Headlamp driving circuit based on constant current driving and headlamp

Abstract

The invention relates to the technical field of automobile illuminating lamps, and discloses a headlamp driving circuit based on constant current driving and a headlamp, and the headlamp driving circuit comprises a headlamp input unit which is suitable for being connected with a whole vehicle power supply to obtain a first power supply signal; the constant current detection unit is configured to perform voltage detection on the first power supply signal and generate a switching signal under the condition that a detection result is lower than a voltage limit value; the boost topology unit is configured to perform boost processing on the first power supply signal and output a boosted second power supply signal; and the power supply switching unit is configured to cut off the connection between the whole vehicle power supply and the headlamp according to the switching signal, and connect the boost topology unit with the headlamp so as to provide the second power supply signal to the headlamp for lightening. According to the invention, through voltage detection and boost processing and in combination with the power supply switching unit, continuous and stable lighting of the LED is ensured.

Description

Technical Field

[0001] The present application relates to the field of automobile lighting technology, and in particular to a headlamp driving circuit and a headlamp based on constant current driving. Background Art

[0002] Car headlights are installed on both sides of the car head, mainly used to illuminate the road to provide the driver with road information ahead. They must not only meet regulatory requirements, but also facilitate driving. LEDs have the advantages of high brightness, low power consumption and long life, so they are increasingly used in car headlights and other automotive lighting. The working characteristics of LEDs require stable driving current and suitable operating voltage. Therefore, in order to ensure the driver's driving safety and driving experience, the design of the headlights must not only ensure brightness, but also ensure stable power supply current and voltage.

[0003] In order to prevent the power supply voltage from being insufficient when the car is running at a low speed or the battery voltage drops, which may cause the LED brightness to be low or cause flickering, in the relevant technology, the LED driver design generally uses a single boost channel to boost the power supply voltage to drive the LED to light up. However, this single boost channel causes the power supply voltage to be boosted even if it is at a normal level, which may cause the voltage driving the LED to be too high, increasing the risk of damage to the LED, thereby affecting the vehicle driving experience and driving safety. Summary of the invention

[0004] The present application provides a headlamp driving circuit and a headlamp based on constant current drive, which solves the technical problem that the current single boost processing of the power supply voltage leads to an increased risk of LED damage, thereby affecting the vehicle driving experience and driving safety. By adding a constant current detection unit for the input voltage, a boost topology unit and a power supply switching unit, it can automatically switch to the boost circuit under low voltage conditions, increase the power supply voltage to meet the headlamp lighting requirements, and at the same time, it can switch back to the normal driving circuit in time when the power supply voltage is normal, so as to ensure that the LED is continuously and stably lit and greatly improve the reliability of the headlamp, and achieve the technical effect of effectively coping with the adverse effects of automobile voltage fluctuations on LED lighting.

[0005] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0006] In a first aspect, an embodiment of the present application provides a headlight driving circuit based on constant current driving, the headlight driving circuit comprising:

[0007] A headlight input unit, wherein the headlight input unit is adapted to be connected to a vehicle power supply to obtain a first power supply signal;

[0008] a constant current detection unit, the constant current detection unit being configured to perform voltage detection on the first power supply signal and generate a switching signal when the detection result is lower than a voltage limit;

[0009] A boost topology unit, wherein the boost topology unit is configured to perform a boost process on the first power signal and output a boosted second power signal;

[0010] A power supply switching unit is configured to cut off the connection between the vehicle power supply and the headlight according to the switching signal, and connect the boost topology unit and the headlight to provide the second power supply signal to light the headlight.

[0011] The headlamp driving circuit proposed in the embodiment of the present application detects the supply voltage of the first power supply signal output by the vehicle power supply through the constant current detection unit, and switches the power supply line of the headlamp through the power supply switching unit according to the detection result, and connects the boost topology unit with the headlamp to provide the boosted second power supply signal to power the headlamp. Therefore, the present application can detect the situation of insufficient power supply voltage and automatically switch to the boost topology unit for power supply, so as to ensure that the headlamp can still obtain a stable power supply voltage under low voltage conditions, thereby avoiding the situation that the headlamp is affected by unstable voltage and has reduced brightness or flickering, and can also switch back to the connection between the vehicle power supply and the headlamp when it is detected that the power supply voltage is not lower than the voltage limit, so as to avoid the risk of overvoltage, and can greatly improve the reliability of the headlamp while ensuring the brightness and stability of the headlamp, thereby improving the driver's driving experience and ensuring driving safety.

[0012] Optionally, in some embodiments of the present application, the headlight drive circuit also includes a conversion unit, which is configured to convert the vehicle power supply to obtain a reference signal, wherein the reference signal is used to respectively power the constant current detection unit, the boost topology unit and the power supply switching unit and provide a reference voltage.

[0013] The embodiment of the present application converts the first power supply signal into a stable reference signal by setting a conversion unit. The reference signal is used to provide the required operating voltage for the constant current detection unit, the boost topology unit and the power supply switching unit, and provides a reference for the subsequent voltage detection and voltage boosting links, thereby ensuring that each unit in the headlight driving circuit can work continuously and stably under different input voltage conditions, thereby improving the reliability of the headlight driving circuit.

