WO2010080017A1

WO2010080017A1 - Low-complexity electronic protection circuit for avoiding over-discharge of automotive batteries

Info

Publication number: WO2010080017A1
Application number: PCT/MX2009/000130
Authority: WO
Inventors: Jesús Ezequiel MOLINAR SOLIS
Original assignee: Universidad Autónoma Del Estado De México
Priority date: 2009-01-09
Filing date: 2009-12-07
Publication date: 2010-07-15
Also published as: MX2009000339A

Abstract

This patent provides an electronic protection circuit which avoids over-discharge of automotive batteries and guarantees that the latter store at least the minimum charge necessary for restarting the vehicle. The function of said circuit is to disconnect the battery when, as a result of current consumption, the latter is slowly discharged below the safety charging level, and thus provides the minimum current necessary for the car to always start. The electronic circuit has an electromechanical relay connected between the positive pole of the battery and the car ignition system. The above is effected specifically when the car is switched off, thus avoiding over-discharge of the battery.

Description

LOW COMPLEXITY ELECTRONIC PROTECTION CIRCUIT TO PREVENT OVERDOWN OF AUTOMOTIVE BATTERIES

FIELD OF THE INVENTION

Automotive industry, specifically in the part of the electrical system.

OBJECT OF THE INVENTION

This circuit provides a solution of low complexity to the problem that occurs in gasoline cars when they are overcharged for some reason causing the car can not start again. It is common, that by default of the user, some device that consumes energy such as lights, stereo or other device is left in operation and eventually this discharges the battery below the minimum charge level necessary for the car to start again, it is say, it is "over-downloaded." The protection circuit of the present invention prevents such a situation from taking place. Said circuit monitors the battery charge in such a way that if it is discharged, when it reaches a minimum level of charge necessary for the vehicle to start again, the circuit will disconnect everything that consumes energy to ensure said minimum charge in the battery and thus, the vehicle may eventually restart. The proposed circuit is of low complexity so it can be developed as an accessory item that could be installed in any car.

BACKGROUND

There are currently several options to deal with the problem of total or partial discharge of the battery in a car. There are the common "pass cables current "which through the proper connection of another vehicle's battery to the discharged battery, the latter is provided with the necessary charge to start the vehicle again. Another option is to have an" extra "emergency battery which It is intended to replace the one that is discharged. There are currently several patents registered as in the case of the United States, of which a control system is offered that when the battery charge reaches the critical level, automatically said The system partially disconnects the electric charge of the vehicle, which is not the case with the control system itself, although the energy consumption of such a control system is well below the consumption of the lighting system or the stereo system, to name a few. , after days or weeks the consumption of the control circuit will end the minimum load that was intentionally stored to turn on the ve hicle again.Example of the above are the following patents: US 5,200,877; US 6,424,511; US 4,493,001; US 5,272,380. Other patents refer to the use of sophisticated microcontrollers that allow them to monitor additional variables to the battery charge itself. However, the complexity of these solutions grows enormously making it difficult to install such systems, such is the case of patents: US 6,646,845; US 5,315,228. In addition, this type of proposed system prevents the production of a universal protection accessory that can be used by any vehicle. Other solutions suggest the use of several electromechanical relays to cut off the current from the battery. In this situation, it is known that such devices have very low impedance in the winding that controls the switch, which causes the part that controls the relay to demand a lot of current, approximately 12OmA. If the proposed solution requires several relays Electromechanical with these characteristics, the exclusive consumption of such devices can cause the battery to discharge even without other more demanding current devices being turned on, such is the case of US 5,327,068. US Patent 7,166,990 is perhaps the most compact of the aforementioned, however, it has several shortcomings. While the battery charge is monitored with the battery voltage itself, (if the charge decreases so does the battery voltage) this input voltage signal passes through a voltage divider to attenuate that signal, this through two resistors and then to a voltage comparator. Such a situation means that the excursion that the battery voltage might have is also attenuated through said voltage divider. Example, if the battery voltage decreases 0.5 V across the splitter, only a fraction of that value will change depending on the values of both resistors. This reduction in signal excursion makes the circuit more sensitive to noise induced by the motor itself or other auxiliary circuits of the vehicle itself. In this same patent, a commercial integrated circuit is suggested for the voltage comparator block, the S-808/9 from Seiko Instrument that acts as a voltage detector. This device has a fixed reference voltage and its maximum operating voltage is 7V, in said patent it is not specified how the required power is provided to said device. Another important point is the reference to the electromagnetic switch used to cut the charge to the battery, the one suggested in this work, the OMRON "Reset Rocker Switch A8G" only has the capacity for 2OA of current. Normally any compact vehicle requires much greater current to start the engine, that is, 50-70 A. In addition, said switch requires 185mA in the winding of control which makes it a device of relatively high consumption and that eventually this only device could discharge the battery in several days. Thus, the objective of the present invention is to overcome the disadvantages of the above proposals and propose a solution of low complexity and low energy consumption that allows the development of an accessory that can be easily installed to any vehicle.

