Smart Gate Driver Coupler TLP5214 Application Note Advanced ver.-

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1 < 貴社内限定でご活用下さい > Smart Gate Driver Coupler TLP5214 Application Note Advanced ver.- Rev /12/23

2 Contents Setting and adjustment method of blanking time P3 Reference waveforms (changing C BLANK ) 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, R g and Q g P9 Prevent false 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 R B ) P12 LED signal reshape P16 RESET function P17 Other notes P18 2

3 Controller DRIVER Setting and adjustment method of blanking time When the TLP5214 LED is turned on, the output voltage (V out ) increases. Then the IGBT is turned on. At this time, in order to monitor the collector-emitter voltage (V CE ), the external blanking capacitor (C BLANK ) is charged by a charging current (I CHG ), flowing from the terminal, causing the terminal voltage to rise. function should be disabled until V CE becomes lower than V th(igbt). This time is called blanking time (t BLANK ). This can be adjusted using C BLANK inserted between the and VE terminals. If the terminal voltage exceeds the threshold voltage, 6.5V (typ.), TLP5214 starts soft turn-off of the IGBT. The t BLANK needs to be (1) longer than the time t th that V CE reaches V th(igbt), and (2) shorter than the IGBT short-circuit time t sc. *V th(igbt) :P.6 IF I F TLP5214 UVL O Blanking time is adjusted by C BLANK. Vcc2 Vout 1μF 1μF I CHG R P V GE V CE V th(igbt) t th IC LED Signal V EE C BLANK V 6.5 V Rf SHIELD V CLAMP V CLAMP 1μF R pull R G V GE V CE N voltage Monitor IGBT V voltage (contain Di, R) E V F +(R I CHG ) +V CE(sat) V E 0.1μF V LED t BLANK The invalid time of over current protection The over current protection function time 3

4 t BLANK (μs) Setting and adjustment method of blanking time t BLANK can be calculated by C BLANK, V and I CHG. t BLANK = C BLANK V / I CHG Where, V is 6.5 V (typ.) and I CHG is 240 μa (typ.). IF Example) When the C BLANK is 100 pf, tblank is calculated as V CE IC t BLANK = 10-7 F x 6.5 V / (2.4 x 10-4 ) A = 2.7 μs The relationship between C BLANK and t BLANK is shown in the graph below. V 6.5 V terminal voltage Small C BLANK Large t BLANK - C BLANK C BLANK (pf) Small t BLANK Over current protection invalid term Over current Protection term Large Over current protection invalid period is adjusted by C BLANK. 4

5 Reference waveforms (Changing C BLANK ) and V out terminal waveforms when the TLP5214 LED is turned on are shown below. TLP5214 C BLANK = 100 pf TLP5214 C BLANK = 200 pf Ta=25 I F =10mA,V CC2 =30V Rg=10Ω,Cg=25nF Ta=25 I F =10mA,V CC2 =30V Rg=10Ω,Cg=25nF t BLANK 1μs t BLANK 1μs It is confirmed that t BLANK is changed by C BLANK. Reference (ACPL-332J) t1 (Delay time) Ta=25 I F =10mA,V CC2 =30V Rg=10Ω,Cg=25nF 1μs Left figure is terminal voltage waveform of ACPL-332J. ACPL-332J has a delay time (t 1 ). 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. *Measured waveform contains stray capacitance of PCB and probe capacitance. 5

6 Confirmation of the switching time To check if the switching time of IGBT turn-on is below t BLANK. Condition: t plh of TLP t ON * of IGBT = Switching time < t BLANK *where, t th is similar to t ON. t plh : 150 ns (max) from TLP5214 datasheet. t ON : estimates from Q g of IGBT, I O of TLP5214 (formula; t ON = Q g /I O ) Example) When IGBT (GT30J341) switches at V GE = 15 V and I O = 1.5 A, Q g is Switching time < t BLANK 130 nc using the IGBT s V CE, V GE -Q g characteristics. The t ON is estimated as below; t ON =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** It is recommended to use a large C BLANK that satisfies the relationship between t BLANK and t sc, which is explained on page 3. GT30J341 (**t BLANK :P.3) 15V I F V O I O V CE V th(igbt) TLP5214: t plh IC IGBT: t ON If t BLANK is shorter than switching time of IGBT, TLP5214 malfunction may occur. V 6.5V terminal voltage V E t BLANK 6

