U.S. patent application number 12/869406 was filed with the patent office on 2010-12-23 for complementary high voltage switched current source integrated circuit.
Invention is credited to Benedict C.K. Choy.
Application Number | 20100321089 12/869406 |
Document ID | / |
Family ID | 43353771 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100321089 |
Kind Code |
A1 |
Choy; Benedict C.K. |
December 23, 2010 |
COMPLEMENTARY HIGH VOLTAGE SWITCHED CURRENT SOURCE INTEGRATED
CIRCUIT
Abstract
A complementary high voltage switched current source circuit has
a complementary current source pair, wherein a first of the current
source pair is coupled to a positive voltage rail and a second of
the current source pair is coupled to a negative voltage rail. A
digital logic-level control interface circuit is coupled to the
complementary current source pair and to the positive voltage rail
and the negative voltage rail. A pair of high voltage switches is
coupled to the complementary current source pair and the digital
logic-level control interface circuit and controlled by the digital
control interface circuit.
Inventors: |
Choy; Benedict C.K.;
(Cupertino, CA) |
Correspondence
Address: |
WEISS & MOY PC
4204 NORTH BROWN AVENUE
SCOTTSDALE
AZ
85251
US
|
Family ID: |
43353771 |
Appl. No.: |
12/869406 |
Filed: |
August 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12434862 |
May 4, 2009 |
|
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12869406 |
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Current U.S.
Class: |
327/427 |
Current CPC
Class: |
H03K 5/05 20130101; H03K
3/021 20130101; H03F 3/217 20130101; H03K 17/6872 20130101; G01S
7/5202 20130101; H03K 3/64 20130101 |
Class at
Publication: |
327/427 |
International
Class: |
H03K 17/687 20060101
H03K017/687 |
Claims
1. A complementary high voltage switched current source circuit
comprising: a complementary current source pair; a digital
logic-level control interface circuit coupled to the complementary
current source pair and to a positive voltage rail and a negative
voltage rail; and a pair of high voltage switches coupled to the a
complementary current source pair, the digital logic-level control
interface circuit and controlled by the digital control interface
circuit.
2. A complementary high voltage switched current source circuit in
accordance with claim 1 further comprising a plurality of
multi-channel high voltage switched current sources coupled
together.
3. A complementary high voltage switched current source circuit in
accordance with claim 1 wherein the complementary current source
pairs are approximately matched for generating low harmonic
waveform for one of ultrasound image system or Class-D audio
applications.
4. A complementary high voltage switched current source circuit in
accordance with claim 1 wherein the complementary current source
pair comprises: a pair of P-type MOSFETs coupled to the digital
logic-level control interface circuit and to the high voltage
switches; and a pair of N-type MOSFETs coupled to the digital
logic-level control interface circuit and to the high voltage
switches.
5. A complementary high voltage switched current source circuit in
accordance with claim 1 wherein the complementary current source
pair comprises: a first P-type MOSFET coupled to the digital
logic-level control interface circuit and to the high voltage
switches; a first N-type MOSFET coupled to the first P-type MOSFET,
to the digital logic-level control interface circuit, and to a
first high voltage switch; a second P-type MOSFET coupled to the
digital logic-level control interface circuit and to the high
voltage switches; and a second N-type MOSFET coupled to the second
P-type MOSFET, to the digital logic-level control interface
circuit, and to a second high voltage switch.
6. A complementary high voltage switched current source circuit in
accordance with claim 5 wherein the digital logic-level control
input circuit comprises: a pair of capacitive elements, wherein a
first of the pair of capacitive elements is coupled to a first
control waveform and to the first N-type MOSFET, and a second of
the pair of capacitive elements is coupled to a second control
waveform and to the second N-type MOSFET; a pair of Zener diodes,
wherein a first of the pair of Zener diodes is attached to the
first control waveform, to the first N-type MOSFET, and to the
positive voltage rail and a second of the pair of Zener diodes
attached to the second control waveform, to the second N-type
MOSFET, and to the negative voltage rail; a first pair of resistive
elements, wherein a first of the first pair of resistive element is
in parallel with the first Zener diode, and a second of the first
pair of resistive element is in parallel with the second Zener
diode; a second pair of resistive elements, wherein a first of the
second pair of resistive element is coupled to the first P-type
MOSFET and the first N-type MOSFET, and a second of the second pair
of resistive element is coupled to the second P-type MOSFET and the
second N-type MOSFET; and a pair of switching diodes, wherein a
first of the pair of switching diodes is coupled to the first of
the second pair of resistors and to the first P-type MOSFET, and s
second of the pair of switching diodes is coupled to the second of
the second pair of resistors and to the second P-type MOSFET.
