Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a discharge tube safety protection system, a discharge tube safety protection method, and a battery management system, so as to solve the problem in the prior art that a discharge tube heats seriously after being connected to a charger after overdischarge and is finally burnt out.
In order to achieve the above purpose, the invention provides the following technical scheme: a discharge tube safety protection system comprises a charger detection circuit, a current sampling circuit and a logic processing circuit, wherein the charger detection circuit is used for generating a charger access signal; the current sampling circuit is used for detecting a charging current access signal generated when the charger is accessed and charging current appears; the logic processing circuit is used for receiving a charger access signal and a charging current access signal, and enabling the discharge tube enabling signal to control the discharge tube NM1 to be started.
Further, a charge tube driver for receiving a discharge tube enable signal and controlling the discharge tube NM1 to be turned on and off, and a discharge tube driver for receiving a charge tube enable signal and controlling the charge tube NM2 to be turned on and off are included.
Further, the logic processing circuit 14 is configured to receive an over-discharge signal of the battery pack, and generate a discharge tube enable signal and a charge tube enable signal according to the over-discharge signal.
Further, still include battery voltage sampling circuit, overdischarge comparator and reference circuit, wherein:
the battery voltage sampling circuit is connected with a battery and is used for collecting a signal of the battery and connecting the sampled signal to the input end of the over-discharge comparator; the reference circuit is used for providing reference signals for the over-discharge comparator and the current sampling circuit; the over-discharge comparator is used for comparing the received sampling signal with the reference voltage and outputting a corresponding over-discharge signal to be connected to the input end of the logic processing circuit.
Further, the battery pack is composed of a plurality of batteries connected in series, and the overdischarge of the battery pack is realized by at least one battery in the battery pack.
Further, the discharge tube driver comprises an inverter U101 and a level shift module LV2HV, wherein an input terminal of the inverter U101 is used for connecting the discharge tube enable signal DFEN output by the logic processing circuit and an input terminal of the level shift module LV2 HV; the output end of the level conversion module LV2HV is connected with the grid of a PMOS tube PM101, the output end of the phase inverter U101 is connected with the grid of an NMOS tube NM101, the drain of the PMOS tube PM101 is butted with the drain of the NMOS tube NM101 and is connected with a DHC pin, and the source of the NMOS tube NM101 is grounded.
Further, when the over-discharge exists in the battery pack, if both the charger access signal and the charging current access signal are yes, the discharge tube NM1 is opened, otherwise, the discharge tube NM1 is closed.
The invention provides a discharge tube safety protection method, which comprises the following steps of firstly sampling the voltage of a battery pack, and judging whether over-discharge exists in one or more sections of the battery pack;
when one or more sections of the battery pack have over-discharge conditions, judging whether the charger is connected and whether charging current exists, when the charger is not connected or does not have charging current, closing the discharge tube NM1, and then continuing to sample the voltage of the battery pack; when the charger is connected and has charging current, the discharge tube NM1 is opened, and then the voltage sampling of the battery pack is continued;
when there is no overdischarge in one or more battery packs, the discharge tube NM1 is opened, and then battery pack voltage sampling is continued.
Further, battery pack voltage sampling is carried out through a battery voltage sampling circuit to generate a plurality of sampling signals; the sampling signal and the reference generated by the reference circuit are connected to the over-discharge comparator, and the corresponding over-discharge signal is output through the comparison of the sampling signal and the reference voltage; the over-discharge signal is connected to the logic processing circuit to output a discharge tube enable signal and a charging tube enable signal; the discharge tube enabling signal is connected with the discharge tube drive and used for controlling the discharge tube to be opened and closed; the charging tube enabling signal is connected with the charging tube drive and used for controlling the charging tube to be opened and closed;
when the over-discharge protection of the battery pack occurs, the over-discharge signal enables the discharge tube enable signal to be disabled through a logic processing circuit, and the discharge tube enable signal is connected with a discharge tube drive and used for controlling the discharge tube NM1 to be closed;
when the over-discharge protection of the battery pack occurs, the battery pack is connected into a charger, a charger detection circuit generates a charger connection signal when detecting the connection of the charger, and a current sampling circuit generates a charging current connection signal when detecting the charging current generated by the connection of the charger; the charger access signal and the charging current access signal are connected to a logic processing circuit to enable the discharge tube enable signal; the discharge tube enabling signal is connected with the discharge tube drive to control the discharge tube to be opened.
