Field of the Invention:
The invention belongs to flasher units for use in vehicles.
Background of the Invention:
Visible turn indicators have virtually become standard equipment on all modern motor vehicles, and in fact, most, if not all, vehicular licensing authorities require licensed vehicles to be equipped with visible front turn indicators and rear turn indicators. The most acceptable and most widely used front turn indicators are a pair of illuminating devices mounted on a front side of the vehicle. Likewise, the most acceptable and widely used rear turn indicators are a pair of illuminating devices mounted on a rear side of the vehicle. In addition to the above, some vehicles (predominantly of the four-wheel category) have illuminating devices mounted on the side surfaces of the vehicle.
The illuminating devices are arranged for manual energization by the driver. For example, when a left-hand movement or turn or bend is intended, the driver actuates a lever or a switch in a first direction so that the illuminating devices mounted on the left-hand side of the vehicle will get illuminated. Likewise, when a right-hand movement or turn or bend is intended, the driver actuates the lever or the switch in a second direction so that the illuminating devices mounted on the right-hand side of the vehicle will get illuminated.
Also, in most cases, instead of being continuously illuminated the illuminating devices flash ON and OFF. By way of example, the illuminating devices may flash ON and OFF at the rate of heart beat. By way of another example, the illuminating devices will be in an ON state for let's say 1 second, will then be in an OFF state for 1 second and this cycle will go be repeated. Thus, a flasher unit is provided in the vehicle that ensures that the illuminating devices flash ON and OFF.
In this regard, reference may be made to U.S. Patent No. 4,692,736 that teaches a flasher for flashing a vehicle light, comprising a manual switch; an interval means coupled to said manual switch for providing in response to its operation a duration signal of at least a predetermined duration; cycling means coupled to said interval means for providing a periodic cycling signal in response to and for the duration of said duration signal, said predetermined duration of said duration signal exceeding the period of said periodic cycling signal; pulsing means for providing a power output, said pulsing means being coupled to said cycling means for blanking said power output in response to and synchronously with said

cycling signal; and substitution means coupled to said power switch, said interval means and said pulsing means for repowering said light from said pulsing means instead of said power switch in response to and for the duration of said duration signal, said substitution means being operable by said interval means in the absence of said periodic signal from said cycling means to power said vehicle light for said predetermined duration, whereby said vehicle light is flashed for said predetermined duration.
A further reference may be made to U.S Patent No. 5,309,142 that teaches an electronic flasher unit for controlling a plurality of flashing lamps and connectable to a battery, an ignition switch connected to the battery, a turn indicator switch, a hazard warning flasher switch, and a grounding point, said electronic flasher unit comprising: a battery terminal connectable to the battery; a ground terminal connectable to the grounding point; at least a first, a second, and a third control input terminal connectable respectively to the ignition switch, the turn indicator switch, and the hazard warning flasher switch; a flashing relay having a plurality of relay contacts that are connected respectively to said second and said third control input terminals; an integrated circuit which has a first connecting pin which controls said flashing relay, a second connecting pin which is a measuring input and is connected to said plurality of relay contacts and is also connected, via a measuring resistor, to said battery terminal, a third connecting pin which is a hazard warning flasher input and is connected, via an inner resistor which is inside said integrated circuit, to said second connecting pin and is also connected, via a first resistor, to said third control input terminal, and a fourth connecting pin which is a turn indicator input and is connected, via a second resistor, to said second control input terminal; a plurality of resistors coupled to said first, said second, and said third control input terminals, wherein said plurality of resistors output a plurality of voltage drops in response to the input of at least a first, a second, and a third switch setting signal from said first, said second, and said third control input terminals, respectively; and a switching means, within said integrated circuit, coupled to said plurality of resistors via a plurality of connecting pins of said integrated circuit, to change the operating state of said integrated circuit in response to said plurality of voltage drops from said plurality of resistors.
A further reference may be made to U.S. Patent No. 6,069,559 that teaches a programmable turn signal and hazard flasher control system, comprising: a shunt resistor having one end adapted for connection to a voltage source and an opposite end adapted for coupling in a first

