JP2584832B2 - Charger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charger provided with a plurality of charged state detecting means for detecting that a charged state of a secondary battery has reached a predetermined state.

[Prior Art] FIG. 5 shows a conventional charger. This charger includes an inverter 1 composed of a switching element Q ₄ , an oscillation transformer T, and a control circuit 2. The inverter 1 converts an output obtained by rectifying and smoothing a commercial power supply AC into high-frequency power, and uses the output of the inverter 1. The output winding L ₃ of an oscillation transformer T
Is rectified and smoothed by the diodes D ₂ and D ₃ and the choke coil Lc, and the secondary battery B is charged with the rectified and smoothed DC voltage. The inverter 1 is a separately-excited type, and the IC shown in FIG.
(TL494) PWM by the control circuit 2 configured using 5
(Pulse width modulation) is controlled. In this charger, 2
Detects the charging current by the next battery B and the resistance R ₅ for connecting charging current detection in series, and a charging current control circuit 3 for feeding back a control signal corresponding to the charging current control circuit 2. The control circuit 2 in response to the control signal maintains a constant charging current by controlling the on-duty of turning on the switching element Q _4. The charging current control circuit 3 has a function of detecting the battery voltage and the battery temperature of the secondary battery B to prevent the secondary battery B from being overcharged. That is, secondary to the battery voltage detection circuit 18, shown in FIG. (B) the battery voltage of the secondary battery B as shown in FIG. 7 (a) it is detected that has risen to a predetermined voltages V ₁ or more battery temperature of the battery B is a battery temperature detecting circuit 17 for detecting that exceeds the predetermined temperature T _1, and feeds back the detection outputs of the charging state detection means to the control circuit 2. Based on the control signal the feedback control circuit 2 is to minimize the on-duty of the switching element Q _4, 7
As shown in FIG. 4D, the charging current of the secondary battery B is reduced. In this charger, the output of the charging current control circuit 3 is fed back to the IC 5 of the control circuit 2 via the photocoupler PC, and the power supply side and the battery side are connected between the photocoupler PC and the oscillation transformer T of the inverter 1. Insulated.

However, in the case of such a charger having a plurality of state-of-charge detecting means, the photocoupler shown by the solid line and the broken line in FIG. The current flowing through the light emitting diode LD of the PC is different, so that the light emission intensity of the light emitting diode LD varies due to the respective charge state detecting means, and the current flowing through the phototransistor PT on the output side also changes. As a result, the charging current values based on the outputs of the respective charging state detecting means differ as shown by the solid line and the broken line in FIG.
There was a problem that stable charge control could not be performed. The solid line in FIG. 7 indicates that the battery voltage of the secondary battery B is equal to the predetermined voltage V _1.
Indicate a case where rises above, also dashed battery temperature of the secondary battery B is indicative of the case exceeds a predetermined temperature T _1.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and an object of the present invention is to provide a charger capable of performing stable charging control.

Means for Solving the Problems To achieve the above object, the present invention detects a charging current and outputs a control signal having a signal amount corresponding to the magnitude of the charging current to a control circuit of an inverter. A control circuit for detecting a state of charge of the secondary battery, inputting the detection signal to the charge current control circuit, and outputting a control signal for minimizing the charge current when the state of charge reaches a predetermined state; The charge current control circuit is provided with a plurality of charge state detection means for outputting through the control circuit, and feedback amount control means for making the control signal output from the charge current control circuit constant by the charge state detection means.

(Operation) The present invention is configured as described above, so that the control signal from the charge state detection means, which is fed back to the control circuit of the inverter by the feedback amount control means, is constant, and the charge state detection means determines the predetermined charge state. When a is detected, a constant charging current is supplied to the secondary battery without any variation, so that stable charging control can be performed.

(Embodiment) FIGS. 1 and 2 show an embodiment of the present invention. In addition,
This embodiment has the same configuration as that of the conventional example shown in FIGS. 5 and 6 except for a part of the configuration of the charging current control circuit 3. Therefore, the entire configuration will be described with reference to FIGS. 5 and 6. This will be described with reference to FIG. This charger connects AC power supply AC to input terminals a and b,
The secondary battery B is used by connecting to the output terminals c and d. Inverter 1 of the charger, oscillation transformer T, is composed of a switching element Q ₄ and the control circuit 2, an input terminal
a, together with the connected AC power source AC to b to rectified by diode bridge DB, and converts a smoothing the rectified smoothed output by the smoothing capacitor C ₁₂ to the high frequency power, the oscillation transformer T, which is the output of the inverter 1 are then supplied to the charging current of the high frequency voltage induced in the output winding L ₃ to the diode D _2, D ₃ and rectifying and smoothing a secondary battery B in the choke coil Lc. The switching element Q ₄ Yes using transistors, the primary winding L ₁ of the oscillating transformer T in series with the switching element Q ₄ is is connected. The oscillation transformer T supplies in addition to the primary winding L ₁ and the output winding L _3, a reset winding L ₂ of the diode D ₁ is connected across the power supply to the charging current control circuit 3 to be described later and a winding L ₄ for. A constant voltage circuit 4 composed of a transistor Q ₁ , a zener diode ZD ₁ , resistors R ₁ and R ₂ , and a capacitor C ₁₁ connected to the output of the diode bridge DB converts the output of the diode bridge DB into a constant voltage and sends it to the control circuit 2. Supply. The control circuit 2 includes a control IC 5, control transistors Q ₂ and Q ₃ for controlling conduction of the switching element Q ₄ according to an output of the IC 5, an external resistor R _T , R ₈ , R ₉ and a capacitor C _{T of the} IC 5.
When, it is constituted by a phototransistor PT and a series circuit of a resistor R ₇ of the photocoupler PC as an input circuit for receiving the output of the charging current control circuit 3.

