WO2007131551A1 - Switched mode power supply with storage coil - Google Patents

Switched mode power supply with storage coil Download PDF

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Publication number
WO2007131551A1
WO2007131551A1 PCT/EP2006/062368 EP2006062368W WO2007131551A1 WO 2007131551 A1 WO2007131551 A1 WO 2007131551A1 EP 2006062368 W EP2006062368 W EP 2006062368W WO 2007131551 A1 WO2007131551 A1 WO 2007131551A1
Authority
WO
WIPO (PCT)
Prior art keywords
power supply
switched mode
mode power
switching transistor
coil
Prior art date
Application number
PCT/EP2006/062368
Other languages
French (fr)
Inventor
Reinhard Kögel
Original Assignee
Tte Germany Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tte Germany Gmbh filed Critical Tte Germany Gmbh
Priority to PCT/EP2006/062368 priority Critical patent/WO2007131551A1/en
Publication of WO2007131551A1 publication Critical patent/WO2007131551A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only

Definitions

  • the present invention relates to a switched mode power supply comprising a transformer with a primary and a secondary winding, a switching transistor coupled with a current input to the primary winding of the transformer, and a driver stage for the operation of the switching transistor, and in particular to a flyback converter.
  • a switched mode power supply of this kind is used for example for consumer electronics appliances .
  • switched mode power supplies utilized for consumer electronic appliances have to provide power for a normal mode operation and for a low power standby mode operation of the appliance.
  • the normal mode operation essentially all circuits of the appliance are operating, and in the standby mode operation the energy consumption of the appliance should be as low as possible.
  • the transformer of the flyback converter When a flyback converter is used as a switched mode power supply, the transformer of the flyback converter has to be designed in accordance with the high power normal mode, which implicates a magnetic core, which is able to store sufficient energy for the normal operation and which includes also a safety margin for not reaching the saturation of the core. Because a flyback converter of this kind has to operate within a large output power interval, as required for example for television sets, video recorders and DVD players, the design of the transformer is not optimized for the stand-by mode, and the efficiency of the switched mode power supply is therefore comparatively low in the stand-by mode. On the other side, when a given switched mode power supply has to provide an increased output power, a larger transformer is necessary. In this case, a larger transformer implicates a redesign of the switched mode power supply. A fast adaptation of an existing switched mode power supply for an increased requirement of output power is therefore not possible.
  • the switched mode power supply comprises a transformer with a primary winding and a secondary winding, a switching transistor coupled to the primary winding, and a driver stage coupled to the switching transistor for the operation of the switching transistor.
  • an energy storage coil is coupled in parallel with the primary winding and in series with the switching transistor. In the storage coil energy is stored, when the switching transistor is conducting, and which energy is converted to the secondary side of the switched mode power supply, when the switching transistor is blocking.
  • the switched mode power supply operates in particular as a flyback converter for converting a DC input voltage to a DC output voltage, the DC input voltage being provided by an input capacitor coupled to the primary winding.
  • the storage coil can be easily included in an existing switched mode power supply for providing an increased output power without modifying the circuit design of the switched mode power supply, in particular without a modification of the transformer.
  • the switching frequency of the switching transistor can remain unchanged, only one additional component, a coil with a inductivity of 0,5 - 5 mH for example, is necessary.
  • the switched mode power supply is modified in a further aspect of the invention for an optimized stand-by operation, by including an additional switch being connected in series with the storage coil and being in parallel with the primary winding.
  • the switch is operated such that during stand-by operation, the storage coil is always switched off for disabling the operation of the storage coil, and during normal operating mode, the switch is closed for providing additional energy for an increased output power.
  • the switched mode power supply operates in this case with a high efficiency in a wide energy range, by including only a further small modification.
  • Fig. 1 a switched mode power supply comprising a storage coil in parallel with a primary winding of a transformer
  • FIG. 2 current diagrams of the switched mode power supply as shown in figure 1,
  • FIG. 3 current diagrams of a switched mode power supply according to prior art
  • Fig. 4 the switched mode power supply as shown in figure 1, comprising further a switch in series with the storage coil and in parallel with the primary winding of the transformer.
  • the switched mode power supply shown in figure 1 comprises a mains isolated transformer TR with a primary winding Wl, a first secondary winding W2, a further secondary winding W3 and may comprise additional secondary windings as indicated.
  • an input capacitor Cl is coupled which receives a DC voltage for example from a rectified mains supply.
  • a switching transistor Tl is coupled with a current input to a second terminal 2 of the primary winding Wl and with a current output to ground, for being arranged in series with the primary winding Wl.
  • the switching transistor Tl is operated by a driver stage DR, which is coupled with an output to a control input of the switching transistor Tl.
  • the secondary winding W2 provides via a rectifying diode Dl and a smoothing capacitor C2 a DC output voltage Ul .
