The rectifier bridge is one of the most important devices in the power rectifier circuit, which functions to convert AC power into DC power. In practice, some customers lack the relevant cognitive knowledge and do not know how to use the rectifier bridge. In this paper, ASEMI engineers will answer the questions about whether the voltage rectifier of the rectifier bridge will change the voltage level of the circuit and the output voltage of the rectifier bridge.

01.  In principle, the rectifier bridge does not change the voltage in the circuit.

We can inquire about publicly available materials such as Baidu Encyclopedia. The design principle of the rectifier bridge is explained: four diode chips with single-pass characteristics are packaged in a shell by bridge circuit connection, and four leads are used to facilitate the connection. External circuits are connected. As shown in the following figure, Baidu Encyclopedia and other publicly available materials explain the working principle of the rectifier bridge. Two sets of diodes alternately work in turn, so that the load end obtains continuous uninterrupted current. The use of the rectifier bridge doubles the working efficiency compared to the half-wave rectifier circuit, and solves the complicated operation of the full-wave rectifier circuit requiring the center tap of the front-end transformer.

According to the working principle of the rectifier bridge, we can know that after the rectifier bridge, only the polarity direction of the AC power will be changed, so that the power load terminal can obtain continuous working current. Under theoretical conditions (regardless of subtle self-loss such as voltage drop), the voltage is not changed, and the potential energy of the output voltage is approximately equal to the potential energy of the input voltage.

02 .  What is the output voltage of the actual rectifier bridge back?

1. The output voltage rises after the rectifier bridge

The AC input to the front end of the rectifier bridge is represented by an effective value, and the DC output of the back end is represented by an average value. 220V is the rms value of AC power, and the maximum peak value of 220V AC power is (root 2 times = 1.4148) or 311V. Because the rectifier bridge can only change the polarity direction of the AC power and does not change the magnitude of the current and voltage, the output voltage after the rectifier bridge is pulsed DC voltage (shown in the waveform below). Because this voltage is not stable enough, it cannot be used by many devices. Direct use, so in most circuits will add large capacitor filter, voltage regulator, constant voltage constant current or current limit and other functional circuits. When the capacitor is filtered while smoothing the voltage, it is also charged, and the voltage rise at both ends is superimposed on the circuit. In the limit case, the peak value of the AC voltage can reach 311V. Therefore, the phenomenon that the output voltage rises after rectification is caused, and the actually measured voltage is generally higher than the effective value of the front-end alternating current 220V, which is lower than the peak value of 311V.

2. The output voltage is reduced after the rectifier bridge

When in a purely resistive circuit, no capacitive filtering is applied. After the rectifier bridge, the output sinusoidal pulse DC voltage is directly applied to the back-end equipment. The output DC component is the front-end AC voltage minus the bridge voltage drop. We use the formula 220-(1.05+1.05) to be equal to the 218V DC output voltage, and the voltage is slightly reduced. .

In summary, we know that the DC voltage output through the rectifier bridge ranges from 218V to 311V. In actual circuit operation, in most cases, the lowest voltage point is set by adjusting the capacitance configuration parameter.

03.  Is it feasible to get the required working voltage directly after the rectifier bridge?

We have already talked about the design and working principle of the rectifier bridge. The function of the rectifier bridge can only convert the alternating current with large fluctuations and polarity into a sinusoidal pulsating DC with the same polarity and polarity. It does not have the lifting pressure and change. The function of the current size. Some customers ideally believe that it is unrealistic to directly output the desired voltage after the rectifier bridge, such as 12V, 19V, 24V. To achieve the function of step-up and step-down, it is necessary to use a transformer to achieve all the required voltage parameters by adjusting the parameters of the transformer or by dividing the voltage of the energy-consuming device.

The above is the whole content of this paper on whether the voltage rectifier of the rectifier bridge will change the voltage magnitude of the circuit and the output voltage of the rectifier bridge. hope this would be helpful to you.ASEMI Semiconductor has been focusing on power rectifiers for 12 years, providing you with a range of solution services.