Switching circuit for master-slave feeding mode of low voltage power supply

• US 20050127882A1
• Filed: 12/03/2004
• Published: 06/16/2005
• Est. Priority Date: 12/11/2003
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Zhang, Lan, Cheng, HongBing, Pan, JunKui, Qian, YuJian
• Granted Patent: US 7,332,833 B2
• Time in Patent Office: Days
• US Class Current: 323/268
• CPC Class Codes: H02J 1/108 using diodes blocking reverse current flow H02J1/12 takes precedence
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems

Abstract

The present invention provides a switching circuit for the master-slave feeding mode of the low voltage power supply. The switching circuit utilizes the active switches as the switching devices, so that it can increase the switching speed, decrease the voltage drop and loss, being suitable to the low voltage circuits, and can judge or determine the master power supply and the back-up power supply, realizing the switching between the master and slave power supplies without interruption. The switching circuit of the invention improves the reliability of the system and has the simple structure and easy operation.

Claims

1. A switching circuit for a master-slave feeding mode of the low voltage power supply, wherein said switching circuit comprising:

A master power supply input terminal, a secondary power supply input terminal, an output terminal;

A master switch between master input terminal and output terminal, a secondary switch between slave power supply input terminal and output terminal;

A sampling device for sampling signals from said master input terminal and slave input terminal;

A control device for judging and controlling “

on”

or “

off”

states of said master and slave switches according to output of said sampling device, wherein when power supply input at the master power supply input terminal is normal, said control device controls the master switch to be “

on”

, the secondary switch to be “

off”

;

otherwise said control device controls the master switch to be “

off”

, the secondary switch to be “

on”

.

2. The switching circuit according to claim 1, wherein said sampling device comprises two resistances (R340 and R342) in series and a capacitor (C12), wherein one terminal of said two resistances (R340 and R342) in series is grounded and the other terminal is connected to said master power supply input terminal, and said capacitor (C12) is parallel with the resistance positioned on the grounded side, a voltage between two resistances (R340 and R342) is the output of said sampling device.

3. The switching circuit according to claim 1, wherein said switching circuit further comprises a power-supply-introduced and isolating circuit for providing an operating voltage to said judging and controlling device and isolating said master power supply from said secondary power supply, said power-supply-produced and isolating circuit is constituted by two diodes (V8, V13) in series in contrary direction, one terminal of which is connected to said master power supply input terminal and the other terminal is connected to said secondary power supply input terminal, and a common connecting point of these two diodes (V8, V13) is a common power supply terminal of said judging and controlling device.

4. The switching circuit according to claim 3, wherein said judging and controlling device comprises a dual-comparer constituted by two comparers (N3A, N3B), and two reference voltage circuits;

A of reference voltage circuits for setting a reference voltage for one comparer (N3A) comprises two resistances (R341, R343) in series and a capacitor (C11), said two series resistances (R341, R343) being parallel with the capacitor (C11), one terminal of which is grounded and the other terminal is connected to said common power supply terminal;

The other reference voltage circuit for setting a reference voltage for the other comparer (N3B) comprises two resistances (R346, R347) in series, one terminal of which is grounded and the other terminal is connected to said common power supply terminal;

One of input terminals of said one comparer (N3A) is connected to the output terminal of said sampling device, the other input terminal is connected to a common connecting point of the two series resistances (R341, R343) of the one reference voltage circuit, and an output terminal of the one comparer (N3A) is connected to one of input terminals of the other comparer (N3B) and the controlling terminal of master switch respectively;

the other input terminal of said the other comparer (N3B) is connected to a common connecting point of two series resistances (R346, R347) of the other reference voltage circuit, an output terminal of the other comparer (N3B) is connected to the controlling terminal of said secondary switch.

5. The switching circuit according to claim 4, wherein said judging and controlling device further comprises two up-pulling resistances (R348, R349 ) provided between the output terminals of said dual-comparer (N3A, N3B) and said common power supply terminal respectively.

6. The switching circuit according to claim 4, wherein said judging and controlling device further comprises two series resistances (R344, R345) provided between the reference voltage input terminal and the output terminal of said comparer (N3A), being used to set a feedback of said comparer (N3A).

7. The switching circuit according to claim 1, wherein said switching circuit further comprises two diodes which are parallel with the master switch and the secondary switch respectively and used to maintain a rear stage voltage during the switching of the master switch and the secondary switch.

8. The switching circuit according to claim 1, wherein said switching circuit further comprises a fictitious load constituted by two parallel resistances, one terminal of which is grounded and the other terminal is connected to the master power supply input terminal, being used to discharge the capacitor at the master power supply input terminal to stabilize the operating voltage of the switching circuit.

9. The switching circuit according to claim 1, wherein said master switch and said secondary switch are constituted by MOSEFT transistors.