Magnetic saturation transient effect of transformer
The magnetic saturation transient effect of transformer should pay attention to whether the flux is near saturation under the condition of minimum input voltage and maximum pulse width. Because the pulse width will narrow when the input voltage is high, the core is far away from saturation.
When the transient load is high, and the load current is small, if the load current increases suddenly, the control circuit will increase the pulse width immediately to provide the supplementary power. In this way, both the input voltage and the pulse width change to the maximum at the same time, even if only a short time, the transformer will also appear to be saturated, and cause out of control and failure. Here are several measures to avoid out of control. (1) the transformer is designed according to high input voltage and wide pulse to make the core work at low magnetic flux density and winding more primary winding. The disadvantage of this method is to reduce the efficiency of the transformer and increase the volume and weight of the transformer. (2) the control circuit should work in a highly sensitive state. When the high input voltage occurs, it can quickly limit the pulse width and keep it at a safe value. (3) improve the performance of the control circuit so that the switch tube can react quickly in the current working cycle. The UC1846 / UC1847 current mode control chip can automatically carry out such limiting action.
When the transient load is high, and the load current is small, if the load current increases suddenly, the control circuit will increase the pulse width immediately to provide the supplementary power. In this way, both the input voltage and the pulse width change to the maximum at the same time, even if only a short time, the transformer will also appear to be saturated, and cause out of control and failure. Here are several measures to avoid out of control. (1) the transformer is designed according to high input voltage and wide pulse to make the core work at low magnetic flux density and winding more primary winding. The disadvantage of this method is to reduce the efficiency of the transformer and increase the volume and weight of the transformer. (2) the control circuit should work in a highly sensitive state. When the high input voltage occurs, it can quickly limit the pulse width and keep it at a safe value. (3) improve the performance of the control circuit so that the switch tube can react quickly in the current working cycle. The UC1846 / UC1847 current mode control chip can automatically carry out such limiting action.