation of the Class-D amplifier (250) in a steady state. In the example of FIG. 4, it is assumed that the first DC voltage is +HV = 80 V, the second DC voltage is -HV = -80 V, the inductor (L) has an inductance of 21 μH, and the capacitor (C) has a capacitance of 470 nF. The following graph is shown in FIG. 4: The red graph labeled "Vinv" represents the terminal (T) to ground. M Simulated waveform of the switched DC voltage at ) (which fluctuates between +HV and -HV depending on the complementary operation of switches (M1, M2)) shown in volts over time; the red graph labeled "V_HIGH" represents the voltage across switch (M1), in other words, terminal (T M Simulated waveform of the voltage at the first voltage terminal (T1) for ) (which fluctuates between 0V and +HV-(-HV)=+2HV depending on the on or off of the switch (M1)) shown in volts over time; the blue graph labeled "I(MOS1)*10" shows the voltage from the first voltage terminal (T1) to the terminal (T M The simulated waveform of the current flowing through the switch (M1) in the direction toward ) is displayed magnified tenfold in amperes over time; the red graph labeled "V_LOW" represents the voltage across the switch (M2), that is, the terminal (T) for the second voltage terminal (T2). MSimulated waveform of the voltage at ) (which fluctuates between 0V and +HV-(-HV)=+2HV depending on the on or off of switch (M2)) shown in volts over time; the blue graph labeled "I(MOS2)*10" is the terminal (T M The simulated waveform of the current flowing through the switch (M2) in the direction from ) to the second voltage terminal (T2) is displayed magnified tenfold in amperes over time; and the red graph labeled "i(Lo)" is the first terminal (T) of the inductor (L). L1 From ) to the second terminal (T) of the inductor (L) L2 Simulated waveform of current flowing through the inductor (L) in the direction of ) is displayed in amperes over time.

[0034] Referring to FIG. 2, the amplifier controller (280) can control the Class-D amplifier (250) to operate in an idle state based on the absence of an input audio signal to the Class-D amplifier (250), such control includes keeping SW1 (231) and SW2 (232) each open (i.e. off) during the operation of the Class-D amplifier (250) in the idle state.

[0035] For the aforementioned control of the amplifier controller (280), the amplifier controller (280) may switch the Class-D amplifier (250) to an idle state (e.g., from a normal state) when the absence of an input audio signal to the Class-D amplifier (250) persists. For example, in response to the duration of the absence of an input audio signal to the Class-D amplifier (250) reaching a predetermined threshold time length, e.g., a predetermined time length (e.g., 30 seconds) that is at least 20 seconds and no more than 60 seconds, the amplifier controller (280) may cause the Class-D amplifier (250) to enter an idle state by, for example, turning off SW2 (232) followed by turning off SW1 (231). For example, as depicted in FIG. 5, SW1 (231) is the common terminal (T) of the switches (M1, M2) of the switching circuit (260). M )) and the first terminal (T) of the inductor (L) ( L1 Two series switching elements (SW) coupled between )) 1a , SW 1b ) and, to reduce the inrush current generated during the operation of SW1 (231), a switching element (SW 1b A resistive element (R) coupled in parallel to ) (which includes at least one of, for example, a thermistor or a fixed resistor), and SW1 (231) may include two series switching elements (SW 1a , SW 1b Sequential turn-off of ) (e.g., switching element (SW 1a Following the turn-off of the switching element (SW 1b Turn-off of ) or switching element (SW 1b Following the turn-off of the switching element (SW 1a It can be turned off as a turn-off of ).

