Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.

Field of the invention:
[0001] The present invention relates to a synchronous dc-dc converter and a method for operating the same.

Background of the invention:
[0002] According to a patent literature WO2023117941, a controlling semiconductor switches of a voltage converter circuit arrangement is disclosed. The invention relates to a technique for controlling semiconductor switches of a circuit arrangement, in particular in the form of buck converters, boost/buck converters or flyback converters at a DC source or at an AC source, during a period comprising a fixed duration (ton) of a magnetising phase and a variable duration (toff) of a demagnetising phase of an inductor. The buck converter circuit arrangement comprises a first semiconductor switch that is conductive during the magnetising phase and a second semiconductor switch that is conductive during the demagnetising phase, the inductor, a capacitor parallel to an electrical load, and at least one current measuring point in the current path of one of the semiconductor switches. A current value is measured via the current measuring point at a fixed time point of the period and is compared with a fixed reference current value. The duration (toff) of the demagnetising phase is modified depending on the result of the comparison.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0004] Fig. 1 illustrates a synchronous DC-DC converter of a first type, according to an embodiment of the present invention;
[0005] Fig. 2 illustrates the synchronous DC-DC converter of a second type, according to an embodiment of the present invention, and
[0006] Fig. 3 illustrates a method for operating the synchronous DC-DC converter, according to the present invention.

Detailed description of the embodiments:
[0007] Fig. 1 illustrates a synchronous DC-DC converter of a first type, according to an embodiment of the present invention. The DC-DC converter 100 comprises, at least two semiconductor switches 106, 108, namely a first semiconductor switch 106 positioned between a first node 116 and a second node 118, and a second semiconductor switch 108 positioned between the second node 118 and a third node 122. An inductor 112 is positioned between the second node 118 and a fourth node 120, a capacitor 104 in parallel connection with a load 114, is positioned between the fourth node 120 and the third node 122, and an input source 102 and the parallel connection of the capacitor 104 and the load 114 connectable between the first node 116 and the third node 122, and the fourth node 120 and the third node 122 interchangeably, for usage as any one of a buck converter and boost converter, respectively. A controller 110 in communication with said at least two semiconductor switches 106, 108 to control the operation in critical conduction mode, characterized in that, the DC-DC converter 100 comprises current sensors 124, 126, 128, 132 positioned to measure current through each of the two semiconductor switches 106, 108, the inductor 112 and the capacitor 104, and the controller 110 configured to operate the two semiconductor switches 106, 108 in the critical conduction mode in dependence of the current measured by the current sensors 124, 126, 128, 132. Further, the capacitor 104 shown connected in dotted line is provided so that only load 114 and the input source 102 need to be interchanged to operate as buck or boost converter. In other words, the input source 102 can be applied in place of load 114 and the load 114 can be connected in place of the input source 102 to operate the same circuit as buck or boost converter.

[0008] According to the present invention, the controller 110 configured to measure an output voltage across the load 114 using a voltage sensor, compare the measured output voltage with a desired voltage, generate a reference inductor current using the measured voltage and the desired voltage as input to a proportional integral (PI) module. While the DC-DC converter 100 is operated as buck converter, the controller 110 configured to subtract the reference current from the sum of measured current through the capacitor 104 and the inductor 112, close the first semiconductor switch 106 if same measured inductor current is detected to be less than zero, and simultaneously apply combinational logic to operate the second semiconductor switch 108.

[0009] According to an embodiment of the present invention, a graph 140 is shown. In the graph 140, four plots are provided, a first plot 134 corresponds to current in capacitor 104, a second plot 136 corresponds to current in inductor 112, a third plot 138 corresponds to switching signal for second semiconductor switch 108 and a fourth plot 142 corresponds to switching signal for first semiconductor switch 106. The circuit parameter as an example is provided such as input voltage as 60V, Output voltage as 24V, power output is 120 watts, inductor is 50uH and capacitor is 200uF. The present invention enables operation of the DC-DC converter 100 on boundary condition at any load 114 under the range. The first plot 134 is shown to be varying between 5 Ampere to -5 Ampere with middle value as 0. The second plot 136 is shown to be varying between 10 Ampere and 0 ampere with 5 Ampere as the middle value. The third plot 138 and the fourth plot 142 are complimentary to each other, i.e. when the first semiconductor switch 106 is ON, the second semiconductor switch 108 is OFF, or when the first semiconductor switch 106 is OFF, the second semiconductor switch 108 is ON. Further, as can be seen, when the first semiconductor switch 106 is ON, then the inductor 112 charges and stores energy which is received from the input source 102 and when the second semiconductor switch 108 is ON and the first semiconductor switch 106 is OFF, the inductor 112 discharges along with the capacitor 104 and supplies current to the load 114.

