JP6016595B2 - Charger - Google Patents

Description

  The present invention relates to a charger for charging a storage battery mounted on, for example, various electric vehicles, hybrid vehicles, and the like, and in particular, to a battery that is charged by a multistage constant current charging method, to achieve downsizing and high efficiency. It relates to things devised to be able to

The charging voltage and charging current of the multi-stage constant current charging method are as shown in FIG. The diagram shown on the upper side in FIG. 5 is a diagram showing the charge voltage characteristics, and the time (t) is plotted on the horizontal axis and the charge voltage is plotted on the vertical axis, showing the time variation of the charge voltage. Further, the lower diagram in FIG. 5 is a diagram showing the charging current, and the time (t) is plotted on the horizontal axis and the charging current is plotted on the vertical axis, showing the time variation of the charging current.
The multi-stage constant current charging method is a charging method for extending the life of the storage battery, reducing the charging time, and increasing the charging efficiency. For the above purpose, the constant current values (I _z , I _max ), the charging voltage regulation value (V _reg ), and the maximum charging voltage (V _max ) of each stage are preset as values specific to the storage battery.
The maximum charging voltage (V _max ) is set as a value larger than the charging voltage regulation value (V _reg ).

As shown in FIG. 5, charging in the multi-stage constant current charging method is performed, for example, in three stages, that is, the first stage (1 stage), the middle stage (2 stages), and the last stage (3 stages). Is 25A, the middle stage charging current is 15A, and the last stage charging current is 8A. Also, the first stage of the charging current 25A has become a maximum charging current _{I max.}

On the other hand, is a charge voltage, the first stage, not exceed the middle both in the charging voltage regulation value _V reg (28.8V), has led to 35V beyond the charging at the final stage voltage regulation value _V reg (28.8V) . This is the maximum charging voltage _{V max.}
In the constant current charging, the constant current value is switched using the charging voltage regulation value V _reg as a guide.

As described above, the maximum charging current I _max is the first stage charging current, and the maximum charging voltage V _max is the last stage maximum charging voltage. The actual DC voltage converter of the charger is not able to output a maximum charge voltage V _max in the maximum charging current I _max, as the design, can output the maximum charge voltage V _max in the maximum charging current I _max It has become a structure. That is, the number of turns of the transformer secondary winding has a number of turns which can output the maximum charge voltage V _max, also wire diameter has a diameter which can output the maximum charging current I _max.

Further, the transformer turns ratio n ₀ (number of turns of the secondary winding / number of turns of the primary winding) that can output the maximum charging voltage V _max is calculated by the following equation (I).

V ₀ = V _max = n ₀ · D · V _in ―― (I)

However,
V ₀ : Output voltage V _{max of} charger: Maximum charging voltage n ₀ : Turn ratio of transformer capable of outputting maximum charging voltage V _max (number of turns of secondary winding / number of turns of primary winding)
D: Duty of main switch (main switch on time / main switch switching cycle)
V _in : Input voltage Note that the loss of each element of the main switch of the primary side circuit and the loss of the diode of the secondary side circuit are ignored.

  As an example of the configuration of this type of charger, there is, for example, Patent Document 1, and as an example of a multistage constant current charging method, there is Non-Patent Document 1, for example.

JP 2003-288948 A

Report of Central Research Institute of Electric Power Development of multi-stage constant current charging method for sealed lead-acid batteries for electric vehicles Research report: T97011 April 1998, published by Central Research Institute of Electric Power Industry

The conventional configuration has the following problems.
That is, the conventional charger, the design, the maximum capable of outputting a charging voltage V _max configured by the maximum charging current I _max. In other words, the number of turns of the transformer secondary winding has a number of turns which can output the maximum charge voltage V _max, also wire diameter has a diameter which can output the maximum charging current I _max. For this reason, there is a problem that the transformer and the charger are enlarged and the cost is increased.
In addition, the reverse applied voltage of the secondary side rectifier diode or commutation diode becomes high, and therefore, a rectifier diode or commutation diode having a large forward voltage drop and a high reverse breakdown voltage must be used. There was also a problem of inefficiency.

  The present invention has been made based on these points, and an object of the present invention is to provide a multistage constant current charging type charger capable of achieving downsizing and high efficiency.

