JPS593106B2 - Jiyuden Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a charging circuit that detects the voltage of the battery 1 to be charged and controls the charging current to prevent overcharging. A set voltage changing circuit 3 is provided that sets the constant voltage Vs high at the beginning of charging, and when the charging current drops to a constant current value IB2 at the end of charging, lowers the charging control set voltage Vs to change the operating point of the control circuit 2. An object of the charging circuit is to provide a charging circuit that can quickly charge a battery to be charged without overcharging.

FIG. 1 is a circuit diagram of a conventional charging circuit using a so-called converter oscillation circuit. 5 is a charging section that forms a ringing chain type converter oscillation circuit with a converter transformer and an output transistor Tr3; An output winding 0Lo of the converter transformer is connected to the rectifier power supply circuit 4 connected to the power supply e, and is connected between the other end of the resistor R9 connected in series to the emitter of the output transistor Tr3 and the negative electrode of the rectifier power supply circuit 4. A series circuit with diode D3,
A battery to be charged 1 connected in parallel is inserted into the series circuit, and the collector of the output transistor Tr3 is connected to the positive electrode of the rectifying power supply circuit 4 via the collector winding Lc of the converter transformer.

Reference numeral 2 denotes a control circuit that uses the rectifier power supply circuit 4 as a power source, and detects a sudden rise in the battery voltage VB at the end of charging of the battery 1 to be charged, and determines whether the battery voltage is higher than the reference voltage across the diode group D2. When the set voltage Vs determined by the voltage Vs is reached, the transistor Trl is turned off and the transistor Tr2 is turned on.
This is for controlling the base current of No. 3 with the transistor Tr-2 to stop the oscillation of the charging section 5.

That is, when the battery voltage VB of the battery 1 to be charged reaches the set value Vs as shown in FIG. Therefore, the operation of charging section 5 is controlled and reduced. However, the control circuit 2 described above intermittently controls the charging unit 5 when the battery voltage B falls below the set voltage Vs due to natural discharge etc. after the charging unit 5 stops oscillating so that the battery voltage VB is maintained at the set voltage V8. It is designed to operate to perform supplementary charging. Assuming that the average current flowing during this supplementary charging is the final charging current 1B0, charging will be performed for a long time with this current 1B0 after charging is completed. Therefore, it is necessary to keep this current 1B0 below the safe current IBL at which battery deterioration will not be a problem, but if the set voltage 8 is set high, the safe current 1BL that the battery 1 to be charged at that voltage can take will be a low value. Therefore, by setting the set voltage Vs low, the safe current IBL that can be taken by the battery 1 charged to that voltage is increased, and the battery It is necessary to enable supplementary charging in which deterioration is not a problem. On the other hand, the battery 1 to be charged has a relatively small internal resistance r1 at the beginning of charging, and after the battery voltage rises rapidly after charging is completed, it has a large internal resistance R2, so the charging current increases to a certain extent. However, since the internal resistance is small, the battery voltage at the beginning of charging is not affected by the magnitude of the charging current, but at the end of charging, the battery voltage is significantly affected by the magnitude of the charging current. Therefore, if an M type 450 mAh nickel cadmium storage battery is used as the battery 1 to be charged and the conventional circuit shown in FIG. 1 is used, charging for one hour is possible. However, when performing rapid charging with a large charging current, the low internal resistance value of the battery 1 to be charged at the initial stage of charging also becomes a problem. In other words, for example, if a low set voltage Vs is set as described above in consideration of battery deterioration due to being charged after charging is completed, if a large charging current is applied, the battery voltage VB will exceed the set voltage Vs even with a low internal resistance, and the battery voltage VB will be sufficient. There is a problem in that the battery cannot be charged. Therefore, in the conventional circuit, it is difficult to suppress the charging current at the end of charging to a certain value or less and quickly complete charging of the battery to be charged because contradictory setting conditions of the control circuit 2 are required.

The present invention has been provided in view of the above-mentioned drawbacks, and will be described in detail below with reference to Examples.

FIG. 3 is a plotter diagram of an embodiment of the present invention.
is a setting voltage changing circuit for controlling the charging control setting voltage of the Fbl leg circuit 2, and the setting voltage changing circuit 3 is connected to the charging section 5.
In other words, the charging current flowing from the charging unit 5 to the battery 1 to be charged is indirectly detected by the charging current detection circuit 6, and upon receiving the detection signal, the charging current is detected at the initial stage of charging when the charging current is large. In this case, the charging control setting voltage s of the control circuit 2 is set high, and when the charging current decreases to a constant value 1B2 at the end of charging when the charging current decreases, the charging control setting voltage s of the control circuit 2 is set high.
By lowering the charging current 1B1 at the initial set voltage V8l, the current at the end of charging is suppressed to a smaller value. Next, the operation will be further explained using the specific circuit shown in FIG.

