FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A system and a method for providing a bypass mode operation in single phase AC-AC matrix converter for High Intensity Discharge (HID) lamps.
APPLICANTS
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worii, Mumbai - 400030, Maharashtra. India, an Indian Company.
INVENTORS
Chaudhary Mukesh Kumar, Rawat Chandan Singh, Hassan Hafiz Imtiaz, Saha Raja and Wachasundar Shripad of Crompton Greaves Limited, Global R&D, Electronic Design Centre (EDC). Aryabatta Building, Kanjur Marg (East), Mumbai - 400042, Maharashtra. India; all Indian Nationals.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to the field of electronics and electrical engineering.
Particularly, this invention relates to solid state devices for controlling or modifying power, specifically, for controlling or modifying AC power.
More particularly, this invention relates to a control mechanism for bypass feature in single phase matrix converter (AC-AC converter) without extra hardware for HID lamps.
Specifically, this invention relates to a system and a method for providing a bypass mode operation in single phase AC-AC matrix converter for High Intensity Discharge (HID) lamps.
BACKGROUND OF THE INVENTION
High Intensity Discharge (HID) lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between electrodes. For initialization, there is a need to strike an electrical arc across the electrodes. This arc, that needs to be struck, for initialization has to be of high voltage.
HID lamps, typically, are used in street light applications.
HID lamps require a surge of high voltage during start-up. High Intensity Discharge (HID) lamps require high voltage during start-up or initialization. Typically, this could be around 185V. Some of the lamps require slightly higher voltage around 200V or 210V depending on variation in lamp characteristics. The maximum output voltage available with switching converter is 190V.

Hence, in such conditions, there is a requirement of more voltage for start-up of the load and then it can be low after initial ignition of the lamp.
In high frequency AC-AC switching converter, normal operation at maximum duty cycle is 90%. It cannot go beyond 90% because of issue of dead-band as a result of which short circuit could take place. For some HID lamps, initial striking voltage required may be more than what is produced at 90%. In such cases, conventional operation of AC-AC converter with PWM duty cycle will not suffice for successful striking of lamps.
PRIOR ART
EP1819207 discloses an ignition method for a fluorescent lamp. It consists of a power controller which performs the task of adjusting current to higher value than the nominal value (normally available) to facilitate the starting up of the device (fluorescent lamp in this case). The system of this patent works on DC input and is a flyback converter. A flyback is used in AC-DC or DC-DC conversion and not used in AC-AC conversion.
US20110199016 discloses a controller device and corresponding method for modifying an AC input power to provide a reduced power AC output power to a load when coupled to the controller device. The AC output power has a series of cut-out pulses in half cycles of the AC output power waveform. The device includes a switching system having a plurality of switching elements for positioning the series of cut-out pulses in the half cycles of a waveform of the AC input power to result in said reduced power AC output power; and a switch control system for coordinating opening and closing of the plurality of switching elements during positioning of the series of cut-out pulses.

The drawback of the conventional operation of AC-AC converter is that there is no sufficient voltage for initial striking of HID lamps.
OBJECTS OF THE INVENTION
An object of the invention is to provide a control system and method for AC - AC converter such that sufficient voltage is provided, which sufficient voltage is greater than normal operation at maximum duty cycle in high frequency AC-AC switching converter.
Another object of the invention is to provide a control system and method for AC -AC converter which overcomes the limitations posed by conventional operation of AC-AC converter with PWM duty cycle.
Yet another object of the invention is to provide a control system and method for AC-AC converter which provides for relatively more voltage for start-up of a load.
Still another object of the invention is to provide a control system and method for AC-AC converter such that sufficient starting voltage is provided for striking or initialization of HID lamps.
An additional object of the invention is to provide a control system and method with a pre-defined sequence of switching of associated solid state devices in order to enter bypass mode for providing relatively higher voltage for a pre-defined time duration or for pre-defined periods of time durations.
Yet an additional object of the invention is to provide a control system and method with a pre-defined sequence of switching of associated solid state devices in order

to exit bypass mode for providing relatively higher voltage for a pre-defined time duration or for pre-defined periods of time durations.
SUMMARY OF THE INVENTION
According to this invention, there is provided a system and a method for providing a bypass mode operation in single phase AC-AC matrix converter, for providing high voltage to a load, said system comprises:
a. at least a first set of solid state devices in series with each other and
cumulatively, in parallel to said load;
b. at least a second set of solid state devices in parallel to each other and
independently, in series to said load;
c. at least a gating signal generator adapted to generate gating signals to switch
on or to switch off said solid state devices;
d. at least a first control mechanism adapted to provide logic for:
i. control of gating signal generator in order to provide gating signals in
accordance with a first sequence of a pre-determined pattern for entering
said bypass mode; and ii. control of gating signal generator in order to provide gating signals in
accordance with a second sequence of a pre-determined pattern for
exiting said bypass mode; and
e. at least a second control mechanism adapted to provide logic for control of
gating signals based on determination of pre-determined parameters relating
to voltage cycles,

