A low-noise heat dissipation system of a high-power charging pile power module

Abstract

The application relates to a low-noise heat dissipation system of a high-power charging pile power module, which comprises an air-cooled large fan controlled by a charging pile main control board CCU, and further comprises a TEC auxiliary heat dissipation unit, an auxiliary heat dissipation control module and an auxiliary heat dissipation working power supply; the TEC auxiliary heat dissipation unit is arranged on each key heat generating power device of a charging power supply module; the TEC auxiliary heat dissipation unit comprises a semiconductor refrigeration sheet TEC, heat dissipation fins, a small fan and temperature sensors for monitoring the cold face and the hot face temperature of the TEC respectively; and the heat dissipation fins are attached to the hot face of the TEC. During charging, the large fan of the air-cooled system is used for heat dissipation in addition to the small fan and the TEC transient heat dissipation driven by an independent MCU, so that the total power of the large fan of the air-cooled system is reduced and noise is reduced.

Description

Technical Field

[0001] This invention relates to power module thermal management of high-power DC charging piles, and is particularly suitable for the silent operation of 160 kW and above supercharging terminals in noise-sensitive scenarios such as residential areas and nighttime. Background Technology

[0002] Existing air-cooled charging piles use a single high-power fan, with its speed uniformly controlled by the main control unit (CCU). Under full load, the fan speed can reach 6000 rpm or even higher, with noise levels of 65–68 dB(A). Reducing the fan speed can reduce noise, but this causes the chip temperature to rise rapidly beyond the limit, creating a dilemma between noise reduction and heat dissipation. Summary of the Invention

[0003] This invention addresses the dilemma of "noise reduction and heat dissipation" in high-power DC charging piles by proposing a low-noise heat dissipation system for high-power charging pile power modules, which uses a decoupled heat dissipation approach of "power reduction of the original large fan and independent compensation of the small fan + TEC".

[0004] This invention is achieved through the following technical solution: A low-noise heat dissipation system for a high-power charging pile power module includes a large air-cooled fan controlled by the charging pile main control board (CCU), and also includes... The TEC auxiliary heat dissipation unit is respectively installed on each key heat-generating power device of the charging power module. The TEC auxiliary heat dissipation unit includes a semiconductor cooling chip TEC, heat dissipation fins, a small fan, and temperature sensors that monitor the cold and hot surfaces of the TEC respectively. The heat dissipation fins are attached to the hot surface of the TEC. The auxiliary heat dissipation control module includes an MCU, a temperature detection circuit that receives and processes temperature sensor signals, and a drive control circuit. The MCU monitors the temperature of the TEC auxiliary heat dissipation unit and controls the TEC and the small fan. The auxiliary heat dissipation power supply provides operating power for the TEC auxiliary heat dissipation unit and the auxiliary heat dissipation control module.

[0005] Preferably, the MCU of the auxiliary heat dissipation control module listens for the "charging activation" status through a digital bus or level signal. When the charging power module is activated, the MCU starts the TEC auxiliary heat dissipation unit to work. The TEC cooling capacity and the speed of the small fan are dynamically adjusted by the temperature monitored by the MCU, so as to achieve decoupling and parallel operation with the air-cooled large fan.

[0006] Preferably, when the charging power module stops working, the MCU of the auxiliary heat dissipation control module turns off the TEC cooling and keeps the small fan running until the temperature of the heat sink fins returns to normal, i.e., less than the ambient temperature +5℃.

[0007] The beneficial effects of this invention are as follows: During charging, in addition to the large air-cooled fan for heat dissipation, a small fan driven by an independent MCU and transient heat dissipation by the TEC are also used, reducing the total power of the large fan in the air-cooling system and reducing noise. The original air-cooling system of this invention does not require rewiring or recertification, resulting in a short upgrade cycle; the power consumption of the large fan is significantly reduced, thereby significantly reducing the overall noise; the peak junction temperature of power devices can be reduced, improving device lifespan; the TEC auxiliary heat dissipation is controlled by an independent MCU, which can run in parallel with the CCU thermal strategy, and the failures of each other do not affect each other. Detailed Implementation

[0008] The present invention will be further described in detail below through specific embodiments.

