TWI784865B - Resonant converter - Google Patents

Abstract

A resonant converter is provided. The resonant converter includes a transformer, a resonant circuit, a coupling circuit and a rectifier. The transformer includes a primary side winding and a secondary side winding. The resonant circuit is coupled to the primary side winding. The coupling circuit includes an excitation inductor. The excitation inductor is coupled in parallel to the secondary side winding. The excitation inductor couples energy of the secondary side winding to provide a sensing voltage. The rectifier rectifies the sensing voltage to generate an output power. The coupling circuit provides discharging loops to consume energy stored in the excitation inductor. Formations of the discharging loops are related to switching sequences of various power switches.

Description

resonant converter

The invention relates to a resonant converter, in particular to a resonant converter capable of reducing resonance energy oscillation.

Existing power supply devices can perform voltage switching operations through resonant converters to convert electrical energy. Generally speaking, when the electrical power required by the load device (for example, a computer for gaming) is large, the magnetizing inductor in the resonant converter is designed to have a large inductance value. However, a magnetizing inductor with a larger inductance value also generates larger resonance energy during voltage switching operation, making the resonant converter unstable.

An embodiment of the present invention provides a resonant converter capable of reducing resonance energy oscillations.

The resonant converter in the embodiment of the present invention includes a transformer, a first power switch, a second power switch, a resonant circuit, a coupling circuit and a rectifier. A transformer includes a primary side winding as well as a secondary side winding. The first power switch is coupled between the input power and the connection node. The second power switch is coupled between the connection node and the first ground terminal. The resonant circuit is coupled between the connection node and the primary winding. The coupling circuit includes a magnetizing inductor. The magnetizing inductor is coupled in parallel with the secondary winding. The magnetizing inductor couples the energy from the secondary winding to provide an induced voltage. The rectifier is coupled to the coupling circuit. The rectifier rectifies the induced voltage to generate output power. The coupling circuit provides multiple discharge circuits to dissipate the energy stored in the magnetizing inductor. The formation of the plurality of discharge loops is respectively associated with switching timings of the first power switch and the second power switch.

Based on the above, the magnetizing inductor of the resonant converter of the embodiment of the present invention is coupled in parallel to the secondary winding. Resonant energy can be coupled through the magnetizing inductor. In addition, the resonance energy of the magnetizing inductor can be moderately dissipated via multiple discharge loops to stabilize the resonant converter.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

Parts of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. For the referenced reference symbols in the following description, when the same reference symbols appear in different drawings, they will be regarded as the same or similar components. These embodiments are only a part of the present invention, and do not reveal all possible implementation modes of the present invention. Rather, these embodiments are only examples within the scope of the patent application of the present invention.

Please refer to FIG. 1 , which is a block diagram of a resonant converter according to an embodiment of the present invention. In this embodiment, the resonant converter 100 includes a transformer 110 , power switches Q1 - Q2 , a resonant circuit 120 , a coupling circuit 130 and a rectifier 140 . The transformer 110 includes a primary winding NP and a secondary winding NS. The power switch Q1 is coupled between the input power VIN and the connection node ND. The power switch Q2 is coupled between the connection node ND and the ground terminal GND. The resonant circuit 120 is coupled between the connection node ND and the primary winding NP.

In this embodiment, the coupling circuit 130 includes a magnetizing inductor LM. The magnetizing inductor LM is coupled in parallel to the secondary winding NS. The magnetizing inductor LM couples the energy of the secondary winding NS to provide an induced voltage VS. The rectifier 140 is coupled to the coupling circuit 130 . The rectifier 140 rectifies the induced voltage VS to generate an output power VO.

It should be noted that the magnetizing inductor LM is coupled in parallel to the secondary winding NS, but not to the primary winding NP. The energy of the secondary side winding NS can be efficiently coupled and converted into the output power supply VO. Therefore, the performance of the resonant converter 100 can be improved.

In this embodiment, the coupling circuit 130 provides discharge circuits LP1 and LP2 to properly consume the energy stored in the magnetizing inductor LM. The formation of the discharge loops LP1 and LP2 is related to the switching timing of the power switch Q1 and the power switch Q2 respectively. That is, in response to the power switches Q1 , Q2 being turned on or turned off, the discharge loops LP1 , LP2 are not formed at the same time.