As shown in FIG. 6, IC5 includes an oscillator 6 for generating a sawtooth wave having a frequency determined by an external resistor R _T and a capacitor C _T , two error amplifiers 7, 8, and outputs of the error amplifiers 7, 8 A comparator 9 for generating a signal for PWM control by comparing the output of the comparator 6 with an output of the oscillator 6, a comparator 10 used for providing a dead time, and comparators 9, 10
An OR gate 11 that takes the OR of the OR gate 11, a flip-flop 12 that is set according to the output of the OR gate 11, a NOR gate 13, 14 that takes the NOR of the output of the OR gate 11 and the flip-flop 12, or an inverted output, and an output of the NOR gate 13, 14 The output transistors 15 and 16 are controlled. The IC5 can also be used to alternately turn on and off a plurality of switching elements such as a so-called half-bridge or full-bridge type inverter. For this reason, the error amplifier 8 and the dead time Although a comparator 10, a NOR gate 14, and an output transistor 16 are provided, the circuit is not used in the present embodiment. In the control circuit 2, be connected to one input and the charging current control circuit 3 of IC5 by photo coupler PC, the voltage across the resistor R ₇ is changed by the conduction state of the phototransistor PT of the photocoupler PC, the voltage across the error It is input to the non-inverting input of the amplifier 7. Note that the error amplifier 7 functions to control the ON period of the output transistor 15, and the on-duty of the output pulse is maximized when the output of the error amplifier 7 is minimum.

Next, a description will be given of a charging current control circuit 3 which detects a charging current flowing through the secondary battery B and feeds back a control signal corresponding to the charging current to the control circuit 2 of the inverter 1. The configuration of the charging current control circuit 3 for stabilizing the charging current is the same as that of the conventional example, and is changed to a resistor for detecting the charging current flowing through the secondary battery B as shown in FIG.
R ₅ , an operational amplifier OP ₁ , a volume VR, a light emitting diode LD of a photocoupler PC, and resistors R ₃ and R ₆ . The power source of the charging current control circuit 3 is an oscillation transformer T
And a voltage induced in the winding L ₄ a diode D ₄ and a capacitor C ₀₁ obtained by rectifying and smoothing. That is, the voltage across the resistor R ₅ generated in accordance with the charge current is amplified by the operational amplifier OP _1, the emission intensity of the light emitting diode LD of the photocoupler PC with the output of the operational amplifier OP ₁ to the variable, the control circuit 2 IC
5 and controls the on-duty of turning on the switching element Q ₄ keep the charging current constant, for example, those in which the charge current fluctuation of power supply voltage so as not to vary. Incidentally, the volume VR is provided in order to set the charging current to a predetermined value by adjusting the gain of the operational amplifier OP _1.

The operation of the charger having the above configuration will be briefly described.
When due supply voltage variation of the charging current of the secondary battery B is increased, the voltage across the resistor R ₅ is increased, also increases the output of the operational amplifier OP _1. For this reason, the light emission intensity of the light emitting diode LD of the photocoupler PC increases, and the input signal of the IC 5 also increases. Therefore, the control circuit 2 to reduce the on-duty of the switching element Q _4, the output voltage drops inverter 1, an increase of the charging current is suppressed. Further, when the charging current becomes small, decreases the voltage across the resistor R ₅ is, the output of the operational amplifier OP ₁ is lowered, the switching element Q
By controlling the on-duty of ₄ to be large, a decrease in the charging current is suppressed. Thus, the charging current of the secondary battery B is kept constant.

Hereinafter, the configuration of the charging current control circuit 3 which is a feature of the present embodiment will be described. In this embodiment, the secondary battery B is also used.
Zener diode ZD ₂ and the battery voltage detecting circuit 18 is a series circuit of a resistor R _4, a battery temperature detection circuit 17 for detecting a battery temperature of the secondary battery B voltage across detects that equal to or greater than a predetermined voltage To prevent the secondary battery B from being overcharged by these charged state detecting means.
The present embodiment is different from the conventional example in that a feedback amount control unit 19 for keeping a control signal fed back to the control circuit 2 by the charge state detection units 17 and 18 constant is provided. 19 comprises a resistor R _A and a plurality of transistors Q _A , Q _B ,. That is, a plurality of transistors Q _A , Q _B ,... Are connected in parallel, and the transistors Q _A , Q _{B ,.}
Power supply for the charging current control circuit 3 and the operational amplifier OP
Connected to the output of ₁ . Then, the battery voltage detection circuit 18, and the base of the transistor Q _A, as well as connection between the positive electrode of the secondary voltage B, and the output of the battery temperature detecting circuit 17, are input to the base of the transistor Q _B.

