Claims:We claim:
1. A sequential LED device (200)comprising :
one or more loads (202,202b) configured in parallel to receive an input power from an input terminal (206) connected to a power source;
a driver unit(201) configured to set a frequency of said one or more loads (202,202b) through a frequency setting unit (203);
a detecting terminal (207) to detect an open load condition in at least one of said one or more loads (202,202b); and
a fault response terminal (208) to enable a frequency setting switch (204) of said frequency setting unit (203) to actuate another said one or more loads (202,202b) with a predetermined frequency to indicate said open load condition.
2. The sequential LED device (200) as claimed in claim1, wherein said one or more loads (202,202b) is said a primary load (202) and secondary load (202b).
3. The sequential LED device (200) as claimed in claim1, wherein said frequency setting unit (203) comprises one or more frequency setting resistors (R11, R10) arranged in parallel and said frequency setting switch (204).
4. The sequential LED device (200) as claimed in claim1, wherein said detecting terminal (207) switches between a low state and a high state.
5. The sequential LED device (200) as claimed in claim1, wherein said fault response terminal (208) is configured to said frequency setting switch (204) of said frequency setting unit (203) through a voltage regulation circuit (205).
6. The sequential LED device (200) as claimed in claim1, wherein said predetermined frequency depends on said frequency setting resistor (R10,R11).
7. The sequential LED device (200) as claimed in claim1, wherein said input terminal (206) is configured to a polarity protection diode (D1), a filter capacitor (C1) and a transient voltage protection zener diode (D8).
8. The sequential LED device (200) as claimed in claim1, wherein said detecting terminal (207) connected to a pull-up resistor (R1).
9. The sequential LED device (200) as claimed in claim1, wherein said one or more loads (202,202b) comprises one or more LEDs arranged in parallel.
10. A method of actuating an output load in a sequential LED device (200) comprising the steps of:
setting a frequency of one or more output load (202,202b);
detecting a fault condition in said one or more output load (202,202b);
changing a state of detecting terminal (207);
switching ON a frequency setting switch (204); and
actuating at least one of said one or more output load (202,202b) at a predetermined frequency.

11. A sequential LED device (200) for a vehicle comprising:
one or more driver unit (201) located on one or more location of said vehicle;
said one or more driver unit (201) configured to set a frequency of one or more loads (202,202b) through a frequency setting unit (203);
a detecting terminal (207) to detect an open load condition in said at least one of the said one or more loads (202,202b); and
a fault response terminal (208) to enable a frequency setting switch (204) of said frequency setting unit (203) to actuate another said one or more loads (202,202b) with a predetermined frequency to indicate said open load condition.
12. The sequential LED device (200) for a vehicle as claimed in claim 10,wherein said one or more location is an instrument cluster or one more turn signal lamp (120,121,122,123) of said vehicle.
13. The sequential LED device (200) for a vehicle as claimed in claim 10, wherein said one or more loads (202,202b) are primary load (202) and a secondary load (202b) located on a right side or a left side of said vehicle.
14. The sequential LED device (200) for a vehicle as claimed in claim 10, wherein said one or more loads (202,202b) comprises one or more LEDs arranged in parallel.
15. A method of actuating a TSL in a vehicle on detecting an open condition comprising the steps of:
setting a frequency of one or more turn signal lamps (120,121,122,123);
detecting a fault condition in said one or more turn signal lamps (120,121,122,123); and
actuating at least one or more turn signal lamps (120,121,122,123) at a predetermined frequency , Description:TECHNICAL FIELD
[0001] The present subject matter generally relates to a sequential LED circuit. More particularly but not exclusively the present subject matter relates to a sequential LED circuit for a turn signal lamp of a vehicle.
