JP2001190031A - Battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an overvoltage which is generated by a resonance phenomena of a reactor and a capacitor (an LC filter) and applied to the capacitor, when a battery is not connected to a charger. SOLUTION: A charging current of a battery 5 and a current applied to a capacitor 4 are detected and fed back via an AC amplifier 807. A charging current command value VB* obtained by deducting a fed back current value from an output of a charging voltage command generator 802. This operation is equivalent to the process that an imaginary resistor is connected in series to a reactor 3. That is, by multiplying the detected current by a gain and deducting the multiplication result from a voltage command value, the operation is practiced as if a resistance exists, so that the AC amplifier 807 can be substituted equivalently by the imaginary resistor. When a battery is not connected to a charger, a resonance produced by the reactor 3 and the capacitor 4 (an LC filter) is suppressed by the imaginary resistor, by which the damping of the LC filter is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger, and more particularly, to suppressing the resonance of an LC filter of a battery and coping with abnormal charging voltage and charging current.

[0002]

2. Description of the Related Art FIG. 11 shows a conventional battery charger.
The charger is composed of a step-down chopper, 1 is a switching element, 2 is a diode, 3 is a reactor, 4 is a capacitor, 5 is a battery, 6 is a switch, 7 is a drive circuit for the switching element 1, and 11 is battery charging. Voltage V
B is a voltage sensor for detecting B, and 12 is a battery charging current IB
801 is a charging current command generator,
802 is a charge voltage command generator, 803 is a current control amplifier, 805 is a voltage control amplifier, 804 is a limiter that does not output a negative value, 806 is a PWM modulation circuit, 821 and 82
2, 823 are adder / subtracters.

Next, the operation will be described. On / off of the switching element 1 is determined by a gate command which is an output of the PWM modulation circuit 806. When the switching element 1 is turned on / off, a DC input voltage VD is generated at both ends of the diode 2 when the switching element 1 is on, and becomes 0 V when the switching element is off. This rectangular wave DC voltage is smoothed by the reactor 3 and the capacitor 4, and a DC voltage corresponding to the output of the PWM modulation circuit 806 can be obtained. When a DC voltage corresponding to the output of the PWM modulation circuit 806 is generated in the capacitor 4, the switch 6 is turned off and the battery 5 is charged.

[0004] The charging method of the battery 5 is generally such that at the start of charging, the battery is charged at a constant current because the internal impedance of the battery is low, and when energy is stored in the battery 5, switching to constant voltage charging is performed. It is. Therefore,
At the start of charging, an adder / subtractor 821 calculates a deviation between the output of the charging current command generator 801 that outputs a constant current charging command value and the battery charging current IB detected by the current sensor 12.
The current control amplifier 803 controls the difference between the output of the charge current command generator 801 and the battery charge current IB detected by the current sensor 12 to be zero, and the current control amplifier 80
3 is subtracted by an adder / subtractor 822 from the output of a charging voltage command generator 802 for outputting a constant voltage charging command value via a limiter 804, thereby making the charging current command generator 80
A charge voltage command VB * corresponding to the constant current charge command value, which is the output of 1, is generated.

Next, the difference between the output of the adder / subtractor 822 for outputting the charge voltage command VB * and the battery charge voltage VB detected by the voltage sensor 11 is obtained by addition / subtraction 823 so that this voltage difference becomes zero. Voltage controlled amplifier 805 and P
The WM modulation circuit 806 controls the switching of the switching element 1.

Next, energy is stored in the battery 5 and the battery charging current IB detected by the current sensor 12 is detected.
Is less than the output of the charging current command generator 801,
The current control amplifier 803 outputs a negative value, but since the negative value is cut by the limiter 804 and outputs zero, the constant voltage charging command value output from the charging voltage command generator 802 becomes the charging voltage command VB *. Is charged at a constant voltage.

A battery charger is disclosed in Japanese Patent Application Laid-Open No. Hei 9-112462, which is based on a combination of constant current control and constant voltage control to achieve the object of the present invention described below. It does not do.

[0008]

Since the conventional charger is configured as described above, when a battery is not connected to the charger, a resonance phenomenon occurs due to the reactor of the charger and the capacitor, and the capacitor is charged. There is a problem that an overvoltage is applied.

Further, the battery charge voltage VB does not change even if the charge voltage command value of the charge voltage command generator is varied in an attempt to adjust the battery charge voltage during constant current charging, but the command value is set higher than necessary. If the charging is performed, there is a danger that the constant voltage charging is performed at an abnormal voltage when switching from the constant current charging to the constant voltage charging.