[0014] Optionally, in some embodiments of the present application, the constant current detection unit includes: a first comparator, wherein the negative input terminal of the first comparator is connected to the first power supply signal via a first resistor, the positive input terminal of the first comparator is connected to the reference signal via a second resistor, the output terminal of the first comparator is suitable for outputting the switching signal, and a first feedback resistor is connected between the output terminal of the first comparator and the positive input terminal of the first comparator.

[0015] The embodiment of the present application realizes voltage detection of the first power supply signal by setting a first comparator, and divides the reference signal according to the second resistor to obtain a comparison threshold, so that the phenomenon of insufficient power supply voltage can be quickly detected when the first power supply signal is lower than the comparison threshold, and the first comparator outputs a high level to automatically trigger the subsequent boosting link and power supply switching link, which is beneficial to ensure the stability of the headlamp under low voltage conditions.

[0016] Optionally, in some embodiments of the present application, the power supply switching unit includes:

[0017] a first triode, wherein the collector of the first triode is connected to the first end of the third resistor, the second end of the third resistor is suitable for receiving the switching signal, the emitter of the first triode is grounded, and the collector of the first triode is connected to the reference signal via a fourth resistor;

[0018] A first MOS transistor, wherein a gate of the first MOS transistor is connected to a collector of the first transistor, a source of the first MOS transistor is grounded, and a drain of the first MOS transistor is connected to a first end of a fifth resistor;

[0019] A second MOS transistor, wherein the gate of the second MOS transistor is connected to the second end of the fifth resistor, the drain of the second MOS transistor is suitable for receiving the first power supply signal, the source of the second MOS transistor is connected to the anode of the first diode, and the cathode of the first diode is connected to the headlight.

[0020] The embodiment of the present application controls the switching of two different power supply lines between the vehicle power supply and the headlights and between the boost topology unit and the headlights through the first transistor, and realizes the conduction and disconnection of the power supply line between the vehicle power supply and the headlights through the circuit coordination between the first transistor and the first MOS tube and the second MOS tube, thereby automatically stopping the direct power supply of the vehicle power supply to the headlights under low voltage conditions, thereby improving the response speed of the power supply switching unit.

[0021] Optionally, in some embodiments of the present application, the power supply switching unit further includes:

[0022] a third MOS transistor, wherein the gate of the third MOS transistor is connected to the second end of the third resistor via a current limiting resistor, the source of the third MOS transistor is grounded, and the drain of the third MOS transistor is connected to the first end of the sixth resistor;

[0023] A fourth MOS tube, wherein the gate of the fourth MOS tube is connected to the second end of the sixth resistor, the drain of the fourth MOS tube is suitable for receiving the first power supply signal, and the source of the fourth MOS tube is connected to the boost topology unit.

[0024] In the embodiment of the present application, the first transistor is used to control the switching of two different power supply lines between the vehicle power supply and the headlights and between the boost topology unit and the headlights, and the first transistor is used to coordinate with the circuits between the third MOS tube and the fourth MOS tube to realize the conduction and disconnection of the power supply line between the boost topology unit and the headlights, so that the boost topology unit can be automatically switched to the boost topology unit under low voltage conditions to boost the vehicle power supply before supplying power to the headlights, thereby improving the response speed of the power supply switching unit.

[0025] Optionally, in some embodiments of the present application, the boost topology unit includes:

[0026] a triangular wave generating sub-circuit, wherein the triangular wave generating sub-circuit is configured to generate a triangular wave signal;

[0027] a PWM generation subcircuit, the PWM generation subcircuit being configured to generate a PWM signal according to the triangular wave signal, the first power signal and the reference signal;

[0028] An energy storage inductor is configured to be charged and discharged according to the PWM signal to output a boosted second power signal, wherein a first end of the energy storage inductor is connected to the power supply switching unit.

[0029] The embodiment of the present application provides a constant frequency periodic signal for a subsequent PWM generating subcircuit through a triangular wave generating subcircuit, and realizes accurate and reliable voltage boost processing of the first power supply signal based on the pulse width modulation signal of the PWM generating subcircuit combined with the charging and discharging effect of the energy storage inductor, and effectively reduces electromagnetic interference in the voltage boost process, which is beneficial to ensure the continuous and stable operation of the LED and avoid the adverse effects of automobile voltage fluctuations on LED lighting.

[0030] Optionally, in some embodiments of the present application, the triangle wave generating subcircuit includes:

[0031] A first amplifier, wherein a negative input terminal of the first amplifier is grounded via a first capacitor, a positive input terminal of the first amplifier is connected to the reference signal via a seventh resistor, a second feedback resistor is connected between an output terminal of the first amplifier and the negative input terminal of the first amplifier, and a third feedback resistor is connected between an output terminal of the first amplifier and the positive input terminal of the first amplifier.