  • the output voltage Ul is coupled via a feedback circuit FB to the driver stage DR of the primary side for a regulation of the output voltage Ul .
  • the switched mode power supply operates in particular as a flyback converter, in which during operation in a conduction phase of the switching transistor TR energy is stored in the core of the transformer TR, and during a blocking phase of the switching transistor Tl the energy of the transformer Tl is transferred to the secondary windings W2 and W3.
  • the switched mode power supply comprises further according to the invention a storage coil Ll arranged in parallel with the primary winding Wl and in series with the switching transistor Tl.
  • the storage coil Ll is coupled with one end to the terminal 1 and with the other end to the terminal 2 of the primary winding Wl .
  • the coil Ll comprises in particular a ferrite core with an air gap and the inductivity of the coil Ll is for example in the range of 0,5 - 5 mH.
  • the operation of the storage coil Ll is as follows: when the switching transistor Tl is conducting, a current from the capacitor Cl is flowing through the primary winding Wl as well as through the storage coil Ll .
  • the switching transistor Tl is blocking, the energy stored in the transformer TR is transferred to the secondary windings.
  • a voltage and a current are provided by the coil Ll because of the magnetic energy stored in the core of the coil Ll, and which voltage and current are applied to terminal 2 of primary winding W2. Because the switching transistor Tl is blocking, the current of the coil Ll is flowing through the primary winding Wl and therefore transferred to the secondary windings of the transformer TR in accordance with the turns ratios of the respective windings of the transformer TR.
  • the diode Dl is conducting and the energy of the storage coil Ll is therefore transferred to the capacitor C2 and also to the further secondary windings .
  • the operation of the storage coil Ll can be understood therefore as a forward mode in which the energy from the coil Ll is transferred via the transformer TR to the secondary side of the switched mode power supply during the blocking phase of the switching transistor Tl.
  • the transformer TR is transferring the current from the coil Ll to the secondary windings in a conduction mode of the transformer TR, the design of the transformer TR has not to be changed with regard to a flyback converter without a storage coil Ll, because the energy, which is coming from the coil Ll, has not to be stored in the transformer TR.
  • the saturation margin of the transformer TR is therefore preserved, but the output power of the switched mode power supply has been increased by including the coil Ll .
  • FIG 2 respective currents during operation of the switched mode power supply of figure 1 are shown.
  • Figure 2a shows the current of the primary winding Wl of transformer TR, as caused by the switching transistor Tl.
  • the switching transistor Tl In time intervals tl - t2 and t3 - t4 the switching transistor Tl is conducting, therefore drawing respective currents from the input capacitor Cl through the primary winding Wl and the coil Ll .
  • the switching transistor Tl In the time interval t2 - t3 the switching transistor Tl is blocking, blocking therefore current from the capacitor Cl through the primary winding Wl and coil Ll .
  • FIG 2b the current through the storage coil Ll is shown.
  • time interval tl - t2 when the switching transistor Tl is conducting, a current flows from the capacitor Cl through the storage coil Ll and energy is stored in the core of Ll, due to the inductivity of the coil Ll.
  • the current through the coil Ll continues to flow, but flows now through primary winding Wl, from terminal 2 to terminal 1.
  • the voltage generated by the coil across primary winding Wl is transformed to the secondary winding W2, and because the switched mode power supply operates as a flyback converter, the diode Dl is conducting.
  • FIG 3 the current through the primary winding Wl, figure 3a, and the current through the diode Dl, figure 3b, are shown for a switched mode power supply without the storage coil Ll, as known from prior art.
  • the power supply operates here in a discontinuous mode, in which the current through the diode Dl declines to zero in the interval t2 - t3 before the next switching cycle t3 - t4 starts, in which the switching transistor Tl again is conducting.
  • the switched mode power supply shown in figure 1 comprises in addition a switch Sl, coupled in series with the storage coil Ll and the switching transistor Tl and in parallel with the primary winding Wl, as shown in figure 4.
  • the switch Sl allows to decouple the storage coil Ll from the switching transistor Tl and the primary winding Wl, respectively allows to disable the operation of the coil Ll.
  • the switch Sl can be a bipolar transistor, a MOSFET or for example also a relay.
  • the switched mode power supply of figure 4 operates in particular in a low energy standby mode or in a normal mode, in which the power supply provides a high output power for a full operation of a respective appliance.
  • the switch Sl is operated such, that during standby mode the switch Sl is open and during normal operation mode the switch Sl is closed.
  • the transformer TR is here designed as a standby transformer, with the requirement that the thickness of the wires of the windings Wl, W2 and W3 are capable of the total power of the switched mode power supply.
  • the inductivity of the primary winding Wl can be optimized therefore to the standby mode by increasing the inductivity. Hence, the conduction time of the switching transistor can be increased also for improving the efficiency and the reliability of the switched mode power supply.
  • the additional storage coil Ll is designed to store about the total power for the normal operating mode of the switched mode power supply.
  • the dimensions of the transformer TR can be reduced therefore, which leads to reduced conduction losses and magnetization losses during standby mode and therefore to an increased efficiency.