7 IGBT over current sensing voltage setting TLP5214 s V is 6.5V (typ.). However, if the threshold voltage of IGBT short (V th(igbt) ) needs to be lower, there are two ways to accomplish this requirement: (1) using the V F of external multiple diodes, or (2) using Zener diodes. 1.New V th(igbt) = V - (n x V F + R x I CHG ) n: number of diodes 2.New V th(igbt) = V - (V F + V z + R x I CHG ) V z : Zener voltage Example) If diodes are used (V F = 0.4 V@240 μa) and R is 100 Ω, the new V th(igbt) is changed per below; New V th(igbt) = 6.5 (3 x 0.4 V Ω x 240 μa) 5.3 V Vcc2 TLP5214 IF example V O V 100Ω 1 2 P V O V EE C BLANK R G V CE IC V CLAMP V E During normal operation, a forward current flows at the diode to monitor the RV PullDow CE of IGBT. n 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. Using the Zener diode, you can tune V th(igbt) with a high accuracy. N V th(igbt) New V th(igbt) V 6.5 V terminal voltage V F n Voltage of pin changes due to V F of diode and Vz of Zener diode. V F n 7

8 t PLH /t PHL (ns) t PLH /t PHL (ns) Relationship among propagation delay time, gate capacitance and gate resistance I F = 10 ma (P.G.) (f =10 khz, duty = 50 %, t r = t f < 5 ns) t plh /t phl - C g V EE = 0 V R g = 10 Ω V EE = 0 V C g = 25 nf t plh /t phl - R g t plh t plh t phl 50 t phl Cg (nf) Rg (Ω) 8

9 t (10%) (μs) t (10%) (μs) Relationship among soft-turn off time, Rg and Qg The TLP5214 soft turn-off time(t (10%) ) depends on the gate resistance (Rg), the gate capacitance(c g ) and the output supply voltage (V CC2 ). Soft turn-off time t (10%) C g Vcc2=15V Vcc2=30V V EE = 0 V R g =10 Ω 6 4 t (10%) R g Vcc2=15V Vcc2=30V V EE = 0 V C g = 25 nf Cg (nf) Rg (Ω) 9

10 TLP5214 Prevent false operation due to negative voltage spikes during IGBT switching One of the reason for false triggering is caused by a forward current flow which is generated by forward biasing at the built-in diode. This occurs by pulling the 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 V E. The Zener diode (V Z = 7 to 8 V) prevents any high transient voltage which can affect the pin while the Schottky diode prevents the forward biasing of the built-in diode. 1uF C BLANK *A negative power supply is used 1uF R D P 1uF R B 10Ω R G 25nF N 10

11 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 V EE, and a 10 Ω resistor is connected across the photocoupler V out 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 V CLAMP is not used (e.g. using a negative voltage source), this pin should be connected to the VEE pin. Below transistors and diodes are recommended as the buffer transistors and diode respectively. 1uF C BLANK TTC3710B Transistors example R D P P/N Max. rating NPN PNP V CEO (V) I C (A) P C (W) Package 1uF TTC3710B TTA1452B TO-220SIS 1uF R B 10Ω R G Diodes example 25nF P/N Max. rating Characteristics (Max.) V RRM (V) I F(AV) (A) V FM FM (A) Package TTA1452B N CRF CRF S-FLAT TM CMF M-FLAT TM 11