[0032] Optionally, in some embodiments of the present application, the PWM generation subcircuit includes:

[0033] a second amplifier, wherein a negative input terminal of the second amplifier is connected to the negative input terminal of the first amplifier, and a positive input terminal of the second amplifier is connected to the reference signal via an eighth resistor;

[0034] a second triode, wherein the base of the second triode is connected to the output end of the second amplifier via a ninth resistor, and the emitter of the second triode is grounded;

[0035] a third triode, wherein the base of the third triode is connected to the collector of the second triode, the collector of the third triode is connected to the collector of the second triode via a tenth resistor, and the collector of the third triode is connected to the cathode of the second diode, and the anode of the second diode is suitable for receiving the first power supply signal;

[0036] a fourth triode, wherein the base of the fourth triode is connected to the collector of the second triode, the collector of the fourth triode is grounded, the emitter of the fourth triode is connected to the emitter of the third triode and has a first node;

[0037] a fifth MOS transistor, wherein a gate of the fifth MOS transistor is connected to the first node via an eleventh resistor, a source of the fifth MOS transistor is grounded, and a drain of the fifth MOS transistor is connected to the second end of the energy storage inductor;

[0038] An optical coupler, wherein a first end of the optical coupler is connected to the reference signal via a twelfth resistor, a second end of the optical coupler is grounded via a voltage stabilizing diode, a third end of the optical coupler is grounded, and a fourth end of the optical coupler is connected to the positive input end of the second amplifier.

[0039] The embodiment of the present application forms a circuit for generating a PWM signal through a second amplifier, a second transistor, a third transistor, a fourth transistor and a fifth MOS tube, thereby realizing a boost processing of the first power supply signal according to the generated PWM signal, and an optical coupler is set to realize signal isolation and transmission, thereby avoiding differences in signal transmission caused by different reference grounds, thereby improving the accuracy and stability of the boost topology unit.

[0040] Optionally, in some embodiments of the present application, the headlight input unit includes a low beam input module and a high beam input module, and an anti-reverse diode is connected between the low beam input module and the high beam input module, wherein the cathode of the anti-reverse diode is connected to the low beam input module, and the anode of the anti-reverse diode is connected to the high beam input module.

[0041] Optionally, in some embodiments of the present application, the low beam input module and the high beam input module both include a constant current regulation subcircuit, and the constant current regulation subcircuit is configured to perform constant current regulation on one of the first power supply signal and the second power supply signal to provide stable power supply to the low beam and the high beam.

[0042] The embodiment of the present application ensures that the LED particles of the low beam and the high beam have a constant lighting voltage and lighting current through a constant current regulation subcircuit, so as to ensure that the low beam and the high beam have stable brightness respectively, thereby greatly improving the lighting effects of the low beam and the high beam.

[0043] In a second aspect, an embodiment of the present application provides a headlamp, comprising:

[0044] Low beam;

[0045] High beam;

[0046] And a headlamp driving circuit according to the above embodiment.

[0047] The headlamp proposed in the embodiment of the present application detects the power supply voltage of the power signal output by the vehicle power supply through the headlamp driving circuit, and switches the power supply line of the headlamp according to the detection result to provide a boosted power signal to power the headlamp. Therefore, the present application can detect the situation of insufficient power supply voltage and automatically switch to the boost topology unit for power supply, so as to ensure that the headlamp can still obtain a stable power supply voltage under low voltage conditions, thereby avoiding the situation where the headlamp is affected by unstable voltage and the brightness is reduced or flickered, ensuring the brightness and stability of the headlamp, thereby improving the driver's driving experience and ensuring driving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 A schematic diagram of the structure of a headlamp driving circuit based on constant current driving proposed in an embodiment of the present application;

[0050] Figure 2 A schematic diagram of the circuit structure of a low beam input module and a high beam input module proposed in an embodiment of the present application;

[0051] Figure 3 A schematic diagram of the circuit structure of the conversion unit proposed in the embodiment of the present application;

[0052] Figure 4 A schematic diagram of the circuit structure of a constant current detection unit proposed in an embodiment of the present application;

[0053] Figure 5 A schematic diagram of the circuit structure of the power supply switching unit proposed in an embodiment of the present application;

[0054] Figure 6a A schematic diagram of the circuit structure of a triangular wave generating sub-circuit proposed in an embodiment of the present application;

[0055] Figure 6b Schematic diagram of the circuit structure of the PWM generating sub-circuit proposed in the embodiment of the present application

[0056] Figure 7 This is a schematic diagram of the circuit structure of the constant current regulation subcircuit proposed in an embodiment of the present application. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0058] Car headlights are installed on both sides of the car head, mainly used to illuminate the road to provide the driver with road information ahead. They must not only meet regulatory requirements, but also facilitate driving. LEDs have the advantages of high brightness, low power consumption and long life, so they are increasingly used in car headlights and other automotive lighting. The working characteristics of LEDs require stable driving current and suitable operating voltage. Therefore, in order to ensure the driver's driving safety and driving experience, the design of the headlights must not only ensure brightness, but also ensure stable power supply current and voltage.