Furthermore, when the battery pack is connected to the charger after over-discharge protection, and the charger is pulled out, the charger detection circuit enables the output charger connection signal not to be enabled, and the current sampling circuit enables the output charging current connection signal not to be enabled; the charger access signal and the charging current access signal are connected to a logic processing circuit to enable the state of the discharge tube enable signal to be controlled by the over-discharge signal; the over-discharge signal enables the discharge tube enable signal not to enable through a logic processing circuit; the discharge tube enable signal is connected to the discharge tube driver for controlling the discharge tube NM1 to be closed.
As a further object of the present invention, the present invention proposes the use of the above discharge tube safety protection system in a battery management system.
The battery management system provided by the invention has the advantages that the charger is connected after the discharge tube is closed, the charger detection circuit detects that the charger is connected to output a charger connection signal and sends the charger connection signal to the logic processing circuit, and meanwhile, the current sampling circuit compares the reference voltage generated by the reference and outputs a charging current connection signal and sends the charging current connection signal to the logic processing circuit to change the state of the discharge tube enabling signal, so that the discharge tube drives the discharge tube to forcibly pull up the grid electrode of the discharge tube to open the discharge tube again, and the impedance of a charging path is reduced; when the charger is disconnected, the states of the charger access signal and the charging current access signal are changed; the charger access signal and the charging current access signal are used for outputting a discharge tube enabling signal through a logic processing circuit, and the discharge tube enabling signal is used for driving a discharge tube to cancel forced pull-up of a discharge tube grid; compared with the prior art, the battery management system provided by the invention has the advantages that after the battery pack is over-discharged, the discharge tube NM1 is opened immediately when the charger is connected and generates the charging current, so that the charging current passes through the completely conducted charging tube NM2 and discharge tube NM1, and the condition that the discharge tube NM1 is burnt out is prevented.
Detailed Description
The present invention is further illustrated by the following figures and examples, wherein the following detailed description of the present invention provides numerous specific details that will readily suggest themselves to those skilled in the art and that the present invention may be practiced without these specific details. In other instances, well-known schemes, procedures, components and circuits have not been described in detail so as not to obscure the present invention.
As shown in fig. 7, fig. 7 is a flowchart of an exemplary method for a discharge tube safety protection circuit system according to an embodiment of the present invention, after the discharge tube safety protection circuit system operates, firstly, sampling a voltage of a battery pack, determining whether one or more sections of the battery pack have overdischarge, if the overdischarge exists, determining whether a charger is connected and a charging current exists, if the charger is not connected, closing a discharge tube NM1, and then returning to continue sampling the voltage of the battery pack; if the charger is connected and simultaneously has charging current, the discharge tube NM1 is opened, and then the battery pack returns to continue to sample the voltage of the battery pack; if there is no overdischarge, the discharge tube NM1 is opened and then returns to continue the battery voltage sampling. With this reciprocal, realize after the group battery is put excessively, insert under the charger heavy current charging condition, open discharge tube NM1, let charging current through the charge tube NM2 and the discharge tube NM1 that switch on completely, prevent that the condition of discharge tube NM1 burning out from taking place.
The invention provides a discharge tube safety protection circuit system, which comprises a battery voltage sampling circuit 11, an over-discharge comparator 12, a reference circuit 13, a logic processing circuit 14, a charger detection circuit 15, a charging tube driver 16, a discharge tube driver 17 and a current sampling circuit 18, as shown in figure 1.
The battery voltage sampling circuit 11 is connected with a plurality of series batteries VC 1-VCn to generate a plurality of sampling signals and reference voltage generated by the reference circuit 13, and simultaneously the sampling signals and the reference voltage are sent to the over-discharge comparator 12 to be compared and output an over-discharge signal UVP, when the over-discharge signal UVP is high level, the logic processing circuit 14 enables the discharge tube enable signal DFEN to be low level, the discharge tube driver 17 outputs low level to pull down the grid of the discharge tube NM1 to close the discharge tube NM1, and a discharge path is cut off; after the discharge tube NM1 is closed, a charger is connected between P + and P-, the charger detection circuit 15 detects that the charger is connected to output a charger connection signal CHAIN and sends the charger connection signal CHAIN to the logic processing circuit 14, meanwhile, a charging current connection signal ICHA output by comparing the reference voltage generated by the current sampling circuit 18 and the reference circuit 13 is also sent to the logic processing circuit 14 to enable the discharge tube enable signal DFEN to be changed into high level again, the discharge tube NM1 grid is forcibly pulled up through the discharge tube drive 17 to enable the discharge tube NM1 to be opened again, and the impedance of a charging path is reduced; when the charger connected between P + and P-is disconnected, the charger connection signal CHAIN and the charging current connection signal ICHA become low level, the discharge tube enable signal DFEN is output through the logic processing circuit 14, and the discharge tube driver 17 cancels forced pulling up of the gate of the discharge tube NM 1.
