description:
The rectified output push-pull transformer switching power supply, because the two switching tubes alternately work in turn, is equivalent to two switching power supplies simultaneously outputting power, and its output power is approximately equal to twice the output power of a single switching power supply. Therefore, the push-pull transformer switching power supply has a large output power and high working efficiency. After bridge rectification or full-wave rectification, only a small filter inductor and capacitor are needed, and the output voltage ripple can be very small.
Figure 1-30 shows the working principle of the bridge rectifier output push-pull transformer power supply. Except for the rectifier filter circuit, the other parts of the circuit work basically the same as Figure 1-27. The bridge rectifier circuit consists of D1, D2, D3, and D4. C is the energy storage filter capacitor, R is the load resistor, Uo is the DC output voltage, and Io is the current flowing through the load resistor. Figure 1-31 shows the working principle of the push-pull transformer switching power supply with full-wave rectified output. Similarly, except for the rectifying and filtering circuit, the working principle of the other circuits is basically the same as that of Figure 1-27 and Figure 1-30. However, the secondary of the switching transformer needs one more winding, the two windings N31 and N32 take turns to output voltage; the full-wave rectifier circuit consists of D1 and D2, C is the energy storage filter capacitor, R is the load resistance, Uo is the DC output voltage, Io Is the current flowing through the load resistor.
Figure 1-30 compares with Figure 1-31. The bridge-type rectified output push-pull transformer switching power supply uses two rectifier diodes instead of the full-wave rectified output push-pull transformer switching power supply, but the full-wave rectified output switching transformer is The switching rectifier of the bridge rectifier output has a set of secondary coils. Therefore, Figure 1-30 Bridge Rectifier Output Push-Pull Transformer Switching Power Supply is more suitable for the case where the output current is relatively small; and Figure 1-31 Full-wave rectified output push-pull transformer switching power supply is more suitable for relatively large output current. Case. Because of the high cost of high current rectifier diodes, the power loss is also relatively large. Below we will analyze in detail the working principle of Figure 1-30 Bridge Rectifier Output Push-Pull Transformer Switching Power Supply and Figure 1-31 Full-Wave Rectified Output Push-Pull Transformer Switching Power Supply.
Because Figure 1-30 bridge rectifier output push-pull transformer switching power supply or Figure 1-31 full-wave rectification output push-pull transformer switching power supply voltage output circuit is connected with energy storage filter capacitor, energy storage filter capacitor will input The ripple voltage plays a smoothing role. Therefore, the output voltage Uo in Figure 1-30 and Figure 1-31 does not exhibit a very high voltage kickback. The peak value of the output voltage is basically considered to be a half-wave average. The value is Upa. The value is slightly larger than the forward output nUi, that is, the bridge rectifier output push-pull transformer switching power supply or the full-wave rectification output push-pull transformer switching power supply, the value of the rectified and filtered output voltage Uo is slightly larger than the forward output nUi, n is the transformer The turns ratio of the secondary winding N3 winding to the primary winding N1 winding or the N2 winding.
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