[0009] A low-noise heat dissipation system for a high-power charging pile power module includes a large air-cooled fan controlled by the charging pile's main control board (CCU), which is the existing heat dissipation system. An additional TEC + small fan heat dissipation system is added, including a TEC auxiliary heat dissipation unit, an auxiliary heat dissipation control module, and an auxiliary heat dissipation power supply. The TEC auxiliary heat dissipation unit is located on each critical heat-generating power device (IGBT or SiC) of the charging power module. The TEC auxiliary heat dissipation unit includes a thermoelectric cooler (TEC), heat sink fins, a small fan, and temperature sensors that monitor the cold and hot surfaces of the TEC. The heat sink fins are attached to the hot surface of the TEC, and the small fan dissipates heat from the heat sink fins. The auxiliary heat dissipation control module includes an MCU, a temperature detection circuit that receives and processes the temperature sensor signals, and a drive control circuit. The MCU monitors the temperature of the TEC auxiliary heat dissipation unit and controls the operation of the TEC and the small fan through the drive control circuit. The auxiliary heat dissipation power supply provides operating power to the TEC auxiliary heat dissipation unit and the auxiliary heat dissipation control module.

[0010] The MCU of the auxiliary heat dissipation control module monitors the "charging activation" status via a digital bus or level signal. When the charging power module is activated, the MCU starts the TEC auxiliary heat dissipation unit. The TEC cooling capacity and the speed of the small fan are dynamically adjusted by the temperature monitored by the MCU, achieving decoupling and parallel operation with the air-cooled main fan. When the charging power module stops working, the MCU of the auxiliary heat dissipation control module shuts down the TEC cooling, keeping the small fan running until the temperature of the heat sink fins returns to normal, i.e., less than the ambient temperature +5°C.

[0011] Taking the 40kW charging power module used in mainstream high-power charging piles as an example, multiple charging power modules can be regarded as being used as a single unit stacked together.

[0012] First, let's look at some of the heat dissipation-related indicators and requirements of the original air-cooling system: (1) The power device uses a TO-247 package, and its junction-to-case thermal resistance is: R jc = 0.30 K / W (datasheet value) (2) Heat sink, thermal resistance R sa =0.04 K / W, corresponding to the original air-cooled large fan rated at 65 CFM (Cubic Feet per Minute). The conversion efficiency of the 40kW module is 97%, and the loss is equivalent to 40kW × (1-97%) = 1200W. Under stable operating conditions, the temperature rise is 1200W × 0.04K / W = 48K, which is completely consistent with the industry-tested temperature of 70℃ ± 5℃ in a 25℃ environment.

[0013] (3) For power devices, at a test environment temperature of 25℃, the controller junction temperature T needs to be [missing information]. j ≤80℃, meaning the temperature rise should be controlled within 55℃.

[0014] (4) There are 9 key power devices inside the charging power module, with a total loss of 1200W and an average loss of 130W.

[0015] Based on the above data, the temperature rise ΔT of the large fan at full speed in the original design... j = 130W × (0.30K / W + 0.04K / W) = 44.2 K, margin 10.8 K.

[0016] The relationship between the sound power level LW of an axial fan and its rotational speed n can be described by an empirical exponential model: α≈4.5~5, and the following calculations will be performed with α=5.

[0017] With a noise reduction target of ≥6 dB, we calculated that the corresponding fan speed needs to be reduced by 24% based on 10×lg(1-0.24) = -6dB.

[0018] We know that airflow is directly proportional to rotational speed, and the relationship between radiator thermal resistance and airflow (empirical formula) is as follows:

[0019] When the fan speed decreases by 24%, the heatsink's thermal resistance rises to R. sa =0.04K / W×1 / (0.76 0.7 =0.0485 K / W; ΔT j = 130 W × (0.30K / W + 0.0485K / W) = 45.3K, the margin is reduced to 9.7K.

[0020] To achieve a 24% reduction in fan speed, we need to use other cooling methods to offset the heat dissipation from the normal speed versus the adjusted speed.

[0021] Considering the impact of transient peak values, model bias, and improved components, the target margin should be increased from the original 9.7K to over 13K, meaning that the newly added heat dissipation components need to achieve a temperature drop capability of 3.3K.