The present patent, unlike the aforementioned ones, incorporates a voltage regulator, which allows the excursion of the battery voltage to be the same as that at the input of the voltage comparator and also that said voltage is adjustable. A notable difference is that it uses a single NMOS transistor as a voltage comparator and a single electromechanical relay to cut the total current from the battery.

BRIEF DESCRIPTION OF THE FIGURES For the explanation of the present invention the following drawings will be used, of which: Figure 1 is a simplified diagram of the proposed concept, which includes the car battery and the essential parts of the protection circuit. Figure 2 Describes the protection circuit with all commercial components in detail.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figure 1, the car battery denoted by 101 is connected through the parallel switches 105 and 106, to the engine ignition system, 107 and to the blocks that make up the control circuit 102, 103 and 104 In the beginning, 106 must be in its closed state, this allows node V _{A to} reach 12V from the battery, 102 is a variable voltage V ₁ that is subtracted from that in V _A so that Vj _n = V _A -V ₁ . Block 103 is a low pass filter whose time constant is given by the product τ = RC. This low pass filter is necessary since when the vehicle turns on, due to the large amount of current demanded by the engine ignition system, the voltage in the battery instantly decreases well below any level of safety, evidently in these circumstances the circuit of protection should not pass to its state of activity. In this case, the low pass filter makes Vj _n insensitive to abrupt changes in battery voltage, V _A - In the case when the engine is off and some device demands a small current, the battery voltage across minutes will decrease due to the electric shock. That is, the battery voltage is proportional to the amount of charge that is stored in the latter. The discharge process by a small current is slow and the voltage drop in the battery caused by that current is what the protection circuit must detect. Thus, Vi _n should only be affected by very gradual changes of V _A through the low pass filter. The voltage comparator 104 is the part that verifies the battery safety voltage, this through the comparison of Vj _n with a reference voltage V _ref . In this way, the minimum charge on the battery to start the vehicle is guaranteed. Example.- if the battery voltage is V _A = 12V and

if the reference voltage is V _ref = 4.7V, the comparator is activated since Vi _n > V _ref . In this way, the comparator closes the switch 105 and since it is closed, the switch 106 must be opened manually to start the protection circuit that will be explained below. If the motor shuts down and the battery voltage V _A begins to decrease slowly due to some device that consumes current, Vj _{n will} decrease in the same proportion due to V ₁ . Example.- If the battery voltage V _A has decreased from 12V to 11.6V and since V ₁ = TV, the voltage V _in = V _A -V, = 4.6V and because 4.6V <V _ref (V ₁ * = 4.7V), the voltage comparator detects that the battery voltage has decreased below the safety voltage, which is simply VA _(m _n) ⁼ Vi + V _ref is , for this example 11.7V . Eventually the comparator will put 105 open, this in order to protect the battery so that it does not continue to discharge. If the protection has been activated, both 105 and 106 will be in an open state and this ensures that there is no battery current consumption. To start the vehicle, it is necessary to manually activate 106 and start the engine, the battery safety voltage, V _{A (m} i _n ), must ensure that it has at least enough charge to start the vehicle. Once the engine is started, the nominal voltage values of the battery are restored, 105 is activated and 106 must be manually put back into the open state, so that the battery protection is restored. Another function of the switch 106 is that in case the user wishes to disable the protection circuit, it is simply necessary to leave 106 permanently activated and in this way all activity of the protection circuit is canceled. Figure 2 shows the electrical diagram in more detail of the protection circuit, it can be seen that in this diagram the car battery is also denoted by 101. Said battery is connected to node V _A through the electromechanical relay 105 and of the manual switch 106. In this case the adjustable voltage Vi of Figure 1 is implemented through the voltage regulator 102 now in Figure 2, this is an adjustable negative voltage regulator LM337, with which, to set the output voltage V ₁ resistors R2 and Rl are necessary. Depending on the value of