BACKGROUND
[0002] The lighting system of a vehicle comprises lighting and signalling devices mounted or integrated to the front, rear and sides of the vehicle. Every vehicle is equipped with several lighting systems comprising of Headlamp, Tail lamp, Brake lamp, Position lamp, Turn signal lamp, Hazard/warning lamp, number plate lamp and other lamps depending on the type and the requirement of the vehicle.
[0003] Turn signal lamps (TSL) also known as "direction indicators" or "blinkers" or "flashers" are signalling lamps mounted near the left and right front and rear corners of a vehicle, activated by the vehicle driver to advertise the intent to take turn towards right or left side or to change the lanes. Turn signal lamps are also used as hazard or warning light in a two-wheeled vehicle.
[0004] Sequential turn signal lamps (TSL) are configured in some vehicles wherein the turn-signal function is provided by multiple illuminating elements like LED(s) connected in sequential manner which, illuminates sequentially rather than simultaneously. The LEDs are illuminated sequentially in a progressive manner from the inner most LED to the outermost LED provided on an LED board such that the sequential illumination represents the intended direction of the vehicle. After all the LEDs in the string are in ON condition and illuminating light, the illumination remains at its full intensity for certain period of time before all the LEDs gets switched OFF and then after a brief interval of time, when all the LEDs remains in OFF condition, the sequence is repeated again.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Figure 1illustrates a block diagram of a conventional turn signal lamp (TSL) system implemented in a vehicle.
[0006] Figure 2illustrates connection topology of the turn signal lamps provided in a vehicle.
[0007] Figure 3illustratesa circuit level diagram of the sequential LED device.
[0008] Figure4 illustrates another embodiment of the present subject matter with more than one output load.
[0009] Figure 5 illustrates a flow diagram to depict a method of actuating an output load in a sequential LED device.
[00010] Figure 6 illustrates a flow chart of functioning of the sequential LED TSL in the vehicle
DETAILED DESCRIPTION
[00011] In an ON-OFF type LED TSL, either all LEDs glow at the same time when turned ON and blink or all LEDs stops glowing when turned OFF. When there is a fault, all the LEDs will not glow, which can be easily detected and the fault is communicated to the corresponding TSL on the same side for operating at double frequency. However, this is not the case with sequential LED TSL. In case of sequential LEDs, during its normal functioning, there is a point at which all LEDs do not glow which potentially can result in faulty activation of LED which is undesirable. Hence, there is a need for a solution such that the controller should not misinterpret it to be a fault condition and incorrectly communicate to the corresponding LED on the same side to operate in double frequency.
[00012] Sequential LED turn signal lamps are more noticeable compared to the conventional lighting systems which are ON-OFF illumination type. But identifying a failure of lamp in the sequential turn signal lamp is complex compared to ON-OFF illumination type lamp. In order to find out the failure in any one of the LED string in the sequential LED turn signal lamps, power consumption is determined at any instant of a cycle. A fault is detected by differentiating a start or end cycle of power consumption from a lamp failure condition.
[00013] The LED driver circuit comprises of switch elements that are connected in parallel to the LEDs and the resistors are connected in series with the LEDs and the switches. When the switch is in ON condition, current flows through the resistor as well as the switch and the corresponding LED, connected in parallel, remains in OFF condition. But when the switch is OFF, current flows through the LED. The control unit sequentially turns ON the LEDs by controlling the corresponding switch state. At any given instant the current flows through the LED or through the parallel path having the switch element. Therefore, the current flows through the parallel path all the time. Since, the battery capacity of a two wheeled saddle type vehicle is lower compared to a four wheeler or a three wheeler vehicle; therefore it becomes a concern when current is always flowing in the circuit to control the sequential LED turn signal lamp even if the LED of the turn signal lamp is not in ON condition. Eventually such solution in known art renders the battery of the vehicle vulnerable to being drained out which can adversely impact the startability & reliability of the vehicle as well as durability of the battery.
