LLC resonant converter with variable resonance frequency

Abstract

A resonant converter includes a high-side switch and a low-side switch, both coupled to a common node and driven by a complementary input signal. The common node drives a coupled inductor, with the coupled inductor connected in parallel with a variable impedance. The coupled inductor can be coupled in series with a capacitor and a transformer. The variable impedance can be adjusted to change the resonant frequency of the resonant converter.

Description

PRIORITY

[0001] This application claims priority over U.S. patent application No. 63 / 437,191, jointly owned and dated January 5, 2023, the entire contents of which are hereby incorporated by reference for all purposes. AREA OF INVENTION

[0002] The present disclosure relates to resonant transducers, more precisely to the control of an LLC resonant transducer. BACKGROUND

[0003] A resonant converter can convert an input signal into a DC voltage. Resonant converters can include switches in a half-bridge or full-bridge configuration and a resonant circuit. The resonant circuit can be used to control the resonant frequency within the converter. The output of the resonant circuit can be fed into the first winding of a transformer, and a load can be coupled across the second winding of the transformer.

[0004] As one of several examples, the resonant circuit can include a tank circuit connected in series with the load. When used in a resonant converter, the resonant circuit can act as a voltage divider between the impedance of the resonant circuit and the load impedance. At low loads, the load impedance is very large compared to the circuit's impedance, making it difficult to regulate the output, as this requires the frequency to approach infinity as the load approaches zero. Even at rated loads, a large frequency variation is required to regulate the power.

[0005] As one of many examples, a resonant circuit can include a tank circuit coupled in parallel to a load. When used in a resonant converter, the resonant circuit can conduct current or voltage from the load through the parallel tank circuit. A parallel resonator requires large amounts of circulating current. This makes it difficult to use parallel resonant topologies in applications with high power density or large load fluctuations.

[0006] An LLC resonant converter incorporates a resonant circuit, or tank circuit, consisting of two inductors and a capacitor. The first inductor can be a resonant inductor, and the second inductor can be a transformer winding. An LLC resonant circuit oscillates at a specific frequency, known as the resonant frequency. LLC resonant converters incorporating LLC tank circuits can achieve higher switching frequencies and lower switching losses than configurations with fewer components. LLC resonant converters can regulate power across output load fluctuations with a relatively small variation in switching frequency while maintaining excellent efficiency. Furthermore, they can switch without voltage (ZVS) across their entire operating range. LLC resonant converters can have a limited input voltage range due to the fixed resonant frequency of the resonant circuit. There is a need for LLC resonant converters with adjustable resonant circuits. SUMMARY

[0007] According to one aspect, an LLC resonant converter with adjustable impedance can enable adjustable resonant frequency and voltage regulation over a wide input voltage range.

[0008] According to one aspect, a resonant converter is provided comprising a first power switch with a first node coupled to a first phase of a complementary input signal and a second node coupled to a common node, and a second power switch with a first node coupled to a second phase of the complementary input signal and a second node coupled to the common node, wherein the common node is coupled to a resonant circuit, the resonant circuit having a resonant inductor with a first coupled inductor winding and a second coupled inductor winding, wherein the first coupled inductor winding is coupled between the common node and a first plate of a capacitor, and the second coupled inductor winding is coupled in parallel to a variable impedance circuit.wherein the variable impedance circuit sets the resonant frequency of the resonant circuit, and includes a transformer with a first transformer winding and a second transformer winding, wherein the first transformer winding is coupled between the second plate of the capacitor and a return line and the second transformer winding is coupled to a load.

