Vehicle power supply unit

Abstract

To provide a vehicle power supply device which can strike a balance between an upper-side battery and a lower-side battery.SOLUTION: A vehicle power supply device comprises: an upper-side battery E1 of a high voltage side; a lower-side battery E2 connected to an earth side; a junction point CP of the upper side battery and the lower side battery; and FET 1 and FET 2 that supply electric power through a PID control 50 to the upper-side battery E1 and the lower-side battery E2. Further, the vehicle power supply device applies a feedback control 60 of a time longer than I (integral control) by the PID control 50.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle power supply device that supplies multiple voltages via a divided battery. [Background technology]

[0002] Patent Document 1 discloses a vehicle power supply device that performs power conversion by selectively connecting a storage battery from a high-voltage power supply formed by connecting storage batteries in series to a low-voltage power supply load.

[0003] FIG. 7 shows a prior art vehicle power supply system 310. The battery is divided into an upper battery E1 connected to the high voltage VB side and a lower battery E2 connected to the earth EA side. Current Iout is output from the connection point CP between the upper battery E1 and the lower battery E2. High voltage is supplied from the high voltage VB side. The upper battery E1 and the lower battery E2 are charged by a balancing circuit 240. The balancing circuit 240 is controlled by the control unit 230.

[0004] Figure 8(A) shows the equivalent circuit of the balancing circuit, upper battery E1, and lower battery E2 in Figure 7. A control signal with a duty of 50% is applied to FET1 and FET2, and FET1 charges the upper battery E1 via coil L, and FET2 charges the lower battery E2 via coil L.

[0005] The circuit configuration of Fig. 8(A) is equivalent to the configuration shown in Fig. 8(B), that is, it is equivalent to a configuration in which an ideal power supply of V / 2 and an output impedance R are combined.

[0006] The configuration in Figure 8(B) is equivalent to the configuration shown in Figure 8(C). When a load current I flows through the load, the upper battery E1 becomes [V / 2+IR] and the lower battery E2 becomes [V / 2-IR], resulting in an imbalance.

[0007] Figure 9 shows the configuration of a conventional DC-DC converter that applies P (proportional control), I (integral control), and D (differential control) control to FET1 and FET2. The 12V output voltage from the connection point CP of FET1 and FET2 is compared with a reference voltage of V / 2 by operational amplifier OPI, differentiated by differentiation circuit 136, and added to summing node AN. Similarly, the 12V output voltage is compared with a reference voltage of V / 2 by operational amplifier OPP, and added to summing node AN. The 12V output voltage is compared with a reference voltage of V / 2 by operational amplifier OPD, integrated by integration circuit 138, and added to summing node AN. The output from summing node AN is fed back to FET1 and FET2.

[0008] Figure 10 shows the input voltage (10(A)), output current (10(B)), and output voltage (Figure 10(C)) of the circuit shown in Figure 9. When an overcurrent occurs, that is, a current exceeding the current limit of the DC-DC converter, the output voltage drops.

[0009] FIG. 11(A) shows a configuration in which P (proportional control), I (integral control), and D (differential control) control shown in FIG. 9 are added to the circuit shown in FIG. 8(A). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-26973 Summary of the Invention [Problem to be solved by the invention]

[0011] In a vehicle power supply device, for example, when an electric power steering motor is rapidly rotated, an output exceeding the specified output current may occur. In such a case, as shown in FIG. 11(B), which shows the output current of the configuration in FIG. 11(A), the voltage of the lower battery E2, shown by the solid line, falls below the average voltage of the lower battery E2, shown by the dashed line. That is, in real-time proportional (P) integral (I) differential (D) control, the voltage of the lower battery E2 drops (lower than 2 / V by ΔV [IR in FIG. 8(C)]) due to the battery voltage application time and the chemical reaction delay time, and the voltage of the upper battery E1 rises (higher than 2 / V by ΔV), causing an imbalance between the upper and lower batteries, leading to battery wear and a shortened lifespan.

[0012] An object of the present invention is to provide a vehicle power supply device that can balance the upper and lower batteries. [Means for solving the problem]

[0013] The vehicle power supply device according to the present invention comprises a battery divided into an upper battery on the high voltage side and a lower battery on the low voltage side, a DC-DC converter that supplies power to the upper battery and the lower battery within a preset output limit, and further characterized by the addition of feedback control that feeds back the difference between the long-term average value of the output of the DC-DC converter and a target value. [Effects of the Invention]

[0014] The integral term of I (integral control) in the conventional proportional control, integral control, and differential control (P, I, D) control is set to maintain the current output voltage at the output command voltage. Therefore, if the time constant of the integral term of I (integral control) in the conventional proportional control, integral control, and differential control (D) control is increased, the response to the target command voltage will deteriorate, and a voltage different from the desired output voltage will be output.

