By eectech | 01 June 2018 | 0 Comments
Thyristors, Diodes Main Parameters and Their Meanings (Semiconductors)
There are dozens of parameters used to characterize thyristors and diodes in the IEC standard. However, there are about ten parameters that are frequently used by users. This article gives a brief introduction to the main parameters of thyristors and diodes.
1. Forward average current IF(AV) (rectifier)/on-state average current IT(AV) (thyristor)
Refers to the average value of the maximum sinusoidal half-wave current that is allowed to flow through the device at the specified heatsink temperature THS or case temperature TC. At this point, the junction temperature of the device has reached its maximum allowable temperature Tjm. In the company's product manual, the radiator temperature THS or the shell temperature TC corresponding to the corresponding on-state current is given. The user should select the appropriate type of device according to the actual on-state current and heat dissipation conditions.
2. Positive rms current IF(RMS) (rectifier)/On-state rms current IT(RMS) (Thyristor)
Refers to the maximum effective current that is allowed to flow through the device at the specified heat sink temperature THS or case temperature TC. In use, the user must ensure that under any conditions, the rms current flowing through the device does not exceed the rms current value at the corresponding case temperature.
3. Inrush current IFSM (rectifier), ITSM (thyristor)
Indicates the instantaneous maximum overload current value that the device can withstand under abnormal conditions. With a 10 ms wide sine half-wave peak, the inrush current value given by the company in the product manual is the value under the condition that the device is at the maximum allowable junction temperature and 80% VRRM is applied. The number of times the device can withstand inrush current during its lifetime is limited, and users should try to avoid overload during use.
4. Off-state non-repetitive peak voltage VDSM non-repetitive peak voltage VRSM
Refers to the maximum turning voltage that a thyristor or rectifier diode can withstand when in a blocking state. It is generally used to prevent damage to the device with a single pulse test. The user shall prohibit the application of this voltage to the device during testing or use so as not to damage the device.
5. Off-state repeated peak voltage VDRM/inverse repeated peak voltage VRRM
Refers to the maximum repetitive peak voltage that the off-state and can withstand when the device is in a blocking state. Generally take 90% of the device's non-repeating voltage (high voltage device does not repeat the voltage minus 100V marked). The user must ensure in use that the actual voltage to which the device is exposed should not exceed its off-state and inverted-repeated peak voltage under any circumstances.
6. Off-State Repeat Peak (Leakage) Current IDRM/ Inverted Repeat Peak (Leakage) Current IRRM
In the blocking state of the thyristor, the peak-to-peak peak-to-peak leakage current that flows through the device when subjected to the off-state repeated peak voltage VDRM and the inverted repeated peak voltage VRRM. This parameter is measured at the maximum junction temperature Tjm at which the device is allowed to operate.
7. On-state peak voltage VTM (thyristor) / positive peak voltage VFM (rectifier)
It refers to the peak voltage when the device passes the specified forward peak current IFM (rectifier) or the on-state peak current ITM (thyristor), also called the peak voltage drop. This parameter directly reflects the on-state loss characteristics of the device and affects the on-state current rating of the device.
The on-state (forward) peak voltage of the device at different current values can be approximated by the threshold voltage and slope resistance:
VTM=VTO+rT*ITM VFM=VFO+rF*IFM
In the product manual, the company provides the maximum on-state (forward) peak voltage, threshold voltage, and slope resistance of each device. When required, the device can provide the measured threshold voltage and slope resistance of the device.
8. Circuit commutation turn-off time tq (thyristor)
Under specified conditions, after the thyristor positive main current drops through zero, from the zero-crossing point to the minimum time interval during which the component can withstand the specified reapplied voltage rather than conducting. The off-time value of the thyristor is determined by the test conditions. The company provides the measured off-time values of each device for the manufactured fast and high-frequency thyristors. When not specified, the corresponding test conditions are as follows:
l The on-state peak current ITM is equal to the device ITAV;
l The on-state current drop rate di/dt=-20A/μs;
l increase the voltage increase rate dv/dt = 30A/μs;
l voltage VR=50V;
l Junction temperature Tj=125°C.
