Dc-to-dc converter

• US 6,396,719 B2
• Filed: 05/17/2001
• Issued: 05/28/2002
• Est. Priority Date: 05/31/2000
• Status: Expired due to Fees

• Current Assignee: Sanken Electric Company Limited
• Original Assignee: Sanken Electric Company Limited
• Inventors: Yamagishi, Toshiyuki, Morita, Koichi
• Primary Examiner(s): Nguyen, Matthew
• Application Number:
  US09/859,935
• Publication Number:
  US 20010050853A1
• Time in Patent Office: 376 Days
• Field of Search: 363/16,20,21.01,21.02,21.03,21.12,21.14,95,97,131
• US Class Current: 363/21.12
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33569 having several active switching elements H02M3/3353 takes precedence
• 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 transformer has a primary winding connected across a d.c. power supply via a parallel connection of a switch and a resonant capacitor, and a secondary winding connected across a load via a rectifying and smoothing circuit. In order for the switch to be turned on and off at zero voltage, there is provided, in parallel with the serial circuit of the transformer primary and the switch, a serial circuit of a tertiary and a quaternary winding of the transformer, a resonant inductor, a first diode, and a second switch. A second diode is connected in parallel with the serial connection of the transformer quaternary, resonant inductor, first diode, and second switch. A switch control circuit is connected between the rectifying and smoothing circuit and the first and second switches for on-off control of the latter according to the converter output voltage. The second switch is so controlled in relation to the first switch that the resonant capacitor is compulsorily caused to discharge, making the voltage across the first switch zero when it is turned on.

Claims

1. A d.c.-to-d.c. converter to be connected between a d.c. power supply and a load, comprising:

(a) a pair of input terminals to be connected to a d.c. power supply;

(b) a transformer having a primary winding, a secondary winding, a tertiary winding, and a quaternary winding which are all electromagnetically coupled together, the primary winding having one extremity thereof connected to one of the pair of input terminals;

(c) a pair of output terminals to be connected to a load;

(d) a rectifying and smoothing circuit connected between the secondary winding of the transformer and the pair of output terminals;

(e) a first switch connected between the other extremity of the primary winding of the transformer and the other of the pair of input terminals;

(f) resonant capacitance means connected in parallel with the first switch;

(g) resonant inductance means;

(h) a first diode;

(i) a second switch, the tertiary winding and quaternary winding of the transformer and the resonant inductance means and the first diode and the second switch being all connected in series with one another and in parallel with the serial connection of the primary winding of the transformer and the first switch, the first diode being so oriented as to be forward-biased by a supply voltage to be applied from the pair of input terminals;

(j) a second diode connected in parallel with the serial connection of the quaternary winding of the transformer and the resonant inductance means and the first diode and the second switch, the second diode being so oriented as to be reverse-biased by the supply voltage to be applied from the pair of input terminals; and

(k) a switch control circuit connected to the first and the second switch for making on-off control of the first and the second switch, the switch control circuit including means for turning on the second switch at a first moment that is earlier than a starting moment of each conducting period of the first switch and turning off the second switch at a second moment that is equal to or earlier than an ending moment of each conducting period of the first switch.

2. The d.c.-to-d.c. converter of claim 1 wherein the switch control circuit comprises:

(a) voltage detector means connected to the rectifying and smoothing circuit for putting out a voltage in proportion to the converter output voltage being applied to the load;

(b) a voltage divider circuit connected to the voltage detector means for putting out a voltage indicative of a predetermined fraction of the output voltage of the voltage detector means;

(c) a wave generator for generating a periodic wave;

(d) a first comparator having inputs connected to the voltage detector means and the wave generator for putting out a first switch control signal in the form of a series of pulses indicative of whether the output voltage of the voltage detector means is greater or less than the periodic wave, the first comparator having an output connected to the first switch for on-off control thereof by the first switch control signal;

(e) a second comparator having inputs connected to the voltage divider circuit and the wave generator for providing a series of output pulses indicative of whether the output voltage of the voltage divider circuit is greater or less than the periodic wave; and

(f) a pulse generator connected to the second comparator for putting out a second switch control signal in the form of a series of pulses each rising with one output pulse of the second comparator and each decaying equal to or earlier than one output pulse of the first comparator, the pulse generator having an output connected to the second switch for on-off control thereof by the second switch control signal.

3. The d.c.-to-d.c. converter of claim 2 wherein the pulse generator of the switch control circuit is a monostable multivibrator.

4. The d.c.-to-d.c. converter of claim 1 wherein the switch control circuit comprises:

(a) voltage detector means connected to the rectifying and smoothing circuit for putting out a voltage in proportion to the converter output voltage being applied to the load;

(b) a voltage divider circuit connected to the voltage detector means for putting out a voltage indicative of a predetermined fraction of the output voltage of the voltage detector means;

(c) a wave generator for generating a periodic wave;

(d) a first comparator having inputs connected to the voltage detector means and the wave generator for putting out a first series of pulses indicative of whether the output voltage of the voltage detector means is greater or less than the periodic wave;

(e) a second comparator having inputs connected to the voltage divider circuit and the wave generator for putting out a second series of pulses indicative of whether the output voltage of the voltage divider circuit is greater or less than the periodic wave;

(f) a first pulse rise detector circuit connected to the first comparator for detecting the rise of each output pulse thereof;

(g) a first pulse decay detector circuit connected to the first comparator for detecting the decay of each output pulse thereof;

(h) a second pulse rise detector circuit connected to the second comparator for detecting the rise of each output pulse thereof;

(i) a second pulse decay detector circuit connected to the second comparator for detecting the decay of each output pulse thereof;

(j) a first flip-flop connected to the first pulse rise detector circuit and the second pulse decay detector circuit in order to be set in response to the leading edge of each output pulse of the first comparator and reset in response to the trailing edge of each output pulse of the second comparator, the first flip-flop putting out a first switch control signal for on-off control of the first switch; and

(k) a second flip-flop connected to the second pulse rise detector circuit and the first pulse decay detector circuit in order to be set in response to the leading edge of each output pulse of the second comparator and reset in response to the trailing edge of each output pulse of the first comparator, the second flip-flop putting out a second switch control signal for on-off control of the second switch.

5. The d.c.-to-d.c. converter of claim 1 wherein the rectifying and smoothing circuit comprises:

(a) a rectifying diode connected to one extremity of the secondary winding of the transformer and so polarized as to become conductive in response to the a voltage building up in the transformer secondary when the first switch is off; and

(b) a smoothing capacitor connected in parallel with the transformer secondary via the rectifying diode.

6. The d.c.-to-d.c. converter of claim 1 wherein the tertiary winding and quaternary winding of the transformer are of the same polarity as the primary winding of the transformer with respect to the supply voltage to be applied from the pair of input terminals.

7. The d.c.-to-d.c. converter of claim 1 further comprising a third diode connected in parallel with the first switch, the third diode being so oriented as to be reverse-biased by the supply voltage to be applied from the pair of input terminals.