JP3083549B2 - Constant current charging circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant current charging circuit that charges with a small number of transistors.

[Conventional technology]

In the case of charging a large-voltage storage battery with a constant current by a charger, the configuration is based on the configuration of a “series regulator type” circuit diagram schematically shown in FIG.

In FIG. 3, 1 is a storage battery to be charged, 2-1 and 2
.., 3-n are power transistors, and 4 is a diode. The storage battery 1 to be charged has a large number of storage cells connected in series like a cathode absorption type sealed alkaline storage battery, and the DC input terminal 2-
When charging with a high voltage and a large current such as 1,2-2 to 120V, a plurality of transistors such as the power transistors 3-1 ... 3-n are connected in parallel to shunt the charging current, thereby operating the transistor. Was controlled within the safe operation area. For example, if the voltage between the collector and the emitter is 77 V as shown in FIG. 4, the DC operation safe area is 0.6 A or less. Therefore, the input terminals 2-1 and 2-2
When performing constant current charging from 2 to 2 A, it is necessary to connect four transistors (that is, n = 4 of 3-n) in parallel.

[Problems to be solved by the invention]

In the circuit configuration shown in FIG. 3, it is necessary to connect a large number of transistors in parallel in order to flow a predetermined charging current. Further, since a large-sized and high-standard one is used so that the emitter-collector voltage of each transistor can withstand a high value, the charger becomes extremely expensive.

[Means for solving the problem]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned disadvantages of the related art, and provides a constant current charging circuit using a smaller number of transistors and obtaining a larger output. Are connected in series to one terminal of the battery to be charged, a circuit for controlling the constant current is connected between each stage of the transistor, and both electrodes are connected between the emitter and collector of each stage transistor. A circuit for stabilizing the voltage between them is connected.

(Operation)

The current from the DC power supply passes through the transistor while being controlled to a constant current state by the constant current control circuit, and charges the battery. At the same time, it is controlled by the constant voltage control circuit so that the voltage between the emitter and collector of each transistor becomes the same value, so even if there is a slight difference in the operating characteristics of each transistor, it is accurately controlled so as to be equal Is done.

〔Example〕

FIG. 1 is a diagram showing the principle configuration of the present invention. In FIG. 1, 1 is a storage battery, 2-1 and 2-2 are DC voltage input terminals, 3-1 and 3-2 are transistors connected in series,
Indicates a DC power supply, 6 indicates a constant current control circuit, and 7-1 and 7-2 indicate constant current control circuits.

The configuration of the present invention is as follows. At least two emitter-collector circuits of the transistors 3-1 and 3-2 are connected in series to one terminal 2-1 of the DC power supply 5 and connected to one terminal of the battery 1 to be charged. That
Connecting the constant current control circuit 6 between the stages of the transistors 3-1 and 3-2;
That is, the circuits 7-1 and 7-2 for stabilizing the voltage between the two electrodes are connected between the emitter and the collector of the second.

1, the current from the DC power supply 5 passes through the transistors 3-1 and 3-2 while being controlled to a constant current state by the constant current control circuit 6, thereby charging the battery 1. At the same time, the constant voltage control circuits 7-1 and 7-2 are controlled so that the voltage between the emitter and the collector of each transistor has the same value. However, it is precisely controlled to be equal.

FIG. 2 is a circuit diagram showing an embodiment of the present invention. In FIG. 2, Q1 is the transistor 3-1 and Q2 of FIG.
Corresponds to the transistor 3-2. The three-terminal regulator IC1 and the resistance element R5 constitute a constant current control circuit 6. The low-voltage control circuits 7-1 and 7- are formed by the operational amplifier IC2, the transistor Q3, and the resistance elements R1 to R4 and R7 to R9.
2 and is indicated by 7.

Since the three-terminal regulator IC1 controls the voltage at both ends of the resistance element R5 to be constant, a constant current flows from the transistor Q1 to the transistor Q2.

The voltage between the emitter and collector of the transistor Q1
The constant voltage control circuit 7 operates so that V _CE1 is equal to the voltage V _CE2 between the emitter and the collector of the transistor Q2.

Assuming now that R1 = 100 kΩ, R2 = 1 kΩ, R3 = 100 kΩ, and R2 = 1 kΩ, the operational amplifier IC2 operates so that the voltages at both (+) and (−) input terminals thereof become equal. The voltage at the (−) terminal obtained by dividing the voltage at both ends and obtained on the R2 side (V _CE1 + V _CE2 ) × {R2 / (R1 + R2)} was obtained by dividing the voltage at both ends of R3 and R4 on the R4 side. The voltage at the (+) terminal should be equal to V _CE2 × {R4 / (R3 + R4)}. If the two equations are calculated as being equal, V _CE1 + V _CE2 = V _CE2 × (2 × 101) / (2 × 102) Therefore, V _CE1 = 0.98V _CE2 , and V _CE1 and V _CE2 are almost equal.

If the configuration of the charger is the same as that of the prior art, the voltage 77V between the emitter and the collector in FIG. 3 is 1/2 of 38.5V in FIG. 2, so that the safe operation can be understood from FIG. A DC current of 4 A can flow as an area. That is, the charging current of 2 A can flow with a sufficient margin.

More specifically, for example, the voltage between the emitter and collector of the transistor used was reduced to 38.5 V.
It is sufficient to connect two transistors in series that can pass the charging current of A. In the configuration shown in FIG. 3 of the prior art, four transistors had to be connected in parallel, so that the number of transistors used could be reduced. Alternatively, in the prior art, if the collector current is of a high standard that allows a larger collector current to flow for a predetermined emitter-collector voltage, two devices may be connected in parallel, but this naturally results in an expensive device. Was. According to the present invention, instead of such a high standard, it may be a standard standard,
In order to allow a charging current of 2 A to flow, a transistor having a lower standard than the transistor shown in FIG. 4 may be used. Or 2A in Fig. 2
Instead, it can be used as a 4A type constant current charger.

〔The invention's effect〕

Thus, according to the present invention, since the power transistors are connected in series to divide the voltage and connect to the battery,
The transistors in each stage can be easily set within a safe operation region. Compared to the conventional parallel type, the number of transistors to be used is reduced, or a low-standard one is used because a voltage / current control circuit is connected instead of simply using a series type. It is possible to increase the capacity. That is, the performance of the charger can be easily improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention, FIG. 2 is a circuit diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing the configuration of a conventional charging circuit, and FIG. FIG. 7 is a diagram showing the operating characteristics of the transistor. 1. Batteries 2-1 and 2-2 DC voltage input terminals 3-1 and 3-2 Transistors 5 DC power supplies 6 Constant current control circuits 7-1 and 7-2 Constant voltage control circuit

Claims (1)

(57) [Claims] An emitter-collector circuit of at least two transistors is connected in series to one terminal of a DC power supply, connected to one terminal of a battery to be charged, and performs constant current control between each stage of the transistor. A constant current charging circuit, comprising: a circuit connected to the circuit; and a circuit for stabilizing a voltage between both electrodes between an emitter and a collector of each transistor.