A dual-frequency DC-DC converter and its dynamic coordinated control method

Abstract

This invention provides a dual-frequency DC-DC converter and its dynamic coordination control method, belonging to the technical field of DC-DC converters. The invention includes an LLC resonant converter module and a PWM DC-DC converter module. The input of the PWM DC-DC converter module is cascaded with the secondary output of the LLC resonant converter module, and its output is connected in series with the main output of the LLC resonant converter module. The LLC resonant converter module operates in open loop at a kHz-level switching frequency and always operates at the resonant frequency point; the PWM DC-DC converter module operates at a MHz-level switching frequency, transmits less than 20% of the power, and dynamically coordinates and cancels the ripple of the main output of the LLC resonant converter module. This invention achieves low output ripple while possessing the advantages of a wide output voltage range and fast response speed, and exhibits high efficiency and high power density characteristics comparable to conventional LLC resonant converters.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converter technology, and in particular to a low-ripple dual-frequency DC-DC converter and its dynamic coordination control method. Background Technology

[0002] With the rapid development of information and communication technologies, the scale and energy consumption of data centers are increasing rapidly, leading to a growing demand for high-performance server power supplies with low output ripple, wide voltage regulation range, and fast response speed. LLC resonant converters, due to their high efficiency and high power density, are currently the most widely used topology in server power supplies. However, LLC resonant converters have a discontinuous output current characteristic, resulting in relatively large output ripple in medium to high power applications, which limits their application range to some extent.

[0003] To meet the requirement of low output ripple, using large-capacity, large-volume capacitors to filter the output of LLC resonant converter is a simple and effective method, but it reduces the power density of LLC resonant converter to some extent.

[0004] LLC resonant converters can significantly reduce output ripple by using an interleaved parallel topology. However, due to the existence of component tolerances, additional power switches, inductors, capacitors, and current sharing control strategies are required to ensure reliable operation, increasing the complexity of the system. For example, Chinese patent application No. 201910904161.6 discloses an interleaved parallel circuit of a half-bridge LLC resonant converter module and its current sharing control method. Multiple LLC resonant converter modules with the same topology are interleaved and paralleled, and the driving signals of each LLC resonant converter module are phased, which can achieve the cancellation of system output ripple. However, this method has the following shortcomings: (1) Due to the existence of resonant component tolerances, the interleaved parallel LLC resonant converter requires additional power switches, inductors, capacitors, and current sharing control strategies to achieve output current balance, which increases system cost and reduces power density; (2) The PFM modulation of the LLC resonant converter module is tightly coupled with current sharing control and auxiliary power switch control, increasing the complexity of system output voltage regulation.

[0005] In addition, increasing the switching frequency of power devices is also a method to reduce output ripple. Replacing silicon-based semiconductor devices with wide-bandgap semiconductor devices can increase the switching frequency and improve the output ripple, power density, efficiency, and other performance indicators of the power supply. However, this places more stringent requirements on power devices, transformers, and the EMI of the power supply, and the cost also increases accordingly. For example, Chinese patent application CN201910740392.8 discloses a high-power-density GaN capacitor series-interleaved parallel PFC power supply module. By using wide-bandgap semiconductor devices with high switching speed and low switching losses, the switching frequency of the DC-DC converter module is increased, and the power supply has the advantages of low output ripple, high power density, and high efficiency. However, this method has the following shortcomings: (1) High switching frequency operation places more stringent requirements on power devices, requiring the selection of wide bandgap semiconductor devices with fast switching speed and low switching loss. However, the price of wide bandgap semiconductor devices of the same specifications is more than five times that of silicon-based semiconductor devices of the same specifications, which will significantly increase the cost of the system; (2) Due to the skin effect and proximity effect of the transformer winding, high switching frequency operation will increase the eddy current loss of the transformer and significantly reduce the efficiency of the power supply device; (3) High switching frequency operation will seriously affect the performance of the DC-DC converter due to the parasitic parameters of the circuit, and the EMI problem cannot be ignored, which increases the design difficulty of the power supply device.

[0006] In summary, while the aforementioned technical solutions can effectively reduce the output ripple of LLC resonant converters in medium- and high-power applications, they also lead to problems such as decreased power density, increased system control complexity, increased cost, increased transformer design difficulty, and increased EMI suppression difficulty. Therefore, a simple and effective technical solution is lacking to reduce the output ripple of LLC resonant converters in medium- and high-power applications while simultaneously considering performance indicators such as efficiency, power density, and cost.

[0007] The existing technology has at least the following shortcomings:

[0008] 1. While reducing the output ripple of LLC resonant converters, problems such as decreased power density, increased system control complexity, and increased cost are caused.