In addition, an excessive current flows through the switching element 1 due to a short-circuit accident on the battery side or a short-circuit of the battery terminal of the charger, and an inrush current flows through the capacitor 4 when the charger starts. As a result, an excessive current flows through the switching element 1. In such a case, there is no protection circuit for protecting the switching element 1.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a charger which suppresses a resonance phenomenon caused by a reactor and a capacitor and does not apply an overvoltage to the capacitor. It is another object of the present invention to provide a charger that prevents charging with an abnormal voltage and prevents an excessive charging current from flowing to a switching element.

[0012]

(1) A battery charger according to the present invention detects and feeds back a charge voltage command value and a charge current command value for a battery and a charge voltage and a charge current of the battery. A gate command value is derived based on the value and a pulse width modulation control is performed based on the gate command value, and the battery charger includes a chopper-type control circuit that controls a charging voltage and a charging current of the battery. The feedback value of the charging current detection is a feedback value by detecting a current flowing through both the battery and the smoothing capacitor of the chopper-type control circuit, and includes a resonance preventing unit. The gate command value is changed according to the current value obtained when the battery is disconnected from the battery charger. The case, in which the means for preventing resonance by LC content including the smoothing capacitor of said chopper-type control circuit.

(2) In the above (1), the resonance preventing means includes: a filter that passes a current in a frequency band that resonates in L and C components including a smoothing capacitor of a chopper type control circuit out of the fed-back current; Means for changing the gate command value according to the current value passing through the filter.

(3) A gate command value is derived based on a charge voltage command value and a charge current command value for the battery and a feedback value obtained by detecting and feeding back the charge voltage and the charge current of the battery. A pulse width modulation control based on a command value, and in a battery charger including a chopper type control circuit for controlling a charging voltage and a charging current of the battery, the battery is charged based on the charging current command value. A means for preventing a change in the charging voltage command value is provided.

(4) A gate command value is derived based on a charge voltage command value and a charge current command value for the battery and a feedback value obtained by detecting and feeding back the charge voltage and the charge current of the battery. In a battery charger including a chopper-type control circuit that controls a charging voltage and a charging current of the battery by performing pulse width modulation control based on the value, the feedback value of the charging current detection is based on the battery and the chopper-type A current flowing through both the control capacitor and the smoothing capacitor is detected and used as a feedback value, and charging current limiting means is provided. The charging current limiting means detects the current value when the fed back current value exceeds a predetermined limiting value. Changing the gate command value according to the current value fed back to limit the charging current of the battery Battery charger, characterized in that it has a means that. It is what it was.

(5) In the above item (4), a limit value changing means for changing a limit value at the start of charging the battery is provided.

(6) In the above (1) or (2),
Means for preventing the change of the charging voltage command value in the above item (3);
Any one of the charging current limiting means of the above item (4) and the charging current limiting means and the limiting value changing means of the above item (5).
The means of paragraph or the means of paragraphs (3) and (4) above;
Alternatively, the above-mentioned means (3) and (4) are provided.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a circuit diagram of a battery charger according to Embodiment 1 of the present invention. In FIG. 1, functions corresponding to those in FIG. 11 described above are denoted by the same reference numerals, and detailed description thereof will be omitted. 807 is an AC amplifier, and 824 is an adder / subtractor. FIG. 2 shows an equivalent circuit in which the AC amplifier 807 of FIG. 1 is replaced by a virtual resistor circuit 807a.

Next, the operation of the above embodiment will be described with reference to FIGS.
(Mainly referring to FIG. 2). Here, the case where the battery 5 is not connected will be described. (1) The battery charging current IB (all charging and discharging currents of the capacitor 4) is detected by the current sensor 12, and (2) the output of the charging voltage command generator 802 via the virtual resistor circuit 807a (AC amplifier 807). Adder / subtractor 82
4 to obtain a charging voltage command VB *. (3) Charge voltage command VB * based on battery charge current IB
, The virtual resistor is connected in series with the reactor 3. (4) Therefore, the transfer function F (S) of the LC filter including the reactor 3 and the capacitor 4 is apparently F (S) = 1 / (LCS ² + RCS + 1) (1), and the damping coefficient ζ is ζ = (R / 2) × √ (C / L) (2) (5) From equation (2), the battery charging current I
If the charge voltage command VB * is not drooped by B,
Since R = 0, ζ = 0, and the resonance phenomenon does not stop, but the charging voltage command VB * based on the battery charging current IB
, Any R can be realized, so that ζ = 0.
A proportional coefficient R of 7 or more is selected, and the voltage controlled amplification 805 is selected.
, The damping of the LC filter can be improved.

