Switching amplifier circuit

Abstract

A switching amplifier circuit for driving an inductive load, the switching amplifier circuit comprising a modulator circuit and an output stage circuit, wherein the switching amplifier circuit is configured to: when the modulator circuit outputs a modulated output signal that produces a ripple current in a load: adjust a switching frequency of the modulator circuit within a predetermined frequency range; monitoring a power of the switching amplifier circuit while adjusting the switching frequency within the predetermined frequency range; and selecting a frequency within the predetermined frequency range at which the monitored power meets a predefined criterion as an operating switching frequency of the modulator circuit.

Description

Technical Field

[0001] The present disclosure relates to switching amplifier circuits. In particular, the present disclosure relates to switching amplifier circuits with reduced power consumption. Background Art

[0002] Switching amplifier circuits, such as class D amplifier circuits, are commonly used to drive inductive loads in various electronic devices, such as output transducers (such as speakers), actuators (eg, resonant actuators such as linear actuators), and motors.

[0003] In some amplifier systems, a filter circuit is provided between the output of the switching amplifier circuit and the transducer to be driven to filter out signal components at the switching frequency of the switching amplifier circuit.

[0004] Other systems (sometimes referred to as filterless switching amplifiers) do not include any such filter circuitry, but instead rely on the inductance of the load to filter out the switching frequency signal component.

[0005] Figure 1 is a schematic diagram of a filterless switching amplifier circuit. Figure 1 The filterless switching amplifier circuit shown generally at 100 in FIG. 1 includes a switching amplifier circuit 110, such as a pulse width modulation (PWM) amplifier circuit, configured to receive an input signal Sin and output a drive signal Sout to an inductive load 120, such as a transducer (e.g., a speaker or a resonant actuator) or a motor, which is Figure 1 1 is represented as a series combination of a resistor 122 and an inductor 124. The drive signal Sout may be a voltage signal that switches between two or more different discrete voltage levels.

[0006] A characteristic of switching amplifier based systems driving inductive loads is ripple current, which is generated by the switching voltage present at the load terminals during operation of the amplifier circuit due to the interaction between the drive signal Sout and the load inductance. Figure 2 This is illustrated in Figure 1, which shows the switching voltage at the terminals of the load varying over time. As can be seen, during the positive pulse of the switching voltage, the current in the load inductance increases. During the negative pulse of the switching voltage, the current in the load inductance decreases. The change in the load current di / dt depends on the magnitude of the switching voltage V and the load inductance L as follows:

[0007] di / dt=V / L (1).

[0008] This varying load current is called ripple current and is undesirable because the ripple current represents out-of-band power loss in the load.

[0009] exist Figure 1In the filter-free switching amplifier circuit of the type shown, the switching frequency F0 is typically much higher than the maximum expected bandwidth of the signal output by the load 120, so that the averaged or filtered drive signal Sout represents the desired output signal with sufficient resolution. In some applications, the switching frequency F0 can be significantly reduced without adversely affecting the resolution of the signal output by the load 120.

[0010] Reducing the switching frequency may have the effect of reducing switching losses in the amplifier circuit 110 because the energy lost per unit time in the output stage driver of the amplifier circuit 110 and / or in the gate capacitance of the transistors (e.g., field effect transistors or FETs) of the output stage driver is reduced. As will be appreciated by one of ordinary skill in the art, capacitive power loss P CAP It can be expressed as

[0011]

[0012] Where C is the capacitance (e.g., the gate capacitance of the output stage transistor), F0 is the switching frequency, and V is the switching voltage developed across the capacitance.

[0013] Therefore, reducing the switching frequency F0 will have the effect of reducing the capacitive power losses in the amplifier circuit 110 .

[0014] In addition, assuming that the time that the output-stage transistor operates in its active region within each cycle of the output signal Sout is the same for all switching frequencies, the resistive power loss of the output-stage transistor caused by the load current (for example, the power loss due to the load current and the drain resistance of the output-stage transistor) can also be reduced by reducing the switching frequency F0, because at a lower switching frequency, the output-stage transistor does not pass through its active region as many times per unit time as at a higher switching frequency.

[0015] However, for a load of given inductance, reducing the switching frequency will increase the ripple current in the load, resulting in an increase in the ripple power delivered to the load.

[0016] According to the above formula (1), the ripple current di can be expressed as:

[0017] di=dt(V / L), (3)

[0018] Wherein dt is equal to the duty cycle of the output signal Sout multiplied by the inverse of the switching frequency F0 of the amplifier circuit 110 (and therefore also the inverse of the drive signal Sout), that is, dt=duty cycle*1 / F0.

[0019] As will be appreciated, the ripple current di is therefore inversely proportional to the switching frequency F0.

[0020] Therefore, in applications with lower output signal bandwidth, capacitive and / or resistive losses (and hence power consumption) can be reduced by reducing the switching frequency F0, but this is at the expense of increased losses due to ripple current in the load.

[0021] Therefore, in order to optimize the power consumption in such applications, it is desirable to find a switching frequency F0 at which, for a given load, a balance can be achieved between reduced capacitive and / or resistive losses and increased ripple current losses to reduce power consumption to a minimum or optimal level. As will be appreciated by those skilled in the art, the switching frequency F0 at which power consumption is minimized will be different for different loads because it depends on the inductance of the load. Summary of the invention

[0022] According to a first aspect, the present invention provides a switching amplifier circuit for driving an inductive load, the switching amplifier circuit comprising:

[0023] a modulator circuit; and

[0024] An output stage circuit, wherein the switching amplifier circuit is configured as:

[0025] When the modulator circuit outputs a modulated output signal that produces a ripple current in the load:

[0026] adjusting a switching frequency of the modulator circuit within a predetermined frequency range;

[0027] monitoring power of the switching amplifier circuit while adjusting the switching frequency within a predetermined frequency range; and

[0028] A frequency within a predetermined frequency range is selected as the operating switching frequency of the modulator circuit, at which frequency within the predetermined frequency range the monitored power meets a predefined criterion.

[0029] The monitored power may include input power to the amplifier circuit, and the switching amplifier circuit may further include an input power monitoring circuit for monitoring the input power.

[0030] The circuit may be configured to select as the operating switching frequency a frequency within a predetermined range at which a minimum monitored input power of the switching amplifier circuit occurs.

[0031] The input power monitoring circuit may include an input current monitoring circuit for monitoring an input current of the switching amplifier circuit.

[0032] The input power monitoring circuit may also include an input voltage monitoring circuit for monitoring an input voltage of the switching amplifier circuit.

[0033] The modulator circuit may include a class D modulator circuit operable in a class BD mode of operation or a class AD mode of operation.

[0034] The output stage circuit may include a single-ended output stage circuit.

[0035] The modulator circuit may be operated in either its class AD mode or its class BD mode to output a modulated output signal that produces a ripple current in the load.

[0036] The output stage circuit may include a differential output stage circuit.

[0037] The modulator circuit is operable in its class AD mode to output a modulated output signal that produces a ripple current in the load.

[0038] The switching amplifier circuit may also include a pilot or test signal generator circuit operable to supply a pilot or test signal to an input of the modulator circuit. The output stage circuit may include a differential output stage circuit, and the modulator circuit may be operated in its class BD mode to output a modulated output signal that produces a ripple current in the load based on the pilot or test signal.

[0039] Pilot or test signals may include:

[0040] a sinusoidal signal having predefined amplitude and / or frequency and / or phase characteristics;

[0041] a variable amplitude sinusoidal signal; or

[0042] A DC signal of fixed or variable amplitude.

[0043] In some examples, the switching amplifier circuit can be configured to have zero PWM switching when idle, and the switching amplifier circuit can also include a pilot or test signal generator circuit that is operable to supply a pilot or test signal to an input of the modulator circuit. The modulator circuit is operable to output a modulated output signal that produces a ripple current in the load based on the pilot or test signal.

[0044] In some examples, the switching amplifier circuit can be configured to have zero PWM switching when idle, and the switching amplifier circuit can include a multi-mode modulator circuit. The modulator circuit is operable to change its operating mode to output a modulated output signal that produces a ripple current in the load when no input signal is present.

[0045] The monitored power may include an output power of the amplifier circuit, and the switching amplifier circuit may further include a load ripple current power monitoring circuit for monitoring the output power. The switching amplifier circuit may be configured to select a frequency within a predetermined range as the operating switching frequency, at which frequency within the predetermined range a minimum monitored output power of the switching amplifier circuit occurs.

