Systems and methods of input power and current measurement

Patent metadata

Field	Value
Publication number	US-9523756-B2
Application number	US-201313915777-A
Country	US
Kind code	B2
Filing date	Jun 12, 2013
Priority date	Aug 20, 2012
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

As disclosed herein, a PFC control device, may be used for power factor correction and for input power and current measurement simultaneously. To determine the input power, input voltage and input current are determined. These measurements may be performed using a current sensor and a voltage sensor, for example. In an example embodiment of the systems and methods of input power and current measurement disclosed herein, the current is measured after an electromagnetic interference (EMI) filter. The input voltage and input current should be sampled substantially simultaneously. The measured input current is adjusted due to a phase shift introduced in the current sense circuit. The input voltage and input current should be sampled substantially simultaneously. The input power is determined using the PFC input voltage and the adjusted input current. The total input current is determined using the PFC input current and the EMI filter reactive current.

First claim

The invention claimed is:

1. A method of determining input power and current comprising:
providing a power factor correction (PFC) control device having a plurality of analog to digital converter (ADC) inputs and a pulse width modulation (PWM) output controlling an output voltage of the PFC circuit;
determining power factor correction (PFC) input current utilizing at least one of the ADC inputs of a PFC control device;
determining PFC input voltage utilizing at least one of the ADC inputs of the PFC control device;
correlating the PFC input voltage and the PFC input current such that the PFC input voltage and the PFC input current are sampled substantially simultaneously;
adjusting the determined PFC input current value to compensate for a phase shift in a current sense circuit to determine an adjusted input current;
determining the input power using the correlated PFC input voltage and the adjusted input current; and
adjusting the determined input current to compensate for reactive current in an electromagnetic interference (EMI) filter to determine a total input current, wherein the total input current is substantially equal to a square root of a sum of a square of an EMI reactive current and a square of the determined input current, the EMI reactive current substantially equal to the input voltage divided by 1/(2πfC), where C is an EMI capacitance value and f is the frequency of the input current.

2. The method of claim 1 , further comprising calibrating the determined input current for gain and offset in operational amplifiers in a current measurement circuit.

3. The method of claim 2 , wherein the calibrating is performed using at most two calibration points.

4. The method of claim 1 , wherein the correlating of the PFC input voltage and PFC input current comprises using a dual sample and hold circuit to sample the PFC input voltage and PFC input current substantially simultaneously.

5. The method of claim 1 , wherein compensating for a phase shift in the current sense circuit comprises determining a delay of the current sense signal through the current sense circuit.

6. The method of claim 1 , wherein the calculating of the input power comprises calculating

P
=

∑

(

k
v

⁢

C
v

⁡

(
n
)

-

m
v

)

⁢

(

k
i

⁢

C
i

⁡

(
n
)

-

m
i

)

N

,

where k v is a voltage sense gain, C v is a voltage ADC conversion output (in counts), m v is a voltage sense offset, k i is a current sense gain, C i is a current ADC conversion output (in counts), and m i is current sense offset and wherein n is an integer representing the nth sample and N is the total number of samples in an AC cycle.

7. A system of input power and current measurement, comprising:
a power factor correction (PFC) control device comprising:
a plurality of analog to digital converter (ADC) inputs and a pulse width modulation (PWM) output, a first at least one of the plurality of ADC inputs configured for sensing an input voltage, a second at least one of the plurality of ADC inputs configured for sensing an input current, the PWM output configured to control an output voltage of a PFC circuit;
an input voltage signal conditioning circuit configured to receive an input voltage and adjust the input voltage range to fit within the measurement range of the first of the plurality of ADC inputs; and
a current sense signal conditioning circuit configured to sense an input current of the PFC control circuit and adjust a signal representing the sensed input current to fit within a measurement range of the second at least one of the plurality of ADC inputs,
the PFC control device configured to determine an input current and adjust the determined input current to compensate for reactive current in an electromagnetic filter to determine a total input current and to compensate for a phase shift introduced by the current sense conditioning circuit, wherein the PFC control device determines the total input current as substantially equal to a square root of a sum of a square of an EMI reactive current and a square of the determined input current, the EMI reactive current substantially equal to the input voltage divided by 1/(2πfC), where C is an EMI capacitance value and f is the frequency of the input current.

8. The system of claim 7 , wherein the PFC control device calibrates the determined input current for gain and offset errors in operational amplifiers in the current sense signal conditioning module.

9. The system of claim 8 , wherein the PFC control device calibrates using at most two calibration points.

10. The system of claim 7 , wherein the PFC control circuit is further configured to correlate the input voltage and the input current such that the input voltage and the input current are sampled substantially simultaneously.

11. The system of claim 10 , wherein the correlating of the input voltage and input current comprises using a dual sample and hold circuit to sample the input voltage and input current substantially simultaneously.

12. A system of input power and current measurement, comprising:
a power factor correction (PFC) control device comprising:
a plurality of analog to digital converter (ADC) inputs and a pulse width modulation (PWM) output, a first at least one of the plurality of ADC inputs configured for sensing an input voltage, a second at least one of the plurality of ADC inputs configured for sensing an input current, the PWM output configured to control an output voltage of a PFC circuit;
an input voltage signal conditioning module circuit configured to receive an input voltage and adjust the input vo

Assignees

• Texas Instruments Inc

Inventors

• Sun Bosheng

Classifications

• G01R21/133

  by using digital technique · CPC title

• G01R35/04 Primary

  of instruments for measuring time integral of power or current · CPC title

• G01R35/005 Primary

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title