KR102294315B1 - Power supply including llc converter and protection method for the same - Google Patents

Abstract

The present embodiment provides an LLC converter for outputting an input voltage as a preset output voltage according to a first switching signal and a second switching signal, a current sensing unit for sensing a resonant inductor current flowing through the LLC converter, and a resonant inductor current; An object of the present invention is to provide a power supply device including a protection circuit for outputting a protection signal for stopping an operation of an LLC converter in response to a phase difference between a first switching signal or a second switching signal, and a method for protecting the same.

Description

POWER SUPPLY INCLUDING LLC CONVERTER AND PROTECTION METHOD FOR THE SAME

The present invention relates to a power supply including an LLC converter and a method for protecting the same.

Switched mode power supplies are used in a wide range of electronic equipment. In particular, LLC converters are widely used because of their high efficiency and simple structure. The LLC converter may design a resonance tank stage based on the gain curve as shown in FIG. 1 using Fundamental Harmonic Approximation (FHA). At this time, the LLC converter can operate in the ZVS (Zero Voltage shutdown) region or ZCS (Zero Voltage shutdown) region depending on the impedance of the resonance tank stage. It is common to make it work in the realm.

As a method of blocking the entry into the ZCS region in order to operate only in the ZVS region as described above, the minimum frequency and input voltage can be set so that a design margin sufficient for the gain predicted by the FHA can be set. However, the margin may be set to be larger than an actual required margin due to an error of the FHA, so that the efficiency of the LLC converter may be lowered.

Korean Patent Publication KR 2012-0106511 (published on September 29, 2012)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply device including an LLC converter that operates stably with high efficiency and a method for protecting the same.

A first embodiment of the present invention provides an LLC converter for outputting an input voltage as a preset output voltage according to a first switching signal and a second switching signal, a current sensing unit for sensing a resonance inductor current flowing through the LLC converter, and a resonance inductor An object of the present invention is to provide a power supply device including a protection circuit for outputting a protection signal for stopping an operation of an LLC converter in response to a current and a phase difference between a first switching signal or a second switching signal.

A second aspect of the present invention is to provide a protection method for a power supply device including an LLC converter generating a predetermined voltage by receiving a first switching signal and a second switching signal, the protection method comprising the resonance of the LLC converter The steps of detecting the inductor current, determining the phase difference between the resonance inductor current and the first switching signal or the second switching signal, and outputting a protection signal if the phase difference is less than or equal to a preset value to stop the operation of the LLC converter may include

According to the power supply device including the LLC converter and the protection method thereof according to the present invention, the power supply device can be designed to be optimized for efficiency, thereby reducing switching loss and increasing efficiency. In addition, the device can be protected so that it can be operated stably.

1 is a graph showing a gain curve of an LLC resonant tank.
2 is a structural diagram showing the structure of a power supply device including an LLC converter using a phase according to the present invention.
3 is a circuit diagram illustrating an embodiment of the LLC resonant converter shown in FIG. 2 .
4 is a structural diagram showing a first embodiment of the protection circuit shown in FIG.
FIG. 5 is a timing diagram illustrating an operation of the protection circuit shown in FIG. 4 .
6 is a structural diagram showing a second embodiment of the protection circuit shown in FIG.
FIG. 7 is a timing diagram illustrating an operation of the protection circuit shown in FIG. 6 .
8 is a flowchart illustrating a protection operation in the LLC converter shown in FIG. 2 .

The control device according to the present invention and the operational effect including the technical configuration for the above purpose of the power supply device using the same will be clearly understood by the following detailed description with reference to the drawings in which a preferred embodiment of the present invention is shown.

In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In this specification, terms such as first, second, etc. are used to distinguish one component from another component, and the component is not limited by the terms.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0023] Reference is made to the accompanying drawings, which show by way of illustration specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein with respect to one embodiment may be embodied in other embodiments without departing from the spirit and scope of the invention. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the following detailed description is not intended to be taken in a limiting sense, and the scope of the present invention, if properly described, is limited only by the appended claims, along with all scope equivalents to those claimed. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to enable those of ordinary skill in the art to easily practice the present invention.