[0009] 2. While reducing the output ripple of the LLC resonant converter, it also leads to problems such as increased difficulty in transformer design and EMI suppression in the power supply unit. Summary of the Invention

[0010] To address the technical problems existing in the prior art, this invention provides a low-ripple dual-frequency DC-DC converter and its dynamic coordination control method. The proposed dual-frequency DC-DC converter includes an LLC resonant converter module and a PWM DC-DC converter module. The input of the PWM DC-DC converter module is cascaded with the secondary output of the LLC resonant converter module, and its output is connected in series with the main output of the LLC resonant converter module. The LLC resonant converter module operates in open loop at a kHz-level switching frequency, always operating at the resonant frequency point; the PWM DC-DC converter module operates at a MHz-level switching frequency, transmitting less than 20% of the power, and dynamically coordinates and cancels the ripple of the main output of the LLC resonant converter module. The proposed dual-frequency DC-DC converter achieves low output ripple while possessing the advantages of a wide output voltage range and fast response speed, and exhibits high efficiency and high power density characteristics comparable to conventional LLC resonant converters.

[0011] This invention provides a dual-frequency DC-DC converter, comprising an LLC resonant converter module and a PWM DC-DC converter module. The input of the PWM DC-DC converter module is cascaded with the secondary output of the LLC resonant converter module, and its output is connected in series with the main output of the LLC resonant converter module. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module, the output voltage of the secondary output of the LLC resonant converter module, and the output voltage of the PWM DC-DC converter module satisfy the following relationship:

[0012]

[0013] in,

[0014] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0015] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0016] V o2 The output voltage of the LLC resonant converter module's secondary output;

[0017] V o1_ac This refers to the AC component of the output voltage of the main output of the LLC resonant converter module.

[0018] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module.

[0019] V o1_dc This refers to the DC component of the output voltage of the main output of the LLC resonant converter module.

[0020] Vo3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module.

[0021] D represents the duty cycle of the PWM DC-DC converter module.

[0022] Preferably, the LLC resonant converter module includes a chopper unit, a resonant circuit unit, a transformer unit, multiple rectifier units, an input filter capacitor, and multiple output filter capacitors; the transformer unit is a multi-winding transformer; the chopper unit, the resonant circuit unit, and the transformer unit are cascaded sequentially; the multiple rectifier units respectively rectify the multiple windings of the transformer unit; the input filter capacitor is connected in parallel with the input power supply; and the multiple output filter capacitors are respectively connected in parallel with the outputs of the multiple rectifier units and the PWM DC-DC converter module.

[0023] Preferably, the plurality of rectifier units include a first rectifier unit and a second rectifier unit, and the secondary winding of the transformer unit includes a main winding and a secondary winding, wherein the turns ratio of the main winding and the secondary winding satisfies N2≥N3;

[0024] N2 is the number of turns in the main winding;

[0025] N3 is the number of turns in the secondary winding.

[0026] Preferably, the main output voltage V of the LLC resonant converter module is... o1 The output voltage V of the secondary output o2 The following relationship must be satisfied:

[0027]

[0028] Preferably, the chopper unit in the LLC resonant converter module is a half-bridge structure, a full-bridge structure, or a multi-level structure, wherein the power devices are silicon-based devices.

[0029] Preferably, the PWM DC-DC converter module includes a DC-DC converter unit, which is a Buck converter, a Buck-Boost converter, or a Cuk converter, wherein the power device is a wide-bandgap device.

[0030] This invention provides a dynamic coordination control method for any of the above-mentioned dual-frequency DC-DC converters, comprising:

[0031] The LLC resonant converter module operates in open loop at a kHz-level switching frequency and always operates at the resonant frequency point. After PFM modulation, it controls the turn-on and turn-off of the power devices in the chopper unit.

[0032] The PWM DC-DC converter module operates at a switching frequency in the MHz range and transmits less than 20% of its power.

[0033] The PWM DC-DC converter module determines the voltage based on the detected V. o1 V o2 and I o2 The duty cycle of the PWM DC-DC converter module is predicted for the next switching cycle. Through PWM modulation, the switching on and off of the power devices in the DC-DC converter unit is controlled, thereby regulating the output voltage of the PWM DC-DC converter module to achieve the desired voltage V. o3_ac With V o1_ac They cancel each other out to satisfy the following relationship

[0034] V o1_ac +V o3_ac =0

[0035] This makes the output voltage V of the dual-frequency DC-DC converter o Contains only the DC component to satisfy the following relationship

[0036] V o =V o1_dc +V o3_dc

[0037] in,

[0038] I o2 This refers to the output current of the LLC resonant converter module's secondary output.