[0059] In order to prevent the insufficient supply voltage when the car is running at a low speed or the battery voltage drops, which may cause the LED brightness or flicker, in the relevant technology, the LED driver design generally directly sends the body power supply to the boost circuit to form a boost channel, where the body power supply can be the car's power battery, battery management system (BMS) and rechargeable battery, etc. However, this single boost channel causes the power supply voltage to be boosted even if it is at a normal level. For example, when the power supply voltage is lower than 13.5V, the boost channel can reach the normal voltage level to drive the LED to light up, but when the power supply voltage is higher than 13.5V, the power supply voltage still needs to pass through this boost channel, which may cause the voltage driving the LED to be too high and cause damage to the LED device, increasing the risk of LED damage, and thus affecting the vehicle driving experience and driving safety risks.

[0060] In order to stabilize the output, constant current chips are introduced in some application scenarios of related technologies to perform constant current processing on the body power supply. However, the voltage processing range of the constant current chip is limited and it cannot flexibly process different power supply voltage conditions. In addition, the peripheral circuit of the constant current chip is complex, resulting in a larger size of the driver board.

[0061] In the embodiment of the present application, a headlamp driving circuit 10 based on constant current driving is provided, such as Figure 1 As shown, the headlamp driving circuit 10 can be used in a lighting system related to headlamps such as a high beam lamp and a low beam lamp of a car, and includes a headlamp input unit 100, a constant current detection unit 200, a boost topology unit 400 and a power supply switching unit 300;

[0062] Wherein, the headlamp input unit 100 is suitable for connecting to the vehicle power supply to obtain a first power supply signal;

[0063] The constant current detection unit 200 is configured to perform voltage detection on the first power signal and generate a switching signal when the detection result is lower than the voltage limit value;

[0064] The boost topology unit 400 is configured to perform a boost process on the first power signal and output a boosted second power signal;

[0065] The power supply switching unit 300 is configured to cut off the connection between the vehicle power supply 20 and the headlight 30 according to the switching signal, and connect the boost topology unit 400 and the headlight 30 to provide a second power supply signal to light the headlight 30.

[0066] The headlamp driving circuit proposed in the embodiment of the present application detects the supply voltage of the first power supply signal output by the vehicle power supply through the constant current detection unit, and switches the power supply line of the headlamp through the power supply switching unit according to the detection result, and connects the boost topology unit with the headlamp to provide the boosted second power supply signal to power the headlamp. Therefore, the present application can detect the situation of insufficient power supply voltage and automatically switch to the boost topology unit for power supply, so as to ensure that the headlamp can still obtain a stable power supply voltage under low voltage conditions, thereby avoiding the situation that the headlamp is affected by unstable voltage and has reduced brightness or flickering, and can also switch back to the connection between the vehicle power supply and the headlamp when it is detected that the power supply voltage is not lower than the voltage limit, so as to avoid the risk of overvoltage, and can greatly improve the reliability of the headlamp while ensuring the brightness and stability of the headlamp, thereby improving the driver's driving experience and ensuring driving safety.

[0067] like Figure 2 As shown, in some embodiments of the present application, the headlight input unit 100 includes a low beam input module 110 and a high beam input module 120, and an anti-reverse diode D7 is connected between the low beam input module 110 and the high beam input module 120, wherein the cathode of the anti-reverse diode D7 is connected to the low beam input module 110, and the anode of the anti-reverse diode D7 is connected to the high beam input module 120.

[0068] The low beam input module 110 includes a low beam protection circuit composed of a transient voltage suppressor tube TVS1, a capacitor C10, a resistor R24, an anti-reverse connection MOS tube Q7, a resistor R25 and a voltage regulator diode Z1, and a filter circuit composed of capacitors C11, C12, C13, C14 and an inductor L1. The low beam input module 110 absorbs the signal interference such as surge voltage, static electricity and lightning surge from the low beam power supply LH output by the vehicle power supply through the transient voltage suppressor tube TVS1 and the resistor R24, and then performs anti-reverse connection protection through the anti-reverse connection MOS tube Q7, and finally outputs the first power supply signal VCC after filtering.

[0069] The high beam input module 120 includes a high beam protection circuit composed of a transient voltage suppressor tube TVS2, a capacitor C32, a resistor R75, an anti-reverse connection MOS tube Q20, a resistor R76, a resistor R77 and a voltage stabilizing diode Z10. Similarly, the high beam input module 120 absorbs the signal interference such as surge voltage, static electricity and lightning surge from the high beam power supply HB output by the vehicle power supply through the transient voltage suppressor tube TVS1 and the resistor R75, and then outputs the first power supply signal VCC after anti-reverse connection protection through the anti-reverse connection MOS tube Q20.

[0070] In some embodiments of the present application, the headlight drive circuit 10 also includes a conversion unit 500, which is configured to convert the power supply of the entire vehicle to obtain a reference signal, wherein the reference signal is used to supply power to the constant current detection unit 200, the boost topology unit 400 and the power supply switching unit 300 and provide a reference voltage.

