GB2601751A - Buck-boost converter - Google Patents

Buck-boost converter Download PDF

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Publication number
GB2601751A
GB2601751A GB2019283.7A GB202019283A GB2601751A GB 2601751 A GB2601751 A GB 2601751A GB 202019283 A GB202019283 A GB 202019283A GB 2601751 A GB2601751 A GB 2601751A
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United Kingdom
Prior art keywords
switches
switch
inductor
terminal
configuration
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GB2019283.7A
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GB202019283D0 (en
Inventor
Greetham Stephen
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Dyson Technology Ltd
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Dyson Technology Ltd
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Priority to GB2019283.7A priority Critical patent/GB2601751A/en
Publication of GB202019283D0 publication Critical patent/GB202019283D0/en
Priority to PCT/GB2021/052952 priority patent/WO2022123202A1/en
Publication of GB2601751A publication Critical patent/GB2601751A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0095—Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • H03K2017/6878—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors using multi-gate field-effect transistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
    • H03K2217/0009—AC switches, i.e. delivering AC power to a load

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

Buck-boost converter 10 comprising: a first pair of switches 16 connecting each side of an AC supply 30 to a first terminal 25 of an inductor L1; a second pair of switches 17 connecting each side of the AC supply to the second terminal 26 of the inductor; and a third pair of switches 18 connecting each side of the AC supply to a second terminal 28 of a capacitor C1 which is connected across the output terminals 13, 14. Each first switch has an ON state, diode state and OFF state; and each second switch has an ON and OFF state. The first and second switches may be the same type of bidirectional switch. The converter may energise the inductor in a first mode and transfer said energy to the capacitor in a subsequent mode. In buck mode the switches may operate in a first configuration during the positive half-cycle of the AC supply (Fig. 2a) and in a second configuration in the negative half-cycle (Fig. 2b). In boost mode the switches may operate in a first configuration during the positive half-cycle of the AC supply (Fig. 3a) and in a second configuration in the negative half-cycle (Fig. 3b).

Description

BUCK-BOOST CONVERTER
Field of the Invention
The present invention relates to a buck-boost converter.
Background of the Invention
Buck-boost converters typically provide DC-to-DC conversion. Where AC-to-DC conversion is required, a front-end bridge rectifier and bulk capacitor are generally provided.
S ummary of the Invention The present invention provides a buck-boost converter comprising: first and second input terminals for connection to a power supply supplying an alternating input voltage; first and second output terminals for outputting an output voltage; a pair of first switches; a pair of second switches; a pair of third switches or diodes; an inductor having a first terminal and a second terminai; a capacitor having a first terminal and a second terminal; and a controller for controlling the switches, wherein: one of the first switches is connected between the first input terminal and the first terminal of the inductor, and the other of the first switches is connected between the second input terminal and the first terminal of the inductor; one of the second switches is connected between the first input terminal and the second terminal of the inductor, and the other of the second switches is connected between the second input terminal and the second terminal of the inductor; one of the third switches or diodes is connected between the first input terminal and the second terminal of the capacitor, and the other of the third switches or diodes is connected between the second input termina I arid the second terminal of the capacitor; the first terminal of the capacitor is connected to the second terminal of the inductor and to the first output terminal, and the second terminal of the capacitor is connected to the second output terminal; each of the first switches has an ON state in which the switch is conductive in at least a first direction, a diode state in which the switch is conductive in the first direction and is non-conductive in a second direction, and an OFF state in which the switch is non-conductive in both the first direction and the second direction; and each of the second switches has an ON state in which the switch is conductive in at least a first direction, and an OFF state in which the switch is non-conductive in both the first direction and a second direction.
The converter is therefore capable of providing AC-to-DC conversion without the need for a recdfier bridge or front-end bulk capacitor. Moreover, the converter is capable of providing AC-to-DC conversion using just six devices (ft. six switches, or four switches and two diodes), an inductor and a capacitor.
The first switches have an OFF state in which the switches are non-conductive in both directions. The switches can therefore be controlled such that the inductor is disconnected from the power supply, thereby enabling the converter to operate in buck mode.
