CN2794005Y

CN2794005Y - Under-voltage protecting circuit for battery

Info

Publication number: CN2794005Y
Application number: CN 200520057923
Authority: CN
Inventors: 李达华; 廖大慈
Original assignee: MEIGU ELECTRONIC (SHENZHEN) CO Ltd
Current assignee: MEIGU ELECTRONIC (SHENZHEN) CO Ltd
Priority date: 2005-04-28
Filing date: 2005-04-28
Publication date: 2006-07-05
Anticipated expiration: 2015-04-28

Abstract

The utility model relates to under-voltage protecting circuit for batteries, which aims to solve the problem that the existing under-voltage protecting circuit can not accurately judge the time for switching off loads. The utility model is characterized in that a control unit sends out a first control signal to an electronic switch at specified intervals, so that the electronic switch recovers to a closed state after instantaneous switching off; in the meantime, a tank circuit provides casual electric energy for the loads, so that the loads can not shut down for waiting the starting again under energization for the next time. Meanwhile, a voltage detect circuit detects the voltage of a battery during the instantaneous switching off; then the control unit judges whether the voltage of the battery is lower than an index value or not during the instantaneous switching off; if so, the control unit sends out a second control signal to permanently switch off the electronic switch; or else the control unit successively sends out the first control signal at the specified interval. The utility model has the advantages that the voltage detected by the voltage detecting circuit is the voltage when the loads are switched off, so the most proper time to switch off the loads can be judged more accurately.

Description

The battery under-voltage protection circuit

Technical field

The utility model relates to battery protecting circuit, more particularly, relate to a kind of can be when cell voltage be lower than predetermined value the battery under-voltage protection circuit of disconnecting consumers.

Background technology

In medium-to-high grade automobile, power consumption equipments such as sound equipment, air-conditioning all are housed usually, what have also is equipped with car refrigerator (normally adopting the small refrigerator of semiconductor refrigerating).When automobile is in when starting state, these power consumption equipments do not need automobile storage battery to provide power supply for it, can not cause what influence to storage battery.Yet when automobile is in when not starting state then need be by storage battery power supply, if continue to use these equipment, may be with exhaustion of the accumulators, its consequence is when needs start automobile, owing to the battery electric quantity deficiency, engine can't start up the car.As seen, corresponding protection circuit need be set, when cell voltage drops to suitable degree, automatically shutting down these power consumption equipments, thereby guarantee that battery electric quantity is not depleted.

For realizing this purpose, normally detect cell voltage in the prior art by a voltage detecting circuit, when cell voltage is lower than predetermined value, then disconnect the electronic switch that is connected between battery and the load.Yet detected in this method is the load terminal voltage of load when in running order, rather than real cell voltage, and have this moment:

U _Battery=I* (R+r1+r2),

U _Load=I*R,

Wherein, U _BatteryBe the open circuit voltage of battery, U _LoadTerminal voltage during for loaded work piece, detect the circuit of gained, the electric current when I is work, R are load resistance, and r1 is the internal resistance of cell, and r2 is for connecting conductor resistance and contact resistance sum.

At automobile, the voltage U of actual detected gained _LoadMay be than real battery open circuit voltage U _BatteryLow 0.5V even more, and can be connected contact resistance that conductor length, bad contact produce etc. and influence, thereby cause detecting exactly cell voltage, when disconnecting consumers is optimum also just can't accurately to judge Ying Yu.Need battery-powered power consumption equipment for other, also have this problem.

The utility model content

At the above-mentioned defective of prior art, the utility model will solve existing battery under-voltage protection circuit can not accurately judge the when only problem of disconnecting consumers of Ying Yu.

For solving the problems of the technologies described above, the utility model provides a kind of battery under-voltage protection circuit, comprises the voltage detecting circuit that is used to detect cell voltage, and the electronic switch that is used to control the break-make between battery and the load; Also comprise a clock circuit that is used for clocking, and a control unit that is connected with described voltage detecting circuit, electronic switch and clock circuit; Wherein, described control unit can send first control signal to described electronic switch by predetermined space, revert to closure state again after making the instantaneous disconnection of described electronic switch, described voltage detecting circuit can detect the cell voltage of instantaneous off period, if the cell voltage of described instantaneous off period is less than predetermined value, then described control unit can send the permanent shut-down of second control signal with described electronic switch.

In battery under-voltage protection circuit of the present utility model, preferably set up an accumulator that is used for providing for described load interim electric energy at the electronic switch off period.

