GB2427968A - A full bridge circuit - Google Patents

A full bridge circuit Download PDF

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Publication number
GB2427968A
GB2427968A GB0513204A GB0513204A GB2427968A GB 2427968 A GB2427968 A GB 2427968A GB 0513204 A GB0513204 A GB 0513204A GB 0513204 A GB0513204 A GB 0513204A GB 2427968 A GB2427968 A GB 2427968A
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GB
United Kingdom
Prior art keywords
switching devices
full bridge
bridge circuit
pair
devices
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0513204A
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GB0513204D0 (en
Inventor
Neil Frank Dudley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TYCO ELECTRONICS
Original Assignee
TYCO ELECTRONICS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TYCO ELECTRONICS filed Critical TYCO ELECTRONICS
Priority to GB0513204A priority Critical patent/GB2427968A/en
Publication of GB0513204D0 publication Critical patent/GB0513204D0/en
Priority to PCT/GB2006/002249 priority patent/WO2007000572A1/en
Publication of GB2427968A publication Critical patent/GB2427968A/en
Withdrawn legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53Conversion of dc power input into ac 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
    • H02M7/537Conversion of dc power input into ac 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, e.g. single switched pulse inverters
    • H02M7/5387Conversion of dc power input into ac 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, e.g. single switched pulse inverters in a bridge configuration
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS 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
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/505Conversion of dc power input into ac 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 thyratron or thyristor type requiring extinguishing means
    • H02M7/515Conversion of dc power input into ac 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 thyratron or thyristor type requiring extinguishing means using semiconductor devices only
    • H02M7/521Conversion of dc power input into ac 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 thyratron or thyristor type requiring extinguishing means using semiconductor devices only in a bridge configuration

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Power Conversion In General (AREA)

Abstract

A full bridge circuit (10) comprises first (TR2, TR3) and second (TR1, TR4) pairs of parallel connected one-way, switching devices, each respective said switching device (TR1, TR4) of the second pair being connected in series with a respective said switching device (TR2, TR3) of the first said pair to define two switchable parallel conducting paths. A load (11) is connected so as to bridge the parallel conducting paths between the said switching devices (TR2, TR3) of the first pair and the said switching devices (TR1, TR4) of the second pair, and the circuit is connectable so as to apply an alternating current to flow in the parallel conducting paths. The circuit is characterised in that the switching devices (TR2, TR3) of the first pair are field effect transistor (FET) devices; and the switching devices of the second pair (TR1, TR4) are insulated gate bipolar transistor (IGBT) devices.

