The half-bridge switching power supply is also one of the most typical inverter-rectifier type converters, whose structure is shown in the following figure.
Half-bridge converter structure
Since C1 and C2 have the same capacity, their node voltages are equal to half of the input voltage Ui. When switches S1 and S2 are alternately on, the voltage applied to the switching transformer TR1 is half of Ui. We can control the output voltage by changing the conduction time of S1 and S2 . There is a taboo for the half-bridge converter, that is, to turn S1 and S2 on at the same time; if S1 and S2 are turned on at the same time, it will lead to the phenomenon that the two power tubes will short-circuit the input voltage UI, and the light one will be short-circuited and tripped, and the heavy one will be exploded and burned.
We have talked about push-pull converters before, their main devices are two switching tubes, so what is the difference between them?
The most basic difference between push-pull converter and half-bridge switching power supply is that: when the switches S1 and S2 are alternately on, the working voltage of the push-pull converter is Ui; while the working voltage of the half-bridge converter is 1/2 Ui; therefore, the half-bridge switching power supply has a lower utilization rate of the power supply than the push-pull switching power supply.
In order to solve the low utilization of the power supply by the half-bridge converter, we add two power tubes on the basis of the half-bridge switching power supply, which can form a full-bridge switching power supply.
Since the half-bridge power supply on the utility power utilization is not high, why should it exist, it comes to the advantages of the half-bridge switching power supply.
- Because the half-bridge switching power supply two working tubes alternately, equivalent to two switching power supply output power at the same time, the output power is equivalent to a single switching power supply twice, so the half-bridge switching power supply output power is very large, the output efficiency is very high, and the half-bridge switching power supply output voltage voltage pulsation coefficient Sv and current pulsation coefficient Si are very small, so at the output side only need Very small filtering inductors and capacitors are sufficient.
2.Half-bridge switching power supply has a very big advantage over the push-pull power supply, that is, the voltage requirements of the two switching devices than the push-pull switching power supply requirements can be reduced by half, because the half-bridge switching power supply two switching devices operating voltage is only half of the input voltage, the maximum withstand voltage is equal to the sum of the operating voltage and counter-electromotive force, about twice the supply voltage, this structure is exactly the push-pull type This structure is exactly half of the push-pull switching power supply two device voltage withstand value, so the half-bridge switching power supply is mainly used in the input voltage is relatively high.
3.Half-bridge switching power supply requires only one winding of the primary coil of the transformer, which is also its advantage, which is relatively easy to wind the coil of a small power switching transformer.
