Push-pull converter is a voltage converter using a pulse transformer . The transformation ratio of the transformer can be arbitrary. Despite the fact that it is fixed, in many cases the pulse width can vary, which extends the available voltage stabilization range. The advantage of push-pull converters is their simplicity and the ability to increase power .
The single-phase push-pull converter is a push-pull full-bridge generator with a transformer and a rectifier with a filter .
Content
- 1 Principle of operation
- 2 Advantages and disadvantages
- 3 Transistors
- 4 Phasing
- 5 See also
- 6 References
Principle of Operation
The term “push-pull” is sometimes used to describe any transducer with bi-directional excitation of a transformer. For example, in a full-bridge converter, the keys connected to the H-bridge change the polarity of the voltage supplied to the primary winding of the transformer. At the same time, the transformer works as if it is connected to an AC source and produces voltage on the secondary winding. However, most often they mean a half-bridge converter loaded on the primary winding with a tap from the middle.
In any case, the secondary voltage is then rectified and transmitted to the load. At the output of the power source, a capacitor is often turned on, filtering out noise that inevitably arises due to the operation of the source in pulsed mode.
In practice, it is necessary to leave a small free interval between half-periods. The keys are usually a pair of transistors (or similar elements), and if both transistors open at the same time, there is a risk of a short circuit in the power source. Therefore, a slight delay is needed to avoid this problem.
Advantages and disadvantages
Transistors
N-type and p-type transistors can be used. Insulated gate field effect transistors are often used due to their ability to switch high currents, as well as low open channel resistance. Gates or bases of power transistors are pulled through a resistor to one of the voltages of the power source. To supply positive voltage to the gate of the N-type power transistor, an additional P-type transistor is used in the circuit with a common source, and an additional N-type transistor is used to connect the gate potential of the P-type power transistor to the ground potential.
Power transistors can be n-type (3 times more profitable than p-type).
Phasing
A very important point is the synchronization of the opening and closing of transistors. If both transistors are open, a short circuit occurs, if both are closed, high-voltage pulses appear due to EMF self-induction .
If the driver of power transistors is powerful enough and fast enough, the self-induction EMF does not have time to charge the stray capacitance of the transformer windings and transistors to high voltages.
See also
- Inverter (electrical)
- Push-pull output
- Rectifier
- H bridge