The control of single-lithium-battery electric tool and protective circuit and detection thereof, control method
The present invention relates to a kind of lithium electricity electric tool, particularly a kind of control of lithium electricity electric tool and protective circuit and detection thereof, control method.
The utilization of direct current electric power tools, directly substituted hand tools, alleviated people's operation labor intensity, improved operating efficiency, particularly adopt the direct current electric power tools of power-type lithium ion battery, alleviated especially the weight of electric tool, improved the service life cycle of battery, the demand that meets environmental protection is subject to liking of people.
Power-type lithium ion battery is due to the characteristic of self, at charge and discharge process, cell voltage, discharging current and temperature there is strict requirement, exceed specification requirement, light shorten the charge and discharge cycles useful life of battery or damage battery, heavy might cause and catch fire or the generation of the security incident such as blast.Because the common volume of electric tool that adopts single-unit (nominal voltage 3.6V) power-type lithium ion battery is small and exquisite, battery all adopts non-removable mode to be fixedly mounted in electric tool, and for this reason, the protection and control circuit also must be arranged in electric tool.
Traditional method with the single-unit lithium ion battery in Power Tools Industries is to adopt the former IC that is designed for the single-unit protection use of mobile phone digital class to do to control and protection.because general single-unit protection IC designs for the mobile phone digital series products, fill during work, discharging current is little, discharge load is resistive load substantially, discharge steadily, need not make temperature protection function, and the load of single-lithium-battery direct current electric power tools is brush direct current motor, has discharging current large, in battery operated process, temperature rises fast, during motor rotation, electric spark disturbs large, the special high of motor back-emf, so there is the incomplete defective of defencive function in the protection scheme that adopts the IC that is used for the mobile phone digital class to make the single-lithium-battery direct current electric power tools, as without temperature protection function and multistage current protecting function, charge and discharge protecting voltage and discharge prevention current parameters are fixed and can't be changed by IC manufacturer, can't show the various work of electric tool and guard mode etc., user interface is unfriendly, the defectives such as safety and reliability are relatively low.
So; be used for the IC of mobile phone digital series products and be not suitable for the protection and control of lithium electricity electric tool; if add in addition the circuit such as temperature protection function, multistage current protecting function, charging/discharging voltage and current protecting function; the circuit of whole system will become more complicated; components and parts increase greatly; essentially no installing space in electric tool is so practical value is little.
The circuit theory of common single-lithium-battery protection IC as shown in Figure 1, although simple in structure, when being used for lithium electricity electric tool, defencive function is not comprehensive, safety and reliability are low.
Summary of the invention
The invention discloses control and protective circuit that a kind of single-unit power-type lithium ion battery is used for electric tool; adopt single-chip microcomputer U2 to make master control IC; coordinate simple peripheral circuit that lithium electricity electric tool has been realized: charging control and management function, control of discharge management function, charging/discharging voltage defencive function, to discharge and recharge temperature protection function, charging overcurrent protection defencive function; the functions such as discharge multistage overcurrent protection function and each operating state demonstration, circuit theory of the present invention as shown in Figure 2.
Power supply circuits for single-chip microcomputer U2, traditional way is to adopt the 3.3V of voltage stabilizing or the power supply of 5V to power to single-chip microcomputer, and the present invention utilizes the normal working voltage scope of single-unit lithium ion battery between 2.5-4.2V, and the characteristic that can work between 2-5V of single-chip microcomputer, directly adopt the mode of cell voltage power supply to come to make the single-chip microcomputer steady operation to the single-chip microcomputer power supply, also simplified the design of power supply simultaneously, reduce the components and parts cost, improved the reliability of system.
