Power conversion device and power conversion system

Abstract

In order to realize miniaturization of a power conversion device, the power conversion device of the present application includes: a main circuit section having a voltage conversion circuit provided with a switching element and a capacitor; a voltage sensor that detects a voltage of the capacitor; and a control unit that controls an operation of the switching element based on a voltage value detected by the voltage sensor, the voltage sensor including: a voltage dividing circuit that converts a high potential to a low potential; an isolation circuit that insulates and outputs a digital signal corresponding to an output of the voltage dividing circuit; and a filter circuit that converts the digital signal output from the isolation circuit to an analog value, the control unit including a converter that acquires the analog value output from the filter circuit and converts it to a digital value.

Description

Technical Field

[0001] This application relates to power conversion devices and power conversion systems. Background Technology

[0002] The power conversion device converts the DC power from a DC power source such as a battery into AC power to drive a motor. On the other hand, it converts the AC power generated by the motor into DC power to supply the DC power source such as a battery.

[0003] In power conversion devices, the need for high-speed boost voltage control allows for the miniaturization of capacitors assembled within the device. Therefore, high-precision, high-response voltage sensors are required to achieve high-response control. On the other hand, with the increasing voltage of batteries, high insulation must be ensured between the main power conversion circuit (high-voltage side) and the control unit (low-voltage side). Furthermore, voltage sensors also require high insulation properties.

[0004] Therefore, as a voltage sensor for power conversion devices, voltage detection accuracy is improved while ensuring insulation. For example, in the voltage detection device (voltage sensor) shown in Patent Document 1, as a structure that transmits information related to the voltage detected by the main circuit section (high voltage side) to the control section side (low voltage side), it includes a voltage divider circuit that divides the detected voltage value, and a processing circuit that processes the voltage value after voltage division by the voltage divider circuit. In the processing circuit, the voltage value is converted into a digital value corresponding to the voltage value from the voltage divider circuit, and the converted digital value is output through an insulation circuit.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6448077 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, in the power conversion device shown in Patent Document 1 above, the signal input to the control unit (e.g., a microcomputer) is a digital signal. Therefore, if the digital signal is made more frequent, even if a high response is achieved, the accuracy of the obtained voltage information will decrease due to the limitation of the acquisition resolution of the digital signal of the control unit.

[0010] This application was made to solve the above-mentioned problems, and its purpose is to provide a power conversion device with a voltage sensor that enables the miniaturization of capacitors and achieves high responsiveness and high insulation.

[0011] Technical means for solving technical problems

[0012] The power conversion device disclosed in this application includes: a main circuit section having a voltage conversion circuit with switching elements and a capacitor; a voltage sensor for detecting the voltage of the capacitor; and a control unit for controlling the operation of the switching elements based on the voltage value detected by the voltage sensor. The power conversion device is characterized in that the voltage sensor includes: a voltage divider circuit for converting a high potential to a low potential; an isolation circuit for isolating a digital signal corresponding to the output of the voltage divider circuit; and a filter circuit for converting the digital signal output from the isolation circuit into an analog value. The control unit includes a converter that acquires the analog value output from the filter circuit and converts it into a digital value.

[0013] Invention Effects

[0014] According to the power conversion device disclosed in this application, voltage information obtained by simulating a digital output is acquired and then converted into a digital value, thereby achieving high responsiveness and high insulation. Attached Figure Description

[0015] Figure 1 This is a circuit diagram of the power conversion device involved in Embodiment 1.

[0016] Figure 2 This is a structural diagram illustrating an example of the hardware of the control circuit involved in Implementation Method 1.

[0017] Figure 3A It is a waveform diagram showing the operation of the power conversion device according to Embodiment 1.

[0018] Figure 3B It is a waveform diagram showing the operation of the power conversion device according to Embodiment 1.

[0019] Figure 4 This is a block diagram illustrating the voltage sensor involved in Embodiment 1.

[0020] Figure 5 This is an explanatory diagram showing the signal conversion of the insulation circuit involved in Embodiment 1.

[0021] Figure 6 This is a structural diagram of the filter circuit involved in Implementation Method 1.

[0022] Figure 7 This is a circuit diagram of the power conversion device involved in Embodiment 2.

