GB2455568A - Protection system for a resonant converter with synchronous rectification - Google Patents

Protection system for a resonant converter with synchronous rectification Download PDF

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Publication number
GB2455568A
GB2455568A GB0724431A GB0724431A GB2455568A GB 2455568 A GB2455568 A GB 2455568A GB 0724431 A GB0724431 A GB 0724431A GB 0724431 A GB0724431 A GB 0724431A GB 2455568 A GB2455568 A GB 2455568A
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United Kingdom
Prior art keywords
override
rectifier switch
circuit
rectifier
sri
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB0724431A
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GB0724431D0 (en
Inventor
Thomas Andre Olsen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eltek Valere AS
Original Assignee
Eltek Valere AS
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 Eltek Valere AS filed Critical Eltek Valere AS
Priority to GB0724431A priority Critical patent/GB2455568A/en
Publication of GB0724431D0 publication Critical patent/GB0724431D0/en
Priority to PCT/NO2008/000416 priority patent/WO2009078728A1/en
Publication of GB2455568A publication Critical patent/GB2455568A/en
Withdrawn legal-status Critical Current

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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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
    • H02H7/127—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers having auxiliary control electrode to which blocking control voltages or currents are applied in case of emergency
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • H02M3/33569—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 having several active switching elements
    • H02M3/33576—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—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 having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)
  • Dc-Dc Converters (AREA)

Abstract

A protection system for a resonant converter comprises sensors 1,2 to measure the voltage across each synchronous rectifier switch Sr1, Sr2 and an override circuit 0C1, 0C2 for each rectifier to override a control signal from a control system when the measured voltage over the opposite rectifier switch is below a predetermined threshold value ( fig 2c Vref). The circuit may included a comparator (fig 2c) and the rectifiers can be switched off when overridden, using an AND gate or diodes (fig 2c). The converter may be an LLC resonant converter.

