Smart Gate Driver Coupler TLP5214 Application Note ... · Smart Gate Driver Coupler TLP5214 Application Note ... pLH of TLP5214 + t ON * of IGBT = Switching time < t BLANK *where,

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© 2015, Toshiba Corporation. Rev.1.0 2015/12/23

Smart Gate Driver Coupler TLP5214 Application Note –Advanced ver.-

2 © 2015, Toshiba Corporation.

・ Setting and adjustment method of blanking time P3

・ Reference waveforms (changing CBLANK) P5

・ Confirmation of the switching time P6

・ IGBT over current sensing voltage setting P7

・ Relationship among propagation delay time, gate capacitance and P8

gate resistance

・ Relationship among soft-turn off time, Rg and Qg P9

・ Prevent false DESAT operation due to negative voltage spikes during IGBT

switching P10

・ External current booster (transistor buffer) P11

・ Blanking time adjustment by an external blanking circuit (using RB) P12

・ LED signal reshape P16

・ RESET function P17

・ Other notes P18

Contents


When the TLP5214 LED is turned on, the output voltage (Vout) increases. Then the IGBT is turned on. At this

time , in order to monitor the collector-emitter voltage (VCE), the external blanking capacitor (CBLANK) is charged

by a charging current (ICHG), flowing from the DESAT terminal, causing the DESAT terminal voltage to rise.

DESAT function should be disabled until VCE becomes lower than Vth(IGBT). This time is called blanking time

(tBLANK). This can be adjusted using CBLANK inserted between the DESAT and VE terminals. If the DESAT terminal

voltage exceeds the DESAT threshold voltage, 6.5V (typ.), TLP5214 starts soft turn-off of the IGBT.

The tBLANK needs to be (1) longer than the time tth that VCE reaches

Vth(IGBT), and (2) shorter than the IGBT short-circuit time tsc.

*Vth(IGBT)：P.6

Setting and adjustment method of blanking time

VCE

VGE

IF

Vth(IGBT)

DESAT voltage

Blanking time is adjusted by CBLANK.

tBLANK The invalid time of over current protection

The over current protection function time

Monitor IGBT voltage (contain Di, R)

CBLANK

VGE

VCE

ICHG

VLED

VCLAMP

VEE

DESAT

Vcc2

Rf

0.1μF

P

N

VCLAMP

DR

IVER

UVLO

SHIELD

DESAT

TLP5214

LED Signal

Contr

oller

IF

VE

Vout

RDESAT

1μF

1μF

RG

Rpull

1μF

VDESAT≃ 6.5 V

IC

VE

tｔｈ

VF +(RDESAT×ICHG) +VCE(sat）


0

2

4

6

8

10

0 100 200 300

tBLANK － CBLANK

CBLANK (pF)

t BLA

NK (μ

s)

Setting and adjustment method of blanking time

tBLANK can be calculated by CBLANK , VDESAT and ICHG.

tBLANK = CBLANK × VDESAT / ICHG

Where, VDESAT is 6.5 V (typ.) and ICHG is 240 μA (typ.).

Example)

When the CBLANK is 100 pF, tBLANK is calculated as

tBLANK = 10-7 F x 6.5 V / (2.4 x 10-4) A

= 2.7 μs

The relationship between CBLANK and tBLANK is

shown in the graph below.

VCE IC

DESAT terminal

voltage

IF

Over current

Protection term

CBLANK Small Large

tBLANK

Over current

protection invalid

term

Over current protection invalid

period is adjusted by CBLANK.

VDESAT ≃ 6.5 V

Small

Large


Reference waveforms (Changing CBLANK)

TLP5214 CBLANK = 100 pF TLP5214 CBLANK = 200 pF

DESAT and Vout terminal waveforms when the TLP5214 LED is turned on are shown below.

*Measured waveform contains stray capacitance of PCB and probe

capacitance.

t1 （Delay time）

It is confirmed that tBLANK is changed by CBLANK.

Left figure is DESAT terminal voltage waveform of ACPL-332J. ACPL-332J has a delay time (t1). The behavior at the LED turning on period of ACPL-332J is different from TLP5214. If you replace the ACPL-332J with the TLP5214, you need to check the circuit operation.

