JP3274478B2 - Charging circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for a rechargeable battery such as a NiCd battery, and more particularly to a charging circuit for charging using a vehicle storage battery.

[0002]

2. Description of the Related Art FIG. 4 shows a primary current from a storage battery and a charging current from a charging circuit with respect to a voltage of the storage battery in a conventional charging circuit. FIG. FIG. 4B shows the relationship between the current and the voltage of the vehicle-mounted storage battery and the primary current.

Conventionally, in a vehicle storage battery, as shown in FIG. 4B, the current decreases as the voltage increases. The charging current is controlled so that the primary current has a margin with respect to the fuse rated current of the vehicle when the voltage of the vehicle-mounted storage battery is minimized. On the other hand, as shown in FIG. 4A, a predetermined level of charging current is supplied to the charging current in the circuit regardless of the voltage of the vehicle storage battery.

[0004]

Today, there is an increasing demand for charging in a moving vehicle, especially for quick charging. On the other hand, in a conventional charging circuit that is set so that the primary current of the vehicle-mounted storage battery is reduced in inverse proportion to the voltage,
For example, the charging circuit operates under the low-level primary current as it is despite the fact that the voltage of the vehicle-mounted storage battery is sufficiently high and the primary current is much lower than the fuse rated current and has sufficient margin. As a result, this has a problem that the demand for quick charging in a vehicle cannot be met.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a charging circuit capable of quick charging even when a vehicle-mounted storage battery is used.

[0006]

In order to achieve the above object, a charging circuit according to the present invention is supplied with power from a vehicle storage battery.
In a charging circuit for performing constant current charging, voltage detecting means for detecting the voltage of the vehicle-mounted storage battery, current value changing means for changing and changing the charging current value according to the detected voltage, and counting a charging time from the start of charging. Timer means for outputting a count value, arithmetic control means for weighting the count value according to the charge current value, integrating the count value to determine whether the battery has reached a set value, and determining whether the battery has reached a set value ; Check the temperature of
Means for calculating the temperature rise rate of the battery.
When the battery temperature rise rate reaches a predetermined level, it is determined that the battery is overcharged.
Means for shutting down the current value.
Is set according to the charging current value changed by the
It is configured to be.

[0007]

According to the present invention, the voltage of the on-vehicle storage battery is detected by the voltage detecting means, and when the detected voltage is low, the normal charging current value is set by the current value changing means. On the other hand, when the detected voltage is high, a larger charging current value is set, and rapid charging is performed.
Then, the count value obtained by counting the charging time from the start of charging is weighted according to the charging current value,
This is integrated to determine whether or not the battery has reached a set value, thereby determining whether the battery is fully charged. Further, the battery temperature is detected, and the battery temperature is detected.
The rate of temperature rise is calculated, and the rate of temperature rise of this battery is
Is reached, it is determined that the battery is overcharged. Here, the predetermined record
The bell is the charging current changed by the current value changing means.
A value corresponding to the value is set.

[0008]

FIG. 1 is a circuit block diagram showing one embodiment of a charging circuit according to the present invention.

The smoothing circuit 2 smoothes the input voltage from the vehicle storage battery 1 and outputs the same to the primary winding N1 of the transformer 3. The transformer 3 includes a primary winding N1 and a secondary winding N2, and a current flowing into the primary winding N1 is switched by turning on and off a switching element of the switching circuit 4, whereby a voltage is applied to the secondary winding N2. Is induced. The control circuit 5 outputs a switching signal for turning the switching circuit 4 on and off. 2 above
A rectifier circuit 6 and a smoothing circuit 7 are connected to the secondary winding N2 so that the power induced in the secondary winding N2 is rectified and smoothed and supplied to the battery 9.

The current detection circuit 8 is provided between the smoothing circuit 7 and the battery 9 and detects a charging current. The current detection circuit 8 converts the charging current into a voltage signal and inputs the voltage signal to an arithmetic control circuit 11 described later. The temperature sensor 10 detects the temperature of the battery 9 to prevent overcharging, and is converted into a voltage by the temperature detection circuit 12 and input to the arithmetic and control circuit 11. The timer circuit 13 counts the charging time from the start of charging, and counts the count value.
1 is input. Voltage detection circuit 14
Detects the output voltage of the on-vehicle storage battery 1, and the detected voltage is input to the arithmetic and control circuit 11.

The arithmetic control circuit 11 has the following functions.

First, upon receiving an input voltage signal from the current detection circuit 8, the duty of the switching pulse from the control circuit 5 is changed so that the charging current value becomes constant. Is turned on and off.

The arithmetic and control circuit 11 includes a voltage detection circuit 1
The charge current value is changed and switched based on the detection result of No. 4. 3A and 3B illustrate switching of the charging current value. FIG. 3A illustrates the relationship between the voltage of the vehicle-mounted storage battery and the charging current, and FIG. 3B illustrates the relationship between the voltage of the vehicle-mounted storage battery and the primary current. I have. As shown in FIG. 3A, the charging current value is switched between a normal level and a higher level at a predetermined value as a boundary in the output voltage of the vehicle-mounted storage battery. As shown in FIG. 3 (b), the primary current has increased as much as the charging current has been switched to the high level.