Abstract

The switched mode power supply comprises a transformer (TR) with a primary winding (W1) and a secondary winding (W2), a switching transistor (T1) coupled to the primary- winding (W1), and a driver stage (DR) coupled to the switching transistor (T1), and in addition a storage coil (L2) is coupled in parallel with the primary winding (W1) and in series with the switching transistor (T1) as an energy storage. In the storage coil energy is stored, when the switching transistor is conducting, which energy is converted to the secondary side of the switched mode power supply, when the switching transistor is blocking. The switched mode power supply operates in particular as a flyback converter converting a DC input voltage to a DC output voltage. The storage coil provides an increased output power of an existing switched mode power supply without any essential modifications of the circuit design, in particular without a modification of the transformer.

Description

Switched mode power supply with storage coil
Field of the invention
The present invention relates to a switched mode power supply comprising a transformer with a primary and a secondary winding, a switching transistor coupled with a current input to the primary winding of the transformer, and a driver stage for the operation of the switching transistor, and in particular to a flyback converter. A switched mode power supply of this kind is used for example for consumer electronics appliances .
Background
It is well known that switched mode power supplies utilized for consumer electronic appliances have to provide power for a normal mode operation and for a low power standby mode operation of the appliance. In the normal mode operation essentially all circuits of the appliance are operating, and in the standby mode operation the energy consumption of the appliance should be as low as possible.
When a flyback converter is used as a switched mode power supply, the transformer of the flyback converter has to be designed in accordance with the high power normal mode, which implicates a magnetic core, which is able to store sufficient energy for the normal operation and which includes also a safety margin for not reaching the saturation of the core. Because a flyback converter of this kind has to operate within a large output power interval, as required for example for television sets, video recorders and DVD players, the design of the transformer is not optimized for the stand-by mode, and the efficiency of the switched mode power supply is therefore comparatively low in the stand-by mode. On the other side, when a given switched mode power supply has to provide an increased output power, a larger transformer is necessary. In this case, a larger transformer implicates a redesign of the switched mode power supply. A fast adaptation of an existing switched mode power supply for an increased requirement of output power is therefore not possible.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a switched mode power supply which is easily adjustable with regard to different output power requirements.
This object is achieved for a switched mode power supply as defined in claim 1. Preferred embodiments of the invention are described in the dependent claims.
The switched mode power supply according to the invention comprises a transformer with a primary winding and a secondary winding, a switching transistor coupled to the primary winding, and a driver stage coupled to the switching transistor for the operation of the switching transistor. In addition, an energy storage coil is coupled in parallel with the primary winding and in series with the switching transistor. In the storage coil energy is stored, when the switching transistor is conducting, and which energy is converted to the secondary side of the switched mode power supply, when the switching transistor is blocking. The switched mode power supply operates in particular as a flyback converter for converting a DC input voltage to a DC output voltage, the DC input voltage being provided by an input capacitor coupled to the primary winding.
The storage coil can be easily included in an existing switched mode power supply for providing an increased output power without modifying the circuit design of the switched mode power supply, in particular without a modification of the transformer. The switching frequency of the switching transistor can remain unchanged, only one additional component, a coil with a inductivity of 0,5 - 5 mH for example, is necessary.
The switched mode power supply is modified in a further aspect of the invention for an optimized stand-by operation, by including an additional switch being connected in series with the storage coil and being in parallel with the primary winding. The switch is operated such that during stand-by operation, the storage coil is always switched off for disabling the operation of the storage coil, and during normal operating mode, the switch is closed for providing additional energy for an increased output power. The switched mode power supply operates in this case with a high efficiency in a wide energy range, by including only a further small modification.