[00014] Hence, the present subject matter provides a sequential LED device which eliminates the drawback related to the existing State-of-Art i.e. the circuit for the sequential LED driver draws unnecessary power from the battery of the vehicle to detect a fault condition in the sequential LED lamp. To overcome this drawback, the present subject matter provides a sequential LED device where a driver unit is configured to a plurality of output loads with plurality of LED strings arranged in parallel configuration. The driver unit drives the plurality of output load based on detecting an open load condition in any LED string of the said output load. A fault response terminal to enable a frequency setting switch in order to actuate said output load with a predetermined frequency.
[00015] Yet another aspect of the present subject matter is to provide a detecting terminal which is connected to a pull-up resistor. When a fault occurs in any of the LED string in the output load i.e. plurality of LEDs then the state of the detecting terminal (207) as shown in Fig 3 changes from low state to high state and the driver unit senses this change of the state at the detecting terminal. The detecting terminal is an open drain output which has a low state during no fault condition. The output load is primary load and a secondary load which represents the TSL on one side of the vehicle (either left or right) located in the front side and rear side of the vehicle respectively. If a fault occurs in a primary load then the secondary load indicates the fault. If the fault occurs in the secondary load then the primary load indicates the fault.
[00016] A detecting terminal which is connected to the pull-up resistor changes from low state to high state when any of the LED gets open (faulty) and when the state of the detecting terminal is high then the corresponding voltage is provided to a fault response terminal.
[00017] Still another aspect of the present subject matter provides a fault response terminal configured to the driver unit to enable changing a frequency of said plurality of LEDs through a frequency setting unit during fault condition. The driver unit is connected to the frequency setting unit through a frequency setting pin. The frequency setting unit comprises of a frequency setting switch which can be an NMOS (N-type MOSFET) switch. Further, one or more frequency setting resistors are arranged in parallel such that one of the frequency setting resistors is in series with the frequency setting switch and during the fault condition the frequency setting resistor, arranged in series with the frequency setting switch, gets activated and changes the frequency of the output load to indicate fault.
[00018] Fig. 1 illustrates a conventional turn signal lamp (TSL) system in a vehicle. The input end of the flash unit (106,105) is fed with one or more power input such as a battery (103) or a magneto (102). The magneto (102) provides alternating current (AC) whereas the battery provides a direct current (DC). One of the terminals of the magneto (102) and the battery (103) are electrically connected to a zero voltage by grounding the terminals to the ground (113) at zero potential. The input received from the magneto (102), by the flasher unit (106,105), is an AC current and therefore the input from the magneto (102) goes through a rectification process and also a regulation process to control the voltage level in order to make the voltage suitable for powering the flasher unit (106,105) and the turn signal lamps (TSL) connected to the flasher unit (106,105). The RR unit (regulation rectification unit) (104) regulates the incoming voltage received from the magneto (102) and at the same time the RR unit (104) converts the incoming alternate current (AC) voltage from the magneto (102) into a DC current through the process of rectification.
[00019] The flasher unit is further connected to a TSL switch (104). The TSL switch (104) may be operated manually or automatically. The TSL switch (104) connects the turn signal lamps located on the front (right and left hand side), back (right and left hand side) and the lateral sides of the vehicle.
[00020] An ignition switch (165) is provided before the flasher unit such that whenever the ignition is switched ON only then the turn signal lamps (TSL) will operate otherwise during the ignition OFF condition the turn signal lamps (TSL) will not operate.
[00021] Fig. 2 illustrates connection topology of the turn signal lamps provided in a vehicle as per the present invention. Each turn signal lamp is provided with a TSL driver circuit. Each of the TSL driver circuit comprises a detecting terminal and a fault terminal. The detecting terminal of the right side front TSL (123) is connected to fault terminal of the right side rear TSL (122) and the detecting terminal of the right side rear TSL (122) is configured to fault terminal of the right side front TSL (123).
[00022] Similarly, the detecting terminal of the left side front TSL (120) is configured to fault terminal of the left side rear TSL (121) and the detecting terminal of the left side rear TSL (121) is configured to fault terminal of the left side front TSL (120).