That is, by multiplying the detected current value by a gain and subtracting it from the voltage command value, the operation is performed as if there is a resistor. Therefore, the AC amplifier 807 can be equivalently replaced with a virtual resistor. When the battery is not connected to the charger, the reactor 3 and the capacitor 4 (LC
The generation of resonance by the filter is improved by suppressing the resonance by improving the damping of the LC filter by the virtual resistor circuit.

As described above, resonance can be suppressed by the voltage control system, so that an overvoltage is not applied to the capacitor 4.

Embodiment 2 FIG. Next, FIG. 3 relates to Embodiment 2 of the present invention. In FIG. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. The difference from the first embodiment is that a band-pass filter 808 that allows only the resonance frequency band of the LC filter to pass is added, and the rest is the same as the first embodiment.

In FIG. 3, the battery charging current IB is
From the output of the charging voltage command generator 802 through an AC amplifier 807 (an equivalent virtual resistance circuit 807a shown in FIG. 2) through a bandpass filter 808 that is detected by the current sensor 12 and passes only the resonance frequency band of the LC filter. The result is subtracted from the adder / subtractor 824 to obtain a charging voltage command VB *. AC amplifier 807 (virtual resistance circuit 807a)
Is a circuit for improving damping from the viewpoint of the voltage control amplifier 805 of the LC filter as in the first embodiment. Since the bandpass filter 808 passes the component of the LC filter resonance frequency band as it is, the damping improvement operation has the same improvement effect as in the first embodiment. On the other hand, when the charger is charging the battery, the DC component of the signal input to the AC amplifier 807 (virtual resistance circuit 807a) is removed by the bandpass filter 808, so that the output of the virtual resistance circuit 807 is 0. Become.

With this configuration, when the battery is not connected, only the resonance frequency band of the LC filter viewed from the voltage control amplifier 805 has a virtual impedance connected in series with the reactor 3 and damping is performed. When the battery is improved and the battery is charged, the battery operates like a filter having low impedance characteristics, so that the battery voltage does not fluctuate depending on the amount of charging current.

Embodiment 3 Next, FIG. 4 relates to Embodiment 3 of the present invention. In FIG. 4, the same reference numerals are given to portions corresponding to FIG. 3, and detailed description thereof will be omitted. The difference from the second embodiment is that a comparator 809 is added, and the other points are the same as the second embodiment.

In FIG. 4, when the battery charging voltage VB is adjusted, the charging voltage command generator 80 is operated while the charger is operating.
2 can be varied. (1) Even if the output (charge voltage command value) of the charge voltage command generator 802 is varied to adjust the battery charge voltage VB during constant current charging, the battery charge voltage VB Does not change. (2) Further, once the output of the charging voltage command generator 802 is changed, it is difficult to find the original value. (3) If the output of the charging voltage command generator 802 is increased more than necessary, energy is stored in the battery during charging, and when switching from constant current charging to constant voltage charging, constant voltage charging with an abnormal voltage is performed. there's a possibility that.

In order to cope with the above (1) to (3), the output of the limiter 804 is monitored by the comparator 809 during constant current charging so that the battery charging voltage cannot be adjusted even if it is adjusted. If the output of the limiter 804 is positive, the constant current charging is in progress, and the comparator 80
The output signal of the charging voltage command generator 802 may not be changed by the output signal of No. 9.

With this configuration, the battery charging voltage VB cannot be adjusted during the constant current charging, so that the battery charging voltage VB can be surely adjusted.

Embodiment 4 Next, FIG. 5 relates to a fourth embodiment of the present invention. In FIG. 5, parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. The difference from the third embodiment is that a limiting circuit 813, an AC amplifier 814 (not shown, but equivalently replaced with a virtual resistor circuit), and an adder / subtractor 826 are added.
Others are the same as the third embodiment. FIG. 6 is a diagram showing input / output characteristics of the control circuit.