In order to achieve the above object, a battery charger according to claim 1 of the present invention comprises a power factor improving unit and a DC voltage converter, and is charged by a multi-stage constant current charging method, wherein the DC voltage converter is a main switch. A primary side circuit including a smoothing coil, and a transformer including a primary winding and a secondary winding interposed between the primary side circuit and the secondary side circuit. The transformer turns ratio (n ₁ : number of secondary windings / number of primary windings) is determined based on the charging voltage regulation value (V _reg ), and the smoothing coil is It becomes critical state at a charge current (I _z) current larger than the final stage, as in the last stage of the charging current (I _z) can output the maximum charge voltage (V _max) or of the voltage, the specification is determined It is characterized by being .
According to a second aspect of the present invention, in the charger according to the first aspect, the inductance (L) of the smoothing coil satisfies the following expression.
L ≦ T · V _reg (V _reg −D · V _max ) / 2V _max · I _z
L> 0
V _reg −D · V _max > 0
However,
L: Smoothing coil inductance T: Main switch switching cycle V _reg : Charge voltage regulation value D: Main switch duty (main switch on time / main switch switching cycle)
V _max : Maximum charging voltage I _z : Final stage charging current

As described above, according to the charger according to claim 1 of the present invention, in the charger which is constituted by the power factor improving unit and the DC voltage conversion unit and is charged by the multistage constant current charging method, the DC voltage conversion unit includes the main switch. A primary side circuit including a smoothing coil, and a transformer including a primary winding and a secondary winding interposed between the primary side circuit and the secondary side circuit. The transformer turns ratio (n ₁ : number of secondary windings / number of primary windings) is determined based on the charging voltage regulation value (V _reg ), and the smoothing coil is It becomes critical state at a charge current (I _z) current larger than the final stage, as in the last stage of the charging current (I _z) can output the maximum charge voltage (V _max) or of the voltage, the specification is determined So that the charging capacity is reduced Therefore, the number of windings of the secondary winding of the transformer can be reduced, whereby the transformer, the DC voltage converter, and thus the charger can be reduced in size. In addition, since the number of secondary windings of the transformer can be reduced, loss can be reduced and higher efficiency can be achieved.
According to a second aspect of the present invention, in the charger according to the first aspect, since the inductance (L) of the smoothing coil satisfies the following formula, the above effect is ensured. be able to.
L ≦ T · V _reg (V _reg −D · V _max ) / 2V _max · I _z
L> 0
V _reg −D · V _max > 0
However,
L: Smoothing coil inductance T: Main switch switching cycle V _reg : Charge voltage regulation value D: Main switch duty (main switch on time / main switch switching cycle)
V _max : Maximum charging voltage I _z : Final stage charging current

It is a figure which shows one embodiment of this invention, and is a block diagram which shows the relationship between AC power supply, a charger, and a storage battery. It is a figure which shows one embodiment of this invention, and is a circuit diagram which shows the structure of the DC voltage conversion part of a charger. FIG. 3 is a diagram showing an embodiment of the present invention, and shows the current of the smoothing coil of the secondary side circuit of the DC voltage converter of the charger and the timing of “on / off” and “turn on” of the main switch of the primary side circuit. FIG. It is a figure which shows one embodiment of this invention, and is a characteristic view which shows the relationship between the output current and output voltage of a charger. It is the figure used for description of a prior art example, and is a figure which shows the charging voltage and charging current of a multistage constant current charging system.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of a charging system using the charger 1 according to the present embodiment will be described with reference to FIG.
As shown in FIG. 1, the charger 1 is for charging the storage battery 5 with electric power from the AC power supply 3. The charger 1 includes a power factor improving unit 7 and a DC voltage converting unit 9.

  The power factor improving unit 7 is a circuit for reducing the harmonic component of the commercial AC power frequency of the input current from the AC power source 3 (a component having a frequency that is an integer multiple of the fundamental frequency) and improving the input power factor. is there.

As shown in FIG. 2, the DC voltage converter 9 includes a primary side circuit 11, a secondary side circuit 13, and a transformer 15 interposed between the primary side circuit 11 and the secondary side circuit 13. It is composed of The primary circuit 11 includes a power source 17 and a main switch 19.
Incidentally, showing the input voltage by drawing power 17 by symbol _{V in.}

  The secondary circuit 13 includes a rectifier diode 21, a commutation diode 23, a smoothing coil 25, a capacitor 27, and a resistor 29. The transformer 15 is composed of a primary winding 31 and a secondary winding 33.

The turn ratio n ₁ of the transformer 15 is designed using the charging voltage regulation value V _reg as a guide, and is calculated by the following equation (II).