It is worth mentioning here that even if the inductance of the magnetizing inductor LM is designed to be large, the energy coupled to the magnetizing inductor LM can be moderately consumed through multiple discharge circuits. Therefore, resonance energy oscillations caused by the magnetizing inductor LM can be reduced to stabilize the resonant converter 100 .

In this embodiment, the power switches Q1 and Q2 are respectively implemented with transistors. Specifically, the first end of the power switch Q1 is coupled to the input power VIN. The second end of the power switch Q1 is coupled to the connection node ND. The control terminal of the power switch Q1 receives the control signal GD1. The power switch Q1 performs a switching operation in response to the control signal GD1. The first end of the power switch Q2 is coupled to the connection node ND. The second terminal of the power switch Q2 is coupled to the ground terminal GND. The control terminal of the power switch Q2 receives the control signal GD2. The power switch Q2 performs a switching operation in response to the control signal GD2. The control signal GD1 is opposite to the control signal GD2.

In this embodiment, when the power switch Q1 is turned on, the coupling circuit 130 provides a discharge loop LP1 to consume the energy stored in the magnetizing inductor LM. On the other hand, when the power switch Q2 is turned on, the coupling circuit 130 provides a discharge loop LP2 to consume the energy stored in the magnetizing inductor LM. The numbers of the discharge loops LP1 and LP2 in this embodiment are just examples.

It should be noted that when the power switch Q1 is turned on, the power switch Q2 is turned off under the control of the reverse direction of the control signal GD1 (ie, the control signal GD2 ). At this time, the discharge loop LP1 is formed, and the discharge loop LP2 is not formed. On the other hand, when the power switch Q2 is turned on, the power switch Q1 is turned off. At this time, the discharge loop LP2 is formed, and the discharge loop LP1 is not formed. The discharge circuits LP1 and LP2 are formed alternately, and alternately reduce the energy stored in the exciting inductor LM. The resonance energy generated by the exciting inductor LM at the time of voltage switching operation is reduced. In the resonant converter 100 , there will be no resonant energy oscillation caused by excessive resonant energy. In this way, the operation of the resonant converter 100 can be more stable.

Please refer to FIG. 2 , which is a circuit diagram of a resonant converter according to another embodiment of the present invention. In this embodiment, the resonant converter 200 includes a transformer 210 , power switches Q1 , Q2 , a resonant circuit 220 , a coupling circuit 230 and a rectifier 240 . In this embodiment, the resonant converter 200 is implemented as an LLC resonant converter. Specifically, the resonant circuit 220 includes a resonant capacitor CR and a resonant inductor LR. The first end of the resonant capacitor CR is coupled to the connection node ND. The second end of the resonant capacitor CR is coupled to the first end of the resonant inductor LR. The second terminal of the resonant inductor LR is coupled to the first terminal of the primary winding NP. The second terminal of the primary winding NP and the second terminal of the power switch Q2 are coupled to the ground terminal GND1.

In this embodiment, the rectifier 240 includes a bridge circuit 241 and an output capacitor CO. The bridge circuit 241 is coupled in parallel to the output capacitor CO. The bridge circuit 241 rectifies the induced voltage VS according to the control signals GD1 and GD2 . The output capacitor CO outputs the output power VO according to the rectified induced voltage VS.

Specifically, in this embodiment, the bridge circuit 241 includes rectification switches Q3, Q4 and rectification diodes D1, D2. The first end of the output capacitor CO is coupled to the first end of the rectifier switch Q3. The first terminal of the output capacitor CO and the first terminal of the rectifier switch Q3 serve as the output terminal of the rectifier 240 . The second terminal of the output capacitor CO is coupled to the ground terminal GND2. The second end of the rectifier switch Q3 is coupled to the first end of the magnetizing inductor LM. The control terminal of the rectifier switch Q3 receives the control signal GD1. The anode of the rectifying diode D1 is coupled to the second end of the magnetizing inductor LM. The cathode of the rectifier diode D1 is coupled to the first terminal of the rectifier switch Q3. The first end of the rectification switch Q4 is coupled to the second end of the rectification switch Q3. The second terminal of the rectifier switch Q4 is coupled to the ground terminal GND2. The control terminal of the rectifier switch Q4 receives the control signal GD2. The anode of the rectifier diode D2 is coupled to the ground terminal GND2. The cathode of the rectifying diode D2 is coupled to the second end of the magnetizing inductor LM. In other implementations, the rectifier switches Q3 and Q4 may be implemented as diodes.