2 is a structural diagram showing a power supply device including an LLC converter according to the present invention.

Referring to FIG. 2 , the power supply 200 outputs an input voltage Vs as a preset output voltage based on a first switching signal Q1 and a second switching signal Q2. An LLC converter 210, an LLC converter In response to the current sensing unit 220 sensing the resonance inductor current Ir flowing through 210, and the phase difference between the resonance inductor current Ir and the first switching signal Q1 or the second switching signal Q2 A protection circuit 230 for outputting a protection signal for stopping the operation of the LLC converter 210 may be included.

The LLC converter 210 receives the first switching signal Q1 and the second switching signal Q2, converts the flow of current flowing by the input voltage, and converts the input voltage Vs to a preset output voltage by the generated electromotive force. (Vo) can be output. In this case, the output voltage Vo may be fed back so that the output voltage Vo may be constant. In addition, the LLC converter 210 may be operated by setting the switching frequencies of the first switching signal Q1 and the second switching signal Q2 to operate in the ZVS region shown in FIG. 1 .

The current sensing unit 220 may sense the resonance inductor current Ir flowing through the LLC converter 210 by the first switching signal Q1 and the second switching signal Q2 . The power supply 200 may allow the LLC converter 210 to operate in the ZVS region using the resonance inductor current Ir. The current sensing unit 220 senses the resonant inductor current Ir through a voltage applied to the sensing resistor connected to the LLC converter 210 or uses an auxiliary winding to correspond to the resonant inductor current Ir. By measuring the resonant inductor current (Ir) can be detected. However, the configuration of the current sensing unit 220 is not limited thereto.

The protection circuit 230 may output a protection signal to prevent damage and/or efficiently drive the LLC converter 210 . The protection circuit 230 uses the phase difference between the resonant inductor current Ir and the first switching signal Q1 or the resonant inductor current Ir and the second switching signal Q2 so that the LLC converter 210 operates in the ZVS region or ZCS region. You can check whether it is operating in the area or not. As shown in FIG. 1 , the LLC converter 210 operates in the ZCS region when the switching frequency is lower than the frequency at the maximum gain, and operates in the ZVS region when the switching frequency is higher than the frequency at the maximum gain. Also, the LLC converter 210 may have lower efficiency at the maximum gain. Therefore, when the protection circuit 230 operates at the maximum gain by using the phase difference between the resonance inductor current Ir and the first switching signal Q1 or the second switching signal Q2, it outputs a protection signal and outputs a protection signal to the LLC converter 210 ) can be stopped. Also, if there is no phase difference between the resonant inductor current Ir and the first switching signal Q1 or the second switching signal Q2, it may be determined that the protection circuit 230 operates at the maximum gain.

3 is a structural diagram showing the structure of a power supply device including an LLC converter using a phase according to the present invention.

Referring to FIG. 3 , the LLC converter 210 may include a power conversion unit 211 , a resonance tank 212 , a transformer 213 , and a rectifying unit 214 . In addition, the rectifier 214 may be connected to the output capacitor Co to transmit the output voltage Vo from the rectifier 214 to the load.

The power converter 211 may include a first switching element SW1 and a second switching element SW2 that can be alternately turned on by receiving the first switching signal Q1 and the second switching signal Q2. can The first switching element SW1 and the second switching element SW2 may be a field effect transistor (FET), a metal oxide silicon field effect transistor (MOSFET), a bipolar junction transistor (BJT), or the like. However, the present invention is not limited thereto. The resonance tank 212 may include a first inductor Lr, a second inductor Llkg, a third inductor Lm, and a resonance capacitor Cr. The transformer 213 may include a primary winding 213a and a secondary winding 213b, and the electromotive force generated by the current transmitted to the primary winding 213a by the power converter 211 is The voltage may be transformed in the secondary winding 213b to output a preset voltage. In addition, the secondary winding 213b of the transformer 213 may include a first sub winding and a second sub winding, and the voltage induced in the secondary winding 213b is rectified by the rectifier 214 to obtain an output capacitor. (Co) can be forwarded. The rectifier 214 includes a first diode D1 and a second diode D2, and may perform full-wave rectification of a preset voltage output from the secondary winding 213b. However, the configuration of the rectifying unit 214 is not limited thereto.

