1498 results about "Average current" patented technology

A surgical instrument includes a surgical end effector having at least one actuation assembly to effect a surgical procedure when actuated, an electric motor operationally connected to the end effector to operate the at least one actuation assembly, and a power supply electrically connected to the motor and selectively powering the motor to actuate the actuation assembly. The power supply has a battery cell with a critical current rate and, when activated to power the motor and actuate the actuation assembly, operates the cell at a super-critical current rate or at an average current rate above the critical current rate. The power supply selectively powers the motor to actuate the assembly less than 16 times during a clinical life of at least one of the end effector, the motor, and the power supply. When actuated, the assembly operates only between 0.5 seconds and 16 seconds in duration.

Exemplary apparatus, method and system embodiments provide for separately and independently sourcing current to a series of light emitting diodes of a plurality of series of light-emitting diodes. An exemplary apparatus comprises a power converter which generates a current, a first multiplexer, and a controller. The controller provides for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes for a corresponding period of time. An average current provided by the power converter is determined as substantially equal to a sum of the corresponding currents through the plurality of series of light-emitting diodes. A total period for switching current to all of the series of light-emitting diodes is also determined. A corresponding time period for switching current to a selected corresponding series of light-emitting diodes is substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

A control circuit controlling output current at the primary side of a power converter is provided. A waveform detector generates a current-waveform signal. A discharge-time detector detects a discharge-time of a secondary side switching current. An oscillator generates an oscillation signal for determining the switching frequency of the switching signal. An integrator generates an integrated signal by integrating an average current signal with the discharge-time. The average current signal is generated in response to the current-waveform signal. The time constant of the integrator is correlated with the switching period of the switching signal, therefore the integrated signal is proportional to the output current. An error amplifier amplifies the integrated signal and provides a loop gain for output current control. A comparator controls the pulse width of the switching signal in reference to the output of the error amplifier. Therefore, the output current of the power converter can be regulated.

Methods and apparatus are provided for determining the duty cycle, average amperage, and / or the number of arc starts during a welding operation. The apparatus comprises first and second circuits, the first circuit being a CPU control circuit, and the second circuit being an arc time sensor circuit which is programmed to measure amperage, welding wire feed speed and preferably gas flow rates while welding. A ratio of the cumulative welding time during the audit to the total on-time provides a measurement of the efficiency of the welding arc. The welding deposition efficiency may then be calculated using the average amperage and welding duty cycle as measured and calculated by the apparatus. The number of arc starts where the arc on-time is in excess of one second may also provide a useable measurement in giving secondary information on the overall efficiency of the welding operation.

An exemplary apparatus embodiment provides for controlling current supplied to solid state lighting, such as light emitting diodes. An exemplary apparatus comprises a memory adapted to store a plurality of current parameters; and a control circuit adapted to modulate an energizing cycle time period for providing a substantially constant DC average current to the solid state lighting in response to a selected current parameter of the plurality of current parameters. In an exemplary embodiment, the control circuit modulates a current provided to the solid state lighting in response to a predetermined minimum current level (IMIN) parameter and a predetermined peak current level (IP) parameter, such that the DC average current level (IO) is substantially proportional to one-half of a sum of a predetermined peak current level (“IP”) and a predetermined minimum current levelIM(IO∝IP+IMIN2).

An apparatus, method and system are provided for controlling the solid state lighting, such as LEDs. An exemplary apparatus comprises: a switch for switching electrical current through the LEDs, a current sensor; a first comparator adapted to determine when a switch electrical current has reached a first predetermined threshold; a second comparator adapted to determine when the switch electrical current has reached a predetermined average current level; and a controller. The controller is adapted to turn the switch into an on state and an off state, to determine a first on time period as a duration between either a detection of a second predetermined current threshold or the turning the switch into the on state, and the detection of the predetermined average current level; to determine a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold; and to determine an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period. Additional exemplary embodiments utilize a difference between the first and second on time periods to generate an error signal to adjust the on time period of the switch.

The throttle of an engine in an engine driven generator system operating under an intermittently heavy load, as in supplying current to a welder, is controlled such that successive control signals sent to a throttle actuator for adjusting the engine throttle position are inhibited until at least a predetermined time has elapsed since the last preceding adjustment to the throttle. This procedure ensures that, as to each incremental adjustment to the throttle, the engine has sufficient time to respond, thereby preventing over-speeding or stalling the engine. The throttle actuator may be a stepper motor which is stepped by throttle position change signals from a processor which monitors engine speed and generator load to determine whether the throttle should be adjusted and, if so, in which direct. Alternatively, the throttle actuator may be a solenoid pulling against a spring in accordance with the average current through the solenoid coil. In this embodiment, the processor causes pulse width modulated signals to be applied across the solenoid coil with throttle position changes being reflected in changes to the width of the pulses, such changes in the pulse width being delayed for at least the predetermined time since the last preceding adjustment to the throttle.