The second switches have an OFF state in which the switches are non-conductive in both directions. The switches can therefore be controlled such that (i) current does notflow directly from the power supply to the capacitor when the insta ntaneous value of the input voltage is greater than the output voltage, and/or (ii) current does not flow from the capacitor to the power supply when the instantaneous value of the input voltage is less than the output voltage.
The controlier may configure the switches in a configuration in which the inductor is energised by the power supply, and a further configuration in which energy stored in the inductor is transferred to the capacitor. Moreover, the controller may switch between the configuration and the further configuration throughout each half-cycle of the input voltage.
The converter may have discreet buck and boost modes, with different configurations for each mode. The converter may then be used in buck mode only, boost mode only, or a combination of buck and boost modes.
In a buck mode, the controller may configure the switches in: a first configuration in which one of the first switches is ON, the other of the first switches is in the diode state, and both second switches are OFF; and a second configuration in which one of the first switches is OFF, the other of the first switches is in the diode state, and both second switches are OFF.
In a boost mode, the controller may configure the switches in: a first configuration in which one of the first switches and one of the second switches are ON, and the other of the first switches and the other of the second switches are OFF; and a second configuration in which one of the first switches is ON, the other of the first switches is OFF, and both second switches are OFF.
In each of the two modes, the inductor may be energised by the power supply in the first configuration, and energy stored in the inductor may be transferred to the capacitor in the second configuration.
The choice of switches that are ON or in diode state may be determined by the polarity of the input voltage. Accordingly, when in buck mode, one of the first switches is ON and the other of the first switches is in the diode state when the polarity of the input voltage is positive, and the other of the first switches is ON and the one of the first switches is in the diode state when the polarity of the inputvoltage is negative. And when in boost mode, one of the first switches and one of the second switches are ON when the polarity of the input voltage is positive, and the other of the first switches and the other of the second switches are ON when the polarity of the input voltage is negative.
With the topology of the converter, the inductor may be energised in the same direction irrespective of the polarity of the input voltage, Hysteresis losses may then be reduced (in comparison to a topology in which the inductor is energised in opposite directions).
Each of the first switches and each of the second switches may be conductive in both the first direction and the second direction when in the ON state. This then has the advantage that the converter may be used for bidirecfional power transfer, i.e. power may be transferred from the power supply to the capacitor (forward power transfer), and power may be transferred from the capacitor to the power supply (reverse power transfer).
The present invention further provides a buck-boost converter comprising: input terminals for connection to a power supply supplying an alternating input voltage; output terminals for outputting an ougput voltage; a pair of first switches, each of the first switches having an ON state in which the switch is conductive in at least a first direction, a diode state in which the switch is conductive in the first direction and is non-conductive in a second direction, and an OFF state in which the switch is non-conductive in both the first direction and the second direction; a pair of second switches, each of the second switches having an ON state in which the switch is conductive in at least a first direction, and an OFF state in which the switch is nonconductive in both the first direction and a second direction; a pair of third switches or diodes; an inductor connected between the first switches and the second switches; a capacitor; and a controller for controlling the switches, wherein: in a buck mode the controller configures the switches in: a first configuration in which one of the first switches is ON, the other of the first switches is in the diode state, and both second switches are OFF, thereby causing the inductor to be energised by the power supply; and a second configuration in which one of the first switches is OFF, the other of the first switches is in the diode state, and both second switches are OFF, thereby causing energy stored in the inductor to be transferred to the capacitor and in a boost mode the controller configures the switches in: a first configuration in which one of the first switches and one of the second switches are ON, and the other of the first switches and the other of the second switches are OFF, thereby causing the inductor to be energised by the power supply; and a second configuration in which one of the first switches is ON, the other of the first switches is OFF, and both second switches are OFF, thereby causing energy stored in the inductor to be transferred to the capacitor.
Brief Description of the Drawings
E mbodiments will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a buck-boost converter; Figure 2 illustrates configurations of the converter operating in buck mode when a polarity of an input voltage is positive; Figure 3 illustrates configurations of the converter operating in buck mode when the polarity of the input voltage is negative; Figure 4 illustrates configurations of the converter operating in boost mode when a polarity of an input voltage is positive; Figure 5 illustrates configurations of the converter operating in boost mode when the polarity of the input voltage is negative; and Figure 6 illustrates the states of the switches of the converter over a cycle of the input voltage; Figure 7 illustrates configurations of the converter for reverse power transfer when the polarity of the input voltage is positive; and Figure 8 illustrates alternative configurations of the converter for reverse power transfer when the polarity of the input voltage is positive.
