CN107276385A

CN107276385A - The effective value-acquiring method of alternating voltage and device of PFC power supplys

Info

Publication number: CN107276385A
Application number: CN201710483383.6A
Authority: CN
Inventors: 黄招彬
Original assignee: Guangdong Midea Refrigeration Equipment Co Ltd
Current assignee: GD Midea Air Conditioning Equipment Co Ltd
Priority date: 2017-06-21
Filing date: 2017-06-21
Publication date: 2017-10-20
Anticipated expiration: 2037-06-21
Also published as: CN107276385B

Abstract

The present invention discloses the effective value-acquiring method of alternating voltage and device of a kind of PFC power supplys, wherein, the effective value-acquiring method of alternating voltage of PFC power supplys comprises the following steps：Obtain the current operating parameters of PFC power supplys；During the condition that the circuit of power factor correction for meeting PFC power supplys in the current operating parameters of PFC power supplys is closed, the circuit of power factor correction of control PFC power supplys is closed, and the first input ac voltage peak value of PFC power supplys is obtained according to the voltage at electrochemical capacitor two ends；During the condition that the circuit of power factor correction for meeting PFC power supplys in the volume current operating parameters of PFC power supplys is opened, control circuit of power factor correction is opened, and the second input ac voltage peak value of PFC power supplys is obtained according to input ac voltage instantaneous value；According to the first input ac voltage peak value or the alternating voltage virtual value of the second input ac voltage peak computational PFC power supplys.Technical solution of the present invention has the characteristics of accuracy is high.

Description

Method and device for acquiring effective value of alternating voltage of PFC (power factor correction) power supply

Technical Field

The invention relates to the technical field of power electronics, in particular to a method and a device for acquiring an effective value of alternating voltage of a PFC power supply.

Background

In household appliances and the like: the single-phase alternating current power supply accessed from the power grid is rectified by an uncontrollable full bridge, then passes through a power factor correction circuit, finally outputs a direct current power supply, and supplies power to a load after passing through a large-capacity electrolytic capacitor. The power factor correction circuit generally adopts a BOOST architecture. The BOOST type power factor correction circuit can not only enable a PFC power supply to achieve a high power factor, but also BOOST and output a stable direct current bus voltage so as to provide a stable direct current power supply for a load.

There are various control methods for BOOST type power factor correction, such as voltage/current double closed loop control algorithm, single cycle control algorithm, etc. From the viewpoint of power factor correction, the alternating voltage is not needed to be used as an input quantity by adopting the single-period control algorithm, and the alternating voltage sampling circuit is eliminated, however, the alternating voltage is needed to be used as a protection threshold value or other control input parameters in most electric appliance systems, so that the estimation of the effective value of the alternating voltage is needed to be carried out on the basis of the elimination of the alternating voltage sampling circuit.

The prior art adopts the following method to obtain the effective value of the alternating voltage of the PFC power supply: and when the current is small, the voltage peak value is adopted to calculate the effective value, and when the current is large, the voltage instantaneous value is adopted to calculate the effective value. In any switching period of a power switching tube in the power factor correction circuit, the voltage instantaneous value is related to the inductance current change quantity, the inductance current rising time and the inductance current falling time.

Because the time of the current drop of the inductor cannot be known when the power factor correction circuit works in the inductor current interrupted mode, the prior art cannot avoid the problem that the estimated alternating voltage effective value is larger due to the estimation error of the alternating voltage of the power factor correction circuit in the current interrupted working state.

Disclosure of Invention

The invention mainly aims to provide a method for acquiring an effective value of alternating voltage of a PFC power supply, aiming at improving the accuracy of the acquired effective value of the alternating voltage of the PFC power supply.

In order to achieve the above object, the method for obtaining the effective value of the alternating voltage of the PFC power supply according to the present invention comprises the following steps:

s100, obtaining current working parameters of the PFC power supply;

s200, when the current working parameters of the PFC power supply meet the condition that a power factor correction circuit of the PFC power supply is closed, controlling the power factor correction circuit of the PFC power supply to be closed, acquiring the voltage at two ends of an electrolytic capacitor of the PFC power supply, and acquiring a first input alternating current voltage peak value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor;

s300, when the current working parameters of the PFC power supply meet the condition that a power factor correction circuit of the PFC power supply is started, controlling the power factor correction circuit to be started, acquiring an input alternating-current voltage instantaneous value of the PFC power supply, and acquiring a second input alternating-current voltage peak value of the PFC power supply according to the input alternating-current voltage instantaneous value;

s400, calculating the effective value of the alternating voltage of the PFC power supply according to the first input alternating voltage peak value or the second input alternating voltage peak value.

