Apparatus and method for controlling charge for battery

An apparatus for controlling a charge for a battery is provided. The apparatus includes an input unit that is configured to convert alternating current (AC) input power into direct current (DC) power. A first converter is configured to store or output the DC power and a circuit unit is configured to filter or boost output power based on a normal operation state or an instantaneous power failure state of the AC input power. In addition, a second converter is configured to convert the filtered or boosted power and supply the power to a high voltage battery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Korean Patent Application No. 10-2013-0152985 filed on Dec. 10, 2013, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a power factor correction (PFC) converter circuit, and more particularly, to an apparatus and a method for controlling a charge for a battery that reduces a PFC output voltage and/or current ripple and/or increases a hold-up time based on an output density of an on-board charger (OBC).

BACKGROUND

Generally, in connection with a development of an environmentally friendly vehicle, such as a plug-in hybrid and a hybrid vehicle, a converter for charging an alternating current-direct current (AC-DC) high voltage battery (hereinafter, OBC) may be an essential component. The OBC includes a power factor correction (PFC) converter to improve a power factor. An output terminal of the PFC needs to be provided with a large-capacity output power capacitor to absorb a voltage and current ripple and secure an instantaneous power failure hold-up time. This is schematically illustrated inFIG. 1. Referring toFIG. 1, a PFC converter circuit110is configured to include a PFC inductor111, a PFC output capacitor112, and the like. Further, the PFC converter circuit110is configured to further include an input unit101, a DC-DC converter140, a high voltage battery150, and the like.

Herein, a concept of the hold-up time is briefly represented by the following Equation.
½CPFC(VPFC_cap2−Vmin2)=Powerout×THold-upEquation 1

In the above Equation 1, the left side is proportional to a capacity of a capacitor as energy stored in the PFC output capacitor112. In the above Equation 1, Vminis a minimum PFC output voltage which may emit an OBC normal output. That is, to increase the hold-up time in the condition in which the OBC output is fixed, there is a need to increase a capacity C_pfc of the capacitor or a voltage V_pfc_cap applied to the capacitor.

However, since a separate circuit is not generally present in the vicinity of the PFC output capacitor, a voltage level of the capacitor may not be increased at the time of AC power instantaneous power failure. Therefore, to increase the hold-up time, only a method for increasing the capacity of the capacitor has been developed. Further, to reduce the PFC output voltage and/or current ripple, only a method for increasing a capacity of a PFC inductor and capacitor has been developed. This may increase the overall size and cost of the OBC, reduce an output density, and cause a problem of a configuration of a high voltage charging system package.

In other words, to reduce the voltage and current ripple of the output terminal of the PFC, there is a need to increase a magnitude in a capacitance of the output capacitor. However, since the capacitor is generally a component that occupies a largest volume within the OBC, there is a limitation in increasing the capacitance of the capacitor to improve the output density of the OBC. That is, an optimal capacity of the capacitor needs to be selected in consideration of the reduction in the output voltage ripple and/or the reduction in the package size of the OBC.

SUMMARY

An exemplary embodiment of the present invention is directed to an apparatus and a method for controlling a charge for a battery that may improve a power factor correction (PFC) output voltage in consideration of an output density of an on-board charger (OBC). Further, an exemplary embodiment of the present invention is directed to an apparatus and a method for controlling a charge for a battery capable of reducing a current ripple and/or increasing a hold-up time in consideration of an output density of an on-board charger (OBC). To achieve the above problem, an apparatus for controlling a charge for a battery is provided to improve a power factor correction (PFC) output voltage in consideration of an output density of an on-board charger (OBC).

The apparatus for controlling a charge for a battery may include: an input unit configured to convert alternating current (AC) input power into direct current (DC) power; a first converter configured to store or output the DC power; an additional circuit unit configured to filter or boost output power based on a normal operation state (e.g., when no failure occurs) or an instantaneous power failure state of the AC input power; and a second converter configured to convert the filtered or boosted power and supply the power to a high voltage battery.

