Constant frequency, zero-voltage-switching converters with resonant switching bridge

• US 5,594,635 A
• Filed: 03/30/1993
• Issued: 01/14/1997
• Est. Priority Date: 03/30/1993
• Status: Expired due to Term

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gegner, Joel P.
• Primary Examiner(s): Sterrett, Jeffrey L.
• Application Number:
  US08/040,302
• Time in Patent Office: 1,386 Days
• Field of Search: 363/17, 363/98, 363/132, 363/124
• US Class Current: 363/124
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A novel, compact, converter structure utilizes a switching bridge configuration to provide a low voltage stress, constant frequency controlled converter whose switches and diodes all turn-on and turn-off with zero-voltage-switching. The novel converter configuration uses a full-bridge switching circuit comprising four diodes D₁ -D₄ and, in one embodiment, four active semiconductor switches S₁ -S₄. A resonant inductor L_r is connected across the bridge nodes a and b, and parasitic capacitance of the diodes and active switches S₁ -S₄ are incorporated in an L-C circuit. Connected in parallel with the bridge is a voltage source or sink, depending on the direction that power will flow; and connected to node a or b is a current source or sink, again depending upon the direction of power flow. The present invention stores sufficient energy in the resonant inductor L_r so that prior to each switch or diode commutation, charge present on the corresponding parasitic capacitance of that semiconductor may be removed by the current drawing action of the resonant inductor L_r. In this way, all diodes D₁ -D₄ and active switches S₁ -S₄ operate with zero-voltage-switching. The novel bridge configuration directs the power flow from the source to the load, while passively guaranteeing voltage limitation across each diode and switch, and providing volts-seconds balance for the resonant inductor L_r.

Claims

1. A constant frequency controlled, zero-voltage switched, quasi-resonant converter for receiving power from a DC power source and providing power to a DC load, said converter comprising:

switching bridge means for connecting and disconnecting said power from said DC power source to and from said DC load, said switching bridge comprising;

(a) a resonant inductor having a first end operatively connected to a first node and a second end operatively connected to a second node;

(b) a first diode having an anode operatively connected to said first node and a cathode operatively connected to a third node;

(c) a second diode having an anode operatively connected to said second node and a cathode operatively connected to said third node;

(d) a third diode having an anode operatively connected to a fourth node and a cathode operatively connected to said second node;

(e) a fourth diode having an anode operatively connected to said fourth node and a cathode operatively connected to said first node;

(f) first and second active switch means for connecting and disconnecting said DC power source to and from said DC load, said first active switch means operatively connected across said second diode, said second switch means operatively connected across said third diode;

(g) a first resonant capacitor;

(h) a second resonant capacitor;

wherein said first resonant capacitor is operatively connected to said first node such that any voltage change across said first resonant capacitor necessitates a substantially equal voltage change across said fourth diode as represented by ##EQU6## and wherein said second capacitor is operatively connected to said second node such that any voltage change across said second resonant capacitor necessitates a substantially equal voltage change across said third diode as represented by ##EQU7## when said switching bridge is operatively connected to said converter such that any voltage change across said fourth diode necessitates a substantially equal and opposite voltage change across said first diode;

at least one filtering inductor having first and second ends, said first end operatively connected to said first node, said second end operatively connected to said DC power source;

at least one filtering capacitor having a first terminal and a second terminal, the first terminal coupled to said third node and the second terminal coupled to said fourth node;

a timing means for controlling a conduction interval for each of said first active switch means and said second active switch means so that said second active switch means conducts current for a percentage D of a switching period T_S, and said first active switch means conducts current only when said second active switch means is turned off such that said first active switch means and said second active switch means and said first diode and said fourth diode turn on and turn off with substantially zero volts across them.

2. The converter of claim 1 wherein said switching bridge further comprises third active switch means for connecting and disconnecting said power source to and from said load, said third active switch means operatively connected across said fourth diode, such that current conduction through said third active switch means while said first active switch means conducts current assures the turn-on of said second active switch means with substantially zero volts.

5. The converter of claim 1 wherein at least one of said first and second active switch means comprises semiconductor means.

6. The converter of claim 2 wherein at least one of said first, second and third active switch means comprises semiconductor means.

3. The converter of claim 3 wherein said switching bridge means further comprises fourth active switch means operatively connected across said first diode such that current conduction through said fourth active switch means while said second active switch means conducts current assures the turn-on of said first active switch means with substantially zero volts.

4. The converter of claim 3 wherein at least one of said first, second, third, and fourth active switch means comprises semiconductor means.