[0036] As long as the absence of an input audio signal to the Class-D amplifier (250) persists for a threshold time length or longer, the amplifier controller (280) may keep the Class-D amplifier (250) in an idle state. While the Class-D amplifier (250) is operating in an idle state, conduction may occur from the second voltage terminal (T2) through the inductor (L) to the first voltage terminal (T2) along one of the first circuit path and the second circuit path. For example, when the Class-D amplifier (250) enters the idle state, the second terminal (T) of the inductor (L) L2 From ) to the first terminal (T) of the inductor (L) L1 When current flows in the direction of ), the first circuit path can provide conduction from the second voltage terminal (T2) through the inductor (L) to the first voltage terminal (T1) during the idle state (in other words, from the second voltage terminal (T2), through the fourth switching element (244), to the second terminal (T1) of the inductor (L) L2 From ) to the first terminal (T) of the inductor (L) L1 Conduction to the first voltage terminal (T1) can occur via the inductor (L) and the first switching element (241) in the direction of ). Otherwise, when the Class-D amplifier (250) enters the idle state, the first terminal (T) of the inductor (L) L1 From ) to the second terminal (T) of the inductor (L) L2 When current flows in the direction of ), the second circuit path can provide conduction from the second voltage terminal (T2) through the inductor (L) to the first voltage terminal (T1) during the idle state (in other words, from the second voltage terminal (T2), through the third switching element (243), to the first terminal (T1) of the inductor (L) L1 From ) to the second terminal (T) of the inductor (L) L2Conduction to the first voltage terminal (T1) may occur through the inductor (L) and the second switching element (242) in the direction of ). Meanwhile, conduction from the first voltage terminal (T1) to the second voltage terminal (T2) through the inductor (L) may not occur along either the first circuit path or the second circuit path.

[0037] Control performed by the amplifier controller (280) during the idle state and conduction provided by the idle state conduction circuit (240) can divert the current flowing through the inductor (L) from the second voltage terminal (T2) to the first voltage terminal (T1) along the first circuit path or the second circuit path while suppressing the current flowing through the inductor (L) of the LPF circuit (270) to the speaker (290), even if the switching circuit (260) of the class-D amplifier (250) continues to switch without an input audio signal to the class-D amplifier (250) (e.g., with a 50% duty cycle that the PWM signal has when the input audio signal is given as a zero input). This ultimately includes various losses occurring during the idle state, for example, losses occurring in the inductor (L) of the LPF (270), losses occurring in the speaker (290), turn-on losses and turn-off losses of each switch (M1, M2) of the switching circuit (260), and conduction losses occurring in each switch (M1, M2) of the switching circuit (260) (this is the drain-source on state resistance (R) of the corresponding switch). DSon (can be given according to ) etc. can be reduced compared to the case where there is no control and conduction as described above. Furthermore, since the residual noise path is cut off during the idle state, the transmission of white noise to the speaker (290) can be prevented.

[0038] FIG. 6 shows an example in which the first to fourth switching elements (241, 242, 243, 244) of the idle state conduction circuit (240) of the Class-D amplifier (250) are each configured as first to fourth diodes (D1, D2, D3, D4). An equivalent illustration to FIG. 6 is shown in FIG. 7 and FIG. 8, respectively, while the Class-D amplifier (250) configured in this way is operating in an idle state (with both SW1 (231) and SW2 (232) kept off as described above), FIG. 7 and FIG. 8 also schematically depict an example of conduction occurring along the first circuit path and conduction occurring along the second circuit path during the idle state, respectively.

[0039] As shown in FIGS. 6 to 8, the first diode (D1) is the first terminal (T) of the inductor (L). L1 ) allows unidirectional conduction from the first voltage terminal (T1), and the second diode (D2) is the second terminal (T) of the inductor (L). L2 ) allows unidirectional conduction from ) to the first voltage terminal (T1), and the third diode (D3) allows unidirectional conduction from the second voltage terminal (T2) to the first terminal (T) of the inductor (L). L1 ) allows unidirectional conduction to ), and the fourth diode (D4) allows unidirectional conduction from the second voltage terminal (T2) to the second terminal (T) of the inductor (L). L2 ) allows unidirectional conduction to. Accordingly, the first circuit path is as depicted in FIG. 7 (in other words, while the Class-D amplifier (250) is operating in an idle state, from the second voltage terminal (T2) through the fourth diode (D4) to the second terminal (T L2 From ) the first terminal (T L1It is formed by a fourth diode (D4), an inductor (L), and a first diode (D1) to provide unidirectional conduction to the first voltage terminal (T1) via the inductor (L) and the first diode (D1) in the direction toward ). Additionally, the second circuit path is formed as depicted in FIG. 7 (in other words, from the second voltage terminal (T2) through the third diode (D3) to the first terminal (T) while the Class-D amplifier (250) is operating in an idle state). L1 From ) the second terminal (T L2 It is formed by a fourth diode (D4), an inductor (L), and a first diode (D1) to provide unidirectional conduction to the first voltage terminal (T1) through the inductor (L) and the second diode (D2) in the direction of ). Additionally, when the Class-D amplifier (250) is operating in a normal state, all diodes (D1, D2, D3, D4) may be blocked.