Description

Title: Protection system
FIELD OF THE thWENTION
The present invention relates to a protection system for a resonant converter with synchronous rectifiers.
PRIOR ART
Several types of converters are known for use in power supply systems, where there is a need to convert an AC power to a controlled DC power. The AC power will usually be supplied from an AC power source, such as the mains. The DC power is supplied to equipment such as telecommunication equipment, broad band data communication equipment, military equipment, medical equipment etc. Several such converters are known. For example is a boost converter shown and described in "Power Electronics: converters, applications, and design", 2 ed., by Mohan, Undeland and Robbins in chapter 7-4. In the same book, different DC-DC converter topologies are described in chapter 10-4 and 10-5. Synchronous rectifiers are also known in the art, to further control the output voltage of power supply systems.
The requirements for the DC power can vary, but usually it is important to keep the DC voltage within certain boundaries and also to protect the DC side from irregularities in the voltage/current oii the AC side. Failures may also occur in the load, which causes a surge voltage or current to enter the power supply system from the DC side.
Consequently, it is important to protect both the electrical components of the telecommunication equipment, i.e. the load, and also to protect the electrical components of the power supply system itself.
The switches of the power supply systems are more and more being controlled digitally, for example by means of a programmed digital signal processor (DSP).
The DSP receives voltage and current measurements from sensors in the power supply system, and calculates the current state continuously. If one or some of the measurements indicate that a dangerous state has occurred, for example that the input voltage is above a certain level, the DSP provides for that the system goes into a failsafe mode, for example by turning off all switches of the system.
However, there are some disadvantages related to the above control system. The DSP can, in certain situations, be busy with calculations, thereby causing the failsafe mode to be delayed, thereby causing components to be damaged by the surge voltage. çpçqycr, i has been fgund difficult to predict all possible failure situations and combinations of failure situations and program those into the DSP.
The object of the invention is to provide an improved protection system where the disadvantages mentioned above are avoided.
SUMMARY OF THE INVENTION
The present invention relates to a protection system for a resonant converter with synchronous rectification, where the resonant converter is comprising a control system for providing control signals to first and second rectifier switches of the converter, characterized in that the protection system comprises: -a first sensing means for measuring the voltage over the first rectifier switch and a second sensing means for measuring the voltage over the second rectifier switch; -comparator circuits for comparing the measured voltages from the first and second sensing means with a predetermined threshold value Vref; -an override circuit for each of the first and second rectifier switches, for overriding the control signal from the control system when the measured voltage over the opposite rectifier switch is below a predetermined threshold value Vref.
In an aspect of the invention, the override circuit comprises a first input terminal receiving the control signal from the control system, a second input terminal receiving an override signal from the comparator circuit, and an output terminal connected to a gate terminal of the rectifier switch either directly or by means of a gate driver circuit.
In an aspect of the invention, the rectifier switch is turned OFF when overridden by the protection system.
In an aspect of the invention, the override circuit for the first rectifier switch receives an override signal when the voltage over the second rectifier switch is below the predetermined threshold value Vref and that the override circuit for the second rectifier switch (5r2) receives an override signal when the voltage over the first rectifier switch (Sri) is below the predetermined threshold value Vref.
In an aspect of the invention, the override circuits comprise a logic AND circuit element.
In an aspect of the invention, the override circuits comprise a diode connected with its anode to a gate driver circuit for the second rectifier switch and to the control signal for the second rectifier switch and with its cathode to the output of the comparator circuit.
In an aspect of the invention, the convertçr Is a L4 ser rcQajfl poRyert,c ytl synchronous rectification.
The present invention also relates to a resonant converter with synchronous rectification, characterized in that it comprises a protection system as described above.
DETAILED DESCRIPTION
Embodiments of the invention will now be described with reference to the enclosed drawings, where: Fig. I illustrates the topology of a first embodiment of the invention; Fig. 2a and 2b illustrate an embodiment of the override circuits for the two rectifier switches respectively; Fig. 2c illustrates an alternative embodiment of the override circuit for one of the rectifier switches.