In addition, the current sensing unit 220 is connected to the first node N1 of the LLC converter 210 to receive the resonant inductor current Ir from the current sensing unit 220 . Also, the current sensing unit 220 may receive the resonance inductor current Ir through an auxiliary winding wound around the third inductor Lm. However, the connection of the current sensing unit 220 is not limited thereto. In addition, the resonance inductor current Ir may be a current that is induced in the third inductor Lm and flows.

In addition, the LLC converter 210 includes a control unit 215 , and the control unit 215 generates a first switching signal Q1 and a second switching signal Q2 to generate a first switching element of the power conversion unit 211 . It can be transmitted to (SW1) and the second switching element (SW2). Also, the controller 215 may receive the driving voltage Vcc and start driving when the enable signal is transmitted. And, the protection signal shown in FIG. 2 prevents the driving voltage from being transmitted to the control unit 215 or prevents the enable signal from being transmitted so that the control unit 215 does not operate. operation can be stopped.

4 is a structural diagram showing a first embodiment of the protection circuit shown in FIG. 2, and FIG. 5 is a timing diagram showing the operation of the protection circuit shown in FIG.

4 and 5 , the protection circuit 230a may include a first comparator 231a and an AND gate 232a. In the first comparator, a negative (-) input terminal may receive a resonance voltage corresponding to the resonance inductor current Ir sensed by the current sensing unit 220 , and a positive (+) input terminal may be connected to the ground. In addition, the output of the first comparator 231a and the first switching signal Q1 may be respectively input to the AND gate 232a.

In addition, the negative (-) input terminal of the first comparator 231a receives the resonance voltage Vir from the current sensing unit 220, and the first comparator 231a has a resonance because the positive (+) input terminal is connected to the ground. When the voltage Vir has a negative value, a high signal can be output, and when the voltage Vir has a positive value, a low signal can be output. And, the output terminal of the first comparator 231a and the first switching signal Q1 are ANDed by the AND gate 232a, so that the output signal of the first comparator 231a and the first switching signal Q1 are high. A high signal can be output only in this case. Therefore, as shown in FIG. 5 , the phase of the resonance voltage Vir is later than the phase of the first switching signal Q1, and the first switching signal Q1 is in a high state while the magnitude of the resonance voltage Vir is negative. , the AND gate 232a may output a high signal. In this case, the signal output from the AND gate 232a may be output as a low signal when the resonance voltage Vir is changed from negative to positive. Accordingly, the protection circuit 230a may determine the phase difference between the first switching signal Q1 and the resonance voltage Vir through the width of the pulse generated by maintaining the high state of the signal output from the AND gate 232a. . If there is no phase difference between the first switching signal Q1 and the resonance voltage Vir, the signal output from the AND gate 232a is not output to the high state, and thus only the low state may be maintained. Accordingly, when the signal output from the AND gate 232a is output in a low state, it may be determined that there is no phase difference between the first switching signal Q1 and the resonance voltage Vir. Accordingly, the protection circuit 230a may determine a phase difference between the first switching signal Q1 and the resonance voltage Vir using the signal output from the AND gate 232a, and if there is no phase difference, output the protection signal.