V ₀ = V _reg = n ₁ · D · V _in ―― (II)

However,
V ₀ : Output voltage V _{reg of} charger ₁ : Charge voltage regulation value n ₁ : Turn ratio of transformer 15 capable of outputting charge voltage regulation value V _reg (number of turns of secondary winding 33 / turn of primary winding 31 Number of lines)
D: Duty of main switch 19 (ON time of main switch 19 / switching cycle of main switch 19)
V _in : Input voltage by the power supply 17

Even if the input voltage V _in by the power source 17, the turns ratio n ₁ of the transformer 15, and the duty D of the main switch 19 are constant, if the output current is made smaller than a certain current I _crit and the load resistance is increased, the output voltage will be It becomes higher than the charging voltage regulation value V _reg calculated by the formula (III).

I _crit = V _reg (n ₁ · V _in −V _reg ) · T / n ₁ · V _in · 2L
――― (III)
However,
I _crit : critical value of output current at which output voltage becomes V _reg or higher V _reg : charging voltage regulation value n ₁ : turn ratio of transformer 15 that can output charging voltage regulation value V _reg (number of windings of secondary winding 33 / Number of primary windings 31)
V _in : Input voltage L from the power source 17: Inductance T of the smoothing coil 25: Switching cycle of the main switch 19

In a critical state where the output current I ₀ is equal to the critical value I _crit of the output current, energy is stored in the smoothing coil 25 when the main switch 19 is “ON”. Released to load when “off”. When the main switch 19 is turned on, the current flowing through the smoothing coil 25 becomes “0” A. This is shown in FIG. FIG. 3 is a graph showing the time change with time (t) on the horizontal axis and the current of the smoothing coil 25 on the vertical axis.
The critical state means a state where the current flowing through the smoothing coil 25 becomes “0” A when the main switch 19 is turned on as shown in FIG.

Even if the output current I ₀ is attempted to be smaller than the critical value I _crit of the output current, the duty D of the main switch 19 is constant, so that when the main switch 19 is “ON”, the energy accumulated in the smoothing coil 25 is Does not decrease. Since all the stored energy is discharged to the load while the main switch 19 is “off”, the output voltage becomes higher than the charging voltage regulation value V _{reg of the} formula (II). In the case of the present embodiment, this operation is applied to the final stage of multistage constant current charging.

The output voltage when the output current I ₀ is less than or equal to the critical value I _crit of the output current is calculated by the following equation (IV).

V ₀ = V _dcm = V _reg ² / (D · V _reg + 2LI _o / T)
――― (IV)
However,
V ₀ : Output voltage V _dcm of the charger 1: Output voltage V _reg : Charge voltage regulation value D: Duty of the main switch 19 when the duty is constant and the output current I ₀ is below the critical value I _{crit of the} output current ( ON time of main switch 19 / switching cycle of main switch 19)
L: inductance I _o of the smoothing coil 25: switching period of the main switch 19: output current T of the DC voltage converter 9

Therefore, when the constant current value required for the final stage of multi-stage constant current charging is I _z and the maximum charging voltage is V _max , the output voltage V ₀ when the output current of the charger is I _z is the maximum charging voltage V _max. In other words, the following equation (V) may be satisfied.

V _max ≦ V _reg ² / (D · V _reg + 2LI _z / T)
――― (V)
However,
V _max : Maximum charging voltage V _reg : Charge voltage regulation value D: Duty of the main switch 19 (ON time of the main switch 19 / switching cycle of the main switch 19)
L: inductance I _z of the smoothing coil 25: final stage charging current T: switching period of the main switch 19

For example, if the charging voltage regulation value V _reg (determined from the input voltage V _in , the turn ratio n ₁ of the transformer 15 and the duty D of the main switch 19) and the switching cycle T of the main switch 19 are determined, the following equation (VI) , (VII), and (VIII) determine the inductance L of the smoothing coil 25.

L ≦ T · V _reg (V _reg −D · V _max ) / 2V _max · I _z
――― (VI)

L> 0 ――― (VII)

V _reg −D · V _max > 0 ――― (VIII)

However,
L: Inductance of smoothing coil 25: Switching period _{Vreg of} main switch 19: Regulating charging voltage D: Duty of main switch 19 (ON time of main switch 19 / switching period of main switch 19)
V _max : Maximum charging voltage I _z : Final stage charging current

An example of each numerical value is given as a specific example.

T
154 μS (f = 65 Hz)
D: 0.41
n ₁ : 0.18
V _in : 390V
V _reg : 28.8V
V _max : 35V
_Iz : 8A
V _reg −D · V _max : 144V> 0

Therefore,
L <: 14.4 μH
It becomes.