The first embodiment of the invention is illustrated in fig. 1, where it is shown a DC-DC converter with a synchronous rectifier. More specifically, the converter is a LLC series converter with a synchronous rectifier.
The DC-DC converter would normally be connected to an AC/DC converter (not shown), for example a bridgeless boost converter. In the present embodiment, the input terminals of the DC-DC converter is a positive boost output terminal Obp and a negative boost output terminal Obn of such a bridgeless boost converter. It should be noted that the input terminals can be another DC source, for example the output terminals of another type of AC/DC converter.
A boost capacitor Cbl is connected between the terminals Obp and Obn, as shown in fig. I. The DC-DC converter comprises a first dc-dc switch Sdcl connected between the positive output terminal Obp of the boost converter and a third node 3 and a second dc-dc switch Sdc2 connected between the negative output terminal Obn of the boost converter and the third node 3.
A dc-dc inductor Ldc is connected between the third node 3 and a first input terminal of a transformer device Tdc. A dc-dc capacitor Cdc is connected between the negative output terminal Obn of the boost converter and a second input terminal of the transformer device Tdc.
The topology on the secondary side or output side of the DC-DC converter is often referred to as a synchronous rectifier.
Here, a first rectifier switch Sri is connected between a first output terminal of the transformer device Tdc and a negative dc-dc output terminal Odcn.
A second rectifier switch Sr2 is connected between a second output terminal of the transformer device Tdc and the negative dc-dc output terminal Odcn.
A positive dc-dc output terminal Odcp is connected directly to a third output terminal of the transformer device Tdc. The third output terminal is an output terminal between the first and second output terminals, and consequently, the voltage level at the third terminal is between the voltage levels at the first and second terminals. In the present embodiment, the number of windings between the first and third terminal is half of the number of windings between the first and second terminals.
A rectifier capacitor Cr is connected between the positive dc-dc output terminal Odcp and the negative dc-dc output terminal Odcn.
The converter comprises a control system (illustrated with dashed lines) for controlling the first and second rectifier switches Sbl, Sb2. The control system will also be controlling the dc-dc switches Sdcl, Sdc2 (even though not shown in fig. 1).
The operation of the control system is based on input from sensors that measures voltages and/or currents in the converter. In fig. 1 it is shown that the output voltage over the rectifier capacitor Cr is used as an input to the control system, however, other parameters can be used as well. The control system can be of a type that is known for a man skilled in the art, and will not be described here in detail.
The control system controls the switches to provide an optimal (i.e. regarding quality, regarding specified voltage and current output etc) output power to the positive and negative dc-dc output terminals Odcp, Odcn.
The elements of the protection system according the present embodiment are illustrated in fig. 1. The protection system comprises a first sensing means or first sensor I and a second sensing means or second sensor 2. The first sensor 1 is measuring the voltage Vsrl over the first rectifier switch Sri. The second sensor 2 is measuring the voltage Vsr2 over the second rectifier switch Sr2.
The protection system also comprises first and second override circuits OCI and 0C2, as shown in fig. 1. Also the control signals from the control system are input to the respective override circuits. The override circuits will be described in detail below.
Moreover, the protection system uses a reference voltage Vref for the voltage over the respective rectifier switches Sri and Sr2. The reference voltage Vref will be dependent of the components that are chosen in the topology, however, it must be so large that dangerous operation is avoided, and at the same time should not be to large to reduce power efficiency.
The protection system also comprises comparator circuits to provide a comparison of the following parameters to provide the override functionality: 1: If VsrI <Vref, then disable control signal to the second rectifier switch Sr2. If not, enable control signal to rectifier switch Sr2. The protection system provides this by an override signal to the second override circuit 0C2.
2: If Vsr2 <Vref, then disable control signal to the first rectifier switch Sri. If not, enable control signal to rectifier switch Sri. The protection system provides this by an override signal to the first override circuit OCi.
