Drive device driving a plurality of semiconductor elements having respective reference potential electrodes coupled via a main electrode unit and alternating current power supply device provided with the drive device

A first bypass circuit has first and second nodes. The first load circuit is connected between the first node and a signal input terminal of the second drive circuit. The second load circuit has substantially the same impedance as the first load circuit, and is connected between the second node and the reference potential terminal of the second drive circuit. The first drive circuit has the same reference potential as the input buffer. The second bypass circuit passes a signal of a predetermined frequency or higher between a current path formed between the first load circuit and the signal input terminal of the second drive circuit and a current path formed between the second load circuit and the reference potential terminal of the second drive circuit. The first bypass circuit passes a signal of a predetermined frequency or higher between the first and second nodes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drive device and an alternating current (hereafter, also referred to as AC) power supply device provided with the drive device, and particularly to a drive device driving a plurality of semiconductor elements having respective reference potential electrodes coupled via a main electrode unit as well as an AC power supply device provided with the drive device.

2. Description of the Background Art

A drive device driving semiconductor elements may include, e.g., a plurality of semiconductor elements coupled in parallel. In this structure, a parasitic inductance is present in each of interconnections between the semiconductor elements. Therefore, when the semiconductor element performs a switching operation to supply intermittently an output current, an induced electromotive force occurs in a parasitic inductance.

In a general power semiconductor element, a change rate of current at the time of switching is about 3000 A/μs. Therefore, when the parasitic inductance is 10 nH (nanohenry), the induced electromotive force is equal to (10 n×3000/1μ=30 (V)). This induced electromotive force destroys the semiconductor element, and causes a malfunction of circuits.

International Publication No. WO 01/001555 brochure, Japanese Patent Laying-Open Nos. 2001-043990, 2006-229454, 2003-339152 and 2001-045740, and International Publication No. WO 01/089090 brochure (publications 1-6) have disclosed structures driving semiconductor elements, and particularly structures for preventing a large voltage such as an induced electromotive force that may instantaneously occurs, and thereby preventing destruction and malfunctions of circuits.

For example, the publication1has disclosed the following structure. In a power conversion circuit that converts a direct current into an alternating current or the like to supply a power to a load, the disclosed structure aims to prevent a malfunction and destruction due to a surge voltage. This structure includes a level shift circuit that is arranged corresponding to a switching semiconductor element forming a main circuit, and performs level shifting of a reference potential on an output side in a manner following variations in reference potential of the switching semiconductor element. A control signal is transmitted via the level shift circuit to the switching semiconductor element. A direct current control power supply supplying the power to the level shift circuit is connected to a negative pole of the switching semiconductor element via at least one of the inductance and the resistance.

The publication 2 has disclosed the following structure. An output terminal of a bridge drive circuit is connected to gate terminals of four MOS transistors in an H-bridge circuit via resistances. At least one of four MOS transistor drive circuits has an output terminal connected to an interconnection providing a negative-side reference potential via a capacitor. By this structure, an integrating circuit formed of the resistance and the capacitor operates as a filter to prevent application of a high voltage to the MOS transistor drive circuit.

However, the publications 1-6 have not disclosed a structure that is employed in a drive device driving, based on a common drive control signal, a plurality of semiconductor elements having respective reference potential electrodes coupled via a main electrode unit, and reduces an influence of an induced electromotive force caused by a switching operation of the semiconductor element.

SUMMARY OF THE INVENTION

An object of the invention is to provide a drive device that drives, based on a common drive control signal, a plurality of semiconductor elements having respective reference potential electrodes coupled via a main electrode unit, and can reduce an influence of an induced electromotive force caused by a switching operation of the semiconductor element, and is to provided an AC power supply device provided with the drive device.

A drive device according to an aspect of the invention is a drive device driving first and second semiconductor elements having respective reference potential electrodes coupled via a main electrode unit, and includes an input buffer receiving a drive control signal; a first bypass circuit including first and second nodes, receiving an output signal of the input buffer and providing a signal from the first node; a first drive circuit including a reference potential terminal coupled to a reference potential electrode of the input buffer, the second node of the first bypass circuit and the reference potential electrode of the first semiconductor element, and a signal input terminal receiving the output signal from the first node of the first bypass circuit, and supplying a voltage to a control electrode of the first semiconductor element; a second drive circuit including a reference potential terminal coupled to the second node of the first bypass circuit and the reference potential electrode of the second semiconductor element, and a signal input terminal receiving the output signal form the first node of the first bypass circuit, and supplying a voltage to a control electrode of the second semiconductor element; a first load circuit connected between the first node of the first bypass circuit and the signal input terminal of the second drive circuit; a second load circuit having substantially the same impedance as the first load circuit, and connected between the second node of the first bypass circuit and the reference potential terminal of the second drive circuit; and a second bypass circuit passing a signal of a predetermined frequency or higher between a current path formed between the first load circuit and the signal input terminals of the second drive circuit and a current path formed between the second load circuit and the reference potential terminal of the second drive circuit. The first bypass circuit passes a signal of a predetermined frequency or higher between the first and second nodes.

