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					Power Electronics
                Supplement:
        Practical Application Issues
     of Power Semiconductor Devices
                    and
      Gate Triggering Control Circuit
          for Thyristor Rectifiers
Power Electronics   Outline
                    Practical application issues of power semiconductor
                      devices
                      Gate drive circuit
                      (Section 1.6 in the Chinese textbook)
                      Protection of power semiconductor devices
                      (Section 1.7 in the Chinese textbook)
                      Series and parallel connections of power
                      semiconductor devices
                      (Section 1.8 in the Chinese textbook)

                    Gate triggering control circuit for thyristor rectifiers
                      (Section 2.9 in the Chinese textbook)

                                                                               2
Power Electronics   1.6 Gate drive circuit
                    Basic function of gate drive circuit:
                      is to generate gate signals to turn-on or turn-off power
                      semiconductor device according to the commanding
                      signals from the control circuit.

                    Other functions of gate drive circuit:
                      Reduce switching time (including turn-on time and turn-
                      off time)
                      Reduce switching loss (including turn-on loss and turn-
                      off loss) and improve efficiency
                      Improve protection and safety of the converter

                    Gate drive circuits provided by power semiconductor
                    manufacturers and Integrated gate drive chips are
                    more and more widely used.
                                                                                 3
Power Electronics   Electrical isolation in the gate drive circuit
                     Gate drive circuit usually
                     provides the electrical                  ID      IC
                     isolation between control                                       E
                     circuit and power stage.                           R1
                                                              R
                                                       U in
                     Two ways to provide                               Photo
                                                                                  U out
                                                                     transistor
                     electrical isolation                     LED


                     – Optical
                         • Optocoupler, fiber optics
                         • Transformer                 Schematic of an optocoupler
                     – Magnetic



                                                                                          4
Power Electronics   Thyristor gate current pulse requirments
                     Shape of gate current
                     pulse waveform:
                      – Enhanced leading part
                     Magnitude requirement
                     (for the enhanced leading
                                                          IM
                     part and the other part)
                                                                    I
                     Width requirement (for the                                            t
                     enhanced leading part and    t1 t2        t3                     t4

                     the whole pulse)
                                                           Ideal gate current pulse
                     Power of the triggering
                                                           waveform for thyristors
                     signal must be within the
                     SOA of the gate I-V
                     characteristics
                                                                                           5
Power Electronics   Typical thyristor gate triggering circuit

                                         +E1          +E2         VD2   R4
                                                            TM




                                                VD1




                                                                  VD3
                                         R1
                                                    R3

                        Input from                           R2
                                               V1
                       control circuit
                                                            V2




                                                                             6
                    Typical gate signal and gate drive circuit
Power Electronics   for GTO



                    uG
                                                     C2 VD3             R1

                     O                t




                                                            VD2
                                                                   R2
                                                                                            GTO
                                                     VD1
                     iG                                                           V1         L
                                                     N2     C1    C 3 V2
                     O                    50kHz                                             R3
                                      t         N1
                                           50V                               V3
                                                     N3           C4                   R4
                                                           VD4




                                                                                                  7
                    A typical gate drive circuit for IGBT based on
Power Electronics   an integrated driver chip


                                                     4 VCC                                 4.7kΩ
                                         Detection                                                   Fast recovery diode
                    14                    circuit    1 Sensing                                            trr≤ 0.2µs
                                                                                       8
                                                                                               1
                                     Timer and
                                    reset circuit
                                                                      +5V                                  30V
                                                                                14             5
                             Interface                                                                     3.1Ω
                              circuit                5 uo                                      4
                                                                                     M57962L                +15V
                                                                      ui        13
                                          Turn-off         Error            1                      100µF
                                           circuit
                                                     8
                                                         indicating                                100µF
                    13                                                                         6
                                                     6 VEE                                                  -10V



                     M57962L integrated driver chip



                                                                                                                     8
                    1.7 Protection of power semiconductor
Power Electronics   devices
                    Protection circuits
                      Overvoltage protection
                      Overcurrent protection

                    Snubber circuits—specific protection circuits that
                      can limit du/dt or di/dt
                      Turn-on snubber
                      Turn-off snubber




                                                                         9
                    Causes of overvoltage on power
Power Electronics   semiconductor devices

                    External reasons
                      Overvoltage caused by operation of mechanic
                      swithes
                      Overvoltage caused by thunder lightening

                    Internal reasons
                       Overvoltage caused by the reverse recovery of
                       diode or thyristor
                       Overvoltage caused by the turning-off of fully-
                       controlled devices


                                                                         10
                    Measures to protect power semiconductor
Power Electronics   devices from overvoltage

                                                                       SDC
                                  T                                          LB
                                                                                  M
                       S
                                                          U
                                          C
                           F
                                                          RV   RC3            RCD
                                                                     RC4
                                                    RC2
                                      D       RC1



                      Lightening arrestor
                      RC or RCD snubbers (will be discussed later)
                      Zener diode, Metal Oxide Varistor (MOV), Break Over
                      Diode (BOD)
                                                                                      11
                    Measures to protect power semiconductor
Power Electronics   devices from overcurrent
                     Fuse
                     Circuit breaker
                     Protection with current feedback control in the control
                     circuit
                     Protection with overcurrent detection in the gate drive
                     circuit—the fastest measure