Detailed Description of the Invention
The buck-boost converter 10 of Figure 1 comprises input terminals 11,12 for connection to a power supply 30 supplying an AC input voltage VIN, and output terminals 13,14 for outputting a DC output voltage V OUT. The converter 10 further comprises an input filter 15, a pair of first switches 16, a pair of second switches 17, a pair of third switches or diodes 18, an inductor L1, and capacitor C1, a gate driver 19 and a controller 20.
The input filter 15 comprises an inductor L2 and a capacitor Cl, and attenuates high-frequency ripple in the input current drawn from The power supply 30. Whilst the input filter 15 has particular benefits and may be required for regulatory compliance (e.g. harmonics), the input filter 15 is not required for AC-to-DC conversion and could conceivably be omitted.
The pair of first switches 16 comprises switches SW1 and SW2. Each of the first switches SW1,SW2 has four states ON, D1, D2, and OFF. When the state of the switch is ON, the switch is conductive in both a first direction and a second direction. When the state of the switch is D1, the switch is conductive in the first direction and non-conductive in the second direction. Conversely, when the state of the switch is D2, the switch is conductive in the second direction and non-conductive in the first direction. D1 and D2 may therefore be regarded as diode states. In the particular example shown in Figure 1, the first direction may be regarded as upward (i.e. D1 = upward conducting), and the second direction may be regarded as downward (i.e. D2 = downward conducting). Finally, when the state of the switch is OFF, the switch is non-conductive in both the first direction and the second direction.
Each of the first switches SW1,5W2 is connected between a respective input terminal 11,12 and a first terminal 25 of the inductor L1. Accordingly, one of the first switches SW1 is connected between the first input terminal 11 and the first terminal 25 of the inductor 1..1, and the other of the first svvitc.hes 5W2 is connected between the second input terminal 12 and the first terminal 25 of the inductor Li.
The pair of second switches 17 comprises switches SW3 and SW4. Each of the second switches SW3,SW4 has an ON state in which the switch is conductive in at least one of a first direction and a second direction, and an OFF state in which the switch is non-conductive in both the first direction and the second direction. In the particular example shown in Figure 1, each of the second switches SW3,SW4 conducts in at least a direction from right to left. In contrast to the first switches, the second switches are not required to have a diode state. Nevertheless, the second switches may be the same type of device as the first switches.
Each of the second switches SW3,SW4 is connected between a respective input terminai 11,12 and a second terminal 26 oldie inductor L1. Accordingly, one of the second switches SW3 is connected between the first input terminal 11 and the second terminal 26 of the inductor L1, and the other of the second switches 5W4 is connected between the second input terminal 12 and the second terminal 26 of the inductor L1.
In the example illustrated in Figure 1, the pair of third switches or diodes 18 comprises switches SW5 and 5W6. However, the converter 10 might alternatively comprise diodes. The use of a switch over a diode has the advantage of lower conduction losses, and may be used to provide synchronous rectification.
Each of the third switches SW5,5W6 (or diodes if provided) is connected between a respective input terminal 11,12 and a negative terminal 28 of the capacitor C1. Accordingly, one of the third switches SW5 is connected between the first input terminal 11 and the negative terminal 28 of the capacitor C 1, and the other of the third switches 5W6 is connected between the second input terminal 12 and the negative terminal 28 of the capacitor Cl.
The inductor L1 comprises a first terminal 25 connected to each of the first switches SW1,SW2, and a second terminal 26 connected to each of the second switches SW3,SW4. The second terminal 26 is additionally connected to a positive terminal 27 of the capacitor Cl.
The capacitor Cl comprises a positive terminal 27 connected to the second terminal 26 of the inductor L1, and a negative terminal 28 connected to each of the third switches SW5,SW6 (or diodes, if provided). The positive terminal 27 is additionally connected to one of the output terminals 13, and the negative terminal 28 is connected to the other of the output terminals 14.