[0040] Subsequently, when an audio signal is input to the Class-D amplifier (250), the amplifier controller (280) can switch the Class-D amplifier (250) from an idle state to a normal state. For example, the amplifier controller (280) can cause the Class-D amplifier (250) to enter a normal state by turning on SW1 (231) and then turning on SW2 (232) in response to the input of an audio signal to the Class-D amplifier (250). In an example where SW1 (231) is configured as shown in FIG. 5, SW1 (231) consists of two serial switching elements (SW 1a , SW 1b Sequential turn-on of ) (e.g., switching element (SW 1a Following the turn-on of ), the switching element (SW 1b Turn-on of ), or switching element (SW 1b Following the turn-on of ), the switching element (SW 1a It can be turned on as the turn-on of ).

[0041] The following are various examples of a Class-D amplifier with improved power consumption in idle state and a public address system utilizing it.

[0042] In Example 1, the Class-D amplifier comprises a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage (wherein the first DC voltage and the second DC voltage are applied to the Class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, wherein the DC level of the first DC voltage is higher than the DC level of the second DC voltage), a low-pass filter (LPF) circuit (wherein the LPF circuit includes an inductor), a first additional switching circuit coupled between the switching circuit and the inductor, a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the Class-D amplifier, and an amplifier controller that controls the Class-D amplifier to operate in an idle state based on the absence of an input audio signal to the Class-D amplifier (wherein the control keeps the first additional switching circuit and the second additional switching circuit off during the idle state). It includes an idle state conduction circuit that forms two different circuit paths leading from the second voltage terminal to the first voltage terminal through the inductor in each different direction between the two terminals of the inductor (one of the two different circuit paths provides conduction from the second voltage terminal to the first voltage terminal during the operation of the Class-D amplifier in the idle state).

[0043] Example 2 includes the subject of Example 1, where each of the two different circuit paths also prevents conduction from the first voltage terminal above through the inductor above to the second voltage terminal above.

[0044] Example 3 includes the subject of Example 1 or Example 2, wherein the above idle state conduction circuit comprises a first switching element coupled between the first terminal of the two upper terminals of the above inductor and the above first voltage terminal, a second switching element coupled between the second terminal of the two upper terminals of the above inductor and the above first voltage terminal, a third switching element coupled between the first terminal of the above inductor and the above second voltage terminal, and a fourth switching element coupled between the second terminal of the above inductor and the above second voltage terminal, such that the first circuit path of the above two different circuit paths is formed by the above fourth switching element, the above inductor, and the above first switching element, and the second circuit path of the above two different circuit paths is formed by the above third switching element, the above inductor, and the above second switching element.

[0045] Example 4 includes the subject of Example 3, wherein the first switching element, the second switching element, the third switching element, and the fourth switching element are each unidirectional conductive elements.

[0046] Example 5 includes the subject of any of Examples 1 through 4, wherein the idle state conduction circuit comprises a first diode, a second diode, a third diode, and a fourth diode, wherein the anode and cathode of the first diode are coupled to the first terminal of the two upper terminals of the inductor and the first voltage terminal, respectively; the anode and cathode of the second diode are coupled to the second terminal of the two upper terminals of the inductor and the first voltage terminal, respectively; the anode and cathode of the third diode are coupled to the second voltage terminal and the first terminal of the inductor, respectively; and the anode and cathode of the fourth diode are coupled to the second voltage terminal and the second terminal of the inductor, respectively, so that the first circuit path of the two different circuit paths is, during the operation of the Class-D amplifier in the idle state, in the direction from the second voltage terminal through the fourth diode to the first terminal The above fourth diode, the above inductor, and the above first diode are formed to provide unidirectional conduction to the above first voltage terminal through the inductor and through the above first diode, and the second circuit path among the above two different circuit paths is formed by the above third switching element, the above inductor, and the above second switching element to provide unidirectional conduction to the above first voltage terminal through the above inductor and through the above second diode in the direction from the above first terminal to the above second terminal through the above third diode during the above operation of the above Class-D amplifier in the above idle state.

