CN212381445U

CN212381445U - LED drive circuit

Info

Publication number: CN212381445U
Application number: CN202021625096.8U
Authority: CN
Inventors: 夏虎; 崔凤敏
Original assignee: Shanghai Natlinear Electronics Co ltd
Current assignee: Shanghai Natlinear Electronics Co ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2021-01-19
Anticipated expiration: 2030-08-07

Abstract

The utility model provides a LED drive circuit, include: the mode control module is used for sampling the voltage of the positive electrode of the battery and comparing the voltage based on the first reference voltage and the second reference voltage to generate a mode control signal so as to control the LED driving circuit to work in different modes; the LED driving circuit comprises an enabling signal generating module, a driving control module and a switching tube, wherein the enabling signal generating module is used for generating an enabling signal to start the driving control module when the LED driving circuit works in a conventional driving mode and generating an enabling signal to control the switching tube to be turned off when the LED switching control signal is effective, and the driving control module is turned off when the LED driving circuit works in an over-discharge protection mode; the driving control module is used for generating a driving signal based on the enabling signal to control the switch tube to be conducted when the LED driving circuit works in a conventional driving mode; and the regulating and controlling module is used for generating an output sink current based on the difference value of the battery positive voltage and the third reference voltage so as to regulate and control the magnitude of the driving signal when the enabling signal is effective.

Description

LED drive circuit

Technical Field

The utility model relates to an integrated circuit design field especially relates to a LED drive circuit.

Background

At present, a plurality of portable lighting driving electric appliances which use a battery as a power supply and use LED lamp beads as light sources, such as emergency lamps, flashlights, stall lights and the like, appear on the market. When the lighting driving electric appliance is used, the service life of the battery can be greatly influenced by the thorough exhaustion of the electric quantity of the battery, and even the battery is damaged; therefore, a battery over-discharge protection circuit is usually connected between the two poles of the battery. When the battery over-discharge protection circuit detects that the battery voltage is lower than the over-discharge protection threshold, the discharging path is disconnected to stop discharging the battery; the over-discharge protection threshold voltage is typically 2.7V for a 4.3V lithium battery, and 2.2V for a 3.7V lithium battery.

Fig. 1 is a conventional LED driving circuit with an over-discharge protection function, which uses a battery as a power source to drive an LED; however, as the conduction voltage value of the LED lamp bead load is very close to the over-discharge protection threshold value of the battery, when the electric quantity of the battery is close to exhaustion and the over-discharge protection is started, the LED lamp may flicker, poor use experience is brought to a user, and even the problem that the user mistakenly thinks that the LED lamp breaks down is caused.

The reason why the LED driving circuit with the over-discharge protection function shown in fig. 1 causes the LED lamp to flicker is analyzed as follows:

the battery has internal resistance, and the battery in practical application can be equivalent to an ideal battery core BAT without resistance and a resistor R1 with certain resistance value which are connected in series. The voltage of the ideal battery cell is Vbat, and the resistor R1 is the equivalent series resistance of the battery, and when the battery discharges, a certain voltage drop is generated on the resistor R1.

The non-inverting input end of the hysteresis comparator A is connected with the positive electrode of the battery and used for detecting the voltage Vbatt of the positive electrode of the battery, and the first inverting input end and the second inverting input end of the hysteresis comparator A are respectively connected with a first reference voltage Vref1 and a second reference voltage Vref2, wherein Vref1 is less than Vref 2. When the battery is discharged and the battery positive voltage Vbat is reduced from being higher than Vref2 to being lower than Vref1, the output signal OD of the hysteresis comparator A is changed from high level to low level, and the LED drive circuit enters an over-discharge protection mode; when the battery is charged and the battery positive electrode voltage Vbat is increased from being lower than Vref1 to being higher than Vref2, the output signal OD of the hysteresis comparator A is changed from low level to high level, and the LED drive circuit exits from the over-discharge protection mode. Typically, Vref2 is only about 500mV higher than Vref1 in order to ensure that the battery has a wide operating voltage range.

