34063 circuit for DC-DC power conversion

34063 is an integrated circuit used for DC-DC power conversion. It is widely used, universal, cheap and easy to buy. It can be used for voltage step-up, step-down and polarity reversal. 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 working frequency filter capacitor, etc. In addition, when the output power cannot 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 tube . The nominal meaning of peripheral components and the calculation formula of 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 (inductor): 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: the minimum value when the input voltage is unstable Vf=1.2V Fast switching diode forward voltage drop Other manual parameters: Parameter name Symbol unit MC34063 CW34063 IRM03A Input voltage Vin V 2.5～40V 2.5～40V 2.5～40V Output voltage Vout V 1.25～40V 1.25～40V 1.25～40V Maximum output current Iomax A 1.5A 1.5A 1.8A Maximum operating frequency f kHz 0.1～100 KHZ 0.1～ 100KHZ 0.1~100KHZ Power PW 1.25W 1.25W 0.9W Working temperature Ta 0~70 degrees 0~70 degrees 0~70 degrees Notes in practical applications: 1: IN4148 can be used as a fast switching diode in situations where high efficiency is required. IN5819 must be used! 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.