Battery protecting circuit
[technical field]
The utility model relates to circuit design field, and particularly a kind of have the battery protecting circuit of self-recovering function after electric discharge overcurrent protection.
[background technology]
Fig. 1 shows a kind of structural representation of battery protecting circuit system.As shown in Figure 1, described battery protecting circuit system (such as, lithium battery) comprises battery battery core Bat, battery protecting circuit 110, charge power switch 130 and discharge power switch 120.Discharge power switch 120 and charge power switch 130 are series between the negative pole of battery battery core Bat and the negative pole BP-of battery successively, and the positive pole of battery battery core Bat is directly connected with the positive pole BP+ of battery.
Described charge power switch 130 comprises NMOS (N-channel Metal Oxide Semiconductor) field effect transistor M C and parasitizes the diode (not shown) in its body.Described discharge power switch 120 comprises nmos fet MD and parasitizes the diode (not shown) in its body.The drain electrode of nmos pass transistor MD is connected with the drain electrode of nmos pass transistor MC, and the source electrode of nmos pass transistor MD is connected with the negative pole of battery battery core Bat, and the source electrode of nmos pass transistor MC is connected with the negative pole BP-of battery.
Described battery protecting circuit 110 comprises three links (or being called test side) and two control ends; three links are respectively battery battery core anode connection terminal VCC; battery battery core negative pole link VSS and battery cathode link VM, two control ends are respectively charging control end COUT and control of discharge end DOUT.Wherein, link VCC is connected with the positive pole of battery battery core Bat; Link VSS is connected with the negative pole of battery battery core Bat; Link VM is connected with the negative pole BP-of battery; Charging control end COUT is connected with the control end of charge power switch 130, and be namely connected with the grid of nmos pass transistor MC, control of discharge end DOUT is connected with the control end of discharge power switch 120, is namely connected with the grid of nmos pass transistor MD.
Described battery protecting circuit 110 can carry out charge protection and discharge prevention to battery battery core Bat.Usual battery protecting circuit (or battery protection chip) 110 comprises overcharge voltage testing circuit 112, overcharge current testing circuit 114, overdischarge voltage detecting circuit 116, overdischarge current detection circuit 117, short-circuit detecting circuit (sign), control circuit 118 and overcurrent restore circuit 119.When there is not abnormality be connected with load or charger between the positive pole BP+ and negative pole BP-of battery after, the equal conducting of nmos pass transistor MC and MD, lithium battery normally carries out discharge and recharge.
Because metal-oxide-semiconductor conducting exists conducting resistance, so, when there is load between the positive pole BP+ and negative pole BP-of battery, discharging current can form pressure drop on nmos pass transistor MC and MD, discharging current is larger, voltage drop on nmos pass transistor MC and MD is larger, and namely link VM is larger relative to the voltage difference of link VSS.
Described battery protecting circuit 110 is by arranging overdischarge current detection circuit 117 and short-circuit detecting circuit (not shown) carries out two-stage overdischarge current protection.Described overdischarge current detection circuit 117 and short-circuit detecting circuit determine whether by the pressure reduction detected between link VM and VSS the overcurrent that discharges, usual link VSS is connected and ground connection with the negative pole of battery battery core Bat, therefore, the overcurrent that discharges can be judged whether by the voltage detecting link VM.Serve as discharging current testing circuit 117 and detected that the voltage of link VM higher than electric discharge overcurrent protection threshold value VEDI (such as, 80 ~ 200mV), and the duration is greater than over time of delay (such as, 12mS), then control nmos pass transistor MD by control circuit 118 to turn off, enter electric discharge overcurrent protection state (EDI) to make lithium battery; When short-circuit detecting circuit detects that the voltage of link VM higher than short-circuit protection threshold value VSHORT (such as; 1V); and the duration is greater than short-circuit protection time of delay (such as; 2 ~ 80us); then control nmos pass transistor MD by control circuit 118 to turn off, enter short-circuit protection state (SHORT) to make lithium battery.
After entering electric discharge overcurrent protection state, regular picture state can be returned to when external loading lightens to make lithium battery, overcurrent restore circuit 119 is also provided with in battery protecting circuit 110, the operation principle of this overcurrent restore circuit 119 is: after entering electric discharge overcurrent protection state, it can open from the drop-down path between link VM to VSS, attempt to drag down the voltage of link VM (alternatively, attempt the voltage of the negative pole BP-dragging down battery), once external loading lightens (overcurrent reason of namely discharging is eliminated), this drop-down path just can drag down the voltage of link VM, thus make battery recovery arrive regular picture state.