When the charging section 5 constituting the converter oscillation circuit is operating in oscillation, a voltage is generated across the resistor R9 connected in series to the emitter of the output transistor Tr3 due to the emitter current of the output transistor Tr3. At this time, as shown in Figure 5b, a larger voltage oscillates at five points in the figure than when it does not oscillate.
A distinction is made between oscillation and non-oscillation. Incidentally, FIG. 5a shows the output waveform of the rectifier power supply circuit 4 consisting of the diode bridge Dx. As a result, the transistor Tr4 oscillates and the emitter current of the transistor Tr3 flows, and the sum of the voltages across the resistor R and the charged battery 1 becomes as shown in Figure 5b, and this voltage is divided. When the voltage applied to the base of the transistor Tr4 is equal to or higher than a predetermined level, the transistor Tr4 is turned on, and the oscillation of the charging section 5 is detected by this on/off operation, and the on/off operation signal of the transistor Tr4 is applied to the base of the transistor Tr5. The waveform is shaped by the function of the emitter-to-emitter capacitor and transistor Tr5,
A rectangular wave as shown in FIG. 5c is output to the collector of the transistor Tr5. Here, when the waveforms at five points in FIG. 4 reach the high level shown in FIG. 5c, the transistor T
r6 becomes conductive, capacitor C5 is charged, and the terminal voltage of capacitor C5 rises as shown in FIG. 5d. here,
When the voltage at four points in the figure is pulsating as shown in FIG. 6A, the voltage at point 5 in FIG. 6 is generated at the initial stage of charging. As charging progresses, the charging control setting voltage V determined by the diode group D2 provided inside the control circuit 2
s, the control circuit 2 operates and the charging section 5 is controlled. For this reason, the oscillation interval of the charging section 5 becomes longer, and the voltages generated at the five points become as shown in FIG. It becomes lower as shown in . Therefore, the number of times that the capacitor C5 of the charging current detection circuit 6 is charged decreases, and the average voltage of the capacitor C5 becomes lower, and this voltage becomes a value V corresponding to the constant value 1B2 of the charging current. 5, the transistor Tr7 of the set voltage changing circuit 3 is turned on from off, the transistor Tr8 is turned off from on, the transistor Tr9 is turned on from off, and the resistor R42, transistor Tr,...
A current flows through the resistor R7, and due to the voltage drop across the resistor R7, the charging control setting voltage Vs of the control circuit 2 decreases from Vs to VS2, and the charging current becomes smaller as shown at the four points in FIG. controlled.

Note that at the beginning of charging, there is no charge in capacitor C5,
The transistor Tr9 is turned on and the set voltage of the control circuit 2 is VS2, but since the battery voltage is sufficiently low, the charging current increases, that is, the oscillation of the charging section 5 continues and the charging current of the capacitor C5 increases. The voltage rises immediately and the set voltage is V.
SI, the state of capacitor C5 at the start of charging can be ignored. As described above, the present invention sets the charging control setting voltage with respect to the voltage of the battery to be charged high at the beginning of charging, and when the charging current decreases to a constant current B2 at the end of charging, the charging control setting voltage Vs is lowered to control the control circuit. Since a set voltage changing circuit is provided to change the operating point of the battery, even if the battery being charged is rapidly charged in a short period of time with a large charging current, the current can be maintained below the safe current after charging is complete. Moreover, since the charging current at the end of charging rapidly decreases, the charging completion time can be clearly determined.

Further, the present invention has a switching means driven by the voltage of a resistor connected in series with the output transistor of the charging section, which is generated when the charging section oscillates, and when the switching means is on, the capacitor is charged, and when the switching means is off, the capacitor is connected in parallel. The device is equipped with a charging current detection circuit that generates a voltage across the capacitor in accordance with the charging current that flows from the charging section to the battery to be charged by discharging through the resistor, so that the output of the output winding of the charging section and the It is possible to detect the charging current without inserting a current detection element such as a resistor between the charging battery and a large current flows compared to the output circuit of the output winding, where a small current flows. By detecting the presence or absence of oscillation using the resistance of the emitter circuit of the output transistor,
This has the effect of reducing loss and reliably detecting charging current.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the conventional example, Fig. 2 is a charging characteristic diagram of the battery to be charged as above, Fig. 3 is a circuit block diagram of an embodiment of the present invention, Fig. 4 is a specific circuit diagram of the same as above, and Fig. 5 Figures a to d and 6th
Figures A to C are time charts of each part of the same as above, and Figure 7 is a charging current characteristic diagram of the same as above, where 1 is the battery to be charged, 2 is the control circuit, 3 is the set voltage changing circuit, and 6 is the charging current. In the detection circuit, C5 is a capacitor, Tr4 is a transistor, R9 is a resistor, and Vs is a charging control setting voltage.

Claims (1)

[Claims] 1. A battery to be charged is connected to the output winding of a ringing choke type oscillation circuit via a diode, and the battery to be charged is connected to the battery to be charged by the oscillation output generated by the output winding. In a charging circuit equipped with a control circuit that compares the battery voltage with a preset charging control setting voltage and stops the oscillation of the charging section when the battery voltage reaches the charging control setting voltage, the charging that occurs when the charging section oscillates. It has a switching means driven by the voltage of a resistor connected in series with the output transistor of the section, and when the switching means is on, the capacitor is charged, and when it is off, it is discharged through the resistor connected in parallel to the capacitor, thereby removing the voltage from the charging section. A charging current detection circuit that generates a voltage across a capacitor in accordance with the charging current flowing through a charging battery, and a charging control setting voltage of a control circuit when it is detected that the voltage of the capacitor has decreased below a certain value. A charging circuit comprising: a set voltage changing circuit that lowers the set voltage and changes the operating point of the control circuit.