| US 7,602,158 B1 | ||
| Power circuit for generating non-isolated low voltage power in a standby condition | ||
| Alin Theodor Iacob, Sunnyvale, Calif. (US) | ||
| Assigned to National Semiconductor Corporation, Santa Clara, Calif. (US) | ||
| Filed on Mar. 21, 2005, as Appl. No. 11/86,215. | ||
| Int. Cl. H02M 7/06 (2006.01) | ||
| U.S. Cl. 323—231 [363/126; 307/17] | 15 Claims |
| 1. A power circuit generating a non-isolating low voltage power supply in standby, comprising:
an AC connector generating a first AC input and a second AC input, wherein said second AC input is opposite in phase from
said first AC input;
a first diode bridge rectifier circuit coupled at separate nodes to said first AC input, said second AC input, and a ground,
wherein said first diode bridge rectifier at a first output node provides a high voltage power signal to a first load;
a second diode bridge rectifier circuit coupled at separate nodes to said first AC input, said second AC input, and said ground,
said second diode bridge rectifier circuit comprising a first diode, a second diode, a third diode and a fourth diode, wherein
said second diode bridge rectifier at a second output node provides a low voltage power signal to a second load, said second
output node between the cathode of said first diode and the cathode of said second diode;
a first capacitor coupled in series with said first AC input and a first node of said second diode bridge rectifier circuit
for dropping a first voltage of said first AC input, said first node between the anode of said first diode and the cathode
of said fourth diode, wherein said first capacitor is connected directly to said first node;
a second capacitor coupled in series with said second AC input and a second node of said second diode bridge rectifier circuit
for dropping a second voltage of said second AC input, said second node between the anode of said second diode and the cathode
of said third diode, wherein said second capacitor is connected directly to said second node;
a zener diode coupled to said second output node, wherein the anode of said zener diode is connected directly to ground and
wherein the cathode of said zener diode is connected directly to said second output node between said first and second diodes;
and
a switching shunt regulator circuit coupled in parallel with said zener diode and to said second output node, to ground and
to said second load and comprising a first switch, said switching shunt regulator circuit connected directly to said second
output node and operable for controlling the voltage of said low voltage power signal to said second load, wherein said switching
shunt regulator circuit shorts the output at said second output node to ground when engaged, thereby also shorting the output
across said first and second capacitors.
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