In addition, the protection circuit 230a may include a level converter 233a and a second comparator 234a. The output of the AND gate 232a is transferred to the level converter 233a, the output of the level converter 233a is transferred to the negative (-) input terminal of the second comparator 234a, and the reference voltage Vref is transferred to the second comparator 234a. ) can be transmitted to the positive (+) input terminal. The protection circuit 230a may convert the pulse output from the AND gate 232a into a voltage in the level converter 233a and compare it with the reference voltage Vref in the second comparator 234a. In addition, the protection circuit 230a may output a protection signal when the voltage output from the level converter 233a is smaller than the reference voltage Vref of the second comparator 234a. Accordingly, the protection circuit 230a may output the protection signal when the phase difference between the first switching signal Q1 and the resonance voltage Vir is smaller than a preset level even though there is a phase difference between the first switching signal Q1 and the resonance voltage Vir. The level converter 233a may output a pulse output from the AND gate 232a as a predetermined voltage using an RC filter.

Also, since the signal output from the AND gate 232a is generated only when both the first switching signal Q1 and the output signal of the first comparator 231a are high, a pulse may be generated for a very short time. When the pulse is generated only for such a short time, the protection signal is output for most of the time, and there is a fear that the operation time of the LLC converter 210 becomes very short. Accordingly, the above problem can be solved by allowing the protection circuit 230a to operate only when the signal output from the AND gate 232a maintains the low signal for a predetermined time or longer using a timer or the like. In addition, if the protection circuit 230a operates only in a section to which the first switching signal Q1 is input, the above problem can be solved. However, the present invention is not limited thereto.

Here, it has been described that the resonance voltage Vir is transmitted to the negative (-) input terminal of the first comparator 231a and the first switching signal Q1 is transmitted to the AND gate 232a, but the present invention is not limited thereto. Even if the resonance voltage Vir is transmitted to the positive (+) input terminal of the comparator 231a and the second switching signal Q2 is transmitted to the AND gate 232a, the phase difference can be detected.

6 is a structural diagram showing a second embodiment of the protection circuit shown in FIG. 2 , and FIG. 7 is a timing diagram showing the operation of the protection circuit shown in FIG. 5 .

6 and 7 , the protection circuit 230b may include a first comparator 231b and an AND gate 232b. The first comparator 231b may have a positive (+) input terminal receive a resonance voltage Vir corresponding to the resonance inductor current Ir sensed by the current sensing unit 220 , and a negative (+) input terminal may be connected to the ground. . In addition, the output of the first comparator 231b and the second switching signal Q2 may be input to the AND gate 232b, respectively.

In addition, the negative (-) input terminal of the first comparator 231b receives the resonance voltage Vir from the current sensing unit 220, and the first comparator 231b has a negative (-) input terminal connected to the ground, thereby resonating. When the voltage Vir has a positive value, a high signal can be output, and when the voltage Vir has a negative value, a low signal can be output.

Then, the output terminal of the first comparator 231b and the second switching signal Q2 are ANDed by the AND gate 232b, so that the output signal of the first comparator 231b and the second switching signal Q2 are high. A high signal can be output only in this case. Therefore, as shown in FIG. 7 , when the phase of the resonance voltage Vir is later than the phase of the second switching signal Q2 and the second switching signal Q2 becomes high, the resonance voltage Vir continues to be positive. can have a value of Also, when the second switching signal Q2 is maintained high for a predetermined time, the resonance voltage Vir may be switched from positive to negative. Accordingly, the AND gate 232b may output a high signal in a section until the second switching signal Q2 is in a high state and the resonance voltage Vir is converted to a negative state. Accordingly, the phase difference between the second switching signal Q2 and the resonance voltage Vir may be determined based on the pulse width generated by maintaining the high state of the signal output from the AND gate 232b. If there is no phase difference between the second switching signal Q2 and the resonance voltage, the signal output from the AND gate 232b is not output to the high state, and thus only the low state may be maintained. Accordingly, when the low state is output, it may be determined that there is no phase difference between the second switching signal Q2 and the resonance voltage Vir. Accordingly, the protection circuit 230b may determine a phase difference using the signal output from the AND gate 232b and output the protection signal if there is no phase difference.

