Bi-pressure Rectification Circuit

In applications requiring high voltage and low current, a voltage-doubling rectifier circuit is often employed. Voltage-doubling rectification can convert a lower AC voltage into a higher DC voltage using rectifier diodes and capacitors with lower voltage ratings. Voltage-doubling rectifier circuits are typically categorized based on the output voltage to input voltage ratio, including double-voltage, triple-voltage, and multi-voltage rectifier circuits. Figure 14 depicts a double-voltage rectifier circuit. The circuit consists of transformer B, two rectifier diodes D1, D2, and two capacitors C1, C2. Its operating principle is as follows:

During the positive half-cycle (upper positive, lower negative), diode D1 conducts while D2 is blocked. Current flows through D1 to charge capacitor C1, raising the voltage on C1 to nearly the peak of e2 and maintaining it relatively constant. During the negative half-cycle (upper negative, lower positive), diode D2 conducts while D1 is blocked. At this point, the voltage Uc1 on C1 is the sum of the supply voltage e2串联 added together. Current flows through D2 to charge capacitor C2, with the charging voltage Uc2 being approximately e2 peak + 1.2E2. This charging process is repeated, and the voltage on C2 becomes relatively stable. This value is twice the transformer's winding voltage, hence the name "double-voltage rectifying circuit."

In actual circuits, the voltage across the load, Usc, is equal to 2 times 1.2E2. The rectifier diodes, D1 and D2, both bear the maximum reverse voltage. The direct current voltages across the capacitors, Uc1 and Uc2, are such that they can be used to design the circuit and select the components.

Based on a double-voltage rectifying circuit, by adding a rectifying diode D3 and a filter capacitor C3, a triple-voltage rectifying circuit can be formed, as shown in Figure 5-15. The working principle of the triple-voltage rectifying circuit is as follows: during the first and second half-cycles of e2, it is the same as that of the double-voltage rectifying circuit, meaning the voltage on C1 is charged to near, and the voltage on C2 is charged to near. When it's the third half-cycle, D1 and D3 conduct, while D2 is off. The current, in addition to charging C1 through D1, also charges C3 through D3. The charged voltage on C3, Uc3 = e2 peak + Uc2 - Uc1 ≈, at the RFZ output, can produce a DC voltage Usc = Uc1i + Uc3 ≈ + = 3√2 E., achieving triple-voltage rectification.

In actual circuits, the maximum reverse voltage borne by the rectifying diode D3 on the load, which is approximately equal to 3 times 1.2 times 10 to the power of 2, is also the DC voltage on the capacitor.

By this method, adding multiple diodes and an equal number of capacitors can form a multi-stage rectifier circuit, as shown in Figure 5-16. When n is an odd number, the output voltage is taken from the top; when n is an even number, the output voltage is taken from the bottom.

It should be noted that a voltage multiplier circuit operates only under light load conditions (i.e., with a larger Rfz, resulting in smaller output current). Otherwise, the output voltage will decrease. The higher the voltage multiplication, the more pronounced this situation becomes where the output voltage drops due to increased load current.

Diodes for boost rectifier circuits should have a maximum reverse voltage greater than. High-voltage silicon rectifier stacks, such as the series model 2DL, are available. For example, 2DL2/0.2 indicates a maximum reverse voltage of 2 kilovolts and an average rectifying current of 200 milliamperes. The capacitors used in the boost rectifier circuit have a smaller capacity and do not require electrolytic capacitors. The capacitor's withstand voltage should be greater than 1.5x for safe and reliable operation.