[0071] In some embodiments of the present application, the reference voltage is a 5V reference voltage, and the first power signal output by the vehicle power supply is 13.2V-16V under normal power supply conditions. When the first power signal is lower than 13.2V, it is determined to be a low voltage condition.

[0072] like Figure 3 As shown, the conversion unit 500 converts the first power signal VCC at the output end of the vehicle power supply into a +5V reference signal through the DC-DC conversion chip U1. Specifically, the conversion unit 500 includes a diode D1, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4 and a 5V power chip U1, and converts the vehicle power supply into a +5V power supply through the DC-DC conversion chip U1, thereby providing a stable reference signal.

[0073] Specifically, in some embodiments of the present application, the model of the DC-DC conversion chip U1 is 78L05 / SOT89.

[0074] This embodiment converts the first power supply signal into a stable reference signal by providing a conversion unit 500. The reference signal is used to ensure that each unit in the headlamp driving circuit can continuously and stably operate under different input voltage conditions for the constant current detection unit 200, the boost topology unit 400 and the power supply switching unit 300, thereby improving the reliability of the headlamp driving circuit.

[0075] In some embodiments of the present application, Figure 4 As shown, the constant current detection unit 200 includes: a first comparator U2, wherein the negative input terminal of the first comparator U2 is connected to the first power supply signal via the resistor R41 and the resistor R33, the positive input terminal of the first comparator U2 is connected to the reference signal via the second resistor R35, the output terminal out of the first comparator U2 is suitable for outputting a switching signal, and the first feedback resistor R37 is connected between the output terminal of the first comparator U2 and the positive input terminal of the first comparator U2.

[0076] The constant current detection unit 200 performs voltage division sampling after connecting resistors R41 and R33 in series, and inputs the sampled voltage of the first power supply signal i into the negative input terminal of the first comparator U2, and obtains the reference voltage through the voltage division effect of resistor R35 and inputs it into the positive input terminal of the first comparator U2. The sampled voltages of the positive input terminal and the negative input terminal are compared by the first comparator U2. When the voltage of the first power supply signal is less than 13.2V, the output terminal of the first comparator U2 outputs a high-level switching signal to indicate that a low voltage phenomenon is detected and the first power supply signal VCC needs to be boosted before power is supplied.

[0077] The embodiment of the present application realizes voltage detection of the first power supply signal VCC by setting the first comparator U2 and obtains a comparison threshold, so that the phenomenon of insufficient power supply voltage can be quickly detected when the first power supply signal is lower than the comparison threshold, and the first comparator U2 outputs a high level to automatically trigger the subsequent boosting link and power supply switching link, which is beneficial to ensure the stability of the headlamp under low voltage conditions.

[0078] In some embodiments of the present application, Figure 5 As shown, the power supply switching unit 300 includes a first transistor Q12 , a first MOS transistor Q21 and a second MOS transistor Q22 .

[0079] The collector of the first transistor Q12 is connected to the first end of the third resistor R38, the second end of the third resistor R38 is suitable for receiving the switching signal, the emitter of the first transistor Q12 is grounded, and the collector of the first transistor Q12 is connected to the reference signal via the fourth resistor R40;

[0080] The gate of the first MOS transistor Q21 is connected to the collector of the first transistor Q12, the source of the first MOS transistor Q21 is grounded, and the drain of the first MOS transistor Q21 is connected to the first end of the fifth resistor R49;

[0081] The gate of the second MOS transistor Q22 is connected to the second end of the fifth resistor R49 , the drain of the second MOS transistor Q22 is suitable for receiving the first power signal VCC, the source of the second MOS transistor Q22 is connected to the anode of the first diode D6 , and the cathode of the first diode D6 is connected to the headlamp 30 .

[0082] In the embodiment of the present application, the first transistor Q12 is used to control the switching of two different power supply lines between the vehicle power supply 20 and the headlight 30 and between the boost topology unit 400 and the headlight 30, and the first transistor Q12 is used to coordinate with the first MOS tube Q21 and the second MOS tube Q22 to realize the conduction and disconnection of the power supply line between the vehicle power supply 20 and the headlight 30, so that the direct power supply of the vehicle power supply 20 to the headlight 30 can be automatically stopped under low voltage conditions, thereby improving the response speed of the power supply switching unit 300.

[0083] Further, in some embodiments of the present application, Figure 5 As shown, the power supply switching unit 300 also includes:

[0084] A third MOS transistor Q23, wherein the gate of the third MOS transistor Q23 is connected to the second end of the third resistor R38 via the current limiting resistor R44, the source of the third MOS transistor Q23 is grounded, and the drain of the third MOS transistor Q23 is connected to the first end of the sixth resistor R51;

[0085] A fourth MOS transistor Q24 , a gate of the fourth MOS transistor Q24 is connected to the second end of the sixth resistor R51 , a drain of the fourth MOS transistor Q24 is suitable for receiving the first power signal VCC, and a source of the fourth MOS transistor Q24 is connected to the boost topology unit 400 .