The first converter may include: a first inductor; and a first output capacitor configured to be connected to the first inductor in parallel. The additional circuit unit may include: a second inductor configured to be connected to the first inductor in series and connected to the first output capacitor in parallel; a second output capacitor configured to be connected to the first output capacitor in parallel; a first switch configured to be connected to the second inductor in parallel; and a second switch configured to be connected to the second inductor in series.

When the AC input power is in the normal operation state, the first switch may maintained a turned off state (e.g., may remain turned off) and the second switch may hold a turn on state (e.g., may remain turned on). The first inductor and the first output capacitor may be a one-stage filter and the second inductor and the second output capacitor may be a two-stage filter. When the AC input power is in the instantaneous power failure state, the first switch and the second switch may be in an alternately turned on or off state.

A voltage of the first output capacitor may be boosted and thus may be stored in the second output capacitor to increase a hold-up time. The second inductor may be a low-capacity inductor which is equal to or smaller than the first inductor and the second output capacitor may be a low-capacity capacitor which is equal to or smaller than the first output capacitor. The second converter may be a direct current-direct current (DC-DC) converter.

A method for controlling a charge for a battery may include the steps of: converting input power to convert alternating current (AC) input power into direct current (DC) power; storing or outputting the DC power; filtering or boosting output power based on a normal operation state or an instantaneous power failure state of the AC input power; and converting the filtered or boosted power and supply the power to a high voltage battery. The storing or outputting may be performed using a first converter. The filtering or boosting may be performed using an additional circuit unit.

DETAILED DESCRIPTION

Since the present invention may be variously modified and have several exemplary embodiments, specific exemplary embodiments will be shown in the accompanying drawings and be described in detail in a detailed description. However, it is to be understood that the present invention is not limited to the specific exemplary embodiments, but includes all modifications, equivalents, and substitutions included in the spirit and the scope of the present invention. Throughout the accompanying drawings, the same reference numerals will be used to describe the same components.

Terms used in the specification, ‘first’, ‘second’, etc., may be used to describe various components, but the components are not to be construed as being limited to the terms. The terms are used to distinguish one component from another component. For example, the ‘first’ component may be named the ‘second’ component and the ‘second’ component may also be similarly named the ‘first’ component, without departing from the scope of the present invention. The term ‘and/or’ includes a combination of a plurality of items or any one of a plurality of terms.

Unless indicated otherwise, it is to be understood that all the terms used in the specification including technical and scientific terms has the same meaning as those that are understood by those who skilled in the art. It must be understood that the terms defined by the dictionary are identical with the meanings within the context of the related art, and they should not be ideally or excessively formally defined unless the context clearly dictates otherwise.

Hereinafter, an apparatus and a method for controlling a charge for a battery according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2is an exemplary block configuration diagram of an apparatus200for controlling a charge for a battery according to an exemplary embodiment of the present invention. Referring toFIG. 2, the apparatus200for controlling a charge for a battery may include an input unit201configured to convert alternating current (AC) input power into direct current (DC) power, a first converter210configured to store or output the DC power, an additional circuit unit220configured to filter or boost output power based on a normal operation state (e.g., when no failure occurs) or an instantaneous power failure state of the AC input power, and a second converter240configured to convert the filtered or boosted power and supply the converted power to a high voltage battery250, and the like.

The input unit201may be configured to remove an AC component of power to make a DC component. Therefore, the input unit201may include a half-wave rectification circuit, a full-wave rectification circuit, a bridge full-wave rectification circuit, and the like. The first converter210may be a power factor correction (PFC) converter and may include a first inductor211, a first output capacitor212, and the like. Further, the second converter240may be a direct current-direct current (DC-DC) converter. The DC-DC converter is widely known, and therefore will no longer be described to clearly understand the present invention.

The power factor correction (PFC) may be a power saving circuit to improve power efficiency in a power supply apparatus, and a satisfactory PFC type may have harmonics without an (e.g., sinusoidal form) input line current having a substantially unique power factor on a change in a wide load, satisfactory wiring and load adjustment having a right output dynamic, a substantially small size, a substantially light weight, decreased number of components, economic efficiency, high power conversion efficiency, and low electromagnetic interference.

