HK1061749B - Dynamic allocation of power supplied by a power supply and frequency agile spectral filtering of signals - Google Patents

Description

Dynamic allocation of power supplied by power supply and frequency agile spectral filtering of signals

Technical Field

The present invention relates to a power supply circuit arrangement for an electronic device, and more particularly to a power supply circuit arrangement that allows a device to be switched between an operational mode and a reduced power or standby mode.

Background

Some high fidelity audio systems, e.g. so-called Dolby PRO-logic^TMOr Dolby digital^TM(Dolby digital) "surround sound" systems including systems for amplifying signals such as Dolby^TMThe power amplifier for each sound signal provided by the system is, for example, left, right, center, left rear, right rear. In a home audio system, these audio power amplifiers will be powered by a common main power supply.

Generally, in order to obtain a comfortable listening level, it is necessary to improve the signal response in a low frequency bass (bass) range. Dolby^TMA system provides a sub-bass signal output to a sub-bass system, which may be a separate active unit including a preamplifier/buffer, a high power audio power amplifier, and a large diameter speaker that provides adequate audio output at bass frequencies below the normal woofer frequencies. In order to boost the sound in the low frequency range, this sub-bass is provided together with its own dedicated audio power amplifier to overcome the disadvantages in terms of overall sound quality, since, due to the human ear responseAnd often by insufficient size of the listening room, the sub-woofer bass requires disproportionately large amounts of power to be adequately heard, and due to the sub-woofer having a very large structure compared to the other loudspeakers of the loudspeaker system, just more power is required to move the very large bass and correspondingly large amounts of air through the loudspeaker cone. In this way, a dedicated sub-woofer power supply drives the sub-woofer and the bulk of the power is not a load of the main amplifier power supply, which powers different other amplifiers thus allowing other sounds to be fully reproduced.

However, the use of separate active sub-woofers has a higher overall system cost and tends to overload (too much bass) the low frequency signal, since separate volume controls are required for the main unit and sub-woofers. Therefore, increased adjustment of the master volume control can result in these bass overloads. Power supplies are very expensive because they require power transformers, rectifiers, and large filter capacitors. In order to save the large amount of consumption that would result from providing separate power supplies for the high power sub-bass power amplifier, it is desirable that the sub-bass power amplifier share the same power supply as the main audio power amplifier. One such integrated system device is used in RCA home theater model RT2250(RCA home television model RT2250 mass by thomson Consumer Electronics Inc., Indianapolis, Indiana, USA) manufactured by Thomson consumer Electronics, Ind, Ind.A., by the same power source as the main audio amplifier.

However, this substantial cost reduction has been achieved, and when this power is needed for the main power amplifier, we again face the original problem of large power consumption by the main power supply. One solution is to make the main power supply larger, but this is very expensive and adds a lot of weight to the unit. Thus, this approach is not targeted as expected.

Most of the time, a main power supply with e.g. 50 watt audio output power is only lightly loaded even when the music is played "very loud". In larger rooms, playing at a power of one watt per average output level will likely make the window rattle and reduce hearing damage less. The reason why a high power output amplifier is desired (more pleasant to sound) is that even if played at such "loud" sound levels, the signal peaks are not attenuated or distorted. Therefore, the high power capacity of the main power source for the main power amplifier is hardly used. Thus, powering a dedicated sub-bass high power amplifier from the main power supply, including setting the maximum sub-bass power higher than the main channel power, will generally not conflict with the need for a main power amplifier. In this way, the sub-woofer is able to deliver twice the power of the low frequency components, since in the usual case, the mid-range frequency-range music content delivers only a small fraction of the energy relative to the sub-woofer low frequency range. In this way, the system can use the entire power of the amplification system more efficiently while greatly reducing costs.

Another problem is that to compensate for the less audible effect on the audio output by the listener in sub-bass audio frequencies, the sub-bass system gain is set for an unbalanced higher power output, which, as discussed above, can easily reach the full output of the sub-woofer with the sub-bass sound signal "clipped" or reaching its physical limit and distorting the reproduced sub-woofer sound.