It should be noted that the override signal for the first rectifier switch Sri is based on the voltage measurement of the second sensor 2 and the override signal for the second rectifier switch Sr2 is based onthe voltage measurement of the first sensor As mentioned above, the protection system comprises an override circuit OCI, 0C2 for each of the respective rectifier switches Sri, Sr2. The override circuit could for example comprise a logic AND circuit element, where the control signal from the control system and the override signal from the protection system are input to the logic AND circuit element, and where the output of the logic AND circuit element is connected directly to the trigging or gate terminal of the respective switch, according to points 1 and 2 above, or to a gatedriver circuit for the respective switches, to ensure that the voltage or current at the gate terminal of the switch is sufficient to turn the switches ON/OFF. Override circuits for the first and second switch Sri and Sr2 are illustrated in fig. 2a and 2b respectively.
In this configuration, the default output of the protection system would be logic i, i.e. no override of the control system, and the switch will be turned ON and OFF depending on the control signal (logic I and logic 0 respectively). If a dangerous state is detected by the protection system, the output of the protection system would be logic 0 and consequently the output of the logic AND circuit element would also be logic 0. Hence, the output trigging signal would change to logic 0, i.e. the switch will be turned OFF independent of the control signal from the control system.
As known for a man skilled in the art, a logic AND functionality could be implemented in many ways, also by means of an analogue circuit. Such an embodiment is illustrated in fig. 2c for switching the second rectifier switch Sr2.
Here, the protection system is shown to comprise a comparator means by means of a comparator for comparing the voltage reference Vref and the voltage Vsrl over the first switch Sri. The second override circuit OC2 comprises a diode connected with its anode to the gate driver circuit for Sr2 and to the control signal for the second switch Sr2 from the control system and with its cathode to the output of the protection system. Hence, lithe protection system detects a dangerous state, i.e. Vsrl <Vref, the output of the comparator turns to a state LOW, and consequently, the control signal from the control system is clamped to zero by means of the diode of the second override circuit OC2. If no dangerous state is detected, i.e. Vsrl is not less than Vref, the comparator turns to a state HIGH, and consequently, the control signal is forwarded to the gate driver circuit.
It should be noted that the first override circuit 0C2 can be provided correspondingly to the second override circuit described above.
According to the present embodiment, the protection system is independent of the control system, since both systems are provided with separate inputs and separate control functionality. The connection to the input terminals of the override circuits is what they have in common. Title: Protection system
FIELD OF THE thWENTION
The present invention relates to a protection system for a resonant converter with synchronous rectifiers.
PRIOR ART
Several types of converters are known for use in power supply systems, where there is a need to convert an AC power to a controlled DC power. The AC power will usually be supplied from an AC power source, such as the mains. The DC power is supplied to equipment such as telecommunication equipment, broad band data communication equipment, military equipment, medical equipment etc. Several such converters are known. For example is a boost converter shown and described in "Power Electronics: converters, applications, and design", 2 ed., by Mohan, Undeland and Robbins in chapter 7-4. In the same book, different DC-DC converter topologies are described in chapter 10-4 and 10-5. Synchronous rectifiers are also known in the art, to further control the output voltage of power supply systems.
The requirements for the DC power can vary, but usually it is important to keep the DC voltage within certain boundaries and also to protect the DC side from irregularities in the voltage/current oii the AC side. Failures may also occur in the load, which causes a surge voltage or current to enter the power supply system from the DC side.
Consequently, it is important to protect both the electrical components of the telecommunication equipment, i.e. the load, and also to protect the electrical components of the power supply system itself.
The switches of the power supply systems are more and more being controlled digitally, for example by means of a programmed digital signal processor (DSP).
The DSP receives voltage and current measurements from sensors in the power supply system, and calculates the current state continuously. If one or some of the measurements indicate that a dangerous state has occurred, for example that the input voltage is above a certain level, the DSP provides for that the system goes into a failsafe mode, for example by turning off all switches of the system.
However, there are some disadvantages related to the above control system. The DSP can, in certain situations, be busy with calculations, thereby causing the failsafe mode to be delayed, thereby causing components to be damaged by the surge voltage. çpçqycr, i has been fgund difficult to predict all possible failure situations and combinations of failure situations and program those into the DSP.
The object of the invention is to provide an improved protection system where the disadvantages mentioned above are avoided.
SUMMARY OF THE INVENTION
