High-power diode thyristor knowledge serial-control characteristics

Power diode thyristors are widely used in AC/DC converters, UPS, AC static switches, SVC and electrolytic hydrogen, etc. However, most engineers do not understand such bipolar devices as well as IGBTs. For this reason, we organized 6 Article serial, including forward characteristics, dynamic characteristics, control characteristics, protection, loss and thermal characteristics.

High-power diode thyristor knowledge serial-control characteristics

Power diode thyristors are widely used in AC/DC converters, UPS, AC static switches, SVC and electrolytic hydrogen, etc. However, most engineers do not understand such bipolar devices as well as IGBTs. For this reason, we organized 6 Article serial, including forward characteristics, dynamic characteristics, control characteristics, protection, loss and thermal characteristics. The content is extracted from Infineon’s “Bipolar semiconductor Technology Information”.

3.3 The control properties of the thyristor

3.3.1, front gate control

3.3.1.1, gate-level current iG

iG is the current flowing through the control channel (terminal G-HK).

The thyristor can only be triggered by pulses in the positive off-state phase.

Due to the Transistor effect, the forward trigger pulse in the reverse off-state phase will cause the off-state loss to increase greatly. This loss has an adverse effect ON functionality and may cause component damage.

Exception: For light-triggered transistors, control pulses in the reverse off-state phase are allowed.

3.3.1.2 Gate voltage VG

VG is the forward Voltage applied to the gate terminal (G) and cathode (K) or auxiliary cathode (HK).

3.3.1.3 Gate trigger current IGT

IGT is the minimum gate current value required to trigger the thyristor. This value depends on the voltage between the main terminals and the junction temperature. Under the specified gate trigger current value, all specified types of thyristors will be triggered. The gate trigger current increases as the junction temperature decreases, so this value is specified at 25°C.

The trigger pulse generator must safely exceed the data sheet value IGTmax (see also 3.3.1.8).

Exception: For light-triggered thyristors, the minimum optical power required to trigger all specified types of thyristors is specified.

3.3.1.4 Gate trigger voltage VGT

VGT refers to the voltage generated between the gate terminal and the cathode when the gate trigger current IGT flows. This value depends on the voltage between the main terminals and the junction temperature. Under the specified gate trigger voltage value, all specified types of thyristors will be triggered. The gate trigger voltage decreases as the junction temperature increases, so this value is specified at 25°C. Measure VGT when the specified load current flows.

3.3.1.5 The gate does not trigger the current IGD

IGD is the value of the gate current at which the thyristor does not trigger. This value depends on the voltage between the main terminals and the junction temperature. When the specified maximum value is reached, the specified type of thyristor does not trigger. The gate non-triggering current decreases as the junction temperature increases, so specify this value under Tvj max.

3.3.1.6 The gate does not trigger voltage VGD

VGD is the gate voltage value at which the thyristor does not trigger. This value depends on the voltage between the main terminals and the junction temperature. When the specified maximum value is reached, the specified type of thyristor does not trigger. The gate non-triggering voltage decreases as the junction temperature increases, so specify this value under Tvj max.

High-power diode thyristor knowledge serial-control characteristics
Figure 14. When VD=12V, the control characteristic vG=f(iG) trigger area example

3.3.1.7 Control characteristics

The control characteristic shows the statistical distribution limit of the input characteristic of a certain type of thyristor. The statistical distribution diagram of the input characteristics shows in detail the temperature-dependent trigger area and the maximum allowable gate power dissipation curve PGM (a-20W/10ms, b-40W/1ms, c-60W/0.5ms).

3.3.1.8 Control circuit

In conventional applications, the control circuit should be designed according to the control data. This article describes in detail the relationship between the control data and the critical rise time of the on-state current, the gate control delay time and the holding current (see Figure 15).