[0010] The buck converter output voltage is a function of duty ratio and input voltage.
Vout = Duty ratio(D) * Vin
D = ton/T
Where ton is turn on time for semiconductor switch and T is Time period. So, this control scheme fixes the D by changing the ton and T for same output voltage. If the load 114 is changed, ton will reduce at that time T also be reduced.

[0011] In accordance to an embodiment of the present invention, a synchronous buck converter is provided in which case the capacitor 104 connected in dotted line may be or is omitted. This is directly used in devices, appliances, or equipment where the DC voltage is reduced for example loads 114 in electric and non-electric vehicle.

[0012] Fig. 2 illustrates the synchronous DC-DC converter of a second type, according to an embodiment of the present invention. The DC-DC converter 100 of the second type correspond to boost converter but usable as buck converter as well. In the boost converter, the position of the load 114 in parallel connection with the capacitor 104 and the input source 102 are interchanged. The operation of the controller 110 for the synchronous boost converter is explained. While the DC-DC converter 100 is operated as boost converter, the controller 110 configured to subtract the reference current from the sum of measured current through the capacitor 104 and the inductor 112, close the second semiconductor switch 108 if same measured inductor current is detected to be greater than zero, and simultaneously apply combinational logic to operate the first semiconductor switch 106.

[0013] According to the present invention, a second graph 210 is shown which comprises four plots. A fifth plot 202 corresponds to current through the capacitor 104. A sixth plot 204 corresponds to current through the inductor 112. A seventh plot 206 corresponds to switching signal for the second semiconductor switch 108. An eighth plot 208 corresponds to switching signal for the first semiconductor switch 106. Consider, as an example, the synchronous boost converter the circuit parameter are input voltage 24V, output voltage 60V, power output is 120 watts, inductor is 50uH and capacitor is 200uF, then a current of 2A is to be supplied to the load 114. At first the inductor 112 stores energy from the voltage supply when the first semiconductor switch 106 is ON and the second semiconductor switch 108. The voltage source supplies current to the inductor 112, the capacitor 104 and the load 114. When the current through the inductor 112 reaches 10 Ampere, the first semiconductor switch is turned OFF and the second semiconductor switch 108 is turned ON. The change in state of the switches causes the capacitor 104 to supply the load 114. When the current through the inductor 112 reaches zero, the state of the switches are changed again causing the inductor 112 to charge again along with the supplying the load 114. The current flow is known as state of the art.

[0014] In accordance to an embodiment of the present invention, a synchronous boost converter is provided in which case the capacitor 104 connected in dotted line may be or is omitted. This is directly used in devices, appliances, or equipment where the DC voltage is increased for example loads 114 in electric and non-electric vehicle.

[0015] According to an embodiment of the present invention, operated as any one of a buck converter, boost converter and a switch based buck/boost converter. The switch is operated automatically or manually.

[0016] According to the present invention, the synchronous DC-DC converter 100 is a type of bidirectional converter which is combination of synchronous converter and a unique control scheme. The synchronous DC-DC converter 100 has bidirectional property of DC-DC conversion and works in three modes, a Continuous Conduction Mode (CCM), a Discontinuous Conduction Mode (DCM), and the Boundary Conduction Mode (BCM). In CCM, there are two subintervals. In first interval, the first semiconductor switch 106 is on in buck converter while in boost converter second semiconductor switch 108 is turned ON. During this interval inductor 112 stores energy while in second Interval inductor 112 lose energy from complementary switch through load 114. In DCM, when inductor 112 value is less than critical inductance value, the gate pulse from both switches 106, 108 are removed just after inductor current become zero then this type of mode can be observed. The BCM is a just boundary of DCM-CCM. The discontinuity in waveform can create problem of Electromagnetic Interference (EMI), and not fully utilization of switches. The efficiency and switching point of view critical conduction mode (BCM) is very important.