Preferably, the obtaining the voltage across the electrolytic capacitor of the PFC power supply, and then obtaining the first input ac voltage peak value of the PFC power supply according to the voltage across the electrolytic capacitor specifically includes:

s210, collecting voltages at two ends of the electrolytic capacitor in one voltage period of an input alternating current power supply of the PFC power supply, and storing the voltages as a plurality of voltage sampling samples;

s220, obtaining a voltage sampling sample with the maximum voltage value in the plurality of voltage sampling samples;

and S230, calculating a first input alternating current voltage peak value of the PFC power supply according to the voltage value of the voltage sampling sample with the maximum voltage value and a first preset calculation formula.

Preferably, the power factor correction circuit is a BOOST architecture, and the first preset calculation formula is:

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；

vac _ peak1 is the first input AC voltage peak value of the PFC power supply, Vdc _ peak is the maximum value of the voltage added at two ends of the electrolytic capacitor, Vfrd is the conduction voltage drop of a fast recovery diode in the power factor correction circuit, and Vbd is the conduction voltage drop of a rectifier bridge in the PFC power supply.

Preferably, the obtaining an input ac voltage instantaneous value of the PFC power supply, and then obtaining a second input ac voltage peak value of the PFC power supply according to the input ac voltage instantaneous value specifically includes:

s310, detecting the voltage at two ends of the electrolytic capacitor, acquiring the duty ratio of the switching period and the starting time of a power switching tube in the power factor correction circuit, and acquiring the current variation of an inductor in the power factor correction circuit in one switching period of the power switching tube;

s320, calculating an input alternating current voltage instantaneous value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor, the duty ratio of the on-time of the power switch tube, the switching period of the power switch tube, the current variation of the inductor in one switching period of the power switch tube and a second preset calculation formula;

s330, circularly executing the steps S310 to S320 in one voltage period of the input alternating current power supply of the PFC power supply until the calculated input alternating current voltage instantaneous value of the PFC power supply reaches n, wherein n is greater than or equal to 2;

and S340, acquiring the maximum value of the n input alternating current voltage instantaneous values, and taking the maximum value as a second input alternating current voltage peak value of the PFC power supply.

Preferably, the power factor correction circuit is a BOOST architecture, and the second preset calculation formula is:

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；

wherein Vac is an input alternating voltage instantaneous value of the PFC power supply, Vdc is a voltage applied to both ends of the electrolytic capacitor, D is a duty ratio of a power switching tube on time in the power factor correction circuit, Vigbt is a conduction voltage drop of the power switching tube, Vfrd is a conduction voltage drop of a fast recovery diode in the power factor correction circuit, Vbd is a conduction voltage drop of a rectifier bridge in the PFC power supply, L is an inductance value of an inductor in the power factor correction circuit, Δ Iin is a current variation of the inductor in a switching period of the power switching tube, and Ts is a switching period of the power switching tube.

Preferably, the calculating the effective value of the ac voltage of the PFC power supply according to the first input ac voltage peak value or the second input ac voltage peak value specifically includes:

calculating the effective value of the alternating voltage of the PFC power supply according to the first input alternating voltage peak value and a third preset formula; or,

calculating the effective value of the alternating voltage of the PFC power supply according to the second input alternating voltage peak value and a third preset formula;

the third preset formula is

Where, Vac _ rms is the effective value of the ac voltage of the PFC power supply, and Vac _ peak is the peak value of the ac voltage.

Preferably, the current operating parameters of the PFC power supply include:

at least one of a current power value of a load connected with the PFC power supply, a current input current value of the PFC power supply and a current input current peak value of the PFC power supply.

Preferably, the condition that the current operating parameter of the PFC power supply satisfies the condition that the power factor correction circuit of the PFC power supply is turned off includes:

the current power value of a load connected with the PFC power supply is smaller than a preset power value, or the current input current value of the PFC power supply is smaller than a preset input current value, or the current input current peak value of the PFC power supply is smaller than a preset input current peak value;

the condition that the current working parameters of the PFC power supply meet the starting condition of a power factor correction circuit of the PFC power supply comprises the following steps:

the current power value of a load connected with the PFC power supply is larger than or equal to a preset power value, or the current input current value of the PFC power supply is larger than or equal to a preset input current value, or the current input current peak value of the PFC power supply is larger than or equal to a preset input current peak value.

Correspondingly, the invention also provides an apparatus for obtaining the effective value of the alternating voltage of the PFC power supply, comprising:

the working parameter acquisition module is used for acquiring the current working parameters of the PFC power supply;

the first peak voltage acquisition module is used for controlling the power factor correction circuit of the PFC power supply to be closed when the current working parameters of the PFC power supply meet the condition of closing the power factor correction circuit of the PFC power supply, acquiring the voltage at two ends of an electrolytic capacitor of the PFC power supply, and then acquiring a first input alternating current voltage peak value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor;

the second peak voltage acquisition module is used for controlling the power factor correction circuit to be started when the current working parameters of the PFC power supply meet the condition that the power factor correction circuit of the PFC power supply is started, acquiring the input alternating current voltage instantaneous value of the PFC power supply, and then acquiring a second input alternating current voltage peak value of the PFC power supply according to the input alternating current voltage instantaneous value;

and the effective value calculating module is used for calculating the effective value of the alternating voltage of the PFC power supply according to the first input alternating voltage peak value or the second input alternating voltage peak value.