The present invention relates to a protection system for a resonant converter with synchronous rectification, where the resonant converter is comprising a control system for providing control signals to first and second rectifier switches of the converter, characterized in that the protection system comprises: -a first sensing means for measuring the voltage over the first rectifier switch and a second sensing means for measuring the voltage over the second rectifier switch; -comparator circuits for comparing the measured voltages from the first and second sensing means with a predetermined threshold value Vref; -an override circuit for each of the first and second rectifier switches, for overriding the control signal from the control system when the measured voltage over the opposite rectifier switch is below a predetermined threshold value Vref.
In an aspect of the invention, the override circuit comprises a first input terminal receiving the control signal from the control system, a second input terminal receiving an override signal from the comparator circuit, and an output terminal connected to a gate terminal of the rectifier switch either directly or by means of a gate driver circuit.
In an aspect of the invention, the rectifier switch is turned OFF when overridden by the protection system.
In an aspect of the invention, the override circuit for the first rectifier switch receives an override signal when the voltage over the second rectifier switch is below the predetermined threshold value Vref and that the override circuit for the second rectifier switch (5r2) receives an override signal when the voltage over the first rectifier switch (Sri) is below the predetermined threshold value Vref.
In an aspect of the invention, the override circuits comprise a logic AND circuit element.
In an aspect of the invention, the override circuits comprise a diode connected with its anode to a gate driver circuit for the second rectifier switch and to the control signal for the second rectifier switch and with its cathode to the output of the comparator circuit.
In an aspect of the invention, the convertçr Is a L4 ser rcQajfl poRyert,c ytl synchronous rectification.
The present invention also relates to a resonant converter with synchronous rectification, characterized in that it comprises a protection system as described above.
DETAILED DESCRIPTION
Embodiments of the invention will now be described with reference to the enclosed drawings, where: Fig. I illustrates the topology of a first embodiment of the invention; Fig. 2a and 2b illustrate an embodiment of the override circuits for the two rectifier switches respectively; Fig. 2c illustrates an alternative embodiment of the override circuit for one of the rectifier switches.
The first embodiment of the invention is illustrated in fig. 1, where it is shown a DC-DC converter with a synchronous rectifier. More specifically, the converter is a LLC series converter with a synchronous rectifier.
The DC-DC converter would normally be connected to an AC/DC converter (not shown), for example a bridgeless boost converter. In the present embodiment, the input terminals of the DC-DC converter is a positive boost output terminal Obp and a negative boost output terminal Obn of such a bridgeless boost converter. It should be noted that the input terminals can be another DC source, for example the output terminals of another type of AC/DC converter.
A boost capacitor Cbl is connected between the terminals Obp and Obn, as shown in fig. I. The DC-DC converter comprises a first dc-dc switch Sdcl connected between the positive output terminal Obp of the boost converter and a third node 3 and a second dc-dc switch Sdc2 connected between the negative output terminal Obn of the boost converter and the third node 3.
A dc-dc inductor Ldc is connected between the third node 3 and a first input terminal of a transformer device Tdc. A dc-dc capacitor Cdc is connected between the negative output terminal Obn of the boost converter and a second input terminal of the transformer device Tdc.
The topology on the secondary side or output side of the DC-DC converter is often referred to as a synchronous rectifier.
Here, a first rectifier switch Sri is connected between a first output terminal of the transformer device Tdc and a negative dc-dc output terminal Odcn.
A second rectifier switch Sr2 is connected between a second output terminal of the transformer device Tdc and the negative dc-dc output terminal Odcn.
A positive dc-dc output terminal Odcp is connected directly to a third output terminal of the transformer device Tdc. The third output terminal is an output terminal between the first and second output terminals, and consequently, the voltage level at the third terminal is between the voltage levels at the first and second terminals. In the present embodiment, the number of windings between the first and third terminal is half of the number of windings between the first and second terminals.
A rectifier capacitor Cr is connected between the positive dc-dc output terminal Odcp and the negative dc-dc output terminal Odcn.
The converter comprises a control system (illustrated with dashed lines) for controlling the first and second rectifier switches Sbl, Sb2. The control system will also be controlling the dc-dc switches Sdcl, Sdc2 (even though not shown in fig. 1).