Description

A FULL BRIDGE CIRCUIT
This invention relates to a circuit configuration known as a full bndge circuit.
The basic design of such a circuit is cxtreme]y well known. A full bridge is used to convert a DC supply to AC to drive a load.
One known form of such a circuit is shown in Figure 1.
In Figure 1 four switching devices TR1, TR2, TR3, TR4 are shown coimected in a conventional bridge circuit 10. TR1, TR2, TR3 and TR4 are, as shown, field- effect transistor ("FET") devices. Usually FET transistors are considered most suitable for this duty as they arc available with high voltage and current ratings, and switch from the "off' (open circuit) state to the "on" (conductive state) quickly. One characteristic of a typical FET device is the unavoidable inclusion of a diode formed as part of the construction. This diode electrically appears in parallel with the FET switching element. Often the diode is of no consequence as the circuit reverse biases the diode, and it never conducts.
in this circuit one may consider the switching devices TR2, TR3 as a first pair of such devices, and the switching devices TRI, TR4 as a second pair of such devices.
Each respective switching device TRI, TR4 of the second pair is connected in series with a respective switching device of the first pair.
Thus switching device TRI is connected in series with switching device TR2.
Switching device TR4 is connected in series with switching device TR3.
The switching devices TR1, TR2 constitute a first, switchable conducting path that is connected in parallel with a second, switchable, conducting path constituted by the series connection of the diodes TR4, TR3 of the respective pairs.
The switching devices TRI, TR2, TR3, TR4 are arranged so as to be forwardly conducting in the directions as conventionally signified by their symbols used in Figure 1.
A load 11 is connected so as to bridge the aforesaid parallel conducting paths.
Load 11 defines such a bridge at a location that is intermediate the two pairs of switching devices.
As is conventional, an inductor 12 is connected in series with the load 11 for the purpose of reducing, in a per se known manner, high frequency fluctuations resulting from known effects of the switching device switching action.
The inductor 12 typically is a component added in series with the load 11 for this purpose. In some other arrangements, however, one may consider the inductor 12 to be an inherent characteristic of the load device 11.
A gate driver 13 is operatively connected to each switching device TR1, TR2, TR3, TR4 as shown, for the purpose of switching the switching devices in a manner that is well known in the art.
During use of the circuit of Figure 1 a DC voltage is applied across the circuit terminals represented by numerals 14 and 16. In the arrangement shown, terminal 16 is designated as the ground ("GND").
"400 V" adjacent terminal 14 signifies a typical DC voltage that may he applied when the circuit of Figure 1 is used as part of an AC waveform power supply.
In the arrangement of Figure 1, the composite load represented by components 11 and 12 may be considered as terminated at either end at the connectors labelled L2 and LI in Figure 1. These labels will be referred to in the remainder of the descnption.
In use of the Figure 1 circuit, during the positive half cycle when current is flowing from L2 to LI, TR4 is switched on and TR1 and TR2 are driven with a variable mark space ratio such that TRI and TR2 are never both on at the same time. The effective voltage across the load varies in proportion to the mark space ratio. When TRI is always on, no current flows through the load. When TR2 is always on, the full bridge DC supply voltage is presented across the load, and when the duty cycle is 50%, the effective voltage across the load corresponds to that which would flow with roughly half the DC supply voltage. By varying the mark space ratio suitably, the current through the load can be made to approximate a sinusoidal shape or any other desired waveform and the amplitude of that waveform can be varied by adjusting the peak mark space ratio.
The negative half cycle of the waveform can be generated in a similar manner but with TR4 off and TR3 on, in a manner known to those of skill in the art.
A disadvantage of the Figure 1 circuit is that in an attempt to avoid the undesirable condition where TRI and TR2 are on simultaneously, a delay is introduced so that TRI has time to turn off before TR2 turns on and vice versa. A typical delay might be of the order of one or several microseconds. However, during the period that both TRI and TR2 are off, the current that was flowing in the inductor has to flow through another path, namely the parasitic diode which is formed as part of the construction of the FET devices shown.
For example if current is flowing through TR1, and TR1 is turned off in preparation for the control circuit to turn on TR2, the current then flows via TR1 parasitic diode. Usually the unintentional but unavoidable parasitic diode integral with the FET is relatively slow to turn off when the voltage across it is reversed.
This means that for a short period of time, typically a fraction of a microsecond, the diode inside TR I is conducting and TR2 is turned on leading to a near short circuit across the DC supply. For a fraction of a microsecond, a high current flows in TRI and TR2 until the diode in TR1 re-establishes reversed biased (blocking) condition from the forward (current carrying) condition. A similar effect occurs during the reverse changeover when TR2 is turned off and TR1 starts to turn on.
This current is undesirable as it causes large high frequency currents to flow, generating electrical interference, heating up TRI and TR2, and wasting energy that had been intended to be delivered to the load.
A similar effect can occur in devices TR3 and TR4 but this is generally less troublesome, both because the switching frequency is often much lower, so the effect occurs less often, and because the circuit currents through the load are usually low when TR3 and TR4 switch over.
Various modifications to this circuit are possible but undesirably they generally increase complexity and cost and result in additional power losses.
One popular option is to replace the FET's with insulated gate bipolar transistor ("IGBT") devices. These do not have the parasitic diode, but are usually slower to switch from one state to the other and particularly from the on to the off state.
During this transitional period, the 1GBT dissipates significant power which again wastes energy and causes undesirable heating of circuit components.