Now, the secondary battery B is charged, the base current battery voltage of the secondary battery B may rises above the Zener voltage of the Zener diode ZD _2, via a resistor R ₃ and the Zener diode ZD ₂ to the transistor Q _A flows, the transistor Q _a is turned on, current flows through the light emitting diode LD of the photocoupler PC via a resistor R _a. Emission intensity of the light emitting diode LD by the current at this time, since the on-duty of the switching element Q ₄ by the control circuit 2 is set to the intensity to minimize secondary battery B is trickle charged. Therefore, the secondary battery B is not overcharged, and the deterioration of the secondary battery B is prevented. Further, when the battery temperature of the secondary battery B with a battery temperature detection circuit 17 rises above a predetermined temperature is detected, by turning on the transistor Q _B, the same current as in the above flows through the light emitting diode LD, Similarly, secondary battery B
To prevent overcharging. Incidentally, in the case of conventional, a battery voltage detection circuit 18 directly connected between the positive electrode and the output of the operational amplifier OP ₁ secondary voltage B, also receives the output of the battery temperature detecting circuit 17 to the operational amplifier OP ₁ Te had current flows to the light emitting diode LD as the on-duty of the switching element Q ₄ is minimized. For this reason, the current flowing through the light emitting diode LD of the photocoupler PC differs due to variations in resistance and variations in the output of the battery temperature detection circuit 17, and the like.
The value of the charging current flowing to the secondary battery B when the completion of charging or the like is detected by the battery voltage detecting circuit 18 and the battery temperature detecting circuit 17 is different, and therefore, stable charging control cannot be performed. However, in the case of the present embodiment, the respective detection circuits 17, 1
Turn on the transistors Q _A and Q _B with the output of 8, and set the same resistance R _A
When the charging state of the secondary battery B is detected by the two detection circuits 17 and 18, the same current is supplied to the light emitting diode LD as shown in FIG. 2 (c). Can flow to LD. Therefore, any detection circuit
Fig. 2 (d) even if the completion of charging is detected at 17,18
As shown in (1), a constant charging current can be supplied to the secondary battery B, and stable charging control can be performed.

By the way, in the above-mentioned embodiment, the current flowing through the light emitting diode LD is made constant by the transistors Q _A and Q _B and the resistor _RA . However, as shown in FIG. 3, instead of the parallel circuit of the transistors Q _A and Q _B , in using the gate OR _1, OR ₂ taking OR of each of the detection circuits 17 and 18 may be an output of the OR gate OR ₂ in the transistor Q _a. Also, the fourth
As shown in the figure, a constant current diode D _A is connected in series to a series circuit of a resistor R _A and a transistor Q _A, and both detection circuits 17 and 1 are connected.
The output of the 8 directly may be input to the base of the transistor Q _A. In the above-described circuit, the number of transistors, OR gates, and the like are extraly shown because two or more control modes are considered. Also,
As the charged state detecting means for detecting the charged state of the secondary battery B, the battery voltage detecting circuit 18 and the battery temperature detecting circuit 17 are used.
Besides, a timer in which a charging time is set, a timer using a set time of the timer, a correlation between a battery voltage and a battery temperature, or a timer that detects a difference between a battery temperature and an ambient temperature may be used. These may be arbitrarily combined. That is, the number and type of the charge state detection means are arbitrary.

[Effect of the Invention] As described above, in the present invention, the charge current control circuit is provided with the feedback amount control means for making the control signal output from the charge current control circuit constant by the plurality of charge state detection means. When a predetermined state of charge is detected by the state-of-charge detection means, a constant charge current can be supplied to the secondary battery without variation by the feedback amount control means, so that stable charge control can be performed. There is.

[Brief description of the drawings]

FIG. 1 is a main part circuit diagram of one embodiment of the present invention, FIG. 2 is an operation explanatory view of the above embodiment, FIGS. 3 and 4 are main part circuit diagrams of other embodiments, respectively, and FIG. FIG. 6 is a block diagram showing a circuit configuration of a control circuit IC, and FIG. 7 is an operation explanatory diagram of the same. 1 is an inverter, 2 is a control circuit, 3 is a charging current control circuit, 17 is a battery temperature detection circuit, 18 is a battery voltage detection circuit, 19
Is a feedback amount control means, B is a secondary battery, and PC is a photocoupler.

Claims (2)

(57) [Claims] A charge current control circuit for detecting a charge current and outputting a control signal having a signal amount corresponding to the magnitude of the charge current to a control circuit of an inverter; A plurality of charge state detecting means for inputting the detection signal to the charge current control circuit and outputting a control signal for minimizing the charge current through the charge current control circuit when the charge state becomes a predetermined state; A charging amount control means for making the control signal output from the charging current control circuit constant by the charging state detection means of the above-mentioned charging current control circuit. 2. The battery charger according to claim 1, wherein signal transmission between the charging current control circuit and the control circuit is performed via a photocoupler.