FIELD OF THE INVENTION:
[001] The invention in general relates to a battery charging power management system and
in particularly relates to a battery charging control system and a method for maintaining a constant
current charging 5 in the battery.
BACKGROUND OF THE INVENTION:
[002] It is well known that in a typical battery charging system namely square wave or
10 quasi square wave Uninterrupted Power Supply (UPS) and Inverter system that deploys bi-directional
power conversion techniques to achieve battery charging and inverter functions. These systems
typically do not deploy a current sense element to achieve closed loop regulation of battery charging
current. Regulation of charging current across the line input voltage range for the system is achieved
with a constant frequency Pulse Width Modulation (PWM) technique. Major system variables that
15 determine the duty cycle are driven by the leakage inductance of the transformer, line input voltage,
turns ratio and Battery voltage/State of charge. These variables are commonly modeled into the
control system with experimental data at a given “optimal” operating point for the system.
[003] The charger is configured as a boost converter with leakage inductance of the
20 transformer used as the energy storage element. The RMS(Root Mean Square value) current flowing
into the transformer windings for a given average charging current into the battery depends upon the
duty cycle, the operating frequency and the operating mode of the converter. For a wide operating
input voltage range (for example between 120V and 290V AC RMS), sensor less control using such
duty cycle control can move operating modes of the converter between discontinuous conduction
25 mode (DCM) and continuous conduction mode (CCM). When the converter operates in CCM, peak
currents in the transformer windings resulting due to saturation of the leakage inductance can exceed
rated values for wire ampacity resulting in poor efficiency and loss of charger current regulation.
[004] Techniques that are commonly deployed to prevent this situation are to either change
30 the charging current across line input voltage/battery voltage such that the converter remains in DCM
throughout the line cycle or to disable charging for a specific duration across the line cycle in order to
maintain a constant average charging current. The former results in inconsistent charging times for the
battery, because of inconsistent charging currents, while the later results in poor reliability and
thermal performance since transformer RMS currents required during the line cycle period that
35 charging is enabled are higher. Alternately, the switching frequency can be increased to maintain
operation in DCM. All of the above situations have the disadvantage of poor overall system efficiency
across the operating input line voltage range. Moreover, the RMS component of the high frequency
3
AC current flowing into the battery is also significantly high and can result in reduced battery life.
Additional disadvantages of these schemes are limitations of scalability to higher battery charger
power and poor compatibility to generator and inverter input waveforms because computation of duty
cycle is based on an assumption that the input voltage to the system is sinusoidal. The advantage of
these control schemes is simplicity 5 in implementation.
[005] Oscilloscope captures of three independent exhibits designed for an average charging
current of 1A are used to demonstrate this effect and are presented in Figures.1A- 1C. It can be
observed that there is a large error between the intended (1A) & actual average current flowing into
10 the battery in all three exhibits. RMS current flowing into the transformer windings are also
significantly higher indicating poor efficiency and evidence of high frequency AC ripple current
flowing into the battery can also be seen.
OBJECT OF THE INVENTION:
15
[006] In accordance with the present invention, a novel and improved controlled method of
battery charging current is provided to achieve tighter regulation of the charging current over wide
operating input voltage ranges and across the battery voltages/ SoC (State of Charge) during
discontinuons conduction mode operation of the battery system.
20
[007] It is further object of the invention to enhance efficiency of charging to achieve faster
charging times.
[008] It is another object of invention to improve system efficiency by reducing transformer
25 RMS current & losses.
[009] It is an object of the invention to reduce High Frequency RMS current flowing into
the battery.
30 [0010] It is another object of the invention to achieve scalability for higher power charging
in the battery charging system.
[0011] It is further object of the invention to provide a controlled battery charging system
and method to retain performance advantages with generator and inverter input voltage waveforms.
35
4
[0012] It is object to provide the controlled charging method which can also be implemented
in UPS, Inverter and standalone charger systems to charge alternate battery chemistries like Li-Ion,
Li-Ion Polymer batteries.
