Turn ratio optimization method of integrated three-phase Boost-LLC topology

Abstract

The invention discloses a turn ratio optimization method of an integrated three-phase Boost-LLC topology. The turn ratio optimization method comprises the following steps: acquiring a positive peak value and a negative peak value of Boost chopping inductive current; according to the positive peak value and the negative peak value, obtaining an effective value of the chopping inductive current; obtaining resonance current peak values of a Boost primary side and a Boost secondary side; according to the resonance current peak value, resonance current effective values of a primary side and a secondary side are obtained; when the output voltage is fixed, inductance values under different turn ratios are calculated; and according to the effective value of the chopping inductive current, the effective value of the resonance current and the inductance values under different turn ratios, obtaining the turn ratio with the minimum loss. According to the method, the problem that the turn ratio in the integrated three-phase Boost-LLC topology is difficult to design scientifically and efficiently is solved.

Description

Technical Field

[0001] The present invention belongs to the field of isolated DC-DC converters, and particularly relates to a turn ratio optimization method for integrating a three-phase Boost-LLC topology. Background Art

[0002] To improve the system power density, the switching frequency of devices can usually be increased to reduce the volume of passive components. However, the higher the switching frequency, the greater the switching loss. To achieve high-efficiency and high-power-density conversion, LLC is used because it can achieve soft switching of primary and secondary devices. To increase the power capacity and reduce the current ripple, three-phase interleaved LLC is widely used. At the same time, to broaden the voltage regulation range and simplify synchronous rectification, an integrated three-phase Boost-LLC topology is proposed. However, the turn ratio of its transformer affects various performances of the converter, and there is no scientific and reasonable specification for turn ratio design. Therefore, there is an urgent need for a turn ratio optimization method for integrating a three-phase Boost-LLC topology. Summary of the Invention

[0003] To solve the above technical problems, the present invention proposes a turn ratio optimization method for integrating a three-phase Boost-LLC topology, which can solve the problem that it is difficult to design the turn ratio scientifically and efficiently in the integrated three-phase Boost-LLC topology.

[0004] To achieve the above object, the present invention provides a turn ratio optimization method for integrating a three-phase Boost-LLC topology, including:

[0005] Obtaining the positive peak value and negative peak value of the Boost chopper inductor current;

[0006] Obtaining the effective value of the chopper inductor current according to the positive peak value and negative peak value;

[0007] Obtaining the peak values of the resonant currents of the Boost primary side and secondary side;

[0008] Obtaining the effective values of the resonant currents of the primary side and secondary side according to the peak values of the resonant currents;

[0009] When the output voltage is fixed, calculating the inductance values at different turn ratios;

[0010] Obtaining the turn ratio with the minimum loss according to the effective value of the chopper inductor current, the effective value of the resonant current, and the inductance values at different turn ratios.

[0011] Optionally, the method for obtaining the positive peak value of the Boost chopper inductor current is:

[0012]

[0013] Wherein, I L_p is the positive peak value of the Boost chopper inductor current, Vin is the input voltage, f r is the resonance frequency, D is the duty cycle, and P is the input power;

[0014] The method for obtaining the negative peak value of the Boost chopper inductor current is:

[0015]

[0016] where I L_n is the negative peak value of the Boost chopper inductor current.

[0017] Optionally, the method for obtaining the effective value of the chopper inductor current is:

[0018]

[0019] where I L_rms is the effective value of the Boost chopper inductor current.

[0020] Optionally, the method for obtaining the peak value of the resonance current on the secondary side of the Boost is:

[0021]

[0022] where I s_pk is the peak value of the resonance current of the Y-connected secondary side, I o is the output current, D is the duty cycle, and x is the integration variable;

[0023] The method for obtaining the peak value of the resonance current on the primary side of the Boost is:

[0024] I p_pk = I s_pk / n

[0025] where I p_pk is the peak value of the resonance current of the Y-connected primary side, and n is the transformer turns ratio.

[0026] Optionally, the method for obtaining the effective value of the resonance current on the secondary side is:

[0027]

[0028] where I s_rms is the effective value of the resonance current of the Y-connected secondary side;

[0029] The method for obtaining the effective value of the resonance current on the primary side is:

[0030] I p_rms = I s_rms / n

[0031] where I p_rms is the effective value of the resonance current of the Y-connected primary side.

[0032] Optionally, the method for calculating the inductance value at different turns ratios is as follows:

[0033]

[0034] where L is the Boost chopper inductance value, t d is the dead-time value for achieving soft switching, V i is the input voltage, f r is the resonant frequency, D is the duty cycle, P is the input power, f s is the resonant frequency, C p is the junction capacitance of the primary side switching transistor, C s is the junction capacitance of the secondary side switching transistor, and n is the transformer turns ratio.