In battery under-voltage protection circuit of the present utility model, can be by two divider resistance R1, R2, a little process chip U1, a crystal oscillator X1, and corresponding peripheral cell constitutes described voltage detecting circuit, control unit and clock circuit; And by constituting described accumulator with the storage capacitor C5 of described load parallel connection and/or the energy storage inductor L2 that connects with described load; Described electronic switch is connected between described accumulator and the battery, being connected between described load of closure/disconnection simultaneously and accumulator and the described battery.

By such scheme as can be seen, the utlity model has following advantage:

(1) make the instantaneous disconnection of electronic switch recover closed again by first control signal, thereby make voltage detecting circuit detect gained be disconnecting consumers the time voltage, the open circuit voltage of battery just, when disconnecting consumers is optimum can to judge Ying Yu in view of the above more accurately.

(2) at the instantaneous off period of electronic switch, can make it to remain on non-off-position by accumulator for load provides interim electric energy, do not wait for when switching on starting up again and can not shut down next time.

(3) when the cell voltage that detects gained is lower than predetermined value, can disconnect electronic switch, just disconnecting consumers by second control signal; When voltage recovers just often, but auto-closing electronic switch is again just connected load.

Description of drawings

The utility model is described in further detail below in conjunction with drawings and Examples, in the accompanying drawing:

Fig. 1 is the schematic diagram of the battery under-voltage protection circuit in preferred embodiment of the utility model;

Fig. 2 is the workflow diagram of battery under-voltage protection circuit in preferred embodiment of the utility model;

Fig. 3 is the circuit diagram of the battery under-voltage protection circuit in preferred embodiment of the utility model;

Fig. 4, Fig. 5, Fig. 6 are the waveform schematic diagrames of cell voltage, control signal and load voltage in preferred embodiment of the utility model.

Embodiment

In preferred embodiment of the utility model, the principle of battery under-voltage protection circuit as shown in Figure 1.Comprising: be connected in battery 100 two ends, be used to detect the voltage detecting circuit 102 of cell voltage, be connected between battery 100 and the load 112, be used to control the electronic switch 110 of the break-make between battery and the load, the clock circuit 106 that is used for clocking, the control unit 104 that is connected with voltage detecting circuit, electronic switch and clock circuit, and the accumulator 110 that is used for providing for load interim electric energy at the electronic switch off period.

Battery under-voltage protection circuit shown in Figure 1 can be by works shown in Figure 2.Wherein, in step 201, control unit 104 can send first control signal to electronic switch by predetermined space, reverts to closure state again after making electronic switch 108 instantaneous disconnections.At the instantaneous off period of electronic switch, accumulator 110 can be load interim electric energy is provided, and makes it to remain on non-off-position, that is to say to be worked on by the interim electric energy that accumulator provides, and does not wait for when switching on starting up again and can not shut down next time.

In step 202, voltage detecting circuit 102 can detect the cell voltage U of instantaneous off period _Battery

In step 203, control unit 104 can be judged the cell voltage U of this instantaneous off period _BatteryWhether less than pre-voltage U _{Predetermined}If be not less than then return step 201.

If U _Battery＜U _{Predetermined}, then in step 204, control unit can send second control signal, with the electronic switch permanent shut-down.

In step 205, after the permanent disconnection of electronic switch, voltage detecting circuit 102 can continue to detect cell voltage U _Battery

In step 206, control unit 104 can be judged this cell voltage U _BatteryWhether less than pre-voltage U _{Predetermined}If, U _Battery＜U _{Predetermined}, then return step 205.

If U _BatteryNo longer less than U _{Predetermined}, its reason may be because changed battery, battery has been finished charging make its voltage recover normal, then stops to send second control signal, makes electronic switch 108 revert to closure state, gets back to step 201 then, the circulation abovementioned steps.

Be illustrated in figure 3 as the circuit diagram of battery under-voltage protection circuit in preferred embodiment of the utility model.This circuit is applicable to the battery of 12V voltage.Wherein, by two divider resistance R1, R2, a little process chip U1, a crystal oscillator X1, and voltage detecting circuit, control unit and the clock circuit shown in the corresponding peripheral cell pie graph 1.In the present embodiment, provide 5V stabilized voltage power supply for little process chip U1 by voltage stabilizing chip U2.Cell voltage is input to the 8th pin of little process chip U1 after resistance R 1, R2 dividing potential drop, finish contrast with predetermined voltage in inside by little process chip U1, and according to comparing result output control signal corresponding.