Rl, which is a variable resistance, the voltage in V ₁ can take a value between 0 and 10.5V. Through any commercial diode Dl, in this case 1N4148, the voltage in Vi _n is established and through the values of R3 and Cl the filter discharge time constant can be defined, this, for any value considering τ = »R3 Cl. The voltage comparator is implemented by a simple commercial NMOS transistor, in this case the IRF610, 104. This NMOS transistor has a threshold voltage V _JH between 2 and 4 V so the reference voltage V internal _ref for this device will be between 2 and 12 V. Thus, by adjusting V ₁ , V _{A (m} in) ⁼ Vi + V _re f is complied with. In case the battery is discharged and V _A <V _A (min) then the condition in the transistor will be Vi _n <V _ref and in this case the transistor will stop passing current activating the safety, that is, putting the electromechanical relay 105 in the open state. The fact of using a simple NMOS transistor is important since said device in addition to being simple in its operation, does not depend on the positive rail, that is to say V _A and therefore is robust to the possible variations of the battery voltage. The electromechanical relay 105 used is Bitron 7MO 951 253 A, which has several important electrical characteristics that give the proposed circuit advantages over the patents described above. It is a normally open relay and has a control current of only 85mA and in addition, it can control up to 7OA at the output, (In US 7,166,990 the relay used consumes 185mA of control current and only supports 2OA at the output) this is , the current that goes from the battery 101 to the engine ignition system, 107. Finally, the switch 106 is a simple on-off button switch of 7OA. When 106 is activated manually and the vehicle is started, the voltage in V _A is automatically restored to its value nominal and therefore also Vi _n through Dl, which will activate 105. Thus, when the engine is started, 106 must be manually deactivated in order for the protection circuit to be restored.

Claims

CLAIMS Having described my invention sufficiently and clearly, I consider it a novelty and therefore claim as my exclusive property, the content of the following clauses:

1. Electronic circuit of protection of low complexity to avoid over-discharge of automotive batteries, characterized by a voltage regulator that allows the excursion of the battery voltage to be the same as the one of the voltage comparator at the input.

2. Low complexity electronic protection circuit to prevent over-discharge of automotive batteries, which according to the previous clause, allows the protection voltage to be adjustable through the resistances of the same voltage regulator.

3. Low complexity electronic protection circuit to prevent over-discharge of automotive batteries, which according to clause 1, contains a low pass filter, which allows the protection circuit to detect only gradual changes in the load of the battery

4. Low complexity electronic protection circuit to prevent over-discharge of automotive batteries, which according to clause 1, further characterized by an NMOS device that acts as a voltage detector and whose operation does not depend on the possible variations that could have the power, in this case, the battery voltage.

5. Low complexity electronic protection circuit to prevent over-discharge of automotive batteries, which according to clause 1, has a normally open relay device, which functions as a power switch that supplies or It cuts the current coming from the battery through the control circuit.

6. Low complexity electronic protection circuit to prevent over-discharge of automotive batteries, which according to clause 1, presents a series of components and a characteristic connection shown in figures 1 and 2 that aim to avoid over-discharge of car batteries.