7. A complementary high voltage switched current source circuit
comprising: a complementary current source pair; a digital
logic-level control interface circuit coupled to the complementary
current source pair and to a positive voltage rail and a negative
voltage rail; and a pair of high voltage switches coupled to the a
complementary current source pair, the digital logic-level control
interface circuit and controlled by the digital control interface
circuit; wherein the complementary current source pair comprises: a
first P-type MOSFET coupled to the digital logic-level control
interface circuit and to the high voltage switches; a first N-type
MOSFET coupled to the first P-type MOSFET, to the digital
logic-level control interface circuit, and to a first high voltage
switch; a second P-type MOSFET coupled to the digital logic-level
control interface circuit and to the high voltage switches; and a
second N-type MOSFET coupled to the second P-type MOSFET, to the
digital logic-level control interface circuit, and to a second high
voltage switch.
8. A complementary high voltage switched current source circuit in
accordance with claim 7 further comprising a plurality of
multi-channel high voltage switched current sources coupled
together.
9. A complementary high voltage switched current source circuit in
accordance with claim 7 wherein the complementary current source
pairs are approximately matched for generating low harmonic
waveform for one of ultrasound image system or Class-D audio
applications.
10. A complementary high voltage switched current source circuit in
accordance with claim 7 wherein the complementary current source
pair comprises: a first P-type MOSFET coupled to the digital
logic-level control interface circuit and to the high voltage
switches; a first N-type MOSFET coupled to the first P-type MOSFET,
to the digital logic-level control interface circuit, and to a
first high voltage switch; a second P-type MOSFET coupled to the
digital logic-level control interface circuit and to the high
voltage switches; and a second N-type MOSFET coupled to the second
P-type MOSFET, to the digital logic-level control interface
circuit, and to a second high voltage switch.
11. A complementary high voltage switched current source circuit in
accordance with claim 7 wherein the digital logic-level control
input circuit comprises: a pair of capacitive elements, wherein a
first of the pair of capacitive elements is coupled to a first
control waveform and to the first N-type MOSFET, and a second of
the pair of capacitive elements is coupled to a second control
waveform and to the second N-type MOSFET; a pair of Zener diodes,
wherein a first of the pair of Zener diodes is attached to the
first control waveform, to the first N-type MOSFET, and to the
positive voltage rail and a second of the pair of Zener diodes
attached to the second control waveform, to the second N-type
MOSFET, and to the negative voltage rail; a first pair of resistive
elements, wherein a first of the first pair of resistive element is
in parallel with the first Zener diode, and a second of the first
pair of resistive element is in parallel with the second Zener
diode; a second pair of resistive elements, wherein a first of the
second pair of resistive element is coupled to the first P-type
MOSFET and the first N-type MOSFET, and a second of the second pair
of resistive element is coupled to the second P-type MOSFET and the
second N-type MOSFET; and a pair of switching diodes, wherein a
first of the pair of switching diodes is coupled to the first of
the second pair of resistors and to the first P-type MOSFET, and s
second of the pair of switching diodes is coupled to the second of
the second pair of resistors and to the second P-type MOSFET.
Description
RELATED APPLICATIONS
[0001] The present application is a divisional of pending U.S.
patent application entitled: "COMPLEMENTARY HIGH VOLTAGE SWITCHED
CURRENT SOURCE INTEGRATED CIRCUIT", Ser. No. 12/434,862, filed May
4, 2009, and in the name of the same inventors.
FIELD OF THE INVENTION
[0002] This invention relates generally to an ultrasound scanning
image system, and more particularly, to an array of high voltage
switched current sources for a high voltage ultrasound transmit
pulse generator to excite the piezoelectric or
capacitive-electrostatic elements in the ultrasound transducer
probe in an ultrasound B-scan or a color image system.
