CN101179200A - Trickle discharge for battery pack protection - Google Patents
Trickle discharge for battery pack protection Download PDFInfo
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- CN101179200A CN101179200A CNA2007101521006A CN200710152100A CN101179200A CN 101179200 A CN101179200 A CN 101179200A CN A2007101521006 A CNA2007101521006 A CN A2007101521006A CN 200710152100 A CN200710152100 A CN 200710152100A CN 101179200 A CN101179200 A CN 101179200A
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Abstract
Battery protection circuitry and method are disclosed. A battery is protected from a large current overdrawn condition by setting a discharge switch into a controllable conduction state. After the discharge switch is in the controllable conduction state, a tickle discharge current is gradually generated under control of a switch control signal. The trickle discharge current can be used to determine whether the large current overdrawn condition still exists. When the large current overdrawn condition is removed, the discharge switch is turned back on.
Description
Technical field
The present invention relates to battery charging/discharging circuit and battery pack protection, relate in particular to the battery charging/discharging circuit that can carry out trickle precharge and/or trickle discharge.But practicality of the present invention can find in being used for the charge/discharge/protection system of mancarried electronic aid, for example, laptop computer, PDA, mobile phone, and/or have the electronic equipment of any type of rechargeable battery.
Background technology
Rechargeable battery, especially lithium ion battery need carry out trickle precharge (recovering charging) to avoid producing damage to exhausting battery from the electric weight spent condition.Depleted and its cell voltage becomes and is lower than threshold voltage V when rechargeable battery
UVThe time, can not use big charging current directly to charge.On the contrary, need precharge mode.In precharge mode, use little charging current, be charged to greater than voltage V up to cell voltage
UV, it just can be recharged with normal mode then, just, charges by bigger charging current.For lithium ion battery, the threshold voltage of a unit electricity core depends on battery types and producer near 2.4V～3.0V.About 10mA～the 100mA of pre-charge current.Yet normal charging current can be extremely several amperes of hundreds of milliamperes, depends on battery capacity.
Figure 1A shows charge profile Figure 50 of Lithuim rechargeable battery.When cell voltage is higher than V
UV, battery enters constant current (CC) charge mode, and big constant current is used for battery is carried out quick charge (cell voltage also increases along with the battery electric quantity increase).When cell voltage is increased to V
OV, it represents overvoltage (for the normal overvoltage voltage of lithium ion battery greatly about about 4.2V), and battery enters constant voltage (CV) charge mode.In this pattern, charger remains on voltage V
OV, charging current reduces gradually.When charging current reduces to predetermined minimum value, 50mA for example, charging procedure stops.In the CV charge mode, charger must accurately be adjusted to V with voltage
OV(error+/-0.005V).If charging output is greater than V
OV, will take place so the overcharging of battery, this can cause the safety problem of lithium ion battery.
Illustrated among Figure 1B and realized precharge traditional circuit 10.The precharge MOSFET12 that connects with resistance 14 is used for precharge.In the precharge moment, charging FET16 closes, and precharge FET12 opens.Therefore, pre-charge current roughly is to be determined divided by series resistance 14Rpre by the pressure reduction between charger input voltage VPACK+ and the total cell voltage Vcell.When existing AC adapter (not shown) and VPACK+ to be higher than cell voltage V
Cell, charging or precharge will begin based on the initial voltage of each unit.If the voltage in the unit is lower than threshold value V arbitrarily
UV, battery pack will enter precharge mode.Otherwise charge normal beginning.
Those skilled in the art will admit that the circuit 10 among Figure 1B comprises battery monitor IC20, and it comprises each unit (Cell1, the circuit of voltage and current Cell2.....Cell4) of monitor battery pack 22.Such circuit can comprise the switching network 24 in order to each cell voltage of sampling.In order to control the operation of precharge MOSFET12, traditional circuit 10 comprises a comparator 26, and they can be by switch 30 with constant reference voltage 28 (V
UV) compare with the voltage of each unit.
Yet a defective of the circuit shown in Figure 1B is that (just, MOSFET12) with resistance 14, they can increase extra cost and increase the area of PCB needs one extra MOSFET.In addition, in the sort circuit topology, lower cell voltage causes bigger pre-charge current.And pre-charge current reduces along with the increase of cell voltage, this means that will finish precharge needs the longer time.
In addition, the value of resistance 14 is normally fixed, and the minimum and maximum value of pre-charge current is also fixed usually, therefore can not be adjusted in order to different battery pack needs to be provided.
Another defective of this topology is that battery pack 22 and MOSFETs are damaged under abnormal conditions easily, and for example the VPACK+ end is shorted to the VPACK-end, and perhaps Wai Bu charger is reversed and is added to VPACK+ and VPACK-end.In this topology, discharge FET18 or be unlocked to allow discharge or to be closed and can not to discharge.As discharge FET18 when being unlocked, if abnormal conditions have taken place, the big electric current that flows out from battery pack 22 flow through discharge FET18 and charging FET16, this will destroy battery pack 22 and/or MOSFET successively.
