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What is a DC-DC circuit?

Any circuit that converts DC to DC can be a DC-DC circuit. The most common DC-DC circuits are switching conversion and linear conversion. In a narrow sense, a circuit that converts DC to DC through switching conversion is called a DC-DC circuit. Generally speaking, a DC-DC circuit must have a regulator tube, which works in a switching state or a linear amplification state, which determines its working mode. DC-DC power supplies are usually divided into two categories: linear regulated power supplies and switching regulated power supplies. Here is a DC-DC circuit online calculator and formula-related parameters.

DC-DC power supplies are usually divided into two categories: linear regulated power supplies and switching regulated power supplies. Of course, in addition to the above two types of power supplies, there is also a small power supply that uses a voltage regulator tube.

Switching power supply DC-DC converters can be divided into several types: step-down (Buck), step-up (Boost) and step-up-step-down (Boost-Buck).

Generally speaking, there are three most common modulation methods for switching power supplies DC-DC, namely pulse width modulation (PWM), pulse frequency modulation (PFM) and cycle-skipping modulation (PSM).

1: Polarity reversal

2: Voltage boost

3: Voltage drop

Automatic calculation of peripheral component parameters for three typical circuits

Directions：Just enter the parameters you want in the middle left box, and then click the "Calculate and Refresh Circuit Diagram" button, it will automatically give all relevant peripheral component parameters and corresponding standard circuit drawings, making the design of DC-DC circuits intelligent and efficient.

Regarding warnings：If the parameters you enter exceed the limit of 34063, it will automatically pop up a warning window to remind you to change them.

Special InputTo design a polarity reversal circuit, add a minus sign in front of the input or output voltage number, such as -5v.

This is an integrated circuit used for dc-dc power conversion. It is widely used, general, cheap and easy to buy. The polarity reversal efficiency is up to 65%, the boost efficiency is up to 90%, and the buck efficiency is up to 80%. The conversion efficiency is proportional to the operating frequency, filter capacitance, etc.

In addition, when the output power does not meet the requirements, such as >250~300ma, the current can be expanded by connecting an external power expansion tube. Either bipolar or MOS type current expansion tubes are acceptable. The calculation formula and other parameters and their meanings are detailed in the bottom part.

The meaning of the nominal values of peripheral components and the calculation formulas for their values：

Vout(Output voltage)＝1.25V（１＋R1／R2）

Ct(Timing capacitor): determines the internal operating frequency. Ct=0.000 004*Ton(operating frequency)

Ipk=2*Iomax*T/toff

Rsc(Current limiting resistor): determines the output current.Rsc＝0.33／Ipk

Lmin(inductance)：Lmin＝(Vimin－Vces)*Ton/ Ipk

Co(Filter capacitor): determines the output voltage ripple coefficient, Co = Io*ton/Vp-p (ripple coefficient)

Fixed value parameters：

Vces=1.0V　　ton/toff=(Vo+Vf－Vimin)/(Vimin－Vces）　　Vimin:Minimum value when input voltage is unstable

Vf=1.2V Fast switching diode forward voltage drop

Other manual parameters：

Note in practical application：

1：IN4148 can be used as a fast switching diode, and IN5819 must be used in situations where high efficiency is required

2：The voltage that 34063 can withstand, that is, the sum of the absolute values of the input and output voltages cannot exceed 40V, otherwise it cannot work safely and stably.