LLC resonant converter derating control method

Abstract

The invention relates to an LLC resonant converter derating control method, and the method comprises the steps: selecting a real-time output current corresponding to a real-time output voltage on a real-time output voltage-real-time output current curve based on the real-time output voltage, and calculating target output power based on the real-time output current and a rated output voltage, controlling the actual output power of the LLC resonant converter to track the target output power so as to realize derating control of the LLC resonant converter; the real-time output voltage-real-time output current curve is formed by fitting an input voltage parameter, a temperature parameter, an output voltage parameter and an output current parameter of the LLC resonant converter, so that the complex coupling relationship of the influence of the input voltage and the temperature on a power device of the LLC resonant converter can be finely and linearly reflected; therefore, derating control of smooth and optimal power control can be realized.

Description

A Derating Control Method for LLC Resonant Converters Technical Field

[0001] This invention relates to the field of LLC resonant cavities, and more specifically, to a derating control method for LLC resonant converters. Background Technology

[0002] LLC resonant converters are widely used in medium-to-high power applications such as communication power supplies, server power supplies, and electric vehicle charging modules due to their high efficiency and soft-switching characteristics. In practical applications, LLC resonant converters often operate under high-voltage input and high-temperature environments. Traditional derating strategies typically derating based on only a single factor, either operating temperature or input voltage. For example, output power is only reduced linearly or stepwise when the temperature exceeds a certain threshold. This strategy fails to comprehensively consider the additional electrical stresses (such as voltage stress and current stress) that increased input voltage places on power devices (such as main switching transistors, resonant capacitors, and transformers).

[0003] While some have proposed derating based on input voltage and temperature, existing derating methods are simply a superposition of these two factors. In reality, the effects of input voltage and temperature on device stress are not simply additive but involve complex coupling relationships. Therefore, current derating control methods for LLC resonant converters cannot achieve smooth, optimal power control derating. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a derating control method for LLC resonant converters that can achieve smooth and optimal power control derating, in view of the above-mentioned defects of the prior art.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A derating control method for an LLC resonant converter is constructed, comprising: when the LLC resonant converter meets the derating condition, selecting the real-time output current corresponding to the real-time output voltage on the real-time output voltage-real-time output current curve based on the real-time output voltage; calculating the target output power based on the real-time output current and the rated output voltage; and controlling the actual output power of the LLC resonant converter to track the target output power to achieve derating control of the LLC resonant converter; wherein, the real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter.

[0006] In the LLC resonant converter derating control method of the present invention, the input voltage parameters include real-time input voltage, a first input voltage derating point, a second input voltage derating point, and a maximum input voltage; the temperature parameters include real-time sampling temperature and a temperature derating point; the output voltage parameters include real-time output voltage, a first output voltage derating point, a second output voltage derating point, a third output voltage derating point, and a fourth output voltage derating point; the output current parameters include a first output current, a second output current, a third output current, and a fourth output current; the first output current is the output current where the real-time output voltage is at the first output voltage derating point, the second output current is the output current where the real-time output voltage is at the second output voltage derating point, the third output current is the output current where the real-time output voltage is at the third output voltage derating point, and the fourth output current is the output current where the real-time output voltage is at the fourth output voltage derating point.

[0007] In the LLC resonant converter derating control method of the present invention, the real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter, including: calculating the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point; and calculating the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, and the fourth output current based on the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, and the third output current. The system obtains a first boundary point, a second boundary point, a third boundary point, and a fourth boundary point by using the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; and fits the real-time output voltage-real-time output current curve based on the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; wherein the ordinate of the first boundary point is the first output current, and the abscissa is the first output voltage derating point; the ordinate of the second boundary point is the second output current, and the abscissa is the second output voltage derating point; the ordinate of the third boundary point is the third output current, and the abscissa is the third output voltage derating point; and the ordinate of the fourth boundary point is the fourth output current, and the abscissa is the fourth output voltage derating point.

[0008] In the LLC resonant converter derating control method of the present invention, the calculation of the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point includes: calculating the first output current, the second output current, the third output current, and the fourth output current based on the following formula:

[0009]

[0010]

[0011]

[0012] Wherein, I1max represents the first output current, Vin represents the real-time input voltage, Vin1 represents the first input voltage derating point, Vin2 represents the second input voltage derating point, Vinmax represents the maximum input voltage; Tin represents the real-time sampling temperature, Tde represents the temperature derating point; I2(Vin, Tin) represents the second output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I3(Vin, Tin) represents the third output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I4(Vin, Tin) represents the fourth output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; Poutmax represents the maximum output power; V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; k1, k2, k3, k4, k5, and k6 represent the fitting coefficients.

[0013] In the LLC resonant converter derating control method described in this invention, the real-time output voltage-real-time output current curve satisfies the following formula:

[0014]

[0015]

[0016] Where Vout represents the real-time output voltage, x1(Vin, Tin) represents the first fitting slope, and x2(Vin, Tin) represents the second fitting slope.

