1. A method for operating a cardiac rhythm management device, comprising:
delivering paces to both ventricles with one ventricle designated as a rate chamber and the other ventricle as a synchronized chamber;
sensing depolarizations from the rate chamber;
delivering a rate chamber pace upon expiration of a ventricular escape interval that is reset by a rate chamber sense, the reciprocal of the ventricular escape interval being the lower rate limit;
pacing the synchronized chamber in accordance with a synchronized pacing mode such that a synchronized chamber pace is delivered at a specified pacing instant defined with respect to expiration of the ventricular escape interval;
measuring an R\u2014R interval associated with each rate chamber sense, an R\u2014R interval being the time between a rate chamber sense and a preceding rate chamber sense or pace, with the reciprocal of the R\u2014R interval thus being the measured intrinsic ventricular rate; and,
delivering ventricular rate regularization therapy by adjusting the ventricular escape interval in accordance with a measured R\u2014R interval so that the lower rate limit is adjusted to move toward the measured intrinsic ventricular rate.
2. The method of claim 1 further comprising sensing the rate chamber.
3. The method of claim 1 further comprising:
sensing an atrium;
delivering an atrial pace upon expiration of an atrial escape interval and to deliver a ventricular pace upon expiration of an atrio-ventricular escape interval initiated by an atrial sense.
4. The method of claim 1 further comprising:
detecting ventricular fibrillation based on the sensed ventricular activity; and
applying a ventricular defibrillation shock after detection of fibrillation.
5. The method of claim 4 further comprising initiating ventricular regularization therapy upon detection of ventricular fibrillation.
6. The method of claim 1 further comprising:
detecting atrial fibrillation based on the sensed atrial activity; and
a applying an atrial defibrillation shock after detection of atrial fibrillation.
7. The method of claim 6 further comprising delivering ventricular rate regularization therapy for a specified period of time upon detection of an irregular ventricular tachycardia.
8. The method of claim 1 further comprising:
increasing the ventricular escape interval upon delivery of a ventricular pace; and,
decreasing the ventricular escape interval upon occurrence of a ventricular sense in accordance with the measured R\u2014R interval.
9. The method of claim 1 further comprising adjusting the ventricular escape interval toward a value corresponding to a base lower rate limit after a ventricular pace.
10. The method of claim 1 further comprising adjusting the ventricular escape interval by computing a weighted average of the measured R\u2014R interval multiplied by a scaling factor and the previous value of the ventricular escape interval after each ventricular sense, and wherein the ventricular escape interval is adjusted by multiplying the escape interval by a decay coefficient after a ventricular pace.
11. A cardiac rhythm management device, comprising:
ventricular pacing channels for delivering paces to both ventricles with one ventricle designated as a rate chamber and the other ventricle as a synchronized chamber;
a sensing channel configurable for sensing depolarizations from the rate chamber;
a controller for controlling the delivery of paces by the ventricular pacing channels;
wherein the controller is configured to deliver a rate chamber pace upon expiration of a ventricular escape interval that is reset by a rate chamber sense, the reciprocal of the ventricular escape interval being the lower rate limit;
wherein the controller is programmed to pace the synchronized chamber in accordance with a synchronized pacing mode such that a synchronized chamber pace is delivered at a specified pacing instant defined with respect to expiration of the ventricular escape interval;
wherein the controller is configured to measure an R\u2014R interval associated with each rate chamber sense, an R\u2014R interval being the time between a rate chamber sense and a preceding rate chamber sense or pace, with the reciprocal of the R\u2014R interval thus being the measured intrinsic ventricular rate; and,
wherein the controller is further configured to deliver ventricular rate regularization therapy by adjusting the ventricular escape interval in accordance with a measured R\u2014R interval so that the lower rate limit is adjusted to move toward the measured intrinsic ventricular rate.
12. The device of claim 11
further comprising a sensing channel configurable for sensing the rate chamber.
13. The device of claim 11 further comprising:
atrial sensing and pacing channels;
wherein the controller is configured to deliver an atrial pace upon expiration of an atrial escape interval and to deliver a ventricular pace upon expiration of an atrio-ventricular escape interval initiated by an atrial sense.
14. The device of claim 11 further comprising:
a fibrillation detector for detecting ventricular fibrillation based on the sensed ventricular activity; and
a shock pulse generator for applying a ventricular defibrillation shock after detection of fibrillation.
15. The device of claim 14 wherein the controller is configured to deliver ventricular rate regularization therapy for a specified period of time upon detection of an irregular ventricular tachycardia.
16. The device of claim 11 further comprising:
an atrial fibrillation detector for detecting atrial fibrillation based on the sensed atrial activity; and
an atrial shock pulse generator for applying an atrial defibrillation shock after detection of atrial fibrillation, the shock pulse generator timing the shock based on one or more of the ventricular depolarizations.
17. The device of claim 16 further comprising:
a fibrillation detector for detecting ventricular fibrillation based on the sensed ventricular activity; and
a shock pulse generator for applying a ventricular defibrillation shock after detection of fibrillation.
