JPH0799911B2 - Electronic switch circuit for charging control - Google Patents

Description

The present invention relates to a charging control electronic switch circuit of a charger,
Particularly, it relates to prevention of variation in switching due to voltage fluctuation.

(Prior Art) Generally, in order to perform stable charge control, an electronic switch circuit for charge control has a value of a terminal voltage of a battery to be charged when a transistor performing charge control causes a switching operation from on to off, that is, A threshold voltage and a difference between a terminal voltage of a battery to be charged which causes a switching operation of the transistor from off to on and the threshold value, that is, a variation in a switching voltage difference (hysteresis width) of the transistor. Is required
For this purpose, the one disclosed in Japanese Patent Publication No. 55-42577 has been proposed.

This has the circuit configuration shown in FIG. 2 and has power connection terminals a and b.
A series circuit of a _first resistor R ₁ and a zener diode Dz is connected between them, and a second resistor R ₂ , a diode D ₃ , a base / emitter of the first transistor 2 and a _third resistor R ₃ are connected across the zener diode Dz. A series circuit of a resistor R ₅ and a battery to be charged 1 which is charged by a charging circuit (which is connected between terminals a and b) not shown in the figure, and a series circuit of a diode group D ₁ and a resistor R _7. A first voltage dividing element configured, a resistor R ₈ and a series circuit of a second voltage dividing element configured by a series circuit of a diode group D ₂ are connected in parallel to form a second resistor R ₂ and Between the connection point with the diode D ₃ and the connection point between the emitter of the first transistor 2 and the third resistor R ₅ , the collector / emitter of the second transistor 3 and the fourth resistor R ₆ are connected in series. And the base of the second transistor 3 is connected to the connection point between the first voltage dividing element and the second voltage dividing element. The resistor R ₃ is connected to the connection point between the anti-R ₁ and the power supply connection terminal and the collector of the first transistor 2,
The resistor R ₄ is connected to the connection point between the collector of the transistor 2, the third resistor R _5, and the battery 1 to be charged.

In FIG. 2, c and d are terminals for controlling the charging circuit (not shown), and the voltage between the control terminals c and d changes depending on whether the first transistor 2 is turned on or off. It is designed to control the charging circuit of.

That is, the charging current of the charging circuit (not shown) is made to flow between the control terminal d and the power supply connection terminal b, and the battery 1 to be charged connected between both terminals d and b is charged. In such a conventional circuit, when the voltage Vx between the terminals d and b is gradually increased from zero, the voltage VY between the control terminals c and d changes as follows. That is, as shown in FIG. 3, the terminal voltage Vx of the battery 1 to be charged
Is Vx <Vth−Hw (where Vth is the terminal voltage (threshold value) of the battery 1 to be charged when the second transistor 3 causes a switching operation from on to off, and Hw is the second transistor 3
Is a difference between the terminal voltage of the battery to be charged 1 that causes a switching operation from off to on and the threshold value Vth, that is, the hysteresis width].
When the second transistor 3 is turned on and the first transistor 2 is turned off, the voltage VY becomes VYH as shown in the figure, and the terminal voltage Vx gradually increases and exceeds the threshold value Vth.
The second transistor 3 turns off and the first transistor 2 turns on, causing VY to change from VYH to VYL as shown. Conversely, when the voltage Vx is lowered, Vx = Vth−Hw (Hw is the difference between the switching voltages), the second transistor 3 is switched from off to on, and the first transistor 2 is switched from on to off. The voltage VY between the terminals c and d changes from VYL to VYH.

Such an electronic switch circuit for charge control is used in a quick charge circuit with overcharge prevention. When the battery 1 to be charged is connected between the terminals d and b, the voltage Vx becomes the battery voltage and VY = VYH.
When VY = VYL, the charging current from the charging circuit (not shown) is cut off. On the other hand, in the battery to be charged,
In particular, there is a large internal resistance at the end of charging, the battery voltage is high when the charging current is flowing, and the battery voltage is low when the charging current is not flowing.Therefore, the voltage detection method that controls the charging current by the high and low battery voltage is used. In that case, the charging current cutoff and the charging are not unnecessarily repeated, and the difference Hw between the switching voltages is set as described above to perform stable charging current control.