[0017] In the LLC resonant converter derating control method described in this invention, the first output voltage derating point V1, the second output voltage derating point V2, the third output voltage derating point V3, and the fourth output voltage derating point V4 satisfy the following condition: V2>V3>V1>V4; the first input voltage derating point Vin1, the second input voltage derating point Vin2, and the maximum input voltage Vinmax satisfy the following condition: Vinmax>Vin2>Vin1.

[0018] The LLC resonant converter derating control method of the present invention further includes: determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point.

[0019] In the LLC resonant converter derating control method of the present invention, the step of determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point includes the following steps: Step S1, determining whether the real-time input voltage of the LLC resonant converter is less than the first input voltage derating point; if yes, proceed to step S2; otherwise, determine that the derating condition is not met; Step S2, determining whether the real-time output voltage of the LLC resonant converter is less than the first output voltage derating point; if yes, determine that the derating condition is met; otherwise, determine that the derating condition is not met.

[0020] In the LLC resonant converter derating control method of the present invention, the step of determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point further includes: when the real-time input voltage is less than the third input voltage derating point, it is determined that the LLC resonant converter does not meet the derating condition; the third input voltage derating point = the first input voltage derating point - the set exit voltage.

[0021] In the LLC resonant converter derating control method of the present invention, the step of controlling the actual output power of the LLC resonant converter to track the target output power to achieve the derating control of the LLC resonant converter includes: generating a PWM control signal for controlling the LLC resonant converter by using the target output power as a given value for the closed-loop control of the LLC resonant converter; and controlling the switching transistors of the LLC resonant converter to be turned on or off based on the PWM control signal so that the actual output power of the LLC resonant converter tracks the target output power.

[0022] The LLC resonant converter derating control method of the present invention selects the real-time output current corresponding to the real-time output voltage on the real-time output voltage-real-time output current curve based on the real-time output voltage, calculates the target output power based on the real-time output current and the rated output voltage, and controls the actual output power of the LLC resonant converter to track the target output power to achieve derating control of the LLC resonant converter. The real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters and output current parameters of the LLC resonant converter. Therefore, it can accurately and linearly reflect the complex coupling relationship of the influence of input voltage and temperature on the power devices of the LLC resonant converter, thus achieving smooth and optimal power control derating control. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the drawings: Figure 1 is a flowchart of a preferred embodiment of the LLC resonant converter derating control method of the present invention; Figure 2 is a flowchart of another preferred embodiment of the LLC resonant converter derating control method of the present invention; Figure 3 is a fitting curve obtained using the LLC resonant converter derating control method of the present invention; Figure 4 is a comparative schematic diagram of derating curves obtained using the LLC resonant converter derating control method of the present invention and a derating method considering only the input voltage; Figure 5 is a comparative schematic diagram of derating curves obtained using the LLC resonant converter derating control method of the present invention and a derating method considering only the sampling temperature; Figure 6 is a schematic diagram of various derating curves obtained using the LLC resonant converter derating control method of the present invention at different input voltages and temperatures; Figures 7A-7C show some derating verification data obtained using the LLC resonant converter derating control method of the present invention; Figure 8 is a principle block diagram of a preferred embodiment of the LLC resonant converter derating control method of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Figure 1 is a flowchart of a preferred embodiment of the LLC resonant converter derating control method of the present invention. As shown in Figure 1, in step S1, when the LLC resonant converter meets the derating condition, the real-time output current corresponding to the real-time output voltage is selected on the real-time output voltage-real-time output current curve based on the real-time output voltage.

[0026] In a preferred embodiment of the present invention, the LLC resonant converter is determined to meet the derating condition based on the real-time input voltage, real-time output voltage, first input voltage derating point, and first output voltage derating point. In a further preferred embodiment of the present invention, determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, real-time output voltage, first input voltage derating point, and first output voltage derating point specifically includes step S11: determining whether the real-time input voltage of the LLC resonant converter is less than the first input voltage derating point; if yes, proceed to step S12; otherwise, determine that the derating condition is not met. Step S12: determining whether the real-time output voltage of the LLC resonant converter is less than the first output voltage derating point; if yes, determine that the derating condition is met; otherwise, determine that the derating condition is not met.

[0027] In a preferred embodiment of the present invention, the step of determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point further includes: when the real-time input voltage is less than the third input voltage derating point, determining that the LLC resonant converter does not meet the derating condition; the third input voltage derating point = the first input voltage derating point - the set exit voltage.

[0028] In a preferred embodiment of the present invention, the real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter. In another preferred embodiment, the input voltage parameters include a real-time input voltage, a first input voltage derating point, a second input voltage derating point, and a maximum input voltage; the temperature parameters include a real-time sampling temperature and a temperature derating point; the output voltage parameters include a real-time output voltage, a first output voltage derating point, a second output voltage derating point, a third output voltage derating point, and a fourth output voltage derating point; the output current parameters include a first output current, a second output current, a third output current, and a fourth output current; the first output current is the output current where the real-time output voltage is at the first output voltage derating point, the second output current is the output current where the real-time output voltage is at the second output voltage derating point, the third output current is the output current where the real-time output voltage is at the third output voltage derating point, and the fourth output current is the output current where the real-time output voltage is at the fourth output voltage derating point.

