Resonant converter

Abstract

The application provides a resonant converter, which comprises a half-bridge unit and a resonant unit, an input end of the resonant unit is connected in parallel with an output end of the half-bridge unit, the resonant unit comprises a first capacitor, a first inductor and a transformer, the first capacitor, the first inductor and a primary winding of the transformer are connected in series, the transformer comprises a first secondary winding and a second secondary winding, and the resonant converter further comprises a first output rectification filter unit and a second output rectification filter unit, and the output ends of the first output rectification filter unit and the second output rectification filter unit are connected in parallel to output direct current. The application combines frequency control and duty cycle control, and widens the voltage regulation rate of the resonant converter.

Description

Technical Field

[0001] This invention relates to the field of power conversion technology, and more specifically to a resonant converter with an ultra-wide voltage regulation rate. Background Technology

[0002] LLC resonant converters possess a range of superior performance characteristics: zero-voltage turn-on of the primary-side switches and zero-current turn-off of the secondary-side rectifier bridge diodes; electrical isolation between the primary and secondary sides; and the ability to achieve both boost and buck voltage conversion. They are widely used in applications such as traction power electronic transformers for rail transit, charging devices for new energy vehicles, server power supplies, and other industrial power supplies.

[0003] LLC resonant converters typically employ variable frequency modulation (VFM) technology, where a pulse-width modulated signal with a fixed duty cycle of 0.5 Hz symmetrically drives the upper and lower arm switches, controlling the power flow to the output side by adjusting the switching frequency. When the input voltage varies over a wide range, to change the voltage gain of the resonant tank and obtain a stable output voltage, the switching frequency needs to be adjusted away from the resonant point. This leads to a decrease in the performance and efficiency of the LLC resonant converter. Therefore, the voltage regulation rate of the LLC resonant converter is limited. Summary of the Invention

[0004] This invention provides a resonant converter that, while ensuring the performance and efficiency of an LLC resonant converter, has a sufficient voltage regulation rate.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] Resonant converter, including,

[0007] Half-bridge unit,

[0008] A resonant unit is provided, wherein the input terminal of the resonant unit is connected in parallel with the output terminal of the half-bridge unit. The resonant unit includes a first capacitor, a first inductor, and a transformer. The first capacitor, the first inductor, and the primary winding of the transformer are connected in series. The transformer includes a first secondary winding and a second secondary winding.

[0009] The first output rectifier and filter unit includes a first diode and a first switch, wherein the first diode and the first switch are connected in series with the first secondary winding.

[0010] The second output rectifier and filter unit includes a second diode, which is connected in series with the second secondary winding. The output terminal of the second output rectifier and filter unit is connected in parallel with the output terminals of the first output rectifier and filter unit and the second rectifier and filter unit to output DC power.

[0011] The aforementioned half-bridge unit includes a second switch and a third switch, which are connected in series, and the input terminal of the resonant unit is connected in parallel with the third switch.

[0012] The present invention also provides a single-stage AC-DC converter, including the above-mentioned resonant converter, and further including a rectifier unit, wherein the input terminal of the rectifier unit is connected to AC power, and the output of the rectifier unit is connected in parallel with the input terminal of the half-bridge unit.

[0013] When the AC current is less than the first set value, the first switch is closed; when the AC current is greater than the second set value, the first switch is open; when the AC current is between the first set value and the second set value, the first switch remains in the same state.

[0014] When the first switch is closed, the second and third switches are complementaryly activated, and the switching frequency of the third switch is adjusted; when the first switch is open, the second and third switches are complementaryly activated, and the switching duty cycle of the third switch is adjusted.

[0015] The present invention also provides a multi-stage AC-DC converter, including the above-mentioned resonant converter, and further including a rectifier unit and a power factor correction unit. The input terminal of the rectifier unit is connected to AC power, the output of the rectifier unit is connected in parallel with the power factor correction unit, and the output terminal of the power factor correction unit is connected in parallel with the input terminal of the half-bridge unit.

[0016] When the DC output of the aforementioned multi-stage AC-DC converter is less than the third set value, the first switch is open; when the DC output is greater than the third set value, the first switch is closed.

[0017] When the first switch is closed, the second and third switches are complementaryly activated, and the switching frequency of the third switch is adjusted; when the first switch is open, the second and third switches are complementaryly activated, and the switching duty cycle of the third switch is adjusted.