[0046] The load ripple current power monitoring circuit may include a load current monitoring circuit and a load voltage monitoring circuit.

[0047] The switching amplifier circuit is operable to change the operating mode of the modulator circuit based on characteristics or parameters of the input signal of the switching amplifier, and the operating switching frequency can be selected at least in part based on the average input power of the class AD operating mode and the class BD operating mode varying over time.

[0048] The switching amplifier circuit is operable to change an operating mode of the modulator circuit based on a characteristic or parameter of an input signal to the switching amplifier, and the switching amplifier circuit may be configured to adjust an operating switching frequency based on a current or future operating mode of the modulator circuit.

[0049] The modulation index of the modulated output signal may be variable.

[0050] The switching amplifier circuit may further include a load impedance detector circuit configured to detect an impedance of the load, and the switching amplifier circuit may be operable to adjust an operating switching frequency based on a difference between the detected impedance of the load and a reference impedance of the load.

[0051] The reference impedance of the load may include a stored predefined impedance value or a stored calibrated impedance value determined during calibration of the switching amplifier circuit.

[0052] The load impedance detector circuit may be configured to detect the impedance of the load based on a voltage across the load and a current flowing through the load when a pilot or test signal of a predetermined frequency is input to the modulator circuit.

[0053] The switching amplifier circuit may receive a supply voltage from a power supply external to the switching amplifier circuit.

[0054] The supply voltage may be adjustable based on the detected impedance of the load.

[0055] The switching amplifier circuit can be configured to adjust the switching frequency of the modulator circuit in the following situations:

[0056] during the production process of the switching amplifier circuit; and / or

[0057] upon activation of the switching amplifier circuit; and / or

[0058] In response to a periodic start signal received from a host device incorporating the switching amplifier circuit; and / or

[0059] continuously; and / or

[0060] In response to power consumption of the switching amplifier circuit deviating from a predefined limit; and / or

[0061] in response to a change in one or more characteristics of the load; and / or

[0062] Responsive to changes in operating characteristics of the switching amplifier circuit.

[0063] The modulator circuit may include a pulse width modulator (PWM) circuit.

[0064] The switching amplifier circuit can be configured to monitor power continuously, intermittently, or periodically.

[0065] According to a second aspect, the present invention provides a switching amplifier circuit for driving an inductive load, the switching amplifier circuit comprising:

[0066] Modulator circuit;

[0067] output stage circuit; and

[0068] Power loss comparator circuit,

[0069] wherein the power loss comparator circuit is configured to perform a comparison of the power loss associated with the ripple current in the load with a switching loss model of the switching amplifier circuit,

[0070] And wherein the switching amplifier circuit is configured to control a switching frequency of the modulator circuit based on the comparison.

[0071] The switching amplifier circuit may also include an output power detector circuit configured to generate a signal indicative of power loss associated with the ripple current.

[0072] The power losses associated with the ripple current in the load may be based on a ripple power loss model for the switching amplifier circuit.

[0073] According to a third aspect, the invention provides an integrated circuit comprising a switching amplifier circuit according to the first aspect.

[0074] According to a fourth aspect, the present invention provides a host device comprising the switching amplifier circuit according to the first aspect.

[0075] The host device may include a laptop, notebook, netbook or tablet computer, a gaming device, a game console, a controller for a gaming console, a virtual reality (VR) or augmented reality (AR) device, a mobile phone, a portable audio player, a portable device, an accessory device for use with a laptop, notebook, netbook or tablet computer, a gaming device, a game console, a VR or AR device, a mobile phone, a portable audio player, or other portable device. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Embodiments of the invention will now be described, strictly by way of example only, with reference to the accompanying drawings, in which:

[0077] Figure 1 is a schematic diagram of a filterless switching amplifier circuit;

[0078] Figure 2 shows the ripple current in an inductive load due to the interaction between the switching voltage applied to the load and the load inductance;

[0079] Figure 3 is a schematic diagram of an example switching amplifier circuit according to the present disclosure;

[0080] Figure 4 Is suitable for Figure 3 A schematic diagram of an example single-ended output stage circuit of a switching amplifier circuit;

[0081] Figure 5 Shows Figure 4 The output voltage of a single-ended amplifier circuit varies over time;

[0082] Figure 6 Is suitable for Figure 3 A schematic diagram of an example differential output stage circuit of a switching amplifier circuit;

[0083] Figure 7a Shows Figure 6 The differential output voltage of the differential output stage circuit varies with time when driven by a class AD modulated signal;

[0084] Figure 7b Shows Figure 6 The differential output voltage of the differential output stage circuit varies with time when driven by a class BD modulated signal;

[0085] Figure 8 is a schematic diagram of an alternative example switching amplifier circuit according to the present disclosure;

[0086] Fig. 9 is a schematic diagram of another alternative example switching amplifier circuit according to the present disclosure;

[0087] Fig.10 is a schematic diagram of another alternative example switching amplifier circuit according to the present disclosure;

[0088] Fig.11 is a schematic diagram of another alternative example switching amplifier circuit according to the present disclosure; and

[0089] Fig.12 is a schematic diagram of another alternative example switching amplifier circuit according to the present disclosure. DETAILED DESCRIPTION

[0090] The present disclosure relates to switching amplifier circuits, and in particular, to switching amplifier circuits capable of selecting an operating switching frequency at which power consumption of the amplifier circuit is optimized, minimized, or at least reduced.

[0091] Reference now Figure 3 An example switching amplifier circuit for driving an inductive load 120 , such as an audio transducer (eg, a speaker, etc.), a tactile transducer (eg, a resonant actuator such as a linear resonant actuator), or a motor is generally shown at 300 .

[0092] In this example, switching amplifier circuit 300 includes modulator circuit 310 , output stage circuit 320 , switching frequency generator circuit 340 , power dissipation manager circuit 350 , and input power monitoring circuit 360 .

[0093] The modulator circuit 310 is configured to receive the amplifier input signal Sin and generate a modulated output signal Smod, which is output to the output stage circuit 320. The modulator circuit can be, for example, a pulse width modulator circuit configured to generate a pulse width modulation (PWM) modulator output signal Smod. The modulator circuit 310 can include a class AD modulator circuit, a class BD modulator circuit, or a multi-mode modulator circuit that can selectively operate in a class AD mode or a class BD mode.

[0094] The output stage circuit 320 is configured to generate one or more switching voltage output signals based on the modulator output signal Smod for driving the load 120. Figure 4 and Figure 6 An example topology of the output stage circuit 320 is described in more detail.

[0095] The modulator circuit 310 and the output stage circuit 320 receive a supply voltage from a supply voltage rail 330. A current sense resistor 332 is provided in the supply rail to allow monitoring of the current consumed by the modulator circuit 310 and the output stage circuit 320, as will be described in more detail below.

[0096] Switching frequency generator circuit 340 is configured to generate an output signal that defines a switching frequency of modulator circuit 310. In some examples, switching frequency generator circuit 340 can be configured to output a reference signal to modulator circuit 310, where the frequency of the output reference signal defines the switching frequency of modulator circuit 310. In other examples, modulator circuit 310 can include its own internal reference frequency generator, and switching frequency generator circuit 340 can output a control signal to cause modulator circuit 310 to select or adjust the frequency of its internal reference signal.

[0097] The power dissipation manager circuit 350 is configured to control the switching frequency generator circuit 340 based on an indication of input power to the modulator circuit 310 and the output stage circuit 320 , the input power monitoring circuit 360 supplying the input power to the power dissipation manager circuit 350 .

[0098] Switching amplifier circuit 300 also includes a voltage sense amplifier circuit 370 having an input coupled to supply voltage rail 330 and an output coupled to a first input of input power monitoring circuit 360. Thus, voltage sense amplifier circuit 370 is configured to output a signal (e.g., a voltage) indicative of the voltage of supply voltage rail 330, and thus output a voltage supplied to modulator circuit 310 and output stage circuit 320.

[0099] Switching amplifier circuit 300 also includes a current sense amplifier circuit 380 having first and second inputs coupled to respective first and second terminals of current sense resistor 332 and an output coupled to a second input of input power monitoring circuit 360. Thus, current sense amplifier circuit 380 is configured to output a signal (e.g., a voltage) indicative of a current in supply voltage rail 330, and thus an input current to a combination of modulator circuit 310 and output stage circuit 320.