BACKGROUND OF THE INVENTION
[0003] Ultrasound medical imaging or nondestructive testing (NDT)
application have a growing demand for more sophisticated excitation
waveforms and sequential scanning method for large number of
piezoelectric or capacitive-electrostatic elements array. The
commonly used ultrasound transmit pulse generator circuit generally
consist of a pair of P-type and N-type high voltage power MOSFETs
driven by a very fast and powerful gate driver circuit. Each
channel of the pulse generator needs to produce high voltage and
high current to charge or discharge the load capacitance at
ultrasound frequency or speed. The load capacitance, including the
piezoelectric or capacitive-electrostatic elements and the cable
equivalent capacitance, usually is quite large. The advanced
harmonic ultrasound imaging technology requires that the waveform
generated from this pulse generator contains the least amount of
second harmonics as possible.
[0004] Therefore, a need existed to provide a system and method to
overcome the above problem. The system and method it would be
desirable to provide a transmit pulse generating circuit and method
that can produce well matched rising and falling edges would allow
registered users the ability of adding content, contests and
promotions to web properties.
SUMMARY OF THE INVENTION
[0005] A complementary high voltage switched current source circuit
has a complementary current source pair, wherein a first of the
current source pair is coupled to a positive voltage rail and a
second of the current source pair is coupled to a negative voltage
rail. A digital logic-level control interface circuit is coupled to
the complementary current source pair and to the positive voltage
rail and the negative voltage rail. A pair of high voltage switches
is coupled to the a complementary current source pair and the
digital logic-level control interface circuit and controlled by the
digital control interface circuit.
[0006] The present invention is best understood by reference to the
following detailed description when read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a schematic diagram illustrating a conventional
prior art complementary MOSFETs ultrasound transmitter pulse
generator in a typical ultrasound B-scan image system;
[0008] FIG. 2 is a schematic diagram illustrating a transmit pulse
generate channels for a 2-level ultrasound transducer excitation
waveform integrated device circuit;
[0009] FIG. 3 is a schematic diagram illustrating a circuit
architecture topology of a 5-level ultrasound transducer excitation
waveform integrated device circuit;
[0010] FIG. 4 is a schematic detail diagram illustrating a circuit
architecture topology of an ultrasound pulse generator using N-type
MOSFETs for both positive going and negative going current
switches;
[0011] FIG. 5 is a schematic detail diagram illustrating both
output MOSFETs in the high voltage switched current source of the
transmit pulse generator in FIG. 4 being replaced by bipolar
transistors;
[0012] FIG. 6 is a schematic detail diagram illustrating a smaller
switched current source to control the output MOSFETs in the
transmit pulse generator;
[0013] FIG. 7 is a schematic detail diagram illustrating both
output MOSFETs in a high voltage switched current source of the
transmit pulse generator in FIG. 6 replaced with bipolar
transistors; and
[0014] FIG. 8 is a schematic detail diagram of a high voltage
switched current source of the transmit pulse generator wherein the
high voltage MOSFETs are source driven.
[0015] Common reference numerals are used throughout the drawings
and detailed description to indicate like elements.
DETAILED DESCRIPTION
[0016] Referring to FIG. 1, a schematic diagram illustrating a
conventional prior art complementary MOSFETs ultrasound transmitter
pulse generator 100 (hereinafter pulse generator 100) in a typical
ultrasound B-scan image system is shown. In the pulse generator
100, the source terminals of the P-type MOSFET 104 and N-type
MOSFET 111 are connected to the positive and negative high voltage
power supply rail 105 and 110 respectively. The gate terminals of
the P-type MOSFET 104 and N-type MOSFET 111 are each connected to
one of a pair of gate coupling capacitors 115. The pair of gate
coupling capacitors 115 are driven by control waveforms 116
generated by a gate driver circuit.
[0017] The pulse generator 100 has a pair of Zener diodes 101 and
114. The Zener diodes 101 and 114 have a first terminal coupled to
the positive and negative high voltage power supply rail 105 and
110 respectively and a second terminal coupled to one of the pair
of gate coupling capacitors 115. The Zener diodes 101 and 114 are
in parallel with gate-source DC bias voltage resistors 102 and 113
respectively.
