U.S. patent application number 14/667542 was filed with the patent office on 2015-07-16 for self-bias emitter circuit.
The applicant listed for this patent is Turtle Beach Corporation. Invention is credited to Elwood G. Norris.
Application Number | 20150201276 14/667542 |
Document ID | / |
Family ID | 52019242 |
Filed Date | 2015-07-16 |
United States Patent
Application |
20150201276 |
Kind Code |
A1 |
Norris; Elwood G. |
July 16, 2015 |
SELF-BIAS EMITTER CIRCUIT
Abstract
Self-bias emitter circuit configurations can use the amplitude
of an input AC carrier signal to provide a DC bias voltage across
an emitter for suitable operation. A self-bias emitter circuit can
include a transductor with primary matched with an amplifier, while
secondary can be matched to the emitter. Self-bias emitter circuit
can also include a full-wave bridge rectifier or a center tap
inductor in conjunction with two diodes to rectify the AC carrier
signal into a corresponding DC voltage. This DC voltage can be
subsequently filtered by a capacitor to provide a steady DC bias
voltage across the emitter. Sufficiently small, decoupling
capacitors can be installed at each side of the full-wave rectifier
in order to decouple the DC bias voltage, while a sufficiently
large capacitor can be installed between the emitter and secondary
for preventing the applied DC bias voltage from flowing back to
secondary.
Inventors: |
Norris; Elwood G.; (Poway,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Turtle Beach Corporation |
Poway |
CA |
US |
|
|
Family ID: |
52019242 |
Appl. No.: |
14/667542 |
Filed: |
March 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13917315 |
Jun 13, 2013 |
8988911 |
|
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14667542 |
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Current U.S.
Class: |
381/150 |
Current CPC
Class: |
A61B 8/56 20130101; H04R
3/00 20130101; H04R 2217/03 20130101; H04R 19/02 20130101 |
International
Class: |
H04R 3/00 20060101
H04R003/00 |
Claims
1. An emitter circuit for providing a bias voltage, comprising: an
emitter; a full-wave bridge rectifier configured to convert an
alternating current (AC) carrier signal into a corresponding direct
current (DC) voltage; and a filter capacitor configured to reduce
variations of the DC voltage at an output of the full-wave bridge
rectifier in order to provide a DC bias voltage across the
emitter.
2. The emitter circuit of claim 1, wherein the circuit is
configured to receive the AC carrier signal as input and rectify
the AC carrier signal into a steady DC bias voltage.
3. The emitter circuit of claim 1, wherein the DC bias voltage is
applied across the emitter without affecting carrier information
used by the emitter to emit parametric information.
4. The emitter circuit of claim 1, further comprising a transductor
with a primary winding and a secondary winding, the transductor
configured to match an impedance of the primary winding to an
impedance of an amplifier with the secondary winding configured to
form a part of a parallel resonant circuit with the emitter.
5. The emitter circuit of claim 4, further comprising a decoupling
capacitor configured to decouple the DC bias voltage from the
secondary winding and to avoid shunting the AC carrier signal into
the full-wave bridge rectifier.
6. The emitter circuit of claim 4, further comprising a capacitor
configured to prevent the DC bias voltage from flowing back to the
secondary winding.
7. The emitter circuit of claim 2, wherein the AC carrier signal
includes a modulated AC carrier signal or an unmodulated AC carrier
signal.
8. The emitter circuit of claim 1, wherein the emitter circuit
forms a part of a parametric speaker.
9. The emitter circuit of claim 1, wherein the DC bias voltage can
correspond with a peak of the AC carrier signal.
10. An emitter circuit for providing a bias voltage, comprising; an
emitter; a transductor including a primary winding and a secondary
winding, the secondary winding including a first portion and a
second portion; a full-wave bridge rectifier coupled to the second
portion of the secondary winding, the full-wave bridge rectifier
operable to convert an alternating current (AC) carrier signal into
a corresponding direct current (DC) voltage; and a filter capacitor
configured to smooth the corresponding DC voltage in order to
provide a DC bias voltage across the emitter.
11. The emitter circuit of claim 10, wherein a number of turns of
the first portion of the secondary winding and the second portion
of the second secondary winding is determined based on a desired
amplitude of the DC bias voltage.