[0022] This invention adds nine 20W TECs (Digital Heat Dissipation Units). The cold side of the TEC is bonded to power devices, and the hot side is fitted with 40mm x 40mm aluminum heat sink fins. Nine small fans (each 0.8W, 3 CFM) are mounted on the heat sink fins. One NTC temperature sensor is installed on each of the cold and hot sides of the TEC. The entire unit also includes an auxiliary cooling control module and an auxiliary cooling power supply. The nine small fans provide a total of 7.2W, and the auxiliary cooling power supply only needs to be 12V / 1A.

[0023] The auxiliary heat dissipation control module contains an MCU, a temperature detection circuit, a TEC and a small fan drive control circuit. The temperature detection circuit acquires the temperature sensor signals of the cold and hot sides of each TEC, processes them and sends them to the MCU. The MCU listens for the "charging activation" signal of the CCU through a data bus (such as I²C).

[0024] When charging begins, the MCU listens for the "charging activated" signal and then activates the TEC cooling system and starts the small fan for heat dissipation. The situation at this time is as follows: (1) TEC cooling power Q c =20 W (2) The small fan is a 4010 specification fan. At 4500 rpm, the airflow is 1.5 CFM and the thermal resistance is R. f The typical value is 0.80 K / W, meaning that the small fan reduces the thermal resistance of the heatsink fins to 0.8 K / W.

[0025] (3) There are now two paths for heat dissipation of each power device.

[0026] Original path: 0.30K / W + 0.0485K / W = 0.3485 K / W TEC path: 0.30 K / W + 0.80 K / W = 1.10 K / W Parallel thermal resistance R p = (0.3485×1.10) / (0.3485+1.10) ≈ 0.265 K / W (4) TEC cold charge injection is 20 W per device, resulting in a negative temperature drop ΔT tec =–Q c ×R js =–20 W × 0.30 K / W =–6.0 K (5) Steady-state junction temperature change ΔT j= 130 W × 0.265 K / W – 6.0 K = 28.45 K, when the ambient temperature is 25℃, the junction temperature T j = 25℃ + 28.45K = 53.45℃, margin > 26 K, can withstand short-term overload or ambient temperature rise to achieve the purpose.

[0027] (6) The total weight of all heat sinks in the power module is approximately 1.2 kg. The specific heat at around 20℃ is approximately 900 J / (kg·K), the heat capacity of the heat sink is 1080 J / K, and the device-heat sink time constant τ = Cs × R sa = 1080J / K × 0.0485 = 52.4s, meaning the system reached steady state in less than 1 minute.

[0028] Because the CCU usually activates the "charging activation" signal as soon as it detects that the charging gun is plugged into the electric vehicle, and there are still some human-machine interaction operations before the actual charging begins. During this period, the TEC and small fan have already started to cool down. If the original state was the ambient temperature, and the TEC has a cooling effect, the power devices will cool down in advance, generally 5~6℃ lower than the ambient temperature.

[0029] Furthermore, when charging is complete, the MCU hears the charging completion command, then shuts off the cooling for the TEC, maintains the small fan to dissipate heat from the heat sink fins, and monitors the temperature of the TEC hot surface until it approaches the ambient temperature, then stops the small fan.

[0030] After shutdown, the TEC is turned off, the fan continues to run, and the system switches to single exponential cooling. Assuming the steady-state temperature difference ΔT1 relative to ambient temperature is 60K, and the target temperature is reduced to 5K above ambient temperature (ΔT2), and given the previously calculated device-heatsink time constant τ = 52.4S, the heat dissipation recovery time T... f =τ×ln(ΔT1 / ΔT2)=52.4S×ln(60K / 5K)=130.2S, meaning it can recover to normal status in less than 2.5 minutes, meeting the requirements for continuous operation.

[0031] The noise of the small fans was not considered in the previous calculations. There are 9 small fans. Based on the selected model, the sound power of a single fan is about 43 dB. The far-field superimposed sound power of the small fans is LW1 = 43 + 10 lg9 ≈ 52 dB.

[0032] The original large fan operates at 3000 RPM without speed reduction, with a sound power LW0 of 65 dB. With a 6 dB noise reduction target, the sound power drops to 59 dB after speed reduction. The combined energy of the small and large fans, LW2 = 10 lg(10^(5.9) + 10^(5.2)) ≈ 59.8 dB. Therefore, the overall target of 6 dB is not achieved, and the large fan speed needs to be further reduced. In the previous analysis, the core indicator of the solution, the junction temperature of the power devices, has a 26K margin. Therefore, the large fan speed can be further reduced, calculated to 60% of its original speed, i.e., 1800 RPM, which still meets the requirements. In practice, adjustments can be made based on safety margins and considerations for continuous operation.