It should be noted that the bridge circuit 241 rectifies the voltage by means of bridge rectification instead of center-tapped rectification. That is, the rectifier switch Q3 and the rectifier diode D2 are in the first group, and the rectifier switch Q4 and the rectifier diode D1 are in the second group. The first group and the second group are respectively turned on alternately in response to the control signals GD1 and GD2 for rectification.

In this embodiment, the coupling circuit 230 further includes an inductor LX1, a discharge capacitor C1, and an auxiliary switch QX1. The inductor LX1 is inductively coupled to the magnetizing inductor LM. The inductor LX1 couples the energy stored in the magnetizing inductor LM according to the control signal GD1 to provide the first power consumption. A first end of the discharge capacitor C1 is coupled to a first end of the inductor LX1. The second end of the discharge capacitor C1 is coupled to the first end of the auxiliary switch QX1. The second end of the auxiliary switch QX1 is coupled to the second end of the inductor LX1. The control terminal of the auxiliary switch QX1 receives the control signal GD1. The auxiliary switch QX1 performs switching operations according to the control signal GD1.

In this embodiment, when the auxiliary switch QX1 is turned on in response to the control signal GD1 , the inductor LX1 and the discharge capacitor C1 together form a discharge loop (the discharge loop LP1 shown in FIG. 1 ). At this time, the inductor LX1 charges the discharge capacitor C1 with the first power consumption. In other words, the discharge capacitor C1 absorbs the first power consumption of the inductor LX1. Therefore, when the control signal GD1 is at a high voltage level, the first power consumption of the inductor LX1 is consumed, and then the energy stored in the exciting inductor LM is moderately reduced through coupling.

In this embodiment, the coupling circuit 230 further includes an inductor LX2, a discharging capacitor C2, and an auxiliary switch QX2. The inductor LX2 is inductively coupled to the magnetizing inductor LM. The inductor LX2 couples the energy stored in the magnetizing inductor LM according to the control signal GD2 to provide the second power consumption. A first end of the discharge capacitor C2 is coupled to a first end of the inductor LX2. The second end of the discharge capacitor C2 is coupled to the first end of the auxiliary switch QX2. The second end of the auxiliary switch QX2 is coupled to the second end of the inductor LX2. The control terminal of the auxiliary switch QX2 receives the control signal GD2. The auxiliary switch QX2 performs switching operations according to the control signal GD2.

In this embodiment, when the auxiliary switch QX2 is turned on in response to the control signal GD2 , the inductor LX2 and the discharge capacitor C2 jointly form a discharge loop (the discharge loop LP2 shown in FIG. 1 ). At this time, the inductor LX2 charges the discharge capacitor C2 with the second power consumption. In other words, the discharging capacitor C2 will absorb the second power consumption of the inductor LX2. Therefore, when the control signal GD2 is at a high voltage level, the second power consumption of the inductor LX2 is consumed, and then the energy stored in the exciting inductor LM is moderately reduced through coupling.

In this embodiment, the exciting inductor LM and the inductors LX1 and LX2 may be different windings arranged in the same coupled inductor. In this way, the volume of the secondary side can be reduced.

Please refer to FIG. 2 , FIG. 3A and FIG. 3B at the same time. FIG. 3A and FIG. 3B are schematic diagrams of the operation of the resonant converter shown in FIG. 2 according to the embodiment of the present invention. In this embodiment, in FIGS. 3A and 3B , the horizontal axis represents the operating time of the resonant converter 200 , and the vertical axis represents the voltage value. FIG. 3A shows the control signal GD1 and the voltage signal VLX1 across the inductor LX1. On the other hand, FIG. 3B shows the control signal GD2 and the voltage signal VLX2 across the inductor LX2. In this embodiment, the voltage signal VLX1 is related to the first power consumption. The voltage signal VLX2 is related to the second power consumption.

In this embodiment, the power switches Q1, Q2 are controlled by the control signals GD1, GD2 to be turned on or turned off respectively. The switching operation states of the power switches Q1 and Q2 and the corresponding action states of the coupling circuit 230 and the rectifier 240 are shown in Table (1). Please refer to Figure 2, Figure 3A, Figure 3B and Table (1) together.

