Current limited buck power supply

Details Current limited buck power supply Current limited buck power supply

2001-08-24

2003-11-18

Sterrett, Jeffrey (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

Reexamination Certificate

active

06650098

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to power supplies and more particularly relates to a novel control power supply for circuits containing high side switches.
BACKGROUND OF THE INVENTION
Most power electronic equipment requires a control power supply that supplies power (5-20 w) for the control and drive circuits of the device. Typically, a flyback or a buck converter is used to provide the control power.
Referring to
FIG. 1
, a circuit diagram of a conventional flyback converter
2
is shown. In a typical application, flyback converter
2
is provided with a 300V input connected across a relatively large transformer
4
. An extra clamp circuit
16
is required, such as would be provided by the arrangement of diode
6
, resistor
8
and capacitor
10
. A FET
12
is controlled by controller
14
. The FET requires a breakdown voltage much greater than 300 V, typically from 450-660 V.
Another conventional solution, a buck power supply, is illustrated in the circuit diagram of FIG.
2
. In the buck power supply of circuit
20
, regulation takes place at the ground level. A level shifting driver
22
is used to drive the gate of the high side switch
24
. In a 300 V application, FET
24
typically can have a voltage rating of 400 V.
The conventional circuits have various disadvantages. Flyback converters require transformers having a number of terminals, adding to size and cost. In addition, the converters have losses due to current flow through higher voltages, and thus require higher R
DSON
MOSFET switches. Conventional buck power supply topologies require a high voltage integrated circuit (HVIC).
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of the prior art by providing a novel topology which uses a standard power supply controller to control a high side switch in an electronic circuit. In the power supply of the present invention, the feedback voltage referenced to a ground (or negative bus level) is level-shifted to a high side controller by means of a diode/capacitor/resistor network. In addition, power to a high side controller is supplied by using the feedback output voltage.


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