SHORT DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are explained now in more detail with regard to schematic drawings, which show:
Fig. 1 a switched mode power supply comprising a storage coil in parallel with a primary winding of a transformer,
Fig. 2 current diagrams of the switched mode power supply as shown in figure 1,
Fig. 3 current diagrams of a switched mode power supply according to prior art, and Fig. 4 the switched mode power supply as shown in figure 1, comprising further a switch in series with the storage coil and in parallel with the primary winding of the transformer.
PREFERRED EMBODIMENTS OF THE INVENTION The switched mode power supply shown in figure 1 comprises a mains isolated transformer TR with a primary winding Wl, a first secondary winding W2, a further secondary winding W3 and may comprise additional secondary windings as indicated. To a first terminal 1 of the primary winding Wl an input capacitor Cl is coupled which receives a DC voltage for example from a rectified mains supply. A switching transistor Tl is coupled with a current input to a second terminal 2 of the primary winding Wl and with a current output to ground, for being arranged in series with the primary winding Wl. The switching transistor Tl is operated by a driver stage DR, which is coupled with an output to a control input of the switching transistor Tl.
The secondary winding W2 provides via a rectifying diode Dl and a smoothing capacitor C2 a DC output voltage Ul . The output voltage Ul is coupled via a feedback circuit FB to the driver stage DR of the primary side for a regulation of the output voltage Ul . The switched mode power supply operates in particular as a flyback converter, in which during operation in a conduction phase of the switching transistor TR energy is stored in the core of the transformer TR, and during a blocking phase of the switching transistor Tl the energy of the transformer Tl is transferred to the secondary windings W2 and W3.
As the driver stage DR, a circuit with discrete transistors may be used or an integrated controller circuit. The switched mode power supply as described so far is well known from prior art and illustrated therefore in figure 1 only schematically. An integrated controller circuit for a switched mode power supply of this kind is for example the integrated circuit FSDM0265RL manufactured by Fairchild Semiconductor Operation. Details about the function and design of typical power supply application circuits can be found in respective data sheets . The switched mode power supply comprises further according to the invention a storage coil Ll arranged in parallel with the primary winding Wl and in series with the switching transistor Tl. The storage coil Ll is coupled with one end to the terminal 1 and with the other end to the terminal 2 of the primary winding Wl . The coil Ll comprises in particular a ferrite core with an air gap and the inductivity of the coil Ll is for example in the range of 0,5 - 5 mH.
The operation of the storage coil Ll is as follows: when the switching transistor Tl is conducting, a current from the capacitor Cl is flowing through the primary winding Wl as well as through the storage coil Ll . When the switching transistor Tl is blocking, the energy stored in the transformer TR is transferred to the secondary windings. In addition, a voltage and a current are provided by the coil Ll because of the magnetic energy stored in the core of the coil Ll, and which voltage and current are applied to terminal 2 of primary winding W2. Because the switching transistor Tl is blocking, the current of the coil Ll is flowing through the primary winding Wl and therefore transferred to the secondary windings of the transformer TR in accordance with the turns ratios of the respective windings of the transformer TR.
Because the voltage generated by the storage coil Ll is higher at terminal 2 with regard to terminal 1 when the switching transistor Tl is blocking, the diode Dl is conducting and the energy of the storage coil Ll is therefore transferred to the capacitor C2 and also to the further secondary windings . The operation of the storage coil Ll can be understood therefore as a forward mode in which the energy from the coil Ll is transferred via the transformer TR to the secondary side of the switched mode power supply during the blocking phase of the switching transistor Tl. Because the transformer TR is transferring the current from the coil Ll to the secondary windings in a conduction mode of the transformer TR, the design of the transformer TR has not to be changed with regard to a flyback converter without a storage coil Ll, because the energy, which is coming from the coil Ll, has not to be stored in the transformer TR. The saturation margin of the transformer TR is therefore preserved, but the output power of the switched mode power supply has been increased by including the coil Ll .