mode to a first number of vehicle loads and in a second mode to a second number of vehicle loads; means responsive to a load activation request signal for conducting a first load current through said shunt resistor in said first mode and a second load current through said shunt resistor in said second mode; a control circuit having a first input connected to said opposite end of said shunt resistor, a second input and an output, said control circuit responsive to a first signal state at said second input to produce a load activation signal at said output when said shunt resistor is conducting said first load current there through and to a second signal state at said second input to produce said load activation signal at said output when said shunt resistor is conducting said second load current there through; and a monitoring circuit having an input coupled to said output of said control circuit and producing a warning signal at an output thereof if said load activation signal falls outside of a load activation signal range.
A furthermore reference may be made to U.S. Patent No. 7,852,203 that teaches a vehicular flasher unit comprising: a control circuitry; memory which is accessible by the control circuitry and having a plurality of flasher scheme data sets stored therein which correspond to a plurality of flasher schemes for vehicle flasher lights of a vehicle; a flasher scheme selection input to the control circuitry; a flasher enable input to the control circuitry which enables a flasher scheme in the vehicular flasher lights; a light illumination output from the control circuitry which controls illumination of the vehicle flasher lights; the control circuitry being operative to: monitor the flasher enable input to identify a flasher enable signal; producing, at a light illumination output in response to identifying a flasher enable signal, an output signal in accordance with a selected set of flashing scheme data for illuminating a flasher scheme in the vehicle flasher lights; wherein the set of flasher scheme data comprises heartbeat scheme data corresponding to a heartbeat flashing scheme in the vehicle flasher lights; the heartbeat flashing scheme comprising a repeating sequence of two heartbeat pulse flashes in the vehicle flasher lights including a first heartbeat pulse flash and a second heartbeat pulse flash; each first heartbeat pulse flash of the heartbeat flashing scheme having a first peak intensity in the vehicle flasher lights and each second heartbeat pulse flash having a second peak intensity in the vehicle flasher lights that is the same as or different from the first peak intensity; and each first heartbeat pulse flash of the heartbeat flashing scheme being separated from its following second heartbeat pulse flash by a first time duration and each second heartbeat pulse flash being separated from its following first heartbeat pulse by a second time duration that is greater than the first time duration.

While different types of electronic flashers are available, the need to provide a cost-effective mechanism still exists. While being cost-effective, it is desirable that the electronic flasher includes a mechanism for indicating a lamp failure condition.
It has been furthermore observed that in some instances, a load terminal is short-circuited to a ground. Such short-circuiting of the load terminal to the ground may affect one or more components of the electronic flasher. This may also affect wiring harness as generally are present in the vehicle. Thus, it is furthermore desirable that electronic flasher includes protection mechanism to cater to scenario wherein a load terminal is short-circuited to a ground.
Summary of the Invention:
Accordingly, the present invention provides a discrete flasher unit (100) for use in vehicles. The discrete flasher unit (100) is connectable to a battery (1) and a turn indicator switch (2) and a grounding point (12) and is adapted for controlling a plurality of flashing lamps (31, 3LR, 3LF, 3RR, and 3RF). The discrete flasher unit (100) comprises a square wave oscillator circuit (5) configured to generate square wave signals. The discrete flasher unit (100) further comprises a lamp load driver (6) operably connected between the battery (1) and the turn indicator switch (2). The lamp load driver (6) is configured to receive the square wave signal from the square wave oscillator circuit (5) and a supply as provided by the battery (1) and generate a lamp load driving current. The discrete flasher unit (100) further comprises a current sensing element (7) operably connected between the lamp load driver (6) and the turn indicator switch (2). The current sensing element (7) is configured to generate a current sense signal based on a drop-out voltage technique. The discrete flasher unit (100) further comprises a signal conditioning unit (8) operably connected to the current sensing element (7). The signal conditioning unit (8) is configured to receive the current sense signal and produce an amplified current sense signal. The discrete flasher unit (100) further comprises a flashing rate control block (9) configured to receive the amplified current sense signal. The flashing rate control block is further configured to produce a first flashing signal having a first frequency or a second flashing signal having a second frequency. In particular, the flashing rate control block produces the first flashing signal having the first frequency if a value of the amplified current sense signal is below a first preset threshold limit. Alternatively, the flashing rate control block produces the second flashing signal having the second frequency if the value of the amplified current sense signal is above the first preset

threshold limit. The flashing rate control block is further configured to provide the first flashing signal or the second flashing signal to the square wave oscillator circuit (5) to control a frequency of the square wave signal thus generated. The discrete flasher unit (100) further comprises an overcurrent protection block (10) configured to receive the current sense signal from the current sensing element (7). The overcurrent protection block (10) is further configured to keep the lamp load driver (6) in an OFF state if a value of the current sense signal is above a second preset threshold limit, the second preset threshold limit beign higher than the first preset threshold limit.
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is to be appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.
Brief Description of Figures:
These and other features, aspects, and advantages of the present invention will become better
understood when the following detailed description is read with reference to the
accompanying drawings in which like characters represent like parts throughout the
drawings, wherein:
FIGURE 1 illustrates a block diagram of a turn indicator circuit including the discrete flasher
unit (100);
FIGURE 2 illustrates a detailed circuit diagram of a charge pump circuit (4) in accordance
with an embodiment of the present invention;
FIGURE 3 illustrates a detailed circuit diagram of a square wave oscillator circuit (5) in
accordance with an embodiment of the present invention;
FIGURE 4 illustrates a detailed circuit diagram of a lamp load driver (6) in accordance with
an embodiment of the present invention;
FIGURE 5 illustrates a detailed circuit diagram of a current sensing element (7) in
accordance with an embodiment of the present invention;
FIGURE 6 illustrates a detailed circuit diagram of a signal conditioning block (8) in
accordance with an embodiment of the present invention;