[0015] The vehicle power supply device of claim 1 is provided with long-term feedback control, which allows control to maintain battery balance over a long period of time.

[0016] The vehicle power supply device of claim 2 adds feedback control with a longer time than the I (integral control) of PID control to the power supply circuit that supplies power using P (proportional control), I (integral control), and D (differential control) control. As a result, in the short term, it is possible to output a voltage that is approximately the same as the target output voltage, and in the long term, it is possible to perform control that balances the battery.

[0017] Furthermore, with only real-time P (proportional control), I (integral control), and D (differential control) control, the voltage of the lower battery drops due to the battery voltage application time and the delay time of the chemical reaction, resulting in a poor balance between the upper and lower batteries. However, by adding feedback control with a longer duration than the I (integral control) control of PID control, the battery voltage application time corresponds to the delay time of the chemical reaction, and the upper and lower batteries are balanced, thereby reducing battery consumption and extending battery life.

[0018] The vehicle power supply device of claim 3 uses feedback control to add the difference between the long-term average value of the DC-DC converter output and the target value to the input side of the DC-DC converter, which allows the output voltage to be approximately the same as the target output voltage in the short term, and allows control to be performed to balance the battery in the long term.

[0019] In the vehicle power supply device of claim 4, the voltages of the upper and lower batteries are approximately equal, so the power supply circuit can charge the upper and lower batteries with a simple 50-50 duty.

[0020] In the vehicle power supply device of claim 5, the voltage of the upper battery is higher than the voltage of the lower battery. The power supply circuit can charge the upper and lower batteries by adjusting the duty ratio according to the voltage.

[0021] In the vehicle power supply device of claim 6, the long-term average value is calculated by calculation processing, so that it is possible to accurately calculate the average over a long period of time, for example, about one hour, and by matching the battery voltage application time with the delay time of the chemical reaction and balancing the upper and lower batteries, it is possible to reduce battery consumption and extend battery life. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram showing equivalent circuits of a balancing circuit, an upper battery, and a lower battery of a vehicle power supply device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the contents of PID control of the vehicle power supply device according to the first embodiment. [Figure 3] FIG. 3(A) shows the output current of the vehicle power supply device of the first embodiment, FIG. 3(B) shows the output voltage when integral control with a long time constant is not added, and FIG. 3(C) shows the output voltage when integral control with a long time constant is added. [Figure 4] 10 is a flowchart showing processing in an integrating circuit. [Figure 5] FIG. 4 is a circuit diagram of a vehicle power supply device according to a modified example of the first embodiment of the present invention. [Figure 6] FIG. 6 is a circuit diagram of a vehicle power supply device according to a second embodiment. [Figure 7] 1 is a diagram showing the configuration of a vehicle power supply device according to a first embodiment and a conventional technology; [Figure 8] FIG. 1 is a diagram showing equivalent circuits of a balancing circuit, an upper battery, and a lower battery of a conventional vehicle power supply device. [Figure 9] FIG. 1 shows the configuration of a conventional DC-DC converter that applies PID control to an FET. [Figure 10] 10(A) shows the input voltage of the circuit shown in FIG. 9, FIG. 10(B) shows the output current, and FIG. 10(C) shows the output voltage. [Figure 11] FIG. 11(A) shows the configuration of a conventional DC-DC converter, and FIG. 11(B) shows the output voltage of the DC-DC converter of FIG. 11(A). DETAILED DESCRIPTION OF THE INVENTION

[0023] [First embodiment] FIG. 7 shows the configuration of a vehicle power supply device 10 according to the first embodiment. The battery is divided into an upper battery E1 connected to the 24V high voltage VB side, and a lower battery E2 connected to the earth EA side. The voltage of the upper battery E1 and the voltage of the lower battery E2 are both 12V. A current Iout of 12V is output from the connection point CP between the upper battery E1 and the lower battery E2. A high voltage of 24V is supplied from the high voltage VB side. The upper battery E1 and the lower battery E2 are charged by a balancing circuit 40. The balancing circuit 40 is controlled by the control unit 30. The control unit 30 and the balancing circuit 40 form a DC-DC converter.

[0024] The control unit 30 limits the output current Iout to prevent an output current exceeding a preset rated output capacity from flowing for a long period of time and to ensure safe operation in the event of an output abnormality. That is, when the control unit 30 monitors the output current (current Iout) and detects an abnormal current, it limits the current to prevent any further output current from flowing. Note that an output current exceeding the rated output capacity flows only for a very short period of time. For example, when the electric power steering is operated to a locked state, a large output current flows for a very short period of time (approximately 2 seconds). Note that the electric power steering lock state occurs very rarely, and is expected to occur at most once an hour.

