DD221040A1 - CIRCUIT ARRANGEMENT FOR CHARGING BATTERIES - Google Patents

Abstract

The invention relates to a circuit arrangement for charging batteries, which ensures a constant current charge and selectively lowers the charging current or switches off when reaching the predetermined temperature-compensated voltage limit. According to the invention, the circuit arrangement consists of two operational amplifiers, which are connected to light emitting diodes as reference and display elements and resistors to the circuit.

Description

Field of application of the invention

The invention relates to a circuit arrangement for charging batteries with a constant current until reaching a predetermined voltage limit.

Characteristic of the known technical solutions

There are known according to DD-WP 99892 and DE-OS 2165215 circuit arrangements for charging batteries, in which by a circuit constructed of discrete components after reaching a predetermined voltage limit, the further charge is carried out with a constant voltage.

The disadvantage of these known circuit arrangements is the use of reverse current diodes as necessary components of the circuits. Since the forward voltage of these reverse current diodes is current-dependent, the predetermined voltage limit value can not be kept exactly constant. The thus possible low overload can already lead to bulging of the battery case, for example, in gas-tight Pb batteries.

It is also known from DE-OS 2992894 a circuit arrangement for charging batteries, in which taken with great circuit complexity, the reference voltage for the switch-off voltage from the supply voltage and automatically switched off after reaching the predetermined voltage limit of the charging current.

With this known circuit arrangement but no constant current charge can be achieved; It is therefore intended for the snow load of batteries.

There are already known according to DE-OS 2934302.3020959 and 3106171 circuit arrangements for charging batteries, in which the reference voltage is also supply voltage dependent and another charge with constant current or switching off the charger after reaching the predetermined voltage limit occurs.

However, these known circuit arrangements require a high component cost for the required modules.

Object of the invention

The object of the invention is to avoid both damage to batteries and chargers while avoiding the cited disadvantages when charging batteries as well as to reduce the component cost of the required circuitry and thus save costs and increase the reliability during charging. Explanation of the essence of the invention

The invention has for its object to develop a circuit arrangement for charging batteries, which ensures a reliable automatic charging of the batteries, after reaching a predetermined voltage limit with the same circuit basic structure either another charge with a constant voltage or switching off the charging current makes and thus a permanent connection of the charger with the battery allows and signals the respective operating condition. ,

-2- 257985 3

This object is achieved according to the invention as follows:

As circuit components, two operational amplifiers, preferably as an integrated double operation amplifier, are provided. "- '' "'.'.''/. · '..' · "., '':".-;';'..'.

The inputs of an operational amplifier are connected to a resistor connected in series with the battery as a sense resistor and a constant voltage element, preferably a light emitting diode. In this case, the non-inverting input of the operational amplifier is connected to the cathode of the light-emitting diode. Their anode and one terminal of the sensing resistor are at the positive supply voltage. The inverting input of the operational amplifier is connected via a further resistor as a series resistor to the other terminal of the sensing resistor and is connected to the positive terminal of the battery. About a diode as a protective diode, the output of the operational amplifier at the negative pole of

'Battery.-' ¹ V; - "- ^; V-" VV i ^v -v \: .. V - - "-. ^:: -: -" / '' V -...; '.- ";./' of the other operational amplifier is at a position parallel to the battery voltage bridge circuit of linear and nichtlinaaren components, preferably Resistors in one and a resistor and a constant voltage element, preferably a light emitting diode, arranged in the other bridge branch., The non-inverting input of the operational amplifier with the center of one and the inverting input, with or without an intermediate resistance as a series resistor, with the center of the other bridge branch connected.

From the output of this operational amplifier, preferably in series with this, a signal generator, preferably a light emitting diode, is connected.

The two operational amplifiers are connected to one another, wherein the first operational amplifier is connected with its inverting input via the light-emitting diode to the output of the second operational amplifier.

Between the cathode of the protection diode and the zero potential, a further resistor is preferably arranged.

Between the light emitting diode at the output of the second operational amplifier and its non-inverting input, a resistor is preferably also arranged.

Between the output of the first operational amplifier and the protective diode is preferably a light emitting diode

arranged. ';'^;

The circuit construction according to the invention applies to operational amplifiers with npn end transistors; when using pnp end transistors, the other components are to be arranged with opposite polarity.

The light-emitting diode on the first operational amplifier is fed via a series resistor and also serves as switch-on control for the charger. The operational amplifier compares the forward voltage of the light emitting diode with the voltage drop across the sense resistor through which the charging current flows and regulates this to a constant value.

The total resistance of the bridge circuit is so high that its power consumption is on the order of magnitude of the self-discharge current of the battery. The use of the light emitting diode in the bridge circuit as a reference standard allows for the compensation of the temperature coefficient of the gassing voltage of a gas-tight Pb battery in the range of -10 to + 40 ° C at currents around 5 / u.A. Their forward voltage of 1.2 to 1.3 V allows the charging of individual Pb or NC

Batteriezelleh. ''.''''""":''.V--''''' '  '.'

If the battery voltage exceeds the predetermined voltage limit during charging, the second operational amplifier switches on the associated LED. The inverting input of the first operational amplifier is thereby set to ground potential and the charging current is blocked.

