阅读说明：本技术 一种led驱动电路 (LED drive circuit ) 是由 夏虎 崔凤敏 于 2020-08-07 设计创作，主要内容包括：本发明提供一种LED驱动电路,包括：模式控制模块,用于采样电池正极电压并基于第一、第二基准电压对该电压进行比较处理产生模式控制信号以控制LED驱动电路工作于不同模式下；使能信号产生模块,用于在LED驱动电路工作于常规驱动模式时,受控于LED开关控制信号并在LED开关控制信号有效时产生使能信号以开启驱动控制模块,在LED驱动电路工作于过放保护模式时关闭驱动控制模块以控制开关管关断；驱动控制模块,用于在LED驱动电路工作于常规驱动模式时,基于使能信号产生驱动信号以控制开关管导通；调控模块,用于在使能信号有效时,基于电池正极电压和第三基准电压的差值产生输出沉电流以此来调控驱动信号的大小。(The present invention provides an LED driving circuit, including: 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.)

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,

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.

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:

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.

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.

Technical Field

The invention relates to the field of integrated circuit design, in particular to an LED driving 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 causes the battery positive voltage Vbat ═ Vbat _ after the instant when the LED driving circuit enters 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 changed from being turned off againOn, 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.

Disclosure of Invention

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

To achieve the above and other related objects, the present invention provides 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,

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, according to the LED driving circuit of the present invention, through the design of the regulation and control module, the current flowing through the LED changes along with the voltage of the positive electrode of the battery and approaches to 0 when the battery enters the overdischarge protection mode, so that the rising range of the voltage of the positive electrode of the battery after the LED is turned off is reduced, the battery does not exit the overdischarge protection mode due to the rising of the voltage of the positive electrode of the battery after the LED is turned off, and the problem of the flicker of the LED caused by the repeated turning off and turning on of the battery due to the repeated entering and exiting of the overdischarge protection mode is avoided. 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 is a circuit diagram of an LED driving circuit according to the present invention.

Fig. 3 (a) shows a schematic diagram of a curve of an output sink current of an amplifier with a voltage variation of a positive electrode of a battery when the LED driving circuit of the present invention is applied, and (b) shows a schematic diagram of a curve of a current flowing through an LED with a voltage variation of a positive electrode of a battery when the LED driving circuit of the present invention is applied.

Fig. 4 is a circuit diagram of another LED driving circuit according to 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 embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope 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 illustrate 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 arbitrarily, and the layout of the components may be more complicated.