[0029] In a preferred embodiment of the present invention, the real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter, including: calculating the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point; and calculating the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, and the third output voltage derating point based on the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, and the third output voltage derating point. The system obtains a first boundary point, a second boundary point, a third boundary point, and a fourth boundary point by using the first boundary point and the fourth output voltage derating point; and fits the real-time output voltage-real-time output current curve based on the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; wherein the ordinate of the first boundary point is the first output current, and the abscissa is the first output voltage derating point; the ordinate of the second boundary point is the second output current, and the abscissa is the second output voltage derating point; the ordinate of the third boundary point is the third output current, and the abscissa is the third output voltage derating point; and the ordinate of the fourth boundary point is the fourth output current, and the abscissa is the fourth output voltage derating point.

[0030] In a preferred embodiment of the present invention, calculating the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point includes: calculating the first output current, the second output current, the third output current, and the fourth output current based on the following formula:

[0031]

[0032]

[0033]

[0034] Wherein, I1max represents the first output current, Vin represents the real-time input voltage, Vin1 represents the first input voltage derating point, Vin2 represents the second input voltage derating point, Vinmax represents the maximum input voltage; Tin represents the real-time sampling temperature, Tde represents the temperature derating point; I2(Vin, Tin) represents the second output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I3(Vin, Tin) represents the third output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I4(Vin, Tin) represents the fourth output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; Poutmax represents the maximum output power; V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; k1, k2, k3, k4, k5, and k6 represent the fitting coefficients.

[0035] The real-time output voltage-real-time output current curve satisfies the following formula:

[0036]

[0037]

[0038] Where Vout represents the real-time output voltage, x1(Vin, Tin) represents the first fitting slope, and x2(Vin, Tin) represents the second fitting slope.

[0039] The first output voltage derating point V1, the second output voltage derating point V2, the third output voltage derating point V3, and the fourth output voltage derating point V4 satisfy the following condition: V2>V3>V1>V4; the first input voltage derating point Vin1, the second input voltage derating point Vin2, and the maximum input voltage Vinmax satisfy the following condition: Vinmax>Vin2>Vin1.

[0040] In step S2, the target output power is calculated based on the real-time output current and the rated output voltage. In a preferred embodiment of the present invention, the rated output voltage is the output voltage Vout of the LLC resonant converter under rated conditions (rated minimum input voltage, rated maximum operating temperature), and the target output power P_out_target = I*Vout, where I is the real-time output current obtained in step S1. In this case, the target output power P_out_target is the maximum safe output power allowed to protect the power devices under the current conditions (i.e., real-time input voltage Vin and real-time sampling temperature).

[0041] In step S3, the actual output power of the LLC resonant converter is controlled to track the target output power in order to achieve derating control of the LLC resonant converter.

[0042] In a preferred embodiment of the present invention, controlling the actual output power of the LLC resonant converter to track the target output power to achieve derating control of the LLC resonant converter includes: generating a PWM control signal for controlling the LLC resonant converter using the target output power as a setpoint for the closed-loop control of the LLC resonant converter; and controlling the switching transistors of the LLC resonant converter to be turned on or off based on the PWM control signal so that the actual output power of the LLC resonant converter tracks the target output power.

[0043] The LLC resonant converter derating control method of the present invention selects the real-time output current corresponding to the real-time output voltage on the real-time output voltage-real-time output current curve based on the real-time output voltage, calculates the target output power based on the real-time output current and the rated output voltage, and controls the actual output power of the LLC resonant converter to track the target output power to achieve derating control of the LLC resonant converter. The real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter. Therefore, it can accurately and linearly reflect the complex coupling relationship of the influence of input voltage and temperature on the power devices of the LLC resonant converter, thus achieving smooth and optimal power control derating control.

[0044] Figure 2 is a flowchart of another preferred embodiment of the LLC resonant converter derating control method of the present invention. As shown in Figure 2, the real-time input voltage Vin and real-time output voltage Vout of the LLC resonant converter are first continuously sampled. It is determined whether the real-time input voltage of the LLC resonant converter is less than the first input voltage derating point Vin1. If so, the next step is executed: it is determined whether the real-time output voltage Vout is less than the first output voltage derating point V1; otherwise, it is determined that the derating condition is not met, and no derating control is performed. If the real-time output voltage Vout is less than the first output voltage derating point V1, it is determined that the derating condition is met, and derating control is entered. In this preferred embodiment, the real-time input voltage Vin and real-time output voltage Vout are continuously monitored. Only when both conditions Vin>Vin1 and Vout1 ≤ Vout are simultaneously met is it determined that an advanced derating protection condition needs to be activated. If either condition is not met, the system remains in a non-derating state to maximize performance.

