JPH02266836A - Charge control circuit - Google Patents

Abstract

PURPOSE:To simplify detection of faint current without requiring any adjustment by comparing output current from a current detecting transistor with a predetermined value and switching output voltage from a constant voltage control circuit between at least two stages according to the comparison results. CONSTITUTION:When a charging battery 20 having under voltage is connected, a comparator 11 produces a positive output because the detected voltage is lower than a reference voltage, i.e., the voltage of a constant voltage element 12. Current also flows through the emitter of a transistor 6 arranged in mirror together with the charging current and the positive output from a comparator 14 is stabilized thus opening a switching element 16 and setting a high first stage voltage. When large charging current flows, voltage drop across the resistor 3 increases and a low second stage voltage is set. By such arrangement, even a faint current can be detected easily with no erroneous function.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a charging control circuit for a rechargeable battery.

BACKGROUND OF THE INVENTION In recent years, many devices with built-in charging functions have come into use. Moreover, various quick charging methods have been devised in response to the need to shorten charging time in response to market demands.

Among them, one method, the dual-role constant voltage charging control method, charges at the first constant voltage, which is a higher set voltage, at the initial stage of charging, and
When the t current drops (reduces) to a predetermined value, the set voltage is lowered and the voltage is switched to the second constant voltage.In cycle applications, this method does not cause overcharging problems even if charging is continued for a long time. On the other hand, in trickle applications, it has the advantage of being able to be fully charged in a relatively short time.

A conventional two-stage constant voltage charging control circuit will be described below.

FIG. 3 shows the circuit configuration of a conventional two-stage constant pressure charging circuit. In FIG. 3, 1 is a charging power source that supplies power to the battery. 7 is a transistor for controlling battery charging voltage, and 32 is a base-emitter resistance. 5,8.
10, 42, and 43 are resistors, and the transistor 9, the restrictor 11, and the constant voltage element 12 constitute a feedback loop for driving the transistor 7.

34 is a current detection resistor which drives the transistor 33 to apply feedback to the feedback μm amplifier. 38.
40 is a voltage dividing resistor, resistor 35.36 and adjustment volume 3
It becomes an input to the button comparator 39 together with the voltage divided by 7.

41 is a resistor driven by an open collector output comparator.

20 is a battery to be charged.

The operation of the double constant pressure charge control circuit constructed as described above will be explained below.

First, when the charging battery 20 whose battery voltage is insufficient is connected, the comparator outputs a positive output because the detected voltage is lower than the voltage of the constant voltage element 12 serving as the reference voltage. This drives transistor 7 and a charging current flows. When the charging current is higher than a certain current value, the output of the comparator 39 becomes negative and becomes stable. This is equivalent to inserting resistors 43 and 41 in parallel, and resistors 41, 42 .
43 is set to the first stage high voltage of the output detection voltage.

However, if the charging current is large, the voltage drop across the current detection resistor 34 becomes large, and when the first predetermined current value is reached, the transistor 33 is driven, and the collector current of the transistor 33 is connected to the parallel portion of the voltage dividing resistor 41 and 43. As a result, the voltage at the e input terminal of the comparator 411 is raised, and the output control 1ffll transistors 9 and 7 are controlled in the OFF direction.

Therefore, the overall charging (current) is limited, resulting in a constant current charging operation controlled by the first predetermined current.

After that, the charging battery (pressure j) gradually increases, and when it reaches the 1st voltage set in the first stage, it shifts to constant pressure operation.As the charging current begins to decrease due to constant voltage control, the voltage drop across the detection resistor 34 also decreases. In the same way, the θ input voltage of the comparator 39 also decreases because it is divided by the resistor 35. becomes open, which is equivalent to eliminating the resistor 41 that was connected in parallel, and as a result, it is set to the second low voltage composed of the detection resistors 42 and 43, and from then on, the voltage of the first stage of the second stage is set. Continue to control at a lower constant voltage.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the resistor 34, 35, 36, 38° 40 is used for current detection when transitioning from the first stage constant voltage charging to the second stage constant voltage charging. It takes time to set the constant, and it is necessary to adjust it with the volume 37.