An AC power supply device according to an aspect of the invention, includes a main electrode unit; first and second semiconductor elements having respective reference potential electrodes coupled via the main electrode unit; an input buffer receiving a drive control signal; a first bypass circuit including first and second nodes, receiving an output signal of the input buffer and providing a signal from the first node; a first drive circuit including a reference potential terminal coupled to a reference potential terminal of the input buffer, the second node of the first bypass circuit and the reference potential electrode of the first semiconductor element, and a signal input terminal receiving an output signal from the first node of the first bypass circuit, and supplying a voltage to a control electrode of the first semiconductor element; a second drive circuit including a reference potential terminal coupled to the second node of the first bypass circuit and the reference potential electrode of the second semiconductor element, and a signal input terminal receiving the output signal from the first node of the first bypass circuit, and supplying a voltage to a control electrode of the second semiconductor element; a first load circuit connected between the first node of the first bypass circuit and the signal input terminal of the second drive circuit; a second load circuit having substantially the same impedance as the first load circuit, and connected between the second node of the first bypass circuit and the reference potential terminal of the second drive circuit; and a second bypass circuit passing a signal of a predetermined frequency or higher between a current path formed between the first load circuit and the signal input terminal of the second drive circuit and a current path formed between the second load circuit and the reference potential terminal of the second drive circuit. The first bypass circuit passes a signal of a predetermined frequency or higher between the first and second nodes.

According to the invention, the plurality of semiconductor elements having respective reference potential electrodes coupled via the main electrode unit are driven based on the common drive control signal, and an influence of an induced electromotive force caused by the switching operation of the semiconductor elements can be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will now be described with reference to the drawings. In the figures, the same or corresponding portions bear the same reference numbers, and description thereof is not repeated.

First Embodiment

[Structure and Basic Operation]

FIG. 1is a circuit diagram showing a structure of an AC power supply device201according to a first embodiment of the invention.

Referring toFIG. 1, AC power supply device201includes a drive device101, switch elements (first to third semiconductor elements)11-13, diodes D11-D13, a collector main electrode terminal TC and an emitter main electrode terminal TE. Drive device101includes low-pass filters1-3, a drive circuit (first drive circuit)5, a drive circuit (second drive circuit)6, a drive circuit (second drive circuit)7, an input buffer8, a bypass circuit (first bypass circuit)9, a power supply VD1, common mode inductors L1and L2, and capacitors C1, C4, C6and C8. Bypass circuit9includes a low-pass filter4. Low-pass filter (first low-pass filter)1includes a resistance R4and a capacitor C7. Low-pass filter (second low-pass filter)2includes a resistance (first load circuit) R1, a resistance (second load circuit) R2and a capacitor (second bypass circuit) C3. Low-pass filter3includes a resistance (first load circuit) R5, a resistance (second load circuit) R6and a capacitor (second bypass circuit) C9. Low-pass filter4includes a resistance R3and a capacitor C5. Bypass circuit9includes a node N1corresponding to a connection node of a second end of resistance R3and a first end of capacitor C5, and also includes a node N2corresponding to a second end of capacitor C5.

Each of switch elements11-13has a control emitter CE and a current output emitter IE (i.e., emitter for current output) as will be described later with reference toFIG. 2. Control emitter CE of the switch element is employed for controlling a voltage supplied to the gate electrode of the switch element, and current output emitter IE is employed for passing a large current. In the following descriptions, control emitter CE and current output emitter IE may be generally referred to as “emitters” hereinafter.

Resistance R3has a first end connected to an output terminal of input buffer8and a second end connected to a first end of capacitor C5, a first end of resistance R4, a first end of resistance R1and a first end of resistance R5. A second end of resistance R1is connected to a first end of capacitor C3and a signal input terminal of drive circuit6. A reference potential terminal TREF of drive circuit6is connected to emitters of switch elements11-13, a second end of capacitor C1, a second end of capacitor C3and a second end of resistance R2. A second end of resistance R4is connected to a first end of capacitor C7and a signal input terminal of drive circuit5. A reference potential terminal TREF of drive circuit5is connected to emitters of switch elements11-13, a second end of capacitor C4, a second end of capacitor C5, a second end of capacitor C7, a reference potential terminal TREF of input buffer8, a first end of resistance R2, a first end of resistance R6, a second end of capacitor C6and a negative electrode of power supply VD1. A second end of resistance R5is connected to a first end of capacitor C9and a signal input terminal of drive circuit7. Reference potential terminal TREF of drive circuit7is connected to emitters of switch elements11-13, a second end of capacitor C8, a second end of capacitor C9and a second end of resistance R6.

Collectors of switch elements11-13are connected to cathodes of diodes D11-D13, respectively. Emitters of switch elements11-13are connected to anodes of diodes D11-D13, respectively.