In figure 2 respective currents during operation of the switched mode power supply of figure 1 are shown. Figure 2a shows the current of the primary winding Wl of transformer TR, as caused by the switching transistor Tl. In time intervals tl - t2 and t3 - t4 the switching transistor Tl is conducting, therefore drawing respective currents from the input capacitor Cl through the primary winding Wl and the coil Ll . In the time interval t2 - t3 the switching transistor Tl is blocking, blocking therefore current from the capacitor Cl through the primary winding Wl and coil Ll .
In figure 2b the current through the storage coil Ll is shown. During time interval tl - t2, when the switching transistor Tl is conducting, a current flows from the capacitor Cl through the storage coil Ll and energy is stored in the core of Ll, due to the inductivity of the coil Ll. In the time interval t2 - t3, the current through the coil Ll continues to flow, but flows now through primary winding Wl, from terminal 2 to terminal 1. The voltage generated by the coil across primary winding Wl is transformed to the secondary winding W2, and because the switched mode power supply operates as a flyback converter, the diode Dl is conducting. The energy stored in the coil Ll is therefore transferred completely to the capacitor C2 as well as to the other secondary windings during the blocking phase of the switching transistor TR. In figure 2c the current through the diode Dl is shown, comprising the contributions of the energy as stored in the storage coil Ll and the energy as stored in the transformer TR. The energy coming from the storage coil Ll, which generates a current through primary winding Wl, is therefore not stored in the transformer TR, but directly transformed to the secondary windings W2 and W3. Hence, the output power of the switched mode power supply has been increased, without changing the saturation margin of the transformer.
In figure 3 the current through the primary winding Wl, figure 3a, and the current through the diode Dl, figure 3b, are shown for a switched mode power supply without the storage coil Ll, as known from prior art. The power supply operates here in a discontinuous mode, in which the current through the diode Dl declines to zero in the interval t2 - t3 before the next switching cycle t3 - t4 starts, in which the switching transistor Tl again is conducting.
In a further embodiment of the invention, the switched mode power supply shown in figure 1 comprises in addition a switch Sl, coupled in series with the storage coil Ll and the switching transistor Tl and in parallel with the primary winding Wl, as shown in figure 4. The switch Sl allows to decouple the storage coil Ll from the switching transistor Tl and the primary winding Wl, respectively allows to disable the operation of the coil Ll. The switch Sl can be a bipolar transistor, a MOSFET or for example also a relay.
The switched mode power supply of figure 4 operates in particular in a low energy standby mode or in a normal mode, in which the power supply provides a high output power for a full operation of a respective appliance. The switch Sl is operated such, that during standby mode the switch Sl is open and during normal operation mode the switch Sl is closed. The transformer TR is here designed as a standby transformer, with the requirement that the thickness of the wires of the windings Wl, W2 and W3 are capable of the total power of the switched mode power supply. The inductivity of the primary winding Wl can be optimized therefore to the standby mode by increasing the inductivity. Hence, the conduction time of the switching transistor can be increased also for improving the efficiency and the reliability of the switched mode power supply.
The additional storage coil Ll is designed to store about the total power for the normal operating mode of the switched mode power supply. The dimensions of the transformer TR can be reduced therefore, which leads to reduced conduction losses and magnetization losses during standby mode and therefore to an increased efficiency.
Design and operation of the remaining part of the switched mode power supply of figure 4 correspond with the power supply as shown in figure 1, and like circuit elements are labeled with same reference symbols. The invention has been described with regard to flyback converters as shown in figures 1 and 4, but an application of the invention to other switched mode power supplies, for example half bridge converters, is also within reach of a person skilled in the art without departing from the scope of the present invention.