FIGURE 7 illustrates a detailed circuit diagram of a flashing rate control block (9) in
accordance with an embodiment of the present invention;
FIGURE 8 illustrates a detailed circuit diagram of an overcurrent protection block (10) in
accordance with an embodiment of the present invention;
FIGURE 9 illustrates a detailed circuit of the discrete flasher unit (100) in accordance with
an embodiment of the present invention;
FIGURE 10(a) illustrates a first waveform produced at location 14 with reference to location
11L under full load condition in accordance with an embodiment of the present invention;
FIGURE 10(b) illustrates a second waveform produced at location 11L with reference to
location 12 under full load condition in accordance with an embodiment of the present
invention;
FIGURE 10(c) illustrates a third waveform produced at location 14 with reference to
location 11L under load failure condition in accordance with an embodiment of the present
invention; and
FIGURE 10(d) illustrates a fourth waveform produced at location 11L with reference to
location 12 under load failure condition in accordance with an embodiment of the present
invention.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
Detailed Description:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that one or more devices or sub-systems or elements or structures or components proceeded by "comprises a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Referring to Figure 1, there is illustrated a block diagram of a turn indicator circuit for use in a vehicle. As can be seen, the turn indicator circuit comprises a battery (1), a turn indicator switch (2), a plurality of turn signal flashing lamps (31, 3LR, 3LF, 3RR and 3RF), a grounding point (12) and a discrete flasher unit (100) connected between the battery (1) and the turn indicator switch (2). The discrete flasher unit (100) is adapted for controlling the plurality of turn signal flashing lamps (31, 3LR, 3LF, 3RR, and 3RF). It may be noted that power to the discrete flasher unit and turn signal flashing lamps may be supplied from the battery (1). Although not illustrated, in some cases, the power to the discrete flasher unit

(100) and turn signal flashing lamps may be supplied by an alternate current generator (ACG) as may be provided in the vehicle (in case the battery is not available or has no charge).
In an embodiment, the turn indicator switch (2) may be a three-point contact switch defining a neutral position (2N), a first actuated position (2L) and a second actuated position (2R). In case the discrete flasher unit is used in a vehicle to flash ON and OFF the left and right turn signal flashing lamps, the neutral position (2N) of the turn indicator switch (2) may correspond to all turn signal flashing lamps being in OFF state. When the turn indicator switch (2) is at first actuated position (2L), left turn signal flashing lamps (3LR and 3LF) will start flashing and when turn indicator switch (2) is at second actuated position (2R), a right signal flashing lamps (3RR and 3RF) will start flashing. It may be noted that for the purposes of ease of reference, 3LF indicates Left, Front turn signal flashing lamp; 3LR indicates Left, Rear turn signal flashing lamp; 3RF indicates Right, Front turn signal flashing lamp; 3RR indicates Right, Rear turn signal flashing lamp, and 31 indicates turn signal indicator lamp (as may be provided on a dashboard or a handlebar console of the vehicle).
In an embodiment of the invention, the discrete flasher unit (100) comprises a square wave oscillator circuit (5). The square wave oscillator circuit (5) may be configured to generate different types of square wave signals, as will be described in detail in subsequent portions.
In an embodiment, the discrete flasher unit (100) further comprises a lamp load driver (6) operably connected between the battery (1) and the turn indicator switch (2). The lamp load driver (6) may be configured to receive the square wave signal from the square wave oscillator circuit (5) and a supply as provided by the battery (1) and generate a lamp load driving current.
In an embodiment, the discrete flasher unit (100) further comprises a current sensing element
(7) operably connected between the lamp load driver (6) and the turn indicator switch (2).
The current sensing element (7) may be configured to generate a current sense signal based
on a drop-out voltage technique.
In an embodiment, the discrete flasher unit (100) further comprises a signal conditioning unit
(8) operably connected to the signal conditioning unit (7). The signal conditioning unit (8)
may be configured to receive the current sense signal and produce an amplified current sense
signal.

In an embodiment, the discrete flasher unit (100) further comprises a flashing rate control block (9) configured to receive the amplified drop out voltage signal. The flashing rate control block (9) may be further configured to produce a first flashing signal having a first frequency or a second flashing signal having a second frequency. In particular, the flashing rate control block may be configured to produce the first flashing signal having the first frequency, if a value of the amplified current sense signal is below a first preset threshold limit. Alternatively, the flashing rate control block may be configured to produce the second flashing signal having the second frequency if the value of the amplified current sense signal is above the first preset threshold limit. In an embodiment, the first preset threshold limit of the amplified current sense signal may correspond to a lamp load failure condition. The flashing rate control block may be further configured to provide the first flashing signal or the second flashing signal to the square wave oscillator circuit (5) to control a frequency of the square wave signal thus generated.
In an embodiment of the invention, the discrete flasher unit (100) further comprises an overcurrent protection block (10). The overcurrent protection block (10) may be configured to receive the current sense voltage signal from the current sensing element (7). The overcurrent protection block (10) may be further configured to keep the lamp load driver (6) in an OFF state if a value of the current sense signal is above a second preset threshold limit. In an embodiment, the second preset threshold limit of the current sense signal is higher than the first preset threshold limit of the current sense signal. In an embodiment, the second preset threshold limit of the current sense signal may correspond to a load terminal short circuit condition.
In an embodiment of the invention, the discrete flasher unit (100) further comprises a charge pump circuit (4). The charge pump circuit (4) may be connected to the battery (1) and may act as a power source for the electrical and electronic components forming part of the discrete flasher unit (100).
While all the components of the discrete flasher unit (100), their interconnection and the basic principle of operation has been described with reference to Figure 1, in the following paragraphs, each component of the discrete flasher will be described in further detail with reference to a corresponding figure.