A power supply terminal TP of drive circuit5, a first end of capacitor C4, a power supply terminal TP of input buffer8and a first end of capacitor C6are connected to a positive electrode of power supply VD1. A power supply end TP of drive circuit6and a first end of capacitor C1are connected to the positive electrode of power supply VD1via a common mode inductor L1. Reference potential terminal TREF of drive circuit6and the second end of capacitor C1are connected to a negative electrode of power supply VD1via common mode inductor L1. A power supply terminal TP of drive circuit7and a first end of capacitor C8are connected to the positive electrode of power supply VD1via a common mode inductor L2. Reference potential terminal TREF of drive circuit7and the second end of capacitor C8are connected to the negative electrode of power supply VD1via common mode inductance L2. More specifically, common mode inductor L1is arranged between power supply VD1and drive circuit6. Common mode inductor L2is arranged between power supply VD1and drive circuit7. Output terminals of drive circuits5,6and7are connected to gates (control electrodes) of switch elements11,12and13, respectively. Although drive device101has common mode inductors L1and L2, it may have another structure. Drive device101may have a structure employing two inductors instead of common mode inductors L1and L2, respectively.

Drive device101drives switch elements11-13based on an externally provided drive control signal DRV.

Input buffer8externally receives drive control signal DRV, and amplifies drive control signal DRV so that the voltage amplitude of drive control signal DRV may take a value required for driving switch elements11-13.

Low-pass filter4in bypass circuit9attenuates frequency components of a predetermined frequency or higher among frequency components of drive control signal DRV, i.e., an output signal of input buffer8. Bypass circuit9distributes drive control signal DRV passed through low-pass filter4to low-pass filters1-3via node N1.

Low-pass filter1is connected between node N1of bypass circuit9and the signal input terminal of drive circuit5. Low-pass filter2is connected between node N1of bypass circuit9and the signal input terminal of drive circuit6. Low-pass filter3is connected between node N1of bypass circuit9and the signal input terminal of drive circuit7. Each of low-pass filters1-3attenuates frequency components of a predetermined frequency or higher among the frequency components of drive control signal DRV received from bypass circuit9.

Each of low-pass filters1-4may include an inductance instead of the resistance.

Drive circuits5-7receive drive control signal DRV passed through low-pass filters1-3, and provide voltages to gates of switch elements11-13, respectively. Drive circuits5-7, for example, do not amplify the voltage of drive control signal DRV in contrast to input buffer8. Thus, drive circuits5-7have a voltage gain of one. Drive circuits5-7can drive loads of low impedances, for example, because output resistances thereof are small.

Switch elements11-13are connected in parallel. More specifically, each collector of switch elements11-13is connected to collector main electrode terminal TC, and each emitter (reference potential electrode) thereof is connected to emitter main electrode terminal TE. Switch elements11-13are switched between the on and off states based on drive control signal DRV received from drive circuits5-7, respectively.

Bypass circuit9couples reference potential terminals TREF of drive circuits5and6via resistance R2.

Resistance R1is connected between node N1of bypass circuit9and the signal input terminal of drive circuit6. Resistance R2has substantially the same impedance as resistance R1, and is connected between node N2of bypass circuit9and the reference potential terminal of drive circuit6.

Capacitor C3passes a signal of a predetermined frequency or higher between the second end, i.e., the end on the drive circuit6side of resistance R1and the second end, i.e., the end on the drive circuit6side of resistance R2. Thus, capacitor C3passes the signal of the predetermined frequency or higher between a current path formed between resistance R1and the signal input terminal of drive circuit6and a current path formed between resistance R2and the reference potential terminal of drive circuit6.

Resistance R4is connected between node N1of bypass circuit9and the signal input terminal of drive circuit5.

Bypass circuit9passes a signal of a predetermined frequency or higher between the first end, i.e., the end on the bypass circuit9side of resistance R1and the first end, i.e., the end on the bypass circuit9side of resistance R2. Thus, bypass circuit9passes the signal of the predetermined frequency or higher between nodes N1and N2.

Bypass circuit9couples reference potential terminals TREF of drive circuits5and7via resistance R6.

Resistance R5is connected between node N1of bypass circuit9and the signal input terminal of drive circuit7. Resistance R6has substantially the same impedance as resistance R5, and is connected between node N2of bypass circuit9and the reference potential terminal of drive circuit7.

Capacitor C9passes a signal of a predetermined frequency or higher between the second end, i.e., the end on the drive circuit7side of resistance R5and the second end, i.e., the end on the drive circuit7side of resistance R6. Thus, capacitor C9passes the signal of the predetermined frequency or higher between the current path formed between resistance R5and the signal input terminal of drive circuit7and the current path formed between resistance R6and the reference potential terminal of drive circuit7.

Bypass circuit9passes a signal of a predetermined frequency or higher between the first end, i.e., the end on the bypass circuit9side of resistance R5and the first end, i.e., the end on the bypass circuit9side of resistance R6. Thus, bypass circuit9passes the signal of the predetermined frequency or higher between nodes N1and N2.

FIG. 2shows a structure of AC power supply device201according to the first embodiment of the invention.

Referring toFIG. 2, AC power supply device201includes drive device101and an insulated circuit board SUB2.

Insulated circuit board SUB2is formed of, e.g., a ceramic substrate provided at its opposite surfaces with metal patterns, respectively. More specifically, metal patterns P1and P2are formed on one of main surfaces of insulated circuit board SUB2. A semiconductor chip forming switch elements11-13, a semiconductor chip forming diodes D11-D13and a collector main electrode terminal TC are arranged on metal pattern P1. Emitter main electrode terminal TE is arranged on Metal pattern P2.