18. The device of claim 16 wherein the controller is configured to initiate ventricular regularization therapy upon detection of atrial fibrillation.
19. The device of claim 11 further comprising:
an R\u2014R interval detector;
a ventricular escape interval timer;
a filter for increasing the ventricular escape interval upon delivery of a ventricular pace; and,
a filter for decreasing the ventricular escape interval upon occurrence of a ventricular sense in accordance with the measured R\u2014R interval.
20. The device of claim 11 wherein the controller is configured to adjust the ventricular escape interval toward a value corresponding to a base lower rate limit after a ventricular pace.
21. The device of claim 11 wherein the controller is configured to adjust the ventricular escape interval by computing a weighted average of the measured R\u2014R interval multiplied by a scaling factor and the previous value of the ventricular escape interval after each ventricular sense, and wherein the ventricular escape interval is adjusted by multiplying the escape interval by a decay coefficient after a ventricular pace.
22. A cardiac rhythm management device, comprising:
a sensing channel configurable for sensing depolarizations from a right ventricle;
ventricular pacing channels for delivering paces to both right and left ventricles;
a controller for controlling the delivery of paces by the ventricular pacing channels;
wherein the controller is configured to deliver a right ventricular pace upon expiration of a ventricular escape interval that is reset by a right ventricular sense, the reciprocal of the ventricular escape interval being the lower rate limit;
wherein the controller is programmed to pace the left ventricle in accordance with a synchronized pacing mode such that a left ventricular pace is delivered at a specified pacing instant defined with respect to expiration of the ventricular escape interval;
wherein the controller is configured to measure an R\u2014R interval associated with each right ventricular sense, an R\u2014R interval being the time between a right ventricular sense and a preceding right ventricular sense or pace, with the reciprocal of the R\u2014R interval thus being the measured intrinsic ventricular rate; and,
wherein the controller is further configured to deliver ventricular rate regularization therapy by adjusting the ventricular escape interval in accordance with a measured R\u2014R interval so that the lower rate limit is adjusted to move toward the measured intrinsic ventricular rate.
23. The device of claim 22
further comprising a sensing channel configurable for sensing the left ventricle.
24. The device of claim 22 further comprising:
atrial sensing and pacing channels; and,
wherein the controller is configured to deliver an atrial pace upon expiration of an atrial escape interval and to deliver a ventricular pace upon expiration of an atrio-ventricular escape interval initiated by an atrial sense.
25. The device of claim 22 further comprising:
an R\u2014R interval detector;
a ventricular escape interval timer;
a filter for increasing the ventricular escape interval upon delivery of a ventricular pace; and,
a filter for decreasing the ventricular escape interval upon occurrence of a ventricular sense in accordance with the measured R\u2014R interval.
26. The device of claim 22 wherein the controller is configured to adjust the ventricular escape interval by computing a weighted average of the measured R\u2014R interval multiplied by a scaling factor and the previous value of the ventricular escape interval after each ventricular sense, and wherein the ventricular escape interval is adjusted by multiplying the escape interval by a decay coefficient after a ventricular pace.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus, comprising:
a transformer having a primary winding and a secondary winding;
a switching circuit, including a primary active switch and a capacitor commonly coupled in parallel between a primary ground and the primary winding, to facilitate a periodic application of an input voltage to the primary winding;
a synchronous rectification circuit coupled to the secondary winding to generate a rectified signal;
an output filter coupled to the synchronous rectification circuit to provide an output voltage in response to the rectified signal;
the synchronous rectification circuit includes a bi-directional switch coupled in series between the secondary winding and the output filter and a shunt active switch coupled in parallel with the output filter;
a control circuit, coupled to the output filter, the synchronous rectification circuit, and the primary active switch, and responsive to the output voltage to provide a first control signal to the primary active switch to regulate the output voltage by varying a conductive state of the primary active switch;
the control circuit further arranged to provide a second control signal to the bi-directional switch to control a conductive state of the bi-directional switch; and
the conducting state for the bi-directional switch extending for a first time period after an end of the conducting state for the primary active switch.
2. The apparatus according to claim 1, wherein the primary active switch is a switching transistor.
3. The apparatus according to claim 2, wherein the switching transistor is a MOSFET transistor.
4. The apparatus according to claim 1, wherein
the primary active switch of the switching circuit and the bi-directional switch each have a non-conducting state.
5. The apparatus according to claim 1, wherein the conducting state of the primary active switch of the switching circuit and the conducting state of the bi-directional switch begin substantially at a same time instant.
6. The apparatus according to claim 1, wherein the shunt active switch has a conducting state and a non-conducting state; and the conducting state of the bi-directional switch extends for a second time period after a beginning of the conducting state of the shunt active switch.
7. The apparatus according to claim 6, wherein the beginning of the conducting state of the shunt active switch occurs after a dead time period which follows the end of the conducting state of the primary active switch of the switching circuit, with the first time period being longer than the second time period.