12. The emitter circuit of claim 10, wherein the transductor is
configured to: match the primary winding to the amplifier; couple
the first portion of the secondary winding to the full-wave bridge
rectifier to provide step-up voltage conversion, wherein the first
portion of the secondary winding has a higher number of turns
relative to the second portion of the secondary winding; and match
the second portion of the secondary winding to the emitter.
13. The emitter circuit of claim 12, wherein the step-up voltage
conversion provides the DC bias voltage across the emitter.
14. The emitter circuit of claim 10, wherein the emitter circuit
includes a center tapped inductor to provide full-wave
rectification of the AC carrier signal.
15. The emitter circuit of claim 10, wherein the emitter circuit
includes a voltage doubler used in conjunction with the filter
capacitor for providing the DC bias voltage to the emitter.
16. The emitter circuit of claim 10, further comprising a diode to
limit an amplitude of the DC bias voltage applied across the
emitter.
17. A method for providing a bias voltage across an emitter, the
method comprising: receiving an alternating current (AC) carrier
signal at an emitter circuit, the emitter circuit including a
transductor with a primary winding and a secondary winding;
converting the AC carrier signal into a corresponding direct
current (DC) voltage; and reducing variations of the DC voltage to
provide a DC bias voltage across the emitter included in the
emitter circuit.
18. The method of claim 17, further comprising: matching the
primary winding of the transductor with an impedance of an
amplifier; and matching the secondary winding of the transductor
with an impedance of the emitter to provide a chosen resonant
point. Same change here
19. The method of claim 18, further comprising decoupling the DC
bias voltage from the secondary winding to avoid shunting the AC
carrier signal into a full-wave bridge rectifier associated with
the emitter circuit.
20. The method of claim 18, further comprising preventing the DC
bias voltage from flowing back to the secondary winding of the
transductor.
Description
PRIORITY CLAIM
[0001] This is a continuation of U.S. patent application Ser. No.
13/917,315, filed Jun. 13, 2013, which is hereby incorporated
herein by reference in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present disclosure relates generally to parametric
loudspeakers for use in audio production, and more particularly, to
emitter circuit configurations.
[0004] 2. Background Information
[0005] A new form of emitters can include a film made of plastic
materials such as kapton, mylar, and polypropylene, among others.
The upper side of this film can be laminated with a conductive
material such as copper, nickel, aluminum, or gold.
[0006] The emitter can also include a back plate or stator which
can be configured to exhibit a plurality of microscopic slots or
pits arranged in a random pattern. The lower side of the stator can
be metallized to receive the application of voltage.
[0007] Both film and stator can be combined in such a way that the
non-metalized side of the film or lower side can be in contact with
the upper side of the stator that exhibits the plurality of
microscopic slots or pits. A DC bias voltage can be applied to the
metalized side or upper side of the film and the metalized or lower
side of the stator, where both conductive sides of film and stator
can be separated by the film since its lower side is not
metallized. When the DC bias voltage is applied to the emitter, the
metalized side of the stator can pull the film down to the cavities
of the microscopic slots or pits, causing the emitter to activate.
As such, DC bias voltage application can be required for a suitable
emitter operation.
[0008] To provide DC bias voltage, an auxiliary power supply can be
operatively connected to the emitter, but this configuration can
increase the cost of the emitter circuit while also implying the
use of additional wires to connect the emitter with the auxiliary
power supply.
[0009] For the foregoing reasons, there is a need for providing a
suitable application of DC bias voltage to a new emitter
configuration.
SUMMARY
[0010] A self-bias emitter circuit can receive a modulated or
unmodulated AC carrier signal as input and can subsequently rectify
this modulated or unmodulated AC carrier signal into a steady DC
bias voltage for suitable application across an emitter device
without affecting carrier information necessary to the emitter to
emit parametric information.
[0011] According to an embodiment, a self-bias emitter circuit can
include a transductor with an electromagnetic shielded pot core,
where its primary can be matched to the impedance of an amplifier,
while its secondary is matched to the impedance of the emitter to
provide a chosen resonant point. This self-bias emitter circuit can
include a full-wave bridge rectifier that can convert the modulated
or unmodulated AC carrier signal into a corresponding DC voltage.
