WO2021186467A1

WO2021186467A1 - Integrated driver circuit for illumination system of a vehicle

Info

Publication number: WO2021186467A1
Application number: PCT/IN2021/050252
Authority: WO
Inventors: Chinnala DIVYA SRI
Original assignee: Tvs Motor Company Limited
Priority date: 2020-03-16
Filing date: 2021-03-12
Publication date: 2021-09-23
Also published as: CO2022013265A2

Abstract

The present subject matter relates generally to an integrated driver circuit (101) for an illumination system of a vehicle (100). The integrated driver circuit (101) integrates a transient over voltage protection circuit, a filtering circuit and a reverse polarity protection circuit with a single control unit (106) in order to monitor the current being sent to plurality of LED lamps (LED1, LED2, LED3) provided in the vehicle and to control the illumination of plurality of the LED lamps (LED1, LED2, LED3) through plurality of MOSFET switches (M1, M4, M2) by controlling the gate voltage of the MOSFET switches (M1, M4, M2). The integration is enabled by using a single driver circuit instead of multiple drivers for each lamp in the vehicle. Integrated driver integrates the actuation of each of the lamp independently.

Description

INTEGRATED DRIVER CIRCUIT FOR ILLUMINATION SYSTEM OF A

VEHICLE TECHNICAL FIELD

[0001] The present subject matter relates generally to a vehicle. The present subject matter specifically but not exclusively relates to an integrated driver circuit for illumination system of a vehicle. BACKGROUND

[0002] Currently, LED (Light Emitting Diodes) based lighting has become the efficient light source of choice, replacing both incandescent and fluorescents. The issues of present lighting technology such as efficiency of lighting, shape, color quality, the presence of toxic mercury and limited lifetime are all better addressed by LEDs.

[0003] LEDs are being used in static as well as dynamic powered devices & products e.g. automotive applications in parts, such as head lamp, tail lamp, turn signal lamp, number plate lamp and position lamp. Each LED lamp in the vehicle requires a driver circuit, which regulates the power to an LED or a string (or strings) of LEDs and to protect LEDs from voltage or current fluctuations. Apart from driver circuit, LED lamps are also provided with reverse polarity protection, transient overvoltage protection and filtering components for Electromagnetic interference (EMI). The presence of several LED lamps in a vehicle would result in multiple driver circuit with separate protection and filtering components for each LED lamp, which would lead to increase in the number of electric circuit components in a vehicle. As a result the overall circuit and wiring in the vehicle would become more complex leading to space constraint, increasing manufacturing and assembly time and also increasing the material cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The detailed description is described with reference to an embodiment of a saddle type vehicle along with the accompanying figures. The same numbers are used throughout the drawings to reference like features and components. [0005] Fig. 1 illustrates an exemplary side view of a vehicle used to enable the present subject matter.

[0006] Fig. 2(a) illustrates block diagram of the present subject matter depicting the interaction of each component in the integrated driver circuit.

[0007] Fig. 2(b) illustrates a block diagram of the integrated driver circuit with LED lamps in a vehicle.

[0008] Fig. 3 illustrates a circuit level diagram of the present subject matter depicting the integrated driver circuit.

[0009] Fig. 4 illustrates a circuit configuration for setting operating mode of the position lamp. [00010] Fig.5 illustrates a circuit configuration for a setting current for tail and stop lamp.

[00011] Fig. 7 illustrates a flow chart to depict the working of the integrated circuit.

DETAILED DESCRIPTION [00012] Most of the lamps used in the vehicle comprises more than one LED to provide necessary illumination. LED lamp requires driver circuit which delivers power to string of LEDs in a controlled way. The driver circuit prevents the LEDs from failure by controlling thermal runaway due to decrease in forward voltage thereby leading to increase in the current. Therefore, each lamp employing strings of LEDs requires a driver circuit. If the number of LEDs based lamps increases in the vehicle the number of driver circuit also increases. Similarly, circuits like transient overvoltage protection circuit to protect the LED lamps from transient surge, filtering circuits for electromagnetic interference also increases for each lamp leading to increase in electrical components contributing to increase in production cost and also more space requirement in the vehicle.