[0047] Example 6 includes the subject of any of Examples 1 to 5, wherein the switching circuit comprises two switching elements, each having one end coupled to the first voltage terminal and the second voltage terminal, and the other end of each of the two switching elements is coupled to each other and is also coupled to the first additional switching circuit.

[0048] Example 7 includes the subject of any of Examples 1 through 6, wherein the above control further includes causing the above Class-D amplifier to enter the above idle state by turning off the above second additional switching circuit followed by turning off the above first additional switching circuit in response to the above absence duration reaching a threshold time length.

[0049] Example 8 includes the subject of any of Examples 1 through 7, wherein the first additional switching circuit comprises two series switching elements coupled between the switching circuit and the inductor, and a resistive element coupled in parallel to one of the two series switching elements, and the first additional switching circuit is turned off by the sequential turn-off of the two series switching elements.

[0050] Example 9 includes the subject of Example 8, wherein the resistive element includes at least one of a thermistor or a fixed resistor.

[0051] Example 10 includes the subject of any of Examples 1 through 9, wherein the above amplifier controller additionally controls the above Class-D amplifier to operate in a normal state based on the input of an audio signal to the above Class-D amplifier, the above additional control includes keeping the above first additional switching circuit and the above second additional switching circuit on during the above normal state.

[0052] Example 11 includes the subject of Example 10, where each of the two different circuit paths prevents conduction from the second voltage terminal through the inductor to the first voltage terminal during the operation of the Class-D amplifier in the above steady state.

[0053] Example 12 includes the subject of Example 10 or Example 11, and the above additional control further includes, in response to the above input of the above audio signal, turning on the above first additional switching circuit followed by turning on the above second additional switching circuit, thereby causing the above Class-D amplifier to enter the above steady state.

[0054] Example 13 includes the subject of any of Examples 10 through 12, wherein during the operation of the above Class-D amplifier in the above normal state, the above switching is controlled by a carrier signal modulated by the above input audio signal, the above LPF circuit filters the above switched DC voltage to generate an amplified audio signal, and the above amplified audio signal is provided at the above output terminal as a above speaker driving signal.

[0055] Example 14 includes the subject of any of Examples 1 through 13, wherein the above LPF circuit further includes a capacitor coupled to the above output terminal.

[0056] Example 15 includes the subject of any of Examples 1 through 14, wherein the upper DC level of the first DC voltage has the same magnitude and opposite polarity as the upper DC level of the second DC voltage.

[0057] In Example 16, the Class-D amplifier comprises a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage (wherein the first DC voltage and the second DC voltage are applied to the Class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, wherein the DC level of the first DC voltage is higher than the DC level of the second DC voltage), a low-pass filter (LPF) circuit (wherein the LPF circuit includes an inductor), a first additional switching circuit coupled between the switching circuit and the inductor, a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the Class-D amplifier, and an amplifier controller that causes the Class-D amplifier to enter an idle state in response to the duration of absence of an input audio signal to the Class-D amplifier reaching a critical time length (wherein during the idle state, the first additional switching circuit and the second additional switching circuit are turned off by the amplifier controller). It includes (maintained) and an idle state circuit (the above idle state circuit includes a first diode allowing unidirectional conduction from the first terminal of the two terminals of the above inductor to the above first voltage terminal, a second diode allowing unidirectional conduction from the second terminal of the two terminals of the above inductor to the above first voltage terminal, a third diode allowing unidirectional conduction from the above second voltage terminal to the above first terminal of the above inductor, and a fourth diode allowing unidirectional conduction from the above second voltage terminal to the above second terminal of the above inductor).

[0058] Example 17 includes the subject of Example 16, wherein the switching circuit comprises two switching elements, each having one end coupled to the first voltage terminal and the second voltage terminal, and the other end of each of the two switching elements is coupled to each other and is also coupled to the first additional switching circuit.