SUMMARY 5 OF THE INVENTION:
[0013] The above listed advantages of the present invention is achieved in the present
invention by the feature of providing a battery charging power management system and a method that
may optimize the battery charging current during discontinuous conduction mode operation of the
10 battery driving unit by regulating/controlling the duty cycle D and the switching frequency Ts of the
battery driving unit based on the duty cycle D of the battery driving unit.
[0014] The present invention operates based on the principle of power balance. This is
illustrated below for a boost converter with DC input voltage and DC load current. This concept is
15 extended to the boost converter with rectified sinusoidal input.
[0015] The controlled method of battery charging as per the invention achieves the intended
operation by first calculating the duty cycle required at a given nominal switching frequency to
maintain the converter (battery driving unit) in DCM, while monitoring line and battery voltages. In
20 the event that the condition (derivation provided in the forthcoming description) for DCM is violated
by operating conditions like instantaneous input voltage or/and battery voltage the frequency of
operation is changed to meet the condition for DCM (derivation provided in the forthcoming
description) after the corresponding duty cycle value is computed. The switching frequency and the
duty cycle are thus both simultaneously modulated to maintain the converter in DCM while
25 maintaining a constant charging current. The novelty in the idea arises from the fact that the frequency
of operation and the resulting duty cycle are always maintained close to the critical conduction mode
and in close vicinity to the boundary of critical conduction mode so that transformer RMS currents are
at their lowest levels while still maintaining constant charging current into the battery. As a result the
ripple current is also optimized and the RMS value of the high frequency current into the battery is
30 reduced. Consistency of charging times across line voltage range and battery voltages and higher
system efficiencies are thus achieved. The battery charges at a faster rate as compared to the
conventional schemes while achieving higher efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS:
35
[0016] FIGS.1A-1C illustrates graphical representation of charging current waveforms for an
average charging current of 1A at 230V RMS value according to the conventional system;
5
[0017] FIG. 2 illustrates a general block diagram of a battery charging management system
that included in an electronic device according to an embodiment of the present invention;
[0018] FIG. 2A illustrates a block diagram of a battery charging 5 system employing
microprocessor instead of microcontroller for battery charging according to another embodiment of
the present invention;
[0019] FIG. 2B illustrates a block diagram of a battery charging system employing resistance
10 divide network in the input energy supply for measuring the input AC mains and also the battery unit
according to another embodiment of the present invention;
[0020] FIG. 3 illustrates a schematic electronic configuration of the battery charging system
according to an embodiment of the present invention;
15
[0021] FIG. 4A-4F illustrates the derivation and description of the control equation based on
the circuit and graph diagram in accordance with the method of controlled charging in the battery
system in the present invention;
20 [0022] Fig.5 illustrates a flow process for modulating the switching frequency and the duty
cycle while maintaining constant charging current according to an embodiment of the present
invention;
[0023] FIG. 6 illustrates a graphical representation of charging current regulation according
25 to an embodiment of the present invention which is compared with existing system; and
[0024] FIG. 7 illustrates a graphical representation of experimental results of the charger
waveform comparison showing better charging current regulation and efficiency according to an
embodiment of the present invention.
30
DETAILED DESCRIPTION OF INVENTION:
[0025] In the following description, the purpose, operation and the features of the invention
are explained in detail with reference to the drawings.
35
[0026] With reference to Fig.2, the general block diagram is provided to explain an
electronic system having a battery charging management system (201) which includes the electronic
6
components of an input energy supply unit (202), a control unit (203), a battery driving unit (204) and
a battery unit (205). The input energy supply unit comprises of an input sense main transformer with
an input signal processing stage and the Control unit is a microcontroller stage. The input sense mains
transformer converts the input AC mains voltage to low voltage by using a step down sense
transformer. The input signal processing stage is used for processing all input signals 5 like AC mains
and battery voltage for feeding to microcontroller for measurement. For example, the AC mains sense
signal is provided with a biasing voltage of 2.5 V so that the sense signal rides over this 2.5 V offset.