(1) In FIG. 5, charging voltage command VB *
The voltage control amplifier 805 and the PWM modulation circuit 806 control the switching of the switching element 1 so that the battery charge voltage VB detected by the voltage sensor 11 matches
A voltage control loop is configured. (2) The limiting circuit 813 sets the maximum charging current, and the battery charging current IB detected by the current sensor 12
If the value is equal to or less than the set value, the output of the limiting circuit 813 is zero. If the battery charging current IB is equal to or more than the set value, a value obtained by subtracting the set value from the battery charging current value is output from the limiting circuit 813. The battery charging current IB and the output of the limiting circuit 813 have characteristics as shown in FIG. 6, and the set value (IS) is set to a predetermined value.

(3) The output of the limiting circuit 813 is supplied to a charging voltage command VB via an AC amplifier (virtual resistance circuit) 814.
Is subtracted by the adder / subtractor 826 from the adder / subtractor 824 that outputs (4) For this reason, the battery charging current IB is
Above the set value, the charging voltage command VB * is drooped, and the battery charging voltage VB is drooped. Therefore, the battery charging current IB also decreases, and the switching element 1 is protected from overcurrent.

With such a configuration, the switching element 1 can be protected from an overcurrent due to a short-circuit accident on the load side in response to the voltage control.

Embodiment 5 FIG. Next, FIG. 7 relates to a fifth embodiment of the present invention. In FIG. 7, parts corresponding to those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. The difference from the fourth embodiment is that the PWM voltage command is changed by the battery charging current IB to form a virtual output resistor, and the other points are the same as the fourth embodiment.

In FIG. 7, a limiting circuit 813 sets a maximum charging current. If the battery charging current IB detected by the current sensor 12 is equal to or less than a set value, the limiting circuit 813
13 is zero, and when the battery charging current IB is equal to or greater than the set value, the limiting circuit 813 outputs a value obtained by subtracting the set value from the battery charging current value.

The output of the limiting circuit 813 is subtracted by the adder / subtractor 826 from the output of the voltage control amplifier 806 via an AC amplifier (virtual resistance circuit) 814. Therefore, when the battery charging current IB becomes equal to or more than the set value of the limiting circuit 813, the operation is performed so that the PWM voltage command value drops and the battery charging voltage VB drops, so that the battery charging current IB also decreases and the switching element 1 Are protected from overcurrent.

With such a configuration, the PWM
By the response of the modulation circuit 806, the switching element 1 can be protected from an overcurrent due to a short circuit accident on the load side.

Embodiment 6 FIG. Next, FIG. 8 relates to Embodiment 3 of the present invention. In FIG. 8, portions corresponding to FIG. 7 are denoted by the same reference numerals, and detailed description thereof will be omitted. The difference from the fifth embodiment is that a set value variable command circuit 815 that can change the set value of the limiting circuit 813 is added, and the rest is the same as the fifth embodiment. FIG. 9 is a diagram showing input / output characteristics of the control circuit.

In FIG. 8, when the charger starts, an inrush current flows through the capacitor 4. Therefore, the inrush current can be suppressed by gradually increasing the maximum charging current value set in the limiting circuit 813 from zero to the maximum charging current value by the set value variable instruction circuit 815.

FIG. 9A shows the relationship between the battery charging current IB and the output (IO) of the limiting circuit 813. At the start of charging, the set value (IS) is changed from zero to ISmax (maximum charging current value). Thus, the output (IO) of the limiting circuit 813 continuously changes from 1 to n. FIG.
FIG. 9B illustrates the change over time of the set value in FIG. 9A. For example, a straight line A and a straight line B are used. Is used.

With such a configuration, the inrush current when the charger starts can be suppressed.

Embodiment 7 FIG. In the third embodiment, the current sensor 12 detects the charging current to the battery 5 and the charging current to the capacitor 12 as shown in FIG. 4. However, in FIG. For example, an AC amplifier 807, a bandpass filter 808
May be omitted. Also in this case, during charging by the current control by the comparator 809, the command value of the charging voltage command generator 802 cannot be changed during charging by the current control, and when switching from the current control to the voltage control, the excessive charging voltage is used. Prevent the battery from being charged.

If there is no resonance phenomenon when the battery is not connected, the current sensor may detect only the charging current to the battery 5 as shown in FIG. Even in this case, the comparator 809 is used to prevent the battery from being charged with an excessive charging voltage as in the third embodiment.

Embodiment 8 FIG. In FIGS. 5, 7, and 8 of the fourth to sixth embodiments, the AC amplifier 807 and the band-pass filter 808 may be omitted if no resonance occurs when the battery is not connected. As in the case of the fourth to sixth embodiments, the switching element 1 is protected from overcurrent due to a short circuit accident on the load side.
And the inrush current when the charger starts can be suppressed.

