GB1588135A - Inverter circuits - Google Patents

Inverter circuits Download PDF

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Publication number
GB1588135A
GB1588135A GB30060/77A GB3006077A GB1588135A GB 1588135 A GB1588135 A GB 1588135A GB 30060/77 A GB30060/77 A GB 30060/77A GB 3006077 A GB3006077 A GB 3006077A GB 1588135 A GB1588135 A GB 1588135A
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United Kingdom
Prior art keywords
circuit
transistors
transistor
switching
pair
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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.)
Expired
Application number
GB30060/77A
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Danfoss AS
Original Assignee
Danfoss AS
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Filing date
Publication date
Application filed by Danfoss AS filed Critical Danfoss AS
Publication of GB1588135A publication Critical patent/GB1588135A/en
Expired 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/34—Snubber circuits
    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion 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
    • H02M7/53—Conversion 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
    • H02M7/537—Conversion 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
    • H02M7/5387—Conversion 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
    • 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
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion 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
    • H02M7/53—Conversion 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
    • H02M7/537—Conversion 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
    • H02M7/5387—Conversion 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
    • H02M7/53871—Conversion 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 with automatic control of output voltage or current
    • 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H02M1/34—Snubber circuits
    • H02M1/348—Passive dissipative snubbers

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)
  • Mechanical Operated Clutches (AREA)