Typically, said at least a second control mechanism comprises a processor in order to provide logic for control of gating signal generator in order to provide gating signals in order to perform the steps of: I. detecting zero cross on input voltage so that positive cycle of input voltage is
detected; IL generating and providing Pulse Width Modulated signal for a pre-defined time duration (typically, this time duration may be for 1ms);
III. starting bypass sequence in accordance with first control mechanism;
IV. disabling hardware protection; V. stopping bypass sequence; and
VI. enabling hardware protection in accordance with second control mechanism.
Typically wherein, said first set comprises a second solid state device and a fourth solid state device.
Typically, said first set comprises a second solid state device and a fourth solid state device, characterized, in that, said second solid state device is a second switch.
Typically, said first set comprises a second solid state device and a fourth solid state device, characterized, in that, said fourth solid state device is a fourth switch.
Typically, said second set comprises a first solid state device and a third" solid state
device.
Typically, said second set comprises a first solid state device and a third solid state
device, characterized, in that, said first solid state device is a first switch.
Typically, said second set comprises a first solid state device and a third solid state device, characterized, in that, said third solid state device is a third switch.

Typically wherein, said at least a first control mechanism adapted to provide logic for control of gating signal generator in order to provide gating signals in accordance with a first sequence of a pre-determined pattern for entering said bypass mode, characterized in that, said pattern comprises said steps wherein:
A. said first solid state device and said second solid state device being in Pulse
Width Modulated mode of operation and said third solid state device and said
fourth solid state device being ON upon detection of positive cycle of input
voltage, at a first instance of time;
B. said first solid state device and said second solid state device being OFF and
said third solid state device and said fourth solid state device being ON, at a
second instance of time;
C. said first solid state device, said third solid state device, said fourth solid state
device being ON and said second solid state device being OFF, at a third
instance of time; and
D. said first solid state device and said third solid state device being ON and said
second solid state device and said fourth solid state device being OFF, at a
fourth instance of time.
Typically, said at least a first control mechanism adapted to provide logic for control of gating signal generator in order to provide gating signals in accordance with a second sequence of a pre-determined pattern for exiting said bypass mode, characterized in that, said pattern comprises said steps wherein:
E. said first solid state device and said third solid state device being ON and said
second solid state device and said fourth solid state device being OFF, at a
first instance of time;
F. said first solid state device, said third solid state device, said fourth solid state
device being ON and said second solid state device being OFF, at a second
instance of time;

G. said first solid state device and said second solid state device being OFF and said third solid state device and said fourth solid state device being ON, at a third instance of time; and
H. said first solid state device and said second solid state device being in Pulse Width Modulated mode of operation and said third solid state device and said fourth solid state device being ON upon detection of positive cycle of input voltage, at a fourth instance of time.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic circuit diagram for the system for providing a bypass mode operation in single phase AC-AC matrix converter; and
Figure 2 illustrates a flow chart for bypass mode operation in single phase AC-AC
V
matrix converter.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to this invention, there is provided a system and a method for providing a bypass mode operation in single phase AC-AC matrix converter.
In at least one embodiment, the system comprises a microcontroller device and a method for providing a bypass mode operation in single phase AC-AC matrix converter. The bypass mode operation is for achieving high striking voltage for a load. The load, typically, may be HID lamps which require high striking voltage.

Figure 1 of the accompanying drawings illustrates a schematic circuit diagram for bypass mode operation for single phase AC-AC matrix converter. Typically, this could be for High Intensity Discharge (HID) lamps.
In accordance with an embodiment of this invention, there is provided a first set of solid state devices (S2, S4) in series with each other and cumulatively, in parallel to the load (L). This first set comprises a second Solid state device and a fourth solid state device. A second solid state device is a second switch (S2). A fourth solid state device is a fourth switch (S4).
In accordance with another embodiment of this invention, there is provided a second set of solid state devices (SI, S3) in parallel to each other and independently, in series to the load (L). This second set comprises a first solid state device and a third solid state device. A first solid state device is a first switch (SI). A third solid state device is a third switch (S3).
In accordance with yet another embodiment of this invention, there is provided a gating signal generator adapted to generate gating signals to switch on or to switch off the solid state devices. The gating signal generator is adapted to generate gating signals based on predefined patterns. These pre-defined patterns are defined by logic embedded in control mechanisms.
In accordance with still another embodiment of this invention, there is provided a
first control mechanism adapted to provide logic for:
a) control of gating signal generator in order to provide gating signals in accordance with a first sequence of a pre-determined pattern for entering a bypass mode operation in single phase AC-AC matrix converter; and