Further, for this reason, it is necessary to adjust a large number of batteries in order to set the second predetermined charging current at a very small value.

Furthermore, the control at pressure of the constant core pressure changes from the voltage of the first stage to the voltage of the second role. Since the input direct pressures of both comparators 39 in the Shun 1-tsuka vary, the volume 37 must be set to prevent malfunctions, making adjustment work difficult.

Another problem is that the two control voltage settings for constant voltage control are achieved by connecting the resistors 41 and 43 in parallel, and by using only the resistor 43.
42.43 also need to be set and adjusted mutually,
It also had the disadvantage of not being able to improve accuracy.

The present invention solves the conventional problems as described above, and is capable of detecting a minute amount of current without requiring any effort to detect current when transitioning from constant voltage charging in the first stage to constant voltage charging in the second stage. To provide a charging control circuit that easily enables current detection, eliminates the fear of malfunction when setting a control voltage, and allows setting of two control voltages with high precision without adjusting.

Means for solving the problems In order to achieve this object, the charging system of the present invention includes a constant voltage control circuit, a charging sub-side transistor controlled by the constant voltage control circuit, and the charging control transistor. a current detection transistor connected to a current mirror in the current detection transistor, the output current of the current detection transistor is compared with a predetermined value, and the output pressure of the constant voltage control circuit is switched to at least two stages according to the comparison result. It has features that work.

Operation: With this configuration, the detection resistance value of the resistor that detects the output current of the current detection transistor connected to the charge control transistor as a current mirror is set.

The second predetermined charging voltage can be set by simply setting the reference voltage of the comparator.
It becomes possible to determine the current detection current.

Additionally, by simply increasing the detection resistance, it is possible to handle minute current detection.

Further, a stable reference voltage can be used as the input voltage of the comparator, and stable operation can be performed even when the output voltage shifts on its side.

Two constant voltage regulators (also, high A to lower control voltage)
By using a constant voltage element with a voltage difference between the two constant voltages, it is possible to improve the accuracy of both constant voltages and eliminate the need for adjustment work.

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to a drawing.

FIG. 1 is a diagram showing the configuration of a charging control circuit in a first embodiment of the present invention.

In FIG. 1, 3 is the emitter resistance of transistor 7;
4 is a constant voltage element that determines a constant current value together with resistor 3; 6 is a mirror transistor of transistor 7;

2 is a resistor that determines the current of the current mirror flowing through the resistor 3, 13 is a current detection resistor, 15 is a constant voltage element, 14 is a current detection comparator, 16 is a switch element, 17 is a constant voltage element, 18.19 is an output It is a voltage detection resistor.

The operation of the charging control circuit configured as described above will be explained below.

First, when the charging battery 2o whose battery voltage is insufficient is connected, the comparator 11 uses the constant voltage element 1 as a reference voltage.
Since the detected voltage is lower than the voltage of 2, a positive output is performed. This drives transistor 7 and a charging current flows. A current also flows through the emitter of the transistor 6, which has a mirror configuration with the charging current, and the voltage across the resistor 13 rises due to the collector current caused by the operation of the grounded transistor, and finally the reference voltage of the constant voltage element 15 increases. The output of the comparator 14 becomes positive and stable. As a result, the switch element 16 becomes open and the resistor 18.1
9 and a constant voltage element 17 to set the first stage high voltage.

However, if the charging current is large, the voltage drop across the resistor 3 will increase, and when the current reaches the point where it is clamped by the constant voltage element 4,
After that, a constant current charging operation of the first predetermined current determined by the constant voltage element 4 is performed.