Subsequently, a filter capacitor can reduce variations of the DC
voltage at the output of full-wave bridge rectifier in order to
provide a steady DC bias voltage across the emitter for suitable
operation. Sufficiently small, decoupling capacitors can be
installed at each side of the full-wave rectifier to decouple the
DC bias voltage from the secondary and to avoid shunting the AC
carrier signal into the full-wave bridge rectifier. A sufficiently
large capacitor can be installed between emitter and secondary to
prevent DC bias voltage from flowing back to secondary.
[0012] Amplitude of DC bias voltage can approximately correspond to
the highest peak of the AC carrier signal, where maximum achievable
DC bias voltage can be determined by the highest peak of a
modulated carrier signal.
[0013] According to another embodiment, a self-bias emitter circuit
can include transductor with one primary and two secondary
windings, where primary can be matched to the amplifier, while one
secondary can be matched to the emitter. The other secondary can be
operatively connected to the full-wave bridge rectifier which can
convert an AC carrier signal into corresponding DC voltage,
followed by smoothing of this DC voltage by filter capacitor for
the application of suitable DC bias voltage across the emitter.
Numbers of turns in the secondary connected with full-wave bridge
rectifier can be selected according to the desired amplitude of the
DC bias voltage.
[0014] In another embodiment, a self-bias emitter circuit can
include transductor with primary matched to the amplifier, while
the secondary can include an intermediate tap to configure one
section of the secondary with a higher number of turns. Section of
secondary with higher number of turns can be operatively connected
to the full-wave rectifier to provide step-up voltage conversion,
and consequently a higher DC bias voltage across the emitter. The
other section of secondary can be configured for matching the
emitter resonance.
[0015] Yet in another embodiment, a self-bias emitter circuit does
not require the full-wave bridge rectifier for converting AC
carrier signal into DC bias voltage. In such case, a center tapped
inductor can be used as secondary in conjunction with two diodes
for providing full-wave rectification of AC carrier signal,
followed by filtering and application of DC bias voltage across the
emitter.
[0016] In an even further embodiment, a self-bias emitter circuit
does not require the full-wave bridge rectifier for converting AC
carrier signal into DC bias voltage. In this particular embodiment,
the self-bias emitter circuit can include a voltage doubler which
can be used in conjunction with a filter capacitor in order to
provide a steady and increased DC bias voltage to the emitter,
while also coupling a modulated AC carrier signal to the emitter
without significant signal attenuation. This self-bias emitter
circuit can also include a zener diode to limit the amplitude of
the DC bias voltage applied across the emitter.
[0017] The disclosed embodiments of a self-bias emitter circuit can
use the amplitude of the modulated or unmodulated carrier signal to
provide suitable DC bias voltage across the emitter, eliminating
the necessity of auxiliary power supplies and external wires, and
thereby, reducing operational costs and simplifying operation of
the emitter system. Additional features and advantages can become
apparent from the detailed descriptions which follow, taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0018] Non-limiting embodiments of the present invention are
described by way of example with reference to the accompanying
figures which are schematic and are not intended to be drawn to
scale. Unless indicated as representing the background information,
the figures represent aspects of the invention.
[0019] FIG. 1 shows an emitter circuit which can include an
auxiliary power supply for supplying a bias voltage across an
emitter device as described in the background information.
[0020] FIG. 2 illustrates a self-bias emitter circuit that can
include a full-wave bridge rectifier and does not require the use
of auxiliary power supply and wires to provide a DC bias voltage to
the emitter, according to an embodiment.
[0021] FIGS. 3A, 3B and 3C depict various examples of AC to DC
conversion that can be performed by a self-bias emitter
circuit.
[0022] FIG. 4 shows another self-bias emitter circuit that can
include a center tapped inductor in conjunction with two diodes for
rectification and does not require the use of an auxiliary power
supply and wires to provide a DC bias voltage to the emitter.
[0023] FIG. 5 illustrates another embodiment of a self-bias emitter
circuit where a full-wave bridge rectifier can be used in
conjunction with an additional secondary to provide a steady DC
bias voltage to the emitter.
[0024] FIG. 6 depicts another embodiment of a self-bias emitter
circuit which can include a secondary in the form of an inductor
having a section with a higher number of turns and including an
intermediate tap, where the section can be connected with full-wave
bridge rectifier to provide a steady DC bias voltage to the
emitter.