[0025] Figure 1 shows the equivalent circuit of the balancing circuit, upper battery E1, and lower battery E2 in Figure 7. A control signal with a duty of 50% is applied to FET1 and FET2, and FET1 charges the upper battery E1 via coil L, and FET2 charges the lower battery E2 via coil L.

[0026] A PID control 50 that performs proportional (P), integral (I), and differential (D) control is provided on the input side of FET1 and FET2. The details of the PID control are shown in Figure 2. The 12V output voltage from the connection point CP of FET1 and FET2 is compared with a reference voltage of V / 2 by an operational amplifier OPI, differentiated by a differentiation circuit 36, and added to a first summing node AN1. Similarly, the 12V output voltage is compared with a reference voltage of V / 2 by an operational amplifier OPP, and added to a first summing node AN1. The 12V output voltage is compared with a reference voltage of V / 2 by a first operational amplifier OPD1, integrated by an integration circuit 38, and added to a first summing node AN1. The output from the first summing node AN1 is fed back to FET1 and FET2.

[0027] In the vehicle power supply device 10 of the first embodiment, in addition to the PID control 50, feedback control 60 using averaging means 68 that calculates an average value over a longer time period than the I control by the integrator circuit 38 of the PID control 50 is added. The averaging time of the averaging means 68 is preferably at least 10 times longer than the time constant of the integrator circuit 38, and more preferably 100 times longer. An average value over a longer period than the I control by the integrator circuit 38 of the PID control 50 is calculated by the averaging means 68, and the calculated average value is compared with a reference voltage (target value) of V / 2 by the second operational amplifier OPD2, and the difference is applied to the second summing node AN2. The output from the second summing node AN2 is applied to one input terminal of the PID control 50. The 12V output voltage is applied to the other input terminal of the PID control 50.

[0028] FIG. 3(A) shows the output current of the first embodiment, FIG. 3(B) shows the output voltage when feedback control is not added, and FIG. 3(C) shows the output voltage when feedback control is added.

[0029] 3(B) is not applied, when the output current exceeds the current limit of the vehicle power supply device, the control unit 30, which monitors the output current (current Iout) as described above, detects the abnormal current and applies a current limit to prevent any further output current from flowing. As a result, the voltage of the lower battery E2, shown by the solid line, falls below the average voltage of the lower battery E2, shown by the dashed line.

[0030] 3(C) is added, when the output current exceeds the current limit of the vehicle power supply device, the voltage of the lower battery E2 (shown by the solid line) falls below the average voltage of the lower battery E2 (shown by the dashed line), but once the output current falls within the current limit, the voltage of the lower battery E2 (shown by the solid line) exceeds the average voltage of the lower battery E2 (shown by the dashed line) for a while. In other words, the area of ​​the rectangle where the voltage of the lower battery E2 (shown by the solid line) falls below the average voltage of the lower battery E2 (shown by the dashed line) is equal to the area of ​​the trapezoid where the voltage of the lower battery E2 (shown by the solid line) exceeds the average voltage of the lower battery E2 (shown by the dashed line).

[0031] The integral term of I (integral control) in the conventional proportional control, integral control, and differential control (P, I, D) control is set to maintain the current output voltage at the output command voltage. Therefore, if the time constant of the integral term of I (integral control) in the conventional proportional control, integral control, and differential control (D) control is increased, the response to the target command voltage will deteriorate, and a voltage different from the desired output voltage will be output.

[0032] The vehicle power supply device 10 of the first embodiment adds feedback control 60 using averaging means 68 with a longer time period than the I control of the PID control integrator circuit 38 to the power supply circuit (FET1, FET2) that supplies power using P (proportional control), I (integral control), and D (differential control). As a result, in the short term, it is possible to output a voltage that is approximately the same as the target output voltage, and in the long term, it is possible to perform control to balance the batteries. Furthermore, by adding feedback control with a longer time period than the I (integral control) control of PID control, the battery voltage application time is matched to the delay time of the chemical reaction, and the upper and lower batteries are balanced, thereby reducing battery consumption and extending battery life.

[0033] One possible solution is to set the DC-DC converter with a capacity sufficiently larger than the output current being used, i.e., by strengthening the hardware, thereby eliminating the drop in output voltage and maintaining the average voltage. However, increasing the output capacity of the DC-DC converter creates the problem of increasing the size and cost of the vehicle power supply system. In contrast, the vehicle power supply system 10 of the first embodiment uses feedback control to maintain long-term battery balance, reduce battery consumption, and extend the battery's usable time.

[0034] FIG. 4 is a flowchart showing the processing in the averaging means 68 configured by a microcomputer (digital circuit). In step 12, the variable i is set to 1, and Vsum, which is in the process of calculating the average value, is initialized to 0. In step 14, it is determined whether the variable i is smaller than the total integral time x. The total integral time is set to, for example, one hour. If the variable i is smaller than the total integral time x (S14: Yes), the process proceeds to step 16.