Description

(54) INVERTER CIRCUITS (71) We, DANFOSS A/S, a Danish Company, of DK -6430 Nordborg, Denmark, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to inverter circuits.
A known inverter circuit comprises a pair of transistors connected in series between two D.C. voltage supply leads. An output to a load is taken from the junction of the two transistors and they are alternately switched into a conducting state. Each transistor is arranged in parallel with a respective auxiliary circuit, each auxiliary circuit comprising a capacitor in series with the parallel combination of a resistor and a diode poled in the same sense as the conducting direction of the associated transistor.
In the known inverter circuit, such an auxiliary circuit, which is also termed a R-C-D protective circuit, is provided for the following reason. If in a transistor without the auxiliary or protective circuit there is no control voltage at the base, the emitter current drops back to zero suddenly but within a finite time, whilst the collector-emitter voltage increases from a low value to full magnitude, this again being sudden but within a finite time. Consequently, power is converted in the transistor that can lead to destruction of the transistor in the course of time. By using the protective circuit, the rise in the collectoremitter voltage is retarded in relation to the drop in the emitter current. Consequently the power converted in the transistor on 'switching off' can be kept so low that it is no longer harmful.
Surprisingly, it has been found that despite careful dimensioning of the protective circuit damage occurs to the transistors when these are connected insseries in pairs in an inverter.
According to the invention, there is provided an inverter circuit comprising: a pair of terminals for connection to a D.C. supply, one or more pairs of switching transistors, the two transistors of the (or any particular) pair being connected in series with each other between the terminals, means to switch the transistors selectively to derive an A.C. output from the D.C.
supply by switching ON the transistors of the (or any particular) pair alternately with a dead period between switching OFF one transistor of a pair and switching ON the other transistor of the pair, a respective protective circuit connected in parallel with each switching transistor each protective circuit comprising a capacitor in series with the parallel combination of an ohmic resistor and a diode poled in the same direction as current flow through the switching transistor, and just one supplementary protection circuit including an inductor connected in series with the said one or more pairs of switching transistors to limit the charging current of the capacitor in each protective circuit.
In such an inverter circuit, the transistors that are used are more safely protected against damage.
This result is achieved in that the supplementary circuit including an inductor is provided in series with the pair or pairs of transistors and associated protective circuits.
In an inverter circuit in which the transistors of a serially-connected pair are alternately brought to the conductive state, a certain dead period should be provided between 'switching off' the first transistor and 'switching on' the second transistor so that a short circuit path can on no account occur through both transistors between the two supply leads.
For safety reasons, this dead period should be chosen to be too long rather than too short. Within the dead period, the D.Q voltage is distributed so that about U/2 (where U is the D.C. supply voltage) is applied to each capacitor of the protective circuits. If the one transistor is then brought to the conductive state, the full voltage U will suddenly be applied to the capacitor associated with the other transistor. This leads to a correspondingly high charging current which is supplied through the conductive transistor and leads to its rapid break-down. According to the invention, however, the path of this charging current is through the supplementary circuit containing an inductor so that charging of the capacitor will take much longer and the transistor will not be damaged.
Another advantage of the supplementary circuit resides in the fact that the single supplementary circuit will not only in any case suffice for two transistors with associated protective circuits but can be used for additional transistors with associated protective circuits. The inductor can also have additional functions.
Normal operation of the inverter circuit is in no way affected by the inductor because its D.C. resistance is very low. It is, however, desirable to have a branch which bridges the inductor and contains a diode poled opposite to the pass direction of the transistors. In this way one obtains a circuit through which the inductor current can die away during the dead period.
A resistor may be in series with the diode in the bridging branch. This permits the time constant of the dying-away process to be set.
lf the resistor is not too large, it may also be in series with the inductor and this series circuit bridged by the diode.
It is an advantage if the supplementary circuit is provided between one of the D.C.
supply leads and one end of the series circuit of a pair of transistors. In this way there will be no influence on the output circuit of the two transistors and the output circuit can be of conventional form. If two or more pairs of transistors are provided, it is advisable for the supplementary circuit to be in a lead common to the pairs. One supplementary circuit will then suffice for all transistors and associated protective circuits.
Inverter circuits constructed in accordance with the invention will now be described by way of example only with reference to the accompanying drawing, in which: Fig. 1 is the circuit diagram of a two-phase inverter with earthed centre point and, Fig. 2 is the circuit diagram of a three phase inverter.
In Fig. 1 a regulatable D.C. voltage supply 1 of output voltage U is provided from which there extend a supply lead 2 for the positive D.C. voltage, a supply lead 3 for the negative D.C. voltage and an earthed central connection 4.
A first transistor Trl and a second transistor Tr2 have their collector-emitter paths connected in series. The base-emitter path of each transistor is bridged by a respective one of resistors R1 and R2. If a control voltage is applied to two control signal terminals K1 and K2 provided at respective ends of the resistor R1, transistor Trl will become conductive. If the control signal is absent, the transistor Trl is non-conductive. Similar control signal terminals are provided for the transistor Tr2, and control signals are applied alternately to the two transistors and there is a dead period after each application.
An output 5 is taken from the junction of the transistors and between the output and earth an A.C. load 6 is connected.
In parallel with the transistor Trl there is an auxiliary or protective circuit 7 and in parallel with the transistor Tr2 an auxiliary or protective circuit 8. The auxiliary circuit 7 consists of capacitor Cl in series with the parallel combination of a resistor R3 and a diode D1 which has the same current-pass direction as the transistor Trl. The auxiliary circuit 8 has the same configuration and comprises a capacitor C2, a resistor R4 and a diode D2.
In series with the circuit as described comprising the pair of transistors Trl and Tr2, there is a supplementary circuit 9 having an inductor or choke L and a shunt network comprising a resistor R5 and a diode D3 of which the current-pass direction is opposite to that of the transistors.
Assuming that in operation the transistor Trl is conductive and the transistor Tr2 is non-conductive, then in this condition the capacitor C1 is chargd to only a very low voltage but the capacitor C2 is charged to almost the full D.C. voltage U. If, now, the transistor Trl is turned OFF, its emitter current will cease comparatively rapidly. On the other hand, the collector-emitter voltage will rise more slowly because this takes place in response to the charge on the capacitor Cl.
Accordingly, the power converted in the transistor Trl on switching off is so low that the transistor cannot be damaged.