Table 1): Switching state of power switches Q1, Q2 coupling circuit 230 Rectifier 240 Discharge circuit LP1 Discharge circuit LP2 Rectifier switch Q3, rectifier diode D2 Rectifier switch Q4, rectifier diode D1 Q1 is turned on, Q2 is turned off was formed not formed turned on disconnected Q1 is turned off, Q2 is turned on not formed was formed disconnected turned on

In this embodiment, during the period from the time point 0T to the time point 0.5T, the control signal GD1 has a logic high level, as shown in FIG. 3A . Therefore, the power switch Q1 is turned on. The auxiliary switch QX1 is also turned on in response to the control signal GD1. A discharge loop LP1 is formed. During this period, the first power consumption provided by the inductor LX1 is consumed through the discharge loop LP1 , so that the voltage signal at both ends of the inductor LX1 presents a sinusoidal wave. At the same time, the rectifier switch Q3 is also turned on in response to the control signal GD1 , so the rectifier diode D2 is turned on.

During the period from the time point 0T to the time point 0.5T, the control signal GD2 has a logic low level, as shown in FIG. 3B . Therefore, the power switch Q2 is turned off. The auxiliary switch QX2 is also turned off in response to the control signal GD2. The discharge loop LP2 is not formed. Therefore, there is no voltage difference across the inductor LX2. At the same time, the rectifier switch Q4 is also turned off in response to the control signal GD2, so the rectifier diode D1 is turned off.

In this embodiment, during the period from the time point 0.5T to the time point 1T, the control signal GD1 has a logic low level, as shown in FIG. 3A . Therefore, the power switch Q1 is turned off. The auxiliary switch QX1 is also turned off in response to the control signal GD1. The discharge loop LP1 is not formed. Therefore, there is no voltage difference across the inductor LX1. At the same time, the rectifier switch Q3 is also turned off in response to the control signal GD1 , so the rectifier diode D2 is turned off.

During the period from the time point 0.5T to the time point 1T, the control signal GD2 has a logic high level, as shown in FIG. 3B . Therefore, the power switch Q2 is turned on. The auxiliary switch QX2 is also turned on in response to the control signal GD2. A discharge loop LP2 is formed. During this period, the second power consumption provided by the inductor LX2 is consumed through the discharge loop LP2 , so that the voltage signal at both ends of the inductor LX2 presents a sinusoidal wave. At the same time, the rectifier switch Q4 is also turned on in response to the control signal GD2 , so the rectifier diode D1 is turned on.

The configurations of the durations from the time point 0T to the time point 1T in the embodiments of FIGS. 3A to 3B are just examples.

It should be noted that the discharge loops LP1 and LP2 are alternately formed to dissipate the energy stored in the magnetizing inductor LM. At the same time, the rectifier switches Q3 and Q4 and the rectifier diodes D2 and D1 are turned on alternately to perform rectification in a complementary manner.

To sum up, the magnetizing inductor in the resonant converter of the embodiment of the present invention is coupled in parallel to the secondary winding, so that the performance of the resonant converter is improved. In addition, the resonant energy located in the magnetizing inductor can be dissipated via multiple discharge loops, so that the resonant energy oscillation is reduced to stabilize the resonant converter. In some embodiments, the bridge circuit and the plurality of discharge circuits alternately perform corresponding operations corresponding to the enabled periods of the first power switch and the second power switch.

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention should be defined by the scope of the appended patent application.

100, 200: resonant converter 110, 210: transformer 120, 220: resonant circuit 130, 230: coupling circuit 140, 240: rectifier 241: bridge circuit 0T, 0.5T, 1T: time point C1, C2: discharge capacitor CO: output capacitor CR: resonant capacitor D1, D2: Rectifier diodes GD1, GD2: control signal GND, GND1, GND2: ground terminal LM: Exciting inductor LP1, LP2: discharge circuit LR: Resonant inductor LX1, LX2: Inductor ND: connect node NP: Primary side winding NS: Secondary side winding Q1, Q2: Power switch Q3, Q4: rectifier switch QX1, QX2: Auxiliary switch VIN: input power VLX1, VLX2: voltage signal VO: output power VS: induced voltage

FIG. 1 is a block diagram of a resonant converter according to an embodiment of the invention. FIG. 2 is a circuit diagram of a resonant converter according to another embodiment of the invention. FIG. 3A and FIG. 3B are schematic diagrams of the operation of the resonant converter shown in the embodiment shown in FIG. 2 according to the present invention.