But the existing battery protecting circuit being provided with overcurrent restore circuit 119 in actual use, often can due to certain abnormal cause, and deadlock is in electric discharge overcurrent protection state.
Therefore, be necessary that the technical scheme proposing a kind of improvement is to overcome the problems referred to above.
[utility model content]
The purpose of this utility model is to provide a kind of battery protecting circuit, can overcome the Deadlock of electric discharge overcurrent protection state.And structure is simple, and cost is low.
In order to solve the problem; the utility model provides a kind of battery protecting circuit; it charging control end COUT comprising the link VM be connected with battery cathode, the link VSS be connected with battery battery core negative pole, the link VCC be connected with battery battery core positive pole, the control of discharge end DOUT be connected with the control end of discharge power switch and be connected with the control end of charge power switch, discharge power switch and charge power switch are connected between the link VM of battery cathode connection and the link VSS of battery battery core negative pole connection.Described battery protecting circuit also comprises control circuit and overcurrent restore circuit.Described overcurrent restore circuit comprises pull-up path and discharge path, and described discharge path comprises the first resistance, diode and the first switching device that are series between link VM and link VSS; Described pull-up path comprises and is series at second switch device between link VCC and link VM and the second resistance.After entering electric discharge overcurrent protection state, described control circuit controls second switch break-over of device, and the voltage of link VM is driven high, and forces to enter short-circuit protection state; After entering short-circuit protection state, described control circuit controls second switch device and turns off and the first switch device conductive.Described control circuit determines whether to exit short-circuit protection state according to the voltage of link VM, and after determining to exit short-circuit protection state, described control circuit controls the first switching device and turns off, the conducting of controlled discharge power switch.
Further, after entering electric discharge overcurrent protection state, while described control circuit controls second switch break-over of device, control the first switching device and turn off.
Further, as VEDI < VM < VSHORT, described control circuit controls battery and enters electric discharge overcurrent protection state; As VM > VSHORT; described control circuit controls battery and enters short-circuit protection state; wherein; VM is the magnitude of voltage of tie point VM, and VEDI is electric discharge overcurrent protection threshold value, and VSHORT is short-circuit protection threshold value; under electric discharge overcurrent protection state or short-circuit protection state; described control circuit controls described discharge power switch OFF, and after exiting electric discharge overcurrent protection state and short-circuit protection state, described control circuit controls described discharge power switch conduction.
Further, the negative electrode of described diode connects a link of described first switching device, the anode of described diode is connected with described battery cathode link VM, and another link of described first switching device is connected with described battery battery core negative pole link VSS.
Further, described discharge path provides milliampere rank and following electric current.
Further, under short-circuit protection state, when the voltage of link VM being detected lower than short-circuit protection voltage threshold, described control circuit is determined to exit short-circuit protection state.
Further, described first switching device is nmos pass transistor, and described second switch device is PMOS transistor.
The drive circuit of further described pull-up path multiplexing charging control end COUT.
Compared with prior art, the overcurrent restore circuit in battery protecting circuit of the present utility model can after battery enters electric discharge overcurrent protection state, and the voltage of the negative pole of pull-up battery, enters short-circuit protection state to force battery by overcurrent protection state of discharging; After electric discharge overcurrent reason is eliminated, the voltage of the negative pole of this overcurrent restore circuit down-drawable battery, exits short-circuit protection state to make battery; return to regular picture state; thus overcome the Deadlock of electric discharge overcurrent protection state, and this circuit structure is simple, and cost is low.
[accompanying drawing explanation]
In order to be illustrated more clearly in the technical scheme of the utility model embodiment, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only embodiments more of the present utility model, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.Wherein:
Fig. 1 is a kind of structural representation of battery protecting circuit system;
Fig. 2 its be the circuit diagram of the overcurrent restore circuit in Fig. 1;
Fig. 3 is the circuit diagram of the utility model overcurrent restore circuit of battery protecting circuit in one embodiment.
[embodiment]
For enabling above-mentioned purpose of the present utility model, feature and advantage become apparent more, are described in further detail the utility model below in conjunction with the drawings and specific embodiments.
Alleged herein " embodiment " or " embodiment " refers to special characteristic, structure or the characteristic that can be contained at least one implementation of the utility model.Different local in this manual " in one embodiment " occurred not all refers to same embodiment, neither be independent or optionally mutually exclusive with other embodiments embodiment.Unless stated otherwise, connection herein, be connected, word that the expression that connects is electrically connected all represents and is directly or indirectly electrical connected.