Preferably, the first peak voltage obtaining module includes:

the voltage acquisition unit is used for acquiring the voltages at two ends of the electrolytic capacitor in one voltage period of an input alternating current power supply of the PFC power supply and storing the voltages as a plurality of voltage sampling samples;

the maximum voltage acquisition unit is used for acquiring a voltage sampling sample with the maximum voltage value in a plurality of voltage sampling samples;

and the first peak voltage calculating unit is used for calculating a first input alternating current voltage peak value of the PFC power supply according to the voltage value of the voltage sampling sample with the maximum voltage value and a first preset calculation formula.

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；

Preferably, the second peak voltage obtaining module includes:

the voltage detection subunit is used for detecting the voltage at two ends of the electrolytic capacitor;

the state acquisition subunit is used for acquiring the switching period and the duty ratio of the starting time of a power switching tube in the power factor correction circuit;

the inductor current obtaining subunit is used for obtaining the current variation of an inductor in the power factor correction circuit in one switching period of the power switching tube;

the instantaneous voltage calculation unit is used for calculating an input alternating current voltage instantaneous value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor, the duty ratio of the on-time of the power switch tube, the switching period of the power switch tube, the current variation of the inductor in one switching period of the power switch tube and a second preset calculation formula;

the maximum instantaneous voltage acquisition unit is used for circularly acquiring input alternating current voltage instantaneous values of the PFC power supply within one voltage period of the input alternating current power supply of the PFC power supply until the input alternating current voltage instantaneous values of the PFC power supply obtained through calculation reach n, wherein n is greater than or equal to 2;

and the second peak voltage calculating unit is used for acquiring the maximum value of the n input alternating current voltage instantaneous values and taking the maximum value as the second input alternating current voltage peak value of the PFC power supply.

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；

Preferably, the effective value calculating module is specifically configured to:

the third preset formula is

The method for acquiring the effective value of the alternating voltage of the PFC power supply comprises the following steps: first, the current operating parameters of the PFC power supply are obtained. Then, if the current working parameters of the PFC power supply meet the condition that a power factor correction circuit of the PFC power supply is closed, the power factor correction circuit of the PFC power supply is controlled to be closed, and a first input alternating current voltage peak value of the PFC power supply is obtained according to the voltages at two ends of an electrolytic capacitor; and if the current working parameters of the PFC power supply meet the condition of starting a power factor correction circuit of the PFC power supply, controlling the PFC power supply to be started, and acquiring a second input alternating voltage peak value of the PFC power supply according to the input alternating voltage instantaneous value of the PFC power supply. And finally, calculating the effective value of the alternating voltage of the PFC power supply according to the peak value of the first input alternating voltage or the peak value of the second input alternating voltage. The current interruption mode only appears near the current zero crossing point, but the technical scheme is that when the current working parameters of the PFC power supply meet the condition that a power factor correction circuit of the PFC power supply is started, the second input alternating voltage peak value of the PFC power supply is obtained according to the input alternating voltage instantaneous value of the PFC power supply, and the alternating voltage effective value of the PFC power supply is calculated according to the second input alternating voltage peak value. Therefore, the technical scheme can avoid the interference of the current interruption mode on the result of obtaining the effective value of the alternating voltage of the PFC power supply, and has the characteristic of high accuracy compared with the prior art.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic diagram of a PFC power supply according to the present invention;

fig. 2 is a schematic flowchart of an embodiment of a method for obtaining an effective ac voltage value of a PFC power supply according to the present invention;

FIG. 3 is a detailed flowchart of step S200 in FIG. 2;

FIG. 4 is a detailed flowchart of step S300 in FIG. 2;

fig. 5 is a schematic diagram of functional modules of an embodiment of an ac voltage effective value obtaining apparatus of a PFC power supply according to the present invention;

FIG. 6 is a functional block diagram of an embodiment of the first peak voltage obtaining module shown in FIG. 5;

fig. 7 is a functional block diagram of an embodiment of the second peak voltage obtaining module in fig. 5.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the descriptions relating to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides a method for acquiring an effective value of alternating voltage of a PFC power supply. The topology of the PFC power factor correction circuit has various options, such as BOOST, BUCK, etc.

In order to better understand the technical solution of the present invention, the working principle of the PFC power supply is described herein by taking a BOOST type power factor correction circuit as an example in this embodiment.

