Rectification and filtering of DC regulated power supplies:
1. Classification of rectifier circuits
(1) According to the type of input AC power supply can be divided into single-phase rectification and three-phase rectification.
(2) According to the output power can be divided into small power and high power. Small power DC power supply is usually used single-phase rectifier, while for larger power DC power supply, usually using three-phase rectifier.
(3) According to the type of rectifier element can be divided into controllable rectifier and uncontrollable rectifier circuit. In the controllable rectifier circuit, by changing the on-time of the rectifier element to control the size of the output voltage; in the uncontrollable rectifier circuit, the on-time of the rectifier element is not controllable, when the input voltage of the rectifier circuit and the load must be certain, the output voltage must be.
2. The basic working principle of rectifier circuit
Rectifier circuit using the rectifier diode unidirectional conductivity, the alternating current into a unidirectional pulsating electricity, the output voltage contains a certain DC component.
3. Single-phase rectifier circuit and its main performance indicators
Set U2 for the rms voltage of the secondary side of the transformer, RL for the load resistance, Uo for the DC component of the circuit output voltage, UDRM for the diode to withstand the highest reverse voltage, ID for the average value of the current flowing through the diode. The single-phase rectifier circuit and its main performance indicators are shown in Table 1.
4. Filter circuit
(1) the role of the filter circuit
Filter circuit is the use of capacitance, inductance in the circuit of energy storage and its characteristics of different frequencies have different reactance to form a low-pass filter circuit to reduce the ripple in the output voltage.
(2) Capacitor Filter Circuit
The single-phase bridge rectifier capacitor filter circuit is shown in Fig. 10.1, and the external characteristics of this circuit are shown in Fig. 10.2.
(3) Characteristics of the capacitor filter circuit
① The average value of the output voltage Uo is greater than the RMS value of the voltage on the secondary side of the transformer U2.
When DC regulated power supply types and their selection, DC regulated power supply rectification and filtering
(T is the period of AC voltage), the average value of the output voltage
DC regulated power supply types and their selection, DC regulated power supply rectification and filtering
② The size of the output DC voltage is greatly affected by the load changes, suitable for the occasions where the load is unchanged or the output current is not large.
③ The larger the filter capacitance, the better the filtering effect.
The inrush current flowing through the diode is large, and the current parameter of the diode should be selected with a margin of 2~3 times.
(4) Other forms of filter circuit
In addition to capacitor filter circuit, there are also inductor filter, RC-π filter, LC-π filter and other circuits.