The controller 20 is responsible for controlling the operation of the converter 10 and generates control signals S 1-S 6 for controlling each of the switches SW1-S W6. The control signals are output to the gate driver 19, which in response outputs gate signals for driving the switches.
Operation of the converter 10 will now be described with reference to Figures 2 to 5.
The converter 10 has two modes of operation: buck and boost Figures 2 and 3 illustrate configurations of the switches when the converter operates in buck mode, and Figures 4 and 5 illusffate configurations of the switches when the converter operates in boost mode.
Figure 2 illustrates two configurations when the converter 10 operates in buck mode and the polarity of the input voltage VIN is positive. In the first configuration, shown in Figure 2(a), first switch SW1 is ON, first switch 5W2 is D1, both second switches are OFF, third switch SW5 is OFF and third switch 5W6 is ON. As a result the inductor L1 is energised by the power supply, with current flowing through the inductor L1 in a direction from left to right In the second configuration, shown in Figure 2(b), first switch SW1 is OFF, first switch SW2 is D1, both second switches are OFF, third switch SW5 is OFF and third switch SW6 is ON. Energy stored in the inductor L1 is then transferred to the capacitor C1.
The only difference between the two configurations is the state of first switch SW1, which is ON in the first configuration and OFF in the second configuration. The states of second switch SW2 (which is D1) and third switch SW6 (which is ON) do not change. As noted above, third switch SW6 could conceivably be a diode. However, the provision of the third switch 5W6 enables synchronous rectification to be achieved, thereby improving the efficiency of the converter.
Figure 3 illustrates two configurations when the converter 10 operates in buck mode and the polarity of the input voltage VIN is negative. In the first configuration, shown in Figure 3(a), first switch SW1 is D1, first switch 5W2 is ON, both second switches are OFF, third switch SW5 is ON and third switch SW6 is OFF. As a result the inductor L1 is energised by the power supply, with current flowing through the inductor L1 in a direction from left to right In the second configuration, shown in Figure 3(b), first switch SW1 is D1, first switch SW2 is OFF, both second switches are OFF, third switch SW5 is ON and third switch SW6 is OFF. Energy stored in the inductor L1 is then transferred to the capacitor Cl.
It will be apparent that the configurations of Figure 3 mirror those of Figure 2. For example, the only difference between the first and second configurations of Figure 3 is the state of the first switch SW2, which is ON in the first configuration and OFF in the second configuration. Again, third switch SW5 could conceivably be a diode.
Common to both Figures 2 and 3 is the notion that, when operating in buck mode, the controller 20 configures the switches in: a first configuration in which one of the first switches is ON, the other of the first switches is D1, and both second switches are OFF to energise the inductor L1; and a second configuration in which one of the first switches is OFF, the other of the first switches is D1, and both second switches are OFF such that energy is transferred from the inductor L1 to the capacitor Cl.
The choice of switches that are ON or D1 is determined by the polarity of the input voltage VIN.
Figure 4 illustrates two configurations when the converter 10 operates in boost mode and the polarity of the input voltage VIN is positive. In the first configuration, shown in Figure 4(a), first switch SW1 and second switch SW4 are ON, and all other switches SW2, SW3, SWS and SW6 are OFF. As a result, the inductor L1 is energised by the power supply, with current flowing through the inductor L1 in a direction from left to right In the second configuration, shown in Figure 4(b), first switch SW1 and third switch SW6 are ON, and all other switches SW2-SW5 are OFF. Energy stored in the inductor L1 is then transferred to the capacitor C1.
The only difference between the two configurations is the states of second switch SW4 and third switch SW6. In particular, second switch SW4 is ON and third switch SW6 is OFF in the first configuration, and second switch 5W4 is OFF and third switch SW6 is ON in the second configuration. As noted above, third switch SW6 could conceivably be a diode. In this instance, the only difference between the two configurations would be the state of the second switch SW4. However, the provision of the third switch SW6 enables synchronous rectification to be achieved, thereby improving the efficiency of the converter.