[0039] Preferably, the PWM DC-DC converter module determines the voltage based on the detected V. o1 and V o2 The increase in output current ΔI of the PWM DC-DC converter module within one switching cycle is obtained. o2_up and decrease value ΔI o2_down for

[0040]

[0041] in,

[0042] T s Indicates the switching cycle;

[0043] L o This is the power inductor for the PWM DC-DC converter module.

[0044] Preferably, the PWM DC-DC converter module determines the I based on the detected I o2 The increase in output voltage ΔV of the PWM DC-DC converter module during one switching cycle is obtained. o2_up and decrease value ΔV o2_down for

[0045]

[0046] in,

[0047] R L For load;

[0048] C o3 This is the output capacitor of the DC-DC converter module.

[0049] Preferably, the PWM DC-DC converter module determines the voltage based on the detected V. o1 V o2 and I o2 The predicted duty cycle D for the next switching cycle is:

[0050]

[0051] in,

[0052] ΔV o3 For the voltage error of the PWM DC-DC converter module, the following relationship must be satisfied.

[0053]

[0054] in,

[0055] V o * represents the given value of the output voltage of the dual-frequency DC-DC converter;

[0056] V' o This is the feedback value of the output voltage of the dual-frequency DC-DC converter;

[0057] V o1(k) -V o1(k-1) The voltage difference between the main output voltage of the LLC resonant converter module at time K and time K-1 is used as the predicted value of the main output voltage of the LLC resonant converter module in the next switching cycle.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0059] 1. In the dual-frequency DC-DC converter of the present invention, the PWM DC-DC converter module operates at a switching frequency in the MHz range and dynamically coordinates and rapidly updates the duty cycle to compensate for and cancel the output ripple of the LLC resonant converter module. Therefore, the dual-frequency DC-DC converter has low output ripple characteristics.

[0060] 2. In the dual-frequency DC-DC converter of this invention, the LLC resonant converter module always operates at the resonant frequency. The power devices of the PWM DC-DC converter module are wide-bandgap devices with high switching frequency, low loss, and high junction temperature, and only transmit less than 20% of the power. The dual-frequency DC-DC converter has low loss. The PWM DC-DC converter module based on wide-bandgap devices operates at a MHz-level switching frequency, and the passive components and heat dissipation devices are small in size. Therefore, the dual-frequency DC-DC converter has high efficiency and high power density characteristics comparable to conventional LLC resonant converters.

[0061] 3. In the dual-frequency DC-DC converter of this invention, the PWM DC-DC converter module operating at a MHz-level switching frequency can achieve rapid adjustment of the output voltage by quickly changing the duty cycle. Therefore, the dual-frequency DC-DC converter has the advantages of a wide voltage regulation range and fast response speed. Attached Figure Description

[0062] Figure 1 This is a topology diagram of a dual-frequency DC-DC converter according to an embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of the operation of a dual-frequency DC-DC converter according to an embodiment of the present invention;

[0064] Figure 3 This is the equivalent circuit of a dual-frequency DC-DC converter according to an embodiment of the present invention;

[0065] Figure 4 This is a dynamic coordination control method for a dual-frequency DC-DC converter according to an embodiment of the present invention;

[0066] In the diagram, 1 is the LLC resonant converter module; 2 is the PWM DC-DC converter module; 1-1 is the chopper unit; 1-2 is the resonant circuit unit; 1-3 is the transformer unit; 1-4 is the first rectifier unit; and 1-5 is the second rectifier unit. Detailed Implementation

[0067] The following is in conjunction with the appendix Figure 1-4 The specific embodiments of the present invention will be described in detail below.

[0068] This invention provides a dual-frequency DC-DC converter, including an LLC resonant converter module 1 and a PWM DC-DC converter module 2. The input of the PWM DC-DC converter module 2 is cascaded with the secondary output of the LLC resonant converter module 1, and its output is connected in series with the main output of the LLC resonant converter module 1. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module 1, the output voltage of the secondary output of the LLC resonant converter module 1, and the output voltage of the PWM DC-DC converter module 2 satisfy the following relationship:

[0069]

[0070] in,

[0071] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0072] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0073] V o2 The output voltage of the LLC resonant converter module's secondary output;

[0074] V o1_ac This refers to the AC component of the output voltage of the main output of LLC resonant converter module 1;

[0075] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module 2.

[0076] V o1_dc This refers to the DC component of the output voltage of the main output of LLC resonant converter module 1;

[0077] V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module 2.

[0078] D represents the duty cycle of PWM DC-DC converter module 2.