This is required to capture both the amplitude and polarity of signal because crest and trough both are
available to microcontroller for measurement. The battery driving unit is a Pulse Width Modulation
10 (PWM) driver stage following by a charging transformer. This PWM driver employs an H-bridge
convertor for battery charging and also for charging transformer. Further, battery voltage signal is
also processed to keep it within sensing range of the microcontroller. Further, the microcontroller
stage senses all the input signals, measures the input signals and processes the measured data. It also
drives the PWM signals as per the target current and the duty cycle. It is capable of handling different
15 fault condition and system protection also. The PWM driver stage drives a MOSFET according to the
signal from the microcontroller stage. This stage applies the digital TTL signal coming from
microcontroller to power section through the MOSFET. The drain of MOSFET is further connected to
a charging transformer. This is the power stage transformer to which Mains input is connected on high
voltage winding of transformer. At low voltage winding side the MOSFET Bridge is connected.
20 MOSFET are being driven through Microcontroller to get the desired charging current.
[0027] In the place of Microcontroller, the present invention may also incorporate a
microprocessor with separate peripherals connected to microprocessor like ADC, Memory, and PWM
etc. as shown in figure 2A. In input sensing and processing stage, the present invention may also
25 include resistance divider network for AC mains and battery voltage instead of input sense
transformer from AC mains sensing and OP amp from battery voltage sensing respectively as shown
in figure 2B.
[0028] The detailed component level schematic diagram of the charging section is as shown
30 in Figure 3.
[0029] The derivation and description of the control equation used in accordance with the
present invention are given below and these derivations are explained in detail based on the circuit
diagrams along with necessary graphs from figures 4A to figure 4F.
35
[0030] Assuming Pinput = Poutput; Operation is in Discontinuous conduction Mode (DCM) as
per the circuit in figure 4A and also the graph of the line current in figure 4B.
7
This implies Vin IL (avg) = VBatt IBatt 1
IL (avg) = Vin × D1 Ts × 1 (D1+ D2) Ts
L 5 2
Ts
= Vin D1
2 Ts + Vin D1 D2 Ts 2
2L 2L
10 Substituting equation 2 in equation 1
Vin
2 D1 Ts (D1+ D2) = VBatt IBatt 3
2L
Vin
2 15 = 2L 4
VBatt IBatt D1 Ts (D1+ D2)
Redrawing the Boost Converter circuit as in figure 4C and the diode current is as shown
in figure 4D.
20 ID (avg) = IBatt 5
ID (avg) = 1 × Vin D1 Ts × D2 Ts
2 L 6
Ts
Substituting equation 6 in equation 5,
25 Vin D1 D2 Ts = IBatt 7
2L
D2 = 2L IBatt 8
Vin D1 Ts
30 Substituting equation 8 in equation 4,
Vin
2 = 2L 9
VBatt IBatt D1 Ts D1 + 2L IBatt
Vin D1 Ts
35
8
10
In this 5 case in Figure 4E,
IBatt should be mean of rectified sinusoidal since the input voltage is sinusoidal.
IBatt = 2 Im 11

i(t) = Im sinwt
10 = IBatt sinwt 12
2
Therefore the control equation D1 becomes
D1 = 2L VBatt x IBatt sinwt 2L IBatt sinwt
2 2 13
Vin
2 Ts Vin
15 Ts
Ensuring the DCM Operation:
20 [0031] It is very important that DCM operation is maintained. Otherwise, it would lead to the
saturation of the leakage inductance of the transformer. The following check condition is
implemented in the algorithm to ensure this.
Assuming Critical Mode condition.
25 [0032] In Figure 4F, the transformer current for Critical mode condition is given for
maintaining in DCM,
I Transformer (avg) < I 14
2
I Transformer (avg) = IBatt 15
30 (1-D)
I = Vin X DTS 16
2 L 2
Substituting equations 15, 16 in 14
IBatt < Vin X DTS 17
35 (1-D) L 2
Therefore at every instant this condition should be satisfied.