If the user needs the off-time test value under a specific application condition, it can ask us.
9. Critical rate of increase in on-state current di/dt (Thyristor)
It refers to the maximum value of the on-state current rise rate that the thyristor can withstand when the thyristor is switched from the blocking state to the conducting state. The critical rate of rise of the on-state currents tolerated by the device, di/dt, is strongly affected by the gate trigger conditions. Therefore, we recommend using a strong trigger mode for the user application. The trigger pulse current amplitude: IG≥10IGT; pulse rise time: tr≤ 1μs.
10. Critical voltage rise rate dv/dt
Under the specified conditions, the maximum forward voltage rise speed allowed by the thyristor to switch from the off state to the on state will not be caused. The minimum dv/dt value of all types of thyristors is given in the company's product manual. When the user has special requirements for dv/dt, it can be made at the time of ordering.
11. Gate trigger voltage VGT
Gate trigger current IGT
The minimum gate voltage and gate current required to turn the thyristor from on-state to on-state under specified conditions. The on-time, open-loss, and other dynamic properties of the thyristor opening process are greatly affected by the strength of the trigger signal applied to its gate. If the critical IGT is used to trigger the thyristor in the application, the thyristor will not be able to get a good turn-on characteristic, and in some cases it may even cause premature failure or damage of the device. Therefore, we recommend using a strong triggering method in the user application. The trigger pulse current amplitude: IG≥10IGT; pulse rise time: tr≤1μs. In order to ensure reliable operation of the device, the IG must be much larger than the IGT.
12. Thermal resistance Rjc
Refers to the temperature rise of the device from the junction-to-shell flow unit power consumption under the specified conditions. The thermal resistance of the crust reflects the heat dissipation capability of the device. This parameter also directly affects the on-state rating of the device. In the company's product brochures, the steady-state thermal resistance values for double-sided cooling are given for flat-type devices, and the thermal resistance values for single-side thermal dissipation are given for semiconductor power modules. The user must be aware that the thermal resistance of the crust case of the flat panel device is directly affected by the mounting conditions. Only the mounting force recommended in the manual can be used to ensure that the thermal resistance of the device can meet the requirements.
1. Forward average current IF(AV) (rectifier)/on-state average current IT(AV) (thyristor)
Refers to the average value of the maximum sinusoidal half-wave current that is allowed to flow through the device at the specified heatsink temperature THS or case temperature TC. At this point, the junction temperature of the device has reached its maximum allowable temperature Tjm. In the company's product manual, the radiator temperature THS or the shell temperature TC corresponding to the corresponding on-state current is given. The user should select the appropriate type of device according to the actual on-state current and heat dissipation conditions.
2. Positive rms current IF(RMS) (rectifier)/On-state rms current IT(RMS) (Thyristor)
Refers to the maximum effective current that is allowed to flow through the device at the specified heat sink temperature THS or case temperature TC. In use, the user must ensure that under any conditions, the rms current flowing through the device does not exceed the rms current value at the corresponding case temperature.
3. Inrush current IFSM (rectifier), ITSM (thyristor)
Indicates the instantaneous maximum overload current value that the device can withstand under abnormal conditions. With a 10 ms wide sine half-wave peak, the inrush current value given by the company in the product manual is the value under the condition that the device is at the maximum allowable junction temperature and 80% VRRM is applied. The number of times the device can withstand inrush current during its lifetime is limited, and users should try to avoid overload during use.
4. Off-state non-repetitive peak voltage VDSM non-repetitive peak voltage VRSM
Refers to the maximum turning voltage that a thyristor or rectifier diode can withstand when in a blocking state. It is generally used to prevent damage to the device with a single pulse test. The user shall prohibit the application of this voltage to the device during testing or use so as not to damage the device.
5. Off-state repeated peak voltage VDRM/inverse repeated peak voltage VRRM
Refers to the maximum repetitive peak voltage that the off-state and can withstand when the device is in a blocking state. Generally take 90% of the device's non-repeating voltage (high voltage device does not repeat the voltage minus 100V marked). The user must ensure in use that the actual voltage to which the device is exposed should not exceed its off-state and inverted-repeated peak voltage under any circumstances.