[0018] This invention also provides a control method for a resonant converter, including,

[0019] Step S1: Detect the input voltage of the resonant converter;

[0020] When the input voltage in step S2 is greater than the fourth preset value, the first switch is turned off; when the input voltage is less than the fourth preset value, the first switch is turned on.

[0021] When the first switch is turned off in step S3, the second and third switches are complementary and turned on, adjusting the duty cycle of the second switch to adjust the output voltage or current.

[0022] In step S4, when the first switch is closed, the second and third switches are complementary and conduct, adjusting the switching frequency of the third switch to regulate the output voltage or current.

[0023] The resonant converter of the present invention has a wide voltage regulation rate. When applied to a single-stage AC-DC converter, it can adapt to different grid voltage conditions. When applied to a multi-stage AC-DC converter, it can provide a wide DC voltage range. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a specific embodiment of the resonant converter of the present invention.

[0025] Figure 2 Applied to Figure 1 The flowchart of the control method for the resonant converter is shown.

[0026] Figure 3 for Figure 1 The diagram shows a specific embodiment of the resonant converter applied to a single-stage AC-DC converter.

[0027] Figure 4 For application Figure 3 The controller of the single-stage AC-DC converter shown is shown.

[0028] Figure 5 For application Figure 3 The flowchart shows the control method for a single-stage AC-DC converter.

[0029] Figure 6 for Figure 1 The diagram shows a specific embodiment of the resonant converter applied to a multi-stage AC-DC converter.

[0030] Figure 7 For application Figure 6 The controller of the multi-stage AC-DC converter shown.

[0031] Figure 8 For application Figure 6 The flowchart shows the control method of the multi-stage AC-DC converter. Detailed Implementation

[0032] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] The terms "first," "second," "third," "fourth," etc., as used in this invention (if any) are used to distinguish similar elements and do not necessarily describe a specific order or chronological sequence. It should be understood that these terms are interchangeable in appropriate contexts, allowing implementations of the subject matter described herein to be performed, for example, in an order different from those described or in an order otherwise described herein. Furthermore, wherever possible, components / members / steps using the same reference numerals in the figures and embodiments represent the same or similar parts.

[0034] Figure 1 The resonant converter of the present invention is shown, including a half-bridge unit 11 with an input voltage Vin connected in parallel at its input terminal. The half-bridge unit 11 includes switches Q1 and Q2 connected in series. A resonant unit 12 is connected in parallel across the two ends of switch Q2. The resonant unit 12 includes a capacitor Cr, an inductor Lr, and a transformer T1. The primary winding N1 of the capacitor Cr, inductor Lr, and transformer T1 is connected in series. The transformer T1 includes secondary windings N2 and N3. A first output rectifier and filter unit 13 includes a diode D5 and a switch Q3, which are connected in series with the secondary winding N2. A second output rectifier and filter unit 14 includes a diode D6, which is connected in series with the secondary winding N3. The output terminal of the second output rectifier and filter unit 14 is connected in parallel with the output terminal of the first output rectifier and filter unit 13 and a capacitor Co, outputting a DC voltage Vout.

[0035] Figure 2 The diagram illustrates the control method for the resonant converter of this invention, used to control, for example... Figure 1 The resonant converter shown includes the following steps:

[0036] Step S21: Detect the voltage value of the input voltage Vin of the resonant converter;

[0037] When the voltage value of the input voltage Vin in step S22 is greater than the fourth set value, the switch Q3 is turned off; when the voltage value of the input voltage Vin is less than the fourth set value, the switch Q3 is closed.

[0038] When switch Q3 is turned off in step S23, switches Q1 and Q2 are complementary and conduct, adjusting the duty cycle of switch Q1 to adjust the voltage or current of the output voltage Vout.

[0039] When switch Q3 is closed in step S24, switches Q1 and Q2 are complementary and conduct, adjusting the switching frequency of switch Q1 to regulate the voltage or current of the output voltage Vout.

[0040] Figure 3The diagram shows a single-stage AC-DC converter, including the aforementioned resonant converter 10 and a rectifier unit 34. The input terminal of the rectifier unit 34 is connected to an AC power supply. u in The output terminal of the rectifier unit 34 is connected in parallel with the input terminal of the resonant converter 10 after passing through capacitor C2.