[0017] In accordance to an embodiment of the present invention, the controller 110 is provided with necessary signal detection, acquisition, and processing circuits. The controller 110 is the one which comprises input interface, output interfaces having pins or ports, the memory element such as Random Access Memory (RAM) and/or Read Only Memory (ROM), Analog-to-Digital Converter (ADC) and a Digital-to-Analog Convertor (DAC), clocks, timers, counters and at least one processor (capable of implementing machine learning) connected with each other and to other components through communication bus channels. The memory element (not shown) is pre-stored with logics or instructions or programs or applications or modules/models and/or threshold values/ranges, reference values, predefined/predetermined criteria/conditions, lists, knowledge sources which is/are accessed by the at least one processor as per the defined routines. The internal components of the controller 110 are not explained for being state of the art, and the same must not be understood in a limiting manner. The controller 110 may also comprise communication units such as transceivers to communicate through wireless or wired means such as Global System for Mobile Communications (GSM), 3G, 4G, 5G, Wi-Fi, Bluetooth, Ethernet, serial networks, and the like. The controller 110 is implementable in the form of System-in-Package (SiP) or System-on-Chip (SOC) or any other known types. Examples of controller 110 comprises but not limited to, microcontroller, microprocessor, microcomputer, Electronic Control Units (ECUs), etc.

[0018] Further, the processor may be implemented as any or a combination of one or more microchips or integrated circuits interconnected using a parent board, hardwired logic, software stored in the memory element and executed by a microprocessor, firmware, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA). The processor is configured to exchange and manage the processing of various Artificial Intelligence (AI) modules.

[0019] Fig. 3 illustrates a method for operating the synchronous DC-DC converter, according to the present invention. The DC-DC converter 100 comprises, at least two semiconductor switches 106, 108, namely the first semiconductor switch 106 positioned between the first node 116 and the second node 118, and the second semiconductor switch 108 positioned between the second node 118 and the third node 122. The inductor 112 is positioned between the second node 118 and the fourth node 120, the capacitor 104 in parallel connection with the load 114, is positioned between the fourth node 120 and the third node 122, and the input source 102 and the load 114 connectable between the first node 116 and the third node 122, and the fourth node 120 and the third node 122 interchangeably, for usage as any one of the buck converter and the boost converter, respectively. The method is characterized by a step 302 which comprises controlling the at least two semiconductor switches 106, 108 to control the operation in critical conduction mode. The critical conduction mode is performed in dependence of current measured by the current sensors 124, 126, 128, 132. The method is defined for the buck converter, boost converter, and buck/boost converter as explained before.

[0020] A step 322 comprises measuring current flowing through each of the two semiconductor switches 106, 108, the inductor 112 and the capacitor 104. The method is executed or performed by the controller 110.

[0021] According to the present invention, for controlling the two semiconductor switches 106, 108, i.e. overall step 320, the method comprises plurality of steps of which a step 304 comprises measuring an output voltage across the load 114. A step 306 comprises comparing the measured output voltage with the desired voltage. A step 308 comprises generating the reference inductor current using the measured voltage and the desired voltage as input to the proportional integral (PI) module. A step 310 comprises subtracting the reference current from the sum of measured current through the capacitor 104 and the inductor 112. Further, while the DC-DC converter 100 is operated as buck converter, the method comprises, a step 312 comprising closing the first semiconductor switch 106 if same measured inductor current is detected to be less than zero, and a step 314 comprises simultaneously applying combinational logic to operate the second semiconductor switch 108.

[0022] Similarly, while the DC-DC converter 100 is operated as boost converter, the method comprises, a step 316 comprising closing the second semiconductor switch 108 if same measured inductor current is detected to be greater than zero, a step 318 comprises simultaneously applying combinational logic to operate the first semiconductor switch 106.

[0023] The method is operated as any one of the buck converter, the boost converter and the buck/boost converter based on a status of a switch. The switch is operated automatically or manually.

[0024] According to an embodiment of the present invention, the controller 110 and the method to achieve high efficiency by Boundary Conduction Mode (BCM) in a bidirectional synchronous Buck or Boost converter is provided. The BCM enables Zero Current Switching (ZCS), Zero Voltage Switching (ZVS) reduce size of inductor 112 and capacitor 104, losses are reduced, high efficiency is achieved for all kind of load current, and is less transient. Thus, the DC-DC converter 100 performs very efficiently at boundary conduction mode or in other word for critical inductance value using the present invention. The ZCS is achieved in upper/first semiconductor switch 106 while ZVS is achieved in the lower/second semiconductor switch 108. An example of the semiconductor switch is MosFET and not limited to the same. Also, only one PID is used to control voltage and current in DC-DC converter 100. In addition, robust operation is facilitated, i.e. by changing load 114, switching frequency is automatically adjusted to follow BCM principle.

