JPH02188135A - Charging controller - Google Patents

Abstract

PURPOSE:To obtain a one-chip control circuit by subjecting battery voltage to frequency conversion then digitizing the converted value and comparing the digitized value thus performing charging control. CONSTITUTION:Battery voltage is converted through a voltage-frequency converter 1 into frequency which is then counted through a counter 2 and converted into a digital value. Digitized data are stored in a latch 4 and compared, three times through a comparator 7, with data stored in a maximum value memory section 6, then a new maximum value is stored in the maximum value memory section 6. Count in the counter 2 is also stored in another latch 5 then the difference between the value in the latch 5 and the value stored in the maximum memory section 6 is obtained through a comparator 2. A charge stop command is provided through an output control section 13 upon detection of the battery voltage lower than the maximum value by a predetermined amount. A charge stop output is provided forcibly, based on an output from a timer 10, upon elapse of 90min. after start of charging operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a charging device for charging a secondary battery such as a nickel-cadmium battery in a short period of time, and relates to charging current control means therefor.

(b) Conventional technology A conventional charging control device is, for example,
Comparing the output voltage of a voltage detection device that detects the battery voltage with the storage voltage of the storage unit as in the publication, and increasing the storage voltage to the output voltage only when the output voltage is higher than the storage voltage, The circuit is configured so that the storage voltage maintains the highest value of the output voltage even if the output voltage decreases, and when the output voltage decreases by a certain voltage or more from the storage voltage, the charging current is controlled or charging is terminated. It is. In this example, the electric circuit section that compares the battery voltage and memory voltage is constructed in an analog manner, making it difficult to sort out the electrical components that make up this section, and requiring an adjustment process for these components. However, it was difficult to improve detection accuracy when fully charged.

Furthermore, when attempting to digitally compare the battery voltage and the storage voltage using a microcomputer, there is a problem in that the circuit system becomes large and a large number of attached electric circuit parts are required.

(c) Problems to be solved by the invention The problem to be solved by the invention is to assemble a digital full charge detection circuit using a one-chip IC (integrated) circuit.
The purpose is to control the charging current to the battery based on the output of this detection circuit.

(d) Means for solving the problem - A voltage-frequency converter that inputs the terminal voltage of the secondary battery connected to the charging circuit and converts it into a corresponding frequency, and a digital converter that counts the frequency corresponding to the terminal voltage. a counter that converts the frequency into a value, a comparator that compares the digital value obtained by converting the frequency corresponding to the maximum voltage of the battery being charged with the digital value corresponding to the terminal voltage, and an output control signal from the comparator. and an output control section that controls the current flowing through the charging circuit.

(e) Perform voltage-frequency conversion using the working battery voltage or its partial voltage as an input signal, measure the resulting frequency with a counter, and convert the battery voltage into a digital value. This digital value is compared with a digital maximum value starting from 0, and if the input value is larger several times, that input value is replaced as the digital maximum value, and this operation is repeated thereafter. The peak voltage of the battery voltage of its charging characteristics is recorded, and it is determined from a comparison between the previous input value and the digital maximum value that the battery voltage has dropped by a predetermined value, and an output control signal is issued to control the charging current.

(F) Embodiment Below, the charging control device of the present invention will be described in detail with reference to an embodiment of the drawings.

Figure 2 shows an example of a transformer-type charging circuit. In the figure, (T1) allows its secondary coil (Ll) to be connected to a commercial AC power supply, and supplies a step-down current to the secondary coil (B2) side. (Di) (B2) is a full-wave rectifier whose anode side is connected to both ends of the secondary coil (B2) and whose cathodes are connected together; (Ql) is its emitter-collector circuit; a switching transistor (B) connected to the cathode side of the rectifier (Di) (B2);
1) consists of three Ni-Cd batteries connected in series, the positive electrode of which is connected to the collector side of the switching transistor (Ql), and the negative electrode of which is connected to the center tap of the secondary coil (B2). The battery (ICI) has a diode (B3) between one end of the secondary coil (B2) and the intermediate tap.
), a charging control circuit consisting of a one-chip IC connected to a power input terminal (Vcc-), (C2) is an intermediate tap between the base of the switching transistor (Ql) and the secondary coil (B2). and its emitter between
This is an auxiliary transistor formed by inserting a collector circuit.

A current limiting resistor (R1) is connected between the emitter and the collector of the switching transistor (Ql) for supplying a minute current to the secondary battery (B1) when the transistor (Ql') is not conductive. , a base resistor (R2) is connected between its emitter and base.

