Nowadays, the energy-saving lamps and electronic ballast special transistors introduced by the industry pay great attention to the control of storage time. Because the storage time ts is too long, the oscillation frequency of the circuit will drop, and the increase of the working current of the whole machine will easily lead to the damage of the triode. Although the choke coil inductance and other component parameters can be adjusted to control the power of the whole machine, the discrete nature will make the product consistency poor and reliability reduced. For example, in a quartz lamp electronic transformer circuit, a transistor with too long a storage time may cause the circuit to oscillate at a frequency lower than the operating limit of the output transformer, resulting in saturation of the core at the end of each cycle, which makes the transistor Ic appear in each cycle Spikes, and finally cause overheating and damage to the device.
If the storage time of the two transistors on the same line is too different, the upper and lower half waves of the working current of the whole machine will be severely asymmetric, the heavy-duty transistor will be easily damaged, and the line will also produce more harmonics and electromagnetic interference.
Practical use shows that strict control of storage time and proper adjustment of the complete circuit can reduce the degree of dependence on hFE parameters. It is also worth mentioning that under the condition of a certain chip area, triode characteristics, current characteristics and withstand voltage parameters are contradictory. The Chinese market once used BUT11A as a 220V40W electronic ballast. The starting point is that the BVceo and BVcbo values are high. However, in most electronic ballast circuits, it is no longer necessary to select the voltage parameters of the transistors too high.