When the output signal OD of the hysteresis comparator a is at a low level, the output signal EN of the AND gate AND is at a low level, the charge pump does not operate, the NMOS transistor N1 is turned off due to the gate voltage VG being pulled low, no current passes through the LED lamp, AND the LED lamp does not emit light; when the output signal OD of the hysteresis comparator a is at a high level AND the signal Switch is at a low level, the output signal EN of the AND gate AND is at a low level, the charge pump does not operate, the NMOS transistor N1 is turned off because the gate voltage VG is pulled low, no current passes through the LED lamp, AND the LED lamp does not emit light; when the output signal OD of the hysteresis comparator a is at a high level AND the signal Switch is at a high level, the output signal EN of the AND gate AND is at a high level, the charge pump operates, the NMOS transistor N1 is turned on because the voltage difference between the gate AND the source is raised above its turn-on threshold, the battery supplies power to the LED lamp through the NMOS transistor N1, a current passes through the LED lamp, AND the LED lamp emits light; the signal Switch is a logic signal output by an external control circuit, and serves as a Switch control signal of the LED lamp.

When the LED lamp emits light, the electric quantity of a battery is consumed, the voltage Vbat of the battery core continuously drops, the voltage Vbat of the positive electrode of the battery is dropped along with the voltage Vbat, and the current passing through the LED lamp is I when the NMOS tube N1 is supposed to be conducted_LED；

When the voltage Vbatt of the positive electrode of the battery is reduced to be lower than Vref1, the output signal OD of the hysteresis comparator A is changed from high level to low level, and the LED driving circuit enters an over-discharge protection mode; at this time, the battery positive voltage Vbatp immediately before entering the over-discharge protection mode can be obtained as: vbatp _ before Vref1 Vbat-I_LED*R1；

When the LED drive circuit enters an over-discharge protection mode, the NMOS tube N1 is turned off, and the current passing through the LED lamp is controlled by I_LEDBecomes 0; at this time, the battery positive voltage Vbatp at the moment after the over-discharge protection mode is entered can be obtained as: vbatp _ after ═ Vbat.

As can be seen from the above equation, after the LED driving circuit enters the over-discharge protection mode, the current passing through the LED lamp decreases to 0, the battery positive voltage Vbat increases, and the rising amplitude is I_LEDR1; if I_LED*R1>Vref2-Vref1，The transient battery positive voltage Vbatp-after may cause the LED driving circuit to enter the over-discharge protection mode>Vref2, so that the output signal OD of the hysteretic comparator a changes from low to high, and the LED driving circuit exits the over-discharge protection mode again.

After the LED driving circuit exits the over-discharge protection mode, the NMOS tube N1 is switched on again from off, and the current passing through the LED lamp is changed from 0 to I_LEDThe battery positive electrode voltage Vbatp is changed from Vbatp _ after to Vbatp _ before again, so that the LED driving circuit enters the over-discharge protection mode again. Such repeated entering and exiting of the over-discharge protection mode causes the repeated turning off and turning on of the LED lamp, which is seen by the user as the flickering phenomenon of the LED lamp.

Moreover, due to the fact that batteries on the market have different quality, the more the battery with the lower quality is, the larger the equivalent series resistance is, the higher the possibility of the LED flicker phenomenon is; and the greater the current through the LED lamp, the greater the likelihood of the above-described LED flicker phenomenon.

SUMMERY OF THE UTILITY MODEL

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an LED driving circuit for solving the problem of LED flickering caused by repeatedly entering and exiting the over-discharge protection mode.