[0025] FIG. 7 shows another embodiment of a self-bias emitter
circuit which can include a voltage doubler and a zener diode.
DETAILED DESCRIPTION
[0026] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, which are not to scale or to proportion, similar symbols
typically identify similar components, unless context dictates
otherwise. The illustrative embodiments described in the detailed
description, drawings and claims, are not meant to be limiting.
Other embodiments can be used and/or and other changes can be made
without departing from the spirit or scope of the present
disclosure.
Definition of Terms
[0027] As used herein, "emitter" can refer to a device capable of
emitting ultrasonic signals and that can be integrated in a
self-bias emitter circuit.
[0028] As used herein, "self-bias emitter circuit" can refer to a
circuit capable of transforming an input modulated or unmodulated
AC carrier signal into a steady DC bias voltage.
[0029] As used herein, "DC bias voltage" can refer to a steady or
constant DC voltage that can be obtained after rectification and
filtering of a modulated or unmodulated AC carrier signal, for
subsequent application across the emitter.
Description
[0030] FIG. 1 shows an emitter circuit 100 which can include an
auxiliary power supply 102 for supplying a bias voltage across an
emitter 104 as described in the background information. This
emitter circuit 100 can also include a transductor 106 with primary
108 and secondary 110, a swing capacitor 112, and a resistor
114.
[0031] Emitter 104 can be configured for allowing the emission of
ultrasonic signals, and can exhibit a capacitance ranging from
about 0.5 nF to about 10 nF depending on materials and
configuration of emitter 104. For suitable operation, auxiliary
power supply 102 can be operatively coupled to provide a bias
voltage across emitter 104 using a first wire 116 and a second wire
118 as shown in FIG. 1. A resistor 114 can be in series with first
wire 116 to couple emitter 104. Auxiliary power supply 102 can be
powered by a 3V battery to provide an output DC (direct current)
voltage that can be constant and can exhibit values ranging from
about 200 volts to about 500 volts, depending on the biasing
requirements of emitter 104. Optionally, auxiliary power supply 102
can be powered by regular AC (alternating current) 120 volts, in
which case an AC/DC transformer can be integrated into auxiliary
power supply 102 to convert AC voltage to DC voltage necessary for
biasing emitter 114. Resistor 114 can range from about 1 M.OMEGA.
to about 10 M.OMEGA. depending on the coupling requirements of
emitter 104.
[0032] Capacitor 112 can be installed in emitter circuit 100 to
prevent DC bias voltage provided by auxiliary power supply 102 from
flowing back to secondary 110, thereby reducing or mitigating
interference of auxiliary power supply 102 to the resonance of
emitter circuit 100. Preferred value of capacitor 112 can be
sufficiently large compared to capacitance exhibited by emitter
104. According to an embodiment, capacitor 112 can range from about
100 nF to about 0.1 .mu.F, as compared to emitter 104 which can
typically have a capacitance of about 4 nF to about 8 nF; so the
value of capacitor 112 should be substantially greater so as to not
lose significant signal there.
[0033] Transductor 106 can exhibit a pot core that is inherently
shielded to prevent electromagnetic interference or unwanted
radiation. Primary 108 can be operatively connected to an amplifier
(not shown in FIG. 1) which can feed a carrier signal into emitter
circuit 100. Carrier signal can exhibit a sinusoidal AC waveform
which periodically reverses direction and can be modulated with an
input audio signal processed in a signal processing system (not
shown in FIG. 1). Primary 108 can have enough number of turns to
match impedance of the amplifier which can typically range between
about 4.OMEGA. and 12.OMEGA.. Secondary 110 can include an inductor
which can be selected to match impedance of emitter 104.
[0034] As seen from FIG. 1, auxiliary power supply 102 can be
needed to supply a DC bias voltage to emitter 104 for suitable
operation, along with additional wires 116, 118 which are usually
external to emitter circuit 100. These elements can imply
additional operational costs to emitter circuit 100.
[0035] Referring now to FIG. 2, a self-bias emitter circuit 200
does not require the use of auxiliary power supply 102 and wires
116, 118 to provide DC bias voltage to emitter 104, according to an
embodiment.