Fig. 2 is a schematic diagram of a battery over-discharge protection principle of the present invention, in which a battery voltage sampling circuit 11 is connected to a plurality of series-connected batteries VC 1-VCn to generate a plurality of sampling signals in real time, and the sampling signals and a reference voltage generated by a reference circuit 13 are simultaneously sent to an over-discharge comparator 12 to compare and output an over-discharge signal UVP. When the voltage of one or more of the series-connected batteries VC 1-VCn is lower than the set over-discharge protection threshold, the over-discharge signal UVP changes to a high level, the logic processing circuit 14 generates the discharge tube enable signal DFEN, and finally the output DHC of the discharge tube driver 17 changes to a low level, as can be seen from fig. 1, the gate of the discharge tube NM1 is pulled low, so that the discharge tube NM1 is closed, the discharge path is further broken, and the battery pack stops discharging.
Fig. 3 shows a specific embodiment of the discharge tube driver of the present invention, the discharge tube driver (17) includes an inverter U101 and a level shift module LV2HV, wherein an input terminal of the inverter U101 is used for connecting the discharge tube enable signal DFEN output by the logic processing circuit (14) and an input terminal of the level shift module LV2 HV; the output end of the level conversion module LV2HV is connected with the grid of the PMOS tube PM101, the output end of the phase inverter U101 is connected with the grid of the NMOS tube NM101, the drain of the PMOS tube PM101 is in butt joint with the drain of the NMOS tube NM101 and is connected with a DHC pin, and the source of the NMOS tube NM101 is grounded.
In fig. 3, the discharge tube enable signal DFEN output from the logic processing circuit 14 is connected to one inverter U101 of the discharge tube driver 17 and the level shift module LV2 HV. When the discharge tube enable signal DFEN is at a high level, the gate of the NM101 is changed to a low level, the NM101 is turned off, the gate of the PM101 is pulled low at this time, the PM101 is turned on, the DHC pin is changed to a high level VDD1 at this time, as can be seen from fig. 1, the discharge tube NM1 is turned on at this time; when the discharge tube enable signal DFEN is low, the gate of the NM101 is high, the NM101 is turned on, the gate of the PM101 is pulled high, the PM101 is turned off, the DHC pin is low, and the discharge tube NM1 is turned off as shown in fig. 1.
Fig. 4 shows an embodiment of the charging tube driver according to the present invention, wherein the logic processing circuit 14 outputs a charging tube enable signal CFEN connected to the gate of the NM201 of the charging tube driver 16. When the charging tube enable signal CFEN is high, NM201 is turned on, and at this time, the current I201 passes through a current mirror formed by PM201 and PM202, and the current I201 generated on PM202 is in a direct proportion relationship K1The multiplied current I202 flows out of the CHC pin, and as can be seen from fig. 1, the voltage drop is generated by the resistor RCHC between the gate and the source of the charging tube NM2, so that the charging tube NM2 is turned on; when the charging tube enable signal CFEN is at a low level, NM201 is turned off, and at this time, the current I202 of PM202 becomes 0, as can be seen from fig. 1, the voltage drop of the resistor RCHC becomes 0, and further, the gate-source voltage of the charging tube NM2 becomes 0, and finally, the charging tube NM2 is turned off. The relationship of the currents I201 and I202 is as follows:
according to fig. 1, after the over-discharge occurs, the discharge tube NM1 is closed, the charge tube NM2 is always opened, the current flowing out from the CHC pin cannot flow back to the ground through the discharge tube NM1, so the P-voltage slowly rises to approach P +, and at this time, when the charger is connected between P + and P-, the P-voltage appears as the charger voltage is greater than the total voltage of the over-discharge battery pack, and the positive electrode of the charger and the positive electrode of the battery pack are both connected to P +, so the negative voltage appears after the P-voltage is connected. Meanwhile, the charging current passes through the battery packs VCn-VC 1 from P +, namely the positive pole of the charger, then passes through the sampling resistor RCS, and then flows back to P-, namely the negative pole of the charger, through the body diode of the discharge tube NM1 and the fully-conducted charging tube NM2, so that voltage is generated at the sampling resistor RCS, and the voltage of the pin of the VCS is lower than the voltage of the ground by one negative voltage.
