Abstract: Safe detection of an external load attached to an AC power outlet of a power supply stands out as one advantage of the power supply apparatus and method contemplated herein, although other advantages flow therefrom. Not least among the other advantages are a simplicity of design offering an economical and robust mechanism for detecting external loads. The contemplated mechanism relies on the application of a DC voltage to one electrical phase of the AC power outlet and the coupling of that voltage to the other electrical phase of the AC power outlet through an interconnecting resistor. With both phases respectively coupled to voltage divider circuits nominally matched in value, the divided down voltages measured from the respective phases will differ in dependence on the relative size of the interconnecting resistor and the resistive value of any load attached to the AC power outlet.

Abstract: In one aspect of the teachings herein, a switching circuit for switching a power transistor is configured to control the slew rate of the switched load current in a manner that yields substantial independence from the load voltage, based on the use of a Miller-effect compensation capacitor and controllable source resistances for driving the gate or base of the power transistor. In a non-limiting example, a control circuit, such as a microcontroller, uses a set of bidirectional input/output ports to drive the transistor base or gate through a selectable combination of parallel resistors, so that the effective source resistance for transistor turn-on and turn-off is selectable by configuring different combinations of input/output settings for the set of bidirectional input/output ports. Controlling the source resistance in this manner allows the control circuit to set or otherwise control the slew rate of the load current.

Abstract: In one aspect of the teachings herein, an interface circuit obviates the need for a microcontroller with multi-channel PWM capability in the context of controlling a brushless, three-phase DC motor. Instead, the interface circuit generates the requisite set of motor-phase control signals using a single PWM channel from the microcontroller. The interface circuit is implemented as a standalone integrated circuit (IC) in one embodiment, and is integrated into a pre-driver circuit in another embodiment.

Abstract: In one aspect of the teachings herein, a switching circuit for switching a power transistor is configured to control the slew rate of the switched load current in a manner that yields substantial independence from the load voltage, based on the use of a Miller-effect compensation capacitor and controllable source resistances for driving the gate or base of the power transistor. In a non-limiting example, a control circuit, such as a microcontroller, uses a set of bidirectional input/output ports to drive the transistor base or gate through a selectable combination of parallel resistors, so that the effective source resistance for transistor turn-on and turn-off is selectable by configuring different combinations of input/output settings for the set of bidirectional input/output ports. Controlling the source resistance in this manner allows the control circuit to set or otherwise control the slew rate of the load current.

Abstract: In one aspect of the teachings herein, an interface circuit obviates the need for a microcontroller with multi-channel PWM capability in the context of controlling a brushless, three-phase DC motor. Instead, the interface circuit generates the requisite set of motor-phase control signals using a single PWM channel from the microcontroller. The interface circuit is implemented as a standalone integrated circuit (IC) in one embodiment, and is integrated into a pre-driver circuit in another embodiment.

Abstract: A new and improved method for measuring the value of a capacitor and for detecting small variations in the value of a capacitor around a reference value is described. In accordance with the invention, the capacitance of capacitor may be determined by applying a voltage input having a known amplitude and wave form V to an RC circuit having a substantially known or constant load impedance R and sampling the voltage across the resistor or capacitor at a precisely controlled elapsed time interval T. The method now permits improved detector circuits to be created for measuring small variations in value with precision and accuracy. Solid state keypads incorporating sensor cells and software algorithms provide superior human to machine interface systems which are not subject to environmentally induced errors or errors due to component aging.

Abstract: A new and improved method for measuring the value of a capacitor and for detecting small variations in the value of a capacitor around a reference value is described. In accordance with the invention, the capacitance of capacitor may be determined by applying a voltage input having a known amplitude and wave form V to an RC circuit having a substantially known or constant load impedance R and sampling the voltage across the resistor or capacitor at a precisely controlled elapsed time interval T. The method now permits improved detector circuits to be created for measuring small variations in value with precision and accuracy. Solid state keypads incorporating sensor cells and software algorithms provide superior human to machine interface systems which are not subject to environmentally induced errors or errors due to component aging.