The minimum control data provided in 3.3.1.3 and 3.3.1.4 are only valid for applications that require less critical current rise time and gate control time. In fact, overdrive 4 to 5 times the IGT specified in the data sheet can ensure safe operation, even in the case of higher requirements for current rise time and gate control delay time. The meanings of related terms are as follows:

diG/dt=gate current conversion rate

iGM=gate peak current

tG = duration of trigger pulse

VL = open circuit voltage of the control circuit

As the slew rate of the on-state current diT/dt and the repeated on current IT(RC)M from the snubber circuit increases, attention should be paid to the influence of the load circuit on the gate current iG (see 3.4.1.2 and Figure 21).

High-power diode thyristor knowledge serial-control characteristics
Figure 15. Design of thyristor trigger circuit

During the turn-on process of the thyristor, initially only a small area near the gate area of ​​the die is turned on, resulting in high current density and voltage rise. Due to internal coupling, this voltage also appears at the control terminal, thus causing the gate trigger current to drop moderately. In order to avoid possible damage to the thyristor, iG must not drop below the gate trigger current IGT. In order to prevent the gate pulse from falling excessively, it may be necessary to compensate by increasing the open circuit voltage VC of the trigger circuit. For thyristors connected in parallel or in series, in order to achieve the same turn-on effect, it is necessary to use a sharply rising synchronous high pulse. See also the distribution of gate control delay time values ​​(3.4.1.2.1).

Exception: In order to control the light-triggered thyristor, the laser diode is required to emit light in the region of 900 to 1000 nm. The minimum value of the specified optical power PL and the specified turn-on voltage can ensure the safe triggering of the thyristor. The optical power is determined at the output end of the optical cable. Even for turn-on, over-excitation is recommended, especially for series or parallel connections with high di/dt requirements.

Infineon recommends aligning the laser diode SPL PL90 with suitable accessories before using it (see Figure 16). Infineon provides the laser diode, alignment accessories and optical cable together as auxiliary devices.

High-power diode thyristor knowledge serial-control characteristics
Figure 16. LTT with fiber optic cable

High-power diode thyristor knowledge serial-control characteristics

The laser diode SPL PL 90 complies with the following laser categories: If the end of the laser diode is an optical cable, the control system complies with Class 1 laser. No risk of operation.

If the laser diode is open for operation or the optical cable is broken, the control system is a Class 3b laser as described in IEC 60825-1. At this time, there is a risk of operation due to invisible radiation. Avoid direct or indirect contact with eyes or skin.

High-power diode thyristor knowledge serial-control characteristics
Figure 17. Typical relationship curve between optical power of laser diode SPL PL 90 and control current

In order to control the light-triggered thyristor, we recommend applying current pulses to the laser diode SPL PL90, as shown in Figure 18. The diode SPL PL90 is not suitable for long-term control, so we recommend using a frequency of about 6kHz and the pulse shown in Figure 18 to control the laser diode.

High-power diode thyristor knowledge serial-control characteristics
Figure 18. Recommended current pulse applied to the laser diode SPL PL 90

3.3.1.9 The shortest duration of the trigger pulse tgmin

At least the trigger pulse should be applied after exceeding the holding current (3.1.6) of the thyristor, otherwise the thyristor will return to the off state. Before the end of the trigger pulse, the gate trigger current of the thyristor must be maintained at least at the rated value.

For applications with very short current rise times or low load currents, trigger curves with multiple pulses (for example, a repetition frequency of 6kHz) are usually used.

For light-triggered thyristors, ensure that the temperature of the laser diode is within the allowable range when using multiple pulses. The optical power of a current-controlled laser diode decreases with increasing temperature.

3.3.1.10 Maximum allowable peak trigger current

For applications with a high rate of rise, the overdrive degree of the current iGT may be higher than described in 3.3.1.8. In this case, the gate current should be increased to 8 to 10 times that of IGT within tG=10 to 20μs, and then the amplitude should be reduced and maintained for a sufficient time tG. In order to ensure high inertia gate current, the open circuit voltage of the trigger circuit should be at least 30V.