To achieve the above and other related objects, the present invention provides a LED driving circuit connected between a battery and a LED, the LED driving circuit including: a mode control module, an enable signal generation module, a driving control module, a regulation and control module and a switch tube, wherein,

the mode control module is used for sampling the voltage of the positive electrode of the battery, comparing the voltage of the positive electrode of the battery based on a first reference voltage and a second reference voltage to generate a mode control signal so as to control the LED driving circuit to work in a conventional driving mode or an over-discharge protection mode; wherein the first reference voltage is less than the second reference voltage;

the enabling signal generating module is connected to the output end of the mode control module and is used for being controlled by an LED switch control signal when the LED driving circuit works in a conventional driving mode and generating an enabling signal when the LED switch control signal is effective so as to start the driving control module; when the LED driving circuit works in an over-discharge protection mode, the driving control module is closed to control the switching tube to be switched off;

the drive control module is connected to the output end of the enable signal generation module and used for generating a drive signal based on the enable signal to control the switch tube to be conducted when the LED drive circuit works in a conventional drive mode;

the regulation and control module is connected with the output end of the enabling signal generation module and the output end of the driving control module and is used for generating an output sink current based on the difference value of the battery positive voltage and the third reference voltage when the enabling signal is effective so as to regulate and control the magnitude of the driving signal; wherein the third reference voltage is greater than the first reference voltage.

Optionally, the regulatory module comprises: the control end of the amplifier is connected to the output end of the enabling signal generating module, the first input end of the amplifier is connected to the positive electrode voltage of the battery, the second input end of the amplifier is connected to the third reference voltage, and the output end of the amplifier serves as the output end of the regulating module.

Optionally, the mode control module includes: the positive voltage of the battery is connected to the non-inverting input end of the hysteresis comparator, the first inverting input end of the hysteresis comparator is connected to the first reference voltage, the second inverting input end of the hysteresis comparator is connected to the second reference voltage, and the output end of the hysteresis comparator serves as the output end of the mode control module.

Optionally, the mode control module includes:

the sampling comparison unit is used for sampling the voltage of the positive electrode of the battery and comparing the voltage of the positive electrode of the battery based on the first reference voltage and the second reference voltage to generate an initial control signal;

and the auxiliary control unit is connected to the output end of the sampling comparison unit and used for generating a mode control signal according to the initial control signal and the charging state detection signal so as to control the LED drive circuit to work in a conventional drive mode or an over-discharge protection mode.

Optionally, the sampling comparison unit includes: the positive voltage of the battery is accessed to the non-inverting input end of the hysteresis comparator, the first inverting input end of the hysteresis comparator is accessed to the first reference voltage, the second inverting input end of the hysteresis comparator is accessed to the second reference voltage, and the output end of the hysteresis comparator is used as the output end of the sampling comparison unit.

Optionally, the auxiliary control unit comprises: the input end of the phase inverter is connected to the output end of the sampling comparison unit, the output end of the phase inverter is connected to the zero clearing end of the RS trigger, the set end of the RS trigger is connected to the charging state detection signal, and the output end of the RS trigger is used as the output end of the mode control module; the RS trigger is composed of two NAND gates.

Optionally, the enable signal generating module includes: and the first input end of the AND gate is connected with the LED switch control signal, the second input end of the AND gate is connected with the output end of the mode control module, and the output end of the AND gate is used as the output end of the enabling signal generation module.

Optionally, the drive control module includes: and the input end of the charge pump is connected to the output end of the enabling signal generation module, and the output end of the charge pump is used as the output end of the drive control module.

As described above, the utility model discloses a LED drive circuit, through the design of regulation and control module, make the electric current of flowing through LED follow the battery positive voltage and change and be close to for 0 when the battery gets into the overdischarge protection mode, thereby reduce the range of rising back of the battery positive voltage after LED closes, make the LED close the back battery can not withdraw from the overdischarge protection mode because of its positive voltage rises back, avoided the battery because of getting into repeatedly and withdraw from the overdischarge protection mode and cause LED to close repeatedly and light, avoided LED to appear the scintillation problem promptly. Meanwhile, the battery is locked after entering the over-discharge protection mode through the design of the mode control module, the over-discharge protection mode can be exited to enter the conventional driving mode only when the battery is in a charging state and the electric quantity is sufficient, the problem that the LED is repeatedly turned off and turned on due to repeated entering and exiting of the battery in the over-discharge protection mode is avoided, and the LED flickers is avoided.