Within the dead period there is a distribution of the voltage such that approximately U/2 is applied to both capacitors Cl and C2.
If, now, the transistor Tr2 becomes conductive then, in the absence of the supplementary circuit 9, substantially the full D.C. voltage U would be applied to the capacitor C1. A strong charging current would flow through the transistor Tr2 and most likely damage it.
By reason of the choke L in the supplementary circuit 9, the charging of the capacitor C1 is retarded. The corresponding charging current can be kept so low that the transistor Tr2 does not become damaged.
On turning OFF the transistor Tr2, the conditions are repeated as already described in conjunction with turning-OFF of the transistor Trl. The current then still flowing in the choke L is short-circuited through the resistor R5 and the diode D3 so that the choke current drops rapidly and, on switching the transistor Trl on, the choke is again able to keep the charging current sufficiently low, this time for the capacitor C2.
In the Fig. 2 embodiment, the same reference numerals as in Fig. 1 are used for corresponding components. Figure 2 shows a three-phase inverter and therefore three pairs of transistors Trl, Tr2; Tr3, Tr4; and Tr5, Tr6 are provided, each transistor having a respective associated auxiliary circuit such as those. referenced 7 and 8. All three pairs of transistors have a common protective circuit 9.
In this protective circuit, a sensor resistor R6 is in series with the choke L. A measuring signal i corresponding to the direct current flowing through the inverter can be taken from across this resistor. The senses circuit L and R6 is bridged by the diode D3.
Three outputs SU, SV and SW are provided to which a three-phase load such as an asynchronous motor can be connected.
Further, diodes D4 to D9 are provided each in parallel with a respective transistor. The diodes D4, D6 and D8 are provided directly between a respective output and the positive supply lead 2, the diodes D5, D7 and D9 are privided between a respective output and a point 10 of the negative supply lead 3 located between the voltage supply 1 and the supplementary circuit 9.
WHAT WE CLAIM IS:- 1. An inverter circuit comprising: a pair of terminals for connection to a D.C.
supply, one or more pairs of switching transistors, the two transistors of the (or any particular) pair being connected in series with each other between the terminals, means to switch the transistors selectively to derive an A.C. output from the D.C. supply by switching ON the transistors of the (or any particular) pair alternately with a dead period between switching OFF one transistor of a pair and switching ON the other transistor of the pair, a respective protective circuit connected in parallel with each switching transistor, each protective circuit comprising a capacitor in series with the parallel combination of an ohmic resistor and a diode poled in the same direction as current flow through the switching transistor, and just one supplementary protection circuit including an inductor connected in series with the said one or more pairs of switching transistors to limit the charging current of the capacitor in each protective circuit.
2. A circuit as claimed in claim 1, wherein the supplementary protection circuit includes a diode poled in the opposite direction to current flow through the switching transistors connected in parallel with the inductor.
3. A circuit as claimed in claim 2, wherein the serial combination of the lastmentioned diode and a resistor is connected in parallel with the inductor.
4. A circuit as claimed in any preceding claim, wherein just one pair of switching transistors is provided, and their collectoremitter paths are in series with the supplementary protection circuit connected between one of the terminals and one end of the serially-connected collector-emitter paths.
5. A circuit as claimed in any of claims 1 to 3, wherein two or more pairs of switching transistors are provided, and the collectoremitter paths of the transistors of any one pair are connected in series with the supplementary protection circuit connected between one of the terminals and a common connection to one end of each pair of seriallyconnected collector-emitter paths.
6. An inverter circuit substantially as herein described with reference to, and as illustrated by, Figure 1 of the accompanying drawings.
7. An inverter circuit substantially as herein described with reference to, and as illustrated by, Figure 2 of the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. able to keep the charging current sufficiently low, this time for the capacitor C2. In the Fig. 2 embodiment, the same reference numerals as in Fig. 1 are used for corresponding components. Figure 2 shows a three-phase inverter and therefore three pairs of transistors Trl, Tr2; Tr3, Tr4; and Tr5, Tr6 are provided, each transistor having a respective associated auxiliary circuit such as those. referenced 7 and 8. All three pairs of transistors have a common protective circuit 9. In this protective circuit, a sensor resistor R6 is in series with the choke L. A measuring signal i corresponding to the direct current flowing through the inverter can be taken from across this resistor. The senses circuit L and R6 is bridged by the diode D3. Three outputs SU, SV and SW are provided to which a three-phase load such as an asynchronous motor can be connected. Further, diodes D4 to D9 are provided each in parallel with a respective transistor. The diodes D4, D6 and D8 are provided directly between a respective output and the positive supply lead 2, the diodes D5, D7 and D9 are privided between a respective output and a point 10 of the negative supply lead 3 located between the voltage supply 1 and the supplementary circuit 9. WHAT WE CLAIM IS:-
1. An inverter circuit comprising: a pair of terminals for connection to a D.C.
supply, one or more pairs of switching transistors, the two transistors of the (or any particular) pair being connected in series with each other between the terminals, means to switch the transistors selectively to derive an A.C. output from the D.C. supply by switching ON the transistors of the (or any particular) pair alternately with a dead period between switching OFF one transistor of a pair and switching ON the other transistor of the pair, a respective protective circuit connected in parallel with each switching transistor, each protective circuit comprising a capacitor in series with the parallel combination of an ohmic resistor and a diode poled in the same direction as current flow through the switching transistor, and just one supplementary protection circuit including an inductor connected in series with the said one or more pairs of switching transistors to limit the charging current of the capacitor in each protective circuit.
2. A circuit as claimed in claim 1, wherein the supplementary protection circuit includes a diode poled in the opposite direction to current flow through the switching transistors connected in parallel with the inductor.
3. A circuit as claimed in claim 2, wherein the serial combination of the lastmentioned diode and a resistor is connected in parallel with the inductor.
4. A circuit as claimed in any preceding claim, wherein just one pair of switching transistors is provided, and their collectoremitter paths are in series with the supplementary protection circuit connected between one of the terminals and one end of the serially-connected collector-emitter paths.
5. A circuit as claimed in any of claims 1 to 3, wherein two or more pairs of switching transistors are provided, and the collectoremitter paths of the transistors of any one pair are connected in series with the supplementary protection circuit connected between one of the terminals and a common connection to one end of each pair of seriallyconnected collector-emitter paths.
6. An inverter circuit substantially as herein described with reference to, and as illustrated by, Figure 1 of the accompanying drawings.
7. An inverter circuit substantially as herein described with reference to, and as illustrated by, Figure 2 of the accompanying drawings.
GB30060/77A 1976-07-19 1977-07-18 Inverter circuits Expired GB1588135A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2632381A DE2632381B2 (en) 1976-07-19 1976-07-19 Inverter circuit