In addition, the protection circuit 230b may further include a duty detector 233b. The output of the first andgate 232b is transmitted to the duty detector 233b, and the duty detector 233b detects a pulse corresponding to the output of the first andgate 232b and protects it if the width of the pulse is less than or equal to a preset width signal can be output. The protection circuit 230b may output a protection signal when the width of the pulse detected by the duty detector 233b is smaller than the preset pulse width. Accordingly, the protection circuit 230b may output the protection signal when the phase difference is smaller than a preset magnitude.

In addition, since the signal output from the AND gate 232b is generated only when both the second switching signal Q2 and the output signal of the first comparator 231b are high, a pulse may be generated for a very short time. When the pulse is generated only for such a short time, the protection signal is output for most of the time, and there is a fear that the operation time of the LLC converter 210 becomes very short. Accordingly, the above problem can be solved by allowing the protection circuit 230b to operate only when the signal output from the AND gate 232b maintains a low signal for a predetermined time or longer using a timer or the like. In addition, the protection circuit 230b operates only in a section to which the second switching signal Q2 is input, thereby solving the above problem. However, the present invention is not limited thereto.

Here, it has been described that the resonance voltage Vir is transmitted to the positive (+) input terminal of the first comparator 231b and the second switching signal Q2 is transmitted to the AND gate 232b, but the present invention is not limited thereto. Even if the resonance voltage Vir is transmitted to the negative (-) input terminal of the comparator 231b and the first switching signal Q1 is transmitted to the AND gate 232b, the phase difference can be detected.

8 is a flowchart illustrating a protection operation in the power supply including the LLC converter shown in FIG. 2 .

Referring to FIG. 8 , the power supply 200 may sense the resonant inductor current Ir of the LLC converter 210 ( S800 ). The resonant inductor current Ir is sensed by the current sensing unit 220 . In this case, the current sensing unit 220 may output a resonance voltage Vir corresponding to the sensed resonance inductor current Ir.

In addition, the power supply 200 may determine a phase difference between the resonance inductor current Ir and the first switching signal Q1 or the second switching signal Q2 ( S810 ). The resonance voltage Vir is the resonance inductor current. It can correspond to (Ir), so it can have the same phase as the resonance inductor current (Ir). In addition, the phase difference may be determined by comparing the timing when the resonance voltage Vir corresponding to the magnitude of the resonance inductor current Ir becomes a predetermined value and the turn-on timing of the first switching signal or the second switching signal. In addition, the phase difference may be determined by comparing the time when the resonance voltage Vir changes from a negative value to a positive value with the turn-on time of the first switching signal Q1, and the resonance voltage Vir changes from a positive value to a positive value. The phase difference may be determined by comparing a time point at which a negative value is changed with a time point at which the second switching signal Q2 is turned on.

And, when the phase difference between the resonance inductor current Ir and the first switching signal Q1 or the second switching signal Q2 is less than a preset value, the power supply 200 outputs a protection signal to operate the LLC converter 210 . (S820) The protection signal may be output from the protection circuit 230. The phase difference may be determined by using the magnitude of a voltage corresponding to the phase difference or a pulse width corresponding to the phase difference in the protection circuit 230 .

The functions of the various elements shown in the drawings of the present invention may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, such functionality may be provided by a single dedicated processor, a single shared processor, or a plurality of separate processors, some of which may be shared.

In the claims of this specification, an element expressed as a means for performing a particular function encompasses any manner of performing the particular function, and such an element is a combination of circuit elements that perform the particular function, or a method for performing the particular function. It may include any form of software, including firmware, microcode, and the like, combined with suitable circuitry to implement the software for the purpose.

References herein to 'one embodiment' of the principles of the invention, etc., and various variations of such expressions, in connection with this embodiment, indicate that a particular feature, structure, characteristic, etc., is included in at least one embodiment of the principles of the present invention. it means.

In the present specification, references to various modifications of these expressions, such as 'connected' or 'connecting', are used in the meaning of including being directly connected to another element or indirectly connected through another element. Also, in this specification, the singular includes the plural unless specifically stated otherwise in the text. Also, as used herein, a component, step, operation, and element referred to as 'comprising' or 'comprising' refers to the presence or addition of one or more other components, steps, operations, elements, and devices.