In addition, when battery pack 22 is removed from electronic system, for example, be placed on the support, discharge FET18 can be closed in order to protection battery pack 22 and exempt from abnormal conditions.Yet because discharge FET18 is closed, therefore battery pack 22 can not need a mechanical means or electronic circuit to come announcing circuit 10 to open discharge FET18 immediately to the electronic system energising when battery pack 22 is inserted back in the electronic system.Extra mechanical means or electronic circuit will increase the complexity of circuit 10, price and/or size.In addition, battery pack still can be owing to abnormal conditions are damaged easily after in being inserted into electronic system.
The conventional approach that is used for battery pack protection is to close the big electric current of discharge FET18 to avoid producing when abnormal conditions take place.After being closed a scheduled time, for example 30 seconds, discharge FET18 was opened once more.If abnormal conditions still exist after discharge FET18 is opened again, big electric current will be flowed through and be discharged FET18 and trigger battery pack protection once more.Therefore, discharge FET18 is closed once more.Otherwise battery pack 22 will be operated in a regular picture pattern along with the unlatching of discharge FET18.Yet, if abnormal conditions all existed in a long period, the big electric current discharge FET18 that will flow through continuously, this will finally destroy battery pack 22 and/or MOSFET.
Therefore, need a kind of circuit and its method and can carry out trickle precharge and/or trickle discharge, the present invention has mainly proposed a kind of like this circuit and method.
Summary of the invention
In one embodiment, provide the method for avoiding big overcurrent or short-circuit conditions in order to the protection battery pack.This method is included in the step that turn-on control circuit produces a control signal, and if big overcurrent or short-circuit conditions take place, under the control of control signal, produce the step of a trickle discharge electric current.The trickle discharge electric current can stop big electric current to circulate from battery pack.
In another embodiment, provide another kind of protection battery pack to avoid the method for overcurrent or short-circuit conditions.The method comprising the steps of a) closes discharge switch when big overcurrent or short-circuit conditions take place, b) produce a control signal in ON-OFF control circuit, control signal has a predetermined maximum level, c) under control signal control, produce a trickle discharge electric current, the trickle discharge electric current has a threshold current level and can prevent the big current flowing of battery pack, d) according to the trickle discharge electric current, whether threshold current level and predetermined maximum controlling level detect big overcurrent or short-circuit conditions still exists, e) if still there are repeating step in big overcurrent or short-circuit conditions a) to d), and f) if big overcurrent or short-circuit conditions are eliminated then the complete opening discharge switch.
Description of drawings
Although those skilled in the art will know that the following detailed description employed be preferred embodiment and method, the present invention is not limited to these preferred embodiments and method.Claim scope of the present invention is defined by appended claims.
Other features and advantages of the present invention will and become clearer and more definite with reference to the accompanying drawings along with following detailed, the part that wherein identical digitized representation is identical, and wherein:
Figure 1A is typical charge process electric current, the voltage schematic diagram of lithium ion battery;
Figure 1B is traditional battery pre-charging circuit;
Fig. 2 A is according to a kind of typical trickle precharge circuit of the present invention;
Fig. 2 B is according to a kind of typical trickle discharge circuit of the present invention;
Fig. 3 A is the typical trickle precharge circuit of another kind according to the present invention;
Fig. 3 B is the typical trickle discharge circuit of another kind according to the present invention;
Fig. 4 is the typical trickle precharge circuit of another kind according to the present invention;
Fig. 5 is a typical programmable current source;
Fig. 6 is a typical trickle precharge and trickle discharge circuit;
Fig. 7 is based on the wherein control flow chart of battery pack short circuit/overcurrent protection of an embodiment of the present invention.
Embodiment
Fig. 2 A shows according to of the present invention one typical trickle precharge circuit 100.In this embodiment, two MOSFET 104 and 102 (charging FET CHG_FET and discharge FETDSG_FET) have been used.In this embodiment, charging FET104 and discharge FET102 place with the back-to-back series connection of the mode of describing.In the trickle precharge pattern, discharge FET102 is (nonconducting) who closes, if but charging FET (CHG_FET) 104 opens (conduction), and electric current is still flowed through its body diode to battery cell.If CHG_FET104 closes, do not have electric current to flow to so or flow out battery cell.
Except two MOSFET, circuit 100 also can comprise a reference diode D1110, a discharging driver 106, one charging drivers 108, and a reference current source Iref112.Each all comprises separately comparator charging driver 108 and discharging driver 106.At the charge mode of routine, K switch 1 and K2 (114 and 116) are set to position 2.In this position, charging driving voltage CHG is driven to reference voltage CHG_REF, and this voltage can complete opening charging FET104.Therefore, reference voltage CHG_REF should select according to the cut-in voltage of charging FET104.
In the trickle precharge pattern, K switch 1114 and K2116 can be set to position 1.When the AC adapter connected upward, VPACK+ voltage can raise.Charging FET104 can be recharged driver 108 and is driven into the operate in saturation district, and this means that also charging FET104 can be used as a variable resistor, the trickle-charge current charging FET104 that can flow through.Charging driver 108 dynamic adjustments charging FET (CHG_FET) 104 make voltage Vc equal Vd, and Vd is provided with by diode D1110 and reference current source Iref112.
Vc is the voltage of the tie point of MOSFET102 and 104.Vc can be set as the input of (-) negative terminal of the comparator in the charging driver 108, and Vd (being provided with by Iref and D1) can be set as the input of ㈩ anode simultaneously.Output signal CHG is Vd-Vc.As Vc Vd no better than, the gain of the comparator of charging driver 108 can be ordered about charging FET104 and work in the zone of saturation.Like this, charging driver 108 dynamic adjustments Vc during trickle precharge makes it to be equal to fixed signal Vd.