12 TLP5214 Blanking time adjustment by an external blanking circuit (using R B ) The method shown below uses one external resistor (R B ), connected between the photocoupler output and the pin. This circuit creates an additional blanking capacitor current (I B ) from the TLP5214 output through the R B for charging the blanking capacitor (C BLANK ). By controlling the charging current of C BLANK using the R B, the blanking time (t BLANK ) can be adjusted with high flexibility. (Note: If no SBD is connected across the V E and the pins, the function may be falsely triggered.) >>Calculation V I =V OUT -V E =R B x i(t) +1/C BLANK (I CHG +i(t)dt)) i(t) = (V I /R B + I CHG ) exp(-t/(c BLANK x R B )) - I CHG 1uF I CHG C BLANK R D P V (t) = V I R B x i(t) = V I - (V I + R B x I CHG )exp (-t/(c BLANK x R B )) +R B x I CHG t BLANK = - C BLANK x R B x log( 1- V /(V I +R B x I CHG ) ) 1uF I B 1uF R B 10Ω 25nF N Example) C BLANK =300pF R B =30kΩ V OUT =17V V EE =10 V [V =6.5V, I CHG =0.25mA referred from the datasheet] t = - 300x10-12 x 30x10 3 x log(1-6.5/(17+30x10 3 x250x10-6 ) = x 10-9 x log (1-6.5/(17+7.5)) = -9 x10-6 x log (0.7346) = x10-6 t BLANK : 2.8 μs 12

13 Blanking time adjustment by an external blanking circuit (using R B ) Below is an example of the measured waveform using this method. (Condition: C BLANK = 100 pf, R B = 30 kω, V CC2 = 17 V, V EE = 10 V) R B : none (open) 3.1us I F V OUT FAULT In case no R B is used, t BLANK is measured as 3.1 μs. When R B is used, it becomes 1.2 μs due to the addition of I B through the resistor. This allows using a large C BLANK with short t BLANK which satisfies the t sc of IGBT. Test circuit (adding R B to the t measurement circuit) C BLANK = 100 pf I F SCOPE R B =30kΩ V OUT 17V 1.2us FAULT 10V R B = 30 kω 13

14 t BLANK (μs) Blanking time adjustment by an external blanking circuit (using R B ) These waveforms show t BLANK dependence on C BLANK. (Condition: R B = 30 kω, C BLANK = 50 to 1000 pf, V CC2 = 17 V, V EE = 10 V) C BLANK = 100 pf C BLANK = 330 pf C BLANK = 680 pf I F I F I F V OUT V OUT V OUT FAULT FAULT FAULT C BLANK = 50 to 1000 pf 10 8 実測値 Measured Calculated 計算値 SCOPE R B = 30 kω 6 17V 10V C BLANK (pf) 14

15 t BLANK (μs) Blanking time adjustment by an external blanking circuit (using R B ) These waveforms show t BLANK dependence on R B. R B = 1 kω R B = 30 kω I F I F V OUT V OUT FAULT FAULT C BLANK = 330 pf 10 8 Measured Calculated 実測値 計算値 SCOPE R B = 330 to 30 kω V 10V R B (Ω) 15

16 Controller DRIVER LED signal reshape 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. TLP5214 LED signal 74VHCV244FT I F LED current limiter SHIELD Rf 0.1μF To reshape the input signal, using a buffer with hysteresis is recommended. Buffer IC example P/N Function V CC(opr) I OH /I OL t pd Package 74VHCV244FT Octal Schmitt Bus Buffer 1.8 to 5.5 V 16 ma 3.9 ns (typ.) TSSOP20B 16

17 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 OFF ON, 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 IF When the pin voltage reaches to 6.5 V, V o changes to low (soft-shutdown) 端子電圧が and the 規定値を超え FAULT output Vochanges が保護動作に入る from high FAULT to low. 信号 H L V O 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. terminal voltage FAULT terminal output t BLANK 6.5V FAULT mode is unlocked when the LED OFF ON t (FAULT) Timing chart of TLP5214 (FAULT condition) 17

18 Controller DRIVER Other notes 1A ceramic by-pass capacitor (1 μf) should be connected between V CC2 V EE and V E V CC2 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 V CC1 - V s. 3 The V LED pin should not be connected to others pins. 4 If the active Miller clamping function do not be used, V CLAMP pin should be shorted to the V EE pin. TLP5214 V cc2 1 1 UVLO 1μF 1μF Vout R SHIELD V CLAMP V EE 4 V CLAMP 1μF 1 R pull R G P R f 0.1μF 2 V E V LED 3 N 18

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21 Revision history Revision Revision date Page Nature of revision Rev /12/23-1 st edition 21