Further, in the charging current characteristic shown in FIG. 4, when the initial charging current is controlled at the time t ₀ , whether the subsequent change in the charging current is gradual as in (a) or abrupt as in (b). , The internal resistance of the battery is in agreement with the size at the end of charging, but it is determined by the size of the switching voltage difference Hw. When this Hw is large, the charging current is rapidly controlled as shown in (b). Further, after charging control, the battery is charged with a constant small current for a long time. And the size of. In this way, the difference Hw between the optimum threshold value Vth and the switching voltage exists due to the end-of-charge current and the sudden change in the charge control.

Thus, the threshold value Vth is set to determine the charge capacity of the battery to be charged, and the switching voltage difference Hw keeps the charging current after completion of charging at the safe current of the battery to be charged, resulting in capacity deterioration due to overcharging. It is necessary to set the optimum value in order to prevent this.

Now, in the conventional circuit of FIG. 2, the threshold value Vt
h, the difference between the switching voltage Hw is Vth = Vb (3) -VBE ( 3) - (R 5 + R 6) ie (3) ...
[1] Equation Hw = R ₅ · ie (2) − (R ₅ + R ₆ ) ie (3) Equation [2] where Vb (3): base potential of transistor 3 VBE (3): transistor 3 in this order Direction Base-emitter voltage R ₅ : Resistance value of resistance R ₅ R ₆ : Resistance value of resistance R ₆ ie (3): Emitter current when transistor 3 is on ie (2): Emitter current when transistor 2 is on R _2: the resistance R ₂ of the resistance value Von (3): (the voltage between the collector and emitter with the ON) ON voltage of the transistor 3 Von (2): the collector-to-emitter voltage at the time of the ON voltage (ON transistor 2 ) Vcc: power supply connection terminal voltage VDZ: diode Dz terminal voltage VDz, Von (3), Von (2) is ie (3 from approximately constant [3] formula) is determined by the resistor R _2, R _6, R ₅ , Vth is almost constant because of the resistances R ₂ , R ₆ and R _{5 according} to the formula [1], but ie (2) is not constant because Vcc varies, so Hw is ie (2 It does not become constant due to fluctuations in).

An example of connecting the conventional circuit of FIG. 2 to a charging circuit is shown in FIG. In the figure, A is a transistor inverter,
The transistor inverter A forms a so-called blocking oscillation circuit, rectifies an AC power supply by a rectification circuit C, and oscillates using the rectified DC power as a power supply. A collector winding 7 is provided at both output terminals of the rectification circuit C. , The output transistor 4, the emitter resistor 7, the series circuit of the diode 8 and the output winding 5, and the power supply connection terminals a and b of the charging control electronic switch circuit B described above are connected. The terminal d is connected to the connection point of the resistor 7 and the diode 8. A base feedback winding 9 is connected between the terminal c and the base of the output transistor 4,
Connect capacitor 10 between terminals c and d. The battery 1 to be charged is connected between the terminals d and b. In the figure, 11 is a spike voltage absorbing capacitor, 12 is a spike voltage absorbing resistor, 13 is a current limiting resistor for rectifying circuit C, 14 is a rectifying diode, 15 is a noise preventing choke coil, and 16 and 17 are capacitors. Is.

Since the output terminal waveform of the rectifier circuit C has a waveform as shown in FIG. 6, the voltage Vcc between the power supply terminals a and b of the electronic switch circuit B varies and is not stable, so ie (2) varies and Hw is It is not constant.

That is, there is no problem in the case where the voltage applied to the electronic switch circuit B does not fluctuate, but in reality, since there is a voltage fluctuation as shown in FIG. 6, the switching voltage difference Hw of the transistors corresponding to the hysteresis width varies. There is a problem that stable charging control cannot be performed.

(Object of the invention) The present invention has been made in view of the above-mentioned points, and a switching voltage difference (hysteresis width) of a transistor in which a collector-emitter is connected between an emitter and a base of a charging current control transistor is reduced. It is an object of the present invention to provide a charge control electronic switch circuit that is stable and can set an optimum value without being affected by power supply voltage fluctuations.