As shown in Figure 2, can produce larger electric spark when working disturbs due to brush direct current motor, if do not add processing, can cause the Single Chip Microcomputer (SCM) program pointer to run and fly, have a strong impact on the security of system operation, for eliminating this impact, fly-wheel diode of positive and negative terminal reverse parallel connection in motor M 1, to eliminate the back electromotive force of motor, be parallel with the capacitor C 1 of number 10 microfarads at the positive and negative end of battery BT1, the impulse disturbances in the time that most of motor commutation can being absorbed.
As shown in Figure 2, add a RC low-pass filter circuit that is formed by resistance R 16, capacitor C 12 in the VB of single-chip microcomputer U2 current supply circuit, can guarantee that single-chip microcomputer U2 work is not subjected to motor M 1 and various outside interference, improves Systems balanth and reliability.
Be to remove to detect cell voltage with the reference voltage that stable single-chip microcomputer supply power voltage or external reference voltage are done AD conversion for the traditional method of the voltage detecting circuit of battery charging and discharging, the detected voltage of General Requirements can not be higher than reference voltage.
as shown in Figure 2, the present invention is powered to precision voltage reference U1 by resistance R 10 current limlitings by an IO mouth of single-chip microcomputer, the 2.495V of U1 output makes external reference voltage, make benchmark with cell voltage (single-chip microcomputer U2 supply power voltage), by detecting the voltage of external reference source, thereby adopt Backstepping to reach the purpose that detects cell voltage, to realize the high accuracy testing requirement to charging voltage, and generally be located at 2.5-2.7V due to the Cross prevention electrical voltage point in discharge process, when cell voltage drops to 2.5V, accurate external voltage reference source U1 (TL431) can't provide accurately voltage, due to the operating current of power tool motor at least more than several amperes, the voltage accuracy of discharge prevention point requires relative charging voltage precision low, so when discharge prevention, with cell voltage (single-chip microcomputer U2 supply power voltage) benchmark for referencial use, by detecting the anti-cell voltage that pushes away of voltage of voltage regulation of the inner 1.2V of single-chip microcomputer U2, can guarantee that single-chip microcomputer can detect cell voltage relatively accurately when 2V is above, thereby realize the Cross prevention function.
As shown in Figure 2, the battery charging and discharging temperature sensing circuit adopts stable 2.495V voltage to provide power supply for the series loop of resistance R 11 and negative tempperature coefficient thermistor NTC, with the low-pass filter circuit of resistance R 12 with capacitor C 4 compositions, AD mouth by single-chip microcomputer U2 is made the voltage of this point of benchmaring with outside 2.495V, by the detection of the conversion of the software in single-chip microcomputer U2 realization to battery temperature.
As shown in Figure 2, for reducing the current supply circuit internal resistance, directly adopt the internal resistance R of discharge metal-oxide-semiconductor Q4
DSMake current sampling resistor, after making low-pass filtering by resistance R 8 and capacitor C 3, give the IIN pin (AD mouth) of single-chip microcomputer U2 and make current detecting.
as shown in Figure 2, control triode Q3 by the charging of NPN type, charging metal-oxide-semiconductor Q1, Q2, resistance R 1, R2 and R3 form charging and control and buffer circuit, charging metal-oxide-semiconductor Q1 is connected with the drain electrode of Q2, share gate pole controlling composition charge switch and isolation, when triode Q3 conducting is controlled in charging, charging metal-oxide-semiconductor Q1 and Q2 conducting simultaneously, begin charging, when triode Q3 cut-off is controlled in charging, charging metal-oxide-semiconductor Q1 and Q2 turn-off simultaneously, stop charging, such design makes the internal resistance of charge circuit very low, conduction voltage drop is little, can fully the charge circuit of battery and front be isolated during shutoff, charge efficiency can be improved and quiescent dissipation can be reduced again simultaneously.
As shown in Figure 2, can control the running of motor and stop by the break-make of single-chip microcomputer U2 controlled discharge metal-oxide-semiconductor Q4, can change the rotation direction of motor by operative combination control switch S1.