There is a deadtime between turning OFF the second switch SW4 and turning ON third switch SW6, and vice versa. This then prevents a short circuit of the capacitor Cl. The deadtime may be implemented by the controller 20 (i.e. by introducing a deadtime between changes in signals 54 and 56) or by the gate driver 19 (i.e. by introducing a deadtime between changes in the gate signals for switches SW4 and SW6). During the deadtime, a path is provided for the inductive current through the body diode of the third switch SW6. This then has the advantage that zero-voltage switching may be achieved when turning ON the third switch, thereby further improving efficiency.
Figure 5 illustrates two configurations when the converter 10 operates in boost mode and the polarity of the input voltage VIN is negative. In the first configuration, shown in Figure 5(a), first switch SW2 and second switch SW3 are ON, and all other switches SW1, 5W4, 5W5 and 5W6 are OFF. As a result, the inductor L1 is energised by the power supply, again with current flowing through the inductor L1 in a direction from left to right In the second configuration, shown in Figure 5(b), first switch SW2 and third switch SW5 are ON, and all other switches SW1, SW3, SW4 and SW6 are OFF. Energy stored in the inductor L1 is then transferred to the capacitor Cl.
It will be apparent that the configurations of Figure 5 mirror those of Figure 4. For example, the only difference between the first and second configurations of Figure 5 is the states of the second and third switches SW3,SW5. In particular, second switch SW3 is ON and third switch SW5 is OFF in the first configuration, and second switch SW3 is OFF and third switch SW5 is ON in the second configuration. Again, third switch SW5 could conceivably be a diode, in which case the state of the second switch SW3 only changes.
Common to both Figures 4 and 5 is the notion that, when operating in boost mode, the controller 20 configures the switches in: a first configuration in which one of the first switches and one of the second switches are ON, and the other of the first switches and the other of the second switches are OFF to energise the inductor L1; and a second configuration in which one of the first switches is ON, the other of the first switches is OFF, and both second switches are OFF such that energy is transferred from the inductor L1 to the capacitor C1. The choice of switches that are ON is determined by the polarity of the inputvoltage VIN.
When operating in either buck mode or boost mode, the controller 20 repeatedly switches between the first configuration and the second configuration in order to transfer power from the power supply 30 to the capacitor Cl. The controller 20 switches between the two configurations at a duty, which the controller 20 controls in order to regulate the output voltage Vour whilst also shaping the input current drawn from the power supply 30.
Figure 6 illustrates the states of the switches W1-SW6 over one cycle of the input voltage VIN. It can be seen that the converter 10 operates in buck mode when the input voltage VIN is greater than a target or nominal output voltage, and the converter 10 operates in boost mode when the input voltage VIN is less than the nominal output voltage.
When the converter 10 operates in boost mode (Figures 4 and 5), the current drawn from the power supply 30 is continuous; that is to say that current is drawn from the power supply 30 when the converter 10 is configured in both the first configuration and the second configuration. By contrast, when the converter 10 operates in buck mode (Figures 2 and 3), the current drawn from the power supply 30 is discontinuous. Whilst current is drawn from the power supply 30 when the converter 10 is configured in the first configuration, no current is drawn from the power supply 30 when the converter 10 is configured in the second configuration, as can be seen in Figures 2(b) and 3(b). The input filter 15 then attenuates the higher frequency harmonics within the input current that arise from the discontinuous nature of the converter 10 when operating in buck mode. With the topology of the converter 10, a current source (i.e. the inductor L1) is positioned between two voltage sources (i.e. the power supply 30 and the capacitor Cl).
Consequently, although the input current is discontinuous when operating in buck mode, the input current can nevertheless be actively profiled, e.g. such that it is sinusoidal in shape.
The converter 10 provides AC-to-DC conversion without the need for a rectifier bridge or front-end bulk capacitor. Moreover, the converter provides AC-to-DC conversion using just six devices (i.e. six switches, or four switches and two diodes), an inductor arid a capacitor. The converter 10 has discreet buck and boost modes. Consequently, the converter 10 may be used in buck mode only, boost mode only, or a combination of buck and boost modes, as illustrated in Figure 6.
With the topology of the converter 10, the inductor L1 is energised in the same direction irrespective of the polarity of the input voltage. As a result, hysteresis losses may be reduced (in comparison to a topology in which the inductor is energised in opposite directions).