(Structure of the Invention) According to the present invention, a series circuit of a first resistor and a zener diode is connected between power supply connection terminals, and a second resistor, a diode, a base / emitter of a first transistor, and a third resistor are connected. A series circuit with a battery to be charged, which is charged by a charging circuit, and a series circuit with a first voltage dividing element and a second voltage dividing element are connected in parallel to both ends of the Zener diode, and a second resistor is connected. And a collector / emitter of the second transistor and a fourth resistor are connected in series between the connection point of the diode and the connection point of the emitter of the first transistor and the third resistor,
The base of the second transistor is connected to the connection point of the first voltage dividing element and the second voltage dividing element, and control is performed between the connection point of the first resistor and the Zener diode and the collector of the first transistor. An electronic switch circuit for charge control is formed by connecting the emitter / base of a transistor and a fifth resistor in series, and connecting the switching means to the collector of the control transistor.

(Example) Hereinafter, the present invention will be described with reference to an example shown in FIG. This embodiment circuit is the same as the conventional example circuit of FIG.
R ₄ is removed and the collector of the first transistor 2 is a resistor
Separate from R ₃ . A series circuit of the emitter / base of the control transistor 4 and the resistor R ₉ is connected between the connection point of the resistor R ₁ and the Zener diode Dz and the collector of the first transistor 2. In addition, a resistor R ₃ and a transistor 18 are connected between the power connection terminals.
A series circuit of the collector and the emitter is connected, and a resistor R ₁₀ is connected to the base of the transistor 18, and these constitute a switching means D.

The resistor ₁₀ of this switching means D is a control transistor 4
Connect to the collector.

The operation of this embodiment is different from the conventional example of FIG. 2 in that when the transistor 2 is on, the control transistor 4 is on and the switching means D is operated. That is,
When the control transistor 4 is turned on, the transistor 18 is turned on and the collector of the transistor 18, that is, the terminal c is changed to the terminal b.
From the viewpoint, it becomes Von (4) (ON voltage of the transistor 18). Conversely, when the transistor 2 is turned off, the control transistor 4 is turned off and the transistor 18 is also turned off.

In the charge control electronic switch circuit of the present invention, the threshold value Vth and the switching voltage difference Hw are given by the equations [1] and [2] as in the conventional example. However VEB (4): Control transistor substantially constant emitter-base voltage of 4 R _9: resistance given by the resistance value of R _9, ie (2) the resistance R ₉ regardless of the supply pin voltage compared to the conventional example, Since it is determined by R ₅ and becomes almost constant, the switching voltage difference Hw becomes constant.

(Effect of the Invention) As described above, according to the present invention, since the current flowing through the charging control transistor is substantially constant regardless of the power supply terminal voltage, the difference between the on / off switching voltage of the charging control transistor is large. The (hysteresis width) can be set to a stable and optimum value without being affected by the fluctuation of the power supply voltage, and the charged battery can be stably charged.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of a charge control electronic switch circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional charge control electronic switch circuit, and FIG. FIG. 4 is a charging current characteristic diagram of the same as above, FIG. 5 is a circuit diagram of a charging circuit to which a conventional electronic switch circuit is connected, and FIG. 6 is an output waveform diagram of the above rectifier circuit. 1 ... Battery to be charged, 2 ... First transistor, 3 ...
… Second transistor, 4 …… Control transistor, a, b
...... Power supply connection terminal, R ₁ ...... First resistance, R ₂ ...... Second resistance, R ₅ ...... Third resistance, R ₆ ...... Fourth resistance, R ₇ ...... Resistance (First resistance Voltage dividing element), R ₈ ... resistance (second voltage dividing element),
R ₉ ... Fifth resistance, Dz ... Zener diode, D ₁ ... Diode ( _first voltage dividing element), D ₂ ... (Second voltage dividing element), D ₃ ... Diode, D ... … Switching means.

Claims (1)

[Claims] 1. A series circuit of a first resistor and a zener diode is connected between power supply connection terminals and charged by a second resistor, a diode, a base / emitter of a first transistor, a third resistor and a charging circuit. A series circuit with the battery to be charged and a series circuit with the first voltage dividing element and the second voltage dividing element are connected in parallel to both ends of the Zener diode, and the second resistor and the diode are connected. The collector / emitter of the second transistor and the fourth resistor are connected in series between the point and the connection point of the emitter of the first transistor and the third resistor,
The base of the second transistor is connected to the connection point of the first voltage dividing element and the second voltage dividing element, and control is performed between the connection point of the first resistor and the Zener diode and the collector of the first transistor. An electronic switch circuit for charge control, characterized in that an emitter / base of a transistor and a fifth resistor are connected in series, and a collector of a control transistor is connected to a switching means.