The throttle of an engine in an engine driven generator system operating subject to a wide and rapidly variable load, as in supplying current to a welder, is operated such that control signals are sent to a throttle actuator for adjusting the engine throttle position in response to load changes. The throttle actuator may be a solenoid pulling against a spring in accordance with the average current through the solenoid coil. In this embodiment, the processor causes pulse width modulated signals to be applied across the solenoid coil with throttle position changes being reflected in changes to the width of the pulses, such changes in the pulse width being delayed for at least the predetermined time since the last preceding adjustment to the throttle. Alternatively, the throttle actuator may be a stepper motor which is stepped by throttle position change signals from a processor which monitors engine speed and generator load to determine whether the throttle should be adjusted and, if so, in which direction and to what extent for optimum response.

In a method and apparatus for controlling power factor correction in mixed operation modes, a frequency of the input voltage is obtained by detecting the zero crossing points of the input voltage. A peak of the input voltage is obtained by detecting input voltage with 90 degree phase. Thus, the present invention predicts the input voltage by its frequency and peak and the characteristic of the sine wave. A digital signal processor computes the duty and frequency of a boost switch, switching the operation mode of the boost converter among continuous mode, critical mode and discontinuous mode according to input voltage or the load. According to another aspect, the operation is switched to critical mode from the average current mode when a zero current is detected before the charging and recharging cycle of the boost switch is finished.

An apparatus, method and system are provided for controlling the solid state lighting, such as LEDs. An exemplary apparatus comprises: a switch for switching electrical current through the LEDs, a current sensor; a first comparator adapted to determine when a switch electrical current has reached a first predetermined threshold; a second comparator adapted to determine when the switch electrical current has reached a predetermined average current level; and a controller. The controller is adapted to turn the switch into an on state and an off state, to determine a first on time period as a duration between either a detection of a second predetermined current threshold or the turning the switch into the on state, and the detection of the predetermined average current level; to determine a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold; and to determine an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period. Additional exemplary embodiments utilize a difference between the first and second on time periods to generate an error signal to adjust the on time period of the switch.

A dimmable, light-emitting diode (LED) power supply adapted to provide a direct current (DC), constant current (“constant current source”) from a conventional, phase-controlled 120 VAC, 60 Hz power source is disclosed. The constant current source of the present invention utilizes two processes to control dimming. In a first process, the phase angle of the input voltage is used to control the duty cycle of a line frequency pulse width modulation (PWM). In a second process, a proportional-current limit adjustment is used to control the average current to the LED during the ON time of the line frequency by PWM. As a result, at relatively low phase angles, peak currents can be lowered, reducing flicker and improving the audible noise levels generated by the circuit.

Exemplary embodiments provide a system, method and apparatus for regulating current in loads, such as in an array of independent pluralities of light emitting diodes (“LEDs”). An exemplary system comprises a multiplexer adapted to switch current to each independent string of LEDs; a first controller to maintain a substantially constant average current level to the plurality of LEDs; and a second controller to modulate a current amplitude and duration of time division multiplexing for each independent string of LEDs. Another aspect of the system provides for modulating the on time for switching current to maintain a substantially constant average current level and to respond and converge quickly to changing current reference levels.

Exemplary apparatus, method and system embodiments provide for separately and independently sourcing current to a series of light emitting diodes of a plurality of series of light-emitting diodes. An exemplary apparatus comprises a power converter which generates a current, a first multiplexer, and a controller. The controller provides for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes for a corresponding period of time. An average current provided by the power converter is determined as substantially equal to a sum of the corresponding currents through the plurality of series of light-emitting diodes. A total period for switching current to all of the series of light-emitting diodes is also determined. A corresponding time period for switching current to a selected corresponding series of light-emitting diodes is substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

An LED-based lighting device and method for making the same are disclosed. The lighting device includes an LED light source mounted on a heat sink, a power adaptor, and a controller. The power adaptor is configured to be interchangeable with a conventional incandescent bulb power adapter. The controller provides an average current to the LED light source when power is coupled to the device via the power adaptor. The average current causes the LED light source to generate light of a predetermined standard intensity that is substantially independent of variations in the LED light source from device to device. In one aspect of the invention, the LED light source includes a plurality of LEDs connected in series, the LEDs are bonded to the heat sink and connected to one another in series by wire bonds and to conducting traces on the heat sink.