The operation of the control system is based on input from sensors that measures voltages and/or currents in the converter. In fig. 1 it is shown that the output voltage over the rectifier capacitor Cr is used as an input to the control system, however, other parameters can be used as well. The control system can be of a type that is known for a man skilled in the art, and will not be described here in detail.
The control system controls the switches to provide an optimal (i.e. regarding quality, regarding specified voltage and current output etc) output power to the positive and negative dc-dc output terminals Odcp, Odcn.
The elements of the protection system according the present embodiment are illustrated in fig. 1. The protection system comprises a first sensing means or first sensor I and a second sensing means or second sensor 2. The first sensor 1 is measuring the voltage Vsrl over the first rectifier switch Sri. The second sensor 2 is measuring the voltage Vsr2 over the second rectifier switch Sr2.
The protection system also comprises first and second override circuits OCI and 0C2, as shown in fig. 1. Also the control signals from the control system are input to the respective override circuits. The override circuits will be described in detail below.
Moreover, the protection system uses a reference voltage Vref for the voltage over the respective rectifier switches Sri and Sr2. The reference voltage Vref will be dependent of the components that are chosen in the topology, however, it must be so large that dangerous operation is avoided, and at the same time should not be to large to reduce power efficiency.
The protection system also comprises comparator circuits to provide a comparison of the following parameters to provide the override functionality: 1: If VsrI <Vref, then disable control signal to the second rectifier switch Sr2. If not, enable control signal to rectifier switch Sr2. The protection system provides this by an override signal to the second override circuit 0C2.
2: If Vsr2 <Vref, then disable control signal to the first rectifier switch Sri. If not, enable control signal to rectifier switch Sri. The protection system provides this by an override signal to the first override circuit OCi.
It should be noted that the override signal for the first rectifier switch Sri is based on the voltage measurement of the second sensor 2 and the override signal for the second rectifier switch Sr2 is based onthe voltage measurement of the first sensor As mentioned above, the protection system comprises an override circuit OCI, 0C2 for each of the respective rectifier switches Sri, Sr2. The override circuit could for example comprise a logic AND circuit element, where the control signal from the control system and the override signal from the protection system are input to the logic AND circuit element, and where the output of the logic AND circuit element is connected directly to the trigging or gate terminal of the respective switch, according to points 1 and 2 above, or to a gatedriver circuit for the respective switches, to ensure that the voltage or current at the gate terminal of the switch is sufficient to turn the switches ON/OFF. Override circuits for the first and second switch Sri and Sr2 are illustrated in fig. 2a and 2b respectively.
In this configuration, the default output of the protection system would be logic i, i.e. no override of the control system, and the switch will be turned ON and OFF depending on the control signal (logic I and logic 0 respectively). If a dangerous state is detected by the protection system, the output of the protection system would be logic 0 and consequently the output of the logic AND circuit element would also be logic 0. Hence, the output trigging signal would change to logic 0, i.e. the switch will be turned OFF independent of the control signal from the control system.
As known for a man skilled in the art, a logic AND functionality could be implemented in many ways, also by means of an analogue circuit. Such an embodiment is illustrated in fig. 2c for switching the second rectifier switch Sr2.
Here, the protection system is shown to comprise a comparator means by means of a comparator for comparing the voltage reference Vref and the voltage Vsrl over the first switch Sri. The second override circuit OC2 comprises a diode connected with its anode to the gate driver circuit for Sr2 and to the control signal for the second switch Sr2 from the control system and with its cathode to the output of the protection system. Hence, lithe protection system detects a dangerous state, i.e. Vsrl <Vref, the output of the comparator turns to a state LOW, and consequently, the control signal from the control system is clamped to zero by means of the diode of the second override circuit OC2. If no dangerous state is detected, i.e. Vsrl is not less than Vref, the comparator turns to a state HIGH, and consequently, the control signal is forwarded to the gate driver circuit.
It should be noted that the first override circuit 0C2 can be provided correspondingly to the second override circuit described above.
According to the present embodiment, the protection system is independent of the control system, since both systems are provided with separate inputs and separate control functionality. The connection to the input terminals of the override circuits is what they have in common.