Under aforesaid bias conditions, the DC electric current of the diode D1110 that flows through provides by following formula:
Iref＝A1*IS1*(exp(Vd1/Vt)-1)
Wherein A1 is the junction area of diode D1, and IS1 is the diode reverse saturation current, and Vd1=Vd-Vcell is the voltage drop that strides across diode D1110, and Vt is a diode threshold voltage.The DC electric current of the body diode among the discharge FET102 provides by following formula:
Ipch＝A2*IS2*(exp(Vd2/Vt)-1)
Wherein A2 is the body diode junction area, and IS2 is a body diode unit reverse saturation current, and Vd2=Vc-Vcell is the voltage drop that strides across discharge FET body diode.IS1 and IS2 are determined by selected semiconductor type.If being forced to essence, Vd and Vc equate that trickle precharge electric current and reference current Iref are proportional so, are provided by following formula:
Ipch＝A2/A1*(IS2/IS1)*Iref
Preferably, though not necessarily for the present invention, the junction area A2 of the body diode of charging and discharge FET 102 and 104 is bigger usually to reach low opening resistor and big current capacity, and simultaneously in order to save chip area, the junction area A1 of diode D1 is less.Therefore, because A2＞＞A1, a little electric current I ref (tens microamperes) can be used to control bigger electric current I pch (tens to the hundreds of milliampere).
Fig. 2 B shows according to a trickle discharge circuit 200 of the present invention.Present embodiment is similar to the circuit of describing among Fig. 2 A 100, except reference current source 112 and diode 110 are connected to discharge FET102 end.In trickle discharge period, charging FET104 closes, trickle discharge electric current its body diode of flowing through.The operation principle of circuit 200 is described in detail in the above with reference to figure 2A.
Fig. 3 A shows according to another typical trickle precharge circuit 300 of the present invention.In this embodiment, charging FET302 and discharge FET304 face-to-face rather than back-to-back (as Fig. 2 A) series connection are placed.The embodiment of Fig. 3 A also comprises a reference diode D1310, and charging driver 306 can be by K switch 1 and K2 (314 and 316) control in this embodiment.
At normal charge mode, K switch 1 and K2 can be set to position 2, thereby the grid voltage of charging FET302 is driven to CHG_REF, complete opening charging FET302.In the trickle precharge pattern, discharge FET304 closes, and K1 and K2 are set to position 1.Thereby charging driver 306 can be substantially equal to Vd by dynamic adjustments charging FET302 coercive voltage Vc like this.Under aforesaid bias condition, the DC electric current of diode D1310 provides by following formula:
Iref＝A1*IS1*(exp(Vd1/Vt)-1)
Wherein A1 is a diode D1 junction area, and IS1 is a diode D1 unit reverse saturation current, and Vd1=VPAK+-Vd is the voltage drop that strides across diode D1, and Vt is a diode threshold voltage.The DC electric current of the body diode of discharge FET304 is:
Ipch＝A2*IS2(exp(Vd2/Vt)-1)
Wherein A2 is the body diode junction area, and IS2 is a body diode unit reverse saturation current, and Vd2=VPACK+-Vc is the voltage drop that strides across discharge FET body diode.IS1 and IS2 are determined by selected semiconductor type.If Vd is identical with the Vc pressure, the trickle precharge electric current provides by following formula so:
Ipch＝A2/A1*(IS2/IS1)*Iref
Fig. 3 B shows according to of the present invention one typical trickle discharge circuit 400.This embodiment is similar to the circuit 300 shown in Fig. 3 A, except reference current source 312 and diode 310 are to be connected to charging FET302 end.During trickle discharge, the charging FET302 close, discharging current can flow through the charging FET302 body diode.The operation principle of circuit 400 is described in detail in the above with reference to figure 3A.
In order to quicken the trickle precharge process, trickle precharge electric current I pch can promptly be regulated based on cell voltage.Cell voltage is high more, the trickle precharge electric current by programming reference current Iref can be set up big more.Circuit can be used for the programmable reference current source based on cell voltage among Fig. 5.
Another typical trickle precharge circuit 500 has also been described among Fig. 4.In this embodiment, charging FET504 and discharge FET502 can place with the back-to-back series connection of this mode of describing.In the trickle precharge pattern, discharge FET502 closes (non-conductive), if but charging FET (CHG_FET) 504 opens (conduction), and electric current is still flowed through its body diode to battery cell so.If CHG_FET504 closes, do not have electric current to flow to so or flow out battery cell.
This embodiment also comprises a reference resistance R1, a discharging driver 506, one charging drivers 508 and a reference current source Iref1 512.Charging driver 508 and discharging driver 506 can comprise comparator separately.At the charge mode of routine, K switch 1 and K2 (520 and 518) are set to position 1.In this position, gate drive voltage CHG is driven to the working point that equals reference voltage CHG_REF, with complete opening charging FET504.Therefore, should select reference voltage CHG_REF according to the opening feature of charging FET 504.