[0045] At this point, a real-time output voltage-real-time output current curve needs to be fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter. Therefore, the real-time sampling temperature Tin is sampled. In a preferred embodiment of the present invention, the real-time sampling temperature Tin can be any temperature signal characterizing the circuit operating temperature T, for example, it can come from the junction temperature or case temperature sensor of the key power device (such as the main switching MOSFET) of the LLC resonant converter, the temperature of the resonant inductor, or the internal ambient temperature of the LLC resonant converter.

[0046] Based on the real-time input voltage Vin and the real-time sampling temperature Tin, the boundary points of the real-time output voltage-real-time output current curve are calculated. The specific calculation process is as follows.

[0047] Based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point, the first output current, the second output current, the third output current, and the fourth output current are calculated using the following formulas:

[0048]

[0049]

[0050]

[0051] Wherein, I1max represents the first output current, Vin represents the real-time input voltage, Vin1 represents the first input voltage derating point, Vin2 represents the second input voltage derating point, Vinmax represents the maximum input voltage; Tin represents the real-time sampling temperature, Tde represents the temperature derating point; I2(Vin, Tin) represents the second output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I3(Vin, Tin) represents the third output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I4(Vin, Tin) represents the fourth output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; Poutmax represents the maximum output power; V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; k1, k2, k3, k4, k5, and k6 represent the fitting coefficients.

[0052] Here, Vin represents the real-time input voltage, Tin represents the real-time sampled temperature (a real-time detected value), Vin1 represents the first input voltage derating point, Vinmax represents the maximum input voltage, Tde represents the temperature derating point, V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; all are preset values. The first input voltage derating point Vin is the derating start point of the input voltage, typically corresponding to the critical value at which the voltage stress of the power device begins to increase significantly. The maximum input voltage Vinmax is the maximum input voltage of the LLC resonant converter, which can be selected by those skilled in the art based on the actual situation of the LLC resonant converter. The first input voltage derating point Vin1, the second input voltage derating point Vin2, and the maximum input voltage Vinmax satisfy: Vinmax > Vin2 > Vin1. The second output voltage derating point V2 and the first output voltage derating point V1 are typically the most common load operating voltage range of the product; fine protection within this range is most valuable, therefore, those skilled in the art can select them based on the actual situation of the LLC resonant converter. The third output voltage derating point V3 and the fourth output voltage derating point V4 can be selected based on the second output voltage derating point V2 and the first output voltage derating point V1. The first output voltage derating point V1, the second output voltage derating point V2, the third output voltage derating point V3, and the fourth output voltage derating point V4 satisfy the following order: V2>V3>V1>V4. The fitting coefficients k1, k2, k3, k4, k5, and k6 can be obtained by linear fitting using actual test data. As those skilled in the art know, all measured data can be fitted into a piecewise linear curve to obtain the aforementioned fitting coefficients.

[0053] A first boundary point, a second boundary point, a third boundary point, and a fourth boundary point are obtained based on the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, the third output voltage derating point, and the fourth output voltage derating point; and the real-time output voltage-real-time output current curve is fitted based on the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; wherein the ordinate of the first boundary point is the first output current, and the abscissa is the first output voltage derating point; the ordinate of the second boundary point is the second output current, and the abscissa is the second output voltage derating point; the ordinate of the third boundary point is the third output current, and the abscissa is the third output voltage derating point; and the ordinate of the fourth boundary point is the fourth output current, and the abscissa is the fourth output voltage derating point.

[0054] That is, in a preferred embodiment of the present invention, after obtaining the aforementioned four boundary points, the real-time output voltage-real-time output current curve I_max(Vout) function is obtained by connecting the boundary points (V1, I1), (V2, I2), (V3, I3), and (V4, I4) as endpoints. The real-time output voltage-real-time output current curve satisfies the following formula:

[0055]

[0056]

[0057] Where Vout represents the real-time output voltage, x1(Vin, Tin) represents the first fitting slope, and x2(Vin, Tin) represents the second fitting slope.

[0058] Figure 3 shows the fitting curves obtained using the LLC resonant converter derating control method of the present invention, illustrating four boundary points (V1, I1), (V2, I2), (V3, I3), and (V4, I4), as well as the real-time output voltage-real-time output current curve A of the present invention and the fitting curve B of the prior art. It can be seen that the real-time output voltage-real-time output current curve A of the present invention employs piecewise linear fitting, with continuous switching nodes. This makes the derating control response smooth, predictable, and easy to implement in a microcontroller. In a preferred real-time operation of the present invention, the maximum output current at the boundary points (V2, I2) and (V4, I4) is calculated using a pre-stored model (formula or two-dimensional lookup table). These two current values ​​are the "dynamic anchor points" of the entire derating curve. They decrease as the real-time input voltage Vin increases (voltage stress increases) and as the real-time sampling temperature Tin increases (thermal stress increases), thus reflecting the dual influence of input voltage and operating temperature on derating control.

