Patent Application
20120263323
With the advancement of the technology, the requirement of the low power consumption becomes more important. As a result, the size of the portable electronic device is become thinner and thinner. Because of the disadvantage of the big volume and the weight of the flat sound generator system of the portable electronic device applied for the conventional sound generator, the power consumption of the driver of the flat sound generator system is around 1.5 W˜2 W and that it's about 20%˜70% of the whole power consumption. The power consumption rate of the driver is too high for the portable electronic device. Thus, more and more efforts are focus on the improvement of the flat sound generator system.
Since the conventional flat sound generator system make sounds by utilizing high voltage signals, thus, the audio driver 102 has to utilize the high power transformer with low bandwidth 109 so as to transform the signal which generated by the audio amplifier 108 into two output audio signals So1 and So2 which flat sound generator system 101 needed. However, in order to avoid the signal distorted within the whole audio frequency range, the size of the coil inductor and the core of the high power transformer with low bandwidth 109 need bigger. It may occupy large space and expensive. In other words, the issue of the size of the coil inductor and the core will cause the volume and the weight of the flat sound generator system 101 can not be reduced efficiency.
Consequently, it is so important to reduce the volume and the weight of the flat sound generator system effectively and decrease the power consumption of the flat sound generator system, so as to improve the working time of the portable electronic device.
In one embodiment, an audio driver for a flat sound generator is coupled to the sound generator. The audio driver includes a power amplifier and an audio-amplifying transformer, the power amplifier receiving an input audio signal and the audio-amplifying transformer transforms the input audio signal into an output audio signal to drive a flat sound generator. The flat sound generator includes a perforated electrode plate and a diaphragm. Wherein, the audio-amplifying transformer and the flat sound generator form a low-pass filter effectively.
Features and advantages of embodiments of the claimed subject matter will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which:
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the embodiments of the present invention.
The capacitance flat sound generator 201 includes a perforated electrode plate 205 and a diaphragm 210, wherein the perforated electrode plate 205 includes a plurality of openings 207. The diaphragm 210 includes a film body layer 208 and an electrode layer 206 with charges. In one embodiment, the film body layer 208 can be composed of polytetrafluoroethene (PTFE) or fluorinated ethylene propylene (FEP), but not limited to. In one embodiment, the electrode layer 206 can be composed of aluminum, chromium, or any other electricity conductive materials, but not limited to. The perforated electrode plate 205 and the diaphragm 210 receive the output audio signals So1 and So2 respectively.
The capacitance flat sound generator 201 can be used as a capacitor, wherein the capacitance C can be represented according to equation (1):
Wherein, in equation (1), ∈0 is a dielectric factor of vacuum, is a relatively dielectric factor, A is the measure of area of the diaphragm 210 and the perforated electrode plate 205, d is the distance between the diaphragm 210 and the perforated electrode plate 205.
The amplified input audio signal Sin′ be amplified N2/N1 times by the audio-amplifying transformer 203 and be transformed as output audio signals So1 and So2 to drive the capacitance flat sound generator 201. The value of the output audio signals So1 and So2 can be represented according to equation (2) or equation (3):
In one embodiment, the ratio (N2/N1) of the secondary winding and the primary winding of the audio-amplifying transformer 203 is around 50˜120. In another embodiment, the windings of the primary side or the secondary side are enameled wire with 0.12φ˜0.02φ.
The power consumption Wc of the capacitance flat sound generator 201 can be represented according to equation (4):
W
C=½C(So1−So2)2 (4)
Although the difference (So1−So2) between the output audio signals So1 and So2 is large, the capacitance of the capacitance flat sound generator 201 is very small (usually around 20 pF˜20 nF). Thus, the level of the power consumption Wc of the capacitance flat sound generator 201 is around uW.
Advantageously, the audio-amplifying transformer 203 and the capacitance flat sound generator 201 form a low-pass filter for filtering out the high frequency signal which outputted to the output audio signals So1 and So2. Further, the audio-amplifying transformer 203 is modulated between a wideband of the input audio signal Sin which has relatively high frequency, thus, the capacitance flat sound generator 201 just need a low cost transformer with higher central frequency instead of the high power transformer which with low wideband. As a result, the volume and the weight of the capacitance flat sound generator 201 can be reduced and further decrease the power consumption and then to improve the working time of the portable electronic device.