[00023] The detecting terminal in each of the TSL diagnoses whether there is any fault in any of the LED in the TSL. When a fault occurs in the right side front TSL (123) then the fault terminal detects the fault and the right side rear TSL (122) starts blinking at double the speed to indicate the fault in the right side front TSL (123). Similarly, the detecting terminal in the right side rear TSL (122) diagnosis the right side rear TSL (122) for any open condition in any of the LED. When the fault occurs in the right side rear TSL (122) then the fault terminal detects the fault and the right side front TSL (123) starts blinking at double the frequency. The frequency to indicate the fault in the TSL can be controlled by a frequency setting resistor (not shown).
[00024] Each TSL has a driver unit in one of the embodiment or in an another embodiment, two driver (one driver unit for left and second driver unit for right) unit controlling each side TSL (both front and rear) of the vehicle. The driver unit can be located in an instrument cluster of the vehicle or on the TSL of the vehicle itself.
[00025] Fig. 3illustrates a circuit level diagram of the sequential LED device (200). The sequential LED device (200) comprises a plurality of LEDs (LED1,LED2, LED3, LED4) configured in parallel to receive an input power from an input terminal (206) connected to a power source such as a battery (103) or a magneto (102). The input terminal is connected to a reverse polarity protection diode (D1) to ensure that the sequential LED device (200) does not suffer damage if the power supply polarity is reversed. Reverse polarity protection diode (D1)cuts off the power when the polarity changes from positive to negative (in the present embodiment). The positive side of the reverse polarity protection diode (D1) is connected to the power source and the negative side of the reverse polarity protection diode (D1) is connected to a filter capacitor (C1) arranged in parallel with a transient voltage protection zener diode (D8). Hence, the reverse polarity protection diode (D1) prevents damage to the circuit when the polarity changes from positive to negative. The filter capacitor (C1) filters out unwanted frequency signals and the transient voltage protection zener diode (D8) (or transient protection suppression diode) protects the circuit from voltage spikes induced on the wires connecting the circuit.
[00026] Further, a driver unit (201) configured to set a frequency of said plurality of LEDs (202) through a frequency setting unit (203). The driver unit (201) is connected to the frequency setting unit (203) through a frequency setting pin (210). The frequency setting unit (203) comprises of a frequency setting switch (204) which can be an NMOS (N-type MOSFET) switch (204). Further, frequency setting resistors (R11, R10) are connected in parallel arrangement such that one of the frequency setting resistors (R11) is in series with the frequency setting switch (204).
[00027] A detecting terminal (207) is configured to a pull-up resistor (R1). When a fault occurs in any of the LED in the plurality of LEDs (201) then the state of the detecting terminal (207) changes from low state to high state and the driver unit (201) senses this change of state at the detecting terminal (207). The detecting terminal (207) is an open drain output which has a low state during no fault condition. The detecting terminal (207) which is connected to the pull-up resistor (R1) changes from low state to high state when any of the LED gets open (faulty) and when the state of the detecting terminal (207) state is high then the voltage is provided to a fault response terminal (208).
[00028] The fault response terminal (208) is connected to the frequency setting unit (203) through a voltage regulation circuit (205) to allow regulation of voltage received by the fault response terminal (208). The voltage regulation circuit comprises of a voltage regulator zener diode (D7) arranged in parallel with a regulating resistor (R9) and in series with serial resistor (R8).
[00029] The voltage received by the fault response terminal (208) is transferred to the frequency setting unit (203). When the detecting terminal (207) is at low state then the setting switch (204) remains in an OFF condition as no voltage is provided to the fault response terminal (208) and the frequency setting resistor R10 sets the frequency of the load but when the detecting terminal (207) is in High state, after detecting an open condition in any of the LED string, then the frequency setting switch (204) switches ON.