Drawings

Fig. 1 is a circuit diagram of a conventional LED driving circuit with an over-discharge protection function.

Fig. 2 shows a circuit diagram of the LED driving circuit of the present invention.

In fig. 3, (a) shows do the utility model discloses amplifier output sink current is along with battery positive voltage change curve schematic diagram when LED drive circuit uses, (b) shows do the utility model discloses LED drive circuit flows through LED's current is along with battery positive voltage change curve schematic diagram when using.

Fig. 4 shows another circuit diagram of the LED driving circuit of the present invention.

Description of the element reference numerals

100 mode control module

101 sampling comparison unit

102 auxiliary control unit

200 enable signal generation module

300 drive control module

400 adjustment module

Detailed Description

The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to fig. 2 to 4. It should be noted that the drawings provided in the present embodiment are only schematic and illustrative of the basic idea of the present invention, and although the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of the components in actual implementation may be changed at will, and the layout of the components may be more complicated.

Example one

As shown in fig. 2, the present embodiment provides an LED driving circuit connected between a battery and an LED, the LED driving circuit including: a mode control module 100, an enable signal generating module 200, a driving control module 300, a regulation and control module 400 and a switch tube 500, wherein,

the mode control module 100 is configured to sample a battery positive voltage Vbatp, and compare the battery positive voltage Vbatp based on a first reference voltage Vref1 and a second reference voltage Vref2 to generate a mode control signal pro, so as to control the LED driving circuit to operate in a normal driving mode or an over-discharge protection mode; wherein the first reference voltage Vref1 is less than the second reference voltage Vref 2;

the enable signal generating module 200 is connected to an output end of the mode control module 100, and is configured to be controlled by an LED switch control signal switch when the LED driving circuit operates in a normal driving mode, and generate an enable signal EN when the LED switch control signal switch is active to turn on the driving control module 300; when the LED driving circuit works in the over-discharge protection mode, the driving control module 300 is turned off to control the switching tube 500 to be turned off;

the driving control module 300 is connected to the output end of the enable signal generating module 200, and is configured to generate a driving signal VG based on the enable signal EN to control the switching tube 500 to be turned on when the LED driving circuit operates in the normal driving mode;

the regulation and control module 400 is connected to the output end of the enable signal generation module 200 and the output end of the driving control module 300, and is used forWhen the enable signal EN is effective, an output sink current Iout is generated based on the difference value of the battery positive voltage Vbat p and the third reference voltage Vref3 so as to regulate the magnitude of the driving signal VG, and therefore the regulation of the current I flowing through the LED is realized_LED(ii) a Wherein the third reference voltage Vref3 is greater than the first reference voltage Vref 1.

As an example, as shown in fig. 2, the mode control module 100 includes: a hysteresis comparator a, a non-inverting input terminal of which is connected to the battery positive voltage Vbatp, a first inverting input terminal of which is connected to the first reference voltage Vref1, a second inverting input terminal of which is connected to the second reference voltage Vref2, and an output terminal of which is used as an output terminal of the mode control module 100. In this example, when the battery is in a discharging state, if the battery positive voltage Vbatp drops from being higher than the second reference voltage Vref2 to being lower than the first reference voltage Vref1, the mode control signal pro output by the hysteresis comparator a changes from a high level to a low level, at this time, the battery enters an over-discharge protection mode, and the LED driving circuit operates in the over-discharge protection mode; when the battery is in a charging state, if the battery positive voltage Vbat is increased from being lower than the first reference voltage Vref1 to being higher than the second reference voltage Vref2, the mode control signal pro output by the hysteresis comparator A is changed from a low level to a high level, at this time, the battery exits the over-discharge protection mode and enters a normal driving mode, and the LED driving circuit works in the normal driving mode.