[0059] After obtaining the real-time output voltage-real-time output current curve, the real-time output current corresponding to the real-time output voltage is selected on the curve based on the real-time output voltage. This real-time output current is the maximum allowable output current under the current real-time output voltage, i.e., the maximum limit current. Based on the real-time acquired output voltage Vout, it is substituted into the real-time output voltage-real-time output current curve I_max(Vout) to immediately obtain the real-time output current I, i.e., the current maximum allowable output current limit I_limit_now. For example, through closed-loop control (such as a current loop), the actual output current is forced not to exceed this limit, thereby achieving precise and dynamic limitation of the output power. Specifically, the target output power is calculated based on the real-time output current and the rated output voltage. The rated output voltage is the output voltage Vout of the LLC resonant converter under rated conditions (rated minimum input voltage, rated maximum operating temperature), and the target output power P_out_target = I * Vout, where I is the real-time output current obtained in step S1. At this point, the target output power P_out_target is the maximum safe output power allowed to protect the power device under the current conditions (i.e., real-time input voltage Vin and real-time sampling temperature). In this preferred embodiment, the linearized real-time output voltage-real-time output current curve achieves smoothness and predictability of the derating process. For any real-time output voltage Vout within the interval, its maximum allowable output current (i.e., real-time output current) can be directly obtained through this linear equation (linear interpolation), resulting in extremely high computational efficiency.

[0060] The actual output power of the LLC resonant converter is controlled to track the target output power to achieve derating control of the LLC resonant converter. Specifically, the target output power P_out_target is used as the setpoint for the closed-loop control of the LLC resonant converter to generate a PWM control signal for controlling the LLC resonant converter. Based on the PWM control signal, the switching transistors of the LLC resonant converter are controlled to turn on or off so that the actual output power (or output current) of the LLC resonant converter tracks the target output power P_out_target. When the real-time input voltage Vin increases or the real-time sampling temperature Tin increases, I (i.e., the real-time output current Iout1(Vout, Vin, Tin) in the aforementioned formula) decreases, and the target output power P_out_target decreases linearly accordingly. The control system automatically limits the output power to protect the device. When the real-time input voltage Vin or the real-time sampling temperature Tin drops back, the target output power P_out_target recovers linearly, and the available power is automatically increased.

[0061] After entering derating control, the real-time input voltage and the real-time output voltage are continuously monitored. If it is found that Vout1 ≤ Vout is not satisfied, the derating mode is exited. In a further preferred embodiment of the invention, when the real-time input voltage Vin is less than the third input voltage derating point Vin3, it is determined that the LLC resonant converter does not meet the derating condition and exits the derating mode: wherein the third input voltage derating point Vin3 = the first input voltage derating point Vin1 - the set exit voltage (e.g., 10V). In this preferred embodiment, during the derating process, the real-time input voltage Vin is continuously monitored. Only when the real-time input voltage Vin drops and falls below (Vin1 - 10V) is it determined that the high-voltage stress has been sufficiently relieved and the derating mode is exited. Here, 10V (or a set value) is "hysteresis". Hysteresis is introduced to prevent frequent entry and exit of the derating mode when the real-time input voltage Vin fluctuates slightly near the first input voltage derating point Vin1, thereby causing output power oscillation and system instability. This is a classic engineering robustness design. In other preferred embodiments of the invention, any suitable set-out voltage can be set to match different LLC resonant converters.

[0062] Figure 4 is a comparative schematic diagram of the derating curves obtained by using the LLC resonant converter derating control method of the present invention and the derating method considering only the input voltage; Figure 5 is a comparative schematic diagram of the derating curves obtained by using the LLC resonant converter derating control method of the present invention and the derating method considering only the sampling temperature. As shown in Figure 4, the horizontal axis represents the real-time input voltage Vin; the vertical axis represents the real-time output current I when the real-time input voltage is Vin and the sampling temperature is different (selecting a specific sampling temperature of 30, 50 or 45 degrees Celsius). In Figure 4, the solid line represents the derating output power obtained by using the LLC resonant converter derating control method of the present invention, and the dashed line represents the derating output power obtained by using the derating method considering only the input voltage. That is, the dashed line in Figure 4 represents the derating output power when using the derating method considering only the input voltage, and the solid line represents the derating output power when using the LLC resonant converter derating control method of the present invention. It can be seen that the LLC resonant converter derating control method of the present invention can ensure that the circuit outputs as much power as possible.

[0063] As shown in Figure 5, the horizontal axis represents the real-time sampling temperature Tin; the vertical axis represents the real-time output current I when the real-time sampling temperature is Tin and the input voltage Vin is fixed at 750V. In Figure 5, the solid line represents the output current obtained when using the LLC resonant converter derating control method of the present invention, and the dashed line represents the output current obtained when using the derating method that only considers the sampling temperature. That is, the dashed line in Figure 5 represents the drated output power when using the derating method that only considers the sampling temperature, and the solid line represents the drated output power when using the LLC resonant converter derating control method of the present invention. It can be seen that the LLC resonant converter derating control method of the present invention can ensure that the circuit outputs as much power as possible.

