An apparatus and method for converting a capacitance measured on a sensor element to a digital code. The apparatus may include a switching capacitor as a sensor element of a sensing device, and a sigma-delta modulator coupled to the sensor element to convert a capacitance measured on the sensor element to a digital code. The switching capacitor is in a feedback loop of the sigma-delta modulator. The method may include measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, and converting the capacitance measured on the sensor element to a digital code.

Capacitance to code converter with sigma-delta modulator

A high-performance contactless electrical energy transmission (CEET) technique which employs the inductive energy transmission principle is described. The proposed technique enables the implementation of high-efficiency, high-power-density, fully-regulated CEET systems suitable for applications with a wide input range and a wide load range. The CEET system in this invention consists of an input-side variable-frequency inverter and an output-side regulated rectifier. A high efficiency of the system is achieved by recovering the energy stored in the leakage inductances of the transformer by incorporating them in the operation of the circuit, and by employing high-frequency-inverter and controlled-rectifier topologies that allow a controlled bi-directional power flow through the transformer. A feed forward, variable-switching-frequency control of the inverter is used to maintain a substantially constant power transfer through the transformer when the input voltage changes. A local PWM control is used for the output-side rectifier to achieve a tight regulation of the output in the presence of load variations.

Contactless electrical energy transmission system

A power system having a power converter with an adaptive controller. The power system is coupled to a load and includes a power system controller that receives a signal indicating a system operational state of the load and selects a power converter operational state as a function thereof. The power system also includes a power converter with a power switch that conducts for a duty cycle to provide a regulated output characteristic at an output thereof. The power converter also includes a controller that receives a command from the power system controller to enter the power converter operational state and provides a signal to control the duty cycle of the power switch as a function of the output characteristic and in accordance with the command, thereby regulating an internal operating characteristic of the power converter to improve an operating efficiency thereof as a function of the system operational state.

Power system with power converters having an adaptive controller

A power converter nearly losslessly delivers energy and recovers energy from capacitors associated with controlled rectifiers in a secondary winding circuit, each controlled rectifier having a parallel uncontrolled rectifier. First and second primary switches in series with first and second primary windings, respectively, are turned on for a fixed duty cycle, each for approximately one half of the switching cycle. Switched transition times are short relative to the on-state and off-state times of the controlled rectifiers. The control inputs to the controlled rectifiers are cross-coupled from opposite secondary transformer windings.

High efficiency power converter

A method for locating a conductive object at a touch-sensing surface may include detecting a first resolved location for the conductive object at the touch-sensing surface based on a first scan of the touch-sensing surface, predicting a location for the conductive object, and determining a second resolved location for the conductive object by performing a second scan of a subset of sensor elements of the touch-sensing surface, wherein the subset of sensor elements is selected based on the predicted location of the conductive object.

Predictive touch surface scanning

A system and method for determining an output current of a power converter having an output capacitor and a component coupled thereto. In one embodiment, the system includes (1) an observer circuit, parallel-coupled to the output capacitor, that senses a voltage across the output capacitor and develops therefrom a capacitor signal representing a current through the output capacitor, (2) a sensor circuit, coupled to the component, that senses a characteristic of the component and develops therefrom a component signal representing a current through the component and (3) a summer circuit, coupled to the observer and sensor circuits, that derives an output signal representing the output current from the capacitor signal and the component signal.

System and method for determining output current and converter employing the same

For use with a synchronous rectifier coupled to a secondary winding of a transformer and having a rectifier switch, a circuit for, and method of driving the rectifier switch and a power converter employing the circuit or the method. In one aspect of the present invention wherein the synchronous rectifier has at least first and second rectifier switches, the circuit includes: (1) a series-coupled drive winding and capacitor, coupled between a first control terminal of the first rectifier switch and a second control terminal of the second rectifier switch, that generates first and second drive signals and delivers the first and second drive signals to the first and second control terminals, respectively, and (2) first and second clamps, coupled to the first and second control terminals, respectively, that control first and second capacitive charges within the first and second rectifier switches to limit voltage excursions of the first and second drive signals.

Drive compensation circuit for synchronous rectifier and method of operating the same

A new controller-filter structure for a switch-mode power converter is described. The controller produces a minimum-time control signal for step changes in output voltage or in load current by partitioning the state-vector plane for the converter's output filter with a simple curve. A companion filter estimates the state vector of the power converter by modeling the response of the power converter to the control signal. The controller, abandoning the traditional approach of producing duty cycle using a sawtooth waveform with an adjustable threshold, avoids the performance limitations ordinarily encountered with a linear feedback approach.

Optimal Feedback Control of Switch-Mode Power Converters

A power factor correction system with an EMI line filter at the input includes circuitry to sense the capacitor current of the EMI filter to improve the accuracy of the power factor enhancement. The circuitry consists of a current sensing means connected after the EMI filter, and a voltage sensing capacitor which derives its input signal from a pair of diodes separate from the conventional 4-diode rectifier bridge, which are connected either before or after the EMI filter. The current-sensing means, which may be a resistor, and the voltage-sensing capacitor are tightly coupled to the current control loop of the power factor correction system to compensate for the current in the EMI filter capacitors.

Power factor control for switched mode rectifiers with improved representing of currents in EMI capacitive elements

A power factor correction system with an EMI input filter includes circuitry to sense the capacitor current of the filter to improve the accuracy of the power factor enhancement by providing a split current sensing resistor connected to the EMI filter or a voltage sensing capacitor. Both arrangements may be tightly coupled to the current control loop of the power factor control and compensate for the unsensed current in the EMI filter capacitors.

Mark E. Jacobs

Papers

System and method for determining output current and converter employing the same

Drive compensation circuit for synchronous rectifier and method of operating the same

Optimal Feedback Control of Switch-Mode Power Converters

Power factor control for switched mode rectifiers with improved representing of currents in EMI capacitive elements

Power factor control for switched mode rectifiers