When needs trickle charge (just, trickle precharge), K switch 1 and K2 are connected to node 2.The input of the comparator in the charging driver 508 is the voltage drop (being produced by Iref1 512) (-) that strides across the voltage of Rsens (+) and stride across R1 like this.The gain of the comparator in the charging driver 508 should design big (for example 80dB) so that the voltage drop that makes Iref1 stride across resistance R 1 is approximately equal to the voltage drop that trickle-charge current Ipch strides across sensing resistor Rsens.
The trickle precharge electric current provides by following formula:
Ipch＝Iref1*R1/Rsens
Wherein Iref1 is a programmable current reference source.Usually Rsens very little (for example similar 10 to 20 milliohms), R1 can be selected in 10 ohm the scope simultaneously.Therefore, R1 can be very big to the ratio of Rsens, thereby can use a very little reference current Iref1 to produce big relatively trickle precharge electric current.
In the embodiment of Fig. 4, during the trickle precharge pattern, discharge FET 502 can be by complete opening, thereby eliminates the biased electrical pressure drop of the diode forward direction between VPACK+ and the battery voltage.In this pattern, thus K switch 4 514 and K3 516 can be set to grid voltage that position 1 drives discharge FET to the reference voltage DSG_REF that discharges with the complete opening FET502 that discharges.
Still with reference to figure 4, at normal discharge mode, K switch 3 and K4 can be connected respectively to node 1.Like this, discharging driver 506 drives discharge FET502 complete opening.When in the trickle discharge pattern, K switch 3 and K4 can be connected to node 2.Because the high-gain loop of discharging driver 506, the voltage drop that is striden across resistance R 2 by Iref2 is approximately equal to the voltage drop that strides across sensing resistor Rsens.Like this, the trickle discharge electric current is provided by following formula:
Idsg＝Iref2*R2/Rsens
Wherein Iref2 is a programmable current reference source.Usually Rsens can be very little, and R2 can be very big to the ratio of Rsens like this, and therefore a little reference current Iref2 can produce big relatively trickle discharge electric current.Owing to be inverted at the interdischarge interval sense of current, the voltage drop that strides across the voltage drop of sensing resistor Rsens and stride across R2 has reversed polarity.Therefore, polarity inversion circuit 522 polarity of the voltage that strides across Rsens that is used to reverse.
In this embodiment, during trickle charge, discharge FET502 can be by complete opening.The forward bias voltage of the diode between VPACK+ and battery voltage is eliminated like this.Same, during trickle discharge, charging FET504 can be fallen with the forward bias voltage of eliminating the diode between battery voltage and the VPACK+ by complete opening.
In the present invention, in case MOSFET and diode are fixed, Ipch still can be adjusted by programmable current source (Iref) 112,312,510 and/or 512.One typical circuit topology of one programmable current source has been described among Fig. 5.The circuit of Fig. 5 is suitable for producing the electric current I ref with ratio current mirror.Certainly, except the circuit among Fig. 5, the programmable reference current source is known in the art and can be accomplished in several ways.
One typical trickle precharge and trickle discharge circuit 600 have been described among Fig. 6.In this embodiment, charging FET604 and discharge FET602 place with the back-to-back series connection of the mode of describing, and perhaps alternative places with aforesaid face-to-face series connection.In this embodiment, d convertor circuit (DAC) 616 can be used to produce a FET driving voltage, is described more fully below.
This embodiment comprises the control loop that an analog-digital converter circuit (ADC) 614, one controllers 612 and d convertor circuit (DAC) 616 are formed.The electric current that strides across sensing resistor Rsens618 can detect by ADC614.ADC614 conversely, can produce the digital signal of representing electric current and send these signals to controller 612.In operation, if the electric current by sensing resistor 618 less than predetermined threshold value, controller can send data to DAC616 to increase corresponding FET driving voltage.Otherwise it will send data to DAC616 to reduce the FET driving voltage up to current sensor and scheduled current approximately equal.
In normal charge or discharge pattern, DAC616 disabled (by the DAC_EN signal controlling that receives by DAC616), charging FET604 and the complete conducting of discharge FET602.Charging driver 608 drives the grid voltage of charging FET604 to the CHG_REF value, and complete opening charging FET604.Discharging driver 606 drives the grid voltage of discharge FET602 to the DSG_REF value, and complete opening discharge FET602.
In the trickle discharge pattern, K switch 1 620 is connected to node 1.Discharging driver 606 disabled (DSG_EN is a low level) is output as high resistant, and the conduction state of the FET602 that discharges this moment can be controlled by DAC616.Like this, discharge FET602, sensing resistor Rsens618, ADC614 and DAC616 can form control loop.By the opening resistor of control discharge FET602, the present invention can adjust the default value (can be pre-programmed into controller 612) of trickle discharge electric current to.The opening resistor of MOSFET can be adjusted by adjusting gate drive voltage.