[0079] The equivalent circuit of a dual-frequency DC-DC converter is as follows: Figure 3 As shown, the output of the dual-frequency DC-DC converter is formed by connecting the main output of LLC resonant converter module 1 and the output of PWM DC-DC converter module 2 in series. Therefore, its output voltage V... o Satisfy the following relationship

[0080] V o =V o3 +V o1

[0081] V o1_ac and Vo1_dc These represent the AC and DC components of the output voltage of the main output of LLC resonant converter module 1, respectively; V o3_ac and V o3_dc Let the AC and DC components of the output voltage of the LLC resonant converter module 1 be the output voltage, respectively. Then the output voltage of the dual-frequency DC-DC converter is:

[0082] V o =V o1_ac +V o1_dc +V o3_ac +V o3_dc

[0083] According to a specific embodiment of the present invention, the LLC resonant converter module 1 includes a chopper unit 1-1, a resonant circuit unit 1-2, a transformer unit 1-3, multiple rectifier units, an input filter capacitor, and multiple output filter capacitors; the transformer unit 1-3 is a multi-winding transformer; the chopper unit 1-1, the resonant circuit unit 1-2, and the transformer unit 1-3 are cascaded sequentially; the multiple rectifier units respectively rectify the multiple windings of the transformer unit 1-3; the input filter capacitor is connected in parallel with the input power supply; and the multiple output filter capacitors are respectively connected in parallel with the multiple rectifier units and the output of the PWM DC-DC converter module 2.

[0084] According to a specific embodiment of the present invention, the plurality of rectifier units include a first rectifier unit 1-4 and a second rectifier unit 1-5, and the secondary winding of the transformer unit 1-3 includes a main winding and a secondary winding, wherein the turns ratio of the main winding and the secondary winding satisfies N2≥N3;

[0085] N2 is the number of turns in the main winding;

[0086] N3 is the number of turns in the secondary winding.

[0087] According to a specific embodiment of the present invention, the main output voltage V of the LLC resonant converter module 1 is... o1 The output voltage V of the secondary output o2 The following relationship must be satisfied:

[0088]

[0089] According to a specific embodiment of the present invention, the chopper unit 1-1 in the LLC resonant converter module 1 is a half-bridge structure, a full-bridge structure, or a multi-level structure, wherein the power devices are silicon-based devices.

[0090] According to a specific embodiment of the present invention, such as Figure 1 As shown, in LLC resonant converter module 1, chopper unit 1-1 is a half-bridge structure, including power devices Q1 and Q2 connected in series; resonant circuit unit 1-2 includes resonant inductor L connected in series.r Magnetizing inductance L m and resonant capacitor C r The first rectifier unit 1-4 includes rectifier diodes D1 and D2, the second rectifier unit 1-5 includes rectifier diodes D3 and D4, and the input filter capacitor C... in The output filter capacitor C is connected in parallel with LLC resonant converter module 1. o1 With C o2 The main output and auxiliary output of LLC resonant converter module 1 are connected in parallel, and the transformer unit includes a multi-winding high-frequency transformer T1.

[0091] According to a specific embodiment of the present invention, the PWM DC-DC converter module 2 includes a DC-DC conversion unit, which is a Buck converter, a Buck-Boost converter, or a Cuk converter, wherein the power device is a wide bandgap device.

[0092] According to a specific embodiment of the present invention, such as Figure 1 As shown, the DC-DC converter unit is a Buck circuit, including power devices Q3 and Q4 and a power inductor L. o It operates in synchronous rectification mode, and the output filter capacitor C o3 It is connected in parallel with PWM DC-DC converter module 2.

[0093] This invention provides a dynamic coordination control method for any of the above-mentioned dual-frequency DC-DC converters, comprising:

[0094] LLC resonant converter module 1 operates in open loop at a kHz-level switching frequency and always operates at the resonant frequency point. After PFM modulation, it controls the turn-on and turn-off of the power devices in chopper unit 1-1.

[0095] The PWM DC-DC converter module 2 operates at a MHz-level switching frequency, transmits less than 20% of the power, and dynamically coordinates and compensates for the output harmonics of the LLC resonant converter module 1 to achieve low output ripple of the dual-frequency DC-DC converter.

[0096] PWM DC-DC converter module 2 based on the detected V o1 V o2 and I o2 The duty cycle of the next switching cycle of the PWM DC-DC converter module 2 is predicted. Through PWM modulation, the switching on and off of the power devices in the DC-DC converter unit is controlled, thereby regulating the output voltage of the PWM DC-DC converter module 2 to achieve the desired voltage V. o3_ac With V o1_ac They cancel each other out to satisfy the following relationship

[0097] Vo1_ac +V o3_ac =0

[0098] This makes the output voltage V of the dual-frequency DC-DC converter o Contains only the DC component to satisfy the following relationship

[0099] V o =V o1_dc +V o3_dc

[0100] in,

[0101] I o2 This is the output current of the LLC resonant converter module 1.