[0064] The LLC resonant converter derating control method of this invention provides precise protection with dual factors. By simultaneously considering two core stress factors—real-time input voltage (affecting voltage stress) and real-time sampling temperature (affecting current carrying capacity and lifespan)—the derating model (i.e., the real-time output voltage-real-time output current curve) more closely reflects physical reality, resulting in more precise and comprehensive protection for power devices. This LLC resonant converter derating control method maximizes power output. Through a linearized derating model, it abandons the one-size-fits-all approach of traditional single or conservative derating strategies. Under non-extreme operating conditions, it safely allows the circuit to output higher power, fully exploiting hardware potential and enhancing the overall performance competitiveness of power supply products. This LLC resonant converter derating control method achieves smooth dynamic response. The linearized derating relationship ensures a smooth and continuous power adjustment process, avoiding output disturbances or system instability problems that may arise from step derating, thus improving user experience and load adaptability. This LLC resonant converter derating control method is simple to implement and highly versatile. The core algorithm can be implemented in existing controllers using simple lookup tables or linear formulas without adding complex hardware. This method can be widely applied to various power supply products using LLC topology. The LLC resonant converter derating control method of this invention also provides hysteresis exit, ensuring stability and reliability. Through the hysteresis design in the exit mechanism, the stability of operating state switching is ensured, avoiding critical point jitter and improving reliability.

[0065] In a preferred embodiment of the present invention, a specific LLC resonant converter is selected. This LLC resonant converter uses a full-bridge LLC circuit structure, employs a temperature sampler with a low time constant and high withstand voltage to directly acquire the temperature Tin of the core power device MOS, and uses voltage divider resistors to sample the input voltage Vin. The LLC resonant converter includes switching transistors Q1~Q4, a resonant network (inductor and capacitor), a transformer, a rectifier and filter circuit, and a heat sink.

[0066] As mentioned earlier, the real-time output voltage-real-time output current curve is obtained based on the following formula:

[0067]

[0068]

[0069] ;

[0070]

[0071]

[0072] Wherein, I1max represents the first output current, Vin represents the real-time input voltage, Vin1 represents the first input voltage derating point, Vin2 represents the second input voltage derating point, Vinmax represents the maximum input voltage; Tin represents the real-time sampling temperature, Tde represents the temperature derating point; I2(Vin, Tin) represents the second output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I3(Vin, Tin) represents the third output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I4(Vin, Tin) represents the fourth output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; Poutmax represents the maximum output power; V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; k1, k2, k3, k4, k5, and k6 represent the fitting coefficients; Vout represents the real-time output voltage, x1(Vin, Tin) represents the first fitting slope, x2(Vin, Tin) represents the second output voltage derating point, and x3(Vin, Tin) represents the third output voltage derating point. Tin) represents the second fitted slope.

[0073] Subsequently, based on the real-time output voltage, the corresponding real-time output current is selected on the real-time output voltage-real-time output current curve. Finally, the target output power is calculated based on the real-time output current and the rated output voltage. The actual output power of the LLC resonant converter is controlled to track the target output power to achieve derating control of the LLC resonant converter.

[0074] Figure 6 is a schematic diagram of various derating curves obtained using the LLC resonant converter derating control method of the present invention under different input voltages and temperatures. As shown in Figure 6, the horizontal axis represents the output voltage Vout, which ranges from Vout-V1 = 200 to 1000V, and the vertical axis represents the drated output power. Each curve corresponds to a different output current I(Vout, Vin, Tin). As shown in Figure 6, Vin takes values ​​of 700, 750, 800, 850, and 600 ohms, and Tin takes values ​​of 40, 45, 60, and 25 degrees Celsius. Different I(Vout, Vin, Tin) correspond to different derating conditions, and these derating conditions can be switched linearly under different input voltages and temperatures, ensuring the maximum output capacity under each condition. Figures 7A-7C show some derating verification data obtained using the LLC resonant converter derating control method of the present invention.

[0075] The LLC resonant converter derating control method of this invention provides precise protection with dual factors. By simultaneously considering two core stress factors—real-time input voltage (affecting voltage stress) and real-time sampling temperature (affecting current carrying capacity and lifespan)—the derating model (i.e., the real-time output voltage-real-time output current curve) more closely reflects physical reality, resulting in more precise and comprehensive protection for power devices. This LLC resonant converter derating control method maximizes power output. Through a linearized derating model, it abandons the one-size-fits-all approach of traditional single or conservative derating strategies. Under non-extreme operating conditions, it safely allows the circuit to output higher power, fully exploring the hardware potential and enhancing the overall performance competitiveness of the power supply product. This LLC resonant converter derating control method achieves smooth dynamic response. The linearized derating relationship ensures a smooth and continuous power adjustment process, avoiding output disturbances or system instability problems that may arise from step derating, thus improving user experience and load adaptability.