By the associated further resistance, a hysteresis for the reconnection of the charging current can be set

become. '. '. ··. . ''A ^: .. · :. \ · ..- .- ' . · _ · _; · '. '

Resistance between the cathode of the protection diode and the zero potential allows a trickle charge when the charging current is switched off.

To display "charging current flows" is the LED between the output of the first operational amplifier and the protection diode.

The bridge circuit is powered by the battery itself, this results in a largely independent of the supply voltage cut-off.

With the circuit arrangement according to the invention, the object of the invention is fully achieved. The component cost is lowered and ensures a maintenance-free and. Betriebssichere charge of batteries.

embodiment

The invention will be explained in more detail below using an exemplary embodiment. The accompanying drawing shows the circuit diagram of the circuit arrangement according to the invention.

The circuit arrangement for a battery B consists of the operational amplifiers OVI and OV2 with open-collector outputs, the light-emitting diodes D 1, D 2, D 4 and D 5, the light-emitting diodes D1 and D4 being red GaAsP diodes with a wavelength of 660 nm, the protection diode D3 and the resistors R1 to R11, wherein instead of the resistor R7, a thermistor is arranged and the adjustment voltage R5 is set, the shutdown voltage.

With battery B connected and a charging voltage U ₁ below the cut-off voltage U _a , the input 5 is positive with respect to the input 4 and the output 6 is blocked by the operational amplifier 0V2. In this case, the operational amplifier OV1 operates as a constant current source and regulates U _R3 = U ₀₁ . Due to the good constancy of the forward voltage of the red LED D1 results in a very stable charging current. The LED D1 signals at the same time "charger switched on".

The light-emitting diode D4 works only as a constant voltage element without light emission. If the battery voltage rises to U _L > U _a , the input 5 becomes negative with respect to the input 4 and the output 6 of the operational amplifier OV2 becomes conductive and blocks the output 8 via the input 2 of the operational amplifier OV1. Thus, the charging current is switched off and the LED D5 signals "battery charged".

With the light-emitting diode D4 and the thermistor R7, the temperature coefficient of the gassing voltage of gas-tight lead acid batteries

be compensated in the range of -10 to + 4O ⁰ C.

Without the resistor RIO the charging current is lowered so far that U _L = U _{a is} constantly maintained, with the resistor R10, the necessary hysteresis from switching off until the power is turned on again.

Through the resistor R4, a trickle charge is carried out when the charge current is switched off.

Claims (6)

-1- 257 985   - -: · * ..... , ,; ".." .. ".. Invention claims: 1. A circuit arrangement for charging batteries with a constant current until reaching a predetermined voltage limit, characterized in that as a circuit component two operational amplifiers (OV1; 0V2), preferably as an integrated Doppeloperationsverstärker are provided, wherein the one operational amplifier (OV1) with one in series with the resistor (R3) connected to the battery (B) is connected as a sense resistor and a constant voltage element, preferably a light emitting diode (D 1), such that the noninverting input (1) of the operational amplifier (OV1) is connected to the cathode of the light emitting diode (D 1) in Connection is., The anode of the light emitting diode (D 1) and the one terminal of the resistor (R 3) are at the positive supply voltage, the inverting input (2) of the operational amplifier (OV1) via a resistor (R 2) as a series resistor with the connected to the other terminal of the resistor (R 3) and is at the positive terminal of the battery (B) and the output ( B) of the operational amplifier (OVD via a diode (D3) as a protective diode at the negative terminal of the battery (B), the other operational amplifier (0V2) at a lying parallel to the battery voltage bridge circuit of linear and non-linear components, preferably resistors (R5; R6; R7) is arranged in one and a resistor (R8) and a constant voltage element, preferably a light emitting diode (D4), in the other bridge branch, such that the non-inverting input (5) of the operational amplifier (0V2) with the center of the one and the inverting input (4) of the operational amplifier (0V2), with or without an intermediate resistor (R9) as a series resistor, connected to the center of the other bridge branch, at the output (6) of the operational amplifier (0V2), preferably in series with this, a signal generator, preferably a light-emitting diode (D5) is connected and the two operational amplifiers (OV11; 0V2) are connected to one another such that the output (6) of the operational amplifier (0V2) is connected via the light-emitting diode (D5) to the inverting input (2) of the operational amplifier (0V1). 2. Circuit arrangement according to item 1, characterized in that preferably between the cathode of the protective diode (D3) and the zero potential, a resistor (R4) is arranged. 3. Circuit arrangement according to item 1 and 2, characterized in that preferably between the light emitting diode (D 5) and! the non-inverting input (5) of the operational amplifier (0V2), a resistor (R 10) is arranged. 4. Circuit arrangement according to item 1 to 3, characterized in that preferably between the output (8) of the operational amplifier (OV1) and the protective diode (D3) a light-emitting diode (D2) is arranged. 5. Circuit arrangement according to items 1 to 4, characterized in that operational amplifiers (OV1; 0V2) are used with npn-end transistors. 6. Circuit arrangement according to item 1 to 4, characterized in that in operational amplifiers (OVI; OV2) with internal or discrete pnp-end transistors, the other components are arranged with reversed polarity. For this 1 page drawings _: