JPS61285031A - Charge controlling circuit - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a charging control circuit for constant voltage control in a single type series regulator.

Conventional technology In conventional constant-voltage charge control circuits, a transistor is inserted in series between the power supply and the battery, the battery voltage is further divided by a resistor, and this value is compared with a reference voltage using a comparator. The base current of the transistor is often controlled so that the voltage across the battery is constant.

However, with this method, if charging continues for a long time, there is a risk that the battery will be overcharged, so if the charging current drops, it will be necessary to lower the set voltage of the constant voltage a little. Therefore, as shown in FIG.
, rectifier 102 , main control transistor 103 and battery 1
A resistor 10F5 for current detection is inserted into the series circuit of the second transistor 10F5, and the voltage across the resistor 106 is compared with a reference value (set value) in the comparator circuit 106.
07 was set to 0N-OFFL, and the voltage of battery 1o4 was changed. Note that the resistor 108 is for operating the constant voltage circuit 109, and is the resistor 11o.

111 and 112 are for dividing the voltage of the battery 104.

Problems to be Solved by the Invention In such conventional circuits, it is necessary to insert a current detection resistor in series in the path of the main charging current, and this resistance decreases to a weak value as the battery decreases. When this happens, it is necessary to generate enough voltage to operate the comparison circuit, so a somewhat large resistance value must be selected. Therefore, when charging with a large current, a considerable amount of heat is generated, and the resistor must be large and have a high wattage, making the device itself large and heavy. Moreover, it must be designed with consideration for heat dissipation. . Furthermore, white spots in the resistor lead to a loss of charging current, deteriorating efficiency.

The present invention solves these conventional problems, and aims to provide a variable constant voltage setting value charging control circuit with a simple configuration and no heat loss or efficiency loss.

Means for Solving the Problems The present invention solves the above problems by connecting the base terminal of the transistor that shorts a part of the voltage detection resistor of the battery to the voltage on the input side (rectifier side) of the main control transistor. It is constructed by connecting diodes in opposite directions to the divided points, and then smoothing the voltage at the connection points with a capacitor.

Effect of the Invention With the above-described configuration, the present invention detects a current drop after reaching a constant voltage from a voltage rise on the rectifier side using the V-I characteristic of the transformer, and then converts the detected voltage through an integrating circuit with a large time constant. In addition to the base terminal of the transistor that shorts a part of the battery voltage detection resistor, this transistor is turned on to reduce the voltage applied to the battery, so there is no need to insert a full series resistor. , overcharging of the battery can be prevented without causing loss such as heat generation.

Example Examples thereof will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is an input power source, which is a general 100V power source. 2 is a transformer that lowers the voltage, 3 is a rectifier that converts alternating current to direct current, 4 is a main control transistor, and 5 is a secondary battery. A closed circuit is formed by the above,
The charging current is supplied to the secondary battery 5 through the above-mentioned path. 6 is a smoothing capacitor, 7 is a constant voltage circuit, and 8 is a resistor for supplying current to this constant voltage circuit 7. 10,11
.

12 is a resistor that divides the voltage of the battery 6, and each resistance value is set to R1°1R111R12. 13 is a second transistor for short-circuiting part of the resistor 10, and its base terminal 13B is connected to 70 points. Voltage 1 vb at collector (battery side) terminal 4C of main control transistor 4, emitter (rectifier side) terminal 4E
voltage at the connection point of va1 resistors 11 and 12, constant voltage circuit 7
Let the voltage of the reference terminal 7B of . Furthermore, 14
．． 15 is a resistor that divides the voltage V & wo on the rectifier side, 16 is a diode, 17.18 is a resistor and a capacitor that form an integrating circuit, and the voltage at the connection point is V. shall be.

FIG. 2 shows the VA during charging in the embodiment shown in FIG.

A graph showing changes in the voltage and charging current of vb.
When the voltage of b reaches the first set value v1, the constant voltage circuit 7
is activated, the voltage is made constant, and when the charging progresses further and the current decreases to the set value 12, the second transistor 1
3 is activated, the voltage of vb is lowered to the second set value v2, and the current is further rapidly reduced to a value at which overcharging does not occur.

FIG. 3 shows va and V during charging in the embodiment shown in FIG. It shows the change in the voltage waveform of , and the voltage before the voltage of the secondary battery 5 reaches v1 is val and V. Va2 and V when in the state of 1°vl. In state 2, the current gradually increases and decreases to 12, and at t, Va3 and V. It rises to state 3.

Above, FIGS. 1 to 3 will be explained together. When the voltage of the secondary battery 5 is below v1, the second transistor 1
3 is in the OFF state, and the constant voltage circuit element drives the main control transistor 4 so that the voltage V at the reference terminal 7B is always constant. However, even if the main control transistor 4 becomes saturated, the transformer Since the capacity of 2 is limited, the voltage does not rise, and the voltages of Va and VC are val,
It is in the vol state.

As charging of the battery 5 progresses and the voltage reaches vl,
The constant voltage circuit 7 suppresses the base current of the main control transistor 4 so that the voltage of V becomes constant, and the voltage of the battery 6 is made constant. V at that time. Although the voltage rises to about vc2, the value is set so that the second transistor 13 does not turn on yet. In addition, in FIG. 3, the reason va includes ripple is because the smoothing capacitor 6 cannot completely smooth the ripple.
vc can be calculated as shown in the figure by setting the time constant of the resistor 17 and capacitor 18 of the integrating circuit to be sufficiently large for the power supply frequency of 50/80Hz, and by connecting the diode 16 in the opposite direction to the connection point of the resistors 14 and 16. It can be completely smoothed so that

Further, as charging of the secondary battery 6 progresses and the current decreases to 12, va is determined from the V-I characteristic of the transformer 2.

The voltage of vo increases like va3 and va3. And this time, for the first time, V. By setting the values of the resistors 14 and 16 so that the second transistor turns ON when the voltage 3 rises to this level, the second transistor 13 turns ON and the resistor 10 is short-circuited. Then,
This will be applied to the secondary battery 6. After that, vb=v2
As a result, the constant voltage circuit 7 enters a steady state, the current decreases to almost zero, and overcharging is no longer inevitable. In addition, vo
The reason why the O value is completely smoothed is because if it is not smoothed, the second transistor 13 will repeat ON-OFF operation due to the ripple component, and (b) will not be stable and a sufficient effect will not be obtained.

In this way, the constant voltage setting value can be varied without inserting a series resistor, and there is no heat generation from the resistor or deterioration of efficiency due to it, and a small and lightweight charging control circuit can be realized.
The fear of overcharging can be eliminated.

In addition, in the above embodiment, an example of a circuit that changes the constant voltage setting value only once is shown, but it goes without saying that it is possible to change the constant voltage setting value in many steps by simply adding a similar circuit. Nor.

Effects of the Invention As is clear from the above explanation, according to the present invention, the decrease in charging current is not detected by a series resistor, but by dividing the voltage on the rectifier side of the main control transistor, and dividing the voltage with a sufficient time constant. By detecting the value passed through an integrating circuit with a large value, it is possible to eliminate wasteful heat generation and the resulting deterioration of efficiency, make the charging control circuit, and ultimately the equipment in which it is incorporated, smaller and lighter, and prevent overheating of the battery. Its effects are significant, such as being able to prevent charging.

[Brief explanation of the drawing]

FIG. 1 is a charging control circuit diagram according to an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams showing changes in voltage and current at each part, and FIG. 4 is a conventional charging control circuit diagram. 2...Transformer, 3...Rectifier, 4...
... Main control transistor, 5 ... Secondary battery, 7 ... Constant voltage circuit, 10, 11.12.
...Resistor, 13...Second transistor, 16...Diode, 17°18...
...Integrator circuit (resistance, capacitor). lθ, lノ 12... 搏・4wat1□given

Claims (1)

[Claims] A constant voltage circuit in which a voltage drop transformer, a rectifier, a main control transistor, and a secondary battery are connected in series is provided with a second transistor that shorts a part of the voltage dividing resistor of the secondary battery, and the main control transistor is A charge control circuit that divides the voltage on the input side by resistance, and connects the base terminal of the second transistor to the output of an integrating circuit with a time constant that is sufficiently larger than the frequency of the power supply through a diode in the opposite direction at the connection point. .