D1 = 2L VBatt IBatt – 2L IBatt
Vin
2 Ts Vin Ts
9
i(t) < Vin (t) DTs 18
(1-D) 2L
D(1-D) > 2L IBatt sinwt
2 15 9
Vin (t) . Ts
Putting D (1-D) = Kcritical
Kcritical > 2L IBatt sinwt
10 2 20
Vm (t). Ts
At every instant calculate Kcritical with the D1 got from equation 13 and check with
2L IBatt sinwt
2
15 Vm (t). Ts
If the condition is not satisfied recalculate Ts such that
Ts = 2L IBatt sinwt
2 21
Vin (t) D1 (1-D1)
20
[0033] Recalculate D1 with new value of Ts and check for condition 20 again. If the
condition is satisfied the duty at the instant is the same as calculated. Otherwise follow the same
procedure till the cheek is satisfied.
25 [0034] The duty cycle for charger PWM is calculated at every tick time of the system
considering instantaneous value of the input voltage and the battery voltage averaged over a line
cycle.
[0035] Equation 13 gives us the duty at every input sample.
30
To reduce computation complexity, the above equation is simplified as below:
D1 = [1/Vin] * [SQRT( (2*L*(pi/2)*IBattSin(wt))/Ts) * (VBatt - Vin) )]
10
[0036] Computation of the above equation is further speeded up by a sine look up table for a
given average battery charging current (1.2A in this implementation). Calculation of duty cycle at the
cusp of the input sinusoid per the above equation tends to its maximum value. This can result in
current spikes in the region. In order to avoid this discontinuity in the discrete space, duty cycle is
fixed to a constant value until the instantaneous input voltage is at a fixed threshold 5 (75V in this
implementation).
[0037] The condition for critical conduction mode is then checked using equation. If the
calculated duty does not satisfy the condition in equation-18, the charger operating frequency is re10
calculated and applied.
[0038] With reference to figure 5, the method of battery charging in a battery power
15 management system (201) is now explained in detail in accordance to another aspect of the present
invention. In this aspect, the battery charging method for a power management system (201) is
provided with an input energy supply unit (202), control unit (203), a battery driving unit (204), and a
battery unit (205). This control unit is integrated with a charging controlling mechanism which cooperates
in function with the other components and achieves constant charging current in the battery
by controlling both the duty cycle D and the predefined switching operating frequency Ts 20
instantaneously of the battery driving unit. This control action is performed by generating a control
signal for driving the battery driving unit based on the determined duty cycle D. Furthermore, this
controlling action of duty cycle D and the switching operating frequency Ts of the battery driving unit
occurs during the switching operation of battery driving unit between a discontinuous conduction
25 mode and a continuous conduction mode. The control action is performed sequentially as follows as
per the aspect of the charging controlling mechanism in the present invention.
[0039] At first step 1, the charging operation for the battery unit (205) is started only on
checking step 2, whether there is the presence of input AC mains in the input energy supply unit
30 (202). Unless or otherwise the control unit (203) performs the step 3 of inverter mode operation in the
absence of the input AC mains. Subsequently followed by step 4 for defining a battery charging
current IBatt and a switching operating frequency Ts for the battery driving unit (204) with respect to
the charging requirement of the battery unit(205). The duty cycle D is determined in step 5 by
periodically calculating (5) the average battery voltage VBatt and the input AC supply mains Vin over a
35 single input cycle t. This computation is done by monitoring/measuring continuously the
11
instantaneous value of the input line voltage VL of the input main AC supply and voltage VBatt of the
battery. In step 6, if the measured value of input AC supply mains Vin is within a predefined range
limits between Vin (min) and Vin(max), it is consequently followed by step 7 for checking of measured
value of battery voltage VBatt. Otherwise, the assigning step of 7 is performed, wherein Vin(max) is
assigned to the input AC supply mains Vin if the measured Vin is greater than Vin(max). 5 And assigning
Vin(min) to the input AC supply mains Vin if the measured Vin is less than Vin(min).