Publications (1)

Publication Number Publication Date
GB1588135A true GB1588135A (en) 1981-04-15

Family

ID=5983361

Family Applications (1)

Application Number Title Priority Date Filing Date
GB30060/77A Expired GB1588135A (en) 1976-07-19 1977-07-18 Inverter circuits

Country Status (8)

Country Link
JP (1) JPS5312028A (en)
AU (1) AU511374B2 (en)
DE (1) DE2632381B2 (en)
DK (1) DK312077A (en)
FR (1) FR2359540A1 (en)
GB (1) GB1588135A (en)
NO (1) NO146454C (en)
SE (1) SE7708282L (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4310866A (en) * 1979-09-28 1982-01-12 Borg-Warner Corporation Shootthrough fault protection system for bipolar transistors in a voltage source transistor inverter
JPS5715693U (en) * 1980-06-30 1982-01-27
JPS5992230U (en) * 1982-12-14 1984-06-22 明立精機株式会社 Air spring height control device
US4594650A (en) * 1983-04-19 1986-06-10 Mitsubishi Denki Kabushiki Kaisha Inverter device
DE3429488A1 (en) * 1984-08-10 1986-02-20 Danfoss A/S, Nordborg ELECTRONIC SWITCHING DEVICE

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3737755A (en) * 1972-03-22 1973-06-05 Bell Telephone Labor Inc Regulated dc to dc converter with regulated current source driving a nonregulated inverter

Also Published As

Publication number Publication date
SE7708282L (en) 1978-01-20
JPS5312028A (en) 1978-02-03
JPS5628104B2 (en) 1981-06-29
FR2359540A1 (en) 1978-02-17
NO772362L (en) 1978-01-20
DE2632381B2 (en) 1980-10-30
AU511374B2 (en) 1980-08-14
NO146454B (en) 1982-06-21
DK312077A (en) 1978-01-20
DE2632381A1 (en) 1978-01-26
AU2706277A (en) 1979-01-18
NO146454C (en) 1982-09-29

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Legal Events

Date Code Title Description
PS Patent sealed [section 19, patents act 1949]
PCNP Patent ceased through non-payment of renewal fee