[0102] According to a specific embodiment of the present invention, the PWM DC-DC converter module 2 determines the voltage based on the detected V. o1 and V o2 The increase in output current ΔI of PWM DC-DC converter module 2 within one switching cycle is obtained. o2_up and decrease value ΔI o2_down for

[0103]

[0104] in,

[0105] T s Indicates the switching cycle;

[0106] L o This is the power inductor for PWM DC-DC converter module 2.

[0107] According to a specific embodiment of the present invention, the PWM DC-DC converter module 2 determines the I based on the detected I o2 The increase in output voltage ΔV of PWM DC-DC converter module 2 during one switching cycle is obtained. o2_up and decrease value ΔV o2_down for

[0108]

[0109] in,

[0110] R L For load;

[0111] C o3 This is the output capacitor of the DC-DC converter module.

[0112] According to a specific embodiment of the present invention, the PWM DC-DC converter module 2 determines the voltage based on the detected V. o1 Vo2 and I o2 The predicted duty cycle D for the next switching cycle is:

[0113]

[0114] in,

[0115] ΔV o3 The voltage error of PWM DC-DC converter module 2 satisfies the following relationship

[0116] ΔV o3 =V o * -V' o -(V o1(k) -V o1(k-1) )

[0117] in,

[0118] V o * represents the given value of the output voltage of the dual-frequency DC-DC converter;

[0119] V' o This is the feedback value of the output voltage of the dual-frequency DC-DC converter;

[0120] V o1(k) -V o1(k-1) The voltage difference between the main output voltage of LLC resonant converter module 1 at time K and time K-1 is used as the predicted value of the main output voltage of LLC resonant converter module 1 in the next switching cycle.

[0121] According to a specific embodiment of the present invention, the power transfer coefficient K1 of the main output of LLC resonant converter module 1 and the power transfer coefficient K2 of the secondary output of LLC resonant converter module 1 in the dual-frequency DC-DC converter satisfy the following relationship:

[0122]

[0123] in,

[0124] P1 represents the power transmitted by the main output of LLC resonant converter module 1;

[0125] P2 represents the power transmitted from the sub-output of LLC resonant converter module 1;

[0126] P in This refers to the input power.

[0127] N2 / N3≥0.8, and If K1≥0.8, then more than 80% of the power is handled by the main output of LLC resonant converter module 1, and the structure of LLC resonant converter module sub-output cascaded with PWM DC-DC converter module 2 only transmits less than 20% of the power.

[0128] The formula for calculating the efficiency η of a dual-frequency DC-DC converter is as follows:

[0129] η = K1·η1 + K2·η1·η2

[0130] in,

[0131] η1 is the efficiency of LLC resonant converter module 1;

[0132] η2 represents the efficiency of PWM DC-DC converter module 2.

[0133] Although the two-stage cascaded structure has low power transmission efficiency, this portion of power accounts for a small proportion. The efficiency of the dual-frequency DC-DC converter is mainly determined by the efficiency of the main output of LLC resonant converter module 1. Since LLC resonant converter module 1 always operates at its resonant frequency, it achieves soft switching of the power devices in chopper unit 1-1. Therefore, the dual-frequency DC-DC converter has high efficiency characteristics comparable to the LLC resonant converter. A schematic diagram of the dual-frequency DC-DC converter's operation is shown below. Figure 2 As shown.

[0134] Example 1

[0135] According to a specific embodiment of the present invention, the dual-frequency DC-DC converter of the present invention will be described in detail below.

[0136] This invention provides a dual-frequency DC-DC converter, including an LLC resonant converter module 1 and a PWM DC-DC converter module 2. The input of the PWM DC-DC converter module 2 is cascaded with the secondary output of the LLC resonant converter module 1, and its output is connected in series with the main output of the LLC resonant converter module 1. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module 1, the output voltage of the secondary output of the LLC resonant converter module 1, and the output voltage of the PWM DC-DC converter module 2 satisfy the following relationship:

[0137]

[0138] in,

[0139] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0140] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0141] V o2 The output voltage of the LLC resonant converter module's secondary output;

[0142] V o1_ac This refers to the AC component of the output voltage of the main output of LLC resonant converter module 1;

[0143] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module 2.

[0144] V o1_dc This refers to the DC component of the output voltage of the main output of LLC resonant converter module 1;

[0145] V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module 2.

[0146] D represents the duty cycle of PWM DC-DC converter module 2.

[0147] Example 2

[0148] According to a specific embodiment of the present invention, the dual-frequency DC-DC converter of the present invention will be described in detail below.