Various U.S. patents disclose initiating an electronic action in response to a signal, associated with sub-woofers: us patent No.6,026,168 discloses level adjustment of a sub-bass signal in response to the volume of a scaled main signal; us patent No.5,636,288 discloses turning off the AC power supply of a separate integrated power amplifier of a sub-bass system in response to the presence or absence of a detection signal; and us patent No.5,347,230 discloses therein that the auxiliary power supply is active in response to the level of the audio signal, so that the output power capacity and the power dissipation of the output transistor are reduced at low signal levels and increased at high signal levels, with different parameters for reducing the ripple voltage associated with sub-bass frequencies.

Disclosure of Invention

According to aspects of the present invention, this conflict is resolved by dynamically allocating power from the power supply between the main power amplifier and the sub-bass power amplifier. When the control circuit detects an audio signal in a sub-bass frequency range above a predetermined threshold, a switch is operated to reduce the amount of power from the main power supply to the auxiliary sub-bass power amplifier, thereby switching the auxiliary power amplifier from a fully operational mode to a lower power mode while still providing a substantial low frequency bass output sound level but reducing the cost of the power supply.

For sub-bass devices, the sub-bass signal can be obtained in two ways. For using Dolby as discussed above^TMThe approach of the system is to provide a separate decoded output signal for sub-bass sound reproduction. Such sub-bass audio signals can also be used to participate in the dynamic power allocation disclosed herein. For no use of Dolby^TMAmplifier system for system, single/complex low pass filter can be used to obtain sub-bass sound signal, the method is used in the same way for Dolby^TMSub-bass signals are obtained in a sound system. However, for this non-Dolby^TMMeans capable of varying the cut-off frequency of the low-pass filter, i.e. frequency agility, and selecting the cut-off frequency in dependence on the type of music or the taste of the listener.

The power state change of the auxiliary circuit is provided by a variable resistor in series with the power input of the auxiliary circuit and in response to a control signal. The variable resistance is responsive to the control signal to change/switch between first and second resistance states, thereby generating respective first and second supply voltages/currents for the auxiliary circuit corresponding to the operable and non-zero reduced power modes. In the first resistive state, the supply voltage/current provided to the auxiliary circuit allows full power operation, and in the second resistive state, the supply voltage/current provided to the auxiliary circuit is insufficient for full power operation. Within the scope of the invention, the less power mode includes a wait state in which the auxiliary circuit is temporarily placed in a non-operational wait mode. However, in each state of the auxiliary power amplifier, the supply voltage/current supplied to the main power supply circuit is sufficient for normal operation.

In a preferred embodiment, the first resistance state corresponds to a low impedance, the supply voltage/current provided to the auxiliary power amplifier is the full operating voltage and the second resistance state corresponds to a relatively higher impedance state in order to reduce the maximum power output of the auxiliary circuit.

The variable resistor in the exemplary embodiment includes a fast acting relay having an excitation coil (operating coil) connected to the control circuit and a switch contact connected in parallel with a resistor such as a power resistor. Opening the switch contacts inserts a resistor in series with the power supply, reducing the power supply voltage/current supplied to the auxiliary amplifier to a lower level. Conversely, closing the switch contacts shorts out the resistance, placing a zero or negligible resistance on the power supply path, thus increasing the common supply voltage that may be used to assist the full power output of the amplifier. For transient peak power levels with a duration shorter than the relay reaction time, the supply capacitance should be large enough to obtain the supply voltage/current.

Instead of a relay, it could be replaced with a photoelectric switch or other suitable switch with faster reaction time and higher reliability than a relay, such as a Field Effect Transistor (FET) combined with an optocoupler or the like. Such an opto-coupled switch, like a relay, would provide electrical isolation between the control circuitry and the circuitry controlled by the device if such electrical isolation were desired.

Although the present discussion is provided in connection with a sub-woofer and its dedicated auxiliary power amplifier, other amplifiers and power supply means can be similarly switched. In addition, the relay contacts can be single pole double throw (spdt) to alternately switch two power amplifiers, each drawing their power from a common power supply node, or the relay contacts can be double pole double throw (dpdt) to switch fundamentally different operations.

