On time and parameter selection of asemi rectifier bridge db207

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50Hz AC voltage becomes pulsating DC voltage after full wave rectification u1, Then the DC high voltage is obtained by inputting the filter capacitor U1. Ideally , Rectifier bridge DB207 The conduction angle of should be 180°（ The conduction range is 0° To 180°）, But because of the filter capacitor C The role of , It can only approach the AC peak voltage in a very short time , The input current flows through the rectifier bridge to C Charge .50Hz The half cycle of alternating current is 10ms, The conduction time of the rectifier bridge is tC≈3ms, Its conduction angle is only 54°（ The conduction range is 36°～90°）. therefore , Rectifier bridge DB207 What actually passes through is a narrow pulse current . The principle of bridge rectifier filter circuit is shown in the figure 1(a) Shown , The waveform of rectifier filter voltage and rectifier current are shown in Figure 1(b) and (c) Shown .

 

To sum up ：

(1) The above characteristics of the rectifier bridge can be equivalent to the input voltage frequency of about 30% Duty cycle of .

(2) The primary conduction process of rectifier diode can be regarded as a “ Gated pulse ”, Its pulse repetition frequency is equal to the frequency of AC power grid （50Hz）.

(3) In order to reduce 500kHz The following conducted noise , Sometimes, two ordinary silicon rectifiers and two fast recovery diodes are used to form a rectifier bridge .

 

Rectifier bridge DB207 Parameter selection of

The isolated switching power supply generally adopts the rectifier bridge composed of rectifier tubes , The finished rectifier bridge can also be directly selected to complete the bridge rectifier . Full wave bridge rectifier DB207 It is called silicon rectifier bridge , It connects four silicon rectifiers into a bridge circuit , A semiconductor device encapsulated in plastic .DB207 Small size 、 Easy to use 、 Good consistency of rectifier parameters , It can be widely used in the rectifier circuit of switching power supply . Silicon rectifier bridge DB207 Yes 4 Terminals , It includes two AC input terminals and two DC output terminals .

The average maximum rectified current of silicon rectifier bridge is divided into 0.5~40A And other specifications , The maximum reverse working voltage is 50~1000V And other specifications . Small power silicon rectifier bridge DB207 It can be directly welded on the printed board , And big 、 The medium power silicon rectifier bridge should be fixed with screws and installed with appropriate heat sinks .

Rectifier bridge DB207 The main parameters are reverse peak voltage URM(V)、 Forward pressure drop UF(V)、 Average rectified current Id(A)、 Forward peak surge current IFSM(A)、 Maximum reverse leakage current IR(μA).