[00013] There are LED drivers for providing power to parallelly connected LED sources and LED driver which is a constant current source which connects to any one of the output at a time. The LED driver includes a processor which causes the switch to sequentially connect to each of the LED sources (output) in order to power the sources for a pre-determined period of time. But the problem associated with this is high frequency switching which leads to Electromagnetic inference (EMI) related issues and thereby leading to performance issues due to rapid rise and fall of the current in the LEDs. To overcome the problem of high frequency fluctuation there are drivers which comprises a digital programmable controller programmed to adjust the ripple free DC current. But this system involves multiple components making it a complex circuit which includes employing of a transformer making it less reliable and may cause leakage current in the transformer coil eventually leading to power loss. The present subject matter integrates the control over plurality of independent lamps provided in the vehicle by incorporating a single drive circuit rather than using multiple drive circuit for each of the headlamps or merely combining all the drive circuits in a single package. The integrated driver provided by the present subject matter can control each of the lamps independently.

[00014] Hence, it is the object of the present subject matter to provide an integrated driver circuit for plurality of LED lamps used in the vehicle which incorporates a reverse polarity protection circuit, transient overvoltage protection circuit and a filtering circuit without compromising on electromagnetic interference and issues aforementioned in above paragraphs such as more number of components, power loss and high frequency fluctuation. The integrated driver circuit monitors the current sent to plurality of LED lamps in the vehicle without requiring multiple circuits and components thereby reducing the cost, material and the problems as mentioned above. The present subject matter utilizes a single driver circuit to control plurality of lamps provided in the vehicle thereby integrating the control over multiple lamps in the vehicle and eliminates the requirement of separate driver for each of the lamps provided in the vehicle.

[00015] Another embodiment of the present subject matter provides an integrated driver circuit which comprises of plurality of setting resistors which set the PWM (Pulse width modulation) duty cycle and frequency for each LED lamp provided in the vehicle. Thereby, the present subject matter also eliminates the problems faced in the circuits where plurality of lamps are provided in the vehicle connected in series and the present subject matter prevents complete black out due to any one of the lamp, which may become dysfunctional. [00016] Yet another embodiment of the present subject matter is configured to provide plurality of current sensing resistors which sets and monitors a PWM (Pulse width modulation) duty cycle for each lamp thereby enabling each lamp to be configured independently without interfering the function of the other lamps in the vehicle. [00017] Another embodiment of the present subject matter is configured to provide a driver circuit which monitors the current through the current sense unitss. The driver circuit controls the gates of MOSFET switches which are electrically connected to the LED lamps.

[00018] Fig. 1 illustrates a left side view of an exemplary motor vehicle (100), in accordance with an embodiment of the present subject matter. The vehicle (100) illustrated, has a schematically represented frame member (105). In the present embodiment, the frame member (105) is step-through type including a head tube (105 A), and a main frame (105B) that extend rearwardly downward from an anterior portion of the head tube (105A). The main frame (105B) extends inclinedly rearward to a rear portion of the vehicle (100).

[00019] The vehicle (100) includes one or more prime movers that are connected to the frame member (105). In the present implementation, one of the prime movers is an internal combustion (IC) engine (115) mounted to the frame member (105). In the depicted embodiment, the IC engine (115) is mounted to a structural member (135) that is pivoted to the frame member (105). In one embodiment, the structural member (135) is a rigid member made including metal. The vehicle (100) also includes another prime mover, which is an electric motor (120). In a preferred embodiment, the electric motor (120) is hub mounted to one wheel of the vehicle (100). In another embodiment, one or more than one electric motor is mounted to wheels or to the frame of the vehicle. In the depicted embodiment, the vehicle (100) includes at least two-wheels and the electric motor (120) is hub mounted to the rear wheel (125) of the vehicle. A front wheel (110) is rotatably supported by the frame member (105) and is connected to a handle bar assembly (130) that enables maneuvering of the vehicle (100).

[00020] Further, the vehicle (100) includes a high capacity on-board battery (not shown) that drives the electric motor (120). The high capacity battery may include one or more high capacity battery packs or one or more low capacity cells. The high capacity battery can be disposed at a front portion, a rear portion, or at the center of the vehicle (100). The high capacity battery is supported by the frame member (105) and the vehicle (100) includes plurality of body panels, mounted to the frame member (105) for covering various components of the vehicle (100). The plurality of panels includes a front panel (140A), a leg shield (140B), an under-seat cover (140C), and a left and a right-side panel (140D). A glove box may be mounted to a leg shield (140B).

