Hello folks,
As we were discussing about the Basic Building Blocks of Advanced DC-DC Converters, today we will discuss about SEPIC converter and analyze it.
SEPIC Converters:
The 2nd Basic Building Blocks is Sepic Converter. Both Cúk and buck-boost converter operation cause large amounts of electrical stress on the components, this can result in device failure or overheating. SEPIC converters solve both of these problems.
The SEPIC officially stands for “Single-Ended Primary Inductance Converter. Thus the SEPIC is also basically a BOOST-BUCK converter akin to the CUK converter. (The Boost stage comes first followed by the Buck stage and it is also I-V-I converter). Its output voltage is having same polarity as that of input voltage.
It has become popular in recent years in battery-powered systems as most battery operated circuits require dc-dc conversion to maintain full operation. In most circumstances that require stepping up and down the input voltage, SEPIC converters are worth the price of the extra inductor and capacitor for the efficiency and stable operation they provide.
As we were discussing about the Basic Building Blocks of Advanced DC-DC Converters, today we will discuss about SEPIC converter and analyze it.
SEPIC Converters:
The 2nd Basic Building Blocks is Sepic Converter. Both Cúk and buck-boost converter operation cause large amounts of electrical stress on the components, this can result in device failure or overheating. SEPIC converters solve both of these problems.
The SEPIC officially stands for “Single-Ended Primary Inductance Converter. Thus the SEPIC is also basically a BOOST-BUCK converter akin to the CUK converter. (The Boost stage comes first followed by the Buck stage and it is also I-V-I converter). Its output voltage is having same polarity as that of input voltage.
It has become popular in recent years in battery-powered systems as most battery operated circuits require dc-dc conversion to maintain full operation. In most circumstances that require stepping up and down the input voltage, SEPIC converters are worth the price of the extra inductor and capacitor for the efficiency and stable operation they provide.
Fig 1 : Basic Sepic Converter
Fig 2: Sepic Converter SW ON- OFF circuit diagram
One benefit of the SEPIC converter is that the input ripple current in the input capacitor is continuous. This reduces the amount of input capacitance necessary for low-ripple voltage, which reduces EMI (Electro Magnetic Interference). SEPIC converter maintains a fixed output voltage regardless of whether the input voltage is above, equal or below the output voltage.
Operation of converter into two modes: (Shown in fig)
Mode-1:- When the pulse is high/the switch is on, inductor L1 is charged by the input voltage Vin and inductor L2 is charged by capacitor C1. The diode D is off and the output is maintained by capacitor C. The fact that both L1 and L2 are disconnected from the load when the switch is on leads to complex control characteristics.
L1 charges, C1 discharges, L2 charges, C discharges
Mode-2:- When the pulse is low/the switch is off, the inductors outputs through the diode to the load and the capacitors are charged. When the power switch is turned off, the first inductor L1 charges the capacitor C1 and also provides current to the load, as shown in Fig. The second inductor L2 is also connected to the load during this time.
L1 discharges, C1 charges, L2 discharges, C charges
Thus, the converter is in “buck” mode for D < 0.5, and in “boost” mode for D > 0.5. SEPIC converters make it possible to efficiently convert a DC voltage to either a lower or higher voltage.
Thank you for your time. Let me know your area of interest on which we can have a two-way communication.
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