[0018] The forward direction of the Zener diodes 101 and 114 serve
as the fast DC restoring diodes function for the AC capacitor
coupling gate driving circuit, while the Zener diodes break-down
direction protecting the possible over voltage of MOSFET gate to
source voltages. The pair of switching diodes 109 work as the
revise voltage blocking as well as the ultrasound receiver
isolation propose. In the 2-level transmit pulse generator circuit
the resistor 108 in parallel with the transducer 107, discharge the
capacitance of the transducer back to zero voltage after the
waveform transmitted. A typical waveform 106 is shown in the FIG.
1.
[0019] In advanced ultrasound harmonic medical imaging systems, it
is required to generate the least amount of second harmonics in the
waveform as possible. Therefore to reduce the amount of second
harmonics in the waveform, one should try and match the pulse rise
and fall edges, as well as the pulse positive and negative duration
timing and pulse amplitudes.
[0020] Because of device physics, even using the most current up to
date state of art manufacturing processes, it is extremely
difficult and cost prohibitive to make matching P-type and N-type
MOSFETs having the same size or same current or characteristics.
Presently, to approximately match the MOSFET voltage and current,
the P-type MOSFET is generally two to three times bigger the N-type
MOSFET, when having complementary MOSFET pair in current ultrasound
applications.
[0021] Referring now to FIG. 2, one embodiment of a complementary
switched current source circuit 200 is shown. The circuit 200 has a
pair of gate coupling capacitors 215A and 215B. Each of the pair of
gate coupling capacitors 215 has a first terminal coupled to a
waveform 216. Each of the coupling capacitors 215 is driven by the
control waveform 216 which is generated by a gate driver circuit.
The circuit 200 has a P-type MOSFET 204 and N-type MOSFET 211 each
having drain, gate and source terminals. The gate terminals of the
P-type MOSFET 204 and N-type MOSFET 211 are each connected to a
second terminal of one of the pair of gate coupling capacitors 215.
The circuit 200 has a pair of Zener diodes 201 and 214. The Zener
diodes 201 and 214 have a first terminal coupled to the positive
and negative high voltage power supply rail 205 and 210
respectively and a second terminal coupled to one of the pair of
gate coupling capacitors 215. The Zener diodes 101 and 114 are in
parallel with gate-source DC bias voltage resistors 202 and 213
respectively. The Zener diodes 201 and 214 serve the same function
as they are in FIG. 1. The circuit 200 has a pair of switching
diodes 209. The switching diodes 209 each has a first terminal
coupled to one of the drain terminals of the P-type MOSFET 204 and
N-type MOSFET 211 and a second terminal coupled to a resistor 208
coupled in parallel with a transducer 207.
[0022] The circuit 200 uses two well matched depletion current
control devices 203 and 212 in series with the source terminals of
the P-type MOSFET 204 and N-type MOSFET 211 respectively and power
supply rails 205 and 210 respectively. The addition of the control
devices 203 and 212 provides much tight current matching between
positive and negative going current when the MOSFET switch 204 or
211 is activated.
[0023] Referring now to FIG. 3, a 5-level ultrasound transmit pulse
generator circuit 300 is shown. The circuit 300 is formed of a
plurality of circuits 200 coupled together. In the present
embodiment, three circuits 200 are used wherein the circuits are
numbered 301, 302 and 303. The voltage supplies 305a and 310a have
different absolute voltage value as the 305b and 310b to generate
four waveform levels, when the pulse generate circuit 301 is
activated followed by activation of the circuit 302. The "return to
zero" function is provided by the third circuit 303 when the
"supply voltage" rails are both connect to zero volt or ground. The
typical waveform this circuit can generate is shown in the waveform
306 in the FIG. 3.
[0024] Referring now to FIG. 4, a complementary switched current
source circuit 400 is shown. The circuit 400 has a pair of gate
coupling capacitors 415A and 415B. Each of the pair of gate
coupling capacitors 415A and 415B has a first terminal coupled to a
waveform 216. Each of the coupling capacitors 415A and 415B is
driven by the control waveform 216 which is generated by a gate
driver circuit.