In one embodiment, trickle discharge electric current if desired is set to Itd, uses SAR (successive approximation register) mode can obtain to control the control corresponding code of DAC616 so.The MSB of DAC (highest order) at first is set as height, if the electric current I sen by sensing resistor Rsens618 greater than Itd, the MSB position is set as lowly so, otherwise it will remain height.The 2nd MSB position is set as height then, if Isen＞Itd, the 2nd MSB position is set as low, otherwise it will remain height.This mode of approaching one by one will last till that the LSB (lowest order) of DAC is set.(not shown) can controlled device 612 accesses in the register thereby the control corresponding code can be stored in.If be that a given battery pack is set Itd, control routine also can be set so.No matter when need trickle discharge, controller 612 can send the control routine that is programmed and arrive DAC616, and therefore, battery pack can transmit Itd to external loading.If the trickle discharge electric current need be adjusted, above-mentioned control loop can correspondingly be used for increasing or reducing control routine.In the trickle discharge pattern, charging driver 608 can be activated or forbid.Difference is exactly that the trickle discharge electric current is with charging FET604 or its body diode of flowing through respectively.
In the trickle charge pattern, K switch 1 620 is connected to node 2.Charging driver 608 disabled (CHG_EN is low).The conduction state of charging FET604 can be controlled by DAC616.In this pattern, charging FET604, sensing resistor Rsens618, ADC614 and DAC616 form control loop.By the opening resistor of control charging FET604, present embodiment can be adjusted trickle-charge current to a set point.Pre-charge current is a fixed value normally.In this pattern, present embodiment can produce a control routine (using above-mentioned SAR method) and preserve control routine in memory.For the trickle precharge electric current, its value can be limited between the lower limit on a certain and change, and therefore, correspondingly control routine is at C
TCHAnd C
TCLBetween change, thereby allow trickle-charge current correspondingly to be regulated.In the trickle charge pattern, discharging driver 606 also can be activated or forbid.Difference is exactly flow through respectively discharge FET602 or its body diode of trickle-charge current.
Trickle discharge pattern recited above can further be used to realize battery pack short circuit/overcurrent protection.First kind of following embodiment to battery pack protection of (when also battery pack is in idle condition) is effective when battery pack is taken out from electronic system.Unlike the conventional method that keeps discharge FET602 to close, this embodiment FET602 that will discharge is arranged to a kind of controllable conduction state.As discharge FET602 when being in controllable conduction state, even the situation of being short-circuited, just the VPACK+ end is shorted to the VPACK-end, and the heavy current impact FET602 opening resistor that discharged stops.Similarly, heavy current impact also is prevented from when overcurrent situations takes place.In fact, when short circuit/overcurrent situations takes place, the trickle discharge electric current discharge FET602 that will flow through, the trickle discharge electric current can be set to a value of setting so that guarantee battery pack and the safety of MOSFET.For example, setting the trickle discharge electric current is 100mA, can drive the peripheral control unit (it is different from the controller 612 shown in Fig. 6) that is embedded in the electronic system.When battery pack is inserted in the electronic system, embed controller and can detect the insertion of battery pack and notify battery pack to enter normal discharge mode.Like this, just do not need extra mechanical means or electronic circuit to detect the insertion of battery pack.Yet when battery pack was inserted in the electronic system, this embodiment did not further provide battery short circuit/overcurrent protection.Like this, have only that this embodiment is useful when battery pack is taken out from electronic system.
Flow chart 700 shown in Fig. 7 has been described second kind of embodiment of battery pack protection.When battery pack is taken out from electronic system and all is effective when battery pack is inserted in the electronic system.Beginning, as shown in step 702, battery pack or idle condition (for example, it is taken out from electronic system) is perhaps at normal discharge mode (for example, it is inserted in the electronic system).No matter which kind of pattern is battery pack be in, step 704 is judged the behavior that short circuit/overcurrent takes place.If be not short-circuited/and overcurrent situations, battery pack will rest on free time or discharge mode so.If there is short circuit/overcurrent situations, step 706 is closed discharge FET602 immediately so.Usually, discharge FET602 can close in several microseconds.So, in step 708, if discharge FET602 has been closed preset time, for example, and 25 seconds, unlike traditional method, the FET602 of complete opening discharge at once, discharge FET602 will be driven to controlled conduction state.When the discharge FET602 be in the controllable conductivity state, along with trickle discharge electric current in step 710 flow through the discharge FET602, battery pack will be operated in the trickle discharge pattern.If the scheduled time does not have expired, discharge FET602 still rests on closed condition.
Those skilled in the art will recognize that for performing step 708 embodiment shown in Fig. 6 can comprise a battery management firmware and a timer.The battery management firmware can the monitoring hardware action.Timer has a preset time (for example 25 seconds).If be short-circuited/and overcurrent situations, the battery management firmware will be apprised of discharge FET602 and be closed, start timer then.If the preset time of timer is expired, managed firmware will be apprised of discharge FET602 and close scheduled time length.
In the trickle discharge pattern, the DAC616 among Fig. 6 provides gate drive voltage to discharge FET602.Thereby make discharge FET602 work in the controllable conductivity state.By regulating gate drive voltage, the opening resistor of discharge FET602 is conditioned, and the trickle discharge electric current of the discharge FET602 that therefore flows through is correspondingly regulated.
In the trickle discharge pattern, can comprise following substep.Beginning under the control of controller 612, is set to 0 from the gate drive voltage control code of DAC616 in step 712.Then, the gate drive voltage control code increases gradually in step 714.According to the characteristic of MOSFET, one of ordinary skill in the art will readily recognize that the opening resistor of discharge FET602 will reduce gradually along with the increase of gate drive voltage control code, the trickle discharge electric current of the discharge FET602 that flows through conversely will increase gradually.The gate drive voltage control code increases each time, and the voltage that corresponding trickle discharge electric current strides across resistance R sens618 is detected, and is used to determine whether to exist short circuit/overcurrent situations then.