In one embodiment, the silicon steel of the audio-amplifying transformer 203 has characteristics of low frequency, directivity, and high permeability. In another embodiment, the material of the bobbin of the audio-amplifying transformer 203 is liquid crystal plastic (LCP) and the pin type is C type, so as to avoid the diameter of the winding of the primary side or the secondary side too thin and cause the disconnection.
An audio driver 202 coupled to a capacitance flat sound generator 201 and includes a power amplifier 204 and an audio-amplifying transformer 203 receiving an input audio signal Sin and for transforming it into a high voltage output audio signals So1. In one embodiment, the input audio signal Sin is the audio signal provided by the portable multi-media device, such as MP3 player, CD player, and smart phone, etc. The power amplifier 204 receives a DC high voltage VDCH provided by a high voltage DC source 209 and amplifies the input audio signal Sin to a amplified input audio signal Sin′. In one embodiment, the DC source 209 is provided by a DC/AC converter (not shown) or DC/DC converter (not shown). The power amplifier 204 can be a class AB amplifier or class D amplifier, but not limited to.
The capacitance flat sound generator 201 includes a perforated electrode plate 205 and a diaphragm 210, wherein the perforated electrode plate 205 includes a plurality of openings 207. The diaphragm 210 includes a film body layer 208 and an electrode layer 206 with charges. In one embodiment, the film body layer 208 can be composed of polytetrafluoroethene (PTFE) or fluorinated ethylene propylene (FEP), but not limited to. In one embodiment, the electrode layer 206 can be composed of aluminum, chromium, or any other electricity conductive materials, but not limited to. The perforated electrode plate 205 and the diaphragm 210 receive the output audio signal So1.
The capacitance flat sound generator 201 can be used as a capacitor, wherein the capacitance C can be represented according to equation (5):
Wherein, in equation (5), ∈0 is a dielectric factor of vacuum, is a relatively dielectric factor, A is the measure of area of the diaphragm 210 and the perforated electrode plate 205, d is the distance between the diaphragm 210 and the perforated electrode plate 205.
The amplified input audio signal Sin′ be amplified N2/N1 times by the audio-amplifying transformer 203 and be transformed as a output audio signals So1 to drive the capacitance flat sound generator 201. The value of the output audio signal So1 can be represented according to equation (6) or equation (7):
In one embodiment, the ratio (N2/N1) of the secondary winding and the primary winding of the audio-amplifying transformer 203 is around 50˜120. In another embodiment, the windings of the primary side or the secondary side are enameled wire with 0.12φ˜0.02φ.
The power consumption Wc of the capacitance flat sound generator 201 can be represented according to equation (8):
W
c=½CSo12 (4)
Although the value of So1 is large, the capacitance of the capacitance flat sound generator 201 is very small (usually around 20 pF˜20 nF). Thus, the level of the power consumption Wc of the capacitance flat sound generator 201 is around uW.
Advantageously, the audio-amplifying transformer 203 and the capacitance flat sound generator 201 form a low-pass filter for filtering out the high frequency signal which outputted to the output audio signal So1. Further, the audio-amplifying transformer 203 is modulated between a wideband of the input audio signal Sin which has relatively high frequency, thus, the capacitance flat sound generator 201 just need a low cost transformer with higher central frequency instead of the high power transformer which with low wideband. As a result, the volume and the weight of the capacitance flat sound generator 201 can be reduced and further decrease the power consumption and then to improve the working time of the portable electronic device.
In one embodiment, the silicon steel of the audio-amplifying transformer 203 has characteristics of low frequency, directivity, and high permeability. In another embodiment, the material of the bobbin of the audio-amplifying transformer 203 is liquid crystal plastic (LCP) and the pin type is C type, so as to avoid the diameter of the winding of the primary side or the secondary side too thin and cause the disconnection.
While the foregoing description and drawings represent embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the principles of the present invention as defined in the accompanying claims. One skilled in the art will appreciate that the invention may be used with many modifications of form, structure, arrangement, proportions, materials, elements, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims and their legal equivalents, and not limited to the foregoing description.