As an example, as shown in fig. 2, the enable signal generation module 200 includes: AND an AND gate AND, a first input terminal of which is connected to the LED switch control signal switch, a second input terminal of which is connected to the output terminal of the mode control block 100, AND an output terminal of which is used as the output terminal of the enable signal generation block 200. In this example, when the LED driving circuit operates in the normal driving mode, the mode control signal pro output by the mode control module 100 is at a high level, and at this time, the enable signal generating module 200 controls the driving control module 300 to be turned on or off based on the LED switch control signal switch; if the LED switch control signal switch is at a high level, the AND gate AND performs an AND operation on the LED switch control signal switch AND the mode control signal pro to output a high-level enable signal to turn on the driving control block 300, AND if the LED switch control signal switch is at a low level, the AND gate AND performs an AND operation on the LED switch control signal switch AND the mode control signal pro to output a low level to turn off the driving control block 300. When the LED driving circuit operates in the over-discharge protection mode, the mode control signal pro output by the mode control module 100 is at a low level, AND at this time, the output of the AND gate AND is at a low level, so that the driving control module 300 is directly turned off. It should be noted that the LED switch control signal switch is a logic signal generated by an external circuit, which indicates that the user selects to turn on the LED when it is high, and indicates that the user selects to turn off the LED when it is low.

As an example, as shown in fig. 2, the driving control module 300 includes: and a charge pump, an input end of which is connected to an output end of the enable signal generation module 200, and an output end of which is used as an output end of the driving control module 300. In this example, the charge pump is turned on when the enable signal generating module 200 outputs a high level (i.e., generates an enable signal) to generate a driving signal to control the switching tube 500 to be turned on, and turned off when the enable signal generating module 200 outputs a low level, at this time, the charge pump turns off the switching tube 500 due to non-operation.

As an example, as shown in fig. 2, the regulatory module 400 includes: and an amplifier OP, a control end of which is connected to the output end of the enable signal generation module 200, a first input end of which is connected to the battery positive voltage Vbatp, a second input end of which is connected to the third reference voltage Vref3, and an output end of which is used as the output end of the regulation module 400. Specifically, the amplifier OP is a low-gain amplifier, so that the output sink current Iout of the amplifier OP is slowly increased along with the decrease of the battery positive voltage Vbatp, the current flowing through the LED is slowly reduced, and the problem of flicker caused by rapid brightness change of the LED is avoided. In this example, the amplifier OP is controlled by the output of the enable signal generation module 200, and the output of the enable signal generation module 200 isWhen the level is low, the output sinking current Iout of the amplifier OP is 0; when the output of the enable signal generating module 200 is at a high level (i.e., the enable signal EN is active), the output sink current Iout of the amplifier OP is determined by a difference between two input signals (i.e., the battery positive voltage Vbatp and the third reference voltage Vref3), so that the output current of the driving control module 300 is discharged based on the output sink current Iout, and the magnitude of the driving signal VG is adjusted and controlled, thereby adjusting and controlling the current I flowing through the LED_LED. The current I flowing through the LED is regulated and controlled by the output sinking current Iout_LEDSo that the current I flowing through the LED_LEDThe battery voltage Vbat is changed along with the battery positive voltage Vbat and is close to 0 when the battery enters the over-discharge protection mode, so that the rising range of the battery positive voltage Vbat after the LED is turned off is reduced, the battery can not exit the over-discharge protection mode due to the rising of the battery positive voltage after the LED is turned off, the problem that the LED is turned off and on repeatedly due to the fact that the battery enters and exits the over-discharge protection mode repeatedly is avoided, and the problem that the LED flickers is solved.