[0086] In the embodiment of the present application, the first transistor Q12 is used to control the switching of two different power supply lines between the vehicle power supply 20 and the headlight 30 and between the boost topology unit 400 and the headlight 30, and the first transistor Q12 is used to coordinate with the third MOS tube Q23 and the fourth MOS tube Q24 to realize the conduction and disconnection of the power supply line between the boost topology unit 400 and the headlight 30, so that the boost topology unit 400 can automatically switch to the boost topology unit 400 under low voltage conditions to boost the vehicle power supply 20 before supplying power to the headlight 30, thereby improving the response speed of the power supply switching unit 400.

[0087] Specifically, the high-level switching signal output by the first comparator U2 is input to the gate of the third MOS tube Q23, so that the source and collector of the third MOS tube Q23 are pulled down to the ground, and finally the gate of the fourth MOS tube Q24 is at a low level, so that the fourth MOS tube Q24 is turned on, and at the same time, the base of the first triode Q12 is turned on and connected to the ground after receiving the high level output by the first comparator U2, so that the gate of the first MOS tube Q21 is at a low level. At this time, the first MOS tube Q21 is turned off, resulting in the second MOS tube Q22 not being turned on, disconnecting the original vehicle power supply circuit and switching to the boost topology unit 400, thereby realizing the switching of the power supply line.

[0088] When the vehicle power supply is higher than 13.2V, the voltage at the negative input terminal of the first comparator U2 is greater than the voltage at the positive input terminal, and the first comparator U2 outputs a low-level switching signal. The low-level signal is input to the gate of the third MOS transistor Q23 in the power supply switching unit 300, so that the third MOS transistor Q23 is turned off, and finally the gate of the fourth MOS transistor Q24 is at a high level, so that the fourth MOS transistor Q24 is turned off. The base of the first triode Q12 is closed after receiving the low level output by the first comparator U2, so that the gate of the first MOS transistor Q21 is at a high level and turned on, causing the gate of the second MOS transistor Q22 to be at a low level, thereby turning on and switching to the original vehicle power supply circuit, and the vehicle power supply 20 directly supplies power to the headlight 30.

[0089] In some embodiments of the present application, Figure 6a and Figure 6b As shown, the boost topology unit 400 includes a triangle wave generating sub-circuit 410, a PWM generating sub-circuit 420 and an energy storage inductor L2;

[0090] Wherein, the triangle wave generating subcircuit 410 is configured to generate a triangle wave signal;

[0091] The PWM generation sub-circuit 420 is configured to generate a PWM signal according to the triangle wave signal, the first power signal VCC and the reference signal;

[0092] The energy storage inductor L2 is configured to charge and discharge according to the PWM signal to output a boosted second power signal, wherein a first end of the energy storage inductor L2 is connected to the power supply switching unit 300, and a second end of the energy storage inductor L2 outputs the boosted second power signal.

[0093] The embodiment of the present application provides a constant frequency periodic signal for a subsequent PWM generating subcircuit through a triangular wave generating subcircuit, and realizes accurate and reliable voltage boost processing of the first power supply signal based on the pulse width modulation signal of the PWM generating subcircuit combined with the charging and discharging effect of the energy storage inductor, and effectively reduces electromagnetic interference in the voltage boost process, which is beneficial to ensure the continuous and stable operation of the LED and avoid the adverse effects of automobile voltage fluctuations on LED lighting.

[0094] Further, in some embodiments of the present application, Figure 6a As shown, the triangle wave generating sub-circuit 410 includes a first amplifier U5, wherein the negative input terminal of the first amplifier U5 is grounded via a first capacitor C33, the positive input terminal of the first amplifier U5 is connected to the reference signal via a seventh resistor R82, a second feedback resistor R78 is connected between the output terminal of the first amplifier U5 and the negative input terminal of the first amplifier U5, and a third feedback resistor R81 is connected between the output terminal of the first amplifier U5 and the positive input terminal of the first amplifier U5.

[0095] like Figure 6b As shown, the PWM generation sub-circuit 420 includes: a second amplifier U6, a second transistor Q11, a third transistor Q9, a fourth transistor Q10, a fifth MOS transistor Q8 and an optical coupler U3;

[0096] The negative input terminal of the second amplifier U6 is connected to the negative input terminal of the first amplifier U5, and the positive input terminal of the second amplifier U6 is connected to the reference signal via the eighth resistor R84;

[0097] The base of the second transistor Q11 is connected to the output end of the second amplifier U6 via the ninth resistor R30, and the emitter of the second transistor Q11 is grounded;

[0098] The base of the third triode Q9 is connected to the collector of the second triode Q11, the collector of the third triode Q9 is connected to the collector of the second triode Q11 via the tenth resistor R29, and the collector of the third triode Q9 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is suitable for receiving the first power signal VCC;

[0099] The base of the fourth triode Q10 is connected to the collector of the second triode Q11, the collector of the fourth triode Q10 is grounded, the emitter of the fourth triode Q10 is connected to the emitter of the third triode Q9 and has a first node;

[0100] The gate of the fifth MOS transistor Q8 is connected to the first node via the eleventh resistor R28, the source of the fifth MOS transistor Q8 is grounded, and the drain of the fifth MOS transistor Q8 is connected to the second end of the energy storage inductor L2;

[0101] The first end of the optical coupler U3 is connected to the reference signal via the twelfth resistor R85, the second end of the optical coupler U3 is grounded via the voltage stabilizing diode U4, the third end of the optical coupler U3 is grounded, and the fourth end of the optical coupler U3 is connected to the positive input end of the second amplifier U6.