The output terminal of drive circuit5is connected to a gate G of switch element11, e.g., via an aluminum wire W11. Reference potential terminal TREF of drive circuit5and control emitter CE of switch element11are connected, e.g., via an aluminum wire W21.

Current output emitter IE of switch element11, the anode of diode D11and metal pattern P2are connected via three aluminum wires W1A, W1B and W1C.

Likewise, the output terminal of drive circuit6and gate G of switch element12are connected, e.g., via an aluminum wire W12. Reference potential terminal TREF of drive circuit6and control emitter CE of switch element12are connected, e.g., via an aluminum wire W22.

Current output emitter IE of switch element12, the anode of diode D12and metal pattern P2are connected, e.g., via three aluminum wires W2A, W2B and W2C.

Likewise, the output terminal of drive circuit7and gate G of switch element13are connected, e.g., via an aluminum wire W13. Reference potential terminal TREF of drive circuit7and control emitter CE of switch element13are connected, e.g., via an aluminum wire W23.

Current output emitter IE of switch element13, the anode of diode D13and metal pattern P2are connected, e.g., via three aluminum wires W3A, W3B and W3C.

The number of aluminum wires connecting current output emitters IE of the switch elements, the anodes of diodes and metal pattern P2are appropriately determined according to a current quantity and the like.

Emitter main electrode terminal TE, aluminum wires W1A, W1B, W1C, W2A, W2B, W2C, W3A, W3B and W3C, and metal pattern P2form an emitter main electrode unit MEU of AC power supply device201. Thus, current output emitters IE of switch elements11,12and13are connected via emitter main electrode unit MEU.

Collectors of switch elements11,12and13, cathodes of diodes D11, D12and D13, and collector main electrode terminal TC are connected via metal pattern P1.

When the induced electromotive force occurs in parasitic inductance LP1of AC power supply device201according to a first embodiment of the invention, the operation is performed as follows.

In the following description, it is assumed that the induced electromotive force that occurs in parasitic inductance LP1has an angular frequency of ω, resistances R1-R6have resistance values of R1-R6, respectively, and capacitors C1-C9have capacitance values of C1-C9, respectively.

Reference potential terminal TREF of drive circuit6is connected to control emitter CE of switch element12. Therefore, when an induced electromotive force occurs in parasitic inductance LP1, a potential difference VS corresponding to the induced electromotive force occurs between the reference potential of drive circuit6and the reference potential of input buffer8. This potential difference VS causes a surge current IS to flow between the reference potential of drive circuit6and the reference potential of input buffer8. Surge current IS caused by the induced electromotive force that occurs in parasitic inductance LP1flows through a path extending through switch element12, drive circuit6, low-pass filter2, low-pass filter1, drive circuit5and switch element11in this order as shown inFIG. 1.

In drive device101, the resistance values of resistances R1and R2as well as the capacitance values of capacitors C3and C5are set to satisfy relationships of (R1=R2), ((1/(ω×C3))<<R1) and ((1/(ω×C5))<<R1). Thereby, the values of surge currents flowing through respective resistances R1and R2become substantially equal to each other, and the values of voltage step-down caused in the respective resistances R1and R2by surge current IS become substantially equal to each other.

Owing to the above structure, drive control signal DRV received by drive circuit6does not change even when the induced electromotive force occurs in parasitic inductance LP1, and it is possible to prevent the switching operation of switch element12from being affected by the induced electromotive force.

Since the resistance values of resistances R1and R2are much larger than the interconnection resistance value of the path of surge current IS, the voltage corresponding to potential difference VS caused by the induced electromotive force between the reference potential of input buffer8and the reference potential of drive circuit6can be substantially entirely applied to resistances R1and R2. Therefore, it is possible to prevent a malfunction and destruction of switch element12, drive circuit6and input buffer8.

Then, description will be given on an operation performed when the induced electromotive force occurs in parasitic inductance LP2of AC power supply device201according to the first embodiment of the invention.

Reference potential terminal TREF of drive circuit7is connected to control emitter CE of switch element13. Therefore, when the induced electromotive force occurs in parasitic inductance LP2, potential difference VS corresponding to the induced electromotive force occurs between the reference potential of drive circuit7and the reference potential of input buffer8. This potential difference VS causes surge current IS to flow between the reference potential of drive circuit7and the reference potential of input buffer8. Surge current IS caused by the induced electromotive force that occurs in parasitic inductance LP2flows through a path extending through switch element13, drive circuit7, low-pass filters3and1, drive circuit5and switch element11in this order.

In low-pass filter4of drive device101, the resistance values of resistances R5and R6as well as the capacitance values of capacitors C9and C5are set to satisfy relationships of (R5=R6), ((1/(ω×C9))<<R5) and ((1/(ω×C5))<<R5). Thereby, the values of surge currents flowing through respective resistances R5and R6become substantially equal to each other, and the values of voltage step-down caused in respective resistances R5and R6by surge current IS become substantially equal to each other.

Owing to the above structure, drive control signal DRV received by drive circuit7does not change even when the induced electromotive force occurs in parasitic inductance LP2, and it is possible to prevent the switching operation of switch element13from being affected by the induced electromotive force.