[0040] If in step 8, the battery voltage is not in prescribed voltage limits, then the assigning
step of 9 is performed, wherein VBatt (max) to the battery voltage VBatt if the measured battery voltage
10 VBatt is greater than VBatt (max). And assigning VBatt (min) to the battery voltage VBatt if the measured
battery voltage VBatt is less than VBatt (min).
[0041] Subsequent to step of 8, duty cycle D is calculated in step 10 based on the measured
average battery voltage VBatt and the input AC supply mains Vin using the below formula.
15
D = [1/Vin] * [SQRT( (2*L*(pi/2)*IBattSin(wt))/Ts) * (VBatt - Vin) )]
[0042] This step 10 is sequentially followed by checking (12) whether the determined duty
cycle D satisfies a critical conduction mode condition that given below for achieving a stable state of
20 charging (SOC) operation.
i(t) < Vm (t) DTs 18
(1-D) 2L
[0043] If determined duty cycle D does not satisfy the predefined critical conduction mode
condition, it is followed consecutively by step 11 of determining the switching operating frequency Ts 25
of the battery driving unit and it is calculated using the below formula.
Ts = 2L IBatt Sinwt
2 21
30 Vin (t) D (1-D)
[0044] And the step 11 is followed by step of 10 for determining the duty cycle D1 of the
battery driving unit based on the determined switching operating frequency Ts of the battery driving
and are repeated by calculating the switching operating frequency Ts of the battery driving unit until
35 the determined duty cycle D satisfies the predefined critical conduction mode condition. When the
determined duty cycle D satisfies the predefined critical conduction mode condition, it is successively
followed by step 13 for controlled charging operation of the battery unit by applying (13) the
12
generated control signal for driving the battery driving unit to provide the constant current charging in
the battery based on the predetermined duty cycle D. And as finally, this charging operation is
continued by monitoring the presence of input AC mains in the input energy supply unit. It will be
discontinued and is converted to inverter mode operation in the absence of input energy supply unit.
5
[0045] As illustrated in detail, the flow chart fig. 5 provides the aspect of controlled charging
operation in the present invention and takes place during the discontinuous conduction mode of the
battery driving unit when there is a fluctuation in the operating input voltage range.
10 [0046] Results of the technique implemented in a charger rated to deliver 1.2A of average
charging current into a 12V battery over an operating input voltage range of 140V to 290V are shown
in figure 6. Results are also compared with existing system to provide evidence of issues resolved.
[0047] Results of the present invention shown in Figure 7 by which the charger waveforms
15 which shall be compared with exhibits used for comparison of charging regulation and efficiency in
the prior art system. Thus it is clearly evident that there is an improvement of 90% in charger current
regulation in the battery unit.
[0048] The result of implementing this control scheme in battery control management system
20 is shown. Charging time response with respect to input voltage variation is the main test that can be
deployed to detect implementation of this control scheme or its variants. Charging the battery
consistently within a given time duration (3 hours) to at least 90% of its capacity over a wide
operating range can be achieved by implementing a control scheme that can address system variables
and module operating conditions in accordance with the existing control mechanism. Charging current
25 waveform with respect to mains can be seen to detect if the duty cycle is varying with instantaneous
value of voltage.
[0049] The solution can be simplified to fit into a microcontroller with reduced resources to
carry out a simple triangular modulation of the switching frequency while still assuming a sinusoidal
30 input voltage waveform. If the start and the end frequencies of the triangular modulation technique are
optimized experimentally, the efficiency of the charger can be improved slightly over existing
techniques. This modulation technique also provides a certain degree of immunity to distorted voltage
inputs like in the case of generator compatibility even though reacting to instantaneous voltages is the
best response and most efficient manner to obtain regulation and efficiency.