High-power diode thyristor knowledge serial-control characteristics
Figure 19. Safe overdrive of gate trigger current

High-power diode thyristor knowledge serial-control characteristics

Power diode thyristors are widely used in AC/DC converters, UPS, AC static switches, SVC and electrolytic hydrogen, etc. However, most engineers do not understand such bipolar devices as well as IGBTs. For this reason, we organized 6 Article serial, including forward characteristics, dynamic characteristics, control characteristics, protection, loss and thermal characteristics. The content is extracted from Infineon’s “Bipolar Semiconductor Technology Information”.

3.3 The control properties of the thyristor

3.3.1, front gate control

3.3.1.1, gate-level current iG

iG is the current flowing through the control channel (terminal G-HK).

The thyristor can only be triggered by pulses in the positive off-state phase.

Due to the Transistor effect, the forward trigger pulse in the reverse off-state phase will cause the off-state loss to increase greatly. This loss has an adverse effect on functionality and may cause component damage.

Exception: For light-triggered transistors, control pulses in the reverse off-state phase are allowed.

3.3.1.2 Gate voltage VG

VG is the forward voltage applied to the gate terminal (G) and cathode (K) or auxiliary cathode (HK).

3.3.1.3 Gate trigger current IGT

IGT is the minimum gate current value required to trigger the thyristor. This value depends on the voltage between the main terminals and the junction temperature. Under the specified gate trigger current value, all specified types of thyristors will be triggered. The gate trigger current increases as the junction temperature decreases, so this value is specified at 25°C.

The trigger pulse generator must safely exceed the data sheet value IGTmax (see also 3.3.1.8).

Exception: For light-triggered thyristors, the minimum optical power required to trigger all specified types of thyristors is specified.

3.3.1.4 Gate trigger voltage VGT

VGT refers to the voltage generated between the gate terminal and the cathode when the gate trigger current IGT flows. This value depends on the voltage between the main terminals and the junction temperature. Under the specified gate trigger voltage value, all specified types of thyristors will be triggered. The gate trigger voltage decreases as the junction temperature increases, so this value is specified at 25°C. Measure VGT when the specified load current flows.

3.3.1.5 The gate does not trigger the current IGD

IGD is the value of the gate current at which the thyristor does not trigger. This value depends on the voltage between the main terminals and the junction temperature. When the specified maximum value is reached, the specified type of thyristor does not trigger. The gate non-triggering current decreases as the junction temperature increases, so specify this value under Tvj max.

3.3.1.6 The gate does not trigger voltage VGD

VGD is the gate voltage value at which the thyristor does not trigger. This value depends on the voltage between the main terminals and the junction temperature. When the specified maximum value is reached, the specified type of thyristor does not trigger. The gate non-triggering voltage decreases as the junction temperature increases, so specify this value under Tvj max.

High-power diode thyristor knowledge serial-control characteristics
Figure 14. When VD=12V, the control characteristic vG=f(iG) trigger area example

3.3.1.7 Control characteristics

The control characteristic shows the statistical distribution limit of the input characteristic of a certain type of thyristor. The statistical distribution diagram of the input characteristics shows in detail the temperature-dependent trigger area and the maximum allowable gate power dissipation curve PGM (a-20W/10ms, b-40W/1ms, c-60W/0.5ms).

3.3.1.8 Control circuit

In conventional applications, the control circuit should be designed according to the control data. This article describes in detail the relationship between the control data and the critical rise time of the on-state current, the gate control delay time and the holding current (see Figure 15).