[0009] According to one aspect, a method is provided, wherein the method involves driving a first node of a first circuit breaker and a first node of a second circuit breaker with a complementary periodic signal, wherein a second node of the first circuit breaker and a second node of the second circuit breaker are coupled to a common node, wherein a resonant circuit is coupled to the common node, and wherein the resonant frequency of the resonant circuit is adjusted by varying the impedance of a variable impedance circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The figures illustrate exemplary devices and methods for controlling LLC resonant transducers. Fig. Figure 1 illustrates an LLC resonant transducer according to various examples. Fig. Figure 2 illustrates an LLC resonant circuit amplification response in a first configuration. Fig. Figure 3 illustrates an LLC resonant circuit amplification playback in the first configuration and in a second configuration. Fig. Figure 4 illustrates a method for controlling the resonant frequency of a resonant transducer. DETAILED DESCRIPTION

[0011] Fig. Figure 1 illustrates one of several examples of an LLC resonant converter 100. A signal source 110 can generate an input signal. The signal source 110 is illustrated as a sine wave source, but this is not intended as a limitation. The signal source 110 can generate a square wave input signal, a pulse-width modulated input signal, a triangle wave input signal, or any other periodic input signal.

[0012] The output signal of signal source 110 can be fed into a phase-shifting circuit 122. The phase-shifting circuit 122 can shift the phase of the output signal of signal source 110. In one of several examples, the phase-shifting circuit 122 can shift the phase of the output signal of signal source 110 by 180 degrees. The output of signal source 110 can provide an input for the gate of high-side switch 120. The output of the phase-shifting circuit 122 can provide an input for the gate of low-side switch 121. In this way, high-side switch 120 and low-side switch 121 can be controlled with a complementary input signal. The high-side switch 120 can be controlled with a first phase of the complementary input signal 112, and the low-side switch 121 can be controlled with a second phase of the complementary input signal 113.The complementary input signal can be a square wave, a pulse-width modulated (PWM) signal, a triangle wave, or another periodic input signal. In the example in... Fig. In the illustrated example 1, the phase-shifting circuit 122 is shown as a discrete component, but in other examples, the complementary inputs of the high-side switch 120 and the low-side switch 121 can be provided directly by the signal source 120 with the corresponding phase shift, so that the phase-shifting circuit 122 is not required or can be considered as being included in the signal source 110. The high-side switch 120 can be a metal-oxide field-effect transistor (MOSFET), a bipolar transistor, or another type of transistor. The low-side switch 121 can be a metal-oxide field-effect transistor (MOSFET), a bipolar transistor, or another type of transistor. The high-side switch 120 can be coupled to the high-side power supply 190. The low-side switch 121 can be coupled to a return line which includes, among other things, the earthing node 160.The high-side switch 120 and the low-side switch 121 can be coupled via the common node 125. The high-side switch 120 and the low-side switch 121 are illustrated as n-channel transistors, but this is not intended as a restriction. The high-side switch 120 can be a p-channel transistor. The low-side switch 121 can be a p-channel transistor. The high-side switch 120 and the low-side switch 121 are illustrated as field-effect devices, but this is not intended as a restriction. The high-side switch 120 can be a bipolar device. The low-side switch 121 can also be a bipolar device.

[0013] The high-side switch 120 and the low-side switch 121 can be coupled to the resonant inductor 130. The resonant inductor 130 can be the first inductor in an LLC resonant converter. The resonant inductor 130 can be coupled in parallel to the variable impedance circuit 135.

[0014] During operation, the impedance value of the variable impedance circuit 135 can be modified to change the resonant frequency of the resonant transducer 100. The variable impedance circuit 135 is in Fig. Figure 1 illustrates a variable resistor, but this is not intended to be a limitation. The variable impedance circuit 135 can be a variable resistor. The variable impedance circuit 135 can be a variable-amplitude DC current source that saturates the core of the resonant inductor 130 and changes the impedance of the resonant inductor 130. The variable impedance circuit 135 can be a variable-amplitude AC current source. The variable impedance circuit 135 can be a switch that includes, but is not limited to, a MOSFET switch in series with a resistor.

[0015] The resonant inductor 130 can be coupled to a first plate of the resonant capacitor 140. A transformer 150 can be coupled to the second plate of the resonant capacitor 140. The first winding of the transformer 150 can be the second inductor in the LLC resonant converter. A first winding of the transformer 150 can be coupled between the second plate of the resonant capacitor 140 and a return line that includes, among other things, the ground node 160. A second winding of the transformer 150 can be coupled to a load 170. The signal provided to the load can also be referred to as the output signal of the LLC resonant converter 100.