[0100] The input power monitoring circuit 360 is configured to generate a signal indicative of the input power of the modulator circuit 310 and the output stage circuit 320 based on the signals received from the voltage sense amplifier circuit 370 and the current sense amplifier circuit 380 .

[0101] To determine the switching frequency F0 of the modulator circuit 310 that balances the reduced capacitive and / or resistive losses with the increased ripple current losses, the power dissipation manager circuit 350 outputs appropriate control signals to trigger a power optimization sequence.

[0102] During the power optimization sequence, a modulated output signal Smod is output by the modulator circuit 310 to cause the output stage circuit 320 to output an output signal that causes a ripple current in the load 120. When the switching frequency of the modulator circuit 310 is adjusted within a predefined frequency range by the switching frequency generator circuit 340, the power consumption manager circuit 350 monitors a signal indicative of the input power. For example, the switching frequency generator circuit 340 may automatically scan the predefined frequency range.

[0103] The power consumption manager circuit 350 identifies a switching frequency within a predefined frequency range at which a minimum input power level occurs (as indicated by a signal indicating input power), and the power consumption manager circuit 350 selects the identified switching frequency as the operating switching frequency of the modulator circuit 310 for subsequent operation of the switching amplifier circuit 300.

[0104] Monitoring input power while adjusting the switching frequency during a power optimization sequence in this manner ensures that all amplifier and load interactions are considered when selecting the operating switching frequency to optimize, minimize, or at least reduce power consumption. Such interactions may include, for example, load ripple losses, load hysteresis losses, amplifier switching losses, parasitic capacitance losses, and the like.

[0105] For some configurations of the modulator circuit 310 and the output stage circuit 320, the modulator circuit 310 will output a modulated output signal Smod, which causes a switching voltage to be output to the load 120 when the switching amplifier circuit 300 is in an idle state, that is, when no input signal Sin is supplied to the modulator circuit 310.

[0106] Figure 4 Shown as Figure 3 An example single-ended output stage circuit of the output stage circuit 320 in the switching amplifier circuit 300 is shown.

[0107] like Figure 4 4, a single-ended output stage circuit includes first and second complementary switches 410, 420 (P-channel and N-channel MOSFET devices, respectively, in this example) coupled between a supply voltage rail 430 and a ground (or other reference voltage) supply rail 440.

[0108] A first terminal of the load 120 is coupled to a node 412 between the first and second switches 410, 420 and a ground rail 440. The input terminals of the switches 410, 420 receive a modulated input signal based on the modulated signal Smod output by the modulator circuit 310, and an output voltage VLoad is formed across the load 120 as the switches 410, 420 switch in response to the received modulated input signal.

[0109] Figure 5 4 shows the output voltage VLoad of the output stage 400 varying over time when the switching amplifier circuit 300 is idle. As can be seen, regardless of whether the modulator circuit 310 outputs a class AD modulated output signal or a class BD modulated output signal, even if there is no input signal Sin at the input of the modulator circuit 310, the output voltage VLoad switches between two values ​​(in this example, VSupply and 0V) at each cycle of the switching frequency F0, and thus generates a ripple current when the amplifier circuit 300 is idle.

[0110] Thus, an operating switching frequency that reduces or minimizes power consumption may be identified and selected by monitoring input power and adjusting the switching frequency of the modulator circuit 310 within a predefined range as described above, without applying any input signal Sin during the power optimization sequence.

[0111] Figure 6 An example differential output stage circuit that may be driven by the modulator circuit 310 is shown. Figure 6 600, a differential output stage circuit is configured as an H-bridge output stage, comprising: a first half-bridge 610, the first half-bridge comprising a first switch 612 and a second switch 614 (in this example, P-channel and N-channel MOSFET devices, respectively); and a second half-bridge 620, the second half-bridge comprising a second switch 622 and a third switch 624 (in this example, P-channel and N-channel MOSFET devices, respectively). The first half-bridge 610 and the second half-bridge 620 are coupled between a power supply voltage rail 630 and a ground (or other reference voltage) rail 640.

[0112] The load 120 is coupled in a bridge-tied load configuration between a node A 616 of the first half-bridge 610 and a node B 626 of the second half-bridge 620. The input terminals of the switches 612, 614, 622, 624 receive a modulated input signal based on the modulated signal Smod output by the modulator circuit 310, and an output voltage VLoad is formed across the load 120 as the switches 612, 614, 622, 624 switch in response to the received modulated input signal.

[0113] Figure 7a The output voltage VLoad of the output stage circuit 600 is shown varying over time when the switching amplifier circuit 300 is idle when the modulator circuit 310 operates to output a class AD modulated output signal having a 50% duty cycle.

[0114] like Figure 7aAs shown, when the output stage circuit 600 is driven by a class AD modulated signal (wherein the amplifier is idle), even when there is no input signal Sin at the input of the modulator circuit 310, the magnitude of the differential output voltage VLoad generated across the load 120 is always +VSupply or -VSupply, and switches between these two values ​​in each cycle of the switching frequency F0, and therefore a ripple current is generated when the amplifier circuit 300 is idle.

[0115] Thus, an operating switching frequency that reduces or minimizes power consumption may be identified and selected by monitoring input power and adjusting the switching frequency of the modulator circuit 310 within a predefined range as described above, without applying any input signal Sin during the power optimization sequence.

[0116] Figure 7b The output voltage VLoad of the output stage circuit 600 is shown varying over time when the switching amplifier circuit 300 is idle when the modulator circuit 310 operates to output a class BD modulated output signal having a 50% duty cycle.

[0117] like Figure 7b It can be seen that when the output stage circuit 600 is driven by a class BD modulated signal (wherein the amplifier circuit 300 is in idle), the magnitude of the differential output voltage VLoad generated across the load 120 is always 0V, and therefore no ripple current is generated when the amplifier circuit 300 is in idle.

[0118] Therefore, when the modulator circuit 310 is configured as or operated as a class BD modulator, in order to identify and select an operating switching frequency that reduces or minimizes power consumption, it is necessary to supply a pilot or test signal to the modulator circuit 310 as the input signal Sin during the power optimization sequence, or to switch the operating mode of the modulator circuit 310 to the class AD mode before starting the power optimization sequence to ensure that a ripple current is generated in the load 120 before monitoring the input power and adjusting the switching frequency of the modulator circuit 310 within the predefined range as described above.

[0119] Similar considerations apply to switching amplifier circuits with zero PWM switching when idle (i.e., amplifier circuits in which the level of the PWM output signal does not change if there is no input signal). Therefore, if the amplifier circuit 300 is configured to operate in this manner, then in order to identify and select an operating switching frequency that reduces or minimizes power consumption, it is necessary to supply a pilot or test signal as the input signal Sin to the modulator circuit 310 during the power optimization sequence, or to change the operating mode of the modulator circuit 310 (e.g., from a class BD mode to a class AD mode) before starting the power optimization sequence to ensure that a ripple current is generated in the load 120 when there is no input signal before monitoring the input power and adjusting the switching frequency of the modulator circuit 310 within a predefined range as described above.

[0120] Figure 8 is a schematic diagram of an example switching amplifier circuit for driving an inductive load 120, such as an audio transducer (e.g., a speaker, etc.), a tactile transducer (e.g., a resonant actuator, such as a linear resonant actuator), wherein an operating mode of a modulator circuit can be adjusted and a pilot or test signal can be input to the modulator circuit to facilitate identification and selection of an operating switching frequency of the modulator circuit that reduces or minimizes power consumption.

[0121] Figure 8 The switching amplifier circuit shown generally at 800 includes a Figure 3 The switching amplifier circuit 300 has the same multiple components. Such common components are Figure 3 and Figure 8 The common figure marks in the drawings are indicated, and for the sake of clarity and conciseness, they will not be described in detail here.

[0122] Switching amplifier circuit 800 and Figure 3 The switching amplifier circuit 300 of the embodiment of the present invention is different in that it includes a multi-mode modulator circuit 810 that can switch between a class BD mode of operation and a class AD mode of operation in response to a mode control signal output by the power manager circuit 350, and includes a differential output stage circuit 820 (e.g., as described above with reference to FIG. Figure 6 The differential output stage circuit is configured to receive the modulated output signal Smod from the modulator circuit 810 and drive the load 120. The modulator circuit 810 may be, for example, a PWM modulator circuit.