Since the resistance values of resistances R5and R6are much larger than the interconnection resistance value of the path of surge current IS, the voltage corresponding to potential difference VS caused by the induced electromotive force between the reference potential of input buffer8and the reference potential of drive circuit7can be applied substantially entirely to resistances R5and R6. Therefore, it is possible to prevent a malfunction and destruction of switch element13, drive circuit7and input buffer8.

The publications 1-6 have not disclosed the structure that causes the plurality of semiconductor elements connected in parallel to perform the switching operation according to the same timing, i.e., to perform switching between the on and off states according to the same timing.

In drive device101, however, the resistance values and the capacitance values are set to satisfy a relationship, e.g., of ((R1+R2)×C3=R4×C7=(R5+R6)×C9). Thus, the time constants of low-pass filters1-3are set equal to each other. According to this structure, drive control signal DRV is transmitted from the output of bypass circuit9to the signal input terminals of drive circuits5-7with delays of the same time, respectively, and the switching operations of switch elements11-13based on drive control signal DRV can be performed according to the same timing.

Low-path filter4in drive device101is configured to have the resistance value and the capacitance value satisfying a relationship, e.g., of ((1/(ω×C5))<<R3). This structure can prevent surge current IS from flowing to the output terminal of input buffer8, and the malfunction and destruction of input buffer8can be prevented.

The reference potential of drive circuit5is the same as that of input buffer8. Owing to this structure, drive control signal DRV received from input buffer8does not change even when the induced electromotive force occurs in parasitic inductance LP3, and it is possible to prevent the switching operation of switch element11from being affected by the induced electromotive force.

The publications 1-6 have not disclosed the structure reducing the influence of the induced electromotive force caused by the switching operations of the semiconductor elements in the drive device that drives, based on the common drive control signal, the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit.

However, the drive device according to the first embodiment of the invention can operate with respect to the induced electromotive force occurring, e.g., in parasitic inductance LP1such that capacitor C3passes the signal of the predetermined frequency or higher between the current path formed between resistance R1and the signal input terminal of drive circuit6and the current path formed between resistance R2and the reference potential terminal of drive circuit6. Also, resistance R2has substantially the same impedance as resistance R1.

As described above, the surge current caused by the induced electromotive force occurring in parasitic inductance LP1flows through the current path between node N1of bypass circuit9and the signal input terminal of drive circuit6as well as the current path that has substantially the same impedance as the above current path and is formed between node N2of bypass circuit9and the reference potential terminal of drive circuit6. Thereby, it is possible to prevent variations in drive control signal received by drive circuit6.

In the drive device according to the first embodiment of the invention, the reference potential of drive circuit5is the same as that of input buffer8. This structure can prevent the variations in drive control signal received by drive circuit5from input buffer8even when the induced electromotive force occurs in parasitic inductance LP3. According to the drive device of the first embodiment of the invention, therefore, the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit can be driven based on the common drive control signal, and the influence of the induced electromotive force caused by the switching operation of the semiconductor device can be reduced. Thereby, it is possible to improve flexibility in arrangement of each switch element and flexibility relating to the interconnections.

The publications 1-6 have not disclosed the structure that includes the input buffer receiving the drive control signal and the plurality of drive circuits driving the plurality of semiconductor elements having the respective reference potential electrodes coupled together based on the output signal of the input buffer, and is configured such that the common potential of at least one of the plurality of drive circuits is the same as the reference potential of the input buffer.

For example, in the drive device, it is assumed that the semiconductor element is internally provided with an element for current sensing, and a sensing circuit monitors a current flowing through the semiconductor element. In general, the drive device externally provides a result of monitoring by the sensing circuit. Therefore, the reference potential of the sensing circuit must be equal to the reference potential of the input buffer. If the reference potential of the input buffer is different from that of the drive circuit, the semiconductor element has the reference potential different from that of the sensing circuit. The difference in reference potential between the semiconductor element and the sensing circuit causes an error in the current sensing result.

However, in the drive device according to the first embodiment of the invention, the reference potential of drive circuit5is the same as that of input buffer8as already described. Owing to this structure, the current flowing through the semiconductor element and the like can be accurately measured by a unit or the like outside the drive device.

Even when it is assumed that drive device101does not have common mode inductances L1and L2, and when the induced electromotive force occurs in parasitic inductance LP1, the induced electromotive force causes the surge current to pass through the path extending through the emitter of switch element12, reference potential terminal TREF of drive circuit6, power supply VD1, capacitor C6, reference potential terminal TREF of drive circuit5and the emitter of switch element11in this order. This surge current causes problems such as a malfunction and destruction of circuits due to crosstalk and voltage step-down in drive device101.

However, in drive device101according to the first embodiment of the invention, the structure provided with common mode inductances L1and L2can prevent the current caused by the induced electromotive force from flowing through the foregoing path. Thus, drive circuits5-7can share one power supply VD1, and the influence of the induced electromotive force caused in the parasitic inductance can be prevented.

Another embodiment of the invention will now be described with reference to the drawings. The corresponding portions bear the same reference numbers, and description thereof is not repeated.