[00021] A floorboard (145) is provided at the step-through portion defined by the main tube (105B). A seat assembly (150) is disposed rearward to the step-through portion and is mounted to the main frame (105B). The seat assembly (150) that is elongated in a longitudinal direction F-R of the vehicle (100) enables the user to operate the vehicle in a saddle ride-type posture. One or more suspension(s) connect the wheels (110), (125) to the vehicle (100) and provide a comfortable ride. The vehicle (100) comprises of plurality of electrical and electronic components including a headlight (155A), a taillight (155B), a starter motor (not shown), a hom etc. Also, the vehicle (100) includes a master control unit (not shown) that takes control of the overall operation of the vehicle (100) including the function of the IC engine (115), the electric motor (120), charging of the batteries from a magneto/integrated starter generator (ISG), driving of loads by the magneto/ISG, charging of the high capacity batteries by the electric motor operating in generator mode, and any other operations associated with the operation of the vehicle (100). The vehicle (100) shown in fig. 1 is an exemplary vehicle and the present subject matter can be used in a two-wheeled vehicle, three-wheeled vehicle or a four- wheeled vehicle.

[00022] Fig. 2(a) illustrates block diagram of the present subject matter depicting the interaction of each component where a control unit (106) powered by a power source (102,103) like a battery (103) or a magneto (102). The control unit (106) monitors and controls the input current sent to a plurality of illuminating units such as LED lamps (LED1, LED2, LED3) provided in a vehicle - headlamp, tail lamp etc. Further, a plurality of current sense unit (208) such as resistors (R9, R10, R11) are used to set the current to drive each of the plurality of illuminating units. The control unit (106) is electrically connected to one or more switching units (Ml, M2, M3), through gates of MOSFETS, which are connected to each of the plurality of illuminating units, such that the control unit (106) is configured to control the voltages of the switching units (Ml, M2, M3) when the input current is greater than the set currents set by the plurality of current sense units (208) for each of said plurality of illuminating units. The switching units (Ml, M2, M3) controls the input currents driving the illuminating units based the voltage at the switching units (Ml, M2, M3).

[00023]

[00024] Fig. 2(b) illustrates a block diagram of the integrated driver circuit with LED lamps (LED1, LED2, LED3) in the vehicle (100). The circuit is constructed in order to control multiple LED lamps in vehicle such as a head lamp, a tail lamp, a stop lamp and a position lamp independently in parallel configuration. At the input end the integrated driver circuit (101) is fed with one or more power input from the battery (103) or a magneto (102). The magneto (102) provides AC (alternating current) whereas the battery (103) provides direct current (103). One of the terminals of the magneto (102) and the battery (103) are electrically connected to a zero voltage by connecting to a ground (113). The input coming from the magneto (102) is an AC current so it first goes through rectification process and also regulation process to control the output voltage level in order to be fed to the integrated driver circuit (101). The RR unit (regulator rectifier unit) (104) regulates the incoming voltage from the magneto (102) and also the AC current gets converted into a DC current through rectification. An input switch (165) has been provided to switch ON or switch OFF the functioning of the integrated driver circuit (101).

[00025] The output from the integrated driver circuit (101) goes to one or more light sources comprising LED strings. The output goes to a DRL (day time running lamp)/Position lamps (107), a head lamp (108), a tail lamp (130) and a stop lamp (111). The DRL/position lamp (107) has been provided without a switch for the driver to control as the DRL/position lamp (107) remains ON irrespective of the user’s choice or ambient light condition. The negative terminal of the LED string of each lamp is connected to ground (113). Headlamp (108) and stop lamp (111) has been provided with a head lamp switch (109) and a stop switch (112) respectively.

[00026] Fig. 3 illustrates a circuit level diagram of the present subject matter depicting the integrated driver circuit (101). A reverse polarity protection circuit (201) is connected to the input power terminal (V bat). The reverse polarity protection circuit (101) comprises a reverse protection diode (202) to protect from reverse voltage, a transient voltage protection diode (211) (Zener Diode) to protect the circuit from transient voltage and a reverse protection capacitor (203) for filtering of input power received from input power terminal (V bat). The reverse polarity protection circuit (201) also protects the driver circuit (106). The control unit (106) is a linear programmable IC through high side resistors and regulates the driving function of the LED lamps (LED1, LED2, LED3). The control unit (106) controls the overvoltage received from the input power terminal (Vbat) whereas reverse protection diode (202) protects the circuit from reverse voltage. The control unit (106) with a linear integrated circuit (IC) is configured in the present subject matter because of low electromagnetic interference issues.

[00027] The control unit (106) is being powered by a driver input (Vin). The driver input (Vin) sends power to a voltage divider circuit (205) comprising one or more resistors in series configuration. The control unit (106) gets enabled or disabled by the voltage divider circuit (205).

