Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-07-03
2004-03-16
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S285000, C363S021040, C363S021110, C363S097000
Reexamination Certificate
active
06707283
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to electronic circuits and, more particularly, to switching power supplies which converts an AC signal to a regulated DC signal.
Most switching power supplies have a transformer with a power switching transistor coupled to one side of the transformers primary winding. The power transistor turns on and off as determined by a regulator circuit to alternately store energy in the magnetic field of the transformer and transfer the stored energy to the secondary winding. The secondary winding of the transformer develops a DC output voltage across a shunt capacitor coupled across the secondary winding as a function of the energy transfer.
For example,
FIG. 1
illustrates prior art switching power supply
10
that receives an AC line voltage and converts it to a DC bulk voltage by the full-wave rectifier diode bridge
12
. Capacitor
14
filters the DC bulk voltage, and the primary winding of transformer
16
receives the DC bulk voltage. Regulator
18
modulates an inductor current through the primary winding of transformer
16
to control the amount of energy stored in the magnetic field of transformer
16
. The energy stored in the magnetic field is transferred to the secondary winding where capacitor
20
is coupled across the secondary winding to develop the DC output voltage (V
OUT
). Diode
22
and photo-detection transistor
24
act together to optically couple feedback information from reference and error amplifier
26
to regulator circuit
18
to regulate V
OUT
of switching power supply
10
.
Secondary side sensing of the voltage and current at the output to the switching power supply in the prior art requires at a minimum, a voltage reference, additional op amps, an opto-coupler, as well as a secondary supply voltage which operates at current limit. When at current limit, the output voltage typically is reduced which results in a reduction of the output voltage to operate the constant current circuitry. Thus, it is desired to have a switching power supply circuit that works entirely from the primary side of the transformer to eliminate the need for additional components. Also, a need exist as well to eliminate the secondary side supply required to operate a switching power supply while in current limit. Furthermore, a need exists to have a switching power supply circuit that operates in a constant current mode, and a constant voltage mode at the output to the switching power supply. The invention disclosed herein will address the above problems.
REFERENCES:
patent: 5305192 (1994-04-01), Bonte et al.
patent: 5349284 (1994-09-01), Whittle
patent: 5619405 (1997-04-01), Kammiller et al.
patent: 6333624 (2001-12-01), Ball et al.
Semiconductor Components Industries L.L.C.
Sterrett Jeffrey
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