Please refer to shown in Fig. 2, it is a kind of specific implementation circuit of the overcurrent restore circuit in Fig. 1.This overcurrent restore circuit comprises and is connected to the first resistance R1, diode D1 between link VM and VSS and the first switching device SW1 successively, and wherein, the control end of the first switching device SW1 is connected with control circuit 118.
Described control circuit 118 determines whether electric discharge overcurrent or short circuit according to the pressure reduction between link VM and VSS; when electric discharge overcurrent or short circuit being detected; just control nmos pass transistor MD to turn off; so just enter electric discharge overcurrent protection state or short-circuit protection state; meanwhile; also control described first switching device SW1 conducting, like this, make the discharge path conducting between link VM and VSS.Usually, described control circuit 118 determines whether to exit electric discharge overcurrent protection state or short-circuit protection state according to the voltage of control end VM.
The course of work of the overcurrent restore circuit in Fig. 2 is specifically introduced below in conjunction with Fig. 1.
When outside have comparatively heavy load time, make VEDI < VM < VSHORT, described control circuit 118 judges electric discharge overcurrent, and it controls nmos pass transistor MD and turns off, and lithium battery enters electric discharge overcurrent protection state (EDI).Because nmos pass transistor MD is turned off, the voltage of link VM can be drawn high the voltage of the positive pole BP+ close to battery by external loading, at this moment, and VM > VSHORT (be equivalent to lithium battery and enter short-circuit protection state).When lithium battery enters electric discharge overcurrent protection state; control circuit 118 controls the first switching device SW1 conducting; thus produce from the drop-down path of link VM through the first resistance R1, diode D1 and the first switching device SW1 to link VSS; link VSS is made to provide a pull-down current to link VM; this pull-down current attempts the voltage dragging down link VM; once electric discharge overcurrent reason is eliminated, the voltage of link VM will be dragged down.
When external loading lightens (overcurrent reason of namely discharging is eliminated), the voltage of link VM can be pulled down to below short-circuit protection threshold value VSHORT by this pull-down circuit, and control circuit 118 judges to exit short-circuit protection state.After determining to exit short-circuit protection state, described control circuit 118 controls the first switching device SW1 to be ended, and makes the discharge path between link VM and VSS turn off like this, and prevents electric leakage; And control nmos pass transistor MD conducting, the voltage of link VM can be pulled down to rapidly voltage close to link VSS by nmos pass transistor MD, thus makes lithium battery exit short-circuit protection state, returns to regular picture state.
But the circuit shown in Fig. 2 exists a problem, due to the existence of diode D1, when (namely under Light Condition) after external loading removes, link VM can only be pulled down to a diode drop (about 0.7V) by overcurrent restore circuit.The electric discharge overcurrent protection threshold value VEDI of current most of battery protecting circuit 116 is at below 200mV, if (such as, unloaded lower control end DOUT mistake is shorted to VSS due to certain abnormal cause; During assembling battery; the first power-on error of protective circuit enters electric discharge overcurrent protection state or battery core micro-short circuit causes entering electric discharge overcurrent protection etc. by mistake); when link VM is in and is greater than electric discharge overcurrent protection threshold value VEDI and is less than the voltage between short-circuit protection threshold value VSHORT; lithium battery is in electric discharge overcurrent protection state; now; the voltage of link VM can not be pulled down to electric discharge below overcurrent protection threshold value VEDI by overcurrent restore circuit; thus deadlock is in electric discharge overcurrent protection state, can only by adding charger activated batteries.
The utility model improves the overcurrent restore circuit in the battery protecting circuit in Fig. 2.
Please refer to shown in Fig. 3 that it is the electrical block diagram of the overcurrent restore circuit in the utility model.Described overcurrent restore circuit comprises pull-up path 310 and discharge path 320.
Described pull-up path comprises and is series at second switch device SW2 between link VCC and link VM and the second resistance R2; Described discharge path comprises and is series at the first resistance R1, diode D1 between link VM and VSS and the first switching device SWI.Described control circuit 118 is connected with the control of second switch device SW2 with the control end of described first switching device SW1 respectively.