The additional circuit unit220may include a second inductor221, a second output capacitor227, first and second switches223and225, and the like which may be operated by being connected to the first inductor211and the first output capacitor212of the first converter210. Further, the additional circuit unit220may be operated as a two-stage filter or a boost converter by controlling a turn on/or off of the first switch223and/or the second switch225based on a normal operation state (that is, AC-free instantaneous power failure state) or an AC instantaneous power failure state.

In other words, the normal operation state is as follows. The first converter210and the second converter240may be the same as a general operation. In the additional circuit unit220, the first switch223may always be turned off and the second switch225may always be turned on. Accordingly, the two-stage filter may be disposed at the output to reduce a PFC output voltage and current ripple. In other words, a one-stage filter may include the first inductor211and the first output capacitor212and the two-stage filter may include the second inductor221and the second output capacitor227.

The AC instantaneous power failure state is as follows. The first converter210and the second converter240may be the same as a general operation. In the additional circuit unit220, the first switch223and the second switch225may be alternately switched and thus may be operated as the boost converter. In other words, the voltage of the first output capacitor212may be boosted and thus may be stored in the second output capacitor227. This will be represented by the following Equation.
½(CPFC1+CPFC2)(VPFC_cap22−Vmin2)≈½CPFC1(VPFC_cap22−Vmin2)=Powerout×THold-upEquation 2

In the above Equation 2, CPFC1represents a capacity of the first output capacitor, CPFC2represents a capacity of the second output capacitor, Vminrepresents a minimum PFC output voltage which may emit a normal output, THold-uprepresents a hold-up time, and VPFC_cap2represents a voltage applied to the second output capacitor. The normal output may be when a constant power is maintained at the output terminal. In other words, the normal output may be when the Poweroutis in a state of stability. The second output capacitor is smaller than the first output capacitor and therefore may be substantially disregarded. The Equation of the hold-up time according to the exemplary embodiment of the present invention may depend on the above Equation 2 and since a Vpfc_cap2voltage may be held for a substantial period of time compared to a generally known technology, the hold-up time may be increased. In other words, the energy stored in the first output capacitor212may be sufficiently used to increase the hold-up time.

FIG. 3is an exemplary diagram illustrating a circuit diagram of the apparatus200for controlling a charge for a battery illustrated inFIG. 2. Referring toFIG. 3, the input unit201may be configured of a bridge diode circuit. The first converter210may include the first inductor211, the first output capacitor212connected to the first inductor211in parallel, the switching devices, and the like.

Further, the additional circuit unit220may include the second inductor221connected to the first inductor211in series and connected to the first output capacitor212in parallel, the second output capacitor227connected to the first output capacitor212in parallel, the first switch223connected to the second inductor221in parallel, and the second switch225connected to the second inductor221in series, and the like. In particular, as the first and second switches223and225, a field effect transistor (FET), a TRIAC, a silicon controlled rectifier (SCR), a diode alternating current (DIAC), a relay, an insulated gate bipolar transistor (IGBT), and the like may be used. In addition, the second inductor221may be a low-capacity inductor which may be equal to or smaller than the first inductor211. The second output capacitor227may be a low-capacity capacitor which may be equal to or smaller than the first output capacitor212.

In the normal state, the first switch221may always be turned off and the second switch225may always be turned on to apply the two-stage filter to the PFC output, and thus, reducing the PFC output voltage and/or current ripple. In other words, the first inductor211and the first output capacitor212may be a first stage filter and the second inductor221and the second output capacitor227may be a second stage filter. Therefore, at the time of a design to show up the output ripple of the equivalent level compared to the generally known technology, the capacity of the first output capacitor212and the first inductor211which have a substantially large capacity may be reduced. Therefore, comparing the overall size and cost with the general technology, it may be designed at the equivalent level or smaller.