Referring now to Figure 2, there is shown a detailed circuit diagram of the charge pump circuit (4). The charge pump circuit (4) may comprise a capacitor Cll which may be connected to the battery (1) via a uni-directional current flow device such as a diode Dl. The capacitor Cll may get charges during off cycle (when turn signal flashing lamps are OFF) of the flasher. When turn signal flashing lamps (31 or 3LF or 3LR or 3RF or 3RR) are in ON state, voltage at output terminal (11L) of the discrete flasher unit (best seen in Figure 1) will be approximately same as battery (1) voltage and capacitor Cll acts as power source for the electrical and electronic components forming part of the discrete flasher unit (100).
Referring now to Figure 3, there is shown a detailed circuit diagram of the square wave oscillator circuit (5). The square wave oscillator circuit (5) comprises of Transistors Ql, Q2, and Q4; Capacitors CI, C2, C5, C6, C9, and CIO; Resistors Rl, R2, R3, R4, R15, R16, R21 and R22; and Diode D4 connected in a manner as shown in Figure 3.
In particular, the square wave oscillator circuit (5) comprises a transistor Q2 (comprising a collector terminal, a base terminal, and an emitter terminal) having its collector terminal connected to location 13. To the location 13, a series combination of Resistors R3, R21 and R22 is connected. The emitter terminal of the transistor Q2 is connected to a common point to which the load is connected. The base terminal of the transistor Q2 is connected to location 14 via a series combination of Resistors R4 and R5. A first terminal of a Capacitor C5 is coupled to the common point to which the load is connected. A second terminal of the capacitor C5 is connected to a location between the base terminal of the transistor Q2 and the resistor R4. A resistor R15 is further provided such that one end of the resistor R15 is connected to the common point to which the load is connected and another end of the resistor R15 is connected to a location between the base terminal of the transistor Q2 and the resistor R4 such that the Resistor R15 is electrically parallel to the capacitor C5. A capacitor CIO is connected between the base terminal of the transistor Q2 and the series combination of Resistors R3, R21, and R22. A Resistor Rl is further connected in an electrical path between the series combination of Resistors R3, R21 and R22 and the Capacitor CIO and a location between the Resistor R4 and Resistor R5. To about a location between the Resistor R4 and Resistor R5, a collector terminal of a transistor Ql is connected. An emitter terminal of the transistor Ql is connected to a common point to which the load is connected. A Capacitor C6 is connected between a base terminal of the transistor Ql and the common point to which the load is connected. Also, a Resistor R16 is connected between a base terminal of the transistor

Ql and the common point to which the load is connected such that the Resistor R16 is electrically parallel to the Capacitor C6. The base terminal of the transistor Ql is connected to location 14 via a Resistor R2. A capacitor CI is connected between the location 14 and the common point to which the load is connected.
By way of a non-limiting example, the square wave oscillator circuit (5) may generate a square wave signal of a first frequency under full load condition. In the present example, the full load condition is represented by 3LF+3LR+3I or 3RF+3RR+3I. By way of a non-limiting example, under the full load condition, the square wave oscillator circuit (5) may generate square wave signal having a frequency of about 1.4Hz.
By way of a non-limiting example, the square wave oscillator circuit (5) may generate a square wave signal of a second frequency under lamp failure condition. In the present example, the lamp failure condition may be represented by 3LF+3I or 3LR+3I or 3RF+3I or 3RR+3I or 31 being in ON state or ALL lamp failure condition. By way of a non-limiting example, under the lamp failure condition, the square wave oscillator circuit (5) may generate square wave signal having a frequency of about 2.8Hz. It may be noted that the square wave signals as generated by the square wave oscillator circuit (5) may be received as input by the lamp load driver (6).
In the following paragraphs, the functioning of the square wave oscillator circuit (5) in terms of generating the square wave signal of a first frequency under full load condition and generating the square wave signal of a second frequency under lamp failure condition is described.
Case 1: Full Load condition:
The transistor Q4 is in ON state. When turn indicator switch (2) switches from neutral position (2N) to any one of the first actuated position (2L) or the second actuated position (2R), capacitors C2 and C9 starts charging through resistors R3, R21, R22 and R2 which supplies current to the base of transistor Ql which results in transistor Ql going to a saturation region and hence Q2 remains in cut off region. As a result, a HIGH voltage is developed at location 13 which functions as the output of the square wave oscillator circuit (5) and to which the lamp load driver (6) is connected. The lamp load driver (6) comes to ON state which allows current flow to the lamp loads.