Second Embodiment

A second embodiment relates to a drive device that is different from the drive device according to the first embodiment in that the drive device additionally includes a circuit for preventing flow of a surge current to an input terminal of the drive circuit

FIG. 3is a circuit diagram showing a structure of an AC power supply device202according to the second embodiment of the invention.

Referring toFIG. 3, a drive device102according to the second embodiment of the invention further includes resistances R11-R13, which are not employed in drive device101of the first embodiment of the invention.

Resistance (third load circuit) R11is connected between the first end of capacitor C3and the signal input terminal of drive circuit6. Resistance (fourth load circuit) R12is connected between the first end of capacitor C7and the signal input terminal of drive circuit5. Resistance (third load circuit) R13is connected between the first end of capacitor C9and the signal input terminal of drive circuit7.

In a high frequency range, the input capacitance of the drive circuit lowers the input impedance of the drive circuit. In drive device102, when the induced electromotive force occurs in parasitic inductance LP1, the surge current flows into drive circuit6via an input impedance Z1of drive circuit6so that drive circuit6may malfunction or break. When the induced electromotive force occurs in parasitic inductance LP2, the surge current flows into drive circuit7via an input impedance Z2of drive circuit7so that drive circuit7may malfunction or break. When the induced electromotive force occurs in parasitic inductance LP3, the surge current flows into drive circuit5via an input impedance Z3of drive circuit5so that drive circuit5may malfunction or break.

It is assumed that resistances R11-R13have the resistance values of R11-R13, respectively, and capacitors C3, C7and C9have the capacitance values of C3, C7and C9, respectively. In drive device102, the resistance values and the capacitance values are set to satisfy relationships of ((1/(ω×C3))<<R11), ((1/(ω×C7))<<R12) and ((1/(ω×C9))<<R13)).

Since the above structure can prevent the surge current from flowing to the input terminals of drive circuits5-7, the malfunction and destruction of drive circuits5-7can be prevented.

Other structures and operations are the same as those of the drive device according to the first embodiment, and therefore description thereof is not repeated.

Similarly to the drive device according to the first embodiment of the invention, therefore, the drive device according to the second embodiment of the invention drives the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit based on the common drive control signal, and can reduce the influence of the induced electromotive force caused by the switching operation of the semiconductor elements.

Still another embodiment of the invention will now be described with reference to the drawings. The corresponding portions bear the same reference numbers, and description thereof is not repeated.

Third Embodiment

This embodiment relates to a drive device that differs from the drive device according to the first embodiment in circuit structure between bypass circuit9and drive circuits5-7.

[Structure and Basic Operation]

FIG. 4is a circuit diagram showing an AC power supply device203according to a third embodiment of the invention.

Referring toFIG. 4, AC power supply device203according to the third embodiment of the invention includes a drive device103, switch elements (first to third semiconductor elements)11-13, collector main electrode terminal TC and emitter main electrode terminal TE. Drive device103includes common mode choke coils L3and L4, drive circuits5-7, input buffer8, bypass circuit (first bypass circuit)9, power supply VD1, common mode inductances L1and L2, capacitor (second bypass circuit) C3, capacitor (second bypass circuit) C9and capacitors C1, C4, C6and C8. Common mode choke coil L3includes choke coils L11and L12. Common mode choke coil L4includes choke coils L13and L14. Bypass circuit9has node N1corresponding to a connection node of the second end of resistance R3and the first end of capacitor C5, and node N2corresponding to a connection node of the second end of capacitor C5.

The first end of resistance R3is connected to the output terminal of input buffer8, and the second end thereof is connected to the first end of capacitor C5, the signal input terminal of drive circuit5, a first end of choke coil L11and a first end of choke coil L13. A second end of choke coil L11is connected to the first end of capacitor C3and the signal input terminal of drive circuit6. Reference potential terminal TREF of drive circuit6is connected to the emitters of switch elements11-13, the second end of capacitor C1, the second end of capacitor C3and a second end of choke coil L12. Reference potential terminal TREF of drive circuit5is connected to the emitters of switch elements11-13, the second end of capacitor C4, the second end of capacitor C5, reference potential terminal TREF of input buffer8, a first end of choke coil L12, a first end of choke coil L14, the second end of capacitor C6and the negative electrode of power supply VD11. A second end of choke coil L13is connected to the first end of capacitor C9and the signal input terminal of drive circuit7. Reference potential terminal TREF of drive circuit7is connected to the emitters of switch elements11-13, the second end of capacitor C8, the second end of capacitor C9and a second end of choke coil L14.

Drive device103drives switch elements11-13based on externally received drive control signal DRV.

Input buffer8externally receives and amplifies drive control signal DRV such that drive control signal DRV may have a voltage amplitude of a value required for driving switch elements11-13.

Low-pass filter4in bypass circuit9attenuates components of a predetermined frequency or higher of drive control signal DRV that is the output signal of input buffer8. Bypass circuit9distributes drive control signal DRV passed through low-pass filter4to common mode choke coils L3and L4as well as drive circuit5from node N1.

Low-pass filter4may have a structure including inductances instead of the resistances.

Drive circuits5-7receive drive control signal DRV provided from bypass circuit9and control signals DRV passed through common mode choke coils L3and L4, and provide them to the gates of switch elements11-13, respectively. Drive circuits5-7do not perform the voltage amplification of drive control signal DRV in contrast to input buffer8. Thus, drive circuits5-7have a voltage gain of one. Drive circuits5-7can drive loads of low impedances because they have, e.g., small output resistances.