As shown in Figure 2, single-chip microcomputer U2 dormancy control and awakening method are disclosed.When cell voltage is normal, the program of single-chip microcomputer U2 detects the insertion that there is no charger, when combination control switch S1 does not press yet, program control single-chip microcomputer U2 closes the power supply of outside precision voltage reference U1, charge closing is controlled triode Q3 and discharge metal-oxide-semiconductor Q4 simultaneously, enter the resting state of low-power consumption, the complete machine quiescent current is less than 1 microampere, and when charger or combination control switch S1 press, VIN pin or the IIN pin of single-chip microcomputer U2 will become high level by low level, single-chip microcomputer U2 is waken up, begin normal charge or discharge process.
As shown in Figure 2, form the charged state indicator light by the dichromatic LED 2LED1 in external charger, circuit and resistance R 13, R14, when cell voltage during less than 2V, dual-colored LED conducting is simultaneously carried out precharge with little electric current to battery, red and green color luminous mixed display simultaneously is orange, when voltage during greater than 2V, enter normal charging condition, this moment when red, green light goes out, the charging complete after red light go out, green light is bright, when occurring temperature in charging process and exceeding, red light dodges, and significantly points out to give the user.During discharge, white light emitting diode LED1 is bright, and is any when abnormal when occurring, and as under-voltage, overtemperature and when crossing flow short-circuit, white light emitting diode LED1 is glittering with different frequencies and duty ratio (glittering time), with the abnormal generation of call user's attention.
Compare with the scheme that adopts NI-G and Ni-MH battery to make power supply: adopt the electric tool of lithium battery owing to having environmental protection and energy saving, lightweight, easy to use, operating efficiency is high, and each discharges and recharges the advantages such as the discontinuous running number of times is more; Adopt single-chip microcomputer U2 to control with protective circuit and make Functional Design more flexible, control circuit is more reliable, use safer, the characteristics such as circulating battery longer service life.
This programme is made single-chip microcomputer U2 the master control IC of protection and control circuit; compare with the way of traditional single-unit protection IC: circuit has the protection and control complete function, circuit complexity reductions, electronic component minimizing, cost, safety and reliability raising, characteristics such as power consumption hardly when circuit is not worked.
Description of drawings
Fig. 1 is the circuit theory diagrams of single-unit protection IC;
Fig. 2 is the circuit theory diagrams of single-lithium-battery electric tool control of the present invention and protective circuit.
Further illustrate below in conjunction with the operation principle of circuit theory diagrams to the single-lithium-battery electric tool:
Resting state: when cell voltage is normal, Single Chip Microcomputer (SCM) program detects the insertion that there is no charger, when combination control switch S1 does not press yet, the program control single-chip microcomputer cuts out the power supply of outside precision voltage reference U1, and charge closing is controlled triode Q3 and discharge metal-oxide-semiconductor Q4 simultaneously, enters the resting state of low-power consumption, the complete machine quiescent current is less than 1 microampere, after single-chip microcomputer U2 is in resting state, even when cell voltage drops near 0V, still can remain on the resting state of low-power consumption.