[0102] Specifically, the first amplifier U5 and its peripheral circuits in the boost topology unit 400 are a triangular wave generating subcircuit 410, and the triangular wave provides a periodic signal with a constant frequency for the subsequent PWM generating subcircuit 420, thereby ensuring the stable voltage regulation of the boost topology unit 400. The error amplifier U6 and its peripheral circuits are PWM wave generating circuits, and the negative input terminal of the second amplifier U6 is connected to the triangular wave, and the positive input terminal is connected to the reference signal, and the two are compared, so as to dynamically and stably adjust the output voltage to ensure that the output voltage is stable at 15V. The output voltage feedback terminal of the boost topology unit 400 uses an optical coupler U3 as a signal isolation and transmission to avoid differences in signal transmission due to different reference grounds, and the output voltage detection circuit of the boost topology unit 400 uses a three-terminal regulator U4 for voltage sampling.

[0103] The embodiment of the present application forms a circuit for generating a PWM signal through a second amplifier, a second transistor, a third transistor, a fourth transistor and a fifth MOS tube, thereby realizing a boost processing of the first power supply signal according to the generated PWM signal, and an optical coupler is set to realize signal isolation and transmission, thereby avoiding differences in signal transmission caused by different reference grounds, thereby improving the accuracy and stability of the boost topology unit.

[0104] In some embodiments of the present application, Figure 7 As shown, the low beam input module 110 and the high beam input module 120 both include a constant current regulation subcircuit 130, which is configured to perform constant current regulation on one of the first power supply signal VCC and the second power supply signal to provide stable power supply to the low beam and the high beam.

[0105] In order to ensure that the voltage and current of the headlamp 30 are not affected by changes in the power supply voltage, in the embodiment of the present application, a constant current regulation subcircuit 130 is used to form a closed-loop negative feedback, wherein the base of the transistor Q6 is connected to the emitters of the transistors Q1 to Q5 in the constant current regulation subcircuit 130, that is, one end of the negative feedback resistors R11 to R20, and the emitter of the transistor Q6 is connected to the bases of the transistors Q1 to Q5. When the emitter current of the transistors Q1-Q5 increases, the current of the base of the transistor Q6 increases, that is, the voltage across the transistor Q6 decreases, which will cause the current of the base of the transistors Q1-Q5 to decrease, and ultimately cause the current of the headlamp 30 to decrease, thereby achieving a dynamic regulation process.

[0106] The embodiment of the present application ensures that the LED particles of the low beam and the high beam have a constant lighting voltage and lighting current through a constant current regulation subcircuit, so as to ensure that the low beam and the high beam have stable brightness respectively, thereby greatly improving the lighting effects of the low beam and the high beam.

[0107] Correspondingly, an embodiment of the present application further provides a headlamp, comprising a low beam, a high beam, and a headlamp driving circuit 10 according to the above embodiment.

[0108] The specific configuration of each of the above modules and units and further functional description are the same as those of the above corresponding embodiments and will not be repeated here.

[0109] The headlamp proposed in this embodiment detects the power supply voltage of the power signal output by the vehicle power supply through the headlamp driving circuit, and switches the power supply line of the headlamp according to the detection result to provide a boosted power signal to power the headlamp. Therefore, the present application can detect the situation of insufficient power supply voltage and automatically switch to the boost topology unit for power supply, so as to ensure that the headlamp can still obtain a stable power supply voltage under low voltage conditions, thereby avoiding the situation where the headlamp is affected by unstable voltage and the brightness is reduced or flickered, ensuring the brightness and stability of the headlamp, thereby improving the driver's driving experience and ensuring driving safety.

[0110] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0111] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0112] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0113] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0114] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A headlamp driving circuit based on constant current driving, characterized in that: The headlamp driving circuit comprises: A headlight input unit, wherein the headlight input unit is adapted to be connected to a vehicle power supply to obtain a first power supply signal; a constant current detection unit, the constant current detection unit being configured to perform voltage detection on the first power supply signal and generate a switching signal when the detection result is lower than a voltage limit; A boost topology unit, wherein the boost topology unit is configured to perform a boost process on the first power signal and output a boosted second power signal; A power supply switching unit is configured to cut off the connection between the vehicle power supply and the headlight according to the switching signal, and connect the boost topology unit and the headlight to provide the second power supply signal to light the headlight.

2. The headlamp driving circuit according to claim 1, characterized in that: The headlamp driving circuit also includes a conversion unit, which is configured to convert the vehicle power supply to obtain a reference signal, wherein the reference signal is used to supply power to the constant current detection unit, the boost topology unit and the power supply switching unit and provide a reference voltage.