Claims

Claims
1. Switched mode power supply comprising a transformer (TR) with a primary winding (Wl) and a secondary winding (W2), a switching transistor (Tl) coupled to the primary winding (Wl), and a driver stage (DR) coupled to the switching transistor (Tl) , characterized in that a coil (L2) is coupled in parallel with the primary winding (Wl) as an energy storage.
2. Switched mode power supply according to claim 1, wherein the switched mode power supply operates as a flyback converter for converting a DC input voltage (U+) provided by an input capacitor (Cl) into a DC output voltage (Ul) , the input capacitor (Cl) being coupled to a first terminal (1) of the primary winding (Wl) .
3. Switched mode power supply according to claim 1 or 2, wherein during operation of the switched mode power supply, energy is stored in the coil (L2), when the switching transistor is conducting, and which energy- is converted to the primary side of the switched mode power supply, when the switching transistor is blocking.
4. Switched mode power supply according to claim 1, 2 or 3, wherein a switch (Sl) is connected in series with the coil (L2) and in parallel with the primary winding (Wl), for disabling the operation of the coil (L2) in a standby mode.
5. Switched mode power supply according to claim 4, wherein the switched mode power supply comprises a normal mode operation and a standby mode operation, and wherein the primary winding (Wl) is designed in accordance with power requirements for the standby mode operation and the coil (L2) is designed in accordance with power requirements for the normal mode operation.
6. Switched mode power supply according to claim 4 or 5, wherein the switch (Sl) is a relay, a bipolar transistor or a MOSFET transistor.
7. Switched mode power supply according to one of the preceding claims, wherein the coil (Ll) comprises a ferrite core with an air gap and the inductivity of the coil (Ll) is in the range of 0,5 - 5 mH.
PCT/EP2006/062368 2006-05-17 2006-05-17 Switched mode power supply with storage coil WO2007131551A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2006/062368 WO2007131551A1 (en) 2006-05-17 2006-05-17 Switched mode power supply with storage coil

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2006/062368 WO2007131551A1 (en) 2006-05-17 2006-05-17 Switched mode power supply with storage coil

Publications (1)

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WO2007131551A1 true WO2007131551A1 (en) 2007-11-22

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6249444B1 (en) * 1999-11-01 2001-06-19 Astec International Limited Offset resonant ZVS forward converter
WO2002007296A1 (en) * 2000-07-18 2002-01-24 Coutant Lambda Limited A dc switching regulator
US20020136032A1 (en) * 2001-02-12 2002-09-26 Delta Electronics, Inc. Asymmetrical full bridge dc-to-dc converter

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6249444B1 (en) * 1999-11-01 2001-06-19 Astec International Limited Offset resonant ZVS forward converter
WO2002007296A1 (en) * 2000-07-18 2002-01-24 Coutant Lambda Limited A dc switching regulator
US20020136032A1 (en) * 2001-02-12 2002-09-26 Delta Electronics, Inc. Asymmetrical full bridge dc-to-dc converter

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