So what does the rectifier bridge do, and where can it be used? Is it the same as using a diode to s

When people want to turn alternating current into direct current, they need this circuit. Because the direction of alternating current flow is a current that changes alternately repeatedly, and direct current flows in one direction, people use the unidirectional conductivity of the diode to convert the current into a direction of current, and a diode is used for half-wave rectification, so half of the current that comes out is not called half-wave rectification, which is used in occasions where the requirements for direct current are not very strict. With four diodes, all wave types of alternating current can be converted into current in a single direction, so it is called full-wave rectification.

Generally, a filter capacitor needs to be added to remove the clutter after rectification, and the polarity cannot be reversed. Full-wave rectified circuits are often used in conventional transformers.

The function of the rectifier bridge is to turn alternating current into direct current (in fact, it turns alternating current in both directions into fluctuating DC in one direction). In most cases, it is used in the case of AC to DC, which can directly convert 220V into DC, or convert AC power converted by transformer into DC. In a few cases, it can also be used in other circuits.

It is not a diode that divides half of the current, but in half of the cycle of the alternating current, two opposing diodes are turned on, and the other two opposing diodes are cut off. And the other half of the cycle is interchangeable between conduction and cut-off, and so on. Their output current is passed through the load (i.e., the subsequent circuit).

Replace the rectifier bridge with four diodes, and the connection method of the diodes is as follows:

The polarity of the diode is arranged in such a way that the two positive outputs are negative and the two negative outputs are positive.

The rules of diode wiring are: positive to negative, negative to positive, one positive and one negative to AC.

The principle of a bridge rectifier.

The most commonly used circuit that uses the unidirectional conductivity of a diode for rectification is used to convert alternating current to direct current.

Bridge rectifiers utilize four diodes, which are docked in pairs. The positive part of the input sine wave is that the two tubes are turned on to obtain a positive output; When the negative half of the sine wave is input, the other two tubes are turned on, and since the two tubes are reversed, the output still gives the positive half of the sine wave.

It is important to note that:

As a rectifier element, the diode should be selected according to different rectification methods and load sizes. If the choice is not right, it may not work safely, or even burn the pipe; Or overkill, resulting in waste.

The selection of rectifier diodes generally follows the following principles:

When the on-voltage is low, the germanium diode is selected;

When the on-voltage is high, the silicon diode is selected;

Silicon diodes are required to be selected for reverse current hours;

When the reverse breakdown voltage is high, the silicon diode is selected;

Silicon diodes are selected when high temperature resistance is required;

When the on-current is large, the surface contact diode is selected;

When a high operating frequency is required, a point-contact diode is selected.

You're talking about the rectifier filter circuit before switching the power supply. In a bridge rectifier circuit, the back voltage experienced by the diode is equal to the peak of the AC input voltage, and the forward average rectification current flowing through the diode is only half of the load current. Therefore, when selecting a diode, as long as the withstand voltage of the diode is greater than the peak value of the AC input voltage, the forward average rectification current is greater than half of the load current.

For safety reasons, these parameters should be selected 20% higher

The current frequency in the switching power supply is very high, generally there are tens of khz, at this time can not use 1N4007, the working frequency of 1N4007 is too low, it has been tested before, under the condition of 80kHz, 1N4007 either burns or does not work, at least to replace the fast recovery diode, such as FR107 or UR107, these are diodes under 1A conditions, the recovery time of these diodes is much shorter than that of 1N4007, but the withstand voltage is the same. If the current is higher, you can use the FR307 with a current of 3A, and other characteristics are the same as the 1N5408, but the reverse recovery time is much shorter.

Bridge rectifier circuits use four diodes for the following reasons:

When e2 is positive for half a cycle, add forward voltage to d1 and d3, and d1 and d3 are turned on; Add reverse voltage to D2 and D4, and cut off D2 and D4. The circuit is composed of E2, D1, RFZ, D3 energizing circuit, forming a positive and negative half-wave rectification voltage on the RFZ, when E2 is negative for half a cycle, add positive voltage to D2 and D4, and D2 and D4 are turned on;

Add reverse voltage to D1 and D3, and cut off D1 and D3. The circuit is composed of E2, D2, RFZ, and D4 energizing circuits, and the other half wave of rectifier voltage is also formed on the RFZ.

Repeating this results in a full-wave rectification voltage on the RFZ. The waveform is the same as the full-wave rectifier waveform. It is not difficult to see from the diagram that the reverse voltage experienced by each diode in the bridge circuit is equal to the maximum value of the transformer's secondary voltage, which is half smaller than that of the full-wave rectifier circuit.

Generally, rectifier diodes or Schottky diodes are used, such as 1N4000 1N4007 (rectifier tube, maximum continuous current 1A), Schottky tubes are characterized by low forward voltage drop, left and right (rectifier tubes are generally left and right), Schottky tubes are often used for lower AC voltage rectification, which can reduce the voltage loss in the rectification process. As you said, it is more appropriate to use Schottky diodes, the peak value of the sine wave AC voltage is multiple of the effective value, for example, the peak value of the sine wave AC voltage is about the left, and the forward voltage drop of the two diodes will be lost after the bridge rectification.

A rectifier diode, a semiconductor device used to convert alternating current into direct current. Usually it contains a PN junction with two terminals, an anode and a cathode. The structure is shown in Figure 1.

The carriers in the p-region are holes, and the carriers in the n-region are electrons, forming a certain barrier in the p-region and the n-region. When a voltage is applied that makes the p-region positive relative to the n-region, the barrier is lowered, and stored carriers are generated near both sides of the barrier, which can pass through large currents and have a low voltage drop (the typical value is called the forward conduction state). If the opposite voltage is added, the barrier increases, and it can withstand a high reverse voltage, and a small reverse current (called reverse leakage current) flows, which is called the reverse blocking state.

Rectifier diodes have significant unidirectional conductivity. Rectifier diodes can be manufactured from materials such as semiconductor germanium or silicon. The silicon rectifier diode has a high breakdown voltage, low reverse leakage current, and good high-temperature performance.

Generally, high-voltage and high-power rectifier diodes are made of high-purity monocrystalline silicon (easy to reverse breakdown when doped more). This device has a large junction area and can pass through a large current (up to thousands of amperes), but the operating frequency is not high, generally below tens of kilohertz. Rectifier diodes are mainly used in various low-frequency half-wave rectifier circuits, and need to be connected to a rectifier bridge to achieve full-wave rectification.

No.20 06 Electron: What is rectification and how is a diode rectified? What is the principle of a rectifier bridge.

Regardless of whether it is a positive half-cycle or a sub-half-cycle, a complete loop must be formed to complete the full-wave rectification. In the power frequency input rectification, you must use 4 tubes to complete the complete full-wave rectification, you can divide the positive half cycle and the secondary half cycle to analyze the diodes through which the current flows separately, and you can understand that there are only 4 of them. The rectification at the back end of the transformer can be completed by 2 rectifier tubes, but there must be a center tap, that is to say, at least 2 sets of secondary sides must be used to complete the half-wave rectification.

If there is only one set of secondary sides and no center tap, 4 tubes are required to complete the full-wave rectification. It's a bit verbose, I don't know if it's explained.

Right! It stands to reason that full-wave rectification can be achieved with two rectifier tubes. Why use 4 pcs? Mainly to save the cost of the transformer, the transformer can reduce one low-voltage winding. Four diodes are used to form a full bridge, and the power supply is picked up for two cycles at the same time.