[0025] The circuit 400 uses small P-type MOSFETs 417 and small
N-type MOSFET 419 with a pair of N-type MOSFET 404 and 411. This
arrangement replaces the complementary P-type MOSFET 204 and N-type
MOSFET 211 of FIG. 2. The benefit of this novel implementation is
twofold. Not only does this configuration save lot of silicon area,
since to approximately match the MOSFET voltage and current, the
P-type MOSFET is generally two to three times bigger the N-type
MOSFET, but it also reduces the gate driver current.
[0026] The P-type MOSFETs 417 and 419 each have a gate terminal
coupled to one the coupling capacitors 415A and 415B respectively.
Each P-type MOSFET 417 and 419 is further coupled to a resistive
element 418 and 420 respectively. The pair of N-type MOSFETs 404
and 411 are each connected in series with current control devices
403 and 412 respectively and power supply rails 405 and 410
respectively. Each of the pair of N-type MOSFETs 404 and 411 is
further coupled to one of the P-type MOSFET 417 and 419.
[0027] The circuit 400 has a pair of Zener diodes 401 and 414. The
Zener diodes 401 and 414 have a first terminal coupled to the
positive and negative high voltage power supply rail 405 and 410
respectively and a second terminal coupled to one of the pair of
gate coupling capacitors 415A or 415B. The Zener diodes 401 and 414
are in parallel with gate-source DC bias voltage resistors 402 and
413 respectively. The Zener diodes 401 and 414 serve the same
function as they do in the previous embodiments.
[0028] The circuit 400 has a pair of switching diodes 409. The
switching diodes 409 each has a first terminal coupled to one of
the N-type MOSFETs 404 or 411 and a second terminal coupled to a
resistor 408. The resistor 408 is coupled in parallel with a
transducer 407.
[0029] As previously stated, the benefit of this novel
implementation is twofold. Not only does this configuration save
lot of silicon area, since to approximately match the MOSFET
voltage and current, the P-type MOSFET is generally two to three
times bigger the N-type MOSFET, but it also reduces the gate driver
current.
[0030] Referring to FIG. 5, another embodiment of a complementary
switched current source circuit 500 is shown. This embodiment is
similar to that shown in FIG. 4, thus the differences will be
discussed. In the present embodiment, two bipolar transistor
devices 504 and 511 are used and replace the MOSFETs 404 and 411 in
FIG. 4. By using the bipolar transistor devices 504 and 511, one is
able to further reduce the die size of the integrated circuit of
the previous embodiments.
[0031] Referring now to FIG. 6, another complementary switched
current source circuit 600 is disclosed. The circuit 600 is similar
to that shown in FIG. 4. However, circuit 600 uses smaller current
sources 603 and 612 and smaller control switchers 617 and 619 for
regulating the currents passing through the matched resistors 618
and 620 to control the matched output N-type of MOSFETs 604 and
611, to generate the matched, or almost matched output
charge/discharge currents via 609 diodes. Because of the current
sources and control switches are both smaller, the present
embodiment will further save the circuit silicon die area.
[0032] Referring now to FIG. 7, another complementary switched
current source circuit 700 is disclosed. The circuit 700 is similar
to that shown in FIG. 6. In the present embodiment, the output
MOSFETs 604 and 611 are replaced by bipolar transistors 704 and
711. This topology can further save the circuit silicon die area in
the integrated circuit.
[0033] Referring now to FIG. 8, another complementary switched
current source circuit 800 is disclosed. The circuit 800 is similar
to that shown in FIG. 6. However, in FIG. 8, the output MOSFETs 804
and 811 are source-driven. That means that the output MOSFET gates
are kept at a fixed gate voltages of +VG and -VG supplied by 821
and 822. In this topology the source-driver circuit components 817,
803, 819 and 812 can be low voltage components. The circuit 800 not
only saves the high voltage components, but also speed up the
current rise and fall timings due to the source-driving
topology.
[0034] While embodiments of the disclosure have been described in
terms of various specific embodiments, those skilled in the art
will recognize that the embodiments of the disclosure can be
practiced with modifications within the spirit and scope of the
claims.
* * * * *