※Reference （ACPL-332J）

tBLANK

Ta=25℃ IF=１0mA,VCC2=30V Rg=10Ω,Cg=25nF

1μs 1μs

1μs

tBLANK




GT30J341

Confirmation of the switching time

15V

To check if the switching time of IGBT turn-on is below tBLANK.

Condition: tpLH of TLP5214 + tON* of IGBT = Switching time < tBLANK *where, tth is similar to tON.

tpLH: 150 ns (max) from TLP5214 datasheet.

tON: estimates from Qg of IGBT, IO of TLP5214 (formula; tON = Qg/IO)

Example)

When IGBT (GT30J341) switches at VGE = 15 V and IO = 1.5 A, Qg is

130 nC using the IGBT’s VCE, VGE-Qg characteristics.

The tON is estimated as below;

tON=130 nC / 1.5 A ≃ 87 ns

Therefore, the switching time criteria is satisfied.

switching time = 150 ns + 87 ns = 237 ns < 2.7 μs** (**tBLANK:P.3)

It is recommended to use

a large CBLANK that satisfies

the relationship between

tBLANK and tsc, which is

explained on page 3.

VCE IC

DESAT terminal voltage

IF

VO

IO

TLP5214: tpLH IGBT: tON

tBLANK

Switching time < tBLANK

Vth(IGBT)

VE

VDESAT ≃ 6.5V

If tBLANK is shorter than switching time of IGBT, TLP5214 malfunction may occur.


VCE


IF

VO

VF × n

Vcc2

P

N

TLP5214

VCLAMP

VEE

VO

VDESAT

CBLANK

RG

RPullDow

n

VE During normal operation, a forward current flows at the DESAT diode to monitor the VCE of IGBT. In case of a high wattage application, the over current protection function may malfunction due to reverse recovery spikes at the freewheel diode in the IGBT. In order to minimize the reverse recovery current, a FRD with smaller capacitance is recommended.

IGBT over current sensing voltage setting

Vth(IGBT)

New Vth(IGBT)

100Ω ①

②

example

Using the Zener diode, you can tune Vth(IGBT) with a high accuracy.

VDESAT ≃ 6.5 V

IC

VF × n

Voltage of DESAT pin changes due to VF of diode and Vz of Zener diode.

TLP5214’s VDESAT is 6.5V (typ.). However, if the threshold voltage of IGBT short (Vth(IGBT)) needs to be lower,

there are two ways to accomplish this requirement: (1) using the VF of external multiple DESAT diodes, or

(2) using Zener diodes.

1.New Vth(IGBT) = VDESAT - (n x VF + RDESAT x ICHG) n: number of diodes

2.New Vth(IGBT) = VDESAT - (VF + Vz + RDESAT x ICHG) Vz: Zener voltage

Example) If diodes are used (VF = 0.4 V@240 μA) and RDESAT is 100 Ω, the new Vth(IGBT) is changed per below;

New Vth(IGBT) = 6.5 – (3 x 0.4 V + 100 Ω x 240 μA) ≃ 5.3 V


0

50

100

150

200

10 20 30 40 50

t PLH/t P

HL

(ns)

Cg (nF)

tpLH/tpHL - Cg

0

50

100

150

200

0 10 20 30 40 50

t PLH/t P

HL

(ns)

Rg (Ω)

tpLH/tpHL - Rg

VEE = 0 V Rｇ＝ 10 Ω

VEE = 0 V Cｇ＝ 25 nF

Relationship among propagation delay time, gate capacitance and gate resistance

IF = 10 mA (P.G.) (f =10 kHz, duty = 50 %, tr = tf < 5 ns)

tpLH

tpHL

tpLH

tpHL


The TLP5214 soft turn-off time(tDESAT(10%))

depends on the gate resistance (Rg), the gate

capacitance(Cg) and the output supply voltage (VCC2).