charged state: when the constant-current constant-voltage charging device with 5V/1A inserts charging socket J1, when if cell voltage is following lower than 2V, because single-chip microcomputer U2 has been in resting state, cisco unity malfunction, this moment, charger was anodal by restorable insurance element PTC, diode D2, dichromatic LED 2LED1, resistance R 13, draw the diode pair battery to carry out the low current charge of several milliamperes on the parasitism of the LEDG of R14 and single-chip microcomputer and LEDR pin inside, in order to can rise by activated batteries voltage, dual-colored LED traffic lights while this moment bright light, be shown as orange, be expressed as in the low current charge activation, if cell voltage is raised to 2V when above, the electrify restoration circuit of single-chip microcomputer U2 inside can will produce the electrification reset action, single-chip microcomputer U2 in dormancy is waken up, make it to begin normal operation, after detecting high level, the VIN of single-chip microcomputer U2 pin enters charging procedure, single-chip microcomputer U2 will open precision voltage reference U1 and COUT pin output high level makes charging control triode Q3 conducting, thereby make charging metal-oxide-semiconductor Q1 and Q2 conducting, constant-current constant-voltage charging device from DC socket is charged to battery, the while when red, expression is charged.if cell voltage is lower than 2.5V, the COUT pin is exported the PWM modulating wave, namely carry out trickle charge with less average current, otherwise directly export high level and carry out quick charge, when charging voltage during soon near 4.2V, software adjustment PWM modulating wave makes it to carry out constant voltage charge, until the PWM duty ratio is when arriving setting-up time lower than the charging timer of set point or single-chip microcomputer inside, COUT pin output low level, thereby making charging control triode Q3 shutoff makes charging metal-oxide-semiconductor Q1 and Q2 turn-off cut-off, stop charging and close the power supply of precision voltage reference U1, the bright expression charging of green light is simultaneously completed.If charger is not dialled down, green light is always bright, and because charge metal-oxide-semiconductor Q1 and Q2 end simultaneously, the power supply that green light and charger voltage detect the loop is to be provided by charger, and single-chip microcomputer enters resting state, to reduce the loss of battery.
The charge protection state: single-chip microcomputer is attached to the negative tempperature coefficient thermistor NTC of battery surface by detection in charging process; the battery surface temperature being detected exceeds when protecting temperature; charge closing metal-oxide-semiconductor Q1 and Q2 are suspended charging; and red light begins flicker; and when the temperature retrieval normal range (NR); recover charging; set a charging timer by scm software; when the charging interval has reached the timing battery and has not reached yet 4.2V voltage; automatically stop charging, to protect the safety of lithium ion battery.If charging current is excessive, the insurance of the recovery certainly PTC resistance of going here and there in charge circuit becomes very large, turn-offs light source of charger, and indicator light will extinguish simultaneously, and single-chip microcomputer detects when there is no charging voltage, will automatically enter resting state.
motor discharge condition: because single-chip microcomputer at ordinary times is in resting state, discharge metal-oxide-semiconductor Q4 is in closed condition, when combination control switch S1 presses, cell voltage will be added to by the coil resistance of motor the drain electrode of discharge metal-oxide-semiconductor Q4, the high level of this point has been added to the IIN pin of single-chip microcomputer U2 by resistance R 8, single-chip microcomputer U2 is waken up, single-chip microcomputer U2 will open precision voltage reference U1, and unlatching discharge metal-oxide-semiconductor Q4, enter the discharge condition of motor rotation, white light LEDs 1 will be lighted, in order to help illumination and indication to use as the attached of instrument, after combination control switch S1 discharges, single-chip microcomputer U2 can't detect discharging current, to turn-off discharge metal-oxide-semiconductor Q4, turn-off the power supply of precision voltage reference U1, close white light LEDs 1, automatically enter resting state.
Motor discharge prevention state: be provided with the defencive functions such as under-voltage, the overtemperature of discharge and multistage overcurrent by scm software; in the process of discharge; single-chip microcomputer U2 software cycles detects cell voltage, temperature and discharging current; exceed the time of the protection value of setting and delay adjustments when wherein any one after; to turn-off discharge metal-oxide-semiconductor Q4; turn-off the power supply of precision voltage reference U1; white lamp LED1 of while automatically entered resting state and locks constant after the time by the flicker frequency flicker setting of setting.Restart motor M 1 as need, after only needing to discharge combination control switch S1, again press combination control switch S1 and get final product, if when this moment, all protective conditions did not satisfy, motor M 1 turned round again.
Above disclosed is only a kind of preferred embodiment of the present invention, certainly can not limit with this interest field of the present invention, and the equivalent variations of therefore doing according to claim of the present invention still belongs to the scope that the present invention is contained.