In a method and apparatus for controlling power factor correction in mixed operation modes, a frequency of the input voltage is obtained by detecting the zero crossing points of the input voltage. A peak of the input voltage is obtained by detecting input voltage with 90 degree phase. Thus, the present invention predicts the input voltage by its frequency and peak and the characteristic of the sine wave. A digital signal processor computes the duty and frequency of a boost switch, switching the operation mode of the boost converter among continuous mode, critical mode and discontinuous mode according to input voltage or the load. According to another aspect, the operation is switched to critical mode from the average current mode when a zero current is detected before the charging and recharging cycle of the boost switch is finished. Overcurrent protection may be achieved by controlling current in response to detected voltage to provide a substantially constant power level. The overcurrent protection may be adaptive in nature.

A method of determining the impedance, inductance, and resistance of the network connecting an electrical power supply to an electric arc welding station including an electrode and a workpiece, wherein the method-comprises: shorting the electrode to the workpiece; creating at least one waveform including a first state operating the power supply at constant current of a selected value and a second state operating the power supply at a low value of current or open circuit voltage whereby the current decays from the selected value along a decay path indicative of di / dt; obtaining the average current Iavg and average resistance Ravg during the first state; selecting a portion of the decay path; sampling the instantaneous current for a number of times on the path during the second state to read the rate of the decay; and, using the average current and the average resistance with the rate of decay to obtain the inductance of the network.

A power-mode controlled power converter is capable of supplying a constant output voltage and output current. A PWM controller generates a PWM signal in response to a voltage sampled from a transformer auxiliary winding. A programmable current-sink and a detection resistor compensate for a voltage drop of an output rectifier. A low-pass filter integrates a switching-current voltage to an average-current signal. An attenuator produces an input-voltage signal from a line-voltage input signal. The PWM controller multiplies the average-current signal with the input-voltage signal to generate a power-control signal. An error-amplifier compares the power-control signal with a power-reference voltage to generate a limit voltage. The limit voltage controls the power delivered from a primary-side circuit to a secondary-side circuit of the power-mode controlled power converter. Since the power-reference voltage varies in proportional to output voltage variations, a constant output current is therefore achieved.

The invention discloses a PFC circuit which is provided with an average current control module, comprising a first boosting circuit, a second boosting circuit and the average current control module. The average current control module comprises a sampling unit, a difference value operating unit, a proportion integral unit and a duty ratio regulating unit which are connected one by one. The duty ratio regulating unit realizes the average current of the inductance current mean in a switch cycle. The invention also discloses an average current control method used for the PFC circuit, and the method comprises the following steps: A. a reference current is produced; B. the current is sampled and the difference value is operated to obtain the inductance current difference value of two parallel branches; C. control signal one of the first boosting circuit is produced through operation; D. control signal two of the second boosting circuit is produced through operation; E. the duty ratio of the two branches is obtained by regulating the duty ratio.

A method and apparatus for automatically detecting an occlusion or drive system failure in a medication infusion system is provided. The electrical current to an infusion pump is measured and compared against a baseline average current. If the current exceeds a threshold amount, an alarm is triggered. Alternatively, pump motor encoder pulses are measured during a pump cycle. If the number of pulses do not correspond within a normal range, an alarm is triggered. After any alarm is triggered, the pump motor is driven in reverse for an incremental distance in order to relieve the fluid pressure in the system.

Electronic circuits and methods include provisions for passing a first current through a diode during a first time interval and for passing a second different current through the diode during a second different time interval. The first current is selected to achieve a predetermined voltage at a node of the diode. A duty cycle of the first current relative to the second current is selected to achieve a predetermined average current passing through the diode. In some arrangements, the diode is a light emitting diode.

The invention discloses an LED driving control circuit and a method. The LED driving control circuit comprises a voltage comparison module, an output current threshold control module and an LED driving module, wherein the voltage comparison module is used for generating a comparison signal PWM (Pulse-Width Modulation) and providing the comparison signal PWM to the output current threshold control module and the LED driving module; the output current threshold control module is used for generating current threshold control signal IREF / VREF (Input Reference / Voltage Reference) to the LED driving module according to the duty factor of the comparison signal PWM; and the LED driving module is used for generating an LED driving control signal according to the input current threshold control signal IREF / VREF and the comparison signal PWM. The product of the duty factor of the current threshold control signal IREF / VREF and the duty factor of the comparison signal PWM is a constant so that average current output by the LED driving control circuit is equal under the comparison signal PWM of different duty factors. According to the invention, the influence of the overlarge current change of an LED lamp when a commercial power is changed can be solved; output current can be set conveniently; and the flickering problem of the LED lamp resulted from the current change is solved.