[0123] In addition, the switching amplifier circuit 800 includes a pilot or test signal generator circuit 830 that operates to generate and output a pilot or test signal having a predefined frequency, amplitude, and / or phase characteristic. For example, the pilot or test signal can be a sinusoidal signal of a predefined amplitude and frequency. The frequency of the pilot or test signal can be outside the response band of the load 120 (e.g., above or below the response band) to avoid causing a perceptible effect on a user of a host device incorporating the switching amplifier circuit 800, such as vibration (when the load is a tactile actuator) or an audible frequency component (when the load is a speaker). In addition, the amplitude of the pilot or test signal can be variable, thereby changing the modulation depth of the modulated output signal Smod in a range from 0% to 100%.

[0124] Alternatively, the pilot or test signal may be a DC signal that is selected to have the effect of keeping the switching amplifier circuit 800 in static modulation for a short period of time. In this case, the level or amplitude of the DC signal may be adjusted (e.g., ramped or stepped) up or down over time to avoid any transducer or motor noise associated with DC signals having fast rising edges.

[0125] The output of pilot or test signal generator circuit 830 may be coupled to the input of modulator circuit 810 via switch 840 .

[0126] Therefore, the switching amplifier circuit 800 can operate in a normal operation mode, where the modulator circuit 810 operates in a class BD mode to generate a class BD modulated output signal based on the received input signal Sin and output the class BD modulated output signal Smod to the output stage circuit 820.

[0127] The switching amplifier circuit 800 may also operate in a first operating switching frequency selection mode in which the switch 840 is closed and the pilot or test signal generator circuit 830 is enabled (e.g., in response to a suitable control signal output by the power consumption manager circuit 350) to output a pilot or test signal to the input of the modulator circuit 810. The first operating switching frequency selection mode may be used in a power optimization sequence to ensure that a ripple current is generated in the load 120, thereby allowing identification and selection of an operating switching frequency for the modulator circuit 810 that minimizes or reduces power consumption.

[0128] The switching amplifier circuit 800 can also operate in a second operating switching frequency selection mode, in which the modulator circuit 810 switches to the class AD mode (e.g., in response to an appropriate control signal output by the power manager circuit 350) to output a class AD modulated signal Smod having a suitable duty cycle (e.g., 50%) to the output stage circuit 820. In this second operating switching frequency selection mode that can be used for power optimization sequences, there is no need to provide a pilot or test signal to the modulator circuit 810 because (as described above with reference to Figure 7a The use of a class AD modulated signal as explained above ensures that even when no input signal Sin is present at the input of the modulator circuit 810, the magnitude of the differential output voltage produced across the load 120 switches between two values ​​within each cycle of the switching frequency F0, and thus a ripple current is generated in the load 120 when the switching amplifier circuit 800 is idle, thereby allowing identification and selection of an operating switching frequency of the modulator circuit 810 that minimizes or reduces power consumption.

[0129] The switching amplifier circuit 800 may operate in a third operating switching frequency selection mode, wherein the modulator circuit 810 is switched to the class AD mode (e.g., in response to an appropriate control signal output by the power manager circuit 350) to output the class AD modulated signal Smod to the output stage circuit 820, and the pilot or test signal generator circuit 830 is enabled and the switch 840 is closed (e.g., in response to an appropriate control signal output by the power manager circuit 350) to output a pilot or test signal to the input of the modulator circuit 810. Again, by executing the power optimization sequence described above, this allows identification and selection of an operating switching frequency for the modulator circuit 810 that minimizes or reduces power consumption.

[0130] As will be appreciated by one of ordinary skill in the art, when the modulator circuit 810 is configured as or operated as a class BD modulator, in order to facilitate identification and selection of an optimal or beneficial operating switching frequency for the modulator circuit 810 by monitoring input power as described above, it is sufficient to simply switch the modulator circuit 810 to its class AD operating mode and monitor the input power consumption when the switching frequency is changed (wherein the switching amplifier circuit 800 is idle), or to supply a pilot or test signal to the modulator circuit 810 and monitor the input power consumption when the switching frequency is changed and the pilot or test signal is supplied to the modulator circuit 810.

[0131] Thus, in some examples, the pilot or test signal generator circuit 830 and associated switch 840 may be omitted, and the modulator circuit 810 may selectively operate in either the Class BD mode or the Class AD mode as described above.

[0132] In other examples, the modulator circuit 810 may operate only in the Class BD mode, and a pilot or test signal generator circuit 830 and a switch 840 may be provided and selectively operable to supply a pilot or test signal to the input of the modulator circuit 810 as described above.

[0133] As referenced above Figure 7b As explained above, Figure 8 For a switching amplifier circuit of the type described, which uses a multi-mode modulator circuit 810 and a differential output stage circuit 820, when the switching amplifier circuit 800 is idle (i.e., when the modulator circuit 810 has no input signal Sin) and the modulator circuit 810 is operating in its class BD mode, there is no differential voltage across the load 120. Therefore, for each signal level transition in the output signal supplied to the load 120, power is dissipated only in the common-mode capacitance ( Figure 6 Marked as C CM ). In contrast, when the switching amplifier circuit delivers power to the load 120 (where the modulator circuit 810 is operating in its class BD mode) (i.e., when the input signal Sin is present), the power is dissipated as ripple current in the common-mode capacitor C CM and differential mode capacitance (at Figure 6 Marked as C diff ) and load 120.

[0134] Therefore, when the switching amplifier circuit is idle (where the modulator circuit 810 is operating in its class AD mode), selecting the operating switching frequency based on the minimum observed input power may not account for the capacitive losses that occur during normal operation of the switching amplifier circuit (i.e., when the input signal Sin is present) (where the modulator circuit 810 is operating in its class BD mode). Therefore, for all operating modes of the modulator circuit 810, the selected operating switching frequency may not provide an optimal balance between capacitive power losses and load ripple current power losses.

[0135] In order to improve the selection of the operating switching frequency to provide a better balance between capacitive power losses and load ripple current power losses, the input power of the modulator circuit 810 and the output stage circuit 820 can be monitored (via the input power monitoring circuit 360) when the switching frequency is adjusted within a predefined range (where the modulator circuit 810 operates in its class AD mode and its class BD mode). The method will generate: a first power consumption reference curve or characteristic, which defines the relationship between the switching frequency and the input power when the modulator circuit 810 operates in the class AD mode; and a second power consumption reference curve or characteristic, which defines the relationship between the switching frequency and the input power when the modulator circuit 810 operates in the class BD mode. The operating switching frequency can then be selected based on the expected modulation scheme of the switching amplifier circuit.

[0136] For example, where a switching amplifier circuit operates to change the operating mode of a modulator circuit based on a characteristic or parameter such as a signal level of an input signal Sin, the operating switching frequency may be selected based on the expected average modulation, for example based on (at least in part) the average input power that varies over time for both the class AD mode and the class BD mode, such that the selected operating switching frequency is not optimized for either mode but instead results in reduced power consumption in both the class AD mode and the class BD mode.

[0137] In addition, determining the power consumption reference curve or characteristic for both the class AD mode of operation and the class BD mode of operation allows the amplifier circuit to dynamically adjust the operating switching frequency according to the current or future operating mode of the modulator circuit. For example, when the switching amplifier circuit operates to change the operating mode of the modulator circuit between the class AD and class BD modes based on a parameter such as the signal level of the input signal Sin, if the input signal parameter is monitored (e.g., by the power consumption manager circuit 350), the appropriate operating switching frequency can be selected before or while changing the operating mode of the modulator circuit 810.

[0138] To further improve the selection of an operating switching frequency that minimizes or reduces power consumption, in addition to adjusting the switching frequency, the modulation index of the modulated output signal Smod may be adjusted while monitoring the input power to the modulator circuit 810 and the output stage circuit 820 via the input power monitoring circuit 360. For example, a pilot or test signal may be supplied to the input of the modulator circuit 810 via the pilot or test signal generator 830, and the amplitude of the signal may be adjusted continuously or in discrete steps to adjust the modulation index of the modulated output signal Sout between 0% (i.e., an idle state of the modulator circuit 810 with no input signal) and 100% (i.e., maximum differential load power).

[0139] In this way, a set of additional power consumption reference curves or characteristics defining the relationship between switching frequency and input power at different modulation indices can be determined, and the set of additional power consumption reference curves or characteristics are then used to select an optimal or at least beneficial operating switching frequency that balances the switching power losses for a given modulation index with the load ripple current power losses.