As shown in fig. 1, the PFC power supply includes a rectifier bridge BD, an electrolytic capacitor C, and a BOOST-type power factor correction circuit 10, where the BOOST-type power factor correction circuit 10 includes an inductor L, a power switch IGBT, a fast recovery diode FRD, and a controller. The input end of the rectifier bridge BD is used for being connected with an input alternating current power supply AC, the positive end of the rectifier bridge BD is connected with the first end of the inductor L, the second end of the inductor L, the input end of the power switch tube IGBT and the anode of the fast recovery diode FRD are interconnected, the cathode of the fast recovery diode FRD is connected with the anode of the electrolytic capacitor C, and the connection node of the fast recovery diode FRD is used for being connected with the anode of a load. The negative end of the rectifier bridge BD, the output end of the power switch tube IGBT and the negative electrode of the electrolytic capacitor C are interconnected, the connection node of the rectifier bridge BD and the output end of the power switch tube IGBT is used for being connected with the negative electrode of a load, and the controlled end of the power switch tube IGBT is connected with the control end of the controller.

The controller is configured to output a PWM wave to a controlled terminal of the power switching tube IGBT, so as to turn on the power factor correction circuit 10, thereby implementing a power factor correction function.

Specifically, when the power switch tube IGBT is turned on, a current is output from the positive terminal of the rectifier bridge BD, sequentially passes through the inductor L and the power switch tube IGBT, and returns to the negative terminal of the rectifier bridge BD. In the process, the current of the inductor L rises linearly, and the voltage relation of the inductor L meets the following conditions:

Vac＝L×p·Iin+Vigbt+Vbd；(1)

when the power switch tube IGBT is turned off, the current is output from the positive end of the rectifier bridge BD, and returns to the negative end of the rectifier bridge BD through the inductor L, the fast recovery diode FRD and the electrolytic capacitor C (and the load) in sequence. In the process: when the output voltage of the rectifier bridge BD is higher than the voltage of the electrolytic capacitor C, the current of the inductor L continuously rises; when the output voltage of the rectifier bridge BD is lower than the voltage of the electrolytic capacitor C, the current of the inductor L decreases. The voltage relation satisfies:

Vac＝Vdc+L×p·Iin+Vfrd+Vbd；(2)

wherein Vac is an instantaneous value (absolute value) of input alternating voltage of the PFC power supply, Vdc is voltage of an electrolytic capacitor C, Iin is an instantaneous value of current of an inductor L, p is a differential operator, L is an inductance value of the inductor L, Vbd is conduction voltage drop of a rectifier bridge BD, Vigbt is conduction voltage drop of a power switch tube IGBT, and Vfrd is conduction voltage drop of a fast recovery diode FRD.

And setting the period of the PWM wave as Ts, setting the on time of the power switch tube IGBT as Ton, the off time of the power switch tube IGBT as Toff, and recording the duty ratio as D as Ton/Ts, wherein the Ts is Ton + Toff. In each PWM period, the rise time of the inductor L current is referred to as Tup, and the fall time of the inductor L current is referred to as Tfall. The sum of the rise and fall of the inductor L current in each PWM cycle is the final current change Δ Iin, i.e.

(Vac-Vigbt–Vbd)×Tup+(Vac-Vdc-Vfrd–Vbd)×Tfall＝L×ΔIin；(3)

When the power factor correction circuit 10 operates in the current continuous mode or the current critical mode, and Ton ═ Tup and Toff ═ Tfall are satisfied, then:

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；(4)

when the power factor correction circuit 10 operates in the current discontinuous mode, the inductor L current rises from zero and finally falls to zero in the current PWM period, and the final current change Δ Iin is 0, which satisfies Ton Tup and Toff Tfall, then:

Vac＝Vdc×Tfall/(Ton+Tfall)+Vigbt×Ton/(Ton+Tfall)+Vfrd×Tfall/(Ton+Tfall)+Vbd；(5)

since Tfall cannot be directly known when the power factor correction circuit 10 operates in the current interruption mode, the effective value of the ac voltage of the PFC power supply cannot be directly obtained by the above equation (5). Since Toff > Tfall when the power factor correction circuit 10 operates in the current chopping mode, substituting Toff for Tfall into equation (5) above will result in an effective value of the ac voltage that is greater than the actual value. This is the reason why the ac voltage of the PFC power supply obtained by the prior art has a large effective value.

Based on the above description, referring to fig. 2, in an embodiment, the method for estimating the effective value of the ac voltage of the PFC power supply includes the following steps:

s100, obtaining current working parameters of the PFC power supply;

here, the current operating parameter of the PFC power supply may be a power value of a load connected to the PFC power supply; the input current value of the PFC power supply or the input current peak value of the PFC power supply can also be obtained; the input current peak value of the PFC power supply may be equal to or greater than a peak value of the input current of the PFC power supply.

When the PFC power supply outputs the power supply to supply power to the load, if the power factor correction circuit 10 is started, the PFC power supply outputs the power supply with corrected power to the load; if the PFC circuit 10 is turned off, the PFC power source outputs power without power correction to the load.

The load may be an actual electrical device, such as a motor, or an analog device for testing, such as a resistor.

In this embodiment, how to obtain the current operating parameter of the PFC power supply is described by taking the operating parameter as the input current value of the PFC power supply as an example.