[0076] Figure 8 is a schematic block diagram of a preferred embodiment of the LLC resonant converter derating control system of the present invention. As shown in Figure 8, the LLC resonant converter derating control system of the present invention includes: an LLC resonant converter 100, a sampling module 200, a control module 300, and a drive module 400. Here, the LLC resonant converter 100 can be any known LLC resonant converter in the art, and may include, for example, switching transistors Q1~Q4, a resonant network (inductor, capacitor), a transformer, a rectifier filter circuit, and a heat sink.

[0077] The sampling module 200 is used to sample the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter. For example, a temperature sampler with a low time constant and high withstand voltage is used to directly acquire the core power device MOS temperature Tin, and voltage divider resistors are used to sample the input voltage Vin and output voltage Vout.

[0078] The control module 300 is used to select the real-time output current corresponding to the real-time output voltage on the real-time output voltage-real-time output current curve based on the real-time output voltage; and to calculate the target output power based on the real-time output current and the rated output voltage; the real-time output voltage-real-time output current curve is fitted based on the input voltage parameter, the temperature parameter, the output voltage parameter and the output current parameter.

[0079] The control module 300 may be, for example, a microprocessor (MCU) or a digital signal processor (DSP), which internally stores or runs programs to execute corresponding steps of the aforementioned LLC resonant converter derating control method. For example, it may fit the real-time output voltage-real-time output current curve based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter; select the real-time output current corresponding to the real-time output voltage on the real-time output voltage-real-time output current curve based on the real-time output voltage; and calculate the target output power based on the real-time output current and the rated output voltage.

[0080] The control module 300 is further used to control the drive module 400 to drive the switching transistor of the LLC resonant converter to turn on or off, so that the actual output power of the LLC resonant converter tracks the target output power to achieve derating control of the LLC resonant converter.

[0081] For example, the control module 300 is used to generate a PWM control signal for controlling the LLC resonant converter, using the target output power as a given value for the closed-loop control of the LLC resonant converter. The drive module 400 controls the switching transistors of the LLC resonant converter to turn on or off based on the PWM control signal, so that the actual output power of the LLC resonant converter tracks the target output power.

[0082] In a preferred embodiment of the present invention, the control module 300 can be further configured to calculate the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point; and to obtain the first boundary point and the second boundary point based on the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, the third output voltage derating point, and the fourth output voltage derating point. The first boundary point, the second boundary point, and the third boundary point; and the fitting of the real-time output voltage-real-time output current curve based on the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; wherein the ordinate of the first boundary point is the first output current, and the abscissa is the first output voltage derating point; the ordinate of the second boundary point is the second output current, and the abscissa is the second output voltage derating point; the ordinate of the third boundary point is the third output current, and the abscissa is the third output voltage derating point; and the ordinate of the fourth boundary point is the fourth output current, and the abscissa is the fourth output voltage derating point.

[0083] In a preferred embodiment of the present invention, the control module 300 can be further used to determine whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point.

[0084] In a preferred embodiment of the present invention, the control module 300 may further be used to perform the following steps: Step S1, determine whether the real-time input voltage of the LLC resonant converter is less than the first input voltage derating point; if yes, proceed to step S2; otherwise, determine that the derating condition is not met; Step S2, determine whether the real-time output voltage of the LLC resonant converter is less than the first output voltage derating point; if yes, determine that the derating condition is met; otherwise, determine that the derating condition is not met.

[0085] In a preferred embodiment of the present invention, the control module 300 can be further configured to determine that the LLC resonant converter does not meet the derating condition when the real-time input voltage is less than the third input voltage derating point; the third input voltage derating point = the first input voltage derating point - the set exit voltage.

[0086] Here, the LLC resonant converter derating control system of the present invention can be constructed with reference to the LLC resonant converter derating control method described in Figures 1 to 7. Those skilled in the art can construct the LLC resonant converter derating control system of the present invention based on the foregoing description of the method and obtain similar beneficial effects, which will not be repeated here.

[0087] Although the present invention has been described through specific embodiments, those skilled in the art will understand that various modifications and equivalent substitutions can be made to the invention without departing from its scope. Furthermore, various modifications can be made to the invention for specific situations or materials without departing from its scope. Therefore, the present invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A derating control method for an LLC resonant converter, characterized in that, include: When the LLC resonant converter meets the derating condition, the real-time output current corresponding to the real-time output voltage is selected on the real-time output voltage-real-time output current curve based on the real-time output voltage. The target output power is calculated based on the real-time output current and the rated output voltage; and the actual output power of the LLC resonant converter is controlled to track the target output power to achieve derating control of the LLC resonant converter; wherein the real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters and output current parameters of the LLC resonant converter.