Subsequently, the current through capacitors C2 and C9 decreases exponentially, resulting in transistor Ql going to the cut-off region. Current flows through resistor Rl and R4 to the base of Q2 which results in Q2 going to the saturation region. The voltage at location 13, therefore, becomes LOW and lamp load driver (6) comes to OFF state.
At the same time, equal and opposite charge to the positive plate of C2 and C9 is developed at the negative plate of the C2 and C9. In this way, the cycle repeats continuously. Values of R3, R21, R22, R2, and C2, C9 decide the frequency of oscillation.
Case 2: Lamp Failure Condition:
In the lamp failure condition, the transistor Q4 is in OFF state. When When turn indicator switch (2) switches from neutral position (2N) to any one of the first actuated position (2L) or the second actuated position (2R), capacitor C9 starts charging through resistors R3, R21, R22 and R2 which supplies current to the base of Ql which results in Ql going to a saturation region and hence Q2 remains in cut off region. As a result, the HIGH voltage developed at location 13 which functions as the output of the square wave oscillator circuit (5) and to which the lamp load driver (6) is connected. The lamp load driver (6) comes to ON state which allows current flow to the lamp loads.
Subsequently, the current through capacitor C9 decreases exponentially, this results in transistor Ql going to the cut-off region. Current flows through resistor Rl and R4 to the base of Q2 which results in Q2 going to the saturation region. The voltage at location 13, therefore, becomes LOW and lamp load driver (6) comes to OFF state.
At the same time, equal and opposite charge to the positive plate of C9 is developed at the negative plate of C9. In this way, the cycle repeats continuously. Values of R3, R21, R22, R2, and C9 decide the frequency of oscillation.
Referring now to Figure 4, there is shown a detailed circuit diagram of the lamp load driver circuit (6). The lamp load driver circuit (6) comprises of a MOSFET switch Q3; Capacitor C8; Resistors R6 and R18; and Zener Diode Zl connected in a manner as shown in Figure 4.
In particular, the MOSFET switch Q3 may be an N channel MOSFET with low on-state resistance and defining a source terminal, a drain terminal and a gate terminal. The source terminal of the MOSFET switch Q3 may be connected through the current sensing element (7) to the common point to which the load is connected. The drain terminal of the MOSFET

switch Q3 is connected to the Battery (1). A gate terminal of the MOSFET switch Q3 is connected via a first electrical path to a location between the diode Dl and the Capacitor Cll. The first electrical path may include a Zener diode Zl. The gate terminal of the MOSFET switch Q3 is further connected to the common point to which the load is connected via a second electrical path. The second electrical path may include a Resistor R18. The gate terminal of the MOSFET switch Q3 is further connected to the common point to which the load is connected via a third electrical path. The third electrical path may include a Resistor R6 and a Capacitor C8 connected in series. The third electrical path and the second electrical path may be interconnected.
The MOSFET switch Q3 becomes ON when a HIGH signal is received at location 13 and remains OFF when a LOW signal is received at location 13. Lamp load becomes ON when Q3 is on and Vice versa.
Now referring to Figure 5, there is shown a detailed view of the current sensing element. The current sensing element (7) may be a low resistance value, high wattage resistor (R7). The output of the current sensing element (7) is supplied as input to the block (8) and (10). The current sensing elements allow for lamp failure detection and over-current shutdown of the discrete flasher unit (100).
Since the value of the current sensing resistor R7 is very less, the voltage drop across R7 resistor and hence, the amplitude of the current sense signal may be very low. In some instance, it may be beneficial to amplify the current sense signal thus produced by the current sensing resistor R7 to produce amplified current sense signal. To boost this current sense signal produced by the current sensing resistor R7, a signal conditioning block may be used. Referring to Figure 6, there is shown a detailed circuit diagram of a signal conditioning block (8). The signal conditioning block (8) uses an Op-Amp as non-inverting voltage amplifier with a predetermined gain. The signal conditioning block (8) receives current sense signal from the current sensing element (7) and produces amplified current sense signal (15). The amplified current sense signal (15) is supplied as input to the flashing rate control block (9). The signal conditioning block (8) includes resistors R8, R9, R13 and R14 and an Op-Amp U1A connected in a manner as shown in Figure 6. In particular, the Op-Amp based non-inverting voltage amplifier includes a first non-inverting input terminal, a second inverting input terminal, an output terminal connected to the second inverting input terminal via a first electrical path, the first electrical path including a Resistor R9; the second inverting input