[0140] For example, selection of an operating switching frequency taking into account the modulation index may be performed as part of a calibration or startup sequence of a switching amplifier circuit.

[0141] In the above example, when the switching frequency of the modulator circuit is adjusted during a power optimization sequence (wherein the amplifier circuit is in an idle state or a pilot or test signal is supplied to the modulator circuit), the input power of the modulator circuit and the output stage circuit of the switching amplifier circuit is monitored to identify and select an optimal or beneficial operating switching frequency of the modulator circuit that minimizes or at least reduces the power consumption of the switching amplifier circuit.

[0142] In other examples, when adjusting the switching frequency of the modulator circuit during a power optimization sequence (wherein the amplifier circuit is in an idle state or a pilot or test signal is supplied to the modulator circuit), the power associated with the load ripple current can be measured or estimated, for example based on measurements of the load current and voltage, to identify and select an optimal or beneficial operating switching frequency for the modulator circuit that minimizes or at least reduces the power consumption of the switching amplifier circuit.

[0143] Fig. 9 is a schematic diagram of another example switching amplifier circuit for driving an inductive load 120 , such as an audio transducer (eg, a speaker, etc.), a tactile transducer (eg, a resonant actuator, such as a linear resonant actuator).

[0144] Fig. 9 The switching amplifier circuit shown generally at 900 includes a Figure 8 The switching amplifier circuit 800 has the same multiple components. Such common components are Figure 8 and Fig. 9 The common figure marks in the drawings are indicated, and for the sake of clarity and conciseness, they will not be described in detail here.

[0145] The switching amplifier circuit 900 differs from the switching amplifier circuit 800 in that it also includes a load ripple power detector circuit 910, an output current sensing amplifier circuit 920 (which has an output coupled to a first input of the load ripple power detector circuit 910), an output current sensing resistor 922, and an output voltage sensing amplifier circuit 930 (which has an output coupled to a second input of the load ripple power detector circuit 910).

[0146] exist Fig. 9 In the example circuit shown, the output stage circuit 820 includes a differential output stage circuit (eg, as described above with reference to FIG. Figure 6 ), which has a first output signal path 942 and a second output signal path 944 for coupling the first output and the second output of the output stage circuit 820 to the respective first terminal and the second terminal of the load 120. However, it will be understood by those skilled in the art that the output stage circuit 820 can also be a single-ended output stage circuit (e.g., as described above with reference to Figure 4The type described above has only a first output signal path 942 for coupling the output of the output stage circuit to a first terminal of a load 120, while a second terminal of the load 120 is coupled to ground or some other suitable reference voltage source.

[0147] An output current sense resistor 922 is disposed in the first output signal path 942 , and a first input and a second input of the output current sense amplifier circuit 920 are coupled to respective first and second terminals of the output current sense resistor 922 .

[0148] Thus, the output current sense amplifier circuit 920 is configured to output a signal (eg, a voltage) indicative of the current in the first output signal path 942 (and therefore flowing through the load 120 ) to the first input of the load ripple power detector circuit 910 .

[0149] The first input and the second input of the output voltage sense amplifier circuit 930 are coupled to the first output signal path 942 and the second output signal path 944, respectively, so that the output voltage sense amplifier circuit is configured to output a signal (e.g., a voltage) indicative of the output voltage across the load 120. (In an alternative example in which the output stage circuit 320 is single-ended, the output voltage sense amplifier circuit 930 may have only a single input coupled to the output signal path from the output stage circuit 320 to the load 120.)

[0150] Thus, the output voltage sense amplifier circuit 930 is configured to output a signal (eg, a voltage) indicative of the voltage across the load 120 to the second input of the load ripple power detector circuit 910 .

[0151] The switching amplifier circuit 900 may be operated in a first operating switching frequency selection mode to execute a power optimization sequence to identify and select an operating switching frequency for the modulator circuit 810. In the first operating switching frequency selection mode, the switch 840 is closed and the pilot or test signal generator circuit 830 is enabled (e.g., in response to a suitable control signal output by the power consumption manager circuit 350) to output a pilot or test signal to the input of the modulator circuit 810. As described above, this ensures that ripple current flows in the load 120 when the modulator circuit 810 is operating in its Class BD mode.

[0152] When a pilot or test signal is output to the input of modulator circuit 810 , the switching frequency of modulator circuit 310 is adjusted within a predefined frequency range by switching frequency generator circuit 340 (eg, in response to an appropriate control signal output by power manager circuit 350 ).

[0153] Alternatively, the switching amplifier circuit 900 may be operated in a second operating switching frequency selection mode to execute a power optimization sequence to identify and select an operating switching frequency for the modulator circuit 810. In the second operating switching frequency selection mode, the modulator circuit 810 is switched to a class AD operating mode, and no input signal is supplied to the input of the modulator circuit 810 (i.e., the switching amplifier circuit 900 is idle). As explained above, when the modulator circuit 810 is operating in its class AD mode, a ripple current may flow in the load 120 even if the modulator circuit 810 has no input signal.

[0154] When the switching amplifier circuit 900 operates in the first or second operating switching frequency selection mode, the output current sensing amplifier circuit 920 outputs a load current signal (e.g., voltage) indicating the current flowing through the load 120 to the first input of the load ripple power detector circuit 910, and the output voltage sensing amplifier circuit 930 outputs a load voltage signal (e.g., voltage) indicating the voltage across the load 120 to the second input of the load ripple power detector circuit 910.

[0155] The load ripple power detector circuit 910 determines the power associated with the load ripple current based on the signals received from the output current sense amplifier circuit 920 and the output voltage sense amplifier circuit 930 (e.g., by multiplying the load current signal by the load voltage signal), and outputs a signal indicating the power associated with the load ripple current to the power consumption manager circuit 350.

[0156] To facilitate this determination of the power associated with the load ripple, the output current and voltage sense amplifier circuits 920, 930 may include a filter circuit (e.g., a high pass filter circuit) configured to pass only signal components of the load current and voltage signals associated with the high frequency load ripple current. Alternatively, a separate filtering circuit may be provided in the signal path between the output stage circuit 820 and the load ripple power detector circuit 910 for this purpose.

[0157] The power manager circuit 350 monitors the signal indicating the power associated with the load ripple current as the switching frequency changes, and identifies the switching frequency at which the minimum load ripple power level occurs within the predefined frequency range. The identified switching frequency is selected by the power manager circuit 350 as the operating switching frequency of the modulator circuit 310 for subsequent operation of the switching amplifier circuit 300.

[0158] When the switching frequency is adjusted in this manner, monitoring the power associated with the load ripple current allows accurate estimation of the power losses associated with the load ripple current, and thus selecting an operating switching frequency that minimizes this power is an effective method for optimizing or at least reducing power consumption in the switching amplifier circuit 900.

[0159] In some cases, it may be beneficial to monitor the impedance of the load 120 to detect differences between the actual load impedance and the rated or nominal impedance of the load 120. Such differences may arise due to, for example, changes in load temperature or load aging. Monitoring the load impedance allows the operating switching frequency to be selected or adjusted to compensate for any such changes in the load impedance, thereby optimizing, minimizing, or at least reducing the power consumption of the switching amplifier circuit.

[0160] Fig.10 is a schematic diagram of another example switching amplifier circuit for driving an inductive load 120 (such as an audio transducer (e.g., a speaker, etc.), a tactile transducer (e.g., a resonant actuator, such as a linear resonant actuator)), which includes a circuit for monitoring the impedance of the load.

[0161] Fig.10 A switching amplifier circuit, shown generally at 1000, includes a Figure 8 The switching amplifier circuit 800 has the same multiple components. Such common components are Figure 8 and Fig.10 The common figure marks in the drawings are indicated, and for the sake of clarity and conciseness, they will not be described in detail here.

[0162] Switching amplifier circuit 1000 differs from switching amplifier circuit 800 in that it also includes a load impedance detector circuit 1010, an output current sensing amplifier circuit 1020 (which has an output coupled to a first input of the load impedance detector circuit 1010), an output current sensing resistor 1022, and an output voltage sensing amplifier circuit 1030 (which has an output coupled to a second input of the load impedance detector circuit 1010).