[0035] Optionally, obtaining the turns ratio with the minimum loss includes:

[0036] Obtaining the minimum loss according to the effective value of the chopper inductor current, the effective value of the resonant current, and the inductance value at different turns ratios;

[0037] Obtaining the turns ratio with the minimum loss according to the minimum loss.

[0038] Optionally, the method for obtaining the minimum loss is as follows:

[0039] P sw_con_p = 3(I L_rms 2 + I p_rms 2 )R dson_p

[0040] P sw_con_s = 3I s_rms 2 R dson_s

[0041] where P sw_con_p is the conduction loss of the primary side switching transistor, P sw_con_s is the conduction loss of the secondary side switching transistor, I L_rms is the effective value of the Boost chopper inductor current, I p_rms is the effective value of the primary side Y-connected resonant current, I s_rms is the effective value of the secondary side Y-connected resonant current, and R dson_s is the on-resistance of the secondary side switching transistor.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] 1. By optimizing the transformer turns ratio design, the present invention can achieve the minimum device loss and improve the efficiency;

[0044] 2. The method principle of the present invention is simple, easy to implement, and highly feasible;

[0045] 3. The present invention solves the problem that it is difficult to scientifically and efficiently design the turns ratio in the integrated three-phase Boost-LLC topology. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0047] Figure 1 is a flowchart of a method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to an embodiment of the present invention;

[0048] Figure 2 is the circuit structure diagram of a three-phase integrated Boost-LLC converter according to an embodiment of the present invention;

[0049] Figure 3 is the loss calculation result diagram under each turns ratio according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine with the embodiments to detail this application.

[0051] It should be noted that the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0052] The present invention proposes a method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology, as Figure 1 shown, specifically including the following steps:

[0053] Obtain the positive peak value and negative peak value of the Boost chopper inductor current;

[0054] Obtain the effective value of the chopper inductor current according to the positive peak value and negative peak value;

[0055] Obtain the peak values of the resonant currents on the primary and secondary sides of the Boost;

[0056] Obtain the effective values of the resonant currents on the primary and secondary sides according to the peak values of the resonant currents;

[0057] When the output voltage is fixed, calculate the inductance values under different turns ratios;

[0058] Obtain the turns ratio with the minimum loss based on the effective value of the chopping inductor current, the effective value of the resonant current, and the inductor values under different turns ratios.

[0059] Specifically, the circuit structure diagram of the three-phase integrated Boost-LLC converter is as Figure 2 shown, and its turns ratio optimization method specifically includes:

[0060] Step 1, calculate the positive peak value and negative peak value of the Boost chopping inductor current according to the power, duty cycle, and input voltage;

[0061] Step 2, calculate the effective value of the current according to the Boost chopping inductor current waveform and its positive and negative peak values;

[0062] Step 3, calculate the peak value and effective value of the resonant current of the primary and secondary Y-type connections according to the charge balance;

[0063] Step 4, calculate the different bus voltages, different duty cycles, different switching frequencies, and the maximum achievable soft-switching Boost chopping inductor under different turns ratios when the output voltage is fixed;

[0064] Step 5, calculate the device losses under different turns ratios under the given operating conditions and device parameters, and select the turns ratio that minimizes the losses.

[0065] Furthermore, the method for obtaining the positive peak value of the Boost chopping inductor current is:

[0066]

[0067] where I L_p is the positive peak value of the Boost chopping inductor current, V in is the input voltage, f r is the resonant frequency, D is the duty cycle, and P is the input power;

[0068] The method for obtaining the negative peak value of the Boost chopping inductor current is:

[0069]

[0070] where I L_n is the negative peak value of the Boost chopping inductor current.

[0071] Furthermore, the method for obtaining the effective value of the chopping inductor current is:

[0072]

[0073] where I L_rms is the effective value of the Boost chopping inductor current.

[0074] Further, the method for obtaining the peak value of the resonant current on the secondary side of Boost is as follows:

[0075]

[0076] where I s_pk is the peak value of the resonant current of the Y-connected secondary side, I o is the output current, D is the duty cycle, and x is the integration variable;

[0077] The method for obtaining the peak value of the resonant current on the primary side of Boost is as follows:

[0078] I p_pk = I s_pk / n

[0079] where I p_pk is the peak value of the resonant current of the Y-connected primary side, and n is the transformer turns ratio.

[0080] Further, the method for obtaining the rms value of the resonant current on the secondary side is as follows:

[0081]

[0082] where I s_rms is the rms value of the resonant current of the Y-connected secondary side;

[0083] The method for obtaining the rms value of the resonant current on the primary side is as follows:

[0084] I p_rms = I s_rms / n (6)

[0085] where I p_rms is the rms value of the resonant current of the Y-connected primary side.