[0059] Example 18 includes the subject of Example 16 or Example 17, wherein causing the above Class-D amplifier to enter the above idle state involves turning off the above second additional switching circuit followed by turning off the above first additional switching circuit.

[0060] Example 19 includes the subject of any of Examples 16 to 18, wherein the first additional switching circuit comprises two series switching elements coupled between the switching circuit and the inductor, and a resistive element coupled in parallel to one of the two series switching elements, and the first additional switching circuit is turned off by the sequential turn-off of the two series switching elements.

[0061] Example 20 includes the subject of Example 19, wherein the resistive element comprises at least one of a thermistor or a fixed resistor.

[0062] Example 21 includes the subject of any of Examples 16 through 20, wherein the above amplifier controller also causes the above Class-D amplifier to enter a steady state in response to an audio signal being input to the above Class-D amplifier, and during the above steady state, the above first additional switching circuit and the above second additional switching circuit are kept on by the above amplifier controller.

[0063] Example 22 includes the subject of Example 21, and during the operation of the above Class-D amplifier in the above normal state, conduction from the above second voltage terminal through the above fourth diode, from the above second terminal through the above inductor and through the above first diode to the above first voltage terminal, and conduction from the above second voltage terminal through the above third diode, from the above first terminal through the above inductor and through the above second diode to the above first voltage terminal is prevented.

[0064] Example 23 includes the subject of Example 21 or Example 22, wherein causing the above Class-D amplifier to enter the above steady state involves turning on the above first additional switching circuit followed by turning on the above second additional switching circuit.

[0065] Example 24 includes the subject of any of Examples 21 through 23, wherein while the above Class-D amplifier is operating in the above normal state, the above switching is controlled by a carrier signal modulated by the above input audio signal, the above LPF circuit filters the above switched DC voltage to generate an amplified audio signal, and the above amplified audio signal is provided at the above output terminal as a above speaker driving signal.

[0066] Example 25 includes the subject of any of Examples 16 through 24, wherein the above LPF circuit further includes a capacitor coupled to the above output terminal.

[0067] Example 26 includes the subject of any of Examples 16 to 25, wherein the upper DC level of the first DC voltage has the same magnitude and opposite polarity as the upper DC level of the second DC voltage.

[0068] In Example 27, the Public Address (PA) system includes a power supply and a Class-D amplifier according to any of Examples 1 to 26, wherein the power supply applies the first DC voltage and the second DC voltage to the Class-D amplifier through the first voltage terminal and the second voltage terminal, respectively.

[0069] Example 28 includes the subject of Example 27, and the above power supply includes a switching mode power supply (SMPS) that converts AC power from a grid power source to generate the above first DC voltage and the above second DC voltage.

[0070] The foregoing description is provided to illustrate and describe several examples in detail. Those skilled in the art will understand that many modifications and variations are possible in light of the foregoing teachings without departing from the scope of this disclosure. In various examples, suitable results may be achieved even if the foregoing techniques are performed in a different order and / or some of the components of the foregoing systems, architectures, devices, circuits and similars are combined or assembled in a different way, or replaced or substituted by other components or equivalents thereof.

[0071] Therefore, the scope of the present disclosure should not be limited to the disclosed forms, but should be determined by the claims and equivalents set forth below. Explanation of the symbols

[0072] 200: Public address system 231: SW1 232: SW2 240: Idle state continuity circuit 241, 242, 243, 244: Switching elements 260: Switching circuit 261: Gate driver 270: LPF circuit 271: First filter circuit section 272: Second filter circuit section 280: Amp controller 290: Speaker