Specifically, a detection resistor (not shown) may be connected in series to the current trunk of the PFC power supply, and one end of the detection resistor is grounded, and the other end of the detection resistor is connected to the negative terminal of the rectifier bridge BD or the negative terminal of the load. In this way, the input current of the PFC power supply can be obtained by detecting the voltage falling on the other end of the detection resistor by a voltage detection device (not shown) under the condition of neglecting the influence of temperature, current, etc. on the resistance value of the detection resistor. When the other end of the detection resistor is connected with the negative end of the rectifier bridge BD, the detected voltage is negative voltage; when the other end of the detection resistor is connected to the negative electrode of the load, the detected voltage is a positive voltage. Preferably, the other end of the detection circuit is connected to the negative pole of the load. To widen the selection range of the voltage detection device.

It should be noted that, by adopting the above manner, the peak value of the input current of the PFC power supply may also be obtained.

S200, when the current working parameters of the PFC power supply meet the condition that the power factor correction circuit 10 of the PFC power supply is closed, controlling the power factor correction circuit 10 of the PFC power supply to be closed, acquiring the voltage at two ends of an electrolytic capacitor C of the PFC power supply, and acquiring a first input alternating current voltage peak value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor C;

here, the condition that the current operating parameter of the PFC power supply satisfies the condition that the power factor correction circuit 10 of the PFC power supply is turned off may be selected as follows: the current working parameter of the PFC power supply is smaller than the preset working parameter. For example, the current power value of the load connected to the PFC power supply is smaller than a preset power value, the current input current value of the PFC power supply is smaller than a preset input current value, the current input current peak value of the PFC power supply is smaller than a preset input current peak value, and so on, which are not listed here.

It should be noted that, in the PFC power supply, the power factor correction circuit 10 is provided to reduce the transmission loss of the power supply. When the current operating parameters of the PFC power supply (including the power value of the load connected to the PFC power supply, the input current value of the PFC power supply, the input current peak value of the PFC power supply, and the like) are small, the transmission loss base number of the power supply is small, the effect of the power factor correction circuit 10 is relatively weak, and even the power consumption of the power factor correction circuit 10 itself is larger than the power transmission loss reduced by the power factor correction circuit 10. Therefore, the technical scheme can select whether the power factor correction circuit 10 needs to be started or not according to the actual working state of the PFC power supply, so that the effective value of the alternating voltage of the PFC power supply can be conveniently obtained, and the reactive power loss of the PFC power supply can be kept in a relatively low state.

In addition, in the embodiment, how to determine that the current operating parameter of the PFC power supply is smaller than the preset operating parameter may be implemented in various ways.

For example, obtaining current working parameters of the PFC power supply; calculating the difference value between the current working parameter of the PFC power supply and a preset working parameter; and if the difference is smaller than zero, determining that the current working parameter of the PFC power supply is smaller than the preset working parameter. Therefore, whether the current working parameter of the PFC power supply is smaller than the preset working parameter or not can be quickly determined.

Or, acquiring the current working parameters of the PFC power supply; calculating the difference value between the current working parameter of the PFC power supply and a preset working parameter; circularly executing the actions to obtain the difference value between the current working parameters of the PFC power supply and the preset working parameters; calculating an average value of the plurality of difference values; and if the average value of the difference values is smaller than zero, determining that the current working parameter of the PFC power supply is smaller than the preset working parameter. Therefore, the influence of detection errors on the data acquisition result can be avoided, and the reliability is further improved.

It should be noted that, if the operating parameter is the input current of the PFC power supply, the preset input current value of the PFC power supply may be selected from 1 ampere to 2 amperes.

Preferably, referring to fig. 3, the following method can be adopted to obtain the voltage across the electrolytic capacitor C of the PFC power supply, and obtain the first input ac voltage peak value of the PFC power supply according to the voltage across the electrolytic capacitor C:

s210, collecting voltages at two ends of an electrolytic capacitor C in one voltage period of an input Alternating Current (AC) power supply of a Power Factor Correction (PFC) power supply, and storing the voltages as a plurality of voltage sampling samples;

It can be understood that, in one voltage cycle of the input AC power AC of the PFC power supply, the more voltage sample samples are stored, the closer the voltage value of the voltage sample with the largest voltage value is to the first input AC voltage peak value of the PFC power supply. Preferably, in the present embodiment, the number of stored voltage sample samples is between 50 and 100.

In addition, according to the operating principle of the PFC power supply, when the power factor correction circuit 10 is turned off, the power switching tube IGBT is turned off, and the rectifier bridge BD, the inductor L, the fast recovery diode FRD, and the electrolytic capacitor C form a current loop, so that there are:

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；(6)

where Vac _ peak1 is the first input ac peak of the PFC supply, and Vdc _ peak is the maximum voltage across the electrolytic capacitor C. The above equation (6) is the first predetermined calculation equation.

When the power factor correction circuit 10 is in the off state, the above equation (6) is always satisfied, and when the stored voltage sample is sufficiently large, the sum of the voltage value of the voltage sample with the largest voltage value, the conduction voltage drop of the fast recovery diode FRD, and the conduction voltage drop of the rectifier bridge BD is almost equal to the first input ac voltage peak value of the PFC power supply. Therefore, the present embodiment can obtain an accurate peak value of the first input ac voltage.