terminal being connected to the common point to which the load via a second electrical path; the second electrical path including a Resistor R13; the first non-inverting input terminal being connected between the lamp load driver circuit and the current sensing element (7) via a third electrical path; the third electrical path including a Resistor R8; and the first non-inverting input terminal being connected to the common point to which the load is connected via a fourth electrical path; the fourth electrical path including a Resistor R14.
As mentioned above, the discrete flasher unit (100) operates in two modes-
- Full load mode; and
- Lamp failure mode.
In the full load mode, flashing frequency is approximately equal to 1.4 Hz and in Lamp failure mode, flashing frequency is approximately equal to 2.8Hz. This is beneficial for the end user to detect failure of any turn signal lamp. The flashing rate control block (9) helps in attaining the different flashing rates as mentioned above. It may, however, be noted that flashing rate control block (9) may be configured to provide two different flashing rates and not essentially the flashing rate of 1.4 Hz and 2.8 Hz. Now referring to Figure 7, the flashing rate control block (9) consists of -
Op-Amp - non-inverting comparator circuit; and
- Transistorised switch circuit to drive capacitor C2 optionally along with the
Capacitor C9.
The Op-Amp-non-inverting comparator circuit comprises Op-Amp U2B, Resistors RIO, Rll and R12 and capacitors C3 and C4. In particular, the Op-Amp-non-inverting comparator U2B includes a first non-inverting input terminal, a second inverting input terminal, and an output terminal. The first non-inverting input terminal is adapted to receive the amplified current sense signal as produced by the signal conditioning block (8). The second inverting input terminal is connected to the common point to which the load via a second electrical path; the second electrical path including a Capacitor C4. The second inverting input terminal is connected to the common point to which the load is connected via a third electrical path; the third electrical path including a Resistor Rll, such that Resistor Rll and Capacitor C14 are electrically parallel to one another. The second inverting input terminal being further connected to the battery via a fourth electrical path; the fourth electrical path including a Resistor RIO. A Capacitor C3 is provided in a fifth electrical path provided between the battery and the common point to which the load is connected.

The Transistorised switch circuit comprises a transistor Q4 and a Diode D4 driving the Capacitor C2 optionally along with the Capacitor C9. The Transistorised switch circuit is connected to the Op-Amp-non-inverting comparator circuit vide a Resistor R19. In particular, the transistorised switch circuit for driving capacitor C2 optionally along with a capacitor C9 includes a transistor Q4 including an emitter terminal, a base terminal, and a collector terminal; the base terminal being configured to receive an output from the Op-Amp based non-inverting comparator circuit; a diode D4 connected between the emitter and the collector terminals; with negative terminals of capacitors C9 and C2 being electrically parallel to each other and being connected to the location 14; positive terminal of Capacitor C2 being connected to an electrical path between the emitter terminal of the transistor Q4 and the diode D4; the collector terminal of the transistor Q4 being connected to the location 13 and a positive terminal of the Capacitor Q9 being connected to the collector terminal of the transistor Q4.
In full load mode, consider lamp ON situation, the voltage at location 15 will be higher than the voltage at location 16 which makes output at location 17 is high and results in transistor Q4 going to a saturation state. Q4 allows the flow of current through Capacitor C2. It looks resultant capacitance = C2+C9, which increases charging and discharging time.
In lamp failure mode, the voltage at location 15 will be always lower than the voltage at location 16 which makes output at location 17 is low and results in transistor Q4 in the cut¬off state. Q4 resist the flow of current through Capacitor C2. Only C9 comes in picture results less charging and discharging time.
Referring to Figure 8, there is further illustrated a detailed circuit diagram of the over-current protection block (10). In case, the location 11L is short-circuited with the location 12, very high current flows through switch Q3 which may damage flasher device or wire harness or melting of the fuse may occur. To avoid this harmful situation, overcurrent protection block (10) is applied to the circuit. The overcurrent protection block comprises SCR SI, Resistor R17 and R20 and Capacitor connected in a manner as shown in Figure 8. In particular, the overcurrent protection block comprises an SCR SI including an anode terminal, a gate terminal, and a cathode terminal, with the anode terminal being connected at a location between the Resistors R21 and R22; the cathode terminal being connected to the common point to which the load is connected; and the gate terminal being connected to the current