[0044]

As described above, according to the present invention, when a battery is not connected to a charger, a resonance phenomenon caused by a reactor and a capacitor is suppressed, and when a battery is charged, an overvoltage is applied to the capacitor. Not to be
This has the effect of preventing charging with an abnormal voltage and preventing excessive charging current from flowing to the switching element.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a battery charger according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit in FIG. 1 replaced with a virtual resistor.

FIG. 3 is a circuit diagram of a battery charger according to Embodiment 2 of the present invention.

FIG. 4 is a circuit diagram of a battery charger according to Embodiment 3 of the present invention.

FIG. 5 is a circuit diagram of a battery charger according to Embodiment 4 of the present invention.

FIG. 6 is a diagram showing input / output characteristics of a limiting circuit according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram of a battery charger according to Embodiment 5 of the present invention.

FIG. 8 is a circuit diagram of a battery charger according to Embodiment 6 of the present invention.

FIG. 9 is a diagram showing input / output characteristics of a limiting circuit according to a sixth embodiment of the present invention.

FIG. 10 is a circuit diagram of a battery charger according to Embodiment 7 of the present invention.

FIG. 11 is a circuit diagram of a conventional battery charger.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 switching element 2 diode 3 reactor 4 capacitor 5 battery 6 switch 7 drive circuit 11 voltage sensor 12 current sensor 801 charging current command generator 802 charging voltage command generator 803 current control amplifier 805 voltage control amplifier 804 limiter 806 PWM modulation circuit 807 AC Amplifier 807a Virtual resistor circuit 808 Bandpass filter 809 Comparator 813 Limiting circuit 814 AC amplifier 815 Set value variable command circuit 821, 822, 823, 826 Adder / subtractor

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5G003 AA01 BA01 CA03 CC02 GA01 GB03 5H030 AA03 AA06 AS18 BB01 FF42 FF43 5H730 AA20 AS01 AS02 AS17 BB13 BB57 DD03 FD01 FD31 FG05 XC09 XX03 XX15 XX23 XX35 XX47

Claims (6)

[Claims] A gate command value is derived based on a charging voltage command value and a charging current command value for a battery and a feedback value obtained by detecting and feeding back the charging voltage and charging current of the battery. In a battery charger including a chopper-type control circuit that controls a charging voltage and a charging current of the battery by performing pulse width modulation control based on the feedback value of the charging current detection, the battery and the chopper-type control circuit The current flowing through both the smoothing capacitor is detected and used as a feedback value, and resonance prevention means is provided. The resonance prevention means changes the gate command value according to the fed back current value, and the battery Including the smoothing capacitor of the chopper control circuit when not connected to the battery charger A battery charger comprising means for preventing resonance due to LC components. 2. The battery charger according to claim 1, wherein the resonance preventing means includes:
Resonance preventing means having a filter for passing a current in a frequency band resonating in L and C components including a smoothing capacitor of a chopper type control circuit, and means for changing a gate command value according to a current value passing through the filter; A battery charger comprising: 3. A gate command value is derived based on a charge voltage command value and a charge current command value for the battery and a feedback value obtained by detecting and feeding back the charge voltage and the charge current of the battery. When the battery is charged based on the charging current command value in a battery charger including a chopper-type control circuit that performs pulse width modulation control based on the charging current command value and controls the charging voltage and charging current of the battery. And a means for preventing a change in the charging voltage command value. 4. A gate command value is derived based on a charge voltage command value and a charge current command value for the battery and a feedback value obtained by detecting and feeding back the charge voltage and the charge current of the battery, and based on the gate command value. In a battery charger including a chopper-type control circuit that controls pulse voltage modulation and a charging voltage and a charging current of the battery, a feedback value of the charging current detection is based on the battery and the chopper-type control circuit. A current flowing through both the smoothing capacitor is detected and used as a feedback value, and charging current limiting means is provided. When the feedback current value exceeds a predetermined limit value, the charging current limiting means detects the feedback current. Means for limiting the charging current of the battery by changing the gate command value according to the value. A battery charger characterized in that: 5. The battery charger according to claim 4, further comprising limit value changing means for changing a limit value when charging of the battery is started. 6. The battery charger according to claim 1 or 2, wherein a means for preventing a change in the charging voltage command value according to claim 3, a charging current limiting means according to claim 4, and a charging current according to claim 5. A battery charger provided with any one of the limiting means and the limit value varying means, the means of claim 3 and claim 4, or the means of claim 3 and claim 5. .