[0041] Please refer to this again. Figure 4 The controller of the single-stage AC-DC converter includes diodes D7 and D8, with the anodes of diodes D7 and D8 receiving AC input. u in The cathodes of diodes D7 and D8 are connected in parallel, and after being divided by resistors R3 and R4, the voltage is input to the digital control unit (MCU). The MCU integrates the control methods for switches Q1, Q2, and Q3, and outputs control signals V for switches Q1, Q2, and Q3. gs- Q1 V gs- Q2 and V gs- Q3 Control signal V gs- Q1 V gs- Q2 and V gs- Q3 This is used to control the on / off state of switches Q1, Q2, and Q3. The control signal V output by the digital control unit (MCU) is... gs- Q3 The signal is transmitted to switch Q3 via optocoupler OPT isolation.

[0042] Figure 5 The diagram shows the control method of the controller for a single-stage AC-DC converter, integrated into... Figure 4 The digital control unit (MCU) shown includes:

[0043] Step S51: Detect the AC input of the single-stage AC-DC converter. u in The voltage is used to obtain the sampled value Uin;

[0044] When the sampled value Uin is less than the first set value in step S52, the switch Q3 is closed; when the sampled value Uin is greater than the second set value, the switch Q3 is open; when the sampled value Uin is between the first set value and the second set value, the switch Q3 remains in the same state.

[0045] When switch Q3 is closed in step S53, switches Q1 and Q2 are complementary and conduct, and the switching frequency of switch Q1 is adjusted.

[0046] When switch Q3 is turned off in step S54, switches Q1 and Q2 are turned on complementaryly, and the duty cycle of switch Q1 is adjusted.

[0047] Figure 6As shown, the present invention also provides a multi-stage AC-DC converter, including a resonant converter 10, a rectifier unit 64, and a power factor correction unit 65, wherein the input terminal of the rectifier unit 64 is connected to an AC power supply. u in The output terminal of the rectifier unit 64 is connected in parallel with the power factor correction unit 65, and the output terminal of the power factor correction unit 65 is connected in parallel with the input terminal of the resonant converter 10. In a preferred embodiment, the rectifier unit 64 includes diodes D1, D2, D3, and D4, which form a full-bridge rectifier unit. The rectifier unit 64 also includes a capacitor C2, which is connected in parallel with the output terminal of the full-bridge rectifier unit. In a preferred embodiment, the power factor correction unit 65 includes an inductor L1, a switch Q4, a diode D9, and a capacitor C3, which form a boost converter unit. The circuit structure and operating principle of the resonant converter 10 are similar to those of the previous embodiment. Figure 1 The embodiments shown are the same.

[0048] Figure 7 As shown Figure 6 In a specific embodiment of the controller of the multi-stage AC-DC converter, the comparison unit U1 samples the voltage value of the DC voltage Vout through the sampling unit (not shown in the figure) to obtain a voltage sampling value Vout', and compares the voltage sampling value Vout' with a set value Vref, and outputs a signal V. gs-Q3 The signal V is driven by the switch Q3 drive unit. gs-Q3 When the signal is high, switch Q3 is closed; the signal V gs-Q3 When the signal is low, switch Q3 is off. Signal V gs-Q3 The signal V is transmitted to the digital control unit (MCU) via resistor R1 and optocoupler OPT. gs-Q3 The voltage is pulled up by resistor R2. The digital control unit (MCU) outputs signal V. gs-Q1 and signal V gs-Q2 The drive units for switches Q1 and Q2 are described. The control method for the digital control unit (MCU) is described in [reference needed]. Figure 8 It includes the following steps:

[0049] Step S81: Detect the DC output of the multi-stage AC-DC converter. Vout The voltage value is used to obtain the sampled value Vout';

[0050] When the sampled value Vout' is less than the third set value in step S82, the switch Q3 is open; when the sampled value Vout' is greater than the third set value, the switch Q3 is closed.

[0051] When switch Q3 is closed in step S83, switches Q1 and Q2 are complementary and conduct, and the switching frequency of switch Q1 is adjusted.

[0052] When switch Q3 is turned off in step S84, switches Q1 and Q2 are turned on complementaryly, and the duty cycle of switch Q1 is adjusted.