sensing element (7) and more particularly between the MOSFET switch Q3 and the Resistor R7. The gate terminal is connected between the MOSFET switch Q3 and the Resistor R7 via a first electrical path which includes a Resistor R20. A parallel combination of Resistor R17 and a Capacitor C7 is further connected between the first electrical path and the common point to which the load is connected.
When short circuit situation happens, current starts rising drastically, at a certain value of current (shut down current), SCR SI goes into the latched mode and voltage at location 18 equals to the forward on-state voltage of SI. Forward on state voltage of SI is very less in value which keeps the MOSFET switch Q3 is in off state. Value of shut down current will be less than the rated drain current of the MOSFET switch Q3.
Referring to Figure 9, there is illustrated a circuit diagram of the discrete flasher unit (100) which may be obtained by joining each of the individual circuits as described above with reference to Figures 2 to 8.
Referring to Figure 10 (a) to 10(d), there is illustrated the waveforms as produced at different locations of the discrete flasher unit (100) under different operating conditions. In particular, Figure 10(a) illustrates a first waveform produced at location 14 with reference to location 11L under full load condition. Based on the first waveform thus produced, a second waveform as shown in Figure 10(b) is produced at location 11L with reference to location 12 under full load condition in accordance with an embodiment of the present invention. On the other hand, Figure 10(c) illustrates a third waveform produced at location 14 with reference to location 11L under load failure condition and Figure 10(d) illustrates a second waveform as produced at location 11L with reference to location 12 based on the third waveform under load failure condition in accordance with an embodiment of the present invention. Comparing the first and the third waveforms, it can be seen that the first waveform has a smaller frequency of repetition compared to the third waveform (although both the first and the third waveforms are not exactly of square nature). On another hand, comparing the second and the fourth waveforms, it can be seen that the second waveform has a smaller frequency of repetition compared to the fourth waveform and that both the second and the fourth waveforms are of square nature. On a comparison of Figures 10 (a) and 10(b) or alternatively on a comparison of Figures 10(c) and 10(d), it can be furthermore observed that the discrete flasher unit has very less flashing operation starting time (i.e. the time taken for the flasher to start operating from the time of switching of the turn indicator switch is very less).

While the discrete flasher unit has been described in detail above, some of the advantages of the discrete flasher unit are listed below:
• Two terminal device
• Contactless operation
• Automatic load failure indication
• Wide range of operating voltage
• Low dropout voltage across the device
• Reverse voltage protection
• Overcurrent protection
• Very less Flashing operation starting time.
The drawings the foregoing descriptions give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of the process described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. In addition, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. The scope of embodiments is at least as broad as the following claims.
While certain embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied and practiced within the scope of the following claims.

WE CLAIMS.

1. A discrete flasher unit (100) for use in vehicles, the discrete flasher unit (100) being connectable to a battery (1) and a turn indicator switch (2) and a grounding point (12) and being adapted for controlling a plurality of flashing lamps (31, 3LR, 3LF, 3RR and 3RF), the discrete flasher unit (100) comprising:
a square wave oscillator circuit (5) configured to generate square wave signals;
a lamp load driver (6) operably connected between the battery (1) and the turn indicator switch (2), the lamp load driver being configured to receive the square wave signal from the square wave oscillator circuit (5) and a supply as provided by the battery (1) and generate a lamp load driving current;
a current sensing element (7) operably connected between the lamp load driver (6) and the turn indicator switch (2), the current sensing element (7) being configured to generate a current sense signal based on drop out voltage technique;
a signal conditioning unit (8) operably connected to the current sensing element (7), the signal conditioning unit (8) being configured to receive the current sense signal and produce an amplified current sense signal;
a flashing rate control block (9) configured to receive the amplified current sense signal, the flashing rate control block being further configured to produce a first flashing signal having a first frequency, if a value of the amplified current sense signal is below a first preset threshold limit or a second flashing signal having a second frequency, if the value of the amplified current sense signal is above the first preset threshold limit; the flashing rate control block being further configured to provide the first flashing signal or the second flashing signal to the square wave oscillator circuit (5) to control a frequency of the square wave signal thus generated;
an overcurrent protection block (10) configured to receive the current sense signal from the current sensing element (7), the overcurrent protection block (10) being further configured to keep the lamp load driver (6) in an OFF state if a value of the current sense signal is above a second preset threshold limit, the second preset threshold limit being higher than the first preset threshold limit.

The discrete flasher unit (100) as claimed in claim 1, further comprising a charge pump circuit (4) connected to the battery (1) the charge pump circuit being configured to act as a power source for the discrete flasher unit (100).
The discrete flasher unit (100) as claimed in claim 2, wherein the charge pump circuit (4) comprises a capacitor Cll connected to the battery (1) via a uni-directional current flow device Dl.
The discrete flasher unit (100) as claimed in claim 1, wherein the square wave oscillator circuit (5) comprises a transistor Q2 comprising a collector terminal, a base terminal and an emitter terminal; a collector terminal of the transistor Q2 being connected to a location 13; a series combination of Resistors R3, R21 and R22 being connected to the location 13; the emitter terminal of the transistor Q2 being connected to a common point to which a load is connected; the base terminal of the transistor Q2 being connected to a location 14 via a series combination of Resistors R4 and R5; a first terminal of a Capacitor C5 being coupled to the common point to which the load is connected and a second terminal of the capacitor C5 being connected to a location between the base terminal of the transistor Q2 and the resistor R4; a resistor R15 provided such that one end of the resistor R15 is connected to the common point to which the load is connected and another end of the resistor R15 is connected to a location between the base terminal of the transistor Q2 and the resistor R4 such that the Resistor R15 is electrically parallel to the capacitor C5; a capacitor C10 being connected between the base terminal of the transistor Q2 and the series combination of Resistors R3, R21 and R22; a Resistor Rl being connected in an electrical path between the series combination of Resistors R3, R21 and R22 and the Capacitor C10 and a location between the Resistor R4 and Resistor R5; a collector terminal of a transistor Ql being connected to about a location between the Resistor R4 and Resistor R5; an emitter terminal of the transistor Ql being connected to a common point to which the load is connected; a Capacitor C6 being connected between a base terminal of the transistor Ql and the common point to which the load is connected; a Resistor R16 being connected between a base terminal of the transistor Ql and the common point to which the load is connected, such that the Resistor R16 is electrically parallel to the Capacitor C6; a base terminal of the transistor Ql being