[00028] The load current to the LED (LED1, LED2, LED3) lamps is being supplied from energy sources like a battery and a magneto provided in a vehicle which is being first filtered, rectified and then regulated by the regulator rectifier unit (104). The power from driver input (Vin) goes to a voltage divider circuit (205) and the voltage gets reduced at the stage in order to make the power suitable to operate the control unit (106). The input power from the driver input (Vin) may consist of some noises which is necessary to be filtered out before sending to the control unit (106). Therefore, a driver filter circuit (204) comprising one or more capacitors are being connected in parallel configuration.

[00029] The input power is fed to plurality of LED lamps (LED1, LED2, LED3) from a power source like a battery. Each of the LED lamps (LED1, LED2, LED3) is electrically connected to at least one current sense units (208) which are resistors R9, R10 and Rl l. The input power is fed to each of the current sense unitss (R9, R10, Rll) and the control unit (106) monitors the current sent to the LED lamps (LED1, LED2, LED3). The LED driver (106) is connected to a plurality of monitor units (206) which are resistors R4, R5 and R6 for each channel to set the PWM (Pulse width modulation) duty cycle and frequency of current value to monitor the load current (from Vbat) sent to each of the LED lamps (LED1, LED2, LED3) provided in the vehicle. The required output current to be fed to the LED lamps (LED1, LED2, LED3) is being programmed through high side resistors or the current sense setting resistors (R9, R10, Rl l). If the value of current through LED string goes beyond the setting current set by the current sense unitss (R9, R10, Rl l) then the gate voltage of the MOSFET switches (Ml, M4, M2) are controlled, thereby controlling and monitoring of current being sent to the LED lamps done by the control unit (106) though gates of the MOSFET switches (Ml, M4, M2). An internal precision constant current regulation loop senses the channel current by the voltage across the sense resistors (R9, R10, Rll) and the gate voltage of plurality of MOSFET switches (Ml, M4, M2) are being controlled accordingly. Depending on the voltage across the sense resistors (R9, R10, Rll), gates of the plurality of MOSFET switches (Ml, M4, M2) are being controlled by the control unit (106) with the help of monitor units (206).

[00030] A charge pump (207) comprising capacitors Cl, C2, C3 which is connected to the control unit (106) to provide gate drive voltage to the MOSFET switches (Ml, M4, M2). Additional resistors for setting one fail all fail setting resistor (210) to detect any fault in the control unit (106) and an internal current reference resistor (209) has been provided for proper functioning of the control unit (106).

[00031] An enhancement type N-channel MOSFET is being used for the purpose of MOSFET switches (Ml, M4, M2). The drain terminals of the MOSFET switches (Ml, M4, M2) are electrically connected to the reverse polarity protection circuit (201) from which the input power is being is received and also connects the current sense unitss (208) whereas the source terminals of each MOSFET switches (Ml, M4, M2) are being connected to one or more LED lamps (LED1, LED2, LED3) present in the vehicle. The source of the MOSFET switches (Ml, M4, M2) are also connected to one or more bypass capacitors (C5, C6, C7) electrically connected to zero potential and operates as an open circuit.

[00032] The control unit (106) constitutes three channel high side current driving and sensing circuitry. Out of the three channels the first one is used to drive the position lamp which can be driven in two modes that is day time running (DRL) mode and position lamp mode. The current is set by the sense resistor (208) whose value switches between two levels based on the operating mode. Fig. 4 illustrates a circuit configuration of operating mode of the position lamp (305). The operating mode of the position lamp (305) is determined by a headlamp switch state (302). When the headlamp switch (302) is in OFF state, the lamp operates in DRL (Day time running lamp) mode. When the headlamp switch (302) changes to ON state, the position lamp (305) operates in position lamp mode. The MOSFET switch (304) regulates the amount of current flowing to the position lamp (305). Head lamp resistors (301,303) are connected in the circuit.

[00033] Fig.5 illustrates a circuit configuration for a setting current for tail and stop lamp (405). The control unit (106) configuration and channel current setting configuration can be modified based on LED connection topologies used in headlamp, tail lamp and position lamp. Protection circuit components for reverse polarity, over voltage (transient voltage) and filtering components for electromagnetic interference are placed at an input terminals of control unit (106).