2. The LLC resonant converter derating control method according to claim 1, characterized in that, The input voltage parameters include real-time input voltage, a first input voltage derating point, a second input voltage derating point, and a maximum input voltage; the temperature parameters include real-time sampling temperature and a temperature derating point; the output voltage parameters include real-time output voltage, a first output voltage derating point, a second output voltage derating point, a third output voltage derating point, and a fourth output voltage derating point; the output current parameters include a first output current, a second output current, a third output current, and a fourth output current; the first output current is the output current where the real-time output voltage is at the first output voltage derating point, the second output current is the output current where the real-time output voltage is at the second output voltage derating point, the third output current is the output current where the real-time output voltage is at the third output voltage derating point, and the fourth output current is the output current where the real-time output voltage is at the fourth output voltage derating point.

3. The LLC resonant converter derating control method according to claim 2, characterized in that, The real-time output voltage-real-time output current curve is fitted based on the input voltage parameters, temperature parameters, output voltage parameters, and output current parameters of the LLC resonant converter, including: calculating the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point; and calculating the first output current, the second output current, the third output current, the fourth output current, the first output voltage derating point, the second output voltage derating point, the third output voltage derating point, and the fourth output current. The output voltage derating point is used to obtain a first boundary point, a second boundary point, a third boundary point, and a fourth boundary point; and the real-time output voltage-real-time output current curve is fitted based on the first boundary point, the second boundary point, the third boundary point, and the fourth boundary point; wherein the ordinate of the first boundary point is the first output current, and the abscissa is the first output voltage derating point; the ordinate of the second boundary point is the second output current, and the abscissa is the second output voltage derating point; the ordinate of the third boundary point is the third output current, and the abscissa is the third output voltage derating point; and the ordinate of the fourth boundary point is the fourth output current, and the abscissa is the fourth output voltage derating point.

4. The LLC resonant converter derating control method according to claim 3, characterized in that, The calculation of the first output current, the second output current, the third output current, and the fourth output current based on the real-time input voltage, the first input voltage derating point, the second input voltage derating point, the maximum input voltage, the real-time sampling temperature, and the temperature derating point includes: calculating the first output current, the second output current, the third output current, and the fourth output current based on the following formula: Wherein, I1max represents the first output current, Vin represents the real-time input voltage, Vin1 represents the first input voltage derating point, Vin2 represents the second input voltage derating point, Vinmax represents the maximum input voltage; Tin represents the real-time sampling temperature, Tde represents the temperature derating point; I2(Vin, Tin) represents the second output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I3(Vin, Tin) represents the third output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; I4(Vin, Tin) represents the fourth output current when the real-time input voltage is Vin and the real-time sampling temperature is Tin; Poutmax represents the maximum output power; V1 represents the first output voltage derating point, V2 represents the second output voltage derating point, V3 represents the third output voltage derating point, and V4 represents the fourth output voltage derating point; k1, k2, k3, k4, k5, and k6 represent the fitting coefficients.

5. The LLC resonant converter derating control method according to claim 4, characterized in that, The real-time output voltage-real-time output current curve satisfies the following formula: Where Vout represents the real-time output voltage, x1(Vin, Tin) represents the first fitting slope, and x2(Vin, Tin) represents the second fitting slope.

6. The LLC resonant converter derating control method according to claim 5, characterized in that, The first output voltage derating point V1, the second output voltage derating point V2, the third output voltage derating point V3, and the fourth output voltage derating point V4 satisfy the following condition: V2>V3>V1>V4; the first input voltage derating point Vin1, the second input voltage derating point Vin2, and the maximum input voltage Vinmax satisfy the following condition: Vinmax>Vin2>Vin1.

7. The LLC resonant converter derating control method according to any one of claims 1 to 6, characterized in that, Further includes: Based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point, it is determined whether the LLC resonant converter meets the derating condition.

8. The LLC resonant converter derating control method according to claim 7, characterized in that, The method for determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point includes the following steps: Step S1, determining whether the real-time input voltage of the LLC resonant converter is less than the first input voltage derating point; if yes, proceed to step S2; otherwise, determine that the derating condition is not met; Step S2, determining whether the real-time output voltage of the LLC resonant converter is less than the first output voltage derating point; if yes, determine that the derating condition is met; otherwise, determine that the derating condition is not met.

9. The LLC resonant converter derating control method according to claim 7, characterized in that, The step of determining whether the LLC resonant converter meets the derating condition based on the real-time input voltage, the real-time output voltage, the first input voltage derating point, and the first output voltage derating point further includes: when the real-time input voltage is less than the third input voltage derating point, it is determined that the LLC resonant converter does not meet the derating condition; the third input voltage derating point = the first input voltage derating point - the set exit voltage.

10. The LLC resonant converter derating control method according to claim 7, characterized in that, The method of controlling the actual output power of the LLC resonant converter to track the target output power to achieve derating control of the LLC resonant converter includes: generating a PWM control signal for controlling the LLC resonant converter by using the target output power as a setpoint for the closed-loop control of the LLC resonant converter; and controlling the switching transistors of the LLC resonant converter to be turned on or off based on the PWM control signal so that the actual output power of the LLC resonant converter tracks the target output power.

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