[0035] In step 16, 1 is added to Vi, and Vsum becomes Vsum+Vi, i.e., the current voltage value Vi is added to the previous Vsum. 1 is added to variable i. In step 16, the past voltage value data of V1 to Vx are shifted and the sum is calculated.

[0036] In step 14, it is determined whether the variable i is smaller than the total integral time x. If the variable i is larger than or equal to the total integral time x (S14: No), the process proceeds to step 18.

[0037] In step 18, Vx is set to Vout (the current output voltage value), Vsum during the calculation of the average value is set to Vsum+Vout, and the target voltage value Vtarget is calculated as Vsum / x, which is the sum of the voltage values ​​for x. In other words, the latest voltage values ​​are summed and the average value is calculated.

[0038] In the vehicle power supply device of the first embodiment, the added feedback control is a long-term average control, so by matching the battery voltage application time with the chemical reaction delay time and balancing the upper and lower batteries, battery consumption can be reduced and battery life can be extended.

[0039] In the vehicle power supply device of the first embodiment, the long-term average value is calculated by calculation processing, so it is possible to accurately calculate the average over a long period of time, for example, about one hour.By matching the battery voltage application time with the chemical reaction delay time and balancing the upper and lower batteries, it is possible to reduce battery consumption and extend battery life.

[0040] In the vehicle power supply device of the first embodiment, the voltages of the upper battery E1 and the lower battery E2 are approximately equal, so the power supply circuit can charge the upper battery and the lower battery with a simple 50-50 duty.

[0041] [Modification of the first embodiment] FIG. 5 shows the configuration of a vehicle power supply device 110 according to a modified example of the first embodiment. The battery is divided into an upper battery E1 connected to the 48V high voltage VB side and a lower battery E2 connected to the earth EA side. The voltage of the upper battery E1 is 36V, and the voltage of the lower battery E2 is 12V. A 12V current Iout is output from the connection point CP between the upper battery E1 and the lower battery E2. A high voltage of 48V is supplied from the high voltage VB side. The upper battery E1 and the lower battery E2 are charged by PID control 50. A control signal with a duty of 25% is applied to FET1, which charges the upper battery E1 via coil L. A control signal with a duty of 75% is applied to FET2, which charges the lower battery E2 via coil L.

[0042] In a vehicle power supply device according to a modified example of the first embodiment, the voltage of the upper battery E1 is higher than the voltage of the lower battery E2. By adjusting the duty ratio of FET1 and FET2 according to the voltage, the upper battery E1 and the lower battery E2 can be charged.

[0043] [Second embodiment] FIG. 6 shows the configuration of a vehicle power supply device 210 according to the second embodiment. Duty control 150 applies a 50% duty signal to FET1, charging the upper battery E1 via coil L. Duty control 150 applies a 50% duty signal to FET2, charging the lower battery E2 via coil L. The feedback control 60 calculates a long-term average value using averaging means 68, which then compares the calculated average value with a reference voltage (target value) of V / 2 using a second operational amplifier OPD2, and the difference is added to a second summing node AN2. Based on the difference, duty control 150 adds or subtracts a 50% duty signal to FET1 and a 50% duty signal to FET2, thereby achieving long-term battery balance. [Explanation of symbols]

[0044] 10 Vehicle power supply unit 36 Differential circuit 38 Integrating circuit 50 PID control 60 Feedback Control 68 Averaging means EA Earth VB High voltage E1 upper battery E2 lower battery

Claims

1. a battery divided into an upper battery on the high voltage side and a lower battery on the low voltage side; a DC-DC converter that supplies power to the upper battery and the lower battery within a preset output limit, A vehicle power supply device further comprising a feedback control for feeding back the difference between the long-term average value of the output of the DC-DC converter and a target value.

2. 2. The vehicle power supply device of claim 1, The DC-DC converter supplies power by P (proportional control), I (integral control), and D (differential control) control, The long-term average value of the feedback control is an average value over a longer period of time than the I (integral control) control of the PID control.

3. 3. The vehicle power supply device of claim 2, The upper battery is connected to the high voltage side, and the lower battery is connected to the ground side; The DC-DC converter supplies power between the high-voltage side and the connection point between the upper battery and the lower battery, and between the connection point and the earth side, and the feedback control adds the difference between the long-term average value of the output of the DC-DC converter and a target value to the input side of the DC-DC converter.

4. 2. The vehicle power supply device of claim 1, The voltages of the upper and lower batteries are approximately equal.

5. 2. The vehicle power supply device of claim 1, The voltage of the upper battery is higher than the voltage of the lower battery.

6. The vehicle power supply device according to claim 5, The long-term average value is determined by calculation.

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