100: Resonant Converter

110: Transformer

120: Resonant circuit

130:Coupling circuit

140: rectifier

GD1, GD2: control signal

GND: ground terminal

LM: Exciting inductor

LP1, LP2: discharge circuit

ND: connect node

NP: Primary side winding

NS: Secondary side winding

Q1, Q2: Power switch

VIN: input power

VO: output power

VS: induced voltage

Claims (10)

A resonant converter comprising: A transformer, including a primary side winding and a secondary side winding; a first power switch, coupled between an input power source and a connection node; a second power switch coupled between the connection node and a first ground terminal; a resonant circuit coupled between the connection node and the primary side winding; a coupling circuit comprising a magnetizing inductor, wherein the magnetizing inductor is coupled in parallel to the secondary side winding, the magnetizing inductor being configured to couple energy of the secondary side winding to provide an induced voltage; and a rectifier, coupled to the coupling circuit, configured to rectify the induced voltage to generate an output power, The coupling circuit provides a plurality of discharge loops to consume the energy stored in the magnetizing inductor, wherein the formation of the discharge loops is respectively related to the switching timing of the first power switch and the second power switch. The resonant converter as claimed in item 1, wherein the first power switch performs a first switching operation in response to a first control signal, and wherein the second power switch performs a second switching operation in response to a second control signal Switching operation, wherein the second control signal is opposite to the first control signal. The resonant converter as claimed in item 2, wherein the discharge circuits include a first discharge circuit and a second discharge circuit, wherein when the first power switch is turned on, the coupling circuit provides the first discharge circuit to consume The energy stored in the magnetizing inductor. The resonant converter as claimed in claim 3, wherein when the second power switch is turned on, the coupling circuit provides the second discharge circuit to consume the energy stored in the magnetizing inductor. The resonant converter as claimed in claim 2, wherein the rectifier comprises: A bridge circuit configured to rectify the induced voltage according to the first control signal and the second control signal. The resonant converter as claimed in item 5, wherein the bridge circuit comprises: A first rectification switch, the first end of the first rectification switch is used as the output end of the rectifier, the second end of the first rectification switch is coupled to the first end of the exciting inductor, the control of the first rectification switch receiving the first control signal at the terminal; a first rectifier diode, the anode of the first rectifier diode is coupled to the second end of the magnetizing inductor, and the cathode of the first rectifier diode is coupled to the first end of the first rectifier switch ; A second rectifier switch, the first terminal of the second rectifier switch is coupled to the second terminal of the first rectifier switch, the second terminal of the second rectifier switch is coupled to a second ground terminal, the second rectifier switch The control terminal of the switch receives the second control signal; and A second rectifier diode, the anode of the second rectifier diode is coupled to the second ground terminal, and the cathode of the second rectifier diode is coupled to the second end of the exciting inductor. The resonant converter as claimed in item 5, wherein the coupling circuit further includes: a first inductor configured to couple energy stored in the magnetizing inductor according to the first control signal to provide a first power consumption; a first discharge capacitor, the first terminal of the first discharge capacitor is coupled to the first terminal of the first inductor; and a first auxiliary switch, the first end of the first auxiliary switch is coupled to the second end of the first discharge capacitor, the second end of the first auxiliary switch is coupled to the second end of the first inductor, the control terminal of the first auxiliary switch receives the first control signal, Wherein when the first auxiliary switch is turned on, the first inductor and the first discharge capacitor jointly form the first discharge loop. The resonant converter as claimed in item 7, wherein the coupling circuit further comprises: a second inductor configured to couple the energy stored in the magnetizing inductor according to the second control signal to provide a second power consumption; a second discharge capacitor, the first terminal of the second discharge capacitor is coupled to the first terminal of the second inductor; and a second auxiliary switch, the first end of the second auxiliary switch is coupled to the second end of the second discharge capacitor, the second end of the second auxiliary switch is coupled to the second end of the second inductor, the control terminal of the second auxiliary switch receives the second control signal, Wherein when the second auxiliary switch is turned on, the second inductor and the second discharge capacitor jointly form the second discharge loop. The resonant converter as claimed in claim 8, wherein the first inductor is configured to consume the first power consumption through the first discharge circuit, and the second inductor is configured to consume the first power consumption through the second discharge circuit The second consumes electric energy. The resonant converter as claimed in claim 1, wherein the resonant circuit comprises: a resonant capacitor, the first terminal of the resonant capacitor is coupled to the connection node; and A resonant inductor, the first end of the resonant inductor is coupled to the second end of the resonant capacitor, and the second end of the resonant inductor is coupled to the first end of the primary winding.

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