Especially, in step 716, the trickle discharge electric current is compared with predetermined current, for example, 40 milliamperes, is used to determine whether to exist short circuit/overcurrent situations.If the trickle discharge electric current, can infer that short circuit/overcurrent situations still exists greater than scheduled current.Then, battery pack protection is restarted by the operation of step 706 in the system shown in Fig. 6.If the trickle discharge electric current is less than scheduled current, the gate drive voltage control code will be compared with predetermined maximum control code in step 718.In fact, the gate drive voltage control code will can unrestrictedly not increase, and can be limited to predetermined maximum control code.In step 718, if the gate drive voltage control code reaches predetermined maximum control code, can infer that short circuit/overcurrent situations no longer exists in step 702, battery pack is with returning to idle mode or regular picture pattern.Otherwise battery pack does not exist short circuit/overcurrent situations to withdraw from the trickle discharge pattern up to having short circuit/overcurrent situations or judge in step 718 owing to judgement in step 716 repeated execution of steps 714,716 and 718.
The scheduled current is here set by the power dissipation performance of considering MOSFET.For the battery pack with four batteries shown in Fig. 6, scheduled current can be set to 40 milliamperes, thus the discharge FET602 maximum power dissipation near 680 milliwatts, this is a safety value for power MOSFET.
In addition, the voltage at the VPACK+ end also can be applied to determining whether to exist short circuit/overcurrent situations.In step 716, the voltage of VPACK+ end is detected and compare with predetermined voltage, for example, and 100 millivolts.If the voltage of VPACK+ end can conclude that less than predetermined voltage short circuit/overcurrent situations still exists.Otherwise gate drive voltage will compare with predetermined maximum control code in step 718.The setting of the predetermined voltage of VPACK+ end will be considered the noise and the internal resistance of cell.For the embodiment of Fig. 6, predetermined voltage is set to 100 millivolts, and this is the compromise of considering between the quantity of short circuit/overcurrent situations and the noise and the internal resistance of cell preferably.
From Figure 1A, we know that charging current needs Be Controlled between precharge phase and between constant voltage (CV) charge period.In traditional circuit, need an extra precharge FET to control pre-charge current.In such traditional circuit, the CV charging must rely on charger to regulate charging voltage accurately to V fully
OV, charging current will be successively decreased then.
In the present embodiment, there is not extra precharge FET pre-charging functions can realize yet.In addition, in order to quicken pre-charge process, pre-charge current Ipch can easily be regulated based on cell voltage.Cell voltage is high more, and pre-charge current is set to big more, for example described herein with reference to figure 2A by programming reference current Iref, the control routine method of describing among Fig. 3 A and Fig. 4 or Fig. 6.
Further, described as numerous embodiment here, trickle-charge current control is utilized in also can be during CV, and trickle charging circuit can become to give birth to trickle-charge current based on cell voltage in the meantime.So, the CV charging current is successively decreased does not need to rely on charger and comes accurately regulation voltage V
OVTherefore, several embodiment provided by the invention can not need expensive, accurate voltage-regulation charger.In fact, easily the AC adapter can be applied to lithium ion cell charging.Because between the CV charge period, even charger can not be fixed on V with constant voltage
OVBut charging current is limited to based on cell voltage and definite pre-programmed trickle current value.So, can not overcharge.This charge-current limit can be used as second layer overvoltage protection (by being provided with the electric current limit to such an extent that compare at voltage V
OVThe observation current value of Shi Shiji is big a little), perhaps as the ground floor overvoltage protection (by regulating charging current up to the V that obtains accurate expection
OV).
Using trickle discharge performance of the present invention, is possible for the short circuit/overcurrent protection preferably of battery pack.In the prior art, discharge FET or fully open to allow discharge or fully to close to forbid discharge.When battery pack is taken out from electronic system, for example, be placed on the support, FET or to be held open to prepare at any time when battery pack injects electronic system be the electronic system power supply so discharges.In this case, if abnormal conditions have taken place, for example the VPACK+ end is shorted to the VPACK-end, and big electric current releases from battery, thus, will destroy battery; The FET that perhaps discharges keeps closing to prevent that battery from suffering short circuit/overcurrent situations.But this will make and stop battery to be powered to system when battery pack is inserted in the system.Need some technical method notice batteries to turn back to the discharge FET state of opening.This will cause client's inconvenience and increase cost.
We can be set to battery pack the trickle discharge pattern to use the present invention, when battery is taken out from electronic system.The trickle discharge current value can selectedly get very big, supposes 100 milliamperes, enough powers for the system that embeds controller when battery pack is inserted in the electronic system.Embedding controller system then will detect the existence of battery and notify battery to be converted to the regular picture pattern.Along with discharge FET is restricted to predetermined trickle discharge electric current with electric current, suppose 100 milliamperes, even the VPACK+ end is shorted to the VPACK-end, big current surge also can be prevented from.