[0036] Self-bias emitter circuit 200 can include a full-wave bridge
rectifier 202 which can convert the AC carrier signal received by
primary 108 to DC voltage. Full-wave bridge rectifier 202 can
include 4 diodes 204 which can be configured as shown in FIG. 2 to
provide full-wave rectification of AC carrier signal. Two
decoupling capacitors 206 A and 206 B can be placed at each side of
full-wave bridge rectifier 202 to decouple the DC voltage generated
after full-wave rectification. Decoupling capacitors 206 A and 206
B can be small enough to minimize current consumption from
full-wave bridge rectifier 202 and to avoid shunting the AC carrier
signal, preferably in the range of about 0.001 .mu.F.
[0037] While full-wave bridge rectifier 202 can provide
unidirectional voltage, this DC voltage cannot have yet reached a
constant or steady state. In order to provide a steady DC voltage
from the rectified AC carrier signal, a filter capacitor 208 can be
operatively coupled to the output of full-wave bridge rectifier
202. Given that the frequency of a carrier signal can be generally
high, specifically in the range of about 25 kHz to about 60 kHz,
filter capacitor 208 can be sufficiently small, preferably between
about 0.01 .mu.F and about 10 .mu.F. This relatively small filter
capacitor 208 cannot represent a considerable operational cost to
self-bias emitter circuit 200.
[0038] Although filter capacitor 208 can provide a sufficiently
steady DC voltage, this DC voltage cannot be completely smooth as
some ripples can still be present, where these ripples cannot
significantly affect suitable operation of emitter 104.
[0039] A sufficiently steady DC output voltage can now be across
filter capacitor 208 and can be floating because of decoupling
capacitors 206 A and 206 B. Two resistors 114 A and 114 B can be
operatively coupled with filter capacitor 208 to apply suitable DC
bias voltage across emitter 104. Similarly as emitter circuit 100
shown in FIG. 1, self-bias emitter circuit 200 can include
capacitor 112 to prevent the DC bias voltage generated by full-wave
bridge rectifier 202 from flowing back to secondary 110. In
addition, primary 108 can be configured to match impedance of
amplifier (not shown in FIG. 2), while secondary 110 can be
selected to match impedance of emitter 104.
[0040] In another embodiment, it is possible to eliminate either
decoupling capacitor 206 B or resistor 114 B from self-bias emitter
circuit 200 without compromising performance. In such case, primary
108 can be completely isolated from earth ground or amplifier
ground, thus no additional isolation is needed in the form of
decoupling capacitor 206 B or resistor 114 B.
[0041] FIG. 3 illustrates an example of AC to DC conversion 300
that can be performed by self-bias emitter circuit 200. This AC to
DC conversion 300 can be also applicable to other embodiments of
self-bias emitter circuits as described herein.
[0042] In FIG. 3A, an exemplary AC carrier signal 302 can be the
input at primary 108 and can swing from high voltage V.sub.H to low
voltage V.sub.L, where V.sub.H can represent the highest peak of
the AC carrier signal 302, while V.sub.L can represent its
corresponding lowest peak. As such, amplitude of AC carrier signal
302 can be determined by V.sub.H+V.sub.L. According to an
embodiment, amplitude of AC carrier signal 302 with 0% modulation
or no input audio signal can exhibit amplitude of about 150 volts.
When this AC carrier signal 302 is near 100% modulated or mixed
with another input audio signal, amplitude can increase to a range
of about 300 volts to about 600 volts.
[0043] FIG. 3B shows full-wave rectified AC carrier signal 304 that
can be measured at the output of full-wave bridge rectifier 202. In
this full-wave rectified AC carrier signal 304, the V.sub.L swings
of AC carrier signal 302 can be rectified to V.sub.H, thereby
obtaining a signal with unidirectional voltage. However, as shown
in FIG. 3B, V.sub.H peaks of full-wave rectified AC carrier signal
304 cannot yet exhibit a steady or constant DC output.
[0044] Referring now to FIG. 3C, a steady DC bias voltage 306 can
be obtained after filter capacitor 208 decreases the variations of
full-wave rectified AC carrier signal 304. Some variations can be
still present in steady DC bias voltage 306 in the form of ripples
308. However, these ripples 308 can be minimal and cannot
significantly affect suitable application of steady DC bias voltage
306 to emitter 104.