                                                                               12
Power Electronics   Functions and classifications of snubbers
                    Functions
                      Limiting voltages applied to devices during turn-off transients
                      Limiting device currents during turn-on transients
                      Limiting device current rising rate (di/dt) at device turn-on
                      Limiting the rate of rise (du/dt) of voltages across devices
                      during device turn-off
                      Shaping the switching trajectory of the device

                    Classifications
                      According to different switching transients
                       – Turn-off snubber (sometimes just called snubber)
                       – Turn-on snubber
                      According to the treatment of energy
                       – Power dissipating snubber
                       – Lossless snubber

                                                                                        13
Power Electronics   Operation principle of typical snubbers
                    Circuit configuration                 uCE                         without turn-off snubber
                                                          iC
                                                                    without turn-on snubber              uCE
                                                                                      iC
                                       Turn-on                                                       with turn-off
                            Ri         snubber                                                         snubber
                                 Li                        O
                           VDi                                                                                 t
                                                                    with turn-on snubber
                                               Turn-off
                                               snubber
                                                          iC
                                               VDs


                            V         Rs                        A                                   B
                                                                         without turn-off snubber
                                               Cs


                                                                         with turn-off snubber
                                           L                         D
                                                                                                        C
                           VD
                                                           O                                             uCE
                                                                    Switching trajectory                             14
Power Electronics   Other turn-off snubbers



                          L   Rs                    L
                                    Turn-off            Cs         Turn-off
                                    snubber
                                                                   snubber




                                                        VDs
                     Ed        Cs              Ed
                                                              Rs
                                   Load                       Load




                                                                          15
                    1.8 Series and parallel connections of
Power Electronics       power semiconductor devices
                    Object
                      To increase the capability to deal with voltage or current

                    Issues and solutions
                       Series connection
                        – Issue: even voltage sharing
                        – Solutions:
                            • Selection of devices that are closer to each other in the characteristics
                            • Voltage sharing circuit
                       Parallel connection
                        – Issue: even current sharing
                        – Solutions:
                            • Selection of devices that are closer to each other in the characteristics
                            • Current sharing circuit and symmetrical circuit layout


                                                                                                          16
Power Electronics   Series Connection of thyristors

                             I    VT1
                                    VT2                                        R
                                                               VT1        RP
                                                                               C
                             IR
                                                                               R
                             O            UT1        UT2   U   VT2        RP
                                                                               C



                                                a)                   b)

                     Voltage sharing circuit
                      – Steady-state voltage sharing circuit
                      – Dynamic voltage sharing circuit
                                                                                   17
Power Electronics   Parallel Connection of Power MOSFETs




                     Easy to realize because of the positive temperature coefficient of
                     their on-state resistance
                     Need a small damping resistor in series with the individual gate
                     connections
                     Still need to select devices that are closer to each other in the
                     characteristics
                     Circuit layout should be symmetrical                                 18
                    2.9 Gate triggering control circuit for
Power Electronics   thyristor rectifiers
                    Object
                      How to timely generate triggering pulses with
                      adjustable phase delay angle

                    Constitution
                      Synchronous circuit
                      Saw-tooth ramp generating and phase shifting
                      Pulse generating

                    Integrated gate triggering control circuits are very
                       widely used in practice.

                                                                           19
Power Electronics   A typical gate triggering control circuit
                                                                                                                R15
                                                                                    VD11~VD14
                                                                                                         C7 + C 6
                                                                                                                           VD15
                                                                                   220V         36V                   B               +15V
                                                                                                              VD7         TP    VD8
                     +15V
                                                                                                                                     R18
                                                      RP2                                R11      R12           R14
                                                                             R9
                                           VS        R3                             C3                    R13                  VD9
                                                                              A
                                                                                                 V5                       R16
                                                     V1                 VD4                                      C5
                                   R1                                                     R10           VD6
                                                      I1c
                                                                 V3     R6                                      V7
                                                                                  V4
                                                                  R7
                                                R4
                        TS       VD1 VD2                    C2                    R17
                                                                                                  V6                      V8
                             R                       V 2 R5             R8                C3
                                       Q
                                                                                         VD10           VD5
                                 uts       C1   R2
                                                                       up
                                                                        RP1
                                                                                                         Disable
                                                                 uco -15V           XY         -15V                                          20
                    Waveforms of the typical
Power Electronics   gate triggering control circuit




                                                      21
                    How to get synchronous voltage for the gate
Power Electronics   triggering control circuit of each thyristor
                             uA   uB   uC

                                                                             UAB
                                                                                   Ua
                                                                                        Usa
                                                                                              -Usc

                       TR                                    TS             -Usb                     Usb
                                                                                                           Ub
                                                                 D,y 5-11
                    D,y 11                                                              Usc -U
                                                                                               sa
                             ua   ub   uc - usa - usc - usb                        Uc
                                             - usb - usa - usc

                     For the typical circuit on page 20, the synchronous voltage of the
                     gate triggering control circuit for each thyristor should be lagging
                     180º to the corresponding phase voltage of that thyristor.           22

				
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posted:8/19/2011
language:English
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