Soft turn-off time

0

2

4

6

8

10

0 10 20 30 40 50

t DES

AT(1

0%

) (μ

s)

Cg (nF)

tDESAT(10%) – Cg

Vcc2=15V

Vcc2=30V

0

2

4

6

10 20 30 40 50

t DES

AT(1

0%

) (μ

s)

Rｇ (Ω)

tDESAT(10%) – Rg

Vcc2=15V

Vcc2=30V

VEE = 0 V Rg＝10 Ω

VEE = 0 V Cg = 25 nF

Relationship among soft-turn off time, Rg and Qg


Prevent false DESAT operation due to negative voltage spikes during IGBT switching

One of the reason for DESAT false triggering is caused by a forward current flow which is generated by forward biasing at the DESAT built-in diode. This occurs by pulling the DESAT pin voltage below GND level due to reverse recovery spikes of the freewheeling diode (the negative spike are generated by inductive loads or reverse recovery spikes of IGBT/MOSFETs freewheeling diodes). To minimize this malfunction, it is recommended to connect properly rated Zener and Schottky diodes between DESAT – VE. The Zener diode (VZ = 7 to 8 V) prevents any high transient voltage which can affect the DESAT pin while the Schottky diode prevents the forward biasing of the built-in diode.

*A negative power supply

is used

RG

1uF

1uF

1uF

10Ω

25nF

RB

RDESAT DDESAT

CBLANK

P

N

TLP5214


External current booster (transistor buffer)

The TLP5214 can output 4A (max). If the current is not enough to drive the IGBT, a buffer

(a pair of NPN and PNP transistors) can be used as a current booster.

A 25 nF capacitor is connected across buffer input and VEE, and a 10 Ω resistor is connected

across the photocoupler Vout pin and the buffer input, as shown below. These passive devices

are necessary for soft turn-off of the IGBT in the event that desaturation does occur.

If VCLAMP is not used (e.g. using a negative voltage source), this pin should be connected to

the VEE pin.

P/N Max. rating

Package

NPN PNP VCEO (V) IC (A) PC (W)

TTC3710B TTA1452B 80 12 30 TO-220SIS

TTA1452B

TTC3710B

Below transistors and diodes are recommended as the

buffer transistors and DESAT diode respectively.

P/N Max. rating Characteristics (Max.)

Package VRRM (V) IF(AV) (A) VFM (V) @IFM (A)

CRF02 800 0.5 3.0 0.5 S-FLATTM

CRF03 600 0.7 2.0 0.7

CMF05 1000 0.5 2.7 0.5 M-FLATTM

Transistors example

Diodes example RG

1uF

1uF

1uF

10Ω

25nF

RB

RDESAT

DDESAT

CBLANK

P

N

TLP5214


Blanking time adjustment by an external blanking circuit (using RB)

The method shown below uses one external resistor (RB), connected between the photocoupler output and the DESAT pin. This circuit creates an additional blanking capacitor current (IB) from the TLP5214 output through the RB for charging the blanking capacitor (CBLANK). By controlling the charging current of CBLANK using the RB, the blanking time (tBLANK) can be adjusted with high flexibility. (Note: If no SBD is connected across the VE and the DESAT pins, the DESAT function may be falsely triggered.)

>>Calculation ＶI＝ＶOUT－ＶE

＝RB x i(ｔ） +1/CBLANK∫(ICHG +i(t)dt)) i(t) = (VI/RB+ ICHG) exp(-t/(CBLANK x RB)) - ICHG

VDESAT (t) = VI – RB x i(t) = VI - (VI + RB x ICHG )exp (-t/(CBLANK x RB)) +RB x ICHG

tBLANK = - CBLANK x RB x log( 1- VDESAT/(VI+RB x ICHG) ) Example) CBLANK=300pF、RB=30kΩ、VOUT=17V、VEE=10 V [VDESAT=6.5V, ICHG＝0.25mA･･･referred from the datasheet] t = - 300x10-12 x 30x103x log(1-6.5/(17+30x103x250x10-6) = - 9000 x 10-9 x log (1-6.5/(17+7.5)) = -9 x10-6 x log (0.7346) = 2.774 x10-6 ｔBLANK : 2.8 μs

ICHG

IB

1uF

1uF

1uF

10Ω

25nF

RB

RDESAT DDESAT

CBLANK

P

N

TLP5214


Below is an example of the measured waveform using this method. (Condition: CBLANK = 100 pF, RB = 30 kΩ, VCC2 = 17 V, VEE = 10 V)

RB=30kΩ

RB: none (open)

1.2us

3.1us

In case no RB is used, tBLANK is measured as 3.1 μs. When RB is used, it becomes 1.2 μs due to the addition of IB through the resistor. This allows using a large CBLANK with short tBLANK which satisfies the tsc of IGBT.