Drawings

FIG. 1 is a block schematic diagram of a power supply apparatus including an electronic device for switching between an operational mode and a reduced power mode.

Fig. 2 is a representative schematic for a multi-stage adjustable low pass filter for providing the sub-bass signal of fig. 1.

Detailed Description

Fig. 1 shows an amplifier system 10 including a power supply 12 and an amplifier circuit including a power amplifier 14. Power supply 12 shows a power transformer 16 having a primary winding 18 connected to an AC power line, a secondary winding 20 connected to a full wave diode bridge 21, and a power supply filter capacitor 22 for providing a suitable voltage and current DC power supply to amplifier circuit 14 at nodes 30(+) and 32 (-). The power supply 12 has many possible configurations, for example, the power supply 12 is balanced by a center tap ground. The illustrated power supply is for exemplary purposes only and does not form a limiting part of the present invention. In this regard, it should be noted that in a television receiver having a CRT video display, some audio power amplifiers may be powered by a flyback circuit.

The main circuit and power amplifier 14 includes audio circuitry other than sub-bass signal processing and speaker driving, and provides power output to a plurality of speakers symbolically represented by a single speaker 34. An audio source signal is provided at terminal 36, and such audio source may be any possible source, such as, for example, a DVD device, a CD device, a tuner,audio tape devices, video tape devices, and the like. These signals are processed by a signal processor including tone and volume control functions, a source signal selection switch, and Dolby^TMOr other such systems, if used.

The signal processor 38 can include any of Dolby^TMA circuit that provides a decoded sub-bass signal or a single/multi-stage low-pass frequency selective filter 39 as shown in fig. 2. Filter 39 limits the signal applied to amplifier 55 and control circuit 52 to a selected band of frequencies. For example, since this particular embodiment is an audio application, filter 39 limits the signal to an audio frequency band or a portion of a frequency band, e.g., sub-bass audio frequencies. Although a ladder filter is shown, other configurations including active filters can be used.

Further, the filter series resistor 40 is not a fixed resistor, but is a variable resistor determined by the CPU 42. In this way, the frequency cut-off (cut-off) of the sub-bass low-pass filter is frequency agile and can be spectrally modified by changing the cut-off frequency, e.g. depending on the frequency content of the audio signal, the level of the sub-bass signal or user settings. Further, the attenuator 44 controlled by the CPU42 can be used to change the amplitude of the sub-bass signal, for example, in response to the level of the audio signal. In this way, if the audio signal is at a high level, such as a high volume control setting, the sub-bass signal can be reduced to further reduce the load on the power supply 12 and to further reduce possible overloading of the sub-bass amplifier and speakers.

Referring back to fig. 1, signal processor 38 outputs the sub-bass signal on line 50 coupled to control circuitry 52 to a sub-bass signal processing and power amplifier 55 whose output is coupled to a sub-woofer 56. Amplifier 55 is similar to power amplifier 14 except that it may be more powerful than any single power amplifier of amplifier 14 and have an ultra-low frequency response at sub-bass audio frequencies.

Control circuit 52 also receives the sub-bass signal provided on line 50 and receives power from power supply 12 at node 30. The control circuit 52 turns on a coil 56 of a switch 54, shown in the exemplary embodiment as a single pole, single throw relay. Resistor 58 is a power resistor in series with power input 60 of power amplifier 55 and is coupled to power supply terminal 30. Since relay 54 is unpowered, e.g., terminals 54a and 54b are in a normally closed (nc) position, shorting resistor 58 and thus providing full power supply to amplifier 55 in order to operate power amplifier 55 at full power.