When L = 10 μH, the characteristics of the output voltage V ₀ with respect to the output current I ₀ of the charger 1 are as shown in FIG. FIG. 4 is a diagram showing the change between the output current I ₀ on the horizontal axis and the output voltage V ₀ on the vertical axis. As shown in FIG. 4, it is possible to output the maximum charge voltage V _max or voltage at the output current I _z multistage constant current last stage. Specifically, it is possible to output a voltage equal to or higher than the maximum charging voltage V _max (35V) with the output current I _z (8A) of the final stage of the multi-stage constant current.
In the case shown in FIG. 4, the critical state is reached only when the output current is 13A. That is, I _crit = 13A, and by setting the output current I _z to 8A smaller than that, it becomes possible to output a voltage equal to or higher than the maximum charging voltage V _max (35V).

As described above, according to the present embodiment, the following effects can be obtained.
First, the DC voltage conversion unit 9 and thus the charger 1 can be reduced in size and efficiency without reducing the charging capacity. That is, the turn ratio n ₁ of the transformer 15 according to the present embodiment is determined based on the charge voltage regulation value V _reg instead of the maximum charge voltage V _max , and therefore compared with the conventional turn ratio n _0. As a result, the number of windings of the secondary winding 33 of the transformer 15 is reduced.
Further, since the maximum charging current I _max does not change, the wire diameter of the secondary winding 33 is the same as the conventional one. Therefore, it is possible to reduce the size and cost of the transformer 15 as much as the number of windings is reduced.
As a specific example, as an example, the number of turns of the secondary winding 33 of the transformer 15 can be reduced by 19%.
At that time, since the inductance L of the smoothing coil 25 is set to a predetermined value, the output current I _z (8A) of the final stage of the multi-stage constant current outputs a voltage equal to or higher than the maximum charging voltage V _max (35V). The charging ability is guaranteed.
Further, the loss can be reduced by reducing the number of windings of the secondary winding 33 of the transformer 15.
Moreover, the reverse voltage of the rectifier diode 21 and the commutation diode 23 of the secondary circuit 11 can be lowered.
As a specific example, as an example, the reverse voltage of the rectifier diode 21 and the commutation diode 23 can be lowered by 19%.
Further, the charging capacity is not reduced at all.

The present invention is not limited to the one embodiment.
For example, the circuit configuration of the DC voltage converter 9 has been described by taking the forward type as an example, but is not limited thereto, and may be of the bridge type.
Further, in the case of the above-described embodiment, as an example of the multi-stage constant current charging method, the case of the first stage, the middle stage, and the last stage has been described as an example. However, the present invention is not limited to this. A case of four or more stages is also assumed.
In addition, the illustrated configuration is merely an example.

The present invention relates to a charger, and more particularly, to a battery that is charged by a multi-stage constant current charging method, and is devised so that it can be reduced in size and efficiency, for example, various electric vehicles and hybrid vehicles. It is suitable for the charger for charging the storage battery mounted in the etc.

DESCRIPTION OF SYMBOLS 1 Charger 3 AC power supply 5 Storage battery 7 Power factor improvement part 9 DC voltage conversion part 11 Primary side circuit 13 Secondary side circuit 19 Main switch 25 Smoothing coil

Claims (2)

In the charger that consists of a power factor improvement part and a DC voltage conversion part and charges by a multistage constant current charging method,
The DC voltage converter includes a primary circuit having a main switch, a secondary circuit having a smoothing coil, a primary winding and a secondary winding interposed between the primary circuit and the secondary circuit. It consists of a transformer that consists of wires,
The transformer turns ratio (n ₁ : number of secondary windings / number of primary windings) is determined with reference to the charging voltage regulation value (V _reg ),
The smooth coil, the charging current (I _z) current larger than the final stage becomes a critical state, the maximum charge voltage at the final stage of the charging current (I _z) (V _max) so that it can output a voltage equal to or higher than the specification A charger characterized in that is determined. The charger according to claim 1, wherein
A charger characterized in that the inductance (L) of the smoothing coil satisfies the following formula.
L ≦ T · V _reg (V _reg −D · V _max ) / 2V _max · I _z
L> 0
V _reg −D · V _max > 0
However,
L: inductance of the smoothing coil T: switching cycle of the main switch V _reg : charge voltage regulation value D before the final stage D: duty of the main switch (main switch ON time / main switch switching cycle)
V _max : Maximum charging voltage I _z : Final stage charging current

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