Booster type switching regulator

Details Booster type switching regulator Booster type switching regulator

2002-09-17

2004-12-28

Berhane, Adolf (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

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

Reexamination Certificate

active

06836102

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a booster type switching regulator (herein after referred to as a booster type SW regulator) in which an inrush current for charging an output capacitor from the power supply through a coil can be suppressed when a power supply is turned on.
2. Description of the Related Art
A conventional booster type SW regulator has a structure such as that of the circuit shown in FIG.
6
.
An input power supply
20
of
FIG. 6
is connected to a coil
21
and a power supply terminal
1
of a booster type SW regulator control circuit
30
, the other end of the coil
21
is connected to a drain of a switch (“SW”) element
22
and an anode of a commutation diode
23
, a cathode of the diode
23
is connected to an output voltage terminal
2
of the booster type SW regulator control circuit
30
, and a capacitor
24
and a load
25
are connected to the output voltage terminal
2
. When the voltage of the output voltage terminal
2
is denoted by Vout, the booster type SW regulator control circuit
30
controls the ON/OFF state of the SW element
22
so that Vout becomes constant. A gate of the SW element
22
is connected to a terminal
3
of a driving circuit
31
for the SW element, and is driven by a voltage Vext of the terminal
3
to turn ON/OFF the SW element
22
. In
FIG. 6
, the SW element is an N-ch MOS transistor, and in order to turn ON the SW element, the voltage Vext of the output terminal
3
of the driving circuit
31
becomes a positive voltage “H”, and in order to turn OFF the SW element
2
, a GND level voltage is outputted as the voltage Vext. Both a source of the SW element
22
and a substrate are connected to the GND level.
A switch circuit (hereinafter referred to as a SW circuit)
10
is for connecting the power supply
20
and the booster type SW regulator circuit, and when the booster type SW regulator circuit is in an OFF state, the SW circuit
10
is opened (hereinafter, a state where the SW circuit
10
is opened will be referred to as a state where the SW circuit
10
is in an OFF state). When the booster type SW regulator circuit is turned ON, the SW circuit
10
is closed (hereinafter, a state where the SW circuit
10
is closed will be referred to as a state where the SW circuit
10
is in an ON state).
In general, a mechanical circuit is used for the SW circuit
10
.
When the SW circuit
10
is turned ON, the output capacitance
24
is charged up to the voltage of the power supply
20
from the power supply
20
through the SW circuit
10
, the coil
21
, and the diode
23
, and a large inrush current flows by this. This is shown in
FIGS. 7A and 7B
.
In
FIGS. 7A and 7B
, the horizontal axis indicates time,
FIG. 7A
shows a current Ip of the power supply
20
, and
FIG. 7B
shows a voltage Vout of the output capacitance
24
. At a time T
1
, the SW circuit
10
is turned ON, and at a time T
2
, the output capacitance
24
is charged to the voltage of the power supply
20
, and the current of the power supply
20
becomes small. Thereafter, a boosting operation is gradually performed by a soft start circuit.
However, in the conventional booster type SW regulator, there is a problem that when the power supply is turned ON from the OFF state (when the SW circuit
10
is turned ON from the OFF state), a large inrush current flows.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the problem described in the related art, and therefore it is an object of the present invention to suppress an inrush current at the time when a power supply of a booster type SW regulator is turned ON.
In order to solve the above-mentioned problem, according to this invention, a MOS transistor is provided between a coil of a booster type SW regulator and a power supply, and when the power supply is turned ON, a resistance value of the MOS transistor is changed from a high state to a low state, so that an inrush current at the time when the power supply is turned ON is suppressed.


REFERENCES:
patent: 4631470 (1986-12-01), Bingley
patent: 5187653 (1993-02-01), Lorenz
patent: 5374887 (1994-12-01), Drobnik
patent: 5420780 (1995-05-01), Bernstein et al.
patent: 6542344 (2003-04-01), Mashiko

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