2335 results about "Current threshold" patented technology

Apparatus and method for stimulating neuromuscular tissue in the stomach. The neuromuscular stimulator stimulates the neuromuscular tissue by applying current-controlled electrical pulses. A voltage sensor detects the voltage across the neuromuscular tissue to determine if the voltage meets a predetermined voltage threshold. A control circuit adjusts the current-controlled pulse if the voltage is found to meet the voltage threshold, such that the voltage does not exceed the voltage threshold. A voltage-controlled pulse may also be applied to the tissue. A current sensor would then detect whether the current on the neuromuscular tissue meets a predetermined current threshold, and a control circuit adjusts the voltage controlled pulse such that the current does not exceed the current threshold. A real time clock may be provided which supplies data corresponding to the time of day during the treatment period. A programmable calendar stores parameters of the stimulating pulse, wherein the parameters have a reference to the time of day.

A power supply including a regulation circuit that maintains an approximately constant load current with line voltage. An example circuit includes a switch including first, second and third terminals. The first terminal is coupled or decoupled to the second terminal in response to a control signal received at the third terminal. Voltage sense circuitry is included and is coupled to sense a voltage drop across the switch. The voltage drop is representative of a current in the switch during an on time of the switch. The voltage sense circuitry has a variable current limit threshold that increases between a first level and a second level during the on time of the switch. The control signal is responsive to the variable current limit threshold to regulate a power supply with an output characteristic having an approximately constant output voltage below an output current threshold and an approximately constant output current below an output voltage threshold.

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.

An over-power protection apparatus with programmable over-current threshold for a power converter is provided. The over-power protection apparatus further provides an over-temperature threshold for protection purposes. The over-power protection apparatus is able to achieve over-power and over-temperature protection in response to the level of the driving signal of the power converter. In addition, the programmable over-current threshold of the present invention can be adjusted in response to various load conditions.

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.

A method for programming and erasing a memory array includes the step of adapting programming or erase pulses to the current state of the memory array. In one embodiment, the step of adapting includes the steps of determining the voltage level of the programming pulse used to program a fast bit of the memory array and setting an initial programming level of the memory array to a level in the general vicinity of the programming level of the fast bit. For erasure, the method includes the steps of determining erase conditions of the erase pulse used to erase a slowly erasing bit of said memory array and setting initial erase conditions of said memory array to the general vicinity of said erase conditions of said slowly erasing bit. In another embodiment of the array, the step of adapting includes the steps of measuring the current threshold level of a bit to within a given range and selecting an incremental voltage level of a next programming or erase pulse for the bit in accordance with the measured current threshold level.

A magnetic memory element capable of maintaining high thermal stability (retention characteristics) while reducing a writing current. The magnetic memory element includes a magnetic tunnel junction having a first magnetic body including a perpendicular magnetization film, an insulating layer, and a second magnetic body serving as a storage layer including a perpendicular magnetization film, which are sequentially stacked. A thermal expansion layer is disposed in contact with the magnetic tunnel junction portion. The second magnetic body is deformed in a direction in which the cross section thereof increases or decreases by the thermal expansion or contraction of the thermal expansion layer due to the flow of a current, thereby reducing a switching current threshold value required to change the magnetization direction.

System controller and method for protecting a power converter. The system controller includes a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter. The power converter further includes a secondary winding coupled to the primary winding, and the drive signal is associated with one or more switching periods. Additionally, the system controller includes a second controller terminal configured to receive a sensing voltage from a sensing resistor. The sensing voltage represents a magnitude of the first current flowing through the primary winding of the power converter. The system controller is configured to process information associated with the sensing voltage and a reference voltage, and determine whether an average output current of the power converter is larger than a current threshold.

Apparatus and method for providing current limiting in a DC-DC converter and especially to methods and apparatus suitable for a start-up mode of operation. The invention monitors the inductor (L) current when the high side supply switch is on against a peak current limit threshold. If the inductor current reaches the peak current limit threshold the high side switch is turned off. The inductor current when the low side switch is off is monitored against a valley current threshold. As long as the inductor current is above the valley current threshold turn on of the low side switch is inhibited. In this way current limiting is provided and the problems of stair-stepping are avoided. Embodiments employing lossless current sensing are described. The invention may be implemented in a start-up mode of operation wherein the converter is controlled purely by the peak current limit and valley current threshold which are increased over time.

A lighting system has an array (100) of at least one light-emitting solid-state element such as a light-emitting diode (LED) or a laser diode. A voltage source (10), which may supply either alternating or direct current, energizes the array. Array state circuitry (125; Q2, R2), electrically connected in series with the array (100), senses at least one state of the array, such as the amount of current passing through the array, or temperature. Secondary circuitry (127; R1, Q1; 200, 201, 202; 200, R4, Q1; 126, 127) is connected in parallel with the array (100). A switching component (Q1; Q1, Q3; 202) adjusts the current passing through the secondary circuitry in accordance with the sensed state of the array such that current through the array is maintained substantially constant. A third, parallel, excess current shunt path may also be provided, in which case so is excess current shunt circuitry, which senses current flowing in the secondary circuitry and shunts current in the secondary circuitry in excess of an excess current threshold to the excess current shunt path, whereby overflow current above a first threshold for the array (100) is shunted away from the array and excess current above a second threshold is shunted from the secondary circuits to the excess current shunt circuitry. A wide-angle mounting arrangement is also provided for the array.