Switch elements11-13are connected in parallel. More specifically, each collector thereof is connected to collector main electrode terminal TC, and each emitter (reference potential electrode) is connected to emitter main electrode terminal TE. Switch elements11-13switch the states between the on and off states based on drive control signals DRV received from drive circuits5-7, respectively.

Bypass circuit9couples reference potential terminals TREF of drive circuits5and6via choke coil L12.

Choke coil L11is connected to node N1of bypass circuit9and the signal input terminal of drive circuit6. Choke coil L12has substantially the same impedance as choke coil L11, and is connected between node N2of bypass circuit9and the reference potential terminal of drive circuit6.

Capacitor C3passes a signal of a predetermined frequency or higher between the second end, i.e., the end on the drive circuit6side of choke coil L11and the second end, i.e., the end on the drive circuit6side of choke coil L12. Thus, capacitor C3passes the signal of the predetermined frequency or higher between a current path formed between choke coil L11and the signal input terminal of drive circuit6and the current path formed between choke coil L12and the reference potential terminal of drive circuit6.

Bypass circuit9passes a signal of a predetermined frequency or higher between the first end, i.e., the end on the bypass circuit9side of choke coil L11and the first end, i.e., the end on the bypass circuit9side of choke coil L12. Thus, bypass circuit9passes the signal of the predetermined frequency or higher between nodes N1and N2.

Bypass circuit9couples reference potential terminals TREF of drive circuits5and7via choke coil L14.

Choke coil L13is connected between node N1of bypass circuit9and the signal input terminal of drive circuit7. Choke coil L14has substantially the same impedance as choke coil L13, and is connected between node N2of bypass circuit9and the reference potential terminal of drive circuit7.

Capacitor C9passes a signal of a predetermined frequency or higher between the second end, i.e., the end on the drive circuit7side of choke coil L13and the second end, i.e., the end on the drive circuit7side of choke coil L14. Thus, capacitor C9passes the signal of the predetermined frequency or higher between the current path formed between choke coil L13and the signal input terminal of drive circuit7and the current path formed between choke coil L14and the reference potential terminal of drive circuit7.

Bypass circuit9passes a signal of a predetermined frequency or higher between the first end, i.e., the end on the bypass circuit9side of choke coil L13and the first end, i.e., the end on the bypass circuit9side of choke coil L14. Thus, bypass circuit9passes the signal of the predetermined frequency or higher between nodes N1and N2.

When the induced electromotive force occurs in parasitic inductance LP1of AC power supply device203according to a third embodiment of the invention, the operation is performed as follows.

Reference potential terminal TREF of drive circuit6is connected to control emitter CE of switch element12. Therefore, when an induced electromotive force occurs in parasitic inductance LP1, potential difference VS corresponding to the induced electromotive force occurs between the reference potentials of drive circuit6and input buffer8. This potential difference VS causes surge current IS to pass between the reference potentials of drive circuit6and input buffer8. Surge current IS caused by the induced electromotive force occurring in parasitic inductance LP1flows through a path extending through switch element12, drive circuit6, common mode choke coil L3, drive circuit5and switch element11in this order.

In drive device103, surge currents IS of substantially the same current value flow to bypass circuit9through choke coils L11and L12, respectively. Therefore, surge current IS steps down the voltages by substantially the same values in choke coils L11and L12, respectively.

According to the above structure, potential difference VS between the reference potentials of drive circuit6and input buffer8can prevent variations in normal mode voltage of common mode choke coil L3. Therefore, it is possible to prevent the variations in drive control signal DRV received by drive circuit6, and it is possible to prevent the switching operation of switch element12from being affected by the induced electromotive force.

Surge currents IS flow through choke coils L11and L12in the same direction and thus to bypass circuit9. Therefore, common mode choke coil L3has a large impedance value with respect to surge current IS, and the voltage corresponding to potential difference VS that is caused between the reference potentials of input buffer8and drive circuit6by the induced electromotive force can be applied substantially entirely to common mode choke coil L3. Therefore, the malfunction and destruction of switch element12, drive circuit6and input buffer8can be prevented.

In AC power supply device203according to the third embodiment of the invention, the operation is performed as follows when the induced electromotive force occurs in parasitic inductance LP2.

Reference potential terminal TREF of drive circuit7is connected to control emitter CE of switch element13. Therefore, when the induced electromotive force occurs in parasitic inductance LP2, potential difference VS corresponding to the induced electromotive force occurs between the reference potentials of drive circuit7and input buffer8. This potential difference VS causes surge current IS to flow between the reference potentials of drive circuit7and input buffer8. Surge current IS caused by the induced electromotive force occurring in parasitic inductance LP2flows through the path extending through switch element13, drive circuit7, common mode choke coil L4, drive circuit5and switch element11in this order.

In drive device103, surge currents IS of substantially the same current values flow through choke coils L13and L14to bypass circuit9, respectively. Therefore, the values of voltage step-down caused in respective choke coils L13and L14by surge current IS are substantially equal to each other.