In the example described above, each of the first switches SW1,SW2 has four states: ON, D1, D2 and OFF. Although the switch has two diode states, D1 and D2, only one of the diode states is ever used, namely Dl. Moreover, although the switch is conductive in both directions when in an ON state, the switch is required to conduct in one direction only, namely upwards. Accordingly, in a more general sense, each of the first switches may be said to have (i) an ON state in which the switch is conductive in at least a first direction, (ii) a diode state in which the switch is conductive in the first direction and is non-conductive in a second direction, and (ii) an OFF state in which the switch is non-conductive in both the first direction and the second direction.
Although the first switches SW1,SW2 and the second switches SW3,SW4 are required to conduct in one direction only, there are advantages in employing switches that can conduct in both directions. In particular, the converter 10 may be used for bidirectional power transfer. That is to say that power may be transferred from the power supply 30 to the capacitor Cl in the manner described above (i.e. forward power transfer). Additionally, power may be transferred from the capacitor C1 to the power supply 30 (i.e. reverse power transfer), as will now be described.
Figure 7 illustrates a pair of configurations for achieving reverse power transfer. In the first configuration, shown in Figure 7(a), first switch SW1 and third switch SW5 are ON, and all other switches are OFF. As a result, the inductor Li is energised by the capacitor C1, with current flowing through the inductor Li in a direction from right to left. In the second configuration, shown in Figure 7(b), first switch SW1 and second switch 5W4 are ON, and all other switches are OFF. As a result energy stored in the inductor L1 is transferred to the power supply 30.
Figure 7 illusintes configurations for reverse power transfer when the polarity of the input voltage VIN is positive. When the polarity of the input voltage VIN is negative, switches SW2 and 5W6 are ON (and all other switches are OFF) in the first configuration, and switches SW2 and SW3 are ON (and all other switches are OFF) in the second configuration.
Figure 8 illustrates an alternative pair of configurations for achieving reverse power transfer. In the first configuration, shown in Figure 8(a), first switch SW1 and third switch SW6 are ON, and all other switches are OFF. As a result, energy is transferred from the capacitor C1 to both the inductor L1 and the power supply 30. In the second configuration, shown in Figure 8(b), first switch SW1 and second switch SW4 are ON, and all other switches are OFF. As a result energy stored in the inductor L1 is transferred to the power supply 30.
Again, Figure 8 illustrates configurations for reverse power transfer when the polarity of the input voltage VIN is posilive. When the polarity of the input voltage VIN is negative, switches SW2 and SW5 are ON (and all other switches are OFF) in the first configuration, and switches SW2 and 5W3 are ON (and all other switches are OFF) in the second configuration.
With the configurations illustrated in Figure 8, reverse power transfer is possible only when the voltage of the capacitor C1 is greater than the voltage of the power supply 30, i.e. when VOUT is greater than VIN. By contrast the configurations illustrated in Figure 7 are capable of providing reverse power transfer irrespective of the voltages of the capacitor Cl and the power supply 30.
Whilst particular examples and embodiments have thus far been described, it will be understood that various modifications may be made without departing from the scope of the invention as defined by the claims.

Claims (9)

  1. CLAIMS1. A buck-boost converter comprising: first and second input terminals for connection to a power supply supplying an alternating input voltage; first and second output terminals for outputting an output voltage; a pair of first switches; a pair of second switches; a pair of third switches or diodes; an inductor having a first terminal and a second terminal; a capacitor having a first terminal and a second terminal; and a controller for controlling the switches, wherein: one of the first switches is connected between the first input terminal and the first terminal of the inductor, and the other of the first switches is connected between the second input terminal and the first terminal of the inductor; one of the second switches is connected between the first input terminal and the second terminal of the inductor, and the other of the second switches is connected between the second input terminal and the second terminal of the 20 inductor; one of the third switches or diodes is connected between the first input terminal and the second terminal of the capacitor, and the other of the third switches or diodes is connected between the second input terminal and the second terminal of the capacitor; the first terminal of the capacitor is connected to the second terminal of the inductor and to the first output terminal, and the second terminal of the capacitor is connected to the second output terminal; each of the first switches has an ON state in which the switch is conductive in at least a first direction, a diode state in which the switch is conductive in the first direction and is non-conductive in a second direction, and an OFF state in which the switch is non-conductive in both the first direction and the second direction; and each of the second switches has an ON state in which the switch is conductive in at least a first direction, and an OFF state in which the switch is nonconductive in both the first direction and a second direction.
