Hp Small Pin Laptop Adapter / Charger - 19.5V /

hp small pin  Laptop Charger 19.5V~3.33A  - Black

Originally, most AC/DC adapters were linear power supplies, containing a transformer to convert the mains electricity voltage to a lower voltage, a rectifier to convert it to pulsating DC, and a filter to smooth the pulsating waveform to DC, with residual ripple variations
small enough to leave the powered device unaffected. Size and weight of
the device was largely determined by the transformer, which in turn was
determined by the power output and mains frequency.
Ratings over a few watts made the devices too large and heavy to be
physically supported by a wall outlet. The output voltage of these
adapters varied with load; for equipment requiring a more stable
voltage, linear voltage regulator circuitry
was added. Losses in the transformer and the linear regulator were
considerable; efficiency was relatively low, and significant power
dissipated as heat even when not driving a load.

Early in the twenty-first century, switched-mode power supplies (SMPSs)
became almost ubiquitous for this purpose. Mains voltage is rectified
to a high direct voltage driving a switching circuit, which contains a
transformer operating at a high frequency and outputs direct current at
the desired voltage. The high-frequency ripple is more easily filtered
out than mains-frequency. The high frequency allows the transformer to
be small, which reduces its losses; and the switching regulator can be
much more efficient than a linear regulator. The result is a much more
efficient, smaller, and lighter device. Safety is ensured, as in the
older linear circuit, because a transformer still provides galvanic isolation.

A
linear circuit must be designed for a specific, narrow range of input
voltages (e.g., 220–240 VAC) and must use a transformer appropriate for
the frequency (usually 50 or 60 Hz), but a switched-mode supply can work
efficiently over a very wide range of voltages and frequencies; a
single 100–240 VAC unit will handle almost any mains supply in the
world.

However,
unless very carefully designed and using suitable components, switching
adapters are more likely to fail than the older type, due in part to
complex circuitry and the use of semiconductors. Unless designed well,
these adapters may be easily damaged by overloads, even transient ones, which can come from lightning