[0149] This invention provides a dual-frequency DC-DC converter, including an LLC resonant converter module 1 and a PWM DC-DC converter module 2. The input of the PWM DC-DC converter module 2 is cascaded with the secondary output of the LLC resonant converter module 1, and its output is connected in series with the main output of the LLC resonant converter module 1. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module 1, the output voltage of the secondary output of the LLC resonant converter module 1, and the output voltage of the PWM DC-DC converter module 2 satisfy the following relationship:

[0150]

[0151] in,

[0152] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0153] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0154] V o2 The output voltage of the LLC resonant converter module's secondary output;

[0155] V o1_ac This refers to the AC component of the output voltage of the main output of LLC resonant converter module 1;

[0156] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module 2.

[0157] V o1_dc This refers to the DC component of the output voltage of the main output of LLC resonant converter module 1;

[0158] V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module 2.

[0159] D represents the duty cycle of PWM DC-DC converter module 2.

[0160] LLC resonant converter module 1 includes chopper unit 1-1, resonant circuit unit 1-2, transformer unit 1-3, multiple rectifier units, input filter capacitors, and multiple output filter capacitors; transformer unit 1-3 is a multi-winding transformer; chopper unit 1-1, resonant circuit unit 1-2, and transformer unit 1-3 are cascaded sequentially; multiple rectifier units respectively rectify multiple windings of transformer unit 1-3; the input filter capacitor is connected in parallel with the input power supply; and multiple output filter capacitors are connected in parallel with multiple rectifier units and the output of PWM DC-DC converter module 2, respectively.

[0161] Example 3

[0162] According to a specific embodiment of the present invention, the dual-frequency DC-DC converter of the present invention will be described in detail below.

[0163] This invention provides a dual-frequency DC-DC converter, including an LLC resonant converter module 1 and a PWM DC-DC converter module 2. The input of the PWM DC-DC converter module 2 is cascaded with the secondary output of the LLC resonant converter module 1, and its output is connected in series with the main output of the LLC resonant converter module 1. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module 1, the output voltage of the secondary output of the LLC resonant converter module 1, and the output voltage of the PWM DC-DC converter module 2 satisfy the following relationship:

[0164]

[0165] in,

[0166] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0167] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0168] V o2The output voltage of the LLC resonant converter module's secondary output;

[0169] V o1_ac This refers to the AC component of the output voltage of the main output of LLC resonant converter module 1;

[0170] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module 2.

[0171] V o1_dc This refers to the DC component of the output voltage of the main output of LLC resonant converter module 1;

[0172] V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module 2.

[0173] D represents the duty cycle of PWM DC-DC converter module 2.

[0174] LLC resonant converter module 1 includes chopper unit 1-1, resonant circuit unit 1-2, transformer unit 1-3, multiple rectifier units, input filter capacitors, and multiple output filter capacitors; transformer unit 1-3 is a multi-winding transformer; chopper unit 1-1, resonant circuit unit 1-2, and transformer unit 1-3 are cascaded sequentially; multiple rectifier units respectively rectify multiple windings of transformer unit 1-3; the input filter capacitor is connected in parallel with the input power supply; and multiple output filter capacitors are connected in parallel with multiple rectifier units and the output of PWM DC-DC converter module 2, respectively.

[0175] Multiple rectifier units include a first rectifier unit 1-4 and a second rectifier unit 1-5. The secondary winding of transformer unit 1-3 includes a main winding and a secondary winding. The turns ratio of the main winding to the secondary winding satisfies N2≥N3.

[0176] N2 is the number of turns in the main winding;

[0177] N3 is the number of turns in the secondary winding.

[0178] Example 4

[0179] According to a specific embodiment of the present invention, the dual-frequency DC-DC converter of the present invention will be described in detail below.

[0180] This invention provides a dual-frequency DC-DC converter, including an LLC resonant converter module 1 and a PWM DC-DC converter module 2. The input of the PWM DC-DC converter module 2 is cascaded with the secondary output of the LLC resonant converter module 1, and its output is connected in series with the main output of the LLC resonant converter module 1. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module 1, the output voltage of the secondary output of the LLC resonant converter module 1, and the output voltage of the PWM DC-DC converter module 2 satisfy the following relationship:

[0181]

[0182] in,

[0183] V o This refers to the output voltage of the dual-frequency DC-DC converter.

[0184] V o1 This refers to the output voltage of the main output of the LLC resonant converter module.

[0185] V o2 The output voltage of the LLC resonant converter module's secondary output;

[0186] V o1_ac This refers to the AC component of the output voltage of the main output of LLC resonant converter module 1;

[0187] V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module 2.

[0188] V o1_dc This refers to the DC component of the output voltage of the main output of LLC resonant converter module 1;

[0189] V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module 2.

[0190] D represents the duty cycle of PWM DC-DC converter module 2.