As an example, as shown in fig. 2, the switching tube 500 is an NMOS tube N1, a gate terminal of the NMOS tube N1 is connected to the output terminal of the driving control module 300, a drain terminal of the NMOS tube N1 is connected to the battery positive voltage Vbatp, and a source terminal of the NMOS tube N1 is connected to an anode terminal of the LED; of course, in other examples, the switching tube 500 may also be a PMOS tube, and at this time, the gate terminal of the PMOS tube is connected to the output terminal of the driving control module 300, the source terminal of the PMOS tube is connected to the battery positive voltage Vbatp, and the drain terminal of the PMOS tube is connected to the anode terminal of the LED.

The operation principle of the LED driving circuit according to the present embodiment is described with reference to fig. 2 and fig. 3.

When the battery is in a discharging state, if the battery positive voltage Vbat is reduced to be lower than the first reference voltage Vref1 from being higher than the second reference voltage Vref2, the mode control signal pro output by the hysteresis comparator A is changed from a high level to a low level, and the battery enters an over-discharge protection mode; at this time, the AND gate AND outputs a low level, the charge pump does not operate, the NMOS transistor N1 is turned off because the gate terminal is pulled low to zero, AND the LED does not emit light because no current flows.

When the battery is in a charging state, if the battery positive voltage Vbat is increased from being lower than a first reference voltage Vref1 to being higher than a second reference voltage Vref2, the mode control signal pro output by the hysteresis comparator A is changed from a low level to a high level, and the battery exits from an over-discharge protection mode and enters a normal driving mode; at this time, if the LED switch control signal switch is at low level, the AND gate AND outputs low level, the charge pump does not operate, the NMOS transistor N1 is turned off because the gate terminal is pulled low to zero, AND the LED does not emit light because no current flows; if the LED switch control signal switch is at a high level, the AND gate AND outputs the high level, the charge pump works, the NMOS tube N1 is conducted because the voltage difference between the grid end AND the source end is raised to be larger than the opening threshold, the battery supplies power to the LED through the NMOS tube N1, AND the LED emits light because current flows through the LED;

when the LED emits light, the electric quantity of a battery is consumed, the voltage Vbat of the battery core continuously drops, the voltage Vbat of the positive electrode of the battery is dropped along with the voltage Vbat, and at the moment, the current flowing through the LED when the NMOS tube N1 is switched on is assumed to be I_LED；

When the battery positive voltage Vbatp is much higher than the third reference voltage vref3, the output sink current Iout of the amplifier OP is 0, and the gate terminal voltage of the NMOS transistor N1 is determined only by the output current capability of the charge pump; at this time, since the gate terminal of the NMOS transistor N1 has no drain path, the gate terminal voltage of the NMOS transistor N1 is very high, so that the on-resistance Rdson of the NMOS transistor N1 is small, and the current I flowing through the LED is small_LEDThe maximum value is that the battery power is sufficient at the moment, and the LED can be normally driven to illuminate;

as the battery power decreases, when the battery positive voltage Vbatp decreases to approach the third reference voltage vref3, the output sink current Iout of the amplifier OP gradually increases, and at this time, a part of the output current of the charge pump is discharged by the output sink current Iout of the amplifier OP, so the gate terminal voltage of the NMOS transistor N1 decreases, the on-resistance Rdson of the NMOS transistor N1 increases, and the current I flowing through the LED increases_LEDDecrease;

as the battery charge continues to decrease, when the battery positive voltage Vbatp falls below the third reference voltage vref3 and equals the first reference voltage vref1, the output sink current Iout of the amplifier OP is large,at this time, most of the output current of the charge pump is discharged by the output sink current Iout of the amplifier OP, so the gate terminal voltage of the NMOS transistor N1 is very low, and thus the on-resistance Rdson of the NMOS transistor N1 is very large, and the current I flowing through the LED is very low_LEDDecreasing to near 0.