[0025] It should be understood that the embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.
, Claims:We claim:
1. A synchronous DC-DC converter (100), said DC-DC converter (100) comprises,
at least two semiconductor switches (106, 108), namely a first semiconductor switch (106) positioned between a first node (116) and a second node (118), and a second semiconductor switch (108) positioned between said second node (118) and a third node (122);
an inductor (112) positioned between said second node (118) and a fourth node (120),
a capacitor (104) positioned across a load (114) between said first node (116) and said third node (122), said capacitor (104) in parallel connection with a load (114), and
an input source (102) and said load (114) connectable between said first node (116) and a third node (122), and said fourth node (120) and said third node (122) interchangeably, for usage as any one of a buck converter and boost converter, respectively, and
a controller (110) in communication with said at least two semiconductor switches (106, 108) to control the operation in critical conduction mode, characterized in that, said DC-DC converter (100) comprises current sensors (124, 126, 128, 132) positioned to measure current through each of said two semiconductor switches (106, 108), said inductor (112) and said capacitor (104), and
said controller (110) configured to operate said two semiconductor switches (106, 108) in said critical conduction mode in dependence of said current measured by said current sensors (124, 126, 128, 132).

2. The synchronous DC-DC converter (100) as claimed in claim 1, wherein said controller (110) configured to
measure an output voltage across said load (114);
compare said measured output voltage with a desired voltage;
generate a reference inductor current using said measured voltage and said desired voltage as input to a proportional integral (PI) module, and
while said DC-DC converter (100) is operated as buck converter, said controller (110) configured to
subtract said reference current from said sum of measured current through said capacitor (104) and said inductor (112);
close said first semiconductor switch (106) if same measured inductor current is detected to be less than zero, and
simultaneously apply combinational logic to operate said second semiconductor switch (108).
while said DC-DC converter (100) is operated as boost converter, said controller (110) configured to
subtract said reference current from said sum of measured current through said capacitor (104) and said inductor (112);
close said second semiconductor switch (108) if same measured inductor current is detected to be greater than zero, and
simultaneously apply combinational logic to operate said first semiconductor switch (106).

3. The synchronous DC-DC converter (100) as claimed in claim 1 is operated as any one of a buck converter, boost converter and a switch based buck/boost converter, wherein said switch is operated automatically or manually.

4. A method for operating a synchronous DC-DC converter (100), said DC-DC converter (100) comprises,
at least two semiconductor switches (106, 108), namely a first semiconductor switch (106) positioned between a first node (116) and a second node (118), and a second semiconductor switch (108) positioned between said second node (118) and a third node (122);
an inductor (112) positioned between said second node (118) and a fourth node (120),
a capacitor (104) positioned across a load (114) between said first node (116) and said third node (122), said capacitor (104) in parallel connection with a load (114), and
an input source (102) and said load (114) connectable between said first node (116) and a third node (122), and said fourth node (120) and said third node (122) interchangeably, for usage as any one of a buck converter and boost converter, respectively, and characterized by, said method comprising the steps of
controlling said at least two semiconductor switches (106, 108) to control the operation in critical conduction mode, wherein said critical conduction mode is performed in dependence of current measured by current sensors (124, 126, 128, 132).

5. The method as claimed in claim 4, wherein, said method comprises measuring current flowing through each of said two semiconductor switches (106, 108), said inductor (112) and said capacitor (104) before controlling said two semiconductor switches (106, 108).

6. The method as claimed in claim 4, wherein for controlling said two semiconductor switches (106, 108), said method comprises the steps of:
measuring an output voltage across said load (114);
comparing said measured output voltage with a desired voltage;
generating a reference inductor current using said measured voltage and said desired voltage as input to a proportional integral (PI) module, and
subtracting said reference current from said sum of measured current through said capacitor (104) and said inductor (112), and
while said DC-DC converter (100) is operated as buck converter, said method comprises,
closing said first semiconductor switch (106) if same measured inductor current is detected to be less than zero, and
simultaneously applying combinational logic to operate said second semiconductor switch (108).
while said DC-DC converter (100) is operated as boost converter, said method comprises,
closing said second semiconductor switch (108) if same measured inductor current is detected to be greater than zero, and
simultaneously apply combinational logic to operate said first semiconductor switch (106).

7. The method as claimed in claim 4 is operated as any one of a buck converter and boost converter based on a status of a switch, wherein said switch is operated automatically or manually.