Claims (8)

  1. I. Protection system for a resonant converter with synchronous rectification, where the resonant converter is comprising a control system for providing control signals to first and second rectifier switches (Sri, Sr2) of the converter, characterized in that the protection system comprises: -a first sensing means (1) for measuring the voltage over the first rectifier switch (Sri) and a second sensing means (2) for measuring the voltage over the second rectifier switch (Sr2); -comparator circuits for comparing the measured voltages from the first and second sensing means (1,2) with a predetermined threshold value Vref; -an override circuit (OCI, 0C2) for each of the first and second rectifier switches (Sri, Sr2), for overriding the control signal from the control system when the measured voltage over the opposite rectifier switch (Sri, Sr2) is below a predetermined threshold value Vref.
  2. 2. System according to claim 1, characterized in that the override circuit comprises a first input terminal receiving the control signal from the control system, a second input terminal receiving an override signal from the comparator circuit, and an output terminal connected to a gate terminal of the rectifier switch either directly or by means of a gate driver circuit.
  3. 3. System according to claim 1, characterized in that the rectifier switch is turned OFF when overridden by the protection system.
  4. 4. System according to claim 1, characterized in that the override circuit for the first rectifier switch (Sri) receives an override signal when the voltage over the second rectifier switch (Sr2) is below the predetermined threshold value Vref and that the override circuit for the second rectifier switch (Sr2) receives an override signal when the voltage over the first rectifier switch (Sri) is below the predetermined threshold value Vref.
  5. 5. System according to claim 1, characterized in that the override circuits (OCI, 0C2) comprise a logic AND circuit element.
  6. 6. System according to claim 1, characterized in that the override circuits (OC1, 0C2) comprise a diode connected with its anode to a gate driver circuit for the.
    second rectifier switch (Sr2) and to the control signal for the second rectifier switch (Sr2) and with its cathode to the output of the comparator circuit.
  7. 7. System according to claim 1, characterized in that the converter is a LLC series resonant converter with synchronous rectification.
  8. 8. Resonant converter with synchronous rectification, characterized in that it comprises a protection system according to any of claims I -7.
    8. Resonant converter with synchronous rectification, characterized in that it comprises a protection system according to any of claims I -7.
    I. Protection system for a resonant converter with synchronous rectification, where the resonant converter is comprising a control system for providing control signals to first and second rectifier switches (Sri, Sr2) of the converter, characterized in that the protection system comprises: -a first sensing means (1) for measuring the voltage over the first rectifier switch (Sri) and a second sensing means (2) for measuring the voltage over the second rectifier switch (Sr2); -comparator circuits for comparing the measured voltages from the first and second sensing means (1,2) with a predetermined threshold value Vref; -an override circuit (OCI, 0C2) for each of the first and second rectifier switches (Sri, Sr2), for overriding the control signal from the control system when the measured voltage over the opposite rectifier switch (Sri, Sr2) is below a predetermined threshold value Vref.
    2. System according to claim 1, characterized in that the override circuit comprises a first input terminal receiving the control signal from the control system, a second input terminal receiving an override signal from the comparator circuit, and an output terminal connected to a gate terminal of the rectifier switch either directly or by means of a gate driver circuit.
    3. System according to claim 1, characterized in that the rectifier switch is turned OFF when overridden by the protection system.
    4. System according to claim 1, characterized in that the override circuit for the first rectifier switch (Sri) receives an override signal when the voltage over the second rectifier switch (Sr2) is below the predetermined threshold value Vref and that the override circuit for the second rectifier switch (Sr2) receives an override signal when the voltage over the first rectifier switch (Sri) is below the predetermined threshold value Vref.
    5. System according to claim 1, characterized in that the override circuits (OCI, 0C2) comprise a logic AND circuit element.
    6. System according to claim 1, characterized in that the override circuits (OC1, 0C2) comprise a diode connected with its anode to a gate driver circuit for the.
    second rectifier switch (Sr2) and to the control signal for the second rectifier switch (Sr2) and with its cathode to the output of the comparator circuit.
    7. System according to claim 1, characterized in that the converter is a LLC series resonant converter with synchronous rectification.
GB0724431A 2007-12-14 2007-12-14 Protection system for a resonant converter with synchronous rectification Withdrawn GB2455568A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB0724431A GB2455568A (en) 2007-12-14 2007-12-14 Protection system for a resonant converter with synchronous rectification
PCT/NO2008/000416 WO2009078728A1 (en) 2007-12-14 2008-11-21 Protection system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0724431A GB2455568A (en) 2007-12-14 2007-12-14 Protection system for a resonant converter with synchronous rectification

Publications (2)

Publication Number Publication Date
GB0724431D0 GB0724431D0 (en) 2008-01-30
GB2455568A true GB2455568A (en) 2009-06-17

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GB0724431A Withdrawn GB2455568A (en) 2007-12-14 2007-12-14 Protection system for a resonant converter with synchronous rectification

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GB (1) GB2455568A (en)
WO (1) WO2009078728A1 (en)

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GB2501108A (en) * 2012-04-12 2013-10-16 Eltek As DC-DC converter having shutdown device
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CN102497104A (en) * 2011-11-30 2012-06-13 深圳市理邦精密仪器股份有限公司 Resonant transformation circuit applied to medical equipment and provided with synchronous rectification control
GB2501108A (en) * 2012-04-12 2013-10-16 Eltek As DC-DC converter having shutdown device
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Publication number Publication date
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GB0724431D0 (en) 2008-01-30

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