Power circuit for transferring energy by alternately switching winding circuits of a transformer at high speed

• US 5,886,880 A
• Filed: 05/28/1998
• Issued: 03/23/1999
• Est. Priority Date: 05/28/1997
• Status: Expired due to Term

• Current Assignee: NEC Platforms, Ltd. (NEC Corporation)
• Original Assignee: NEC Corporation
• Inventors: Hisanaga, Koji
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US09/084,909
• Time in Patent Office: 299 Days
• Field of Search: 363/16, 363/20, 363/21, 363/34, 363/50, 307/46, 307/48, 307/51, 307/64, 307/66
• US Class Current: 363/20
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer

Abstract

In a power supply unit, AC energy is converted to DC energy and stored into a first capacitor to which a first winding of a transformer is connected. An anti-parallel circuit of a first transistor and a diode is connected between the first capacitor and the first winding. An anti-parallel circuit of a second transistor and a diode is connected between a second winding of the transformer and a second, battery-charging capacitor. A current is induced in a third winding of the transformer for charging a third capacitor when a current is produced in the first winding in a particular direction or when energy stored in the second winding is released into the third winding. The first and second transistors are alternately switched on so that energy is transferred from the first capacitor to the second and third capacitors when the AC energy is normal and energy is transferred from the battery to the third capacitor when the AC energy fails.

Claims

1. A power supply unit comprising:

a rectifier for converting alternating-current energy to direct-current energy;

a transformer having a first winding wound in a first direction, a second winding wound in a second direction opposite to the first direction, and a third winding wound in the first direction;

a first loop circuit comprising said first winding, a first capacitor and an anti-parallel circuit of a first switching transistor and a first diode, said first capacitor being connected across said rectifier;

a second loop circuit comprising said second winding, a second capacitor and an anti-parallel circuit of a second switching transistor and a second diode, said second capacitor being connected to a battery;

a power delivery circuit connected to said third winding for receiving a current induced in the third winding when a current is produced in the first winding in a particular direction or when energy stored in the second winding is released into the third winding, and charging a third capacitor with the received current; and

a pulse generating circuit for alternately driving said first and second switching transistors so that energy is transferred from the first capacitor to the second and third capacitors when the first capacitor is charged by the rectifier and energy is transferred from the battery to the third capacitor when the first capacitor is not charged by the rectifier.

2. A power supply unit as claimed in claim 1, wherein said power delivery circuit comprises:

a third diode connected to a terminal of said third winding so that the third diode is forward-biased when the first transistor is switched on to produce a current;

an inductor connected to the third diode for allowing said current to flow into the third capacitor; and

a fourth diode connected between said third diode and an opposite terminal of the third winding, said third capacitor being connected between the inductor and an opposite terminal of said third winding, whereby the fourth diode causes said inductor to continue to flow said current into the third capacitor when said second transistor is switched on.

3. A power supply unit as claimed in claim 2, wherein the arrangement is such that,

when the first switching transistor is switched on, a current is produced in the first winding, energy is stored therein and said third diode is forward-biased to induce a current in the third winding in response to the current in the first winding;

when the first switching transistor is switched off, said third diode is reverse-biased and said second diode is forward-biased to release the energy stored in the first winding into the second winding,

when the second switching transistor is switched on during the time the first capacitor is not charged by the rectifier, a current is withdrawn from the battery into the second winding, and said first and third diodes are reverse-biased to store energy in the second winding, and

when the second switching transistor is switched off, said third diode is forward-biased to release the energy stored in the second winding into the third winding.

4. An energy transfer method using a transformer having first, second and third windings, and first, second and third capacitors respectively associated with the first, second third windings, comprising the steps of:

a) converting alternating-current energy to direct-current energy;

b) charging the first capacitor with said direct-current energy;

c) discharging the first capacitor through the first winding, inducing a current in the third winding to charge the third capacitor and storing energy in the first winding;

d) releasing the stored energy of the first winding into the second winding and charging the second capacitor with the released energy;

e) repeating steps (c) and (d) until the energy released by the first winding becomes insufficient to charge said second capacitor;

f) discharging the second capacitor through the secondary winding and storing energy on the second winding;

g) releasing the stored energy of the second winding into the third winding and charging the third capacitor;

h) repeating steps (f) and (g) until energy stored in the first capacitor becomes sufficient to cause the first winding to release sufficient energy into the second winding to charge said second capacitor; and

i) repeating steps (c) to (h).

5. In a power supply unit comprising:

a rectifier for converting alternating-current energy to direct-current energy;

a transformer having a first winding wound in a first direction, a second winding wound in a second direction opposite to the first direction, and a third winding wound in the first direction;

first, second and third diodes connected to said first, second and third windings, respectively; and

first, second and third capacitors connected to said first, second and third diodes, respectively, said first capacitor being charged with the direct-current energy, a method comprising the steps of;

a) producing a current from the first capacitor to the first winding, forward-biasing the third diode to induce a current in the third winding to charge the third capacitor and reverse-biasing the second diode;

b) forward-biasing the second diode to release energy stored in the first winding into the second winding to charge the second capacitor;

c) repeating steps (a) and (b) until the energy released in the second winding becomes insufficient to charge the second capacitor;

d) producing a current from the second capacitor to the second winding and reverse-biasing the first and third diodes to store energy in the second winding;

f) forward-biasing the third diode to release the stored energy of the second winding into the third winding to charge the third capacitor; and

g) repeating steps (d) and (f) until energy stored in the first capacitor becomes sufficient to cause the first winding to release sufficient energy into the second winding to charge said second capacitor.