connected to location 14 via a Resistor R2; a capacitor CI being connected between the location 14 and the common point to which the load is connected.
The discrete flasher unit as claimed in claim 1, wherein the current sensing element (7) is a low resistance value, high wattage resistor (R7).
The discrete flasher unit as claimed in claim 1, wherein the lamp load driver circuit (6) comprises an N channel MOSFET switch Q3 with low on-state resistance, the MOSFET switch Q3 defining a source terminal, a drain terminal and a gate terminal; the source terminal of the MOSFET switch Q3 being connected through the current sensing element (7) to the common point to which the load is connected; the drain terminal of the MOSFET switch Q3 being connected to the Battery (1); the gate terminal of the MOSFET switch Q3 being connected via a first electrical path to a location between the diode Dl and the Capacitor CI 1; the first electrical path include a Zener diode Zl; the gate terminal of the MOSFET switch Q3 being further connected to the common point to which the load is connected via a second electrical path; the second electrical path including a Resistor R18; the gate terminal of the MOSFET switch Q3 being further connected to the common point to which the load is connected via a third electrical path; the third electrical path including a Resistor R6 and a Capacitor C8 connected in series; and the third electrical path being interconnected to the second electrical path.
The discrete flasher unit as claimed in claim 1, wherein the signal conditioning block incorporates an Op-Amp based non-inverting voltage amplifier with a predetermined gain.
The discrete flasher unit as claimed in claim 7, wherein the Op-Amp based non-inverting voltage amplifier includes a first non-inverting input terminal, a second inverting input terminal, an output terminal connected to the second inverting input terminal via a first electrical path, the first electrical path including a Resistor R9; the second inverting input terminal being connected to the common point to which the load via a second electrical path; the second electrical path including a Resistor R13; the first non-inverting input terminal being connected between the lamp load driver circuit and the current sensing element (7) via a third electrical path; the third electrical path including a Resistor R8; and the first non-inverting input terminal

being connected to the common point to which the load is connected via a fourth electrical path; the fourth electrical path including a Resistor R14.
The discrete flasher unit as claimed in claim 1, wherein the flashing rate control block (9) comprises an Op-Amp based non-inverting comparator circuit and a transistorized switch circuit for driving capacitor C2 optionally along with a capacitor C9, the Op-Amp based non-inverting comparator circuit being connected to the transistorized switch circuit via a Resistor R19.
The discrete flasher unit as claimed in claim 9, wherein the Op-Amp based non-inverting comparator circuit includes an Op-Amp-non-inverting comparator U2B including a first non-inverting input terminal, a second inverting input terminal and an output terminal; the first non-inverting input terminal being adapted to receive the amplified current sense signal as produced by the signal conditioning block (8); the second inverting input terminal is connected to the common point to which the load is connected via a second electrical path; the second electrical path including a Capacitor C4; the second inverting input terminal is connected to the common point to which the load is connected via a third electrical path; the third electrical path including a Resistor Rll, such that Resistor Rll and Capacitor C4 are electrically parallel to one another; the second inverting input terminal being further connected to the battery via a fourth electrical path; the fourth electrical path including a Resistor RIO; and a Capacitor C3 being provided in a fifth electrical path provided between the battery and the common point to which the load is connected.
The discrete flasher unit as claimed in claim 9, wherein the transistorised switch circuit for driving capacitor C2 optionally along with a capacitor C9 includes a transistor Q4 including an emitter terminal, a base terminal and a collector terminal; the base terminal being configured to receive an output from the Op-Amp based non-inverting comparator circuit; a diode D4 connected between the emitter and the collector terminals; with negative terminals of capacitors C9 and C2 being electrically parallel to each other and being connected to the location 14; positive terminal of Capacitor C2 being connected to an electrical path between the emitter terminal of the transistor Q4 and the diode D4; the collector terminal of the transistor Q4 being

connected to the location 13 and a positive terminal of the Capacitor Q9 being connected to the collector terminal of the transistor Q4.
12. The discrete flasher unit as claimed in claim 1, wherein the over current protection block (10) comprises: an SCR SI including an anode terminal, a gate terminal, and a cathode terminal, with the anode terminal being connected at a location between the Resistors R21 and R22; the cathode terminal being connected to the common point to which the load is connected; and the gate terminal being connected to the current sensing element (7) and more particular between the MOSFET switch Q3 and the Resistor R7; the gate terminal being connected between the MOSFET switch Q3 and the Resistor R7 via a first electrical path which includes a Resistor R20; and a parallel combination of Resistor R17 and a Capacitor C7 being connected between the first electrical path and the common point to which the load is connected.