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Single-ended shunt charger

Single-ended shunt charger
The chargers mentioned in the preceding positive connection power supply are all self-excited. The charger is both an oscillating tube and a switch, and these two functions are bound to contain each other. In order to maintain the oscillation and the ideal switching effect, the instability of the positive feedback quantity is an important factor limiting the performance of the self-excited charger. As an oscillating circuit, the power charger increases the pulse width modulator's control current, which is one of the reasons for limiting the maximum output power of the self-excited charger. Therefore, the charger over 200W seldom adopts self-excited mode.
The so-called other-excitation charger means that the charger itself and the pulse transformer are not part of the oscillator. The base switch pulse required by the charger conduction and cut-off is supplied by the external oscillator, and the pulse width modulation is carried out at the specially designed oscillation stage. Since the oscillating stage and pulse width modulation stage of the other type of voltage regulator are independent, the excitation state of the charger is independent of the input voltage, which not only works extremely stable, but also has a wider voltage range. In addition, he excitation charger loss is very small, the output power is large. When the charger is switched on, the voltage drop between its c-e electrodes is only saturation voltage drop, and the loss is very small. When the charger is cut off, all the power voltage is added to the c-e terminal, and the current is zero. Theoretically, there is no loss. There is another advantage is good waveform, such as the use of electrical appliances such as television interference minimal. However, it is more difficult for the self-excited charger to achieve complete non-interference.
, it can be seen that he excitation charger to have an independent oscillator, excitation level and pulse width modulator, power supply protection system, and so on, so the circuit is much more complex than the self-excitation, if the use of discrete components assembly is quite troublesome. Most other chargers now use an integrated <c driver="" that="" integrates="" error="" amplifiers,="" pulse="" width="" modulators,="" oscillators,="" and="" overvoltage="" overcurrent="" protection.<="" span=""></c>
Although some other drive control integrated circuits were developed in the early stage, they were rarely adopted due to the imperfect function design, low integration level and poor reliability. It wasn't until the end of the 20th century, when a series of fully functional drivers with extremely simple external circuits were developed, that they were widely adopted. At present, DVD and other household appliances with less than 30W power consumption also use the other-excitation charger, which not only has a much simpler circuit structure than the self-excitation charger, but also has a much better performance than the white-excitation charger.
All kinds of self-excited chargers mentioned above can form a single-end external chargers if their self-excited oscillation function is removed and independent drivers are added. The difference in the circuit only depends on the internal function and working mode of the drivers. Therefore, this section takes the single-terminal shunt driver as the main line and introduces the working principle, performance and characteristics of various single-terminal shunt chargers through examples.
| release time:2019.10.16    Source:
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