[00034] The control unit (106) is also configured to provide diagnostics and fault protection for various faults like any of the LED lamps (LED1, LED2, LED3) shorting to ground, LED lamp open circuit and over temperature. The MOSFET switches (Ml, M4, M2) and LED lamps (LED1, LED2, LED3) are protected from overvoltage by setting the derating factor using a voltage divider circuit (205). When the input voltage is in the range of 18V to 24 V, the output current in all channels derate by 50%.

[00035] Fig. 6 illustrates a flow chart to depict the working of the integrated circuit. In step 601, the control unit (106), which is electrically connected to a driver input (Vin) gets enabled when an ignition switch of the vehicle gets ON and the current sense unitss (208) connected to head lamps (LED1, LED2, LED3) draws power. After the control unit (106) gets enabled, the setting resistors (R4, R5, R6, R7) enables setting of PWM (Pulse width modulation) duty cycle in step 602. Then in step 603, the current received at the current sense unitss (R9, R10, Rll) is being compared with the current set by the control unit (106). After comparing, in step 604, it is being checked whether the average current is less than or more than the current set by the current sense unitss (R9, R10, R11). Then, if the average current is less than the current set by the current sense units then, in step 605, the MOSFET switches’ (Ml, M4, M2) gate voltage will be controlled in such a way to increase the average current by increasing the duty cycle. Otherwise, if the average current is more than the current set by the current setting resistors (R9, RIO, Rl l) (step 606), then in step 607, the MOSFET switches’ (Ml, M4, M2) gate voltage is again controlled in order to decrease the average current to make it equal to the current set by the current sense unitss (R9, RIO, R11). If the average current is same as that of the setting current set by the current sense unitss (R9, RIO, Rl l), then there would be no action (step 608) by the control unit (106) and the current flowing to the channels connecting different loads that is LED lamps (LED1, LED2, LED3) remains the same. [00036] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

Claims

We Claim:

1. An integrated driver circuit (101), said integrated driver circuit (101) comprising: a control unit (106) powered by a power source (102,103) to control an input current sent to a plurality of illuminating units; a plurality of monitor units (206) controls a duty cycle and a frequency to monitor a load current of said plurality of illuminating units; a plurality of current sense units (208) to configure a set current to drive said plurality of illuminating units; one or more switching units (Ml, M2, M3) electrically connected to said plurality of illuminating units, said control unit (106) configured to control at least a voltage of the said one or more switching units (Ml, M2, M3) when said input current is greater than said set current of each of said plurality of current controlling units (208), and said one or more switching units (Ml, M2, M3) controls said input currents driving said illuminating units based on at least a said voltage.

2. The integrated driver circuit (101) as claimed in claim 1, wherein said plurality of plurality of monitor units (206) electrically configured to a reverse polarity protection circuit (201) and said control unit (106).

3. The integrated driver circuit (101) as claimed in claim 1, wherein said illuminating units are LED lamps (LED1, LED2, LED3).

4. The integrated driver circuit (101) as claimed in claim 1, wherein said said one or more current sense units (208) are connected to one or more drain terminals of one or more MOSFET switches (Ml, M4, M2);

5. The integrated driver circuit (101) as claimed in claim 1, wherein a charge pump (207) comprising plurality of capacitors (Cl, C2, C3) connected to said control unit (106) to provide gate-drive voltage to said one or more switching units (Ml, M2, M3).

6. The integrated driver circuit (101) as claimed in claim 1 or claim 3, wherein said plurality of LED lamps (LED1, LED2, LED3) are head lamp (108), tail lamp (130), stop lamp (111), a day time running lamp or a position lamp (107) in a vehicle (100).

7. The integrated driver circuit (101) as claimed in claiml, wherein said one or more drain terminals of said one or more switching units (Ml, M2, M3) are electrically connected to said one or more current sense units (208).

8. The integrated driver circuit (101) as claimed in claiml, wherein one or more source terminals of said one or more switching units (Ml, M2, M3) are electrically connected to at least a said plurality of illuminating units provided in a vehicle (100).

9. The integrated driver circuit (101) for plurality of LED lamps (LED1, LED2, LED3) as claimed in claim 1, wherein said plurality of illuminating units are arranged in parallel configuration.

10. A method of controlling illumination of a plurality of illuminating units disposed in a vehicle (100) comprising the steps of: receiving load input current from input power terminal (Vbat) after enabling driver circuit; setting a PWM (Pulse width modulation) duty cycle by a plurality of monitor units (206); comparing a current received at one or more current sense units (208) by a control unit (106); and controlling an average current by controlling one or more gate voltage of switching units (Ml, M2, M3) connected to drive said plurality of illuminating units.