When the battery positive voltage Vbatt falls below a first reference voltage vref1, the output of the hysteresis comparator A changes from high level to low level, and the battery enters an over-discharge protection mode;

immediately before the battery enters the over-discharge protection mode, the voltage value Vbat _ before (Vref 1) of the positive electrode of the battery is Vbat-I_LEDR1; after the battery enters the over-discharge protection mode, the NMOS tube N1 is turned off, and the current flowing through the LED is changed from I_LEDWhen the voltage value becomes 0, namely the voltage value Vbat _ after of the battery at the moment after the battery enters the over-discharge protection mode is Vbat;

as can be seen from the above equation, after the battery enters the over-discharge protection mode, the current I flowing through the LED is used_LEDThe voltage Vbat is decreased to 0, and the voltage Vbat of the positive electrode of the battery is increased instead, and the increasing amplitude is I_LEDR1; however, due to the regulation of the amplifier OP, as the battery positive voltage Vbat drops to the first reference voltage vref1, the current I flowing through the LED_LEDAlso drops to approximately 0, at which time I_LEDR1 is small and satisfies I_LED*R1<Vref2-Vref 1; it can be seen that even though the battery positive voltage Vbatt rises after the battery enters the over-discharge protection mode, the voltage still satisfies Vbatt p because the rising amplitude is small<Vref2 so that the output of hysteretic comparator a remains low at all times, i.e., the battery is in an over-discharge protection mode at all times.

Example two

As shown in fig. 4, the difference between the present embodiment and the first embodiment is a mode control module, wherein the mode control module of the present embodiment includes:

a sampling comparison unit 101, configured to sample a battery positive voltage Vbatp, and compare the battery positive voltage Vbatp based on the first reference voltage Vref1 and the second reference voltage Vref2 to generate an initial control signal OD;

and the auxiliary control unit 102 is connected to the output end of the sampling comparison unit 101, and configured to generate a mode control signal pro according to the initial control signal OD and the charge state detection signal recharge, so as to control the LED driving circuit to operate in a conventional driving mode or an over-discharge protection mode.

Specifically, as shown in fig. 3, the sampling comparison unit 101 includes: a non-inverting input terminal of the hysteresis comparator a is connected to the battery positive voltage Vbatp, a first inverting input terminal of the hysteresis comparator a is connected to the first reference voltage Vref1, a second inverting input terminal of the hysteresis comparator a is connected to the second reference voltage Vref2, and an output terminal of the hysteresis comparator a serves as an output terminal of the sampling comparison unit 101. The auxiliary control unit 102 includes: the input end of the phase inverter inv is connected to the output end of the sampling comparison unit 101, the output end of the phase inverter inv is connected to the zero clearing end of the RS trigger, the set end of the RS trigger is connected to the charging state detection signal recharge, and the output end of the RS trigger is used as the output end of the mode control module 100; the RS flip-flop is composed of two NAND gates of NAND1 and NAND 2. In this example, when the battery is in a discharging state, if the battery positive voltage Vbatp is decreased from being higher than the second reference voltage Vref2 to being lower than the first reference voltage Vref1, the initial control signal OD output by the hysteresis comparator a is changed from a high level to a low level, the output of the inverter inv is changed to a high level, at this time, the RS flip-flop is cleared to zero because the charging state detection signal recharge is at a low level, the output signal of the RS flip-flop is changed from a high level to a low level, at this time, the battery enters an over-discharge protection mode, and the LED driving circuit operates in the over-discharge protection mode; when the battery is in a charging state, if the positive voltage Vbatt p of the battery rises from being lower than a first reference voltage Vref1 to being higher than a second reference voltage Vref2, the initial control signal OD output by the hysteresis comparator A changes from low level to high level, the output of the inverter inv changes to low level, at this time, because the charging state detection signal recharge is high level, the RS trigger is set, the output signal of the RS trigger changes from low level to high level, at this time, the battery exits from the overdischarge protection mode and enters a normal driving mode, and the LED driving circuit works in the normal driving mode. In the present example, by the design of the auxiliary control module 102, the mode control signal is generated by using the combined action of the initial control signal OD and the charging state detection signal recharge, so that the battery is locked after entering the overdischarge protection mode, and only when the battery is in the charging state and the electric quantity is sufficient, the battery can exit the overdischarge protection mode to enter the conventional driving mode, thereby avoiding the problem that the LED is repeatedly turned off and turned on due to the repeated entering and exiting of the overdischarge protection mode, i.e., avoiding the problem that the LED flickers. It should be noted that the charge state detection signal recharge is a logic signal generated by an external circuit for identifying whether the battery is charged or not; the charge state detection signal recharge is at a high level when the battery is in a charge state, otherwise the charge state detection signal recharge is at a low level.