CBLANK ＝ 100 pF

RB ＝ 30 kΩ

IF

VOUT

DESAT

FAULT

IF

VOUT

DESAT

FAULT

Test circuit (adding RB to the tDESAT measurement circuit)

10V

17V

SCOPE



These waveforms show tBLANK dependence on CBLANK. (Condition: RB = 30 kΩ, CBLANK = 50 to 1000 pF, VCC2 = 17 V, VEE = 10 V)

CBLANK = 100 pF

CBLANK ＝ 50 to 1000 pF

RB = 30 kΩ

CBLANK = 330 pF CBLANK = 680 pF

0

2

4

6

8

10

0 200 400 600 800 1000

t BLA

NK(μｓ）

CBLANK(pF)

実測値

計算値

Measured Calculated

IF

VOUT

DESAT

FAULT

IF

VOUT

DESAT

FAULT

IF

VOUT

DESAT

FAULT

10V

17V

SCOPE



10V

17V

SCOPE

These waveforms show tBLANK dependence on RB.

CBLANK = 330 pF

RB = 330 to 30 kΩ

RB = 1 kΩ RB = 30 kΩ

0

2

4

6

8

10

0 10000 20000 30000

t BLA

NK(μｓ）

RB(Ω)

実測値

計算値

IF

VOUT

DESAT

FAULT

IF

VOUT

DESAT

FAULT


Measured Calculated


Rf

0.1μF

DR

IVER

SHIELD

TLP5214

LED signal Contr

oller

IF

If wiring between the control unit and the motor drive unite is long, the input signal shape at the TLP5214 input pins may be distorted due to the wire inductance between the TLP5214 and the CPU.

LED signal reshape

74VHCV244FT

LED current limiter

To reshape the input signal, using a buffer with hysteresis is recommended.

Buffer IC example

P/N Function VCC(opr) |IOH|/IOL tpd Package

74VHCV244FT Octal Schmitt Bus Buffer

1.8 to 5.5 V 16 mA 3.9 ns (typ.) TSSOP20B


RESET function

The TLP5214 operation is resumed from the soft turn-off mode by the LED input signal change. Thus, while the TLP5214 operation goes to the FAULT mode due to the IGBT desaturation, the FAULT output is changed to normal followed by the LED OFFON, and then, the photo-coupler resumes normal operation.

There are several ways of resuming normal operation for smart gate driver couplers, listed below … - LED triggering (e.g. TLP5214) - Auto-reset (FAULT signal is automatically reset after a certain period of time) - Using external reset signal


≃ 6.5V

IF

VO

tBLANK

FAULT terminal output

tDESAT(FAULT)

DESAT端子電圧が規定値を超え、Voが保護動作に入る。FAULT信号 H→L

Timing chart of TLP5214 (FAULT condition)

When the DESAT pin voltage reaches to 6.5 V, Vo changes to low (soft-shutdown) and the FAULT output changes from high to low.

FAULT mode is unlocked when the LED OFFON

Since the TLP5214 method for “resumption back to normal operation” is different than (1) auto-reset mode driver couplers, and (2) external reset signal type driver couplers, additional circuitry is required.


①A ceramic by-pass capacitor (1 μF) should be connected between VCC2 – VEE and VE – VCC2 to

stabilize the operation of the internal high gain linear amplifier. Furthermore, in case of use of a

negative power supply, a 1 μF ceramic bypass capacitor is also connected between VE – VEE.

② A ceramic capacitor (0.1 μF) should be connected between VCC1 - Vs.

③ The VLED pin should not be connected to others pins.

④ If the active Miller clamping function do not be used, VCLAMP pin should be shorted to the VEE

pin.

Other notes

VLED

VCLAMP

VEE

DESAT

Vcc2

Rf

0.1μF

P

N

VCLAMP

DR

IVER

UVLO

SHIELD

DESAT

TLP5214

Contr

oller

VE

Vout

RDESAT

1μF

1μF

RG

Rpull

1μF

① ①

② ③

④

①


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Revision history

Revision Revision date Page Nature of revision

Rev.1.0 2015/12/23 - 1st edition

Documents

Smart Gate Driver Coupler TLP5214 Application Note ... · Smart Gate Driver Coupler TLP5214 Application Note ... pLH of TLP5214 + t ON * of IGBT = Switching time < t BLANK *where,