S300, when the current working parameters of the PFC power supply meet the starting condition of the PFC power supply power factor correction circuit 10, controlling the power factor correction circuit 10 to be started, acquiring an input alternating current voltage instantaneous value of the PFC power supply, and acquiring a second input alternating current voltage peak value of the PFC power supply according to the input alternating current voltage instantaneous value;

here, the condition that the current operating parameter of the PFC power supply satisfies the condition that the power factor correction circuit 10 of the PFC power supply is turned on may be selected as: the current working parameter of the PFC power supply is larger than or equal to the preset working parameter. For example, the current power value of the load connected to the PFC power supply is greater than or equal to a preset power value, the current input current value of the PFC power supply is greater than or equal to a preset input current value, the current input current peak value of the PFC power supply is greater than or equal to a preset input current peak value, and so on, which are not listed here.

It should be noted that, in the PFC power supply, the power factor correction circuit 10 is provided to reduce the transmission loss of the power supply. When the current operating parameters of the PFC power supply (including the power value of the load connected to the PFC power supply, the input current value of the PFC power supply, the input current peak value of the PFC power supply, and the like) are large, the transmission loss base number of the power supply is large, and the effect of the power factor correction circuit 10 is relatively obvious. Therefore, the technical scheme can select whether the power factor correction circuit 10 needs to be started or not according to the actual working state of the PFC power supply, so that the effective value of the alternating voltage of the PFC power supply can be conveniently obtained, and the reactive power loss of the PFC power supply can be kept in a relatively low state.

In addition, in the embodiment, various means may be adopted for determining how to determine that the current operating parameter of the PFC power supply is greater than or equal to the preset operating parameter.

For example, obtaining current working parameters of the PFC power supply; calculating the difference value between the current working parameter of the PFC power supply and a preset working parameter; and if the difference is greater than or equal to zero, determining that the current working parameter of the PFC power supply is greater than or equal to a preset working parameter. In this way, whether the current operating parameter of the PFC power supply is greater than or equal to the preset operating parameter can be quickly determined.

Or, acquiring the current working parameters of the PFC power supply; calculating the difference value between the current working parameter of the PFC power supply and a preset working parameter; circularly executing the actions to obtain the difference value between the current working parameters of the PFC power supply and the preset working parameters; calculating an average value of the plurality of difference values; and if the average value of the difference values is larger than or equal to zero, determining that the current working parameter of the PFC power supply is larger than or equal to a preset working parameter. Therefore, the influence of detection errors on the data acquisition result can be avoided, and the reliability is further improved.

Preferably, referring to fig. 4, the input ac voltage instantaneous value of the PFC power supply can be obtained as follows, and the second input ac voltage peak value of the PFC power supply can be obtained according to the input ac voltage instantaneous value:

s310, detecting the voltage at two ends of the electrolytic capacitor C, acquiring the duty ratio of the switching period and the opening time of a power switch tube IGBT in the power factor correction circuit 10, and acquiring the current variation of an inductor L in the power factor correction circuit 10 in one switching period of the power switch tube IGBT;

s320, calculating an input alternating current voltage instantaneous value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor C, the duty ratio of the turn-on time of the power switch tube IGBT, the switching period of the power switch tube IGBT, the current variation of the inductor L in one switching period of the power switch tube IGBT and a second preset calculation formula;

s330, circularly executing the steps S310 to S320 in one voltage period of the input Alternating Current (AC) power supply of the PFC power supply until the calculated input AC voltage instantaneous value of the PFC power supply reaches n, wherein n is greater than or equal to 2;

It can be understood that, within one voltage cycle of the input AC power supply AC of the PFC power supply, the more input AC voltage instantaneous values of the PFC power supply are calculated, the closer the maximum value of the input AC voltage instantaneous values is to the second input AC voltage peak value of the PFC power supply. Preferably, in this embodiment, the input ac voltage instantaneous value of the PFC power supply is calculated to be between 50 and 100.

Furthermore, according to the operation principle of the PFC power supply, when the power factor correction circuit 10 operates in the continuous current mode or the critical current mode, the input ac voltage instantaneous value can be calculated by using the following formula:

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；(7)

the above equation (7) is the second predetermined calculation equation.

Since the current flowing through the load is large when the power factor correction circuit 10 is in the on state, and is already far from the current zero crossing point, the power factor correction circuit 10 is less likely to operate in the discontinuous current mode. Therefore, the present embodiment can obtain an accurate peak value of the second input ac voltage.

And S400, calculating the effective value of the alternating voltage of the PFC power supply according to the peak value of the first input alternating voltage or the peak value of the second input alternating voltage.

Specifically, the effective value of the alternating voltage of the PFC power supply is calculated according to a first input alternating voltage peak value and a third preset formula; or calculating the effective value of the alternating voltage of the PFC power supply according to the second input alternating voltage peak value and a third preset formula.