After that, the charging battery voltage will gradually increase and! When the pressure reaches the set pressure for role 1, it shifts to constant voltage operation. As the charge Kl current begins to decrease due to constant voltage control, the transistor e connected to the transistor 7 in a current mirror
The emitter current of is also reduced. Due to the relationship between the emitter current and the collector current of the transistor 6, the voltage drop across the detection resistor 13 also decreases, and when the second predetermined charging current value is reached, the voltage drop determined by the collector current of the transistor 6 and the resistor 13 and the constant voltage When it matches the reference voltage of element 16, the output of ratio [114 becomes negative, turning on switch element 16. As a result, the weight of the constant voltage element in constant voltage control is eliminated, and the second stage voltage is set to a lower voltage.
Thereafter, control is continued at the second stage constant voltage.

As described above, according to this embodiment, the constant current circuit and the transistors constituting the constant current circuit are connected in a current mirror, and the circuit configuration has the function of changing the detection voltage 2 depending on the output compared with the mirror current. No adjustment is required for current detection when transitioning from the constant voltage charging function to the constant voltage charging function, making it possible to easily detect minute currents and eliminating the worry of malfunctions when changing the control voltage. , two adjustment settings for control pressure can be made with high accuracy without adjustment.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing the configuration of a charging control circuit in a second embodiment of the present invention.

In FIG. 2, reference numerals 21, 25, and 30 are constant voltage diodes, which correspond to the constant voltage elements in FIG.

Reference numeral 26 is a comparator with a hysterinsing function to ensure the switch function. 23.24 is ratio, ii! This is a feedback element for two devices 11. 29 is a transistor as a switching element, 22 is a bias resistor -27 of the constant voltage diode 26,
Reference numerals 28 denote a base resistance and a base-emitter resistance of the transistor 29, respectively.

The configuration differs from the one shown in Figure 1 in that the two voltage setting switching elements are non-contact type, the addition of porium 31 to improve output voltage accuracy, and the addition of two comparators and one reference voltage. The main point is that the comparator 26 has a hysteresis function.

With the above configuration, an inexpensive, small, and lightweight floating bonding element,
By omitting the elements that generate the terence voltage, a compact, lightweight, and low-cost charger can be made. Comparator 26
By providing a hysteresis function to the battery 2o, the voltage setting can be smoothly switched, and it is possible to deal with any situation regarding the initial state of charge of the battery 2o being charged.

Therefore, if the circuit shown in Figure 2 is used, it will be small and lightweight.

It becomes possible to realize a charging control circuit with low cost and low charging operation.

Note that although the constant voltage element 17 is used in the first embodiment, it may be a resistance element.

In addition, although transistors 6 and 7 were made bipolar type, FI
It may be a voltage controlled type using an ET or a vacuum tube.

Further, although the constant voltage elements 21, 25 and 30 in FIG. 2 are Zener diodes, it goes without saying that they may have an alternative voltage generating function.

Effects of the Invention As described above, the present invention includes a stationary pressure control circuit, a charging control transistor controlled by the stationary pressure control circuit, and a current detection transistor connected to the charging anatomy transistor in a current mirror manner.

The charging control circuit is operable to compare the output current of the current detection transistor with a predetermined value, and to switch the output suitable voltage of the constant voltage control circuit into at least two stages according to the comparison result. This eliminates the need for any adjustment in current detection when transitioning from the first stage of constant voltage charging to the second stage of constant voltage charging, making it possible to easily detect minute currents and making it easier to control voltage transitions. This makes it possible to realize an excellent charging control circuit that eliminates the worry of malfunctions during battery life and improves the precision of the two voltage settings of the control layer pressure without adjustment.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a charging control circuit in a first embodiment of the present invention, and FIG. 2 is a diagram of a second embodiment f! of the present invention. FIG. 3, a schematic diagram of the charging control circuit in AI, is a configuration diagram of a conventional charging control circuit. 1...- is the source, 6, 7.9......transistor. 11.14... Comparator, 16... Switch element. 2Q...Rechargeable battery.

Claims (1)

[Claims] A constant voltage control circuit, a charging control transistor controlled by the constant voltage control circuit, and a current detection transistor connected to the charging control transistor in a current mirror, and comparing the output current of the current detection transistor with a predetermined value. The charging control circuit is characterized in that it operates to switch the output voltage of the constant voltage control circuit in at least two stages depending on the comparison result.