35
[0050] The solution suggested by the present invention of battery charging power
management system and the method of constant current charging in the battery finds extensive
13
applications in the manufacture of UPS and (OR) inverter systems. In addition standalone charger
systems for battery charging can also be implemented by this solution because of the scalability for
higher power charging. Hybrid chargers implementing battery charging (with or without MPPT
control) using power available from the both the grid and the solar panel in order to optimize the
power drawn from the line while charging can also implement this solution to 5 gain charging time
advantage.
[0051] Thus the solution of the present invention is not limited to UPS and finds many
applications. This novel method could be employed for even small chargers for mobiles and laptops.
10 They can also be used to charge batteries other than SMF Pb-Acid chemistries, like Li-Ion and Li-Ion
Polymer batteries. The solution can be implemented in all applications where constant current battery
charging over a wide input voltage range is required without using a current sense element to sense
battery current and indirect means to arrive at battery SoC are deployed.
15 [0052] It is to be understood that the description and the claims are not limited to the specific
configuration and components illustrated above. Various modifications, changes and variations may
be made in the arrangement, operation and details of the method and system described above without
departing from the scope of the claims.

WE CLAIM:
1. A battery charging method for a power management system (201) having an input energy
supply unit (202), control unit (203), a battery driving unit (204), and a battery unit (205) comprising
the steps of:
- starting (1) the charging operation for the battery unit;
- defining a battery charging current IBatt and a switching operating frequency Ts for the
battery driving unit with respect to the charging requirement of the battery unit;
- determining (10) a duty cycle D for the predefined switching operating frequency Ts of the
battery driving unit; and
- controlling (13) both the duty cycle D and the predefined switching operating frequency Ts
instantaneously by generating a control signal for driving the battery driving unit based on the
determined duty cycle D, wherein said controlling of duty cycle D and the switching operating
frequency Ts of the battery driving unit occurs during the switching operation of battery driving unit
between a discontinuous conduction mode and a continuous conduction mode and thereby providing a
constant current charging in the battery unit.
2. The method as claimed in claim 1, said charging operation(1) is performed only in the
presence of input AC mains in the input energy supply unit otherwise performs inverter operation in
the absence of the input AC mains.
3. The method as claimed in claim 1, wherein said duty cycle D is determined by periodically
calculating (5) the average battery voltage VBatt and the input AC supply mains Vin over a single input
cycle t.
4. The method as claimed in claim 1 and 3, comprising monitoring continuously the
instantaneous value of the input line voltage VL of the input main AC supply and voltage VBatt of the
battery.
5. The method as claimed in claim 3, wherein said determining of duty cycle D comprising
determining (6) if the measured value of input AC supply mains Vin is within a predefined range
limits between Vin (min) and Vin(max).
6. The method as claimed in claim 5, wherein said determining of duty cycle D comprising
assigning (7) Vin(max) to the input AC supply mains Vin if the measured Vin is greater than Vin(max)
and assigning (7) Vin(min) to the input AC supply mains Vin if the measured Vin is less than Vin(min).
15
7. The method as claimed in claim 1 and 5, wherein said determining of duty cycle D
comprising determining (8) if the measured value of battery voltage VBatt is within a predefined range
limits between VBatt (min) and VBatt (max).
8. The method as claimed in claim 1 and 7, wherein said determining of duty cycle D
comprising assigning (9) VBatt (max) to the battery voltage VBatt if the measured battery voltage VBatt
is greater than VBatt (max) and assigning (9) VBatt (min) to the battery voltage VBatt if the measured
battery voltage VBatt is less than VBatt (min).
9. The method as claimed in claim 1, wherein said determining step (10) of duty cycle D is
calculated based on the measured average battery voltage VBatt and the input AC supply mains Vin
using the below formula.
D = [1/Vin] * [SQRT( (2*L*(pi/2)*IBattSin(wt))/Ts) * (VBatt - Vin) )]
10. The method as claimed in claim 1 and 9, wherein said step of calculating the duty cycle D is
sequentially followed by checking (12) whether the determined duty cycle D satisfies a critical
conduction mode condition.
11. The method as claimed in claim 10, wherein said critical conduction mode condition is a
predefined condition for a stable state of charging (SOC) operation.