Further, the arithmetic control circuit 11 includes a timer circuit 1
The full charge control is performed based on the count value input from 3. At this time, the count value is weighted in accordance with the charging current value, and the count value is integrated to determine whether or not the charging current value has reached a set value regardless of the charging current value. .

The arithmetic and control circuit 11 includes a temperature detecting circuit 1
2 to calculate the temperature rise rate (ΔT) of the battery 9 based on the data from the temperature sensor 10 input through the control unit 2 to constantly determine whether or not the battery 9 is overcharged.
When T reaches a predetermined level, overcharging is determined and charging is terminated. The predetermined level takes into account that the temperature rise gradient varies depending on the charging current value,
A value corresponding to the charging current value is set.

Next, the operation of the charging circuit configured as described above will be described with reference to the flowchart of FIG.

First, the voltage detection circuit 14 determines whether or not the output voltage of the vehicle-mounted storage battery 1 is equal to or higher than a predetermined level. If the output voltage is equal to or higher than the predetermined level (YES in step S1), rapid charging with a large charging current value is started. At the same time (step S2), the count operation is started by the timer circuit 13 (step S3), and the process proceeds to step S4.

On the other hand, in step S1, if the voltage of the vehicle-mounted storage battery 1 is not equal to or higher than the predetermined level (NO in step S1), normal charging with a small charging current value is started (step S5), and the timer circuit 13 counts. Is started (step S6), and the process proceeds to step S4.

The count value input from the timer circuit 13 is weighted and integrated by the arithmetic control circuit 11 according to the charging current value (step S4). Next, it is determined whether or not the integrated value has reached a value at which charging is completed, and if charging is completed (YE in step S7)
S), the charging operation is terminated, and if the charging is not completed (NO in step S7), the process returns to step S1, and the above operation is repeated.

By weighting the count value in accordance with the charging current value in this way, even if the output voltage of the vehicle-mounted storage battery changes during charging and the content of the determination in step S1 changes, full charge control can be reliably performed. .

In this embodiment, the change of the charging current value is shown in two stages, but may be changed in more stages.

The timer may be capable of changing the speed of the counting operation in accordance with the weight coefficient.

[0023]

As described above, according to the present invention, the voltage of the in-vehicle storage battery is detected, and the charging current value is changed and switched according to the detected voltage. Can be rapidly charged. Further, by weighing the count value according to the charging current value, the full charge control can be reliably performed even if the output voltage of the vehicle-mounted storage battery changes during charging. Also, the battery temperature rise rate
When it is determined that the battery is overcharged when it reaches the
The bell corresponds to the charging current value changed by the current value changing means.
Temperature increases according to the charging current value.
It is possible to judge overcharge considering that the gradient is different.
it can.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a charging circuit according to the present invention.

FIG. 2 is a flowchart showing the operation of the charging circuit according to the present invention.

FIG. 3 is a diagram showing a primary current and a charging current from a storage battery with respect to a voltage of a vehicle storage battery in a charging circuit according to the present invention, and (a) shows a relationship between a voltage and a charging current of the vehicle storage battery;
(B) shows the relationship between the voltage of the vehicle-mounted storage battery and the primary current.

FIG. 4 is a diagram showing a primary current and a charging current from a storage battery with respect to a voltage of a vehicle storage battery in a conventional charging circuit;
(A) shows the relationship between the voltage of the onboard storage battery and the charging current, and (b)
Indicates the relationship between the voltage of the vehicle storage battery and the primary current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Onboard storage battery 2, 7 Smoothing circuit 3 Transformer 4 Switching circuit 5 Control circuit 6 Rectifier circuit 8 Current detection circuit 9 Battery 10 Temperature sensor 11 Operation control circuit 12 Temperature detection circuit 13 Timer circuit 14 Voltage detection circuit N1 Primary winding N2 2 Next winding

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36

Claims (1)

(57) [Claims] In a charging circuit which is supplied with power from a vehicle-mounted storage battery and performs constant current charging, voltage detection means for detecting a voltage of the vehicle-mounted storage battery, and current value changing means for changing and switching a charging current value according to the detected voltage. Timer means for counting the charging time from the start of charging and outputting a count value;
Performs weighting to the count value in response to the charging current value, and arithmetic control means for performing integration to full charge determination for whether or not reached the set value this hand for detecting the temperature of the battery
Steps, means for calculating the rate of temperature rise of the battery, and
When the temperature rise rate reaches a predetermined level, it is determined that the battery is overcharged.
And the predetermined level is provided to the current value changing means.
A charging circuit, wherein a value is set according to a charging current value that is further changed .