8. The apparatus according to claim 1, wherein the the conductive state of the primary active switch determines a duty cycle of the primary active switch.
9. The apparatus according to claim 1, wherein the control circuit, in response to the first control signal, is arranged to modulate an activation time period of the primary active switch of the switching circuit to regulate the output voltage.
10. The power converter of claim 9, wherein the control circuit is further arranged to modulate a trailing edge of the activation time period.
11. The apparatus according to claim 7, wherein the conducting state of the primary active switch of the switching circuit and the conducting state of the bi-directional switch begin substantially at a same time instant.
12. The apparatus according to claim 1, wherein
the control circuit is further arranged to provide a third control signal to the shunt active switch to switch between a pair of states of the shunt active switch, a conducting state and a non-conducting state; and
the conducting state of the bi-directional switch extends for a second time period after a beginning of the conducting state of the shunt active switch.
13. The apparatus according to claim 12, wherein the beginning of the conducting state of the shunt active switch occurs after a dead time period which follows the end of the conducting state of the primary active switch of the switching circuit, with the first time period being longer than the second time period.
14. The apparatus according to claim 12, wherein
the bi-directional switch includes a pair of active switches arranged such that in a non-conducting state each one blocks a current between the secondary winding and the output filter in an opposite direction and in a conducting state each transmits the current; and
the control circuit is further arranged to provide the second control signal to a pair of commonly coupled gates of the pair of active switches to switch between the conducting and the non-conducting states of the pair of active switches.
15. The apparatus according to claim 14, wherein the primary active switch of the switching circuit, the pair of active switches of the bi-directional switch and the shunt active switch are MOSFET transistors.
16. A method, comprising:
applying an input voltage to a first end of a primary winding of a transformer by switching on a primary switching transistor coupled between a second end of the primary winding and a primary ground;
charging a capacitor coupled in parallel with the primary switching transistor by switching off the primary switching transistor;
limiting the charging of the capacitor during a pause period to a voltage level substantially equal to the input voltage by shorting a secondary winding of the transformer;
terminating the shorting of the secondary winding to allow the capacitor to further charge and then discharge through the primary winding;
switching on the primary switching transistor after the capacitor discharges.
17. The method according to claim 16, wherein
the applying of the input voltage to the first end of the primary winding of the transformer includes inducing a positive voltage in a secondary winding of the transformer; and
the limiting of the charging of the capacitor during the pause period to the voltage level substantially equal to the input voltage by shorting the secondary winding of the transformer includes providing a bi-directional switch coupled in series between the secondary winding and an output filter in an on state and a shunt switching transistor coupled in parallel with the output filter in an on state after the primary switching transistor is switched off.
18. The method according to claim 17, wherein the terminating of the shorting of the secondary winding to allow the capacitor to further charge and then discharge through the primary winding includes turning off the bi-directional switch.
19. The method according to claim 18, wherein the inducing of the positive voltage in the secondary winding of the transformer includes turning on the primary switching transistor and the bi-directional switch at the same time.
20. The method according to claim 19, wherein the providing of the bi-directional switch in the on state and the shunt switching transistor in the on state after the primary switching transistor is turned off further includes turning on the shunt switching transistor after the primary switching transistor turns off but before the bi-directional switch turns off.
21. A system, comprising:
an integrated circuit chip including a power converter, the power converter including a transformer having a primary winding and a secondary winding; a switching circuit coupled to the primary winding and adapted to periodically apply an input voltage to the primary winding, the switching circuit including a primary active switch and a capacitor commonly coupled in parallel between a primary ground and the primary winding; a synchronous rectification circuit coupled to the secondary winding to generate a rectified signal; an output filter coupled to the synchronous rectification circuit to provide an output voltage in response to the rectified signal; the synchronous rectification circuit includes a bi-directional switch coupled in series between the secondary winding and the output filter and a shunt active switch coupled in parallel with the output filter; a control circuit, coupled to the output filter, the synchronous rectification circuit, and the primary active switch, and responsive to the output voltage to provide a first control signal to the primary active switch to regulate the output voltage by varying a conductive state of the primary active switch; the control circuit further arranged to provide a second control signal to the bi-directional switch to control a conductive state of the bi-directional switch; and the conducting state for the bi-directional switch extending for a first time period after an end of the conducting state for the primary active switch;
a mass storage device; and
a bus coupled to the integrated circuit chip and the mass storage device.
22. The system according to claim 21, wherein the conducting state of the active switch of the switching circuit and the conducting state of the bi-directional switch begin substantially at a same time instant.
23. The system according to claim 22, wherein the shunt active switch has a conducting state and a non-conducting state; and the conducting state for the bi-directional switch extends for a second time period after a beginning of the conducting state of the shunt active switch.
24. The system according to claim 23, wherein the beginning of the conducting state of the shunt active switch occurs after a dead time period which follows the end of the conducting state of the active switch of the switching circuit, with the first time period being longer than the second time period.
25. The method according to claim 16, further comprising:
varying the pause period to accommodate variations in the input voltage.