[0163] exist Fig.10 In the example circuit shown, the output stage circuit 820 includes a differential output stage circuit (eg, as described above with reference to FIG. Figure 6 1042 and 1044 for coupling the first and second outputs of the output stage circuit 820 to the respective first and second terminals of the load 120. However, it will be appreciated by those skilled in the art that the output stage circuit 820 may also be a single-ended output stage circuit (e.g., as described above with reference to Figure 4The type described above has only a first output signal path 1042 for coupling the output of the output stage circuit to a first terminal of a load 120, while a second terminal of the load 120 is coupled to ground or some other suitable reference voltage source.

[0164] The output current sense resistor 1022 is disposed in the first output signal path 1042 , and the first and second inputs of the output current sense amplifier circuit 1020 are coupled to respective first and second terminals of the output current sense resistor 1022 .

[0165] Thus, the output current sense amplifier circuit 1020 is configured to output a signal (eg, a voltage) indicative of the current in the first output signal path 1042 (and therefore flowing through the load 120 ) to the first input of the load ripple power detector circuit 1010 .

[0166] The first input and the second input of the output voltage sense amplifier circuit 1030 are coupled to the first output signal path 1042 and the second output signal path 1044, respectively, so that the output voltage sense amplifier circuit is configured to output a signal (e.g., a voltage) indicative of the output voltage across the load 120. (In an alternative example in which the output stage circuit 820 is single-ended, the output voltage sense amplifier circuit 930 may have only a single input coupled to the output signal path from the output stage circuit 820 to the load 120.)

[0167] Thus, the output voltage sense amplifier circuit 1030 is configured to output a signal (eg, a voltage) indicative of the voltage across the load 120 to the second input of the impedance detector circuit 1010 .

[0168] The impedance detector circuit 1010 is configured to determine the impedance of the load 120 based on signals received from the output current sense amplifier circuit 1020 and the output voltage sense amplifier circuit 1030 while supplying a pilot or test signal to the modulator circuit 810, and output a signal indicating the impedance of the load 120 to the power consumption manager circuit 350.

[0169] In operation of the switching amplifier circuit 1000, a power optimization sequence of the type described above is performed to select an initial operating switching frequency for the modulator circuit 810 based on the monitored input power to the modulator circuit 810 and the output stage circuit 820. As described above, the power optimization sequence may involve switching the modulator circuit 810 to a class AD operating mode and / or supplying a pilot or test tone to the modulator circuit 810 to ensure that a ripple current is generated in the load when the switching frequency is adjusted, and monitoring the input power by the power consumption manager circuit 350 to identify a switching frequency that optimizes, minimizes, or at least reduces power consumption.

[0170] Once the power optimization sequence has been completed and the initial operating switching frequency has been selected, the modulator circuit 810 will switch to its Class BD operating mode as necessary (e.g., in response to an appropriate control signal from the power manager circuit 350), and the pilot or test signal generator circuit 830 is enabled and the switch 840 is closed (e.g., in response to an appropriate control signal from the power manager circuit 350). Thus, the pilot or test signal is supplied to the modulator circuit 810, which in turn outputs a modulated output signal Smod to the output stage circuit 820. The pilot or test tone may be supplied to the input of the modulator circuit 810 in addition to the input signal Sin, or may be supplied to the input of the modulator circuit 810 in the absence of the input signal Sin, e.g., by isolating the input of the modulator circuit 810 from the input signal terminal of the switching amplifier circuit 1000 via a switch in the input signal path.

[0171] The output stage circuit 820 supplies a drive signal to the load 120, and the output current sense amplifier circuit 1020 outputs a signal indicating the load current to the impedance detector circuit 1010. Similarly, the output voltage sense amplifier circuit 1030 outputs a signal indicating the voltage across the load to the impedance detector circuit 1010. The impedance detector circuit 1010 determines the impedance of the load 120 based on the signals received from the output current sense amplifier circuit 1020 and the output voltage sense amplifier circuit 1030, and outputs a signal indicating the load impedance to the power consumption manager circuit 350.

[0172] In response to the signal indicating the impedance of the load 120, the power consumption manager circuit 350 may compare the detected load impedance with a stored reference load impedance. The reference load impedance may be, for example, a reference load impedance value determined based on the outputs of the output current sense amplifier circuit 1020 and the output voltage sense amplifier circuit 1030 during an initial calibration of the switching amplifier circuit 1000. Alternatively, the reference load impedance may be a nominal or rated impedance value of the load 120 that is stored in a memory (e.g., ROM or RAM) of a host device incorporating the switching amplifier circuit 1000.

[0173] The power consumption manager may output appropriate control signals to adjust the switching frequency F0 of the modulator circuit 810 (which is selected as a result of a power optimization sequence two of the type described above) based on the difference between the detected load impedance and the reference load impedance.

[0174] Additionally or alternatively, the power consumption manager circuit 350 may output a suitable control signal to re-trigger the power optimization sequence to select a new switching frequency F0 based on the difference between the detected load impedance and the reference load impedance.

[0175] For example, if the difference between the detected load impedance and the reference load impedance meets or exceeds a predefined threshold, the power consumption manager circuit 350 may output a control signal to adjust the operating switching frequency and / or trigger a power optimization sequence to select a new operating switching frequency.

[0176] Monitoring the load impedance and adjusting the operating switching frequency in this manner may improve power supply efficiency by optimizing the operating switching frequency for an actual load impedance that may differ from a reference load impedance due to temperature effects, aging, etc.

[0177] Additionally or alternatively, the power manager circuit 350 may be operative to adjust the supply voltage VSupply based on the detected load impedance. For example, if the detected load impedance (or the resistive component of the detected load impedance) is lower than the reference load impedance, the power manager circuit 350 may be operative to reduce the supply voltage VSupply, for example by outputting a suitable control signal to a power source (e.g., a power converter, such as a DC-DC converter) external to the switching amplifier circuit that provides the supply voltage VSupply. This may have the effect of improving the power efficiency of the power converter without reducing the power delivered to the load.

[0178] In some cases, characteristics such as the impedance of the load may be unknown or may be variable.

[0179] Fig.11 is a schematic diagram of another example switching amplifier circuit for driving an inductive load 120 (such as an audio transducer (e.g., a speaker, etc.), a tactile transducer (e.g., a resonant actuator, such as a linear resonant actuator)), the other example switching amplifier circuit including circuits for monitoring the voltage across the load and the current flowing through the load.

[0180] Fig.11 A switching amplifier circuit, shown generally at 1100, includes a Figure 3 The switching amplifier circuit 300 has the same multiple components. Such common components are Figure 3 and Fig.11 The common figure marks in the drawings are indicated, and for the sake of clarity and conciseness, they will not be described in detail here.

[0181] Switching amplifier circuit 1100 differs from switching amplifier circuit 300 in that it also includes a load ripple power detector circuit 1110, an output current sense amplifier circuit 1120 having an output coupled to a first input of load ripple power detector circuit 1110, an output current sense resistor 1122, and an output voltage sense amplifier circuit 1130 having an output coupled to a second input of load ripple power detector circuit 1110. Switching amplifier circuit 1100 also includes a power loss comparator circuit 1140 and an amplifier switching loss model 1150.

[0182] exist Fig.11 In the example circuit shown, the output stage circuit 320 includes a single-ended output stage circuit (eg, Figure 4 1) having an output signal path 1142 for coupling the output of the output stage circuit 320 to a first terminal of the load 120, while a second terminal of the load is coupled to ground or some other reference voltage. However, one of ordinary skill in the art will appreciate that the output stage circuit 320 may also be a differential output stage circuit (e.g., as described above with reference to Figure 6 The type described above has only a first output signal path and a second output signal path for coupling the output of the output stage circuit to the first terminal and the second terminal of the load 120.

[0183] An output current sense resistor 1122 is disposed in the output signal path 1142 , and a first input and a second input of the output current sense amplifier circuit 1120 are coupled to respective first and second terminals of the output current sense resistor 1122 .

[0184] Thus, the output current sense amplifier circuit 1120 is configured to output a signal (eg, a voltage) indicative of the current in the output signal path 1142 (and therefore flowing through the load 120 ) to the first input of the load ripple power detector circuit 1110 .

[0185] An input of the output voltage sense amplifier circuit 1130 is coupled to an output signal path 1142 such that the output voltage sense amplifier circuit is configured to output a signal (e.g., a voltage) indicative of the output voltage across the load 120. (In an alternative example in which the output stage circuit 320 is a differential output stage circuit, the output voltage sense amplifier circuit 1130 may have a first input and a second input coupled to respective first and second output signal paths from the output stage circuit 320 to the load 120.)