Further, in the AC instantaneous power failure state, the first and second switches223and225may be alternately switched and thus may be operated as the boost converter. Therefore, the voltage of the first output capacitor212may be boosted and stored in the second output capacitor227to increase the time when the PFC output voltage is reduced to a minimum voltage V_min which may emit a normal output of an on-board charger, thereby holding the OBC normal output for a substantial period of time compared to the generally known technology. Accordingly, an increase in the hold-up time occurs. Therefore, it may be possible to reduce the capacitance of the PFC output capacitor at the time of the design to maintain the hold-up time of the equivalent level to the generally known technology. In addition, the cost may be reduced and the overall size of the OBC may be reduced.

The hold-up time may be the time to continuously hold the output of the OBC during the AC power instantaneous power failure by using the energy stored in the output capacitor. During the AC power instantaneous power failure, when the OBC output is held using the energy stored in the capacitor, the voltage of the capacitor may decrease and an arrival time to the minimum voltage level to hold the OBC output may become a hold-up time. Therefore, when the voltage of the capacitor is increased before the OBC output holding minimum voltage is reached, the arrival time to the OBC output holding minimum voltage level may increase and therefore the hold-up time may increase.

FIG. 4is an exemplary flow chart illustrating an operation process of switches223and225during a normal operation according to an exemplary embodiment of the present invention. Referring toFIG. 4, when the AC input power of the input unit201(FIG. 3) is in the normal operation state, the first switch223(FIG. 3) may always be turned off and the second switch225may always be turned on (steps S410and S420). In particular, the first converter210and the additional circuit unit220may be operated as the two-stage filter.

FIG. 5is an exemplary flow chart illustrating a process of increasing a hold-up time based on an operation of the switches223and225and capacitors212and227during a generation of an instantaneous power failure according to another exemplary embodiment of the present invention. Referring toFIG. 5, when the AC input power of the input unit201(FIG. 3) is in the instantaneous power failure state, the first switch223and the second switch225may be alternately switched every predetermined period, that is, at predetermined intervals (steps S510and S520). The voltage of the first output capacitor212(FIG. 3) may be boosted by the alternative switching and the boosted voltage may be stored in the second output capacitor227(FIG. 3) (steps S530and S540). The boosted voltage may be stored in the second output capacitor227and thus the hold-up time may increase (step S550).

FIG. 6is an exemplary graph comparing a general hold-up time to a hold-up time according to an exemplary embodiment of the present invention. Referring toFIG. 6, according to the exemplary embodiment of the present invention, a hold-up time620may be greater than a general hold-up time610(e.g., a conventional hold-up time). Further, according to the exemplary embodiment of the present invention, a voltage640of the second output capacitor may be more stably held than a voltage of the general output capacitor.

According to the exemplary embodiments of the present invention, the inductor, the switch, and the output capacitor may be configured in plural to control the turning on and off of the plurality of switches during the normal operation and the generation of AC instantaneous power failure, thus reducing the PFC output voltage and current ripple. Further, one switch may always be turned off and the remaining switches may always be turned on to apply the two-stage filter to the PFC output, thus reducing the capacity of the PFC output inductor and the output capacitor. Accordingly, the cost may be reduced and the overall size of the on-board charger (OBC) may be reduced.

In addition, according to the exemplary embodiments of the present invention, the plurality of switches may be alternately switched at the time of the generation of the AC instantaneous power failure, and as a result may be operated as the boost converter. In other words, the voltage of one PFC output capacitor may be boosted and stored in another PFC output capacitor to increase the time when the PFC output voltage is reduced to the minimum voltage V_min which may emit the OBC normal output, to maintain the OBC normal output with respect to the general circuit for a substantial period of time. Accordingly, an increase in the hold-up time may occur. Therefore, it may be possible to reduce the capacity of the PFC output capacitor at the time of a design to maintain the hold-up time of the equivalent level to the related circuit. Thus, the cost may be reduced and the overall size of the OBC may be reduced.

Hereinabove, although the present invention is described by specific matters such as concrete components, and the like, exemplary embodiments, and drawings, they are provided merely for assisting in the entire understanding of the present invention. Therefore, the present invention is not limited to the exemplary embodiments. Various modifications and changes may be made by those skilled in the art to which the present invention pertains from this description.