A method and system for reducing thermal load by monitoring and controlling current flow in a portable computing device (“PCD”) are disclosed. The method includes monitoring a temperature of the PCD and determining if the temperature has reached a temperature threshold condition. This temperature threshold condition may be comprised within any one or more of a plurality of thermal policy states, in which each thermal policy state may dictate various thermal mitigation techniques. The thermal policy states may be associated with values that may indicate thermal loading of a PCD. If the temperature has reached the first threshold condition, then electrical current exiting a power supply device may be monitored. If it is determined that the electrical current has exceeded a current threshold condition, such as a maximum current, a hardware device corresponding to the electrical current may be selected for application of a thermal mitigation technique.

The invention discloses a soft starting circuit for a pulse width modulation DC-DC switch power, comprising a frequency splitting count module, a current threshold module, a current sampling module, a current limiting comparator, a two input or-gate, an oscillator and an RS trigger. The current in a power inductance is sampled when an external switch rectifier is conducted, and the current changes from small to big by stage by limiting the peak value of the current so as to control the step change of the duty ratio, thus leading the output voltage to increase by stage gradually, avoiding surge current in starting procedure and realizing the soft starting function. The invention has the advantages of integrating to the inside of large scale integrated circuit without high capacitance in the outside or a microcontroller to control, limiting the load current directly with good soft starting effect and being suitable for a voltage control mode and a current control mode; the circuit is simple correspondingly by adopting a current gating network; the soft starting time can be regulated automatically according to different loads.

A battery protection circuit is provided that includes a safety circuit and a charge monitoring circuit. The safety circuit monitors the voltage and current of at least one rechargeable cell within the battery pack, and disconnects the cell(s) from the external terminals of the battery pack when either the voltage becomes too high or low, or when excessive current is being drawn from the battery pack. The charge monitoring circuit can include any of a number of detectors or monitoring circuits, including those that monitor temperature, pressure, voltage, energy, current or power. In one embodiment, the charge monitoring circuit includes a power meter and a pulsed current detector. The charge monitoring circuit actuates when either the power or pulsed current exceeds a predetermined power or current threshold, respectively. When the charge monitoring circuit actuates, an overcurrent condition is simulated in the safety circuit. The overcurrent condition causes a disconnect switch to open, thereby disconnecting the cell(s) from the external terminals. The battery protection circuit then latches in this disconnected state until a load is removed from the terminals of the battery pack.

A converter constituted of: an inductor; a plurality of electronically controlled switches; and a control circuitry arranged to operate in a buck-boost mode responsive to the output voltage of the converter being within a predetermined range of the input voltage of the converter, the control circuitry arranged in the buck-boost mode: responsive to a current flowing through the inductor being lower than a predetermined low current threshold, to control the switches to couple the inductor between the input voltage and a common potential; responsive to the current flowing through the inductor being greater than a predetermined medium current threshold, to control the switches to couple the inductor between the input voltage and the output voltage; and responsive to the current flowing through the inductor being greater than a predetermined high current threshold, to control the switches to couple the inductor between the output voltage and the common potential.

The invention provides a motor overheat protection method and device. The method comprises the following steps of: detecting the working current of a motor in real time; comparing the working current with the preset current threshold; timing the time of the working current greater than the current threshold when the working current is greater than the current threshold; comparing the timed time value with the preset time value; and stopping running the motor when the timed time value meets the preset time value. The motor overheat protection method and device provided by the invention can rapidly determine the overheat of the motor when the time of the current of the motor greater than the time of the current threshold meets the preset time value, and can perform the overheat protection for the motor and stop running the motor, and the performances and the service life of the motor can be prevented from being influenced by overheat.

The invention discloses a power factor correction control circuit for reducing EMI (electro magnetic interference), which comprises an inductive current threshold value, wherein when an inductive current is less than the inductive current threshold value, a peak value of the inductive current is controlled to be changed along with an input voltage; and when the inductive current reaches the inductive current threshold value, the inductive current is limited to be the inductive current threshold value. In such a way, the maximum peak of the inductive current is reduced, so that an inductive ripple current is reduced; the power factor is ensured, and the EMI of the circuit is reduced simultaneously, so that circuit filtering can be carried out simply and easily; and the power factor correction control circuit is extremely suitable for occasions with middle or low power. In addition, the peak current stress of the circuit is low, so that a switch tube and other components have small loss, and the utilization ratio of a power supply is further improved. The power factor correction control circuit for reducing the EMI disclosed by the invention meets the requirements of high-power factor and IEC61000-3-2 on the harmonic of the power supply, and has low cost and a small size.