The minimum control data provided in 3.3.1.3 and 3.3.1.4 are only valid for applications that require less critical current rise time and gate control time. In fact, overdrive 4 to 5 times the IGT specified in the data sheet can ensure safe operation, even in the case of higher requirements for current rise time and gate control delay time. The meanings of related terms are as follows:

diG/dt=gate current conversion rate

iGM=gate peak current

tG = duration of trigger pulse

VL = open circuit voltage of the control circuit

As the slew rate of the on-state current diT/dt and the repeated on current IT(RC)M from the snubber circuit increases, attention should be paid to the influence of the load circuit on the gate current iG (see 3.4.1.2 and Figure 21).

High-power diode thyristor knowledge serial-control characteristics
Figure 15. Design of thyristor trigger circuit

During the turn-on process of the thyristor, initially only a small area near the gate area of ​​the die is turned on, resulting in high current density and voltage rise. Due to internal coupling, this voltage also appears at the control terminal, thus causing the gate trigger current to drop moderately. In order to avoid possible damage to the thyristor, iG must not drop below the gate trigger current IGT. In order to prevent the gate pulse from falling excessively, it may be necessary to compensate by increasing the open circuit voltage VC of the trigger circuit. For thyristors connected in parallel or in series, in order to achieve the same turn-on effect, it is necessary to use a sharply rising synchronous high pulse. See also the distribution of gate control delay time values ​​(3.4.1.2.1).

Exception: In order to control the light-triggered thyristor, the laser diode is required to emit light in the region of 900 to 1000 nm. The minimum value of the specified optical power PL and the specified turn-on voltage can ensure the safe triggering of the thyristor. The optical power is determined at the output end of the optical cable. Even for turn-on, over-excitation is recommended, especially for series or parallel connections with high di/dt requirements.

Infineon recommends aligning the laser diode SPL PL90 with suitable accessories before using it (see Figure 16). Infineon provides the laser diode, alignment accessories and optical cable together as auxiliary devices.

High-power diode thyristor knowledge serial-control characteristics
Figure 16. LTT with fiber optic cable

High-power diode thyristor knowledge serial-control characteristics

The laser diode SPL PL 90 complies with the following laser categories: If the end of the laser diode is an optical cable, the control system complies with Class 1 laser. No risk of operation.

If the laser diode is open for operation or the optical cable is broken, the control system is a Class 3b laser as described in IEC 60825-1. At this time, there is a risk of operation due to invisible radiation. Avoid direct or indirect contact with eyes or skin.

High-power diode thyristor knowledge serial-control characteristics
Figure 17. Typical relationship curve between optical power of laser diode SPL PL 90 and control current

In order to control the light-triggered thyristor, we recommend applying current pulses to the laser diode SPL PL90, as shown in Figure 18. The diode SPL PL90 is not suitable for long-term control, so we recommend using a frequency of about 6kHz and the pulse shown in Figure 18 to control the laser diode.

High-power diode thyristor knowledge serial-control characteristics
Figure 18. Recommended current pulse applied to the laser diode SPL PL 90

3.3.1.9 The shortest duration of the trigger pulse tgmin

At least the trigger pulse should be applied after exceeding the holding current (3.1.6) of the thyristor, otherwise the thyristor will return to the off state. Before the end of the trigger pulse, the gate trigger current of the thyristor must be maintained at least at the rated value.

For applications with very short current rise times or low load currents, trigger curves with multiple pulses (for example, a repetition frequency of 6kHz) are usually used.

For light-triggered thyristors, ensure that the temperature of the laser diode is within the allowable range when using multiple pulses. The optical power of a current-controlled laser diode decreases with increasing temperature.

3.3.1.10 Maximum allowable peak trigger current

For applications with a high rate of rise, the overdrive degree of the current iGT may be higher than described in 3.3.1.8. In this case, the gate current should be increased to 8 to 10 times that of IGT within tG=10 to 20μs, and then the amplitude should be reduced and maintained for a sufficient time tG. In order to ensure high inertia gate current, the open circuit voltage of the trigger circuit should be at least 30V.

High-power diode thyristor knowledge serial-control characteristics
Figure 19. Safe overdrive of gate trigger current

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