[0086] Further, the method for calculating the inductance value at different turns ratios is as follows:

[0087]

[0088] where L is the Boost chopper inductance value, t d is the dead-time value for realizing soft switching, V i is the input voltage, f r is the resonant frequency, P is the input power, f s is the resonant frequency, C p is the junction capacitance of the primary-side switch, C s is the junction capacitance of the secondary-side switch, n is the transformer turns ratio, G tot is the total circuit gain, D is the duty cycle, and the duty cycle under the input and output voltages is calculated according to formula (8).

[0089] Further, obtaining the turns ratio with the minimum loss includes:

[0090] Obtaining the minimum loss according to the effective value of the chopping inductor current, the effective value of the resonant current, and the inductance values under different turns ratios;

[0091] Obtaining the turns ratio with the minimum loss according to the minimum loss.

[0092] Further, calculating the minimum loss according to Table 1:

[0093] P sw_con_p = 3(I L_rms 2 + I p_rms 2 )R dson_p (10)

[0094] P sw_con_s = 3I s_rms 2 R dson_s (11)

[0095] wherein, P sw_con_p is the conduction loss of the primary side switching transistor, P sw_con_s is the conduction loss of the secondary side switching transistor, I L_rms is the effective value of the Boost chopping inductor current, I p_rms is the effective value of the primary side Y-connected resonant current, I s_rms is the effective value of the secondary side Y-connected resonant current, and R dson_s is the device conduction resistance.

[0096] Table 1

[0097]

[0098]

[0099] According to Figure 3 the turns ratio with the minimum loss n = 4 can be selected.

[0100] The above is only the preferred specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A turns ratio optimization method for an integrated three-phase Boost-LLC topology, characterized in that: include: Get the positive peak value and negative peak value of the Boost chopper inductor current; Obtaining an effective value of the chopping inductor current according to the positive peak value and the negative peak value; Get the peak value of the resonant current of the primary and secondary sides of Boost; According to the resonant current peak value, obtaining the resonant current effective value of the primary side and the secondary side; When the output voltage is fixed, calculate the inductance value under different turns ratios; The turns ratio with minimum loss is obtained according to the effective value of the chopping inductor current, the effective value of the resonant current and the inductance values ​​under different turns ratios.

2. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 1, characterized in that: The method for obtaining the positive peak value of the Boost chopper inductor current is: Among them, I L_p is the positive peak value of the Boost chopper inductor current, V i is the input voltage, f r is the resonant frequency, D is the duty cycle, and P is the input power; The method for obtaining the negative peak value of the Boost chopper inductor current is: Among them, I L_n is the negative peak value of the Boost chopping inductor current.

3. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 2, characterized in that: The method for obtaining the effective value of the chopping inductor current is: Among them, I L_rms is the effective value of the Boost chopper inductor current.

4. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 1, characterized in that: The method to obtain the resonant current peak value of the Boost secondary side is: Among them, I s_pk is the secondary side Y-type connection resonant current peak value, I o is the output current, D is the duty cycle, and x is the integral variable; The method to obtain the peak value of the resonant current of the Boost primary side is: I p_pk =I s_pk / n Among them, I p_pk is the peak value of the primary Y-type connection resonant current, and n is the transformer turns ratio.

5. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 4, characterized in that: The method for obtaining the effective value of the resonant current of the secondary side is: Among them, I s_rms is the effective value of the secondary Y-type connection resonant current; The method for obtaining the effective value of the primary resonant current is: I p_rms =I s_rms / n Among them, I p_rms It is the effective value of the primary Y-type connection resonant current.

6. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 1, characterized in that: The method to calculate the inductance value under different turns ratios is: Where, L is the Boost chopper inductor value, t d To achieve the dead zone value of soft switching, V i is the input voltage, f r is the resonant frequency, D is the duty cycle, P is the input power, f s is the resonant frequency, C p is the junction capacitance of the primary switch tube, C s is the junction capacitance of the secondary switch tube, and n is the transformer turns ratio.

7. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 1, characterized in that: The turns ratio for minimum loss is: Obtaining minimum switching device loss according to the effective value of the chopping inductor current, the effective value of the resonant current and the inductance values ​​under different turns ratios; According to the minimum loss, a turns ratio with minimum loss is obtained.

8. The method for optimizing the turns ratio of an integrated three-phase Boost-LLC topology according to claim 7, characterized in that: The method to obtain the minimum loss is: P sw_con_p =3(I L_rms 2 +I p_rms 2 )R dson_p P sw_con_s =3I s_rms 2 R dson_s Among them, P sw_con_p is the conduction loss of the primary switch tube, P sw_con_s is the conduction loss of the secondary switch, I L_rms is the effective value of the Boost chopper inductor current, I p_rms is the effective value of the primary Y-type connection resonant current, I s_rms is the effective value of the secondary Y-type connection resonant current, R dson_s is the on-resistance of the device.

Images