[0045] Suitable steady DC bias voltage 306 can be obtained with 0%
modulation or unmodulated AC carrier signal 302, where amplitude of
steady DC bias voltage 306 can correspond to about V.sub.H peak of
AC carrier signal 302 with 0% modulation. According to an
embodiment, maximum magnitude of steady DC bias voltage 306 applied
to emitter 104 can correspond to maximum V.sub.H peak of 100%
modulation or modulated AC carrier signal 302. As such, self-bias
emitter circuit 200 described herein can operate with AC carrier
signal 302 with 0% modulation or with 100% modulation.
[0046] FIG. 4 shows another self-bias emitter circuit 400 that does
not require the use of auxiliary power supply 102 and wires 116,
118 to provide DC bias voltage to emitter 104, according to an
embodiment. Self-bias emitter circuit 400 can exhibit same or
similar performance as compared to self-bias emitter circuit 200
with the difference that self-bias emitter circuit 400 does not
need full-wave bridge rectifier 202 to provide rectification of AC
carrier signal.
[0047] Self-bias emitter circuit 400 can include transductor 106
with primary 108 matched to amplifier (not shown in FIG. 4) and
secondary 110 matched to emitter 104. Secondary 110 can include a
center tapped inductor which can deliver half-voltage cycles
between center tap 402 and each end of secondary 110, where these
half-voltage cycles between center tap 402 and each end of
secondary 110 can exhibit opposite polarities. Diodes 204 can
provide rectification of both half-voltage cycles across secondary
110, where center tap 402 represent negative output (-), while
positive output (+) can be obtained between diodes 204 as shown in
FIG. 4. Similarly as in self-bias emitter circuit 200, decoupling
capacitors 206 A and 206 B can be placed between secondary 110 and
diodes 204 to decouple the DC voltage generated after full-wave
rectification.
[0048] Output (+/-) can be a DC voltage which can require filtering
in order to achieve a constant or steady state. As such, filter
capacitor 208 can filter output (+/-) and can be operatively
connected to resistors 114 A and 114 B to apply steady DC bias
voltage across emitter 104. Capacitor 112 can still be needed to
prevent DC bias voltage applied across emitter 104 from flowing
back to secondary 110.
[0049] FIG. 5 shows another embodiment of a self-bias emitter
circuit 500 where full-wave bridge rectifier 202 can be used in
conjunction with an additional secondary 502 to provide steady DC
bias voltage to emitter 104.
[0050] Self-bias emitter circuit 500 can include a transductor 106
with primary 108 matched to amplifier (not shown in FIG. 5) and
secondary 110 matched to emitter 104. According to some aspects of
this embodiment, transductor 106 can also include additional
secondary 502 which can share the same magnetically shielded pot
core. Number of turns for additional secondary 502 can be selected
according to the application. For example, number of turns in
additional secondary 502 can be configured for step-up or step-down
operation depending on the required levels of DC bias voltage.
[0051] Additional secondary 502 can be operatively coupled to
full-wave bridge rectifier 202 to convert AC carrier signal
received at primary 108 into DC voltage. Subsequently, this DC
voltage output from full-wave bridge rectifier 202 can be smoothed
by filter capacitor 208 and applied across emitter 104 through
resistors 114 A and 114 B. Self-bias emitter circuit 500 cannot
include decoupling capacitors 206 A and 206 B (as compared to FIG.
2 and FIG. 4) because voltages at secondary 110 and additional
secondary 502 can be isolated from each other. However, capacitor
112 can still be needed to prevent DC bias voltage applied across
emitter 104 from flowing back to secondary 110.
[0052] Referring now to FIG. 6, another embodiment of a self-biased
emitter circuit 600 can include secondary 110 in the form of an
inductor having a section 602 with a higher number of turns and
including an intermediate tap 604, where section 602 can be
operatively connected with full-wave bridge rectifier 202 to
provide steady DC bias voltage to emitter 104.
[0053] In self-bias emitter circuit 600, primary 108 can be
configured to match amplifier (not shown in FIG. 6), while
intermediate tap 604 can configure secondary 110 into two sections,
namely section 602 and section 606. Section 602 can exhibit a
higher number of turns compared to section 606, in which case,
section 602 can provide step-up voltage to full-wave bridge
rectifier 202 as required by the application. Optionally, section
602 can be configured to provide step-down voltage to full-wave
bridge rectifier 202. Section 606, in the other hand, can be
configured with a suitable number of turns to match emitter
104.