An electrochemical device converts carbon dioxide to a formic acid reaction product. The device includes an anode and a cathode, each comprising a quantity of catalyst. The anode and cathode each have reactant introduced thereto. Two membranes, a cation exchange polymer electrolyte membrane and an anion exchange polymer electrolyte membrane, are interposed between the anode and the cathode, forming a central flow compartment where a carbon dioxide reduction product, such as formic acid, can be recovered. At least a portion of the cathode catalyst is directly exposed to gaseous carbon dioxide during electrolysis. The average current density at the membrane is at least 20 mA / cm2, measured as the area of the cathode gas diffusion layer that is covered by catalyst, and formate ion selectivity is at least 50% at a cell potential difference of 3.0 V. In some embodiments, at least one polymer electrolyte membrane comprises a polymer in which a constituent monomer is (p-vinylbenzyl)-R, where R is selected from the group consisting of imidazoliums, pyridiniums and phosphoniums. In some embodiments, the polymer electrolyte membrane is a Helper Membrane comprising a polymer containing an imidazolium ligand, a pyridinium ligand, or a phosphonium ligand.

A driving circuit for powering a plurality of light-emitting diode (LED) light sources includes a power converter and a plurality of current balance controllers. The power converter receives an input voltage and provides a regulated voltage to the LED light sources. The current balance controllers coupled to the power converter control a plurality of currents through the LED light sources respectively. The current balance controllers receive a first reference signal indicative of a target average level and a second reference signal indicative of a maximum transient level, and regulate an average current of each of the currents to the target average level and a transient level of each of the currents within the maximum transient level.

A simple method and device for accurately measuring flash memory cell current. The sensing scheme comprises an integrator, an analog to digital converter, and a digital to analog converter. The method comprises the acts of applying an input current and a feedback output current to a summer, integrating the resulting summer output over time, passing the integrated output to a clocked comparator, outputting a comparator output which controls a feedback circuit that keeps the integrator's voltage at the same level as a reference voltage, and outputting a digital average current to a counter. Delta sigma modulation (averaging) is employed to cancel out noise that would otherwise affect the cell current measurement.

A system and method for providing a constant current source driver for a light emitting diode string. The converter includes a current sensor that derives feedback signal corresponding to a peak current through the light emitting diode string. The feedback signal is used by a controller to vary a duty cycle of the controller to regulate the average current. The controller is operable to regulate the average current as the number of light emitting diodes is increased and / or decreased.

A method of driving a light source, a light source apparatus for performing the method, and a display apparatus having the light source apparatus are disclosed in accordance with one or more embodiments. In the method, a plurality of light source strings connected in parallel is driven by applying a driving voltage to a first terminal of the light source strings. A peak current due to a voltage deviation of each of the light source strings is switch-controlled to uniform an average current of the light source strings. Thus, a peak current flowing through light source strings in accordance with a voltage deviation of the light source strings is switch-controlled, so that an average current of the light source strings may be uniformly maintained. Therefore, a voltage deviation is not consumed as power, so that damage to circuit elements due to heat may be prevented.

A dimmable, light-emitting diode (LED) power supply adapted to provide a direct current (DC), constant current (“constant current source”) from a conventional, phase-controlled 120 VAC, 60 Hz power source is disclosed. The constant current source of the present invention utilizes two processes to control dimming. In a first process, the phase angle of the input voltage is used to control the duty cycle of a line frequency pulse width modulation (PWM). In a second process, a proportional-current limit adjustment is used to control the average current to the LED during the ON time of the line frequency by PWM. As a result, at relatively low phase angles, peak currents can be lowered, reducing flicker and improving the audible noise levels generated by the circuit.

The present invention provides a method and apparatus for scaling the average drive current supplied to a light-emitting element or string thereof by coupling a scaling signal to an original control signal thereby generating an effective control signal for control of the light-emitting element(s). The scaling signal can be a modulated signal, for example a Pulse Width Modulation (PWM) signal, Pulse Code Modulation (PCM) signal, or other signal and modifies the original control signal to produce an effective control signal. The effective control signal is subsequently used to control the supply of power to the light-emitting element(s) from a power source via a switching device. The effective control signal essentially modifies the ON time of the light-emitting element(s), thereby modifying the average drive current passing through the light-emitting element(s). The scaling signal is coupled to the original control signal by a coupling mechanism, thereby enabling the modification of the original control signal by the scaling signal forming the effective control signal.