12. The method as claimed in claim 10, wherein said critical conduction mode condition is
determined based on the predetermined D duty cycle, input supply means Vin and leakage inductance
L of a transformer connected in the output of the battery driving unit and this critical condition is
given below.
i(t) < Vm (t) DTs
(1-D) 2L
13. The method as claimed in claim 1 and 10, wherein if said determined duty cycle D does not
satisfy the predefined critical conduction mode condition, it is followed consecutively by determining
(11) step of the switching operating frequency Ts of the battery driving unit.
14. The method as claimed in claim 13, wherein said switching operating frequency Ts of the
battery driving is determined based on the determined duty cycle D, battery charging current IBatt,
input supply means Vin and leakage inductance L in the output of the Battery driving and said
operating switching frequency Ts of the battery driving is calculated using the below formula.
16
Ts = 2L IBatt Sinwt
2
Vin (t) D (1-D)
15. The method as claimed in claim 13, wherein said determined switching operating frequency
Ts of the battery driving unit is followed successively by the step of determining (10) the duty cycle D
of the battery driving unit.
16. The method as claimed in claim 12 to 15, wherein said steps (10) to (12) are repeated by
calculating the switching operating frequency Ts of the battery driving unit based on the
predetermined duty cycle D of the battery driving unit, until the determined duty cycle D satisfies the
predefined critical conduction mode condition.
17. The method as claimed in claim 1 and 7 to 14, wherein when said determined duty cycle D
satisfies the predefined critical conduction mode condition, it is successively followed by controlled
charging operation of the battery unit by applying (13) the generated control signal for driving the
battery driving unit to provide the constant current charging in the battery based on the predetermined
duty cycle D.
18. The method as claimed in claim 14, wherein said charging operation is continued by
monitoring the presence of input AC mains in the input energy supply unit.
19. The method as claimed in claim 14, wherein said charging operation is discontinued and is
converted to inverter mode operation in the absence of input energy supply unit.
20. The method as claimed in claim 14, wherein said controlled charging operation occurs during
the discontinuous conduction mode of the battery driving unit when there is a fluctuations in the
operating input voltage range.
21. A battery charging power management system (201) comprising:
an input energy supply unit(202) is operatively connected to a battery unit(205) through a
battery driving unit(204);
a control unit (203) is disposed between the input energy supply unit (202) and a battery
driving unit (204) and said control unit (203) includes a closed loop charging controlling mechanism
to provide constant current charging operation in the battery unit by controlling a switching operating
frequency Ts of the battery driving unit, wherein said charging operation is controlled instantaneously
17
based on a predetermined duty cycle D and the switching operating frequency Ts of the battery driving
unit (204).
22. The system as claimed in claim 21, wherein said input energy supply unit and said control
unit are interfaced by a input transformer sensing means and battery sensing means for receiving the
sensed signals of the input AC mains and a voltage of the battery unit.
23. The system as claimed in claim 21 and 22, wherein said input energy supply unit comprises at
least one resistance divider network connected to the AC input Mains and also the battery unit for
receiving the sensed signals of the input AC mains and a voltage of the battery unit.
24. The system as claimed in claim 21, wherein said control unit is a microcontroller connected
to the battery driving unit for processing the sensed signals of the input AC mains and the battery
voltage and generating a control signal for driving the battery driving unit.
25. The system as claimed in claim 21, wherein said control unit is a microprocessor coupled to a
memory and is configured to provided controlled operation of constant battery charging current based
on a predetermined duty cycle D and the switching operating frequency Ts of the battery driving unit
(204).
26. The system as claimed in claim 21, wherein said battery driving unit is a power converter
comprising a `H’ bridge circuit.
27. The system as claimed in claim 21, wherein said battery driving unit is a pulse Width
modulator (PWM) circuit.
28. The system as claimed in claim 21, wherein said control unit is adapted to provide constant
current charging operation over a wide operating input AC voltage ranging from 120 V and 280V.