Fig. 5 is a specific embodiment of the charger detection circuit and the current sampling circuit according to the present invention, and according to the analysis of the charger connected after the overdischarge occurs, it can be known that negative voltages occur at the VMON pin and the VCS pin when the charger is connected after the overdischarge occurs. The charger detection circuit 15 is used for detecting negative voltage appearing on the VMON pin when the charger is connected after overdischarge. PM301, PM302 and PM303 in the charger detection circuit 15 form a current mirror structure, and currents I301, I302 and I303 flowing through the PM301, PM302 and PM303 are in a direct proportion K2The specific relationship is as follows:
I303=I302 (3)
the grid of NM302 is connected with A301, and is lower than grid voltage of NM301 by I302 × R301, and the source of NM302 is connected with VMON pin, according to circuit principle, when the voltage of VMON pin is lower than I302 × R301, the drain A302 of NM302 is pulled down, and the charger switch-in signal CHAIN outputted by inverter U301 becomes high level; when the VMON pin voltage is higher than-I302 × R301, the drain a302 of NM302 is pulled high by PM303, outputting the charger incoming signal CHAIN low through the inverter U301. The detection voltage point of VMON can be set by adjusting the current I302 and the resistor R301.
The current sampling circuit 18 is used for detecting the negative voltage of the charging current appearing at the VCS pin when the charger is connected after overdischarge. The reference circuit 13 outputs a reference voltage VR _ CHA connected to the positive terminal of the operational amplifier OP301 in the current sampling circuit 18, and the operational amplifiers OP301 and NM303 constitute a voltage follower so that the source a303 voltage of the NM303 is equal to VR _ CHA. The resistors R302 and R303 form a divided voltage between a303 and VCS, where a304 is connected to the inverting input terminal of the OP-amp 302, the forward input terminal is grounded, and when the voltage of a304 is lower than the ground, the OP-amp OP302 outputs the charging current access signal ICHA to become high level. The A304 voltage formula is as follows:
when A304 is less than or equal to 0, the formula can be obtained
When the charging current is larger than
The charging current access signal ICHA becomes high level. The detection voltage point of VCS can be set by adjusting resistor R302, resistor R303, and reference voltage VR _ CHA.
Fig. 6 shows an embodiment of the present invention in which the discharge tube enable signal processing is performed by the logic processing circuit, and the over-discharge comparator 12 outputs the over-discharge signal UVP, the charger detection circuit 15 outputs the charger access signal CHAIN, and the charging current access signal ICHA output by the current sampling circuit 18 is sent to the logic processing circuit 14 to output the discharge tube enable signal DFEN, and then sent to the discharge tube driver 17. When no overdischarge occurs, the overdischarge signal UVP, the charger access signal CHAIN and the charging current access signal ICHA are at a low level, at this time, a clear end R of the D flip-flop U401 is controlled by the overdischarge signal UVP, the D flip-flop U401 is cleared effectively, the charger access signal CHAIN is shielded, Q output by the D flip-flop U401 is at a low level, a401 output by the and gate U402 is at a low level, the overdischarge signal UVP enables an output discharge tube enable signal DFEN to be at a high level through an inverter U403 and an or gate U404, as can be seen from fig. 3 and 1, at this time, the discharge tube enable signal DFEN controls a discharge tube driver 17 to output a DHC pin at a high level VDD1, and a discharge tube NM1 is opened; when over-discharge occurs and no charger is connected, the over-discharge signal UVP is at a high level, the charger connection signal CHAIN and the charging current connection signal ICHA are at a low level, the output a401 of the and gate U402 is at a low level, the discharge tube enable signal DFEN output by the over-discharge signal UVP is changed to be at a low level through the inverter U403 and the or gate U404, as can be seen from fig. 3 and 1, the discharge tube enable signal DFEN controls the discharge tube driver 17 to output the DHC pin at a low level, and the discharge tube NM1 is closed; when the over-discharge is connected into the charger, the over-discharge signal UVP is at a high level, the charger connection signal CHAIN generates a high pulse, Q output by a D trigger U401 is at a high level, meanwhile, a charging current connection signal ICHA is at a high level, a discharge tube enabling signal DFEN output by an AND gate U402 and an OR gate U404 is changed into a high level, as can be seen from fig. 3 and fig. 1, at the moment, the discharge tube enabling signal DFEN controls a discharge tube drive 17 to output a DHC pin as a high level VDD1, and a discharge tube NM1 is opened; when the over-discharge is connected to the charger and is unplugged, the over-discharge signal UVP is at a high level, the charger connection signal CHAIN is changed into a low level, the charging current connection signal ICHA is changed into a low level, the output A401 is changed into a low level through the AND gate U402, the discharge tube enabling signal DFEN output by the over-discharge signal UVP is changed into a low level through the inverter U403 and the OR gate U404, as can be seen from fig. 3 and fig. 1, the discharge tube enabling signal DFEN controls the discharge tube drive 17 to output the DHC pin as a low level, and the discharge tube NM1 is closed.
The above is only the best embodiment of the present invention, and does not constitute any limitation to the present invention, and it is obvious that various changes and modifications can be made to the circuit thereof under the concept of the present invention, but these are all protected by the present invention.