[0016] In the example of Fig. 1. Changing the impedance of the resonant inductor 130 can alter the resonant frequency of the resonant transducer 100. In one of the various examples, the variable impedance circuit 135 can be a variable resistor. Adjusting the value of the variable resistor can change the resonant point of the resonant transducer 100. Increasing the variable resistor can increase the inductance. In one of the various examples, the variable impedance circuit 135 can be a variable-amplitude DC source. Adjusting the amplitude of the variable-amplitude DC source can change the resonant point of the transducer, since the amplitude of the variable-amplitude DC source can magnetize the core of the resonant inductor 130. In one of the various examples, the variable impedance circuit 135 can be a variable-amplitude AC source.Adjusting the amplitude of the variable-amplitude AC power source can magnetize the core of the resonant inductor 130. This magnetization of the core can indirectly reduce the inductance of the resonant inductor 130.

[0017] Fig. Figure 2 illustrates one of several examples of frequency response graphs for an LLC resonant converter in a first configuration. In the first configuration, the inductance value of the resonant inductor can be chosen to achieve a specific output characteristic. The y-axis can represent the gain from the input of the resonant circuit to the output, represented by the label Vout / V. This graph shows illustrations of the frequency response for several load values. Each curve represents a different load value. The output at certain voltages can only be achieved if the resonant circuit is operated below its resonant frequency. The resonant frequency is located at the top of the curves, in Fig. 2 is labeled 210. Zero-Voltage Switching (ZVS) mode occurs when the high-side switch 120 and the low-side switch 121 are switched when zero volts are applied across them. Zero-Current Switching (ZCS) mode occurs when the high-side switch 120 and the low-side switch 121 are switched when no current flows through them. When operating below the resonant frequency, the high-side and low-side switches may not operate in ZVS mode and could introduce a high current. This could cause catastrophic converter failure.

[0018] Fig. Figure 3 illustrates one of several examples of frequency response diagrams 300 for an LLC resonant transducer in a first configuration and in a second configuration. The set of curves that exhibits a peak at a frequency close to 100 kHz and is labelled 320 illustrates the resonant circuit in the first configuration, as shown in Fig. 2 is formed. The set of curves that form a peak at a frequency near 70 kHz illustrates the resonant circuit in a second configuration, labeled 310. In the second configuration, the inductance value of the resonant inductor can be chosen to achieve a specific output response. The y-axis can represent the gain from the input of the resonant circuit to the output, indicated by the label Vout / V. This graph shows illustrations of the frequency response for different load values. Each curve represents a different load value. In the example of Fig. 3. The impedance of the variable impedance circuit 135 can be modified to change the resonant circuit from the first configuration to the second configuration, resulting in a lower resonant frequency than that in Fig. The resonant frequency is generated as illustrated in Figure 2. The inductance of the resonant inductor can be increased by increasing the impedance of the variable impedance circuit 135. The inductance of the resonant inductor can be decreased by decreasing the impedance of the variable impedance circuit 135. By increasing the inductance of the resonant inductor 130, the resonant frequency can be decreased, and the circuit can continue to operate above the resonant frequency in a ZVS mode.

[0019] Fig. Figure 4 illustrates one of several examples of a method for controlling the resonant frequency of a resonant transducer. The resonant transducer can be an LLC resonant transducer, as previously described with reference to Fig. 1 described.

[0020] Operation 410 allows a first and a second circuit breaker to be controlled with a complementary input signal. The complementary input signal can be a square wave, a pulse-width modulated (PWM) signal, a triangle wave, or another periodic signal. The first and second circuit breakers can be coupled via a common node.

[0021] In operation 420, a resonant circuit can be coupled to the common junction of the first and second circuit breakers. The resonant circuit can include a resonant inductor connected in parallel to a variable impedance circuit. In one of several examples, the variable impedance circuit can be a variable resistor. In another example, the variable impedance circuit can be a variable-amplitude DC current source. In yet another example, the variable impedance circuit can be a variable-amplitude AC current source. Adjusting the amplitude of the variable-amplitude AC current source can magnetize the core of the resonant inductor. Magnetizing the core can indirectly decrease the inductance of the resonant inductor.