According to the invention in a first aspect there is provided a full bridge circuit comprising first and second pairs of parallel connected, one-way switchable switching devices, each respective said switching device of the second pair being connected in series with a respective said switching device of the first said pair to define two switchable parallel conducting paths, a load being connected so as to bridge the parallel conducting paths between the said switching devices of the first pair and the said switching devices of the second pair, and the circuit being connectable so as to apply an alternating current selectively to flow in parts of the parallel conducting paths, characterised in that the switching devices of the first pair are FET devices; and the switching devices of the second pair are IGBT devices.
Conveniently the circuit of the invention includes one or more gate drivers for driving the gate terminals of the switching devices so as selectively to switch the switching devices on and off.
In a preferred embodiment of the invention one or more of the gate drivers selectively switches the switching devices defining one of the said parallel conducting paths at a time according to a variable mark space ratio sequence.
Conveniently one or more of the said gate drivers switches the switching devices, of the first and second pairs that define one of the said parallel conducting paths, such that the switching devices of the said conducting path are never simultaneously forwardly conducting.
It is also preferred that one or more of the said gate drivers selectively adjusts the peak mark space ratio applied to the switching devices of a said conducting path, whereby to adjust the amplitude of the waveform applied to the load.
Conveniently the circuit includes an inductor connected in series with the load.
Advantages of circuits in accordance with the invention are set out hereinbelow.
There now follows a description of a preferred embodiment of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 is a schematic representation of a prior art, switched, full bridge circuit; and Figure 2 is a schematic representation of a switched, full bridge circuit according to the invention.
As is evident from Figure 2, a circuit 10 according to the invention is very similar in configuration to the prior art circuit of Figure 1. The primary difference between the circuits of Figures 1 and 2 is that in Figure 1 all four switching devices TRI, TR2, TR3, TR4 are FET devices. in contrast in Figure 2 the switching devices TRI and TR4 are JGBT transistors.
In view of the similarities between the Figure 1 and Figure 2 circuits, the following description refers principally to the effects of using IGBT's as the switching devices TR1 and TR4. Thus the reader of skill in the art would understand that the basic bridge principles described hereinabove in relation to Figure 1 apply in relation to the Figure 2 circuit.
In the Figure 2 circuit TRI and TR4 (IGBT) switch at the lower frequency, while TR2 or TR3 (FET) as desired are modulated on with a variable duty cycle to control the effective voltage across the load. IGBT switching devices do not have a parasitic diode. in practice manufacturers sometimes add a diode inside the same packaged circuit element as shown in the example above, instead of the diode being slow, inherent and unavoidable, as with FETs, the IGBT diode is specially designed for rapid recovery from the forward (current carrying) condition to the reversed biased (blocking) condition. If the IGBT chosen does not have an internal diode, a suitable external diode can be readily added during construction of the Figure 2 circuit.
in the context of diodes it should be noted that the term "fast" refers to the ability of a diode to shut off current flow very quickly, perhaps in order of tens of nanoseconds, after the voltage across the diode reverses from a polarity which equates to the diode being forward biased and conducting, to the condition where the diode is reversed biased and conventionally regarded as non conducting.
Conversely the term "slow" refers to a diode where the essential cessation of current flow under the condition described may take a significant fraction of a microsecond or even longer to occur.
In the preferred circuit according to the invention, during the positive half cycle when current is to flowing from L2 to Li, TR4 is switched on and TR2 is driven with a variable mark space ratio. The effective voltage across the load varies in proportion to the mark space ratio.
When TR2 is always off, no current flows through the load, and when TR2 is always on the full bridge DC supply voltage is presented across the load. When the duty cycle is 50%, the current through the load corresponds to that which would flow with roughly half the DC supply voltage. By varying the mark space ratio suitably, the current through the load can he made to approximate a sinusoidal shape or any other desirable waveform and the amplitude of that waveform can be varied by adjusting the peak mark space ratio.
During the mark space modulation switching, when TR2 is off, the current that was flowing in the inductor continues to flow via the diode in parallel with TRI, circulating in a clockwise direction through TR4, load 11, inductor 12 and TRI.
When TR2 is on, the diode inside or in parallel with TRI recovers rapidly resulting in much less wasted power inside TR2 than in the case of the prior art circuit.
The FETs used in position TR2 and TR3 switch faster than IGBT devices, so their switching losses are less. Typically, in a bridge circuit designed to generate an AC waveform in the range of tens of Hz to hundreds of Hz these switch at a speed in the range of kT-Iz to hundreds of kHz. The IGBT devices used in positions TRI and TR4 have higher switching losses, but as their switching rate is hundreds of times lower than that of the FET's, a switching loss of several times or even 10 times the switching loss of the FET's is acceptable and has limited impact on the overall circuit efficiency and losses. Also, the slow speed switching tends to occur when the load current is relatively low which also minitnises losses when the IGBT's switch.
The negative half cycle of the waveform can be generated in a similar manner but with TR4 off and TR I on, and TR3 being modulated onloff to generate the desired waveshape.
The configuration of the invention improves efficiency, and requires only slow speed drive to the upper devices TRI and TR4, which cannot share a common ground. TR2 and TR3 share a ground and it is generally easier and less expensive to implement high speed gate drives which are ground referenced.
Although as signified in Figure 2 the circuit of the invention is preferably intended to receive a DC voltage amplitude of 400 volts, being a typical amphtude of a DC supply derived from common single phase mains supply voltages via a piower factor correction circuit, the circuit of the invention may readily he configured to operate at other DC supply voltages. The precise choices of the PET and IGBT components needed to achieve such alteration of the circuit will occur to those of skill in the art. The invention as claimed is intended to embrace all such variants as would occur to such a worker.
S