[0191] LLC resonant converter module 1 includes chopper unit 1-1, resonant circuit unit 1-2, transformer unit 1-3, multiple rectifier units, input filter capacitors, and multiple output filter capacitors; transformer unit 1-3 is a multi-winding transformer; chopper unit 1-1, resonant circuit unit 1-2, and transformer unit 1-3 are cascaded sequentially; multiple rectifier units respectively rectify multiple windings of transformer unit 1-3; the input filter capacitor is connected in parallel with the input power supply; and multiple output filter capacitors are connected in parallel with multiple rectifier units and the output of PWM DC-DC converter module 2, respectively.

[0192] Multiple rectifier units include a first rectifier unit 1-4 and a second rectifier unit 1-5. The secondary winding of transformer unit 1-3 includes a main winding and a secondary winding. The turns ratio of the main winding to the secondary winding satisfies N2≥N3.

[0193] N2 is the number of turns in the main winding;

[0194] N3 is the number of turns in the secondary winding.

[0195] The main output voltage of LLC resonant converter module 1 is V. o1 The output voltage V of the secondary output o2 The following relationship must be satisfied:

[0196]

[0197] In LLC resonant converter module 1, chopper unit 1-1 has a half-bridge structure, including power devices Q1 and Q2 connected in series, both of which are silicon-based devices; resonant circuit unit 1-2 includes a resonant inductor L connected in series. r Magnetizing inductance L m and resonant capacitor C r The first rectifier unit 1-4 includes rectifier diodes D1 and D2, the second rectifier unit 1-5 includes rectifier diodes D3 and D4, and the input filter capacitor C... in The output filter capacitor C is connected in parallel with LLC resonant converter module 1. o1 With C o2 The main output and auxiliary output of LLC resonant converter module 1 are connected in parallel, and the transformer unit includes a multi-winding high-frequency transformer T1.

[0198] PWM DC-DC converter module 2 includes a DC-DC conversion unit, which is a Buck circuit. Power devices Q3 and Q4 are wide-bandgap devices operating in synchronous rectification mode. o For power inductance, C o3 This is the output filter capacitor for PWM DC-DC converter module 2.

[0199] Example 5

[0200] According to a specific embodiment of the present invention, the dynamic coordination control method of the dual-frequency DC-DC converter of the present invention will be described in detail below. The dynamic coordination control method of the dual-frequency DC-DC converter is as follows: Figure 4 As shown, it includes model predictive control, PWM module and PFM module.

[0201] The LLC resonant converter module operates in open loop at a switching frequency in the kHz range, and always operates at the resonant frequency, i.e., satisfying fs = f rAfter PFM modulation, the on / off state of Q1 and Q2 is controlled;

[0202] The PWM DC-DC converter module operates at a switching frequency in the MHz range and delivers less than 20% of its power. The PWM DC-DC converter module adjusts its power delivery based on the detected V... o1 V o2 and I o2 Based on the model predictive control algorithm, the duty cycle of the next switching cycle is predicted. Through PWM modulation, the on / off state of Q3 and Q4 is controlled, achieving rapid adjustment of the output voltage of the PWM DC-DC converter module, thus enabling V... o3_ac With V o1_ac They cancel each other out to satisfy the following relationship

[0203] V o1_ac +V o3_ac =0

[0204] This makes the output voltage V of the dual-frequency DC-DC converter o It contains only a DC component to achieve low output ripple, satisfying the following relationship.

[0205] V o =V o1_dc +V o3_dc

[0206] Based on the detected V o1 V o2 The increase in output current ΔI of the DC-DC converter module within one switching cycle is obtained. o2_up and decrease value ΔI o2_down for

[0207]

[0208] in,

[0209] T s Indicates the switching cycle;

[0210] L o For the power inductor of the PWM DC-DC converter module;

[0211] According to the detected I o2 The increase in output voltage ΔV of the PWM DC-DC converter module within one switching cycle is obtained. o2_up and decrease value ΔV o2_down for

[0212]

[0213] in,

[0214] R LFor load;

[0215] C o3 This is the output capacitor of the DC-DC converter module.

[0216] PWM DC-DC converter module 2 based on the detected V o1 V o2 and I o2 The duty cycle D of the next switching cycle is predicted to be...

[0217]

[0218] in,

[0219] ΔV o3 The voltage error of PWM DC-DC converter module 2 satisfies the following relationship

[0220]

[0221] in,

[0222] V o * represents the given value of the output voltage of the dual-frequency DC-DC converter;

[0223] V' o This is the feedback value of the output voltage of the dual-frequency DC-DC converter;

[0224] V o1(k) -V o1(k-1) The voltage difference between the main output voltage of LLC resonant converter module 1 at time K and time K-1 is used as the predicted value of the main output voltage of LLC resonant converter module 1 in the next switching cycle.

