Zero voltage switching boost topology

Details Zero voltage switching boost topology Zero voltage switching boost topology

2000-06-02

2001-05-22

Riley, Shawn (Department: 2838)

Electricity: power supply or regulation systems

In shunt with source or load

Using a three or more terminal semiconductive device

C323S222000, C323S235000

Reexamination Certificate

active

06236191

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to DC-DC converters and, more particularly, to an improved circuit topology for boost converters.
BACKGROUND OF THE INVENTION
A boost converter is a type of forward converter where a smaller input DC voltage is increased to a desired level. A typical boost converter includes an inductor to which the input voltage is coupled that is in series with a diode connected to an output capacitor across which the load is connected. A transistor switch is connected to a node between the inductor and diode and ground to provide regulation of the output voltage. The control circuit for the transistor switch includes a comparator for sensing and comparing the output voltage of the converter to a voltage reference to generate an error voltage. This error voltage is then coupled to a duty cycle limited constant frequency pulse width modulator circuit (PWM). The PWM converts the error voltage into a control signal for controlling the timing of the on and off states of the transistor switch. When the transistor switch is on, the inductor current increases, storing energy in its magnetic field. When the transistor is off, energy is transferred via the diode to the load and the output energy storage capacitor. The transistor switch is operated at a high frequency relative to the resonance of the inductor capacitor network.
Drawbacks of such conventional boost converter circuits include the creation of switch voltage and current stresses and thus low efficiency power conversion. To overcome this drawback, boost converters have been proposed that provide soft switching, i.e., switching at low voltage and current stress across the transistor switch. A prior art boost topology for this type of converter is shown in FIG.
1
.
As shown in
FIG. 1
, an input voltage V
1
is converted into output power (V
O
) using a resonant network in addition to the conventional components of a boost converter. The resonant network comprises a resonant inductor L
R
, coupled in series with resonant diodes D
1
and D
2
. An auxiliary switch S
2
and resonant inductor L
R
are in series and are connected in parallel with main switch S
1
. A resonant capacitor C
R
connects the anode of resonant diode D
1
to the anode of rectifier diode D
O
. In operation, control switches S
1
and S
2
, are switched with complementary duty cycles, i.e., when one switch is on, the other is off. The current and voltage characteristics of auxiliary switch S
2
and the resonant network of this topology are illustrated in FIG.
2
.
A drawback exhibited by the boost topology of
FIG. 1
is that, after the resonant inductor L
R
has reset, the voltage across auxiliary switch S
2
drops from a higher voltage level (of approximately 400V) to a lower voltage level (of approximately 200V). The voltage drop across auxiliary switch S
2
is illustrated by Trace A of FIG.
2
. This voltage drop causes a current to flow in the resonant diodes D
1
and D
2
prior to auxiliary switch S
2
turning on. The current flow through the resonant diodes is illustrated by Trace B of FIG.
2
. The voltage drop across auxiliary switch S
2
, coupled with the resonant diodes conducting current before the auxiliary switch S
2
turns on, results in a large amount of stress being placed on auxiliary switch S
2
and associated power losses associated with the turning on of auxiliary switch S
2
. Increased EMI noise also results. The power lost through the auxiliary switch reduces the efficiency of the boost converter.
SUMMARY OF THE INVENTION
The aforementioned and related drawbacks associated with prior art boost converters are substantially reduced or eliminated by the improved boost converter topology of the present invention. In a preferred embodiment of the present invention, the boost converter comprises an inductor coupled in series with a voltage source; a control switch coupled in parallel with the inductor and voltage source for controlling the application of voltage to a load as a function of the frequency and on and off time of the control switch, the control switch having a source, drain and gate; a diode rectifier whose anode is coupled to a first node between the control switch and the inductor and whose cathode is coupled to one of two output terminals of the boost converter for providing the voltage to a load connected thereto; an auxiliary switch, the auxiliary switch having a source, drain and gate and a duty cycle complementary to the duty cycle of the control switch; a resonant network coupled in parallel with the diode rectifier, the resonant network including an inductor, a saturable element, a first resonant diode, a second resonant diode, and a third resonant diode, and a capacitor connected between said first node and a second node between the second and third resonant diodes; and a capacitor coupled across the output terminals of the boost converter. The auxiliary switch is connected between a third node between the first and second resonant diodes and the negative terminal of said voltage source.
In a preferred embodiment of the present invention, the first resonant diode is an ultra-fast and soft recovery type diode, while the second and third resonant diodes are snap-off recovery type diodes. As such, the first resonant diode stops conducting current before the second and third resonant diodes; thereby providing that the voltage across the auxiliary switch does not drop due to the recovery current of the second and third resonant diodes. The improved topology of the present invention thus allows for the control switches to be turned on without exhibiting the level of power losses experienced by prior art boost converters.
An advantage of the present invention is that it provides the ability to turn on the control switches of a power converter without producing significant power losses.
Another advantage of the present invention is that it provides for zero voltage switching of the control switches of a power converter.
Yet another advantage of the present invention is that it reduces the amount of stress exhibited with respect to the components of a power converter and the resultant EMI noise.


REFERENCES:
patent: 5293111 (1994-03-01), Weinberg
patent: 5414613 (1995-05-01), Chen
patent: 5486752 (1996-01-01), Hua et al.
patent: 5543704 (1996-08-01), Thoren
patent: 5736841 (1998-04-01), Gucyski
patent: 5736842 (1998-04-01), Jovanovic
patent: 5793190 (1998-08-01), Sahstrom et al.
patent: 5815386 (1998-09-01), Gordon
patent: 5841268 (1998-11-01), Mednik
patent: 5914587 (1999-06-01), Liu
patent: 5923153 (1999-07-01), Liu
patent: 5959438 (1999-09-01), Jovanovic
patent: 5977754 (1999-11-01), Cross
patent: 5991174 (1999-11-01), Farrington
patent: 6008630 (1999-12-01), Prasad
patent: 6028418 (2000-02-01), Javanovic et al.
patent: 6051961 (2000-04-01), Jang et al.
patent: 6060867 (2000-05-01), Farrington et al.
“A Family of PWM Soft-Switching Converters Without Switch Voltage and Current Stresses,” Vilela, Coelho, Vieiera, de Freitas; IEEE 0-7803-3-73-0/96, pp. 533-536 (1996), No Month.

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