And, no matter whether battery pack takes out from electronic system or in electronic system, battery pack of the present invention can prevent to suffer abnormal conditions, for example, short circuit/overcurrent situations.Discharge FET is closed in beginning when abnormal conditions take place.Then, after the down periods at the fixed time, discharge FET is driven to controlled conduction state, rather than as complete opening in the conventional method.Therefore, battery pack will be operated in the trickle discharge pattern.Gate drive voltage increases gradually, the corresponding corresponding increase of trickle discharge electric current.In this process, if corresponding trickle discharge electrorheological must be supposed 40 milliamperes greater than scheduled current, can infer that abnormal conditions exist, therefore discharging, FET will close once more and battery pack will repeat aforesaid operations.If gate drive voltage is increased to a predetermined maximum controlling voltage, corresponding trickle discharge electric current does not also reach scheduled current, can determine that abnormal conditions have been eliminated and battery pack can be carried out work in the regular picture pattern.
Trickle discharge and trickle charge performance are very useful for the system that supports many batteries.When electronic system needed more electric power and Geng Duo characteristic, it is more universal that many battery pack will become.When many battery pack are discharged simultaneously, they can provide more electric power to system, and since a plurality of battery pack parallel it also will reduce the internal resistance of cell to raise the efficiency.But many battery pack are discharged simultaneously and are had the prerequisite of a strictness, and these battery pack must accurately have identical voltage.Otherwise,, suppose 10 millivolts even two battery pack just have very little voltage difference, because the resistance of power bus is very little, supposes 2 milliohms, it also will have a big electric current so, 5 amperes, it will flow to the battery pack with low voltage from having the higher voltage batteries group.In fact, many battery pack are difficult to have identical voltage, even and two battery pack have a very accurate ADC come monitoring battery voltage also to be difficult to supposition they have identical voltage because battery voltage changes along with discharging current.Along with the application of trickle discharge function, we can solve following problem (we are example with two battery pack).
System has two battery pack, battery pack A and battery pack B.Beginning, battery pack A voltage is higher than battery pack B voltage; Battery pack A at first powers to system, and battery pack A voltage reduces gradually.The discharge FET of battery pack B is closed to forbid discharge; When battery pack A voltage drops to when identical with battery pack B voltage, we are set to trickle charge pattern or trickle discharge pattern with battery pack B.If we are set to the trickle charge pattern with battery pack B, we can complete opening discharge FET, and drive charging FET to its operate in saturation district and charging FET as a current-limiting resistance; If we are set to the trickle discharge pattern with battery pack B, our complete opening charging FET, and drive discharge FET to its operate in saturation district and discharge FET as current-limiting resistance.For the consideration of a lot of safety factors, we can be with trickle charge control code C
TCPerhaps trickle discharge control code C
TDBe set to a little current value.Thereby the equivalent resistance of charging FET or discharge FET becomes bigger.Because battery pack A discharge still battery pack B is in idle pulley, even their tested voltage is identical, and actual battery pack A voltage will be higher than battery pack B voltage.Therefore, battery pack A will charge to battery pack B.Yet the resistance that charging current is recharged FET (if battery pack B is set to the trickle charge pattern) or discharge FET (if battery pack B is set to the trickle discharge pattern) limits.The limited current value is by control code C
TCPerhaps C
TDDetermine.We also monitor this charging current by the ADC among the battery pack B; When the voltage difference of battery pack A and B becomes more and more hour, the charging current from battery pack A to battery pack B will become more and more littler.When this charging current during less than predetermined value, suppose 10 milliamperes, we can be converted to normal discharge mode from trickle charge pattern or trickle discharge pattern with battery pack B.
Therefore, trickle precharge able to programme disclosed in this invention and/or trickle discharge circuit are compared with traditional circuit structure with method can provide more flexibility, and assembly still less and the efficient of Geng Gao are finished precharge.The quantity of electric charge (battery of deep discharge needs the trickle charge pattern) based on battery cell, in Fig. 2 A and 2B, switch (K1, K2 and/or K3 and K4) can be controlled by battery monitor IC, and trickle charging circuit able to programme is set to trickle precharge pattern or normal charge mode.Further understand, circuit structure described herein can use discrete device and/or integrated circuit to realize.The present invention is suitable for any mancarried electronic aid that uses rechargeable battery (portable computer, mobile phone, PDA or the like).
The concrete circuit topological structure of here mentioning is an exemplary, and other trickle charge/discharge circuit topological structure also can be used.Same, based on typical trickle charge/discharge circuit of mentioning many circuit distortion and improvement also can be arranged here, but all not break away from spirit of the present invention.All these improvement are all thought within the scope of the present invention, all are subject to claim of the present invention.
Claims (15)
1. one kind is used to protect battery pack to avoid the method for big overcurrent or short-circuit conditions, it is characterized in that, may further comprise the steps:
Produce a control signal at turn-on control circuit; And
If big overcurrent or short-circuit conditions take place, under the control of control signal, produce a trickle discharge electric current,
Wherein the trickle discharge electric current can prevent that big electric current from circulating from battery pack.
2. method according to claim 1 is characterized in that, further comprises step:
Under the control of control signal, adjust described trickle discharge electric current.
3. method according to claim 2 is characterized in that, adjusts described trickle discharge electric current and further may further comprise the steps:
Under the control of control signal, discharge switch is made as the controllable conductivity state;
Adjust the resistance of discharge switch according to control signal; And
Resistance according to discharge switch is adjusted the trickle discharge electric current.