[00030] After the frequency setting switch (204) switches ON then the overall resistance changes from R10 to R11 R10 (R11 R10 = R11 R10 / R11+ R10 ). Since, the overall resistance change leads to change in the frequency at the frequency setting pin (210); the change of the frequency leads to change in the frequency of the plurality of LEDs (202) in order to indicate fault in an LED string. Therefore, the fault response terminal (208) actuates said plurality of load (LEDs) with a predetermined frequency set by setting resistors. The plurality of LEDs (202) starts blinking at a different frequency to indicate the fault in the load when the setting resistor R11 connected to frequency setting switch (204) in series gets activated with the activation of the frequency setting switch (204) .
[00031] Fig. 4 illustrates another embodiment of the present subject matter where the fault in the any of the LED string in the plurality of LEDS (202) leads to change in the frequency in the secondary load (202b) which is also a set of LEDs arranged in parallel configuration e.g. an front or a rear TSL of the vehicle. This is applicable in TSL of a vehicle when one TSL of a particular side get a fault then the other TSL of the same side gets activated with different frequency which causes faster blinking to indicate the fault.
[00032] When the state of the detecting terminal (208) changes from low state to high state after detecting a fault in at least one LED string in the plurality of LEDs (202) then the fault response terminal (208), responding to the change in the state of the detecting terminal (208), enables a frequency setting switch (204) in order to actuate the secondary load with a double frequency. So, the secondary load (202b) gives visual indication when a fault occurs in any of the LED in the plurality of LEDs (202).
[00033] Fig. 5illustrates a flow diagram to depict a method of actuating an output load in a sequential LED device (200). In step 501, the output load i.e. a plurality of LEDs (202) are set at a particular frequency through resistor R10 as the fault response terminal (208) is not receiving any voltage from the detecting terminal (207) because when there is no fault in the output load then the detecting terminal (207) is at low state (zero voltage)and the therefore frequency setting switch (204) of the frequency setting unit (203) is in OFF condition. Since there is no voltage received by the frequency setting unit (203), the setting resistor R11 is inactive as the frequency setting switch (204) is in OFF condition.
[00034] But when any of the LED string in the output load gets in open condition, a fault condition is detected by the detecting terminal (207) in step 502 and the low state of the detecting terminal (207) gets pulled up by the pull-up resistor (R1) and state of the detecting terminal (207) changes to high state in step 503. When the state of the detecting terminal (207) is high then the fault response terminal (208) receives a 12 V input and in step 504, the frequency setting switch (204) of the frequency setting unit (203) gets switched ON due to which, the inactive setting resistor R11 becomes active and the overall resistance changes to R10||R11 (R10R11) in parallel condition (decrease in resistance). This change of the overall resistance leading to change in the frequency of the output load. The frequency increases with decrease in the overall resistance of the frequency setting unit (203). The output load gets actuated (in step 505) due to change in the frequency and the output load starts blinking more frequently to indicate a fault. If the fault occurs in the secondary load (202b) then primary load (202) can be used to indicate the fault in the secondary load (202). A specific fault detection voltage can be set for each of the load e.g. 12V for the primary load (202) and 6V for the secondary load.
[00035] The fault in the output load can be indicated in the same load or in a different load such as a secondary load (202b). This application is implemented in vehicle. If the front TSL of one side gets faulty then the rear TSL of the same side gets actuated to blink at faster rate to indicate a fault in the front TSL.
[00036] Fig. 5 illustrates a flow chart of functioning of the sequential LED TSL in the vehicle such that in step 601 each of the TSL in vehicle is set to a frequency and all the TSL operate at a same frequency during normal operating condition. In step 602, when any TSL has open condition implying a detection of a fault condition in any TSL, then in step 603 the corresponding TSL on the same side (either rear or front) is actuated as an alert or visual alarm indication e.g. the TSL starts blinking at a predetermined frequency based on the value of the resistor in the frequency setting unit (203).