  2. 2. A converter as claimed in claim 1, wherein the controller configures the switches in a configuration in which the inductor is energised by the power supply, and a further configuration in which energy stored in the inductor is transferred to the capacitor.
  3. 3. A converter as claimed in claim 1 or 2, wherein, in a buck mode, the controller configures the switches in: a first configuration in which one of the first switches is ON, the other of the first switches is in the diode state, and both second switches are OFF; and a second configuration in which one of the first switches is OFF, the other of the first switches is in the diode state, and both second switches are OFF.
  4. 4. A converter as claimed in claim 3, wherein, in the first configuration, one of the first switches is ON and the other of the first switches is in the diode state when a polarity of the input voltage is positive, and the other of the first switches is ON and the one of the first switches is in the diode state when the polarity of the input voltage is negative.
  5. 5. A converter as claimed in any one of the preceding claims, wherein, in a boost mode, the controller configures the switches in: a first configuration in which one of the first switches and one of the second switches are ON, and the other of the first switches and the other of the second switches are OFF; and a second configuration in which one of the first switches is ON, the other of the first switches is OFF, and both second switches are OFF.
  6. 6. A converter as claimed in claim 5, wherein, in the first configutation, one of the first switches and one of the second switches are ON when a polarity of the input voltage is positive, and the other of the first switches and the other of the second switches are ON when the polarity of the input voltage is negative.
  7. 7. A converter as claimed in any one of claims 2 to 6, wherein the inductor is energised in the first configuration, and the inductor is energised in the same direction irrespective of a polarity of the input voltage.
  8. 8. A converter as claimed in any one of the preceding claims, wherein the first switches and the second switches are the same type of switch.
  9. 9. A converter as claimed in any one of the preceding claims, wherein each of the first switches and each of the second switches is conductive in both the first direction and the second direction when in the ON state.A buck-boost converter comprising: input terminals for connection to a power supply supplying an alternating input voltage; output terminals for outputting an output voltage; a pair of first switches, each of the first switches having an ON state in which the switch is conductive in at least a first direction, a diode state in which the switch is conductive in the first direction and is non-conductive in a second direction, and an OFF state in which the switch is non-conductive in both the first direction and the second direction; a pair of second switches, each of the second switches having an ON state in which the switch is conductive in at least a first direction, and an OFF state in which the switch is non-conductive in both the first direction and a second direction; a pair of third switches or diodes; an inductor connected between the first switches and the second switches; a capacitor; arid a controller for controlling the switches, wherein: in a buck mode the controller configures the switches in: a first configuration in which one of the first switches is ON, the other of the first switches is in the diode state, and both second switches are OFF, thereby causing the inductor to be energised by the power supply; and a second configuration in which one of the first switches is OFF, the other of the first switches is in the diode state, and both second switches are OFF, thereby causing energy stored in the inductor to be transferred to the capacitor, and in a boost mode the controller configures the switches in: a first configuration in which one of the first switches and one of the second switches are ON, and the other of the first switches and the other of the second switches are OFF, thereby causing the inductor to be energised by the power supply; and a second configuration in which one of the first switches is ON, the other of the first switches is OFF, and both second switches are OFF, thereby causing energy stored in the inductor to be transferred to the capacitor.
GB2019283.7A 2020-12-08 2020-12-08 Buck-boost converter Pending GB2601751A (en)

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GB2019283.7A GB2601751A (en) 2020-12-08 2020-12-08 Buck-boost converter
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150022164A1 (en) * 2013-07-17 2015-01-22 Delta Electronics (Shanghai) Co., Ltd. Power factor correction converter and control method thereof

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WO2012176403A1 (en) * 2011-06-21 2012-12-27 パナソニック株式会社 Boost-type ac/dc converter
JP5678860B2 (en) * 2011-10-07 2015-03-04 株式会社安川電機 AC / DC converter

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150022164A1 (en) * 2013-07-17 2015-01-22 Delta Electronics (Shanghai) Co., Ltd. Power factor correction converter and control method thereof

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