Views:80 Author:Site Editor Publish Time: 2019-11-29 Origin:Site
DC power converter is a voltage converter which can effectively output fixed voltage after converting input voltage. There are three types of DC power converter: step-up DC power converter, step-down DC power converter, and buck-boost DC power converter. Three kinds of control can be adopted according to the demand. PWM control type has high efficiency and good output voltage ripple. PFM control type has the advantage of low power consumption even if it is used for a long time, especially under small load. Because PFM control is implemented at small load, and it is automatically converted to PWM control when heavy load occurs. At present, DC power converters are widely used in mobile phones, MP3, digital cameras, portable media players and other products. In the classification of circuit types, it belongs to chopper circuit.
DC represents a DC power supply, such as a dry battery or a car battery. The 220V power supply for home use is AC power (AC). If a converter can convert a DC voltage (3.0V) into another DC voltage (1.5V or 5.0V), this converter can be called a DC power converter, or a switching power supply or a switching regulator.
DC power converters are generally composed of control chips, inductance coils, diodes, transistors and capacitors. When discussing the performance of DC power converter, it is impossible to judge its merits and demerits if only for the control chip. The component characteristics of the peripheral circuit and the wiring method of the substrate can change the performance of the power supply circuit. Therefore, comprehensive judgment should be made.
(1)PFM (Pulse Frequency Modulation)
The switching pulse width is constant, and the output voltage is stabilized by changing the frequency of the pulse output.
(2)PWM (Pulse Width Modulation)
The frequency of the switching pulse is constant, and the output voltage is stabilized by changing the pulse output width.
The DC circuit design should consider at least the following conditions:
(1)The range of the external input supply voltage and the magnitude of the output current.
(2)DC output voltage, current and the maximum power of the system.
Based on the above two points, the selection of PWM IC should consider:
(1)The maximum input voltage of the PWM IC.
(2)The frequency of the PWM switch. The choice of this is related to the efficiency of the system. The selection of capacitance and inductance also has some influence.
(3)The maximum rated current and rated power that the MOS transistor can withstand. If the DC-DC IC has its own MOS, only the rated current of the IC output needs to be considered.
(4)MOS switching voltage.
Schottky diodes are usually used. The reverse voltage and forward current should be considered when selecting. Generally, the reverse voltage is twice the input voltage and the forward current is twice the output current.
The choice of capacitor is based on the frequency of the switch, the requirements of the system ripple and the requirements of the output voltage. The capacity and the equivalent resistance inside the capacitor determine the ripple size and are also related to inductance as well.
The DC power converter is widely used, it can be installed in any place with electricity to protect personal property and save energy.