6. Off-State Repeat Peak (Leakage) Current IDRM/ Inverted Repeat Peak (Leakage) Current IRRM
In the blocking state of the thyristor, the peak-to-peak peak-to-peak leakage current that flows through the device when subjected to the off-state repeated peak voltage VDRM and the inverted repeated peak voltage VRRM. This parameter is measured at the maximum junction temperature Tjm at which the device is allowed to operate.
7. On-state peak voltage VTM (thyristor) / positive peak voltage VFM (rectifier)
It refers to the peak voltage when the device passes the specified forward peak current IFM (rectifier) or the on-state peak current ITM (thyristor), also called the peak voltage drop. This parameter directly reflects the on-state loss characteristics of the device and affects the on-state current rating of the device.
The on-state (forward) peak voltage of the device at different current values can be approximated by the threshold voltage and slope resistance:
VTM=VTO+rT*ITM VFM=VFO+rF*IFM
In the product manual, the company provides the maximum on-state (forward) peak voltage, threshold voltage, and slope resistance of each device. When required, the device can provide the measured threshold voltage and slope resistance of the device.
8. Circuit commutation turn-off time tq (thyristor)
Under specified conditions, after the thyristor positive main current drops through zero, from the zero-crossing point to the minimum time interval during which the component can withstand the specified reapplied voltage rather than conducting. The off-time value of the thyristor is determined by the test conditions. The company provides the measured off-time values of each device for the manufactured fast and high-frequency thyristors. When not specified, the corresponding test conditions are as follows:
l The on-state peak current ITM is equal to the device ITAV;
l The on-state current drop rate di/dt=-20A/μs;
l increase the voltage increase rate dv/dt = 30A/μs;
l voltage VR=50V;
l Junction temperature Tj=125°C.
If the user needs the off-time test value under a specific application condition, it can ask us.
9. Critical rate of increase in on-state current di/dt (Thyristor)
It refers to the maximum value of the on-state current rise rate that the thyristor can withstand when the thyristor is switched from the blocking state to the conducting state. The critical rate of rise of the on-state currents tolerated by the device, di/dt, is strongly affected by the gate trigger conditions. Therefore, we recommend using a strong trigger mode for the user application. The trigger pulse current amplitude: IG≥10IGT; pulse rise time: tr≤ 1μs.
10. Critical voltage rise rate dv/dt
Under the specified conditions, the maximum forward voltage rise speed allowed by the thyristor to switch from the off state to the on state will not be caused. The minimum dv/dt value of all types of thyristors is given in the company's product manual. When the user has special requirements for dv/dt, it can be made at the time of ordering.
11. Gate trigger voltage VGT
Gate trigger current IGT
The minimum gate voltage and gate current required to turn the thyristor from on-state to on-state under specified conditions. The on-time, open-loss, and other dynamic properties of the thyristor opening process are greatly affected by the strength of the trigger signal applied to its gate. If the critical IGT is used to trigger the thyristor in the application, the thyristor will not be able to get a good turn-on characteristic, and in some cases it may even cause premature failure or damage of the device. Therefore, we recommend using a strong triggering method in the user application. The trigger pulse current amplitude: IG≥10IGT; pulse rise time: tr≤1μs. In order to ensure reliable operation of the device, the IG must be much larger than the IGT.
12. Thermal resistance Rjc
Refers to the temperature rise of the device from the junction-to-shell flow unit power consumption under the specified conditions. The thermal resistance of the crust reflects the heat dissipation capability of the device. This parameter also directly affects the on-state rating of the device. In the company's product brochures, the steady-state thermal resistance values for double-sided cooling are given for flat-type devices, and the thermal resistance values for single-side thermal dissipation are given for semiconductor power modules. The user must be aware that the thermal resistance of the crust case of the flat panel device is directly affected by the mounting conditions. Only the mounting force recommended in the manual can be used to ensure that the thermal resistance of the device can meet the requirements.
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