A current transformer (CT) for the purpose of, for example, current measurement, that uses a power line as a first coil and a second coil for measurement purposes, is further equipped with a third coil. Circuitry connected to the third coil is adapted to inject a known reference signal to the third coil of the CT. The injected reference signal, i.e., current, generates signals in the first and second coils of the CT. The signal generated in the second coil is compared using circuitry attached thereto to the reference signal. Based on the results, and the difference between the expected results and the actual results, updated calibration parameters are determined. These provide improved accuracy when using the CT, for example for measurement of the like of current or phase of the primary coil when measurements are adjusted using the newly determined calibration parameters.

A current transformer (CT) for the purpose of, for example, current measurement, that uses a power line as a first coil and a second coil for measurement purposes, is further equipped with a third coil. Circuitry connected to the third coil is adapted to inject a known reference signal to the third coil of the CT. The injected reference signal, i.e., current, generates signals in the first and second coils of the CT. The signal generated in the second coil is compared using circuitry attached thereto to the reference signal. Based on the results, and the difference between the expected results and the actual results, updated calibration parameters are determined. These provide improved accuracy when using the CT, for example for measurement of the like of current or phase of the primary coil when measurements are adjusted using the newly determined calibration parameters.

A power conversion device includes: a plurality of legs, each leg including a high-side switch connected between a voltage supply node and a phase node and a low-side switch connected between the phase node and a reference node; a phase current sensor for each leg and configured to sense current flowing through the high-side switch or the low-side switch of the corresponding leg; a single current sensor connected between the reference node and the low-side switches, or between the voltage supply node and the high-side switches; and a controller. During a subperiod of a switching period, the controller is configured to sample the current sensed by at least one of the phase current sensors and a current sensed by the single current sensor such that the current in one or more of the legs is sampled during the same subperiod as the current flowing through the single current sensor.

A power conversion device includes: a plurality of legs, each leg including a high-side switch connected between a voltage supply node and a phase node and a low-side switch connected between the phase node and a reference node; a phase current sensor for each leg and configured to sense current flowing through the high-side switch or the low-side switch of the corresponding leg; a single current sensor connected between the reference node and the low-side switches, or between the voltage supply node and the high-side switches; and a controller. During a subperiod of a switching period, the controller is configured to sample the current sensed by at least one of the phase current sensors and a current sensed by the single current sensor such that the current in one or more of the legs is sampled during the same subperiod as the current flowing through the single current sensor.

An abnormality detection method according to one aspect of the present disclosure is a method of detecting an abnormality in an AC signal to be input from an AC power supply. The method includes, where an ideal AC signal is represented as V.sub.0 sin ωt (V.sub.0: amplitude, co: angular frequency, t: time), calculating an arithmetic value including a value represented by sin.sup.2ωt+cos.sup.2ωt and determining that the AC signal is abnormal when the arithmetic value is out of a threshold range.

Techniques described herein address these and other issues by utilizing two or more sensors to take temperature measurements from which a temperature-differential or instantaneous temperature rate-of-change, can be determined. In turn, this can be used to make a highly accurate model of the relationship between the temperature, temperature-differential, and clock circuitry frequency, to accurately estimate the frequency rate-of-change for frequency correction/compensation.

A control circuit for a power factor correction (PFC) circuit, the control circuit includes a multiplier having first, second, and third multiplier inputs and a multiplier output. The control circuit has an adder having first and second inputs and an output. The first input of the adder is coupled to the multiplier output. The control circuit further includes a root mean square (RMS) calculation circuit configured to determine a square of a root mean square of an input sinusoidal voltage. The RMS calculation circuit has an output coupled to the second multiplier input. An input voltage square calculation circuit is configured to determine a square of the input sinusoidal voltage. The input voltage square calculation circuit has an output coupled to the third multiplier input.

A method for determining rectifier-stage output current and/or grid-side currents (iu, iv, iw) of a frequency converter (1) having a passive rectifier (3), an inverter (4), a DC-link with a DC-link inductor (Ldc) and a DC-link capacitor (Cdc) between the rectification stage (3) and the inverter stage (4) is described. In a frequency converter the current information for the grid-side currents (iu, iv, iw) should be obtained without a current sensor at the grid-side (2). To this end the method comprises the step of calculating a current in the DC-link (5) by using at least a voltage value (Urec) and characteristics of the rectifier (3) in the DC-link (5) and/or grid side currents to form a corrected current using the calculated current and a measured current or currents or a fraction of a measured current or currents, or a fraction of a measured current or currents.

In an example method of trimming a voltage reference circuit, the method includes: setting the circuit to a first temperature; trimming a first resistor (R.sub.DEGEN) of a differential amplifier stage of the circuit; and trimming a first resistor (R1) of a scaling amplifier stage of the circuit. The trimming equalizes current flow through the differential amplifier stage and the scaling amplifier stage. The method includes: trimming a second resistor (R2) of the scaling amplifier stage to set an output voltage of the circuit to a target voltage at the first temperature; setting the circuit to a second temperature; and trimming a second resistor (R.sub.PTAT) of the differential amplifier stage, a third resistor (R1.sub.PTAT) of the scaling amplifier stage, and a fourth resistor (R2.sub.PTAT) of the scaling amplifier stage to set the output voltage of the circuit to the target voltage at the second temperature.

In an example method of trimming a voltage reference circuit, the method includes: setting the circuit to a first temperature; trimming a first resistor (R.sub.DEGEN) of a differential amplifier stage of the circuit; and trimming a first resistor (R1) of a scaling amplifier stage of the circuit. The trimming equalizes current flow through the differential amplifier stage and the scaling amplifier stage. The method includes: trimming a second resistor (R2) of the scaling amplifier stage to set an output voltage of the circuit to a target voltage at the first temperature; setting the circuit to a second temperature; and trimming a second resistor (R.sub.PTAT) of the differential amplifier stage, a third resistor (R1.sub.PTAT) of the scaling amplifier stage, and a fourth resistor (R2.sub.PTAT) of the scaling amplifier stage to set the output voltage of the circuit to the target voltage at the second temperature.