200: power supply 210: LLC converter
220: current sensing unit 230: protection circuit
Q1: first switching signal Q2: second switching signal
Ir: resonant inductor current

Claims (13)

an LLC converter for outputting an input voltage as a preset output voltage according to the first switching signal and the second switching signal;
a current sensing unit for sensing a resonant inductor current flowing through the LLC converter; and
When the phase difference between the resonant inductor current and the first switching signal is less than or equal to a preset value or the phase difference between the resonance inductor current and the second switching signal is less than or equal to a preset value, protection for outputting a protection signal to stop the operation of the LLC converter A power supply containing a circuit. According to claim 1,
The protection circuit is
The phase difference is determined by comparing a time point at which a first voltage corresponding to the magnitude of the resonant inductor current sensed by the current sensing unit becomes a predetermined value and a time point at which the first switching signal or the second switching signal is turned on. . delete 3. The method of claim 2,
The protection circuit generates a pulse corresponding to the phase difference, and when a second voltage corresponding to the pulse is lower than a predetermined voltage, the power supply device determines that the phase difference is equal to or less than the preset value. 5. The method of claim 4,
The protection circuit is
a first comparator that compares the magnitude of the resonance inductor current with a first reference voltage and outputs a high signal when the magnitude of the resonance inductor current is smaller than the first reference voltage; a phase detection unit generating the pulse by calculating the first switching signal or the second switching signal;
the second voltage in response to the pulse
A power supply device comprising: a protection signal driver including a level converter generating the level converter; 3. The method of claim 2,
The protection circuit generates a pulse corresponding to the phase difference, and if the width of the pulse is shorter than a predetermined pulse width, the power supply device determines that the phase difference is equal to or less than the preset value. 7. The method of claim 6,
The protection circuit is
a first comparator that compares the magnitude of the resonance inductor current with a first reference voltage and outputs a high signal when the magnitude of the resonance inductor current is smaller than the first reference voltage; a phase detection unit generating the pulse by calculating the first switching signal or the second switching signal;
and a protection signal driver including a duty detection unit that determines the width of the pulse and outputs the protection signal when the width of the pulse is less than or equal to a predetermined value. 3. The method of claim 2,
The protection circuit is
A time point at which the first voltage changes from negative to positive based on the predetermined value is compared with a turn-on time point of the first switching signal, and a time point at which the first voltage changes from positive to negative based on the predetermined value; A power supply for comparing turn-on times of the second switching signal. According to claim 1,
The LLC converter further includes a control unit for outputting the first switching signal and the second switching signal, and the protection signal is transmitted to the control unit to stop driving of the control unit. According to claim 1,
The LLC converter further includes a control unit for outputting the first switching signal and the second switching signal, wherein the protection signal prevents the control unit from outputting the first switching signal and the second switching signal. A method of protecting a power supply device comprising an LLC converter generating a predetermined voltage by receiving a first switching signal and a second switching signal, the method comprising:
sensing a resonant inductor current of the LLC converter;
determining a phase difference between the resonant inductor current and the first switching signal or a phase difference between the resonant inductor current and the second switching signal; and
If the phase difference between the resonant inductor current and the first switching signal is less than or equal to a preset value or the phase difference between the resonance inductor current and the second switching signal is less than or equal to a preset value, outputting a protection signal to stop the operation of the LLC converter A method of protecting a power supply comprising a. 12. The method of claim 11,
When the resonance voltage corresponding to the magnitude of the resonance inductor current changes from negative to positive, the phase difference is the phase difference between the resonance inductor current and the first switching signal. The phase difference is a phase difference between the resonant inductor current and the second switching signal. 12. The method of claim 11,
The determining of the phase difference may include determining a voltage corresponding to the phase difference or a pulse width corresponding to the phase difference.

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