Effect of temperature on the operating characteristics of thyristors

Semiconductor monocrystalline silicon is very sensitive to changes in ambient temperature, for example, its resistivity changes with temperature. When monocrystalline silicon is made into thyristor, the parameters of thyristor also change with the change of temperature. Although the thyristor can work normally over a wide temperature range, its parameters do change.

The influence of temperature on the variation of thyristor parameters is regular, and mastering this law can improve the initiative in selecting thyristors suitable for their own circuit characteristics; The second is that the cause of the failure can be found in time in the application, because the thyristor that violates this law should be a defective product.

Effect of temperature on positive and negative voltage resistance and leakage current

With the increase of ambient temperature, the thyristor will withstand positive and negative voltage, that is, the breakdown voltage will increase, and the leakage current will increase, as shown in (Figure 1). If the temperature rises and the withstand pressure decreases, it should be "defective products". The leakage current increases greatly with the increase of temperature, and the junction temperature at 125℃ is about a hundred times larger than that at room temperature. For example, the leakage current of a certain specification thyristor at room temperature is 0.05 mA, and the leakage current at 125℃ is dozens of MA or even larger.

When the thyristor operates at an allowable junction temperature of 125 ° C, it is called a high temperature state. Now the leakage current increases, plus

The minority carrier lifetime in PN junction increases with the increase of temperature, and the amplification coefficient increases. These two points cause the gate trigger current to decrease with the increase of temperature, and when it works at high temperature, it is much smaller than that at room temperature. In order to avoid too small trigger power to cause false trigger, the standard stipulates "no trigger voltage", "no trigger current" and other items, must be greater than this value to trigger the thyristor, otherwise it is unqualified. It should be noted that when leaving the factory, the gate current is the test value at room temperature and the anode voltage is 6V. When practical, it is high temperature and high pressure, which is easy to trigger on because the triggering current becomes smaller.