[0054] Full-wave bridge rectifier 202 can convert AC carrier signal
at section 602 into a DC voltage, while filter capacitor 208 can
filter this DC voltage and can be operatively connected to
resistors 114 A and 114 B to provide a steady DC bias voltage
across emitter 104. In this embodiment, decoupling capacitors 206 A
and 206 B can be installed at each side of full-wave bridge
rectifier 202 in order to decouple from secondary 110. Similarly to
previous embodiments, capacitor 112 can be required to prevent DC
bias voltage applied across emitter 104 from flowing back to
section 606 of secondary 110.
[0055] FIG. 7 illustrates another embodiment of a self-bias emitter
circuit 700 where a voltage doubler can be used in conjunction with
a filter capacitor 702 in order to provide a steady and increased
DC bias voltage to emitter 104, while also coupling a modulated AC
carrier signal to emitter 104 without significant signal
attenuation. Self-bias emitter circuit 700 can also include a zener
diode 704 to limit the amplitude of the DC bias voltage applied
across emitter 104.
[0056] In self-bias emitter circuit 700, primary 108 can be matched
to amplifier (not shown in FIG. 7), while secondary 110 can be
matched to emitter 104. Voltage doubler can include capacitors 706
and 708, along with diodes 710 and 712. A modulated or unmodulated
AC carrier signal can be received at secondary 110. During the
negative or V.sub.L swing of this AC carrier signal, diode 710 can
begin to conduct, causing capacitor 706 to charge; at the same
time, diode 712 can be reverse biased, preventing the charging of
capacitor 708. Conversely, during the positive or V.sub.H swing of
the AC carrier signal, diode 710 can be reverse biased, while diode
712 can begin to conduct, thereby charging capacitor 708. With both
capacitors 706 and 708 charged, the DC bias voltage across
capacitor 708 can be doubled. According to an embodiment, values
for capacitors 706 and 708 can be determined based on the frequency
of the AC carrier signal. For example, in case of an AC carrier
frequency between about 40 kHz and 50 kHz, capacitors 706 and 708
can typically exhibit a capacitance of about 0.01 .mu.F. In
addition, capacitor 706 can prevent the DC bias voltage from
flowing back to secondary 110.
[0057] Given that the amplitude of the modulated AC carrier signal
can change significantly as music content is played, a zener diode
704 can be installed between resistors 714 and 716 to regulate the
maximum amplitude of the DC bias voltage applied to emitter 104.
For example, a 300 volts zener diode 704 can limit the amplitude of
the DC bias voltage across emitter 104 to about 300 volts. The
maximum amplitude of the DC bias voltage that can be applied to
emitter 104 can be determined based on the materials and thickness
of emitter 104 film.
[0058] Resistors 714 and 716 can be installed as shown in FIG. 7 to
decouple the DC bias voltage and for preventing it from shorting to
the AC carrier signal. Resistor 714 decouples zener diode 704 from
the voltage doubler, while resistor 716 decouples the regulated DC
bias voltage from zener diode 704 to emitter 104. In addition,
resistor 716 also decouples the AC carrier signal from having any
effect on the DC bias voltage applied across emitter 104. Resistors
714 and 716 can exhibit values ranging from about 330 k.OMEGA. to
about 1 M.OMEGA..
[0059] A filter capacitor 702 can be installed as shown in FIG. 7
for smoothing the DC bias voltage applied across emitter 104.
Filter capacitor 702 also provides an effective and continuous
electrical path for the AC carrier signal, specifically from
secondary 110 to the output or emitter 104, without significant
signal attenuation. Filter capacitor 702 can exhibit a capacitance
of about 5 .mu.F, depending on the filtering requirements of the DC
bias voltage applied across emitter 104. Optionally, a diode (not
shown in FIG. 7) can be installed in parallel with filter capacitor
702 in order to prevent any spark from flowing back to filter
capacitor 702, and also for preventing filter capacitor 702 from
switching to wrong or undesired polarity.
[0060] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments are contemplated. The various
aspects and embodiments disclosed herein are for purposes of
illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following claims.
* * * * *