The above structure can prevent variations that may occur in normal mode voltage of common mode choke coil L4due to potential difference VS between the reference potentials of drive circuit7and input buffer8. Therefore, it is possible to prevent the variations in drive control signal DRV received by drive circuit7, and to prevent the switching operation of switch element13from being affected by the induced electromotive force.

Surge currents IS flow through choke coils L13and L14in the same direction and thus to bypass circuit9. Therefore, common mode choke coil L4has a large impedance value with respect to surge current IS, and the voltage corresponding to potential difference VS that is caused between the reference potentials of input buffer8and drive circuit7by the induced electromotive force can be applied substantially entirely to common mode choke coil L4. Therefore, the malfunction and destruction of switch element13, drive circuit7and input buffer8can be prevented.

Since common mode choke coils L3and L4have the impedances of substantially zero with respect to drive control signal DRV that is the normal mode signal, the times of delay of drive control signal DRV caused between the output of bypass circuit9and the respective signal input terminals of drive circuits6and7are substantially zero. Therefore, the time of delay of drive control signal DRV caused between bypass circuit9and drive circuit5, i.e., the path not including the common mode choke coil is equal to that of delay of drive control signal DRV caused between bypass circuit9and drive circuits6and7. Accordingly, switch elements11-13can perform the switching operation according to the same timing based on drive control signal DRV.

Other structures and operations are the same as those of the drive device according to the first embodiment, and therefore description thereof is not repeated.

Similarly to the drive device according to the first embodiment of the invention, therefore, the drive device according to the third embodiment of the invention drives the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit based on the common drive control signal, and can reduce the influence of the induced electromotive force caused by the switching operation of the semiconductor elements.

Yet another embodiment of the invention will now be described with reference to the drawings. The corresponding portions bear the same reference numbers, and description thereof is not repeated.

Fourth Embodiment

This embodiment relates to a drive device that differs from the drive device according to the third embodiment in that the drive device additionally includes a circuit preventing the surge current from flowing to the input terminal of the drive circuit.

FIG. 5is a circuit diagram illustrating a structure of an AC power supply circuit204according to a fourth embodiment of the invention.

Referring toFIG. 5, a drive device104according to the fourth embodiment of the invention differs from the drive device according to the third embodiment of the invention in that resistances R21and R22are additionally employed.

Resistance (third load circuit) R21is connected between the first end of common mode choke coil L3and the signal input terminal of drive circuit6. Resistance (third load circuit) R22is connected between the first end of common mode choke coil L4and the signal input terminal of drive circuit7.

In a high frequency range, the input capacitance of the drive circuit lowers the input impedance of the drive circuit. In drive device104, when the induced electromotive force occurs in parasitic inductance LP1, the surge current flows into drive circuit6via input impedance Z1of drive circuit6so that drive circuit6may malfunction or break. When the induced electromotive force occurs in parasitic inductance LP2, the surge current flows into drive circuit7via input impedance Z2of drive circuit7so that drive circuit7may malfunction or break.

It is assumed that resistances R21and R22have the resistance values of R21and R22, respectively, and capacitors C3and C9have the capacitance values of C3and C9, respectively. In drive device104, the resistance values and the capacitance values are set to satisfy relationships of ((1/ω×C3))<<R21) and ((1/ω×C9))<<R22)).

The above structure can prevent the surge current from flowing to the input terminals of drive circuits6and7, and can prevent the malfunction and destruction of drive circuits6and7.

Other structures and operations are the same as those of the drive device according to the third embodiment, and therefore description thereof is not repeated.

Similarly to the drive device according to the third embodiment of the invention, therefore, the drive device according to the fourth embodiment of the invention drives the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit based on the common drive control signal, and can reduce the influence of the induced electromotive force caused by the switching operation of the semiconductor elements.

Further another embodiment of the invention will now be described with reference to the drawings. The corresponding portions bear the same reference numbers, and description thereof is not repeated.

Fifth Embodiment

This embodiment relates to a drive device that differs from the drive device according to the fourth embodiment in that the delay times of the respective drive control signals are equal to each other.

FIG. 6is a circuit diagram illustrating a structure of an AC power supply circuit205according to a fifth embodiment of the invention.

Referring toFIG. 6, a drive device105according to the fifth embodiment of the invention differs from the drive device according to the fourth embodiment of the invention in that a resistance (fourth load circuit) R23is additionally employed.

Resistance (fourth load circuit) R23is connected between node N1and the signal input terminal of drive circuit5.

Resistances R21-R23have substantially the same impedances. Owing to this structure, the times of delay of drive control signals DRV caused between the output of bypass circuit9and the respective signal input terminals of drive circuits5-7are equal to each other, and switch elements11-13can perform the switching operation according to the same timing based on drive control signal DRV.

Other structures and operations are the same as those of the drive device according to the fourth embodiment, and therefore description thereof is not repeated.

Similarly to the drive device according to the fourth embodiment of the invention, therefore, the drive device according to the fifth embodiment of the invention drives the plurality of semiconductor elements having the respective reference potential electrodes coupled via the main electrode unit based on the common drive control signal, and can reduce the influence of the induced electromotive force caused by the switching operation of the semiconductor elements.