[0186] Thus, the output voltage sense amplifier circuit 1130 is configured to output a signal (eg, a voltage) indicative of the voltage across the load 120 to the second input of the load ripple power detector circuit 1110 .

[0187] The load ripple power detector circuit 1110 is configured to determine the power associated with the load ripple current based on signals received from the output current sense amplifier circuit 1120 and the output voltage sense amplifier circuit 1130 (e.g., by multiplying the load current signal by the load voltage signal), and output a signal indicating the power associated with the load ripple current to the power consumption comparator circuit 1140.

[0188] The power loss comparator circuit 1140, which may be implemented in a processing circuit such as a digital signal processor (DSP) circuit, is configured to compare the power loss associated with the load ripple current (represented by the signal output by the load ripple power detector circuit 1110) with the modeled switching power loss of the switching amplifier circuit 1100 (represented by the output of the amplifier switching loss model 1150). Based on the comparison, the power loss comparator circuit 1140 outputs a control signal to the switching frequency generator circuit 340 to control the operating switching frequency of the modulator circuit 310 to achieve an optimal or at least improved balance between the amplifier switching loss and the load ripple current loss to optimize, minimize or at least reduce the power consumption of the switching amplifier circuit 1100.

[0189] Amplifier switching loss model 1150 may be stored in a memory (such as ROM or RAM) of a host device incorporating switching amplifier circuit 1100. Amplifier switching loss model 1150 includes: a capacitive switching loss model that models capacitive power losses due to capacitance (e.g., gate capacitance) of switches of output stage circuit 320 and / or parasitic capacitance in switching amplifier circuit 1100; and a resistive switching loss model that models resistive power losses due to switches of output stage circuit 320 passing through their active areas.

[0190] The amplifier switching loss model 1150 receives an input signal representing the current operating switching frequency of the modulator circuit 310 from the switching frequency generator circuit 340, and outputs a signal indicating the sum of the capacitive switching power loss and the resistive switching power loss in the switching amplifier circuit 1100 at the operating switching frequency to the power loss comparator circuit 1140.

[0191] The power loss comparator circuit 1140 compares the sum of the capacitive and resistive switching power losses of the current operating switching frequency with the detected ripple current power loss (as represented by the output of the ripple power loss detector circuit 1110), and outputs a control signal to the switching frequency generator circuit 340 to adjust the operating switching frequency based on the comparison result.

[0192] For example, if the sum of the capacitive and resistive switching power losses is greater than the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to reduce the operating switching frequency. On the other hand, if the sum of the capacitive and resistive switching power losses is less than the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to increase the operating switching frequency. If the sum of the capacitive and resistive switching power losses is equal to the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to maintain the current operating switching frequency.

[0193] Thus, an operating switching frequency that optimizes or at least improves the balance between capacitive and resistive switching power losses and ripple current power losses can be identified and selected to optimize, minimize, or at least reduce the power consumption of the switching amplifier circuit 1100 when driving a load with unknown or variable characteristics.

[0194] Fig.12 is a schematic diagram of another example switching amplifier circuit for driving an inductive load 120 , such as an audio transducer (eg, a speaker, etc.), a tactile transducer (eg, a resonant actuator, such as a linear resonant actuator).

[0195] Fig.12 A switching amplifier circuit, shown generally at 1200, includes a Fig.11 The same components as the switching amplifier circuit 1100 are used in the embodiment of the present invention. Fig.11 and Fig.12 The same reference numerals are used throughout and, for the sake of clarity and brevity, will not be described in detail here.

[0196] The switching amplifier circuit 1200 differs from the switching amplifier circuit 1100 in that, instead of the load ripple power detector circuit 1110, the output current sensing amplifier circuit 1120, the output current sensing resistor circuit 1122 and the output voltage sensing amplifier circuit 1130, the switching amplifier circuit includes a load impedance model 1210 and a ripple power loss model 1220.

[0197] The load impedance model 1210 may be stored in a memory (such as a ROM or RAM) of a host device incorporating the switching amplifier circuit 1200 , and models the resistance and inductance of the load 120 .

[0198] The ripple power loss model 1220 may also be stored in a memory (such as a ROM or RAM) of a host device incorporating the switching amplifier circuit 1200, and is configured to receive a signal indicating a current operating switching frequency from the switching frequency generator 320 and generate an estimated ripple power loss measurement for the current operating switching frequency based on the inductance and / or resistance of the load 120 as provided by the load impedance model 1210.

[0199] The ripple power loss model 1220 outputs a signal to the power loss comparator circuit 1140 that indicates the estimated ripple current power loss at the current operating switching frequency.

[0200] and Fig.11 Like the switching amplifier circuit 1100, the power loss comparator circuit 1140 is configured to compare the signal indicating the ripple current power loss with the signal indicating the combined capacitive and resistive switching power losses output by the amplifier switching loss model 1150, and output a control signal to the switching frequency generator 340 to increase, decrease or maintain the operating switching frequency based on the result of the comparison.

[0201] Therefore, if the sum of the capacitive and resistive switching power losses is greater than the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to reduce the operating switching frequency. If the sum of the capacitive and resistive switching power losses is less than the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to increase the operating switching frequency. If the sum of the capacitive and resistive switching power losses is equal to the ripple current power loss, the power loss comparator circuit 1140 may output a control signal to maintain the current operating switching frequency.

[0202] Thus, an operating switching frequency that optimizes or at least improves the balance between capacitive and resistive switching power losses and ripple current power losses can be identified and selected to optimize or at least reduce the power consumption of the switching amplifier circuit 1100 when driving a load whose characteristics are known.

[0203] The circuits and methods described above with reference to the accompanying drawings enable selection of an optimal or at least beneficial operating switching frequency for a modulator circuit in a switching amplifier circuit to provide an optimal or improved balance between capacitive and resistive switching power losses in the switching amplifier circuit and ripple current power losses in the load, thereby optimizing, minimizing or at least reducing the power consumption of the switching amplifier circuit.

[0204] Adjustment of the operating switching frequency in the manner described above may be performed once, for example during a production testing process of a host device incorporating any of the switching amplifier circuit examples described above, or during an adjustment process performed during or after manufacture of the switching amplifier circuit to adjust the switching amplifier circuit to a specific operating switching frequency corresponding to a specified or rated operating frequency of the output transducer.

[0205] Additionally or alternatively, such adjustment of the operating switching frequency may be performed as part of a startup sequence for the amplifier circuit and / or may be initiated periodically or intermittently by a host device incorporating any of the switching amplifier circuit examples described above. Additionally or alternatively, such adjustment of the operating switching frequency may be initiated if the power consumption of the switching amplifier circuit meets or exceeds a predetermined threshold. As a further alternative, any of the methods described above may be used to continuously adjust the operating switching frequency to maintain optimal, minimal, or at least reduced power consumption of the switching amplifier circuit.

[0206] In the above examples, the switching frequency generator and input and / or output power monitoring circuits are provided as part of the switching amplifier circuit. However, in other examples, the switching frequency of the modulator circuit can be controlled by a host device incorporating the switching amplifier circuit, and the input and / or output power can be monitored by the host device to facilitate identification and selection of an optimal or at least beneficial operating switching frequency that optimizes or at least reduces power consumption of the switching amplifier circuit.

[0207] The circuits described above with reference to the accompanying drawings may be implemented in an integrated circuit, for example, as one or more integrated circuits. The circuits described above with reference to the accompanying drawings (whether implemented as discrete circuits or integrated circuits) may be incorporated into a host device (such as a laptop, notebook, netbook, or tablet computer), a gaming device (such as a game console or a controller for a game console), a virtual reality (VR) or augmented reality (AR) device, a mobile phone, a portable audio player, or some other portable device, or may be incorporated into an accessory device for use with a laptop, notebook, netbook, or tablet computer, a gaming device, a VR or AR device, a mobile phone, a portable audio player, or other portable device.

[0208] The skilled person will recognize that some aspects of the above-described apparatus and methods may be embodied as processor control code, for example, on a non-volatile carrier medium such as a disk, CD- or DVD-ROM, a programmed memory such as a read-only memory (firmware), or on a data carrier such as an optical or electrical signal carrier. For many applications, the embodiments will be implemented on a DSP (digital signal processor), an ASIC (application specific integrated circuit), or an FPGA (field programmable gate array). Thus, the code may include conventional program code or microcode, or, for example, code for setting up or controlling an ASIC or FPGA. The code may also include code for dynamically configuring a reconfigurable device such as a reprogrammable logic gate array. Similarly, the code may include code for a hardware description language such as Verilog TM The code may be distributed among multiple coupled components that communicate with each other, as will be appreciated by the skilled artisan. Where appropriate, embodiments may also be implemented using code that runs on a field programmable (reprogrammable) analog array or similar device to configure analog hardware.