As can be seen from Figure 3, wherein form electronic switch by triode Q2, Q1 and metal-oxide-semiconductor Q3 and corresponding resistance R 5, R6, R7.When the 18th pin of little process chip U1 is exported high level, the Q2 conducting, Q1 ends, thereby makes the Q3 conducting, and load MD1 can form complete loops through Q3 and battery, be equivalent to electronic switch and handle closure state.When the 18th pin output low level of little process chip U1, Q2 ends, the Q1 conducting, thus Q3 is ended, load MD1 can not form complete loops with battery, is equivalent to electronic switch and handles off-state.

As can be seen from Figure 3, wherein constitute accumulator by storage capacitor C5, energy storage inductor L2 and diode D2.During powered battery, electric current flows inductance L 2 and capacitor C 5 stored energys through anode, load, inductance L 2, metal-oxide-semiconductor Q3 to battery cathode.When electronic switch disconnected, capacitor C 5 was to load discharge, and to the load afterflow, both send the energy of its storage to load to inductance L 2 simultaneously through diode D2 simultaneously., when specifically implementing, should select to send the interval of first control signal and the width of signal itself according to the load and the accumulator of reality, in this enforcement, send be spaced apart 4 seconds of first control signal, 25 milliseconds of instantaneous opening time.

Described electronic switch is connected between described accumulator and the battery, being connected between described load of closure/disconnection simultaneously and accumulator and the described battery.

As can be seen from Figure 3, wherein also be provided with the LED light L1 in parallel with load, it is used to indicate load whether to be in the energising operating state.

In preferred embodiment of the utility model, the control signal that cell voltage, control unit sent that voltage detecting circuit is measured and the waveform of the voltage in the load are respectively as Fig. 4, Fig. 5, shown in Figure 6.

Simulated the situation that cell voltage reduces gradually among Fig. 4, dotted line wherein is predefined threshold value.

As can be seen from Figure 5, the normal signal of control unit is a high level, and when cell voltage was not less than predetermined voltage, control unit can send low level pulse by predetermined space, i.e. first control signal; When cell voltage during less than predetermined voltage, control unit can transfer low level to by high level, i.e. second control signal.

As can be seen from Figure 6, send low level pulse with the electronic switch off period at control unit, because the effect of accumulator, the voltage in the load can directly not reduce to zero, can supply its voltage that works on and can maintain one; When electronic switch reverted to closure state, it is normal that the voltage of load can recover.

Battery under-voltage protection circuit of the present utility model can be used for automobile storage battery is protected, and also can be used for other and adopts battery powered apparatus.In order not disturb the operate as normal that is connected in other power consumption equipments on the same battery; preferably this battery under-voltage protection circuit is built in air conditioner, stereo set or car refrigerator respectively; thereby make electronic switch only disconnect the power consumption equipment at its place, and all power consumption equipments that can not be connected with battery (for example anti-thefting monitoring equipment on the automobile) all disconnect.

Claims

1, a kind of battery under-voltage protection circuit comprises the voltage detecting circuit that is used to detect cell voltage, and the electronic switch that is used to control the break-make between battery and the load; It is characterized in that,

Also comprise a clock circuit that is used for clocking, and a control unit that is connected with described voltage detecting circuit, electronic switch and clock circuit;

Wherein, described control unit can send first control signal to described electronic switch by predetermined space, revert to closure state again after making the instantaneous disconnection of described electronic switch, described voltage detecting circuit can detect the cell voltage of instantaneous off period, if the cell voltage of described instantaneous off period is less than predetermined value, then described control unit can send the permanent shut-down of second control signal with described electronic switch.

2, battery under-voltage protection circuit according to claim 1 is characterized in that, also comprises an accumulator that is used for providing for described load at the electronic switch off period interim electric energy.

3, battery under-voltage protection circuit according to claim 2 is characterized in that,

Wherein by two divider resistance R1, R2, a little process chip U1, a crystal oscillator X1, and corresponding peripheral cell constitutes described voltage detecting circuit, control unit and clock circuit;

And by constituting described accumulator with the storage capacitor C5 of described load parallel connection and/or the energy storage inductor L2 that connects with described load;

4, battery under-voltage protection circuit according to claim 3 is characterized in that, also comprises the LED light in parallel with described load.