Here, the third predetermined formula is

The method for acquiring the effective value of the alternating voltage of the PFC power supply comprises the following steps: first, the current operating parameters of the PFC power supply are obtained. Then, if the current working parameters of the PFC power supply meet the condition that the power factor correction circuit 10 of the PFC power supply is closed, controlling the power factor correction circuit 10 of the PFC power supply to be closed, and acquiring a first input alternating current voltage peak value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor C; and if the current working parameters of the PFC power supply meet the condition that the power factor correction circuit 10 of the PFC power supply is started, controlling the PFC power supply to be started, and acquiring a second input alternating voltage peak value of the PFC power supply according to the input alternating voltage instantaneous value of the PFC power supply. And finally, calculating the effective value of the alternating voltage of the PFC power supply according to the peak value of the first input alternating voltage or the peak value of the second input alternating voltage. Because the current interruption mode only appears near the current zero crossing point, the technical scheme is that when the current working parameters of the PFC power supply meet the condition that the power factor correction circuit 10 of the PFC power supply is started, the second input alternating voltage peak value of the PFC power supply is obtained according to the input alternating voltage instantaneous value of the PFC power supply, and the alternating voltage effective value of the PFC power supply is calculated according to the second input alternating voltage peak value. Therefore, the technical scheme can avoid the interference of the current interruption mode on the result of obtaining the effective value of the alternating voltage of the PFC power supply, and has the characteristic of high accuracy compared with the prior art.

Correspondingly, the present invention further provides an apparatus for obtaining an effective ac voltage value of a PFC power supply, referring to fig. 5, in an embodiment, the apparatus includes:

a working parameter obtaining module 100, configured to obtain current working parameters of the PFC power supply;

The first peak voltage obtaining module 200 is configured to control the power factor correction circuit 10 of the PFC power supply to be turned off when the current working parameter of the PFC power supply meets a condition that the power factor correction circuit 10 of the PFC power supply is turned off, obtain voltages at two ends of an electrolytic capacitor C of the PFC power supply, and obtain a first input ac voltage peak value of the PFC power supply according to the voltages at the two ends of the electrolytic capacitor C;

Preferably, referring to fig. 6, the first peak voltage obtaining module 200 includes:

the voltage acquisition unit 210 is configured to acquire voltages at two ends of the electrolytic capacitor C within one voltage cycle of the input AC power AC of the PFC power supply, and store the voltages as a plurality of voltage sampling samples;

a maximum voltage obtaining unit 220, configured to obtain a voltage sample with a maximum voltage value among the multiple voltage samples;

the first peak voltage calculating unit 230 is configured to calculate a first input ac voltage peak value of the PFC power according to the voltage value of the voltage sample with the largest voltage value and a first preset calculation formula.

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；(6)

A second peak voltage obtaining module 300, configured to control the power factor correction circuit 10 to start when the current working parameter of the PFC power supply meets a start condition of the power factor correction circuit 10 of the PFC power supply, obtain an input ac voltage instantaneous value of the PFC power supply, and then obtain a second input ac voltage peak value of the PFC power supply according to the input ac voltage instantaneous value;

Preferably, referring to fig. 7, the second peak voltage obtaining module 300 includes:

a voltage detection subunit 311 for detecting the voltage across the electrolytic capacitor C;

a state obtaining subunit 312, configured to obtain a switching period and a duty ratio of a turn-on time of a power switching tube IGBT in the power factor correction circuit 10;

an inductor L current obtaining subunit 313, configured to obtain a current variation of the inductor L in the power factor correction circuit 10 in one switching cycle of the power switching tube IGBT;

the instantaneous voltage calculating unit 320 is used for calculating an input alternating voltage instantaneous value of the PFC power supply according to the voltage at the two ends of the electrolytic capacitor C, the duty ratio of the turn-on time of the power switch tube IGBT, the switching period of the power switch tube IGBT, the current variation of the inductor L in one switching period of the power switch tube IGBT and a second preset calculating formula;

a maximum instantaneous voltage obtaining unit 330, configured to cyclically obtain an input alternating current voltage instantaneous value of the PFC power supply within one voltage period of the input alternating current power supply AC of the PFC power supply until the calculated input alternating current voltage instantaneous value of the PFC power supply reaches n, where n is greater than or equal to 2;

and a second peak voltage calculating unit 340, configured to obtain a maximum value of the n input ac voltage instantaneous values, and use the maximum value as a second input ac voltage peak value of the PFC power supply.

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；(7)

the above equation (7) is the second predetermined calculation equation.

And an effective value calculating module 400, configured to calculate an effective value of the ac voltage of the PFC power supply according to the first input ac voltage peak value or the second input ac voltage peak value. Specifically, the method is used for calculating the effective value of the alternating voltage of the PFC power supply according to the first input alternating voltage peak value and a third preset formula; or calculating the effective value of the alternating voltage of the PFC power supply according to the second input alternating voltage peak value and a third preset formula.