To sum up, the utility model discloses a LED drive circuit, through the design of regulation and control module for the electric current of LED that flows through changes and is close to for 0 when the battery gets into the overdischarge protection mode along with battery positive voltage, thereby reduces the range of rising back of battery positive voltage after LED closes, makes the battery can not withdraw from the overdischarge protection mode because of its positive voltage rises back after LED closes, has avoided the battery to cause LED to close and light repeatedly because of getting into repeatedly and withdrawing from the overdischarge protection mode, has avoided LED to appear the scintillation problem promptly. Meanwhile, the battery is locked after entering the over-discharge protection mode through the design of the mode control module, the over-discharge protection mode can be exited to enter the conventional driving mode only when the battery is in a charging state and the electric quantity is sufficient, the problem that the LED is repeatedly turned off and turned on due to repeated entering and exiting of the battery in the over-discharge protection mode is avoided, and the LED flickers is avoided. Therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. An LED driving circuit connected between a battery and an LED, the LED driving circuit comprising: a mode control module, an enable signal generation module, a driving control module, a regulation and control module and a switch tube, wherein,

2. The LED driving circuit according to claim 1, wherein the regulation module comprises: the control end of the amplifier is connected to the output end of the enabling signal generating module, the first input end of the amplifier is connected to the positive electrode voltage of the battery, the second input end of the amplifier is connected to the third reference voltage, and the output end of the amplifier serves as the output end of the regulating module.

3. The LED driving circuit of claim 1, wherein the mode control module comprises: the positive voltage of the battery is connected to the non-inverting input end of the hysteresis comparator, the first inverting input end of the hysteresis comparator is connected to the first reference voltage, the second inverting input end of the hysteresis comparator is connected to the second reference voltage, and the output end of the hysteresis comparator serves as the output end of the mode control module.

4. The LED driving circuit of claim 1, wherein the mode control module comprises:

5. The LED driving circuit according to claim 4, wherein the sampling comparison unit comprises: the positive voltage of the battery is accessed to the non-inverting input end of the hysteresis comparator, the first inverting input end of the hysteresis comparator is accessed to the first reference voltage, the second inverting input end of the hysteresis comparator is accessed to the second reference voltage, and the output end of the hysteresis comparator is used as the output end of the sampling comparison unit.

6. The LED driving circuit according to claim 4, wherein the auxiliary control unit comprises: the input end of the phase inverter is connected to the output end of the sampling comparison unit, the output end of the phase inverter is connected to the zero clearing end of the RS trigger, the set end of the RS trigger is connected to the charging state detection signal, and the output end of the RS trigger is used as the output end of the mode control module; the RS trigger is composed of two NAND gates.

7. The LED driving circuit according to claim 1, wherein the enable signal generating module comprises: and the first input end of the AND gate is connected with the LED switch control signal, the second input end of the AND gate is connected with the output end of the mode control module, and the output end of the AND gate is used as the output end of the enabling signal generation module.

8. The LED driving circuit according to claim 1, wherein the driving control module comprises: and the input end of the charge pump is connected to the output end of the enabling signal generation module, and the output end of the charge pump is used as the output end of the drive control module.