Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
2000-08-11
2001-08-14
Nguyen, Matthew (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C323S282000
Reexamination Certificate
active
06275014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a switching regulator circuit (hereinafter referred to as SW regulator circuit) constructed of a simple circuit and operable in a high efficiency. More specifically, the present invention is directed to such a switching regulator circuit capable of eliminating a recharging operation of a power supply by a reverse current flowing through a coil.
2. Description of the Related Art
FIG. 8
shows a circuit diagram of a switching regulator circuit typically known as a conventional step-up type SW (switching) regulator circuit. In this step-up type SW regulator circuit, a power supply
10
is connected to one end of a coil
11
, whereas both a switch element (hereinafter referred to as SW element)
13
and a diode
12
are connected to the other end of this coil
11
. The other end of the diode
12
constitutes an output terminal of the SW regulator circuit. To this output terminal, both a capacitor
14
and a load
15
are connected, while an SW regulator control circuit
20
controls ON time and OFF time of the SW element
13
in order that the output voltage of the output terminal becomes a certain constant voltage “Vout”. In the SW regulator circuit of
FIG. 8
, since a current flows through the diode
12
, a loss occurs. To reduce this loss, as shown in
FIG. 9
, such a synchronous rectifying type SW regulator is conducted in which another SW element
16
is additionally connected parallel to the diode
12
, and both the SW element
13
and the SW element
16
are operated in a complementary mode as represented in FIG.
10
. As a result, generally speaking, a converting efficiency of a synchronous rectifying type SW regulator can be increased by approximately 5%.
In this synchronous rectifying type SW regulator, the current of the coil
11
flows via the SW element
16
along the reverse direction in the current mode other than the current continuous mode (namely, in current discontinuous mode where coil current is reduced to 0), so that this reverse coil current charges the power supply
10
which may cause a problem. This SW element
16
is connected parallel to the diode
12
.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problem, and therefore, has an object to provide such a switching regulator circuit, according to the present invention, featured by that while a switch element is additionally provided between a coil and a power supply and also a capacitor having a large capacitance is additionally employed between the coil and the ground, this switch element is turned ON/OFF. As a result, recharging operation of the power supply by the reverse current flowing through the coil is interrupted, whereas the reverse current may charge the capacitor having the large capacitance.
More specifically, the switching regulator circuit is featured by such a synchronous rectifying type switching regulator circuit, according to a first aspect of the present invention, for alternately turning ON/OFF a first switch element for controlling a current of a coil employed in the switching regulator and a second switch element connected parallel to a commutation diode, in which: a capacitor is added to an input of the switching regulator circuit; a third switch element is interposed between a power supply such as a battery and the capacitor; and when the first switch element is turned ON, the third switch element is turned ON, whereas when the first switch element is turned OFF, the third switch element is turned OFF.
Furthermore, the switching regulator circuit is featured by such a synchronous rectifying type switching regulator circuit, according to an second aspect of the present invention, having means for detecting the current of the coil, for alternately turning ON/OFF a first switch element for controlling the current of the coil employed in the switching regulator and a second switch element connected parallel to a commutation diode, in which: a capacitor is added to an input of the switching regulator circuit; a third switch element is interposed between a power supply such as a battery and the capacitor; and when the current of the coil is decreased lower than, or equal to a preselected current value, the third switch element is turned OFF, whereas when the current of the coil is increased higher than, or equal to the preselected current value, the third switch element is continuously turned ON.
With employment of such a circuit arrangement, the switching regulator circuit operable in the high efficiency can be realized, while the power supply is not charged by the coil reverse current.
REFERENCES:
patent: 5721483 (1998-02-01), Kolluri et al.
patent: 5940287 (1999-08-01), Brkovic
patent: 6091232 (2000-07-01), Criscione et al.
patent: 6151233 (2000-11-01), Kondo
Adams & Wilks
Nguyen Matthew
Seiko Instruments Inc.
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