Waveform generator for electrosurgical apparatus

• US 4,961,739 A
• Filed: 03/07/1988
• Issued: 10/09/1990
• Est. Priority Date: 03/07/1988
• Status: Expired due to Term

• Current Assignee: Aspen Laboratories, Inc. (Jefferies Financial Group, Inc.)
• Original Assignee: Aspen Laboratories, Inc. (Jefferies Financial Group, Inc.)
• Inventors: Thompson, Richard K.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): Shay, David
• Application Number:
  US07/165,143
• Time in Patent Office: 946 Days
• Field of Search: 128/303.13, 128/303.14, 128/303.17, 606/37-40
• US Class Current: 606/37
• CPC Class Codes: A61B 18/12 by passing a current through the tissue to be heated, e.g. high-frequency current
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/00684 using lookup tables

Abstract

A waveform generator for electrosurgical apparatus disclosed includes a MxNxP storage device and a parallel to series conversion device. For the storage device, M is the maximum number of different waveforms being stored, N equals the number of bits being output from the storage device at a time and P is the maximum number of N bits that can be stored for each waveform. An address counter selects the next N bits of the waveform and these N bits loaded from the storage device into the conversion device and output in a sequential or series output signal to drive the RF power amplifier of electrosurgical apparatus. The output signal has a bit rate N times faster than the storage device is accessed.

Claims

1. A waveform generator for controlling the waveform and power output of electrosurgical apparatus, said waveform generator comprising:

a clock for providing a REFERENCE FREQUENCY signal,

a counter responsive to said REFERENCE FREQUENCY signal that counts to a selected number and then provides a SHIFT REGISTER LOAD signal,

an address counter responsive to a N BITS OF THE WAVEFORM signal and to said SHIFT REGISTER LOAD signal, said address counter providing a COUNTER LOAD signal and a SUBADDRESS signal for selecting each N bit word,

an MxNxP storage means for storing waveforms where M is the maximum number of a plurality of different waveforms being stored, each waveform having a maximum length of N times P, N equals the number of a plurality of bits being output in parallel from the storage means at a time and P is the maximum number of a plurality of N bits stored for each waveform, said storage means having input address lines for selecting each waveform and a plurality of parallel output lines for providing a N bits of the waveform at a time, and

said address counter having a counter modulus, said counter modulus being set by preloading a selected count from said storage means which selected count provides a waveform of a selected repetition frequency over a range of frequencies, reading a full count and counting to zero, as upper bit of said address counter going to zero and reloading the preloaded count,

a parallel to serial shift register loaded by the N bits of the waveform in response to said SHIFT REGISTER LOAD signal, said COUNTER LOAD signal, and said REFERENCE FREQUENCY signal for converting the N bits of the waveform to a SINGLE BIT SERIAL WAVEFORM output signal for controlling power output, said output signal being selected by said SUBADDRESS signal at a speed determined by said REFERENCE FREQUENCY signal, said output signal having a maximum bit output time N times faster than the read access time of said storage means.

2. A waveform generator as set forth in claim 1 wherein said REFERENCE FREQUENCY signal is 20MHz and each bit is 50 nanoseconds in duration.

3. A waveform generator as set forth in claim 1, wherein the shift register is loaded N bits at a time and shifted out one bit at a time.

4. A waveform generator as set forth in claim 1 wherein there are eight parallel lines into said shift register.

5. A waveform generator as set forth in claim 1 wherein there are eight address lines into said storage means.

6. A waveform generator as set forth in claim 1 wherein said output signal from said shift register is applied to a buffer before being coupled to a RF power amplifier of the electrosurgical apparatus.

7. A waveform generator as set forth in claim 6 wherein N equals eight.