Split-pi topology

Split- P converter (English split -PI) is known in electronics, an electronic circuit that can convert an electrical DC voltage into another DC electric voltage. The height of the output voltage of the DC-DC converter may be either larger or smaller than the original input voltage. The output voltage always has the same sign as the input voltage, so the split -Pi- converter included in the group of the non-inverting DC-DC converter.

A key feature of Split -Pi converter is bi-directional energy flow direction. The topology of the Split - P converter allows both power flow from the defined input to the output and vice versa. It does not matter which side of the converter as input and which is defined as the output. Furthermore, while it does not matter what height the voltages of energy sources.

Naming and construction

The name of the Split -Pi converter is similar to the circuit of a pi filter, which used in the circuit of the converter in duplicate, using semiconductor switches divided (English split mode). The name thus reflects, in principle resist the circuitry expansion of the DC-DC converter.

Split - P converter can be seen in fact as a chain connection of two synchronous converter, wherein the first synchronous converter vice versa - is used and the DC voltage of the converter is supported by means of an additional capacitor - that is mirrored. The transducer thus consists of two inductors that are using four bi-directional semiconductor switches cyclically charged and discharged as the active energy store with energy. The two outer capacitors are used - as with any DC-DC converter - as a buffer capacitors and smooth the respective voltage. As an inductor is provided in the input line and output line, both the input current and the output current is continuous.

Strictly speaking, the split -Pi- converter is not a separate DC-DC converter topology, but rather a combination of conventional DC-DC converter.

Function

In general, the split -Pi- converter is operated so that only one synchronous converter operates. The other of the synchronous converter is in this case coupled to the voltage translator is 1 - in other words it is the upper switch is closed.

Which of the two synchronous converter will now be clocked and which bridges depend on the desired output voltage.

Operation with unidirectional power flow direction

Since the split Pi converter is symmetrical and the direction of energy flow bidirectionally, it does not matter which port as and which is defined as the output input.

If now at a terminal UA a voltage source and the other port UB a load, the voltage at the load by the choice of active and passive synchronous converter can be controlled as desired.

If the voltage at the load to be less than the voltage of the voltage source, it is of the synchronous converter A is operated with a voltage ratio of 1 (upper switch is closed ) and the synchronous clocked converter B having the desired pulse-width ratio. The entire split Pi transducer thus operates as a synchronous buck converter whose output voltage depends on the pulse-width ratio of the synchronous converter B.

If the tension load to be larger than the voltage of the voltage source, it is synchronous converter B operates with a power ratio of 1 (the top switch is closed ) and the synchronous converter A clocked with the desired pulse-width ratio. Split - P converter thus operates as a synchronous boost converter whose output voltage is now dependent on the pulse-width ratio of the synchronous converter A.

Operation with bidirectional energy flow direction

To be connected to each terminal of the Split -Pi- converter, a voltage source, it can - as in the simple synchronous converter also - the current flow direction are determined by the choice of the pulse width ratio. In contrast to simple synchronous converters, it is irrelevant in this converter, which has the height of each voltage source. Depending on the amount of the respective voltages of the voltage sources of both passive and active synchronous converter of Split -Pi converter is specified.

If the voltage of the voltage source to UA higher than the power source voltage at UB, it must synchronous converter A is passive (upper switch is closed ) and the desired direction of energy flow and its height is determined by the pulse width ratio of synchronous converter B, which is actively working.

If the voltage of the voltage source to UA less than that voltage of the voltage source UB, the synchronous converter must work the other way around.

Function of the DC link capacitor

Regardless of the operating mode of the converter is always a synchronous converter inactive. Thus, an inductor is always present either in the input circuit or output circuit that is not used directly for the converter operation. Then switched from the active synchronous converter, the upper and the lower switch from one, it would remain open without a DC link capacitor, a connection of the inductance of the passive synchronous converter. Since, in the previously gone hi- phase of the active synchronous converter injected current but must continue to flow in the inductor of the passive synchronous converter, would be induced without a capacitor on this now open port due to the lenz 's rule a very high voltage, which would destroy the semiconductor switches.

Through this link capacitor of the inductor of the passive synchronous converter is offered a freewheeling current path. The DC link capacitor thus acts as a freewheeling capacitor and represents a kind of voltage source in the time-out (Lo phase) of the active synchronous converter for passive synchronous converter dar.

Application and Benefits

The advantage of this DC-DC converter is both the possible bidirectional energy flow direction and independence of voltage limits. The transducer is optimally suited for akkumulatorbetriebene electric drives, since the induced voltage of the electric motor are also both smaller and larger can than the battery voltage. In addition, is possible by the bi-directional power flow direction of the braking operation of the electric motor.