[0053] The resonant converter of this invention combines frequency regulation and duty cycle regulation methods, exhibiting a wide voltage regulation rate. When applied to single-stage AC-DC converters, it can adapt to different grid voltage conditions. For example, in a low-voltage grid environment, switch Q3 is closed, and the frequency of switch Q1 is adjusted, while switch Q2 has a fixed on-time to achieve output regulation. In a high-voltage grid environment, switch Q3 is open, and the duty cycle of switch Q1 is adjusted, while switch Q2 has a fixed on-time to achieve output regulation. When applied to multi-stage AC-DC converters, such as in battery charging, when the battery voltage is less than 48V, switch Q3 is open, and the duty cycle of switch Q1 is adjusted, while switch Q2 has a fixed on-time. When the battery voltage is greater than 48V, switch Q3 is closed, and the frequency of switch Q1 is adjusted. Furthermore, the adjustment of the duty cycle of switch Q2 described in this invention includes various methods, such as adjusting the on-time while keeping the off-time constant; or adjusting the on-time while also changing the off-time.

[0054] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A resonant converter, characterized in that, include, Half-bridge unit, A resonant unit is provided, wherein the input terminal of the resonant unit is connected in parallel with the output terminal of the half-bridge unit. The resonant unit includes a first capacitor, a first inductor, and a transformer. The first capacitor, the first inductor, and the primary winding of the transformer are connected in series. The transformer includes a first secondary winding and a second secondary winding. The first output rectifier and filter unit includes a first diode and a first switch, wherein the first diode and the first switch are connected in series with the first secondary winding. The second output rectifier and filter unit includes a second diode, which is connected in series with the second secondary winding. The output terminal of the second output rectifier and filter unit is connected in parallel with the output terminal of the first output rectifier and filter unit and the output terminal of the second rectifier and filter unit to output DC power. The half-bridge unit includes a second switch and a third switch, the second switch and the third switch are connected in series, and the input terminal of the resonant unit is connected in parallel with the third switch; The resonant converter is configured to: control the on / off state of the first switch according to the voltage value of the input current of the resonant converter; when the first switch is closed, the second switch and the third switch are complementaryly turned on, and the switching frequency of the third switch is adjusted; when the first switch is open, the second switch and the third switch are complementaryly turned on, and the duty cycle of the third switch is adjusted.

2. A single-stage AC-DC converter, comprising the resonant converter as described in claim 1, characterized in that, It also includes a rectifier unit, the input of which is connected to AC power, and the output of which is connected in parallel with the input of the half-bridge unit; When the first switch is closed, the second and third switches are complementaryly activated, and the switching frequency of the third switch is adjusted; when the first switch is open, the second and third switches are complementaryly activated, and the switching duty cycle of the third switch is adjusted.

3. The single-stage AC-DC converter as described in claim 2, characterized in that, When the AC current is less than a first set value, the first switch is closed; when the AC current is greater than a second set value, the first switch is open; when the AC current is between the first set value and the second set value, the first switch remains in the same state.

4. A multi-stage AC-DC converter, comprising the resonant converter as described in claim 1, characterized in that, It also includes a rectifier unit and a power factor correction unit. The input terminal of the rectifier unit is connected to AC power, the output of the rectifier unit is connected in parallel with the power factor correction unit, and the output terminal of the power factor correction unit is connected in parallel with the input terminal of the half-bridge unit. When the first switch is closed, the second and third switches are complementaryly activated, and the switching frequency of the third switch is adjusted; when the first switch is open, the second and third switches are complementaryly activated, and the switching duty cycle of the third switch is adjusted.

5. The multi-stage AC-DC converter as described in claim 4, characterized in that, When the DC current is less than the third set value, the first switch is turned off; when the DC current is greater than the third set value, the first switch is turned off.

6. A control method for controlling the resonant converter as described in claim 1, characterized in that, include, Step S1: Detect the input voltage of the resonant converter; When the input voltage is greater than the fourth preset value in step S2, the first switch is turned off; when the input voltage is less than the fourth preset value, the first switch is turned on. When the first switch is turned off in step S3, the second and third switches are complementary and turned on, adjusting the duty cycle of the second switch to adjust the output voltage or current. In step S4, when the first switch is closed, the second and third switches are complementary and conduct, adjusting the switching frequency of the third switch to adjust the output voltage or current.

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