Here, the third predetermined formula is

In the ac voltage effective value acquisition device of the PFC power supply: first, the operating parameter acquiring module 100 acquires the current operating parameters of the PFC power supply. Then, when the current working parameter of the PFC power meets the condition that the power factor correction circuit 10 of the PFC power is turned off, the first peak voltage obtaining module 20 controls the power factor correction circuit 10 of the PFC power to be turned off, and obtains a first input ac voltage peak value of the PFC power according to the voltage at the two ends of the electrolytic capacitor C; the second peak voltage obtaining module 300 controls the PFC power supply to be turned on when the current working parameter of the PFC power supply meets the condition that the power factor correction circuit 10 of the PFC power supply is turned on, and obtains a second input ac voltage peak value of the PFC power supply according to the input ac voltage instantaneous value of the PFC power supply. Finally, the effective value calculating module 400 calculates the effective value of the ac voltage of the PFC power according to the first input ac voltage peak value or the second input ac voltage peak value. Because the current interruption mode only appears near the current zero crossing point, the technical scheme is that when the current working parameters of the PFC power supply meet the condition that the power factor correction circuit 10 of the PFC power supply is started, the second input alternating voltage peak value of the PFC power supply is obtained according to the input alternating voltage instantaneous value of the PFC power supply, and the alternating voltage effective value of the PFC power supply is calculated according to the second input alternating voltage peak value. Therefore, the technical scheme can avoid the interference of the current interruption mode on the result of obtaining the effective value of the alternating voltage of the PFC power supply, and has the characteristic of high accuracy compared with the prior art.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A method for obtaining an effective value of an alternating voltage of a PFC power supply is characterized by comprising the following steps:

s100, obtaining current working parameters of the PFC power supply;

2. The method according to claim 1, wherein the obtaining the voltage across the electrolytic capacitor of the PFC power supply and then obtaining the first input ac voltage peak value of the PFC power supply according to the voltage across the electrolytic capacitor specifically comprises:

3. The method according to claim 2, wherein the power factor correction circuit is a BOOST architecture, and the first predetermined calculation formula is:

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；

4. The method according to claim 1, wherein the obtaining an input ac voltage instantaneous value of the PFC power supply, and then obtaining a second input ac voltage peak value of the PFC power supply according to the input ac voltage instantaneous value specifically comprises:

5. The method according to claim 4, wherein the power factor correction circuit is a BOOST architecture, and the second predetermined calculation formula is:

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；

6. The method according to claim 1, wherein the calculating the ac voltage effective value of the PFC power according to the first input ac voltage peak value or the second input ac voltage peak value specifically includes:

the third preset formula is

7. The ac voltage effective value obtaining method of the PFC power supply according to claim 1, wherein the current operating parameters of the PFC power supply include:

8. The method according to claim 7, wherein the step of obtaining the effective value of the AC voltage of the PFC power supply comprises the step of obtaining the effective value of the AC voltage of the PFC power supply,

the condition that the current working parameters of the PFC power supply meet the condition that a power factor correction circuit of the PFC power supply is closed comprises the following steps:

9. An apparatus for obtaining an effective value of an alternating voltage of a PFC power supply, comprising:

the first peak voltage acquisition module is used for controlling the power factor correction circuit of the PFC power supply to be closed when the current working parameters of the PFC power supply meet the condition that the power factor correction circuit of the PFC power supply is closed, acquiring the voltage at two ends of an electrolytic capacitor of the PFC power supply, and then acquiring a first input alternating current voltage peak value of the PFC power supply according to the voltage at two ends of the electrolytic capacitor;

10. The apparatus for acquiring effective value of ac voltage of PFC power supply of claim 9, wherein the first peak voltage acquiring module comprises:

11. The apparatus according to claim 10, wherein the power factor correction circuit is a BOOST architecture, and the first predetermined calculation formula is:

Vac_peak 1＝Vdc_peak+Vfrd+Vbd；

12. The apparatus for acquiring effective value of ac voltage of PFC power supply of claim 9, wherein the second peak voltage acquiring module comprises:

13. The apparatus according to claim 12, wherein the power factor correction circuit is a BOOST architecture, and the second predetermined calculation formula is:

Vac＝Vdc×(1-D)+Vigbt×D+Vfrd×(1-D)+Vbd+L×ΔIin/Ts；

14. The apparatus for obtaining an effective value of an alternating voltage of a PFC power supply of claim 9, wherein the effective value calculating module is specifically configured to:

the third preset formula is

15. The apparatus for obtaining the effective value of ac voltage of the PFC power supply of claim 9, wherein the current operating parameters of the PFC power supply include:

16. The apparatus for obtaining the effective value of alternating voltage of a PFC power supply of claim 15,

the current power value of a load connected with the PFC power supply is smaller than a preset power value, or the current input current value of the PFC power supply is smaller than a preset input current value, or the current input current of the PFC power supply is smaller than a preset input current peak value;