Claims (10)

1. A full bridge circuit comprising first and second pairs of parallel connected one-way, switching devices, each respective said switching device of the second pair being connected in series with a respective said switching device of the first said pair to define two switchahie parallel conducting paths, the parallel conducting paths being connectable across a DC supply; a load being connected so as to bridge the parallel conducting paths between the said switching devices of the first pair and the said switching devices of the second pair; and the circuit being connectable so as to apply an alternating current selectively to flow in parts of the parallel conducting paths, characterised in that the switching devices of the first pair are field effect transistor (PET) devices; and the switching devices of the second pair are insulated gate bipolar switching device (IGBT) devices.
2. A full bridge circuit according to Claim I including a fast recovery diode to provide an alternate current path when the FET device is switched off.
3. A full bridge circuit according to Claim I including said fast recovery diode electrically in parallel with the IGBT switch.
4. A full bridge circuit according to Claim I including one or more gate drivers for driving the gate terminals of the switching devices so as selectively to switch the switching devices on and off.
5. A full bridge circuit according to Claim 2 wherein one or more said gate drivers selectively switches the PET transistors defining one of the said parallel conducting paths at a time according to a variable mark space ratio sequence.
6. A full bridge circuit according to any of Claim 2 or Claim 3 wherein one or more said gate drivers switches the switching devices, of the first and second pairs that define one of the said parallel conducting paths, such that the switching devices of the said conducting path are never simultaneously forwardly conducting.
7. A full bridge circuit according to any of Claims 2 to 4 wherein one or more said gate drivers selectively adjusts the peak mark space ratio applied to the switching devices of a said conducting path, whereby to adjust the amplitude of the waveform applied to the load.
8. A full bridge circuit according to any preceding claim including an inductor connected in series with the load.
9. A full bridge circuit generally as herein described, with reference to and/or as illustrated in Figure 2 of the accompanying drawings.
10. A full bridge circuit according to any preceding claim the parallel conducting paths of which are connected across a DC supply.
GB0513204A 2005-06-29 2005-06-29 A full bridge circuit Withdrawn GB2427968A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB0513204A GB2427968A (en) 2005-06-29 2005-06-29 A full bridge circuit
PCT/GB2006/002249 WO2007000572A1 (en) 2005-06-29 2006-06-20 A full bridge circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0513204A GB2427968A (en) 2005-06-29 2005-06-29 A full bridge circuit

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GB0513204D0 GB0513204D0 (en) 2005-08-03
GB2427968A true GB2427968A (en) 2007-01-10

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010112514A1 (en) * 2009-04-03 2010-10-07 Sagem Defense Securite Engine power supply circuit, and flight control member provided with such a circuit
RU172407U1 (en) * 2016-12-23 2017-07-07 Федеральное государственное бюджетное образовательное учреждение высшего образования "Санкт-Петербургский государственный университет телекоммуникаций им. проф. М.А. Бонч-Бруевича" (СПбГУТ) CONTROLLED RESONANT CURRENT INVERTER

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0502715A1 (en) * 1991-03-04 1992-09-09 Cooperheat International Ltd. Power converter
US20030132211A1 (en) * 2000-01-20 2003-07-17 Hubert Aigner Method for regulating and/or controlling a welding current source with a resonance circuit
US20050105314A1 (en) * 2003-10-07 2005-05-19 Nielsen Henning R. Three level inverter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0502715A1 (en) * 1991-03-04 1992-09-09 Cooperheat International Ltd. Power converter
US20030132211A1 (en) * 2000-01-20 2003-07-17 Hubert Aigner Method for regulating and/or controlling a welding current source with a resonance circuit
US20050105314A1 (en) * 2003-10-07 2005-05-19 Nielsen Henning R. Three level inverter

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Soft switching of IGBTs with the help of MOSFETs in bridge-type converters, Jiang et al.,Proceedings of the annual power electronics specialists conference(PESC), Seattle, June 20-25, 1993, New York, IEEE, US, published 1993-06-20. *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010112514A1 (en) * 2009-04-03 2010-10-07 Sagem Defense Securite Engine power supply circuit, and flight control member provided with such a circuit
FR2944166A1 (en) * 2009-04-03 2010-10-08 Sagem Defense Securite MOTOR SUPPLY CIRCUIT AND FLIGHT CONTROL MEMBER EQUIPPED WITH SUCH A CIRCUIT
CN102369656A (en) * 2009-04-03 2012-03-07 萨甘安全防护公司 Engine power supply circuit, and flight control member provided with such a circuit
US8669733B2 (en) 2009-04-03 2014-03-11 Sagem Defense Securite Engine power supply circuit, and flight control member provided with such a circuit
RU172407U1 (en) * 2016-12-23 2017-07-07 Федеральное государственное бюджетное образовательное учреждение высшего образования "Санкт-Петербургский государственный университет телекоммуникаций им. проф. М.А. Бонч-Бруевича" (СПбГУТ) CONTROLLED RESONANT CURRENT INVERTER

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Publication number Publication date
WO2007000572A1 (en) 2007-01-04
GB0513204D0 (en) 2005-08-03

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