3. The headlamp driving circuit according to claim 2, characterized in that: The constant current detection unit includes: a first comparator, wherein the negative input terminal of the first comparator is connected to the first power supply signal via a first resistor, the positive input terminal of the first comparator is connected to the reference signal via a second resistor, the output terminal of the first comparator is suitable for outputting the switching signal, and a first feedback resistor is connected between the output terminal of the first comparator and the positive input terminal of the first comparator.

4. The headlamp driving circuit according to claim 2, characterized in that: The power supply switching unit comprises: a first triode, wherein the collector of the first triode is connected to the first end of the third resistor, the second end of the third resistor is suitable for receiving the switching signal, the emitter of the first triode is grounded, and the collector of the first triode is connected to the reference signal via a fourth resistor; A first MOS transistor, wherein a gate of the first MOS transistor is connected to a collector of the first transistor, a source of the first MOS transistor is grounded, and a drain of the first MOS transistor is connected to a first end of a fifth resistor; A second MOS transistor, wherein the gate of the second MOS transistor is connected to the second end of the fifth resistor, the drain of the second MOS transistor is suitable for receiving the first power supply signal, the source of the second MOS transistor is connected to the anode of the first diode, and the cathode of the first diode is connected to the headlight.

5. The headlamp driving circuit according to claim 4, characterized in that: The power supply switching unit also includes: a third MOS transistor, wherein the gate of the third MOS transistor is connected to the second end of the third resistor via a current limiting resistor, the source of the third MOS transistor is grounded, and the drain of the third MOS transistor is connected to the first end of the sixth resistor; A fourth MOS tube, wherein the gate of the fourth MOS tube is connected to the second end of the sixth resistor, the drain of the fourth MOS tube is suitable for receiving the first power supply signal, and the source of the fourth MOS tube is connected to the boost topology unit.

6. The headlamp driving circuit according to claim 2, characterized in that: The boost topology unit comprises: a triangular wave generating sub-circuit, wherein the triangular wave generating sub-circuit is configured to generate a triangular wave signal; a PWM generation subcircuit, the PWM generation subcircuit being configured to generate a PWM signal according to the triangular wave signal, the first power signal and the reference signal; An energy storage inductor is configured to be charged and discharged according to the PWM signal to output a boosted second power signal, wherein a first end of the energy storage inductor is connected to the power supply switching unit.

7. The headlamp driving circuit according to claim 6, characterized in that: The triangular wave generating sub-circuit comprises: A first amplifier, wherein a negative input terminal of the first amplifier is grounded via a first capacitor, a positive input terminal of the first amplifier is connected to the reference signal via a seventh resistor, a second feedback resistor is connected between an output terminal of the first amplifier and the negative input terminal of the first amplifier, and a third feedback resistor is connected between an output terminal of the first amplifier and the positive input terminal of the first amplifier.

8. The headlamp driving circuit according to claim 7, characterized in that: The PWM generation sub-circuit comprises: a second amplifier, wherein a negative input terminal of the second amplifier is connected to the negative input terminal of the first amplifier, and a positive input terminal of the second amplifier is connected to the reference signal via an eighth resistor; a second triode, wherein the base of the second triode is connected to the output end of the second amplifier via a ninth resistor, and the emitter of the second triode is grounded; a third triode, wherein the base of the third triode is connected to the collector of the second triode, the collector of the third triode is connected to the collector of the second triode via a tenth resistor, and the collector of the third triode is connected to the cathode of the second diode, and the anode of the second diode is suitable for receiving the first power supply signal; a fourth triode, wherein the base of the fourth triode is connected to the collector of the second triode, the collector of the fourth triode is grounded, the emitter of the fourth triode is connected to the emitter of the third triode and has a first node; a fifth MOS transistor, wherein a gate of the fifth MOS transistor is connected to the first node via an eleventh resistor, a source of the fifth MOS transistor is grounded, and a drain of the fifth MOS transistor is connected to the second end of the energy storage inductor; An optical coupler, wherein a first end of the optical coupler is connected to the reference signal via a twelfth resistor, a second end of the optical coupler is grounded via a voltage stabilizing diode, a third end of the optical coupler is grounded, and a fourth end of the optical coupler is connected to the positive input end of the second amplifier.

9. The headlamp driving circuit according to claim 1, characterized in that: The headlight input unit includes a low beam input module and a high beam input module, and an anti-reverse diode is connected between the low beam input module and the high beam input module, wherein the cathode of the anti-reverse diode is connected to the low beam input module, and the anode of the anti-reverse diode is connected to the high beam input module.

10. The headlamp driving circuit according to claim 9, characterized in that: The low beam input module and the high beam input module both include a constant current regulation subcircuit, which is configured to perform constant current regulation on one of the first power supply signal and the second power supply signal to provide stable power supply to the low beam and the high beam.

11. A headlamp, characterized in that: The headlamp comprises: Low beam; High beam; And a headlamp driving circuit according to any one of claims 1 to 10 above.

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