Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-07-03
2003-06-03
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C323S234000
Reexamination Certificate
active
06572546
ABSTRACT:
BACKGROUND
This invention relates to power supplies for ultrasound radio frequency (RF) transmitters. In particular, this invention relates to power supplies providing at least two different levels of voltage and instantaneous (peak) power.
Diagnostic medical ultrasound imaging operates in both B-mode and continuous wave (CW) Doppler modes. Two-dimensional B-mode imaging typically uses short transmitted bursts of higher peak voltage and higher peak power than CW Doppler. For B-mode imaging, the transmit sequence along any given ultrasound line occurs over a short period of time, but may have a peak power of hundreds of watts. For CW Doppler mode imaging, the transmitter is substantially constantly transmitting with a lower voltage to prevent excess output power dissipation. The B-mode and CW Doppler mode transmissions are often interleaved.
FIG. 1
shows transmit pulses and associated timing for B-mode and CW Doppler interleaved operation. The amplitude of the transmit signals for the B-mode imaging is greater than the amplitude of the CW Doppler transmit signal.
Different supply voltages may be provided by switches and multiple DC power supplies. The low voltage supply is generally fixed and the HV supply generally variable, but both can be varied, depending on the operation. For example,
FIG. 8
shows a single pole switch
302
that connects a high voltage supply
308
to a diode
306
connected with a low voltage supply
310
. When the switch
302
is open, the transmitter
300
draws current from the low voltage supply
310
through the diode
306
. When the switch
302
is closed, the high voltage supply
308
supplies the current and the diode
306
is reverse biased. A bypass capacitor
314
at the transmitter
300
provides radio frequency bypass to ground and local energy storage to minimize interference to low-level circuitry.
High to low voltage transitions may require dissipation of excess energy stored in the bypass capacitor (e.g., dynamic power dissipation). The amount of energy dissipated is the difference between the high and low voltage squared multiplied by the capacitance, all divided by two.
To avoid such dissipation concerns, conventional ultrasound imaging transmitters use separate power stages for multiple switching schemes. For example, amplifier stages are used. The difference between the supply voltage and the instantaneous output voltage is applied across an amplifier's output. For efficient operation, the amplifier is supplied with a low voltage for low output power and a high voltage only for high output power.
Other arrangements may be used.
FIG. 2
illustrates a multiple power supply amplifier
100
as disclosed in U.S. Pat. No.3,961,280. The amplifier
100
includes an amplifying transistor
102
connected with a load
104
, a switching transistor
106
, a high voltage source
108
, a low voltage source
110
and a diode
112
. The amplifier
100
adjusts the power supply voltage in response to the magnitude of the input signal or the signal to be transmitted. When an input signal
114
is less than the voltage from the low voltage source
110
, the diode
112
is forward biased, and the switching transistor
106
is turned off. The amplifying transistor
102
is powered by the low voltage source
110
. When the input signal
114
is larger than the voltage provided by the low voltage source
110
, the base-emitter junction of the switching transistor
106
becomes conductive, reversing the voltage applied to the diode
112
. The switching transistor
106
conducts the higher voltage from the high voltage source
108
to the load.
As an alternative to detecting the instantaneous magnitude of the input signal for selecting power supplies described above, programmable amplifiers may be used. For example, U.S. Pat. No. 6,078,169 discloses a programmable power supply circuit. Analogous circuitry
200
is shown in
FIG. 3. A
plurality of switches
204
a-d
and power supplies
202
a-d
are provided for selecting and powering a transmit array
208
. A micro-controller
206
controls the switches
204
a-d
to select one of the power sources
202
a-d
. Like
FIG. 2
, excess energy stored in the bypass capacitance of the transmit array is dissipated in a resistor or used to recharge a power source.
BRIEF SUMMARY
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below include ultrasound multi-level power supplies for ultrasound imaging.
In one embodiment, a coupling capacitor is provided indirectly between a high voltage source and a low voltage source. The coupling capacitor provides direct current restoration for a two level power supply selector connected with an ultrasound transmit array.
In a further embodiment, a clamping circuit, including a capacitor and a diode, is provided indirectly between the high voltage and the low voltage sources. The high voltage source connects as a power supply to a pulser. Control signals are provided to the pulser to switch the output between the high voltage and ground depending on the type of ultrasound signal being transmitted. A voltage rail of the transmit array connects with the clamp circuit and receives a low voltage for CW Doppler mode imaging and a higher voltage for B-mode imaging. This low cost circuitry may simplify and improve the delivery of high voltage in a two level power supply selection in ultrasound imaging.
In a first aspect, a two level power supply for ultrasound imaging is provided. A coupling capacitor is connected indirectly between first and second voltage supplies. The second voltage supply has a higher voltage than the first voltage supply. At least one ultrasound transmit element operatively connects with the first and second voltage supplies.
In a second aspect, another two-level power supply for ultrasound imaging is provided. A plurality of ultrasound transmit cells connects with a voltage rail. A capacitor-coupled clamp circuit also connects with the voltage rail. A bias port of the capacitor coupled clamp circuit connects with a first voltage supply. An input of the capacitor coupled clamp circuit connects with a pulser. A second voltage supply provides power to the pulser.
In a third aspect, a method for providing power in an ultrasound imaging system is provided. A higher voltage is applied to an ultrasound transmit element. A lower voltage is then applied to the ultrasound transmit element. During generation of the lower voltage, direct current is restored for subsequent repetition of the generation of the higher voltage. The lower voltage characterizes the level of restoration.
In a fourth aspect, a method for providing power in an ultrasound imaging system is provided. High and low voltages are supplied. A high transmit voltage is generated and comprises the sum of the high and low voltages. A low transmit voltage is generated comprising the low voltage. During generation of the high transmit voltage, a capacitor is discharged. The capacitor is recharged with the low voltage.
Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments.
REFERENCES:
patent: 3961280 (1976-06-01), Sampei
patent: 4099139 (1978-07-01), Oguri
patent: 4581590 (1986-04-01), Sunderland
patent: 4852577 (1989-08-01), Smith et al.
patent: 5103157 (1992-04-01), Wright
patent: 5496411 (1996-03-01), Candy
patent: 6045506 (2000-04-01), Hossack
patent: 6078169 (2000-06-01), Petersen
Wu, Albert M. and Sanders, Seth R., An Active Clamp Circuit for Voltage Regulation Module (VRM) Applications, IEEE Transactions on Power Electronics, vol. 16, No. 5, Sep., 2001, p. 623-634.*
Donald G. Fink and Donald Christiansen, Electronics Engineers' Handbook, p. 16-9 and 16-10, 1989.
Bax Ronald F.
Shifrin Lazar A.
Acuson Corporation
Jaworski Francis J.
Jung William C
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