4. method according to claim 1 is characterized in that, described trickle discharge electric current can provide electric power by the peripheral control unit in being embedded in electronic system.
5. method according to claim 4 is characterized in that, the control that further is included in described peripheral control unit produces the step of a regular picture electric current down.
6. a method of protecting battery pack to avoid overcurrent or short-circuit conditions is characterized in that, may further comprise the steps:
A), when taking place, big overcurrent or short circuit close discharge switch;
B), produce a control signal, this control signal has predetermined maximum level in ON-OFF control circuit;
C), under the control of control signal, produce a trickle discharge electric current, this trickle discharge electric current has a threshold current level and can stop battery pack that big current flowing takes place;
D), according to the trickle discharge electric current, threshold current level and predetermined maximum level detect whether have big overcurrent or short-circuit conditions;
E) if big overcurrent or short-circuit conditions still exist repeating step a) to d);
F) if big overcurrent or short-circuit conditions are eliminated then are opened discharge switch.
7. method according to claim 6 is characterized in that, further may further comprise the steps:
One timer is set; And
When timer is expired, produce the trickle discharge electric current.
8. method according to claim 6 is characterized in that, the step of described generation trickle discharge electric current further is included under the control of control signal discharge switch is made as the controllable conductivity state.
9. method according to claim 6 is characterized in that, further comprises according to described control signal adjusting described trickle discharge electric current.
10. method according to claim 9 is characterized in that, the step of described adjustment trickle discharge electric current further comprises:
Adjust the resistance of discharge switch according to described control signal; And
Adjust described trickle discharge electric current according to the resistance of discharge switch.
11. method according to claim 6 is characterized in that, has big overcurrent or short-circuit conditions if described trickle discharge electric current equals the threshold current level at least.
12. method according to claim 6 is characterized in that, if control signal equals the so big overcurrent of predetermined maximum level at least or short-circuit conditions will be eliminated.
13. method according to claim 6 is characterized in that, step (d) further comprises step:
A) detect the trickle discharge electric current;
B) compare trickle discharge electric current and threshold current level;
C) if the trickle discharge electric current less than the threshold current level then comparison control signal and predetermined maximum level;
D) if control signal less than predetermined maximum level then increase control signal;
E) if the trickle discharge electric current less than threshold current level and control signal less than predetermined maximum level repeating step a) to d).
14. method according to claim 6 is characterized in that, described step (d) further comprises step:
A) positive terminal in battery pack detects voltage;
B) comparative voltage and threshold voltage levels;
C) comparison control signal and predetermined maximum level if voltage is higher than threshold voltage levels;
D) if control signal less than predetermined maximum level then increase control signal;
E) if voltage greater than threshold voltage levels and control signal less than predetermined maximum level repeating step a) to d).
15. method according to claim 14 is characterized in that, has big overcurrent or short-circuit conditions if voltage equals threshold voltage levels at the most.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11/540,236 US7646169B2 (en) | 2004-03-25 | 2006-09-29 | Trickle discharge for battery pack protection |
| US11/540,236 | 2006-09-29 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101179200A true CN101179200A (en) | 2008-05-14 |
| CN100589305C CN100589305C (en) | 2010-02-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN200710152100A Active CN100589305C (en) | 2006-09-29 | 2007-09-28 | Trickle discharge for battery pack protection |
Country Status (3)
| Country | Link |
|---|---|
| CN (1) | CN100589305C (en) |
| HK (1) | HK1118643A1 (en) |
| TW (1) | TWI336158B (en) |
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| CN103683370A (en) * | 2012-08-29 | 2014-03-26 | 三星Sdi株式会社 | Battery pack and method of controlling same |
| CN104204832A (en) * | 2012-03-29 | 2014-12-10 | 罗伯特·博世有限公司 | Method for connecting battery cells in a battery, battery and monitoring device |
| CN104518534A (en) * | 2013-09-27 | 2015-04-15 | 中兴通讯股份有限公司 | Method and device for circuit protection, and charging device |
| CN109510253A (en) * | 2017-09-15 | 2019-03-22 | 保时捷股份公司 | Protection circuit for charging unit |
| CN110247442A (en) * | 2018-03-08 | 2019-09-17 | 凹凸电子（武汉）有限公司 | For protecting the protection circuit and guard method and battery management system of battery pack |
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| US8629679B2 (en) | 2009-12-29 | 2014-01-14 | O2Micro, Inc. | Circuits and methods for measuring cell voltages in battery packs |
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2007
- 2007-09-28 CN CN200710152100A patent/CN100589305C/en active Active
- 2007-09-28 TW TW096136105A patent/TWI336158B/en not_active IP Right Cessation
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2008
- 2008-09-16 HK HK08110237.4A patent/HK1118643A1/en unknown
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| CN104204832A (en) * | 2012-03-29 | 2014-12-10 | 罗伯特·博世有限公司 | Method for connecting battery cells in a battery, battery and monitoring device |
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Also Published As
| Publication number | Publication date |
|---|---|
| TWI336158B (en) | 2011-01-11 |
| HK1118643A1 (en) | 2009-02-13 |
| TW200822484A (en) | 2008-05-16 |
| CN100589305C (en) | 2010-02-10 |
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