b) control of gating signal generator in order to provide gating signals in accordance with a second sequence of a pre-determined pattern for exiting a bypass mode operation in single phase AC-AC matrix converter.
The gating signals for each of the first switch (SI), second switch (S2), third switch (S3), and fourth switch (S4) are generated from the control mechanism using digital signal processing techniques. The gating signals for SI, S2, S3, and S4 are generated using digital signal processing techniques through gate driver card(s) in order to target individual switches.
Figure 2 of the accompanying drawings illustrates a flow chart for bypass mode operation of this invention.
In accordance with an additional embodiment of this invention, there is provided a second control mechanism comprising a processor in order to provide a logic for control of gating signal generator in order to provide gating signals in order to perform the steps of: I. detecting zero cross on input voltage so that positive cycle of input voltage is
detected; II. generating and providing Pulse Width Modulated signal for a pre-defined time duration (typically, this time duration may be for 1ms);
III. starting bypass sequence in accordance with first control mechanism;
IV. disabling hardware protection; V. stopping bypass sequence;
VI. enabling hardware protection in accordance with second control mechanism;
and VII. continuing normal Pulse Width Modulated Cycle.

Typically, the bypass mode operation starts in a positive cycle of the input voltage and passes through a sequence before entering the bypass mode operation. The sequence is adapted to take care of any short circuit of current interruption which gives rise to voltage spike(s) across the solid state devices / load or large current through the solid state devices / load.
Table 1, below, illustrates a typical pre-defined sequence for entering the Bypass mode from positive cycle of the input voltage.

+ve cycle -PWM
operation T2 (time in T3 (time in Bypass Mode
Tl (time in ms) us) us) T4 (time in us)
SI PWM OFF ON ON
S2 PWM OFF OFF OFF
S3 ON ON ON ON
S4 ON ON ON OFF
In this mode of entering the bypass mode, the first switch and third switch are enabled i.e. switched ON, so that AC source is directly applied to the load for striking / re-striking / initialization without a short circuit and are disables i.e. switched OFF when the load is striked / re-striked / initialized. After the load is initialized, the system switches back'to normal Pulse Width Modulated operation from the bypass mode of operation.
In these steps of entering the bypass mode of operation, the following steps are pre-decided and need to be followed:
1) SI and S2 is in Pulse Width Modulated mode of operation and S3 and S4 is ON - upon detection of positive cycle of input voltage, at time = Tims

2) S1 and S2 is OFF and S3 and S4 is ON - at time = T2ms
3) S1, S3, and S4 is ON and S2 is OFF - at time = T3ms
4) S1 and S3 is ON and S2 and S4 is OFF - at time = T4ms
With Pulse Width Modulated converter operation, duty cycle limit is 90% and with it sometimes load may not strike / re-strike / initialize and hence may not switch ON. Once the load is successfully struck / re-struck / initialized, it does not require high voltage. Hence, for providing initial striking / re-striking / initializing voltage, there is a need to operate AC-AC converter in bypass mode, thereby connecting source directly to load through first solid state device (S1) and third solid state device (S3). After load is struck / re-struck / initialised, the AC-AC converted is to be switched back in normal Pulse Width Modulated operation.
Table 2, below, illustrates a typical pre-defined sequence for exiting the Bypass mode from positive cycle of the input voltage.

T4 (time in us)
+ve cycle = PWM operation (continues till
T2 (time in T3 (time in next bypass
Bypass Mode us) us) requirement)
SI ON ON OFF PWM
S2 OFF OFF OFF PWM
S3 ON ON ON ON
S4 OFF ON ON ON
In these steps of exiting the bypass mode of operation, the following steps are pre-decided and need to be followed:

1) S1 and S3 is ON and S2 and S4 is OFF - at time = Tims
2) S1, S3, and S4 is ON and S2 is OFF - at time = T2ms
3) S1 and S2 is OFF and S3 and S4 is ON - at time = T3ms
4) S1 and S2 is in Pulse Width Modulated mode of operation and S3 and S4 is ON - upon detection of positive cycle of input voltage, at time = T4ms.
The technical advancement of this invention lies in providing an bypass mode operation in single phase AC-AC matrix converter for initial striking / re-striking / initialization for loads (such as HID lamps). This is enabled by a system and a method provides a sequence pattern for a defined circuit in order to enter bypass mode as well as to exit bypass mode in correlation with voltage cycles. The use of this system and method eliminates the need of extra switch / contactor for initial striking / re-striking / initialization in loads and also prevents short circuit and any current interruption during bypass mode. Therefore, extra hardware cost is saved and reliability is improved. Also, sequence is designed to prevent any short circuit (dead short in the circuit) and any current interruption during bypass mode (may produce voltage spike).
Typically, this system and method can be used for any starter mechanism where boosting of voltage is required.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1) A system and a method for providing a bypass mode operation in single
phase AC-AC matrix converter, for providing high voltage to a load, said
system comprising:
a. at least a first set of solid state devices in series with each other and
cumulatively, in parallel to said load;
b. at least a second set of solid state devices in parallel to each other and
independently, in series to said load;
c. at least a gating signal generator adapted to generate gating signals to
switch on or to switch off said solid state devices;
d. at least a first control mechanism adapted to provide logic for:
i. control of gating signal generator in order to provide gating signals in
accordance with a first sequence of a pre-determined pattern for
entering said bypass mode; and ii. control of gating signal generator in order to provide gating signals in
accordance with a second sequence of a pre-determined pattern for
exiting said bypass mode; and
e. at least a second control mechanism adapted to provide logic for control
of gating signals based on determination of pre-determined parameters
relating to voltage cycles.
2) The system and a method for providing a bypass mode operation jn single
phase AC-AC matrix converter as claimed in claim 1, wherein said at least a
second control mechanism comprising a processor in order to provide logic
for control of gating signal generator in order to provide gating signals in
order to perform the steps of:
I. detecting zero cross on input voltage so that positive cycle of input voltage is detected;

II. generating and providing Pulse Width Modulated signal for a predefined time duration (typically, this time duration may be for 1ms);
III. starting bypass sequence in accordance with first control mechanism;
IV. disabling hardware protection; V. stopping bypass sequence; and
VI. enabling hardware protection in accordance with second control mechanism.
3) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said first set comprising a second solid state device and a fourth solid state device.
4) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said first set comprising a second solid state device and a fourth solid state device, characterized, in that, said second solid state device is a second switch.
5) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said first set comprising a second solid state device and a fourth solid state device, characterized, in that, said fourth solid state device is a fourth switch.
6) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said second set comprising a first solid state device and a third solid state device.
7) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said second

set comprising a first solid state device and a third solid state device, characterized, in that, said first solid state device is a first switch.
8) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said second set comprising a first solid state device and a third solid state device, characterized, in that, said third solid state device is a third switch.
9) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1, wherein said at least a first control mechanism adapted to provide logic for control of gating signal generator in order to provide gating signals in accordance with a first sequence of a pre-determined pattern for entering said bypass mode, characterized in that, said pattern comprising said steps wherein:
A. said first solid state device and said second solid state device being in
Pulse Width Modulated mode of operation and said third solid state
device and said fourth solid state device being ON upon detection of
positive cycle of input voltage, at a first instance of time;
B. said first solid state device and said second solid state device being OFF
and said third solid state device and said fourth solid state device being
ON, at a second instance of time;
C. said first solid state device, said third solid state device, said fourth solid
state device being ON and said second solid state device being OFF, at a
third instance of time; and
D. said first solid state device and said third solid state device being ON and
said second solid state device and said fourth solid state device being
OFF, at a fourth instance of time.

10) The system and a method for providing a bypass mode operation in single phase AC-AC matrix converter as claimed in claim 1. wherein said at least a first control mechanism adapted to provide logic for control of gating signal generator in order to provide gating signals in accordance with a second sequence of a pre-determined pattern for exiting said bypass mode, characterized in that, said pattern comprising said steps wherein:
E. said first solid state device and said third solid state device being ON and
said second solid state device and said fourth solid state device being
OFF, at a first instance of time;
F. said first solid state device, said third solid state device, said fourth solid
state device being ON and said second solid state device being OFF, at a
second instance of time;
G. said first solid state device and said second solid state device being OFF
and said third solid state device and said fourth solid state device being
ON, at a third instance of time; and
H. said first solid state device and said second solid state device being in Pulse Width Modulated mode of operation and said third solid state device and said fourth solid state device being ON upon detection of positive cycle of input voltage, at a fourth instance of time.