Claims

Claim 1 A Class-D amplifier comprising: a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage, wherein the first DC voltage and the second DC voltage are applied to the Class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, wherein the DC level of the first DC voltage is higher than the DC level of the second DC voltage; a low-pass filter (LPF) circuit, wherein the LPF circuit includes an inductor; a first additional switching circuit coupled between the switching circuit and the inductor; a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the Class-D amplifier; and an amplifier controller that controls the Class-D amplifier to operate in an idle state based on the absence of an input audio signal to the Class-D amplifier, wherein the control includes keeping the first additional switching circuit and the second additional switching circuit off during the idle state. A Class-D amplifier comprising: an idle state conduction circuit forming two different circuit paths leading from the second voltage terminal to the first voltage terminal through the inductor in respective different directions between the two terminals of the inductor, wherein during the operation of the Class-D amplifier in the idle state, one of the two different circuit paths provides conduction from the second voltage terminal through the inductor to the first voltage terminal; wherein the first additional switching circuit comprises two series switching elements coupled between the switching circuit and the inductor, and a resistive element coupled in parallel to one of the two series switching elements, wherein the first additional switching circuit is turned off by the sequential turn-off of the two series switching elements. Claim 2 A Class-D amplifier according to claim 1, wherein the control further comprises causing the Class-D amplifier to enter the idle state by turning off the second additional switching circuit followed by turning off the first additional switching circuit in response to the duration of the absence reaching a threshold time length. Claim 3 delete Claim 4 A Class-D amplifier according to claim 1, wherein the resistive element comprises at least one of a thermistor or a fixed resistor. Claim 5 In claim 1, the amplifier controller additionally controls the Class-D amplifier to operate in a normal state based on the input of an audio signal to the Class-D amplifier, wherein the additional control includes keeping the first additional switching circuit and the second additional switching circuit on during the normal state, a Class-D amplifier. Claim 6 In claim 5, the additional control further comprises causing the Class-D amplifier to enter the normal state by turning on the first additional switching circuit followed by turning on the second additional switching circuit in response to the input of the audio signal in the operation of the Class-D amplifier in the idle state. Claim 7 In claim 5, during the operation of the Class-D amplifier in the above normal state, the switching is controlled by a carrier signal modulated by the input audio signal, the LPF circuit filters the switched DC voltage to generate an amplified audio signal, and the amplified audio signal is provided at the output terminal as the speaker driving signal, a Class-D amplifier. Claim 8 As a Class-D amplifier, a switching circuit that generates a switched DC voltage by performing switching between a first DC voltage and a second DC voltage, wherein the first DC voltage and the second DC voltage are applied to the Class-D amplifier through a first voltage terminal and a second voltage terminal, respectively, and the DC level of the first DC voltage is higher than the DC level of the second DC voltage; and a low-pass filter (LPF) circuit, wherein the LPF circuit includes an inductor; a first additional switching circuit coupled between the switching circuit and the inductor, and a second additional switching circuit coupled between the inductor and an output terminal for outputting a speaker drive signal from the Class-D amplifier; and an amplifier controller that causes the Class-D amplifier to enter an idle state in response to the duration of absence of an input audio signal to the Class-D amplifier reaching a critical time length, wherein during the idle state, the first additional switching circuit and the second additional switching circuit are kept off by the amplifier controller; and the A Class-D amplifier comprising an idle state conduction circuit including a first diode allowing unidirectional conduction from a first terminal of two terminals of an inductor to a first voltage terminal, a second diode allowing unidirectional conduction from a second terminal of two terminals of the inductor to a first voltage terminal, a third diode allowing unidirectional conduction from a second voltage terminal to a first terminal of the inductor, and a fourth diode allowing unidirectional conduction from a second voltage terminal to a second terminal of the inductor, wherein the first additional switching circuit comprises two series switching elements coupled between the switching circuit and the inductor and a resistive element coupled in parallel to one of the two series switching elements, and the first additional switching circuit is turned off by the sequential turn-off of the two series switching elements. Claim 9 In claim 8, the amplifier controller also causes the Class-D amplifier to enter a steady state in response to an audio signal being input to the Class-D amplifier, wherein during the steady state, the first additional switching circuit and the second additional switching circuit are kept on by the amplifier controller, the Class-D amplifier. Claim 10 A Public Address (PA) system comprising a power supply unit and a Class-D amplifier according to any one of claims 1, 2 and 4 through 9, wherein the power supply unit applies the first DC voltage and the second DC voltage to the Class-D amplifier through the first voltage terminal and the second voltage terminal, respectively.

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