[0033] Assuming the air-cooled large fan speed is reduced to 60% of its original speed, refer to the previous calculation method.

[0034] The thermal resistance of the heatsink rises to R sa =0.04K / W×1 / (0.6 0.7 =0.0572 K / W.

[0035] ΔT j = 130 W × (0.30 K / W + 0.0572 K / W) = 46.4 K, the margin is reduced to 8.6 K.

[0036] The target margin should be increased from the original 8.6K to over 13K, meaning that the new heat dissipation components need to achieve a temperature drop capability of 4.4K.

[0037] There are now two paths for heat dissipation for each power device.

[0038] Original path: 0.30K / W + 0.0572K / W = 0.3752K / W TEC path: 0.30 K / W + 0.80 K / W = 1.10 K / W Parallel thermal resistance R p = (0.3752×1.10) / (0.3752+1.10) ≈ 0.280 K / W TEC cold injection of 20 W per device, negative temperature drop ΔT tec =–Q c ×R js =–20 W × 0.30 K / W =–6.0 K Steady-state junction temperature change ΔT j = 130 W × 0.280 K / W – 6.0 K = 30.4 K, when the ambient temperature is 25℃, the junction temperature T j = 25℃ + 30.4K = 55.4℃, with a margin of 24.6K, which can withstand short-term overload or ambient temperature rise to achieve the purpose.

[0039] The noise of the small fans: There are 9 small fans. Depending on the selected model, the sound power of a single fan is about 43 dB. The far-field superimposed sound power of the small fans is LW1 = 43 + 10 lg9 ≈ 52 dB.

[0040] The original large fan was 3000 RPM without slowing down, and its sound power LW0 was 65dB. After slowing down, it was 39dB. The combined energy of the small fan and the large fan was LW2 = 10 lg(10^(3.9) + 10^(5.2)) ≈ 52.2 dB, which is a decrease of 12.8dB.

[0041] In practice, adjustments can be made based on safety margins and considerations for continuous operation. Using a combination of a large air-cooled fan and a TEC + small fan in parallel can reduce noise and improve heat dissipation.

[0042] During charging, in addition to the large air-cooled fan for heat dissipation, the invention also uses an independent MCU to drive a small fan and TEC for transient heat dissipation, which significantly reduces the overall noise. Furthermore, the TEC auxiliary heat dissipation is controlled by an independent MCU and can run in parallel with the CCU thermal strategy, so that faults do not affect each other.

Claims

1. A low-noise heat dissipation system for a high-power charging pile power module, comprising a large air-cooled fan controlled by the charging pile main control board (CCU), characterized in that: It also includes, The TEC auxiliary heat dissipation unit is respectively installed on each key heat-generating power device of the charging power module. The TEC auxiliary heat dissipation unit includes a semiconductor cooling chip TEC, heat dissipation fins, a small fan, and temperature sensors that monitor the cold and hot surfaces of the TEC respectively. The heat dissipation fins are attached to the hot surface of the TEC. The auxiliary heat dissipation control module includes an MCU, a temperature detection circuit that receives and processes temperature sensor signals, and a drive control circuit. The MCU monitors the temperature of the TEC auxiliary heat dissipation unit and controls the TEC and the small fan. The auxiliary heat dissipation power supply provides operating power for the TEC auxiliary heat dissipation unit and the auxiliary heat dissipation control module.

2. The low-noise heat dissipation system for a high-power charging pile power module according to claim 1, characterized in that: The MCU of the auxiliary heat dissipation control module listens for the "charging activation" status through a digital bus or level signal. When the charging power module is activated, the MCU starts the TEC auxiliary heat dissipation unit to work. The TEC cooling capacity and the speed of the small fan are dynamically adjusted by the temperature monitored by the MCU, so as to achieve decoupling and parallel operation with the air-cooled large fan.

3. The low-noise heat dissipation system for a high-power charging pile power module according to claim 1, characterized in that: When the charging power module stops working, the MCU of the auxiliary heat dissipation control module turns off the TEC cooling and keeps the small fan running until the temperature of the heat sink fins returns to normal, i.e., less than the ambient temperature +5℃.

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