In one embodiment; after entering electric discharge overcurrent protection state; described control circuit 118 controls the first switching device SW1 and turns off and control second switch device SW2 conducting, to make pull-up path 310 conducting between link VCC and link VM, the voltage of link VM is driven high.Once the voltage of link VM exceedes short-circuit voltage protection threshold value VSHORT; battery will enter short-circuit protection state; that is; after battery enters electric discharge overcurrent protection state; pull-up path 310 in described overcurrent restore circuit, by drawing high the voltage of link VM, forces battery to enter short-circuit protection state by overcurrent protection state of discharging.After battery enters short-circuit protection state, described control circuit 118 controls second switch device SW2 and turns off and the first switching device SW1 conducting, to make discharge path 320 conducting between link VM and VSS, to attempt to drag down the voltage on link VM.If electric discharge overcurrent reason is eliminated, (such as, in the unloaded state), the voltage of link VM can be pulled down to below short-circuit protection threshold value VSHORT by this discharge path 320, and control circuit 118 judges to exit short-circuit protection state.When after determining to exit short-circuit protection state, described control circuit 118 controls the first switching device SW1 to be ended, and makes the discharge path between link VM and VSS turn off like this, and prevents electric leakage; And control nmos pass transistor MD conducting, the voltage of link VM can be pulled down to rapidly voltage close to link VSS by nmos pass transistor MD (discharge power switch), thus makes lithium battery exit short-circuit protection state, returns to regular picture state.
In another embodiment; after entering electric discharge overcurrent protection state; described control circuit 118 controls the first switching device SW1 and the equal conducting of second switch device SW2; to make pull-up path 310 conducting between link VCC and link VM; and the discharge path 320 also conducting between link VM and VSS, because the pull-down current of discharge path 320 when conducting is very low, be generally milliampere and with the electric current of subordinate; therefore, pull-up path 310 still can force the voltage drawing high link VM.Once the voltage of link VM exceedes short-circuit voltage protection threshold value VSHORT, battery will enter short-circuit protection state.After battery enters short-circuit protection state, described control circuit 118 controls second switch device SW2 and turns off.Discharge path 320 between link VM and VSS continues conducting, and it attempts to drag down the voltage on link VM.If electric discharge overcurrent reason eliminates (such as in the unloaded state), the voltage of link VM can be pulled down to below short-circuit protection threshold value VSHORT by this discharge path 320, and control circuit 118 judges to exit short-circuit protection state.When after determining to exit short-circuit protection state, described control circuit 118 controls the first switching device SW1 to be ended, and makes the discharge path between link VM and VSS turn off like this; And control nmos pass transistor MD (discharge power switch) conducting, the voltage of link VM can be pulled down to rapidly voltage close to link VSS by nmos pass transistor MD, thus makes lithium battery exit short-circuit protection state, returns to regular picture state.
In order to reduce power consumption, under electric discharge overcurrent protection state, the pull-down current flowing to link VSS from link VM is very little, for milliampere and with the electric current of subordinate, can be regulated the size of described pull-down current by the size arranging the first resistance R1.
The negative electrode of diode D1 connects a link of described first switching device, and described anode is connected with link VM, and another link of described first switching device is connected with link VSS.Diode D1 is used for allowing link VM to link VSS one-directional flow electric current, stops link VSS to leak electricity to VM, and utilizes the reverse voltage endurance capability of diode D1 at VM voltage lower than most of pressure drop of bearing link VSS to VM during VSS voltage.First resistance R1 also can be positioned between the first switching device MN1 and diode D1, can also be positioned between the first switching device MN1 and link VSS.
In embodiment shown in this Fig. 3, described first switching device SW1 is NMOS (N-channelMetal Oxide Semiconductor) transistor, and described second switch device SW2 is PMOS (P-channel Metal Oxide Semiconductor) transistor.In another embodiment, described first switching device SW1 and second switch device SW2 also can be PMOS transistor or nmos pass transistor.Or described first switching device SW1 and second switch device SW2 can be the switching device of other types.
It should be noted that described pull-up path 310 can other circuit in multiplexing battery protecting circuit 110, such as, described pull-up circuit can the drive circuit of multiplexing charging control end COUT, thus can save chip cost.
In sum, overcurrent restore circuit in the utility model comprises pull-up path 310 and discharge path 320, it after battery carries out electric discharge overcurrent protection state, by the voltage of pull-up path 310 pull-up link VM, can enter short-circuit protection state to force battery by overcurrent protection state of discharging; After electric discharge overcurrent reason is eliminated (even if in the unloaded state); by the voltage of the drop-down link VM of discharge path 320; automatically short-circuit protection state is exited to make battery; return to regular picture state; thus overcome the Deadlock of electric discharge overcurrent protection state; and this circuit structure is simple, and cost is low.
In the utility model, " connection ", " being connected ", " company ", " connecing " etc. represent the word be electrically connected, and if no special instructions, then represent direct or indirect electric connection.
It is pointed out that the scope be familiar with person skilled in art and any change that embodiment of the present utility model is done all do not departed to claims of the present utility model.Correspondingly, the scope of claim of the present utility model is also not limited only to previous embodiment.