A base resistor (R4) is connected between the collector and the base of the auxiliary transistor (C2), and the output terminal (OUT) of the charge control circuit (ICI) is connected to the base of this transistor (C2). .

The positive electrode of the battery (B1) is connected to the charging control circuit (ICI)
A charging control circuit (
A smoothing capacitor is connected in parallel with the charging control circuit (ICI) to stabilize the power input, and a Zener diode (ZDi) is connected across the smoothing capacitor (C1).

Next, FIG. 1 shows a circuit diagram showing the contents of the charging control circuit (ICI) in blocks. In the figure, the charging control circuit (IC
I) is the voltage-frequency (V-F
) conversion unit (for example, voltage controlled oscillator: VCO) (1), a 13-bit counter (2) that counts the output of the conversion unit (1), and two 13-bit latches (2) with a memory function using a timing circuit (3). 4)(5), 13-bit max that stores the maximum frequency value at any time, data storage section (6), data of one latch (4) and m a
'x.

The data of the first latch (7) is compared three times with the data of the data storage unit (6), and the data of the other latch (5) is max.
, a second comparator (8) that compares the data with the data in the data storage section (6), a 3-minute timer section (9) and a 90-minute timer section (10) that operate based on the output of the conversion section (1), and the power supply. Both timer sections (9) are connected to the input terminal (Vcc).
(10) and max, a clear circuit (11) for initializing the data storage section (6), connected to the power input terminal (Vcc), and connected to the 3-minute timer section (9) and the 90-minute timer section (
a start circuit (12) for starting the operation of lO);
Based on the outputs from the second comparator (8), the clear circuit (11) and the 90 minute timer (lO), the output terminal (OUT)
and an output control section (13) that outputs a predetermined output.

The fourth part shows the charging characteristics of the battery (B1), and shows the charging characteristics of the battery (B1).
) and the voltage of the charging control circuit (IC1) -
At time 0 Tp, which draws the same characteristic curve as the frequency f converted by the frequency converter (1), the voltage ■ or the frequency f
It is common practice to record the maximum value and then control so that the current ■ is switched to a minute current at a time point Ts when the current decreases by a predetermined value (.DELTA.V, .DELTA.f).

In the embodiment shown in Fig. 1.2 above, when the commercial power supply is connected to the secondary coil (Ll) of the step-down transformer (T1), the power supply input terminal ( Power is applied to Vcc). Then, the clear circuit (11) operates and the data storage section (6)
, 3 minute timer (9).

The 90-minute timer (1G) and the output control section (13) are in the initial state, and then the start circuit (12) is activated. As a result, both timers (9) and (10) start operating, and the 3-minute timer (9) sets the 13-bit counter (2) to the initial state to prevent instability in the terminal voltage of the battery (B1) at the initial stage of charging. to put it in a non-operating state, and then force a quick charge for 3 minutes. Immediately after starting this charging, the charging control circuit (ICI)
In order to output the output terminal (OUT) i of trHIGHJ level and make the auxiliary transistor (Q2) conductive,
The switching transistor (Ql) becomes conductive and a large current flows into the battery (Bl).

When 3 minutes have passed from the start of charging, the voltage-frequency converter (1), which takes in the terminal voltage of the battery (B1) to the input terminal (IN) of the charge control circuit (ICI) via the resistor (R3), is removed. Convert the input voltage to frequency and then convert this to 13b
The IT counter (2) counts for a certain period of time, and the battery (B
The digital value corresponds to the terminal voltage of 1).

13bitmax, data storage section (6) (initial value is 0)
is compared three times in the first comparator (7) with the digital value previously stored in the 1/3-bit latch (4), and the digital value is larger than the value in the data storage unit (6) (count number). (person), the digital value is rewritten as max data. Then, the new max data in the data storage section (6) and the value of the counter (2) are compared in the second comparator (8) via the other 13-bit latch (5), and the value of the counter (2) is max, when the data decreases by a predetermined value, the output to the output control section (13) is inverted and the output terminal (OU
The output of T) is inverted from rHIGH to rLOWJ.

In other words, according to the charging characteristics shown in Fig. 4, from the start of charging until the terminal voltage of the battery (B1) reaches its peak value, the count data in the data storage section (6) increases intermittently until it exceeds the peak value. While this maX data is stored, the value of the counter (2) decreases after the peak value, and when it decreases by a predetermined value, the output of the charging control circuit (ICI) is inverted.