[0225] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A dynamic coordination control method for a dual-frequency DC-DC converter, characterized in that, include: The LLC resonant converter module operates in open loop at a kHz-level switching frequency and always operates at the resonant frequency point. After PFM modulation, it controls the turn-on and turn-off of the power devices in the chopper unit. The PWM DC-DC converter module operates at a switching frequency in the MHz range, transmits less than 20% of the power, and dynamically coordinates and compensates for the ripple of the main output of the LLC resonant converter module. The PWM DC-DC converter module detects... V o1 , V o2 and I o2 The system predicts the duty cycle of the next switching cycle of the PWM DC-DC converter module, controls the switching on and off of the power devices in the DC-DC converter unit through PWM modulation, and regulates the output voltage of the PWM DC-DC converter module to achieve the desired effect. V o3_ac and V o1_ac They cancel each other out to satisfy the following relationship This makes the output voltage of the dual-frequency DC-DC converter V o Contains only the DC component to satisfy the following relationship in, I o2 This refers to the output current of the LLC resonant converter module's secondary output. The dual-frequency DC-DC converter includes an LLC resonant converter module and a PWM DC-DC converter module. The input of the PWM DC-DC converter module is cascaded with the secondary output of the LLC resonant converter module, and its output is connected in series with the main output of the LLC resonant converter module. The output voltage of the dual-frequency DC-DC converter, the output voltage of the main output of the LLC resonant converter module, the output voltage of the secondary output of the LLC resonant converter module, and the output voltage of the PWM DC-DC converter module satisfy the following relationship: in, V o This refers to the output voltage of the dual-frequency DC-DC converter. V o1 This refers to the output voltage of the main output of the LLC resonant converter module. V o2 The output voltage of the LLC resonant converter module's secondary output; V o1_ac This refers to the AC component of the output voltage of the main output of the LLC resonant converter module. V o3_ac This refers to the AC component of the output voltage of the PWM DC-DC converter module. V o1_dc This refers to the DC component of the output voltage of the main output of the LLC resonant converter module. V o3_dc This refers to the DC component of the output voltage of the PWM DC-DC converter module. D This represents the duty cycle of the PWM DC-DC converter module.

2. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 1, characterized in that, The PWM DC-DC converter module detects... V o1 and V o2 The increase in output current Δ of the PWM DC-DC converter module within one switching cycle is obtained. I o2_up and decrease value Δ I o2_down for in, T s Indicates the switching cycle; L o This is the power inductor for the PWM DC-DC converter module.

3. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 2, characterized in that, The PWM DC-DC converter module detects... I o2 The increase in output voltage Δ of the PWM DC-DC converter module during one switching cycle is obtained. V o2_up and decrease value Δ V o2_down for in, R L For load; C o3 This is the output capacitor of the DC-DC converter module.

4. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 3, characterized in that, The PWM DC-DC converter module detects... V o1 , V o2 and I o2 The predicted duty cycle D for the next switching cycle is: in, Δ V o3 For the voltage error of the PWM DC-DC converter module, the following relationship must be satisfied. in, V o * represents the given value of the output voltage of the dual-frequency DC-DC converter; This is the feedback value of the output voltage of the dual-frequency DC-DC converter; V o1(k) - V o1(k-1) The voltage difference between the main output voltage of the LLC resonant converter module at time K and time K-1 is used as the predicted value of the main output voltage of the LLC resonant converter module in the next switching cycle.

5. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 1, characterized in that, The LLC resonant converter module includes a chopper unit, a resonant circuit unit, a transformer unit, multiple rectifier units, an input filter capacitor, and multiple output filter capacitors. The transformer unit is a multi-winding transformer. The chopper unit, resonant circuit unit, and transformer unit are cascaded sequentially. Multiple rectifier units rectify multiple windings of the transformer unit respectively. The input filter capacitor is connected in parallel with the input power supply. Multiple output filter capacitors are connected in parallel with the outputs of multiple rectifier units and the PWM DC-DC converter module respectively.

6. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 5, characterized in that, Multiple rectifier units include a first rectifier unit and a second rectifier unit. The secondary winding of the transformer unit includes a main winding and a secondary winding. The turns ratio of the main winding and the secondary winding satisfies N2≥N3. N2 is the number of turns in the main winding; N3 is the number of turns in the secondary winding.

7. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 6, characterized in that, The main output voltage of the LLC resonant converter module V o1 Output voltage of the secondary output V o2 The following relationship must be satisfied: 。 8. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 5, characterized in that, The chopper unit in the LLC resonant converter module is a half-bridge structure, a full-bridge structure, or a multi-level structure, and the power devices are silicon-based devices.

9. The dynamic coordination control method for a dual-frequency DC-DC converter according to claim 5, characterized in that, The PWM DC-DC converter module includes a DC-DC converter unit, which can be a Buck converter, a Buck-Boost converter, or a Cuk converter, wherein the power devices are wide-bandgap devices.

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