When the signal level on line 50 reaches a predetermined threshold level, as determined by a comparator (not shown) or some other threshold determining circuit, relay 54 is actuated and terminals 54a and 54b are opened, thus inserting resistor 58 in series with power lead 60. In this manner, the power amplifier 55 draws more current to the sub-woofer 56 for higher power output, and the voltage drop across the resistor 58 reduces the voltage/current output power supplied to the power amplifier 55, thus placing the amplifier 55 in a reduced power mode. Reducing power may mean waiting, if desired, for example, for the value of resistor 58 to be large enough to render circuit 54 inoperative with resistor 58 in that circuit, and returning to full operational functionality through circuit 54 when resistor 58 is shorted. The value of resistor 58 is selected to provide the desired result for the inactive state of circuit 54 between the range of slightly reduced power.

It is apparent that the low impedance state does not require a short circuit. A resistor of suitable value and power ratio (not shown) can be connected in series with one of the terminals 54a/54b so that the impedance of the high impedance state is the series combination of the resistor and the resistor 58. In any event, the resistor 58 and any resistors placed in series with the resistor 58 must have a sufficient power ratio.

It should be noted that the insertion of resistor 58 in the power supply input to amplifier 55 also changes the power supply regulation to amplifier 55 and reduces the maximum current drawn from the power supply. Thus, as used herein, a reduction in the supply voltage due to the insertion of a series resistance or variable impedance also includes a reduced power supplied to the supply current.

It will be appreciated that other forms of switches could be substituted for the relay 54, for example, the switch 54 could comprise an optocoupler using an LED, and for example a photodiode, photo-FET transistor, in which case the diode/transistor would replace the switch contacts, and be connected by a resistor 58, such a device would also have faster action than a relay but would also be more expensive.

The invention is intended to cover various modifications and alternative embodiments. For example, the invention is not limited to the particular examples of switching devices described herein, but includes other devices that will provide the disclosed operation. Moreover, the resistor 58 can have one reactive element, or a combination of resistances, reactive and/or active elements, i.e. resistive, inductive, capacitive, or non-linear elements, e.g. diodes, zener diodes, transistors.

Although the preferred embodiment of the invention described herein is a sub-woofer with a power amplifier, it will be appreciated that the invention may be applied to other devices that switch between operating and reduced power modes in response to a control signal, in this case an audio signal located within a suitable audio frequency band. Additionally, the relay 54 can be a single pole double throw (spdt), such as alternately switching two amplifiers, each drawing power from a common power supply node, or the relay 54 can be a double pole double throw (dpdt) with other electrodes switching some other means, such as regularly pulsing a color status lamp.

Claims (9)

1. A power supply circuit arrangement switchable between a plurality of modes, comprising:

a main circuit and an auxiliary circuit, each coupled to derive their supply voltage/current from a common power supply;

a control circuit having detector means for detecting the level of a signal and providing a control action corresponding to the detected level of the signal; and

a variable impedance device coupled between the common power supply and the auxiliary circuit, responsive to said control action, for switching between first and second impedance states to generate respective first and second supply voltages/currents received by the auxiliary circuit from the power supply, wherein

The first and second voltages/currents correspond to an operational mode and a non-zero reduced power mode, respectively, and the variable impedance device is not coupled between the common power source and the main circuit.

2. The apparatus of claim 1, wherein for the first impedance state the respective supply voltage provided to the auxiliary circuit allows normal operation, and for the second impedance state the respective supply voltage provided to the auxiliary circuit is insufficient for normal operation, while the supply voltage/current provided to the main circuit is sufficient for normal operation in the first and second impedance states.

3. The apparatus of claim 1, wherein the variable impedance device comprises a switch and an impedance.

4. The apparatus of claim 3, wherein the switch and the impedance are connected in parallel with each other, and the switch is operable in response to the control circuit.

5. The apparatus of claim 4, wherein the second impedance state is generated by opening a switch and the first impedance state is generated by closing a switch.

6. The apparatus of claim 5, wherein the switch comprises a relay having switch contacts connected in parallel with the impedance.

7. The apparatus of claim 3, wherein the impedance comprises a resistor.

8. The apparatus of claim 3, wherein the impedance comprises a combination of resistive and reactive elements.

9. The apparatus of claim 2, wherein the main circuit and the auxiliary circuit are speaker driver circuits.