Introduction of Bridge Transformer Switching Power Supply
The half bridge transformer switching power supply is similar to the push-pull transformer switching power supply. Due to the alternating operation of two switching transistors, it is equivalent to two switching power supplies simultaneously outputting power, which is about twice the output power of a single switching power supply. Therefore, the half bridge transformer switching power supply has a high output power and high working efficiency. After bridge rectification or full wave rectification, the voltage ripple coefficient Sv and current ripple coefficient Si of the output voltage are very small, and only a small filter inductor and capacitor are needed. The output voltage ripple and current ripple can be achieved very small.
The biggest advantage of a half bridge transformer switching power supply is that the voltage requirements for two switching devices can be reduced by half compared to the voltage requirements for two switching devices in a push-pull transformer switching power supply. Because the working voltage of the two switching devices in the half bridge transformer switching power supply is only half of the input power supply Ui, its highest withstand voltage is equal to the sum of the working voltage and the back electromotive force, which is approximately twice the power supply voltage. This result is exactly half of the withstand voltage of the two switching devices in the push-pull transformer switching power supply. Therefore, half bridge transformer switching power supplies are mainly used in situations where the input voltage is relatively high. Most high-power switching power supplies powered by AC 220V in the general power grid use half bridge transformer switching power supplies.
The primary coil of the transformer in the half bridge switching power supply only requires one winding, which is also its advantage. This brings some convenience to the winding of the coil in low-power switching power supply transformers. But there is no advantage in winding the coils of high-power switching power transformers, because the coils of high-power switching power transformers need to be wound with multiple strands of wire.
The main disadvantage of half bridge transformer switching power supply is that the power utilization rate is relatively low. Therefore, half bridge transformer switching power supply is not suitable for applications with low operating voltage. In addition, the two switching devices in the half bridge transformer switching power supply are not connected to a common ground, which makes it difficult to connect with the driving signal.
The biggest disadvantage of a half bridge switching power supply is that when the two control switches K1 and K2 are in alternating switching operation, both switching devices will simultaneously have a short period of semi conducting region, that is, both control switches will be in the on state at the same time. This is because when the switching device starts to conduct, it is equivalent to charging the capacitor, and it requires a transitional process from the off state to the fully conducting state; When the switching device transitions from the conducting state to the cutoff state, it is equivalent to discharging the capacitor, and it also requires a transitional process from the conducting state to the completely cutoff state.