In this way, the auxiliary transistor (Q2) becomes non-conductive, the switching transistor (Ql) also becomes non-conductive, and rapid charging ends, and a minute current passes through the resistor (R1) and the battery (
B1).

If rapid charging does not stop even after 90 minutes have passed from the start of charging, the battery (B1) will be overcharged, causing damage to the battery (B1) due to an increase in internal temperature. In preparation for the first situation, the output of the charging control circuit (ICI) is forcibly inverted after 90 minutes, and the switching transistor (Ql) is made non-conductive.
It is equipped with a 0 minute timer (10).

Figure 3 shows an embodiment of an inverter type charging circuit, including a full-wave rectifier (B4), a primary coil (Ll) connected to one end of the rectifier (B4), a secondary coil (R2), and a rectifier (B4).
), an inverter transformer (T2) having a feedback coil (B3) connected to the other end; and an oscillation transistor (T2) having a collector-emitter circuit connected to the secondary coil (Ll).
C3), the base resistance (R5) of the transistor (C3)
, a spike voltage absorbing capacitor (C3) inserted between both ends of the secondary coil (Ll), and the feedback coil (B
3) and the capacitor (C2) connected between the rectifier (B4)
) and a resistor (R9), a control transistor (C4) connected to the base of the transistor (C3), a diode (B5) connected to the secondary coil (B2), and a resistor (R9) connected to the base of the transistor (C4). resistance (R8)
An inverter circuit (INV) is configured by connecting a battery (B2) consisting of two Ni-Cd batteries in series between both ends of the secondary coil (B2), and a battery (B2) consisting of two Ni-Cd batteries connected in series.
A charging control circuit (ICI), a Zener diode (ZD2), and a capacitor (C4) are connected in parallel between the re-output terminals of the battery (B2) via a resistor (R6), and the positive electrode of the battery (B2) is is connected to the input terminal (IN) of the charging control circuit (ICI) through a resistor (R7), and the output terminal (OUT) of the charging control circuit <ICI is connected to the transistor (C4) through a resistor (R8). It is connected to the base.

In this example, as in the embodiment shown in Figure 1, the output of the inverter circuit (INV) is as follows: Immediately after charging starts, a large current is induced into the secondary coil (B2), and the battery (B2) is first rapidly charged for 3 minutes. , until the terminal voltage of the battery (B2) passes through the peak value and decreases by a predetermined value, the max in the state converted to frequency is compared with the data storage value, and when the terminal voltage decreases by the predetermined value, the charging control circuit (ICI) ) output (OlJT) is inverted,
The current transferred to the feedback coil (B3) is transferred to the transistor (
By passing through C4), the base current of the oscillation transistor (Ql) is reduced, and the current supplied to the battery (B2) becomes a minute current.

(G) Effects of the Invention As described above, the present invention includes a voltage-frequency conversion unit that inputs the terminal voltage of a secondary battery connected to a charging circuit and converts it into a corresponding frequency, and a counter that counts and converts it into a digital value; a comparator that compares the digital value obtained by converting the frequency corresponding to the maximum voltage of the battery being charged with the digital value corresponding to the terminal voltage; and the comparator. Since the charging control device includes an output control section that controls the current flowing through the charging circuit based on an output control signal from the charging circuit, the device can be easily made into a one-chip IC as a part of the charging circuit. In addition, since the processing is done digitally, it is expected that there will be no need to take into account variations in parts.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram showing a charging control device of the present invention, Fig. 2 is an implementation circuit diagram of a step-down transformer type charging device using the charging control device of Fig. 1, and Fig. 3 is a block circuit diagram showing the charging control device of the present invention. FIG. 4 is a circuit diagram of an inverter type charging device using the charging control device of the present invention, and FIG. 4 is a diagram showing the charging characteristics of the battery. (Bl) (B2)... Secondary battery, (1)... Voltage -
Frequency conversion unit, (2)...Counter, (8)...Comparator, (13)...Output control unit.

Claims (1)

[Claims] (1) A voltage-frequency converter that inputs the terminal voltage of the secondary battery connected to the charging circuit and converts it into a corresponding frequency, a counter that counts the frequency corresponding to the terminal voltage and converts it into a digital value, and a charging circuit. a comparator that compares a digital value obtained by converting a frequency corresponding to the maximum voltage of the battery therein with a digital value corresponding to the terminal voltage, and a current flowing through the charging circuit based on an output control signal from the comparator. A charging control device consisting of an output control section for controlling.