[0022] In operation 430, the resonant frequency of the resonant circuit can be adjusted by changing the impedance of a variable impedance circuit. Adjusting the variable impedance value can change the resonant transducer's resonant point. Adjusting the amplitude of the variable-amplitude DC source can also change the transducer's resonant point, as the DC source's amplitude can magnetize the resonant inductor's core. Similarly, adjusting the amplitude of the variable-amplitude AC source can magnetize the core of the resonant inductor. This core magnetization can indirectly decrease the resonant inductor's inductance. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 437,191

[0001]

Claims

[1] Resonance transducer which features: a first circuit breaker with a first node coupled to a first phase of a complementary input signal, and a second node coupled to a common node; a second circuit breaker with a first node coupled to a second phase of the complementary input signal, and a second node coupled to the common node; wherein the common node is coupled to a resonant circuit, wherein the resonant circuit has: a resonant inductor with a first coupled inductor winding and a second coupled inductor winding, wherein the first coupled inductor winding is coupled between the common node and a first plate of a capacitor, and the second coupled inductor winding is coupled in parallel to a variable impedance circuit, wherein the variable impedance circuit sets the resonant frequency of the resonant circuit, and a transformer with a first transformer winding and a second transformer winding, wherein the first transformer winding is coupled between the second plate of the capacitor and a return line and the second transformer winding is coupled to a load. [2] Resonance converter according to claim 1, wherein the first power switch comprises a power metal oxide semiconductor field-effect device (MOSFET) and the second power switch comprises a power metal oxide semiconductor field-effect device (MOSFET). [3] Resonance transducer according to one of claims 1 to 2, wherein the first phase and the second phase of the complementary input signal have a periodic signal. [4] Resonance transducer according to one of claims 1 to 2, wherein the first phase and the second phase of the complementary input signal comprise a pulse width modulated signal. [5] Resonance transducer according to any one of claims 1 to 4, wherein the variable impedance circuit has a variable resistance. [6] Resonance transducer according to claim 5, wherein the variable impedance circuit has at least one switch coupled to the variable resistance. [7] Resonance transducer according to any one of claims 1 to 6, wherein the variable impedance circuit comprises a DC source with variable amplitude. [8] Resonance transducer according to any one of claims 1 to 6, wherein the variable impedance circuit comprises an alternating current source with variable amplitude. [9] Method which features: Controlling a first node of a first circuit breaker and a first node of a second circuit breaker with a complementary periodic signal, wherein a second node of the first circuit breaker and a second node of the second circuit breaker are coupled to a common node; Coupling a resonant circuit to the common node; and Adjusting the resonant frequency of the resonant circuit by varying the impedance of a variable impedance circuit. [10] Method according to claim 9, wherein the first power switch comprises a power metal oxide semiconductor field effect device (MOSFET) and the second power switch comprises a power metal oxide semiconductor field effect device (MOSFET). [11] Method according to any one of claims 9 to 10, wherein the input signal is a pulse width modulated signal. [12] Method according to any one of claims 9 to 11, wherein the variable impedance circuit has a variable resistance. [13] Method according to any one of claims 9 to 12, wherein the variable impedance circuit comprises a DC source with variable amplitude. [14] Method according to any one of claims 9 to 13, wherein the variable impedance circuit comprises an alternating current source with variable amplitude. [15] Method according to any one of claims 9 to 14, wherein the resonant circuit comprises a coupled inductor, a capacitor and a transformer. [16] Method according to claim 13, wherein adjusting the resonant frequency by varying the impedance of a variable impedance circuit comprises at least varying the impedance of the variable impedance circuit based on the current in the variable amplitude DC source. [17] Method according to claim 14, wherein adjusting the resonant frequency by varying the impedance of a variable impedance circuit comprises varying the impedance of the variable impedance circuit at least on the basis of the current in the variable amplitude AC source. [18] Method according to claim 15, wherein the coupled inductor has a first coupled inductor winding which is coupled between the common node and a first plate of the capacitor, and a second coupled inductor winding which is coupled in parallel to the variable impedance circuit.

Images