[0209] It should be noted that the above embodiments illustrate rather than limit the present invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims, "a" or "an" does not exclude a plurality, and a single feature or other unit may perform the functions of several units recited in the claims. Any reference signs or labels in the claims should not be construed as limiting their scope.

Claims

1. A switching amplifier circuit for driving an inductive load, the switching amplifier circuit comprising: Modulator circuit; as well as An output stage circuit, wherein the switching amplifier circuit is configured as: When the modulator circuit outputs a modulated output signal that generates a ripple current in the load: adjusting a switching frequency of the modulator circuit within a predetermined frequency range; monitoring the power of the switching amplifier circuit while adjusting the switching frequency within the predetermined frequency range; as well as A frequency within the predetermined frequency range is selected as the operating switching frequency of the modulator circuit, at which frequency within the predetermined frequency range the monitored power meets a predefined criterion.

2. The switching amplifier circuit according to claim 1, wherein: The monitored power includes input power to the amplifier circuit; and The switching amplifier circuit further comprises an input power monitoring circuit for monitoring the input power, And wherein the circuit is configured to select a frequency within the predetermined range as the operating switching frequency, at which a minimum monitored input power of the switching amplifier circuit occurs. 3 . The switching amplifier circuit of claim 2 , wherein the input power monitoring circuit comprises an input current monitoring circuit for monitoring an input current of the switching amplifier circuit. 4 . The switching amplifier circuit of claim 3 , wherein the input power monitoring circuit further comprises an input voltage monitoring circuit for monitoring an input voltage of the switching amplifier circuit.

5. A switching amplifier circuit as claimed in any preceding claim, wherein the modulator circuit comprises a class D modulator circuit operable in either a class BD mode of operation or a class AD mode of operation.

6. A switching amplifier circuit according to claim 5, wherein the output stage circuit includes a single-ended output stage circuit, and wherein the modulator circuit is capable of operating in its class AD mode or its class BD mode to output the modulated output signal that produces a ripple current in the load.

7. A switching amplifier circuit according to claim 5 or claim 6, wherein the output stage circuit comprises a differential output stage circuit, and wherein the modulator circuit is capable of operating in its class AD mode to output the modulated output signal that produces a ripple current in the load.

8. The switching amplifier circuit according to any one of claims 5 to 7, wherein: The switching amplifier circuit also includes a pilot or test signal generator circuit operable to supply a pilot or test signal to an input of the modulator circuit; The output stage circuit comprises a differential output stage circuit; and The modulator circuit is operable in its Class BD mode to output a modulated output signal that produces a ripple current in the load based on the pilot or test signal.

9. The switching amplifier circuit of claim 8, wherein the pilot or test signal comprises: a sinusoidal signal having predefined amplitude and / or frequency and / or phase characteristics; Variable amplitude sinusoidal signal; or A DC signal of fixed or variable amplitude.

10. A switching amplifier circuit according to any of the preceding claims, wherein the switching amplifier circuit is configured to have zero PWM switching when idle, wherein the switching amplifier circuit also includes a pilot or test signal generator circuit, which is capable of operating to supply a pilot or test signal to the input of the modulator circuit, and wherein the modulator circuit is capable of operating to output a modulated output signal that produces a ripple current in the load based on the pilot or test signal.

11. A switching amplifier circuit according to any of the preceding claims, wherein the switching amplifier circuit is configured to have zero PWM switching when idle, wherein the switching amplifier circuit includes a multi-mode modulator circuit, and wherein the modulator circuit is capable of operating in its operating mode to output a modulated output signal that produces a ripple current in the load in the absence of an input signal.

12. A switching amplifier circuit according to any preceding claim, wherein: The monitored power includes the output power of the amplifier circuit; The switching amplifier circuit further includes a load ripple current power monitoring circuit for monitoring the output power; and, The switching amplifier circuit is configured to select a frequency within the predetermined range at which a minimum monitored input power of the switching amplifier circuit occurs as the operating switching frequency.

13. The switching amplifier circuit of claim 12, wherein the load ripple current power monitoring circuit comprises a load current monitoring circuit and a load voltage monitoring circuit.

14. The switching amplifier circuit of claim 5, wherein the switching amplifier circuit is operable to change the operating mode of the modulator circuit based on characteristics or parameters of an input signal to the switching amplifier, and wherein the operating switching frequency is selected at least in part based on average input powers of the class AD operating mode and the class BD operating mode that vary over time.

15. The switching amplifier circuit of claim 5, wherein: The switching amplifier circuit is operable to change the operating mode of the modulator circuit based on a characteristic or parameter of an input signal to the switching amplifier, and wherein the switching amplifier circuit is configured to adjust the operating switching frequency based on a current or future operating mode of the modulator circuit.

16. A switching amplifier circuit according to any preceding claim, wherein a modulation index of the modulated output signal is variable.

17. A switching amplifier circuit according to claim 2 or any one of claims 3 to 16, when dependent on claim 2, wherein the switching amplifier circuit further comprises a load impedance detector circuit configured to detect the impedance of the load, wherein the switching amplifier circuit is operable to adjust the operating switching frequency based on a difference between the detected impedance of the load and a reference impedance of the load.

18. The switching amplifier circuit of claim 17, wherein the reference impedance of the load comprises a stored predefined impedance value or a stored calibrated impedance value determined during calibration of the switching amplifier circuit.

19. A switching amplifier circuit according to any of the preceding claims, wherein the load impedance detector circuit is configured to detect the impedance of the load based on the voltage across the load and the current flowing through the load when a pilot or test signal of a predetermined frequency is input to the modulator circuit.

20. A switching amplifier circuit according to claim 2 or any one of claims 3 to 19, when dependent on claim 2, wherein the switching amplifier circuit receives a supply voltage from a power supply external to the switching amplifier circuit, wherein the supply voltage is adjustable according to the detected impedance of the load.

21. The switching amplifier circuit of any preceding claim, wherein the switching amplifier circuit is configured to adjust the switching frequency of the modulator circuit if: during a production process of the switching amplifier circuit; and / or upon starting the switching amplifier circuit; and / or In response to a periodic start signal received from a host device incorporating the switching amplifier circuit; and / or continuously; and / or In response to power consumption of the switching amplifier circuit deviating from a predefined limit; and / or in response to a change in one or more characteristics of the load; and / or responsive to a change in an operating characteristic of the switching amplifier circuit.

22. A switching amplifier circuit as claimed in any preceding claim, wherein the modulator circuit comprises a pulse width modulator (PWM) circuit.

23. The switching amplifier circuit of any preceding claim, wherein the switching amplifier circuit is configured to monitor the power continuously, intermittently or periodically.

24. A switching amplifier circuit for driving an inductive load, the switching amplifier circuit comprising: Modulator circuit; Output stage circuit; as well as Power loss comparator circuit, wherein the power loss comparator circuit is configured to perform a comparison of power losses associated with the ripple current in the load with a switching loss model of the switching amplifier circuit, And wherein the switching amplifier circuit is configured to control a switching frequency of the modulator circuit based on the comparison.

25. The switching amplifier circuit of claim 24, wherein the switching amplifier circuit further comprises an output power detector circuit configured to generate a signal indicative of the power loss associated with the ripple current.

26. The switching amplifier circuit of claim 24 or claim 24, wherein the power losses associated with the ripple current in the load are based on a ripple power loss model of the switching amplifier circuit.

27. An integrated circuit comprising a switching amplifier circuit as claimed in any preceding claim.

28. A host device comprising a switching amplifier circuit as claimed in any preceding claim.

29. A host device according to claim 28, wherein the host device comprises a laptop, notebook, netbook or tablet computer, a gaming device, a game console, a controller for a gaming console, a virtual reality (VR) or augmented reality (AR) device, a mobile phone, a portable audio player, a portable device, an accessory device for use with a laptop, notebook, netbook or tablet computer, a gaming device, a game console, a VR or AR device, a mobile phone, a portable audio player, or other portable device.

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