[0023] Figure 8 This is an explanatory diagram of the operation mode of the power conversion device according to Embodiment 2.

[0024] Figure 9AIt is a waveform diagram showing the operation of the power conversion device involved in Embodiment 2.

[0025] Figure 9B It is a waveform diagram showing the operation of the power conversion device involved in Embodiment 2.

[0026] Figure 10 This is a block diagram of the voltage sensor involved in Embodiment 2. Detailed Implementation

[0027] Implementation method 1.

[0028] The power conversion device according to Embodiment 1 is described with reference to the accompanying drawings. Figure 1 This describes the structure of a power supply system in which a power conversion device 3 is connected between battery 1 and load 2. That is, the power conversion device 3 is a DC / DC converter with the battery 1 connected to its input terminal and the load 2 connected to its output terminal, configured to boost the voltage of battery 1 to the voltage of load 2 for power supply.

[0029] The power conversion device 3 is divided into a main circuit section 30 for power conversion and a control unit 35 for controlling the main circuit section 30. The main circuit section 30 includes a reactor 31, a first voltage conversion circuit 32, a current sensor 34, a control unit 35, a first smoothing capacitor 36 (C2), a second smoothing capacitor 37 (C1), a first voltage sensor 39, and a second voltage sensor 38.

[0030] The reactor 31 includes a first terminal and a second terminal, with the first terminal connected to the high-potential side terminal of the battery 1. The control unit 35 controls the first voltage conversion circuit 32, the first voltage sensor 39 detects the voltage V2 applied to the first smoothing capacitor 36 (C2), and the second voltage sensor 38 detects the voltage V1 applied to the second smoothing capacitor 37 (C1).

[0031] The first voltage conversion circuit 32 has a structure in which a first switching element 32a and a second switching element 32b are connected in series at a first connection portion 32c and connected in parallel to the load 2. That is, one terminal of the first switching element 32a is connected to the low-potential side terminal of the battery 1, the second switching element 32b is connected to the high-potential side terminal of the load 2, and the first connection portion 32c is connected to the second terminal of the reactor 31. Diodes are respectively provided in parallel on the first switching element 32a and the second switching element 32b.

[0032] The first smoothing capacitor 36 (C2) is connected in parallel with the load 2, and the second smoothing capacitor 37 (C1) is connected in parallel with the battery 1.

[0033] A current sensor 34 is disposed between the reactor 31 and the first connection part 32c to detect the current value IL flowing to the reactor 31.

[0034] The voltage information V2_analog detected by the first voltage sensor 39, the voltage information V1_PWM detected by the second voltage sensor 38, and the current value IL_sen detected by the current sensor 34 are respectively input into the control unit 35.

[0035] Figure 1 The power system shown is installed, for example, in an electric vehicle, where battery 1 uses a high-voltage (100V or higher) lithium-ion battery. On the other hand, control unit 35 is driven by an auxiliary power source, namely a lead-acid battery (less than 100V), and is located in a place accessible to vehicle users. From the viewpoint of preventing electric shock to vehicle users, the high-voltage side (first reference potential 3a), including battery 1, power conversion device 3, and load 2, is insulated from the low-voltage side (second reference potential 3b), including the lead-acid battery and control unit 35. Therefore, the first voltage sensor 39, the second voltage sensor 38, the current sensor 34, and the gate drive signals driving the first switching element 32a and the second switching element 32b, which connect the high-voltage and low-voltage sides, are all configured to insulate the high-voltage side (first reference potential 3a) from the low-voltage side (second reference potential 3b). For example, in the case of current sensor 34, it is configured to perform current detection utilizing the Hall effect.

[0036] In addition, such as Figure 2 As shown in the example of hardware, the control circuit 35 consists of a processor 100 and an on-board unit 101. Although the storage device is not shown, it includes volatile storage devices such as random access memory and non-volatile auxiliary storage devices such as flash memory. Alternatively, an auxiliary storage device such as a hard disk can be used instead of flash memory. The processor 100 executes a program input from the storage device 101. In this case, the program is input to the processor 100 from the auxiliary storage device via the volatile storage device. Furthermore, the processor 100 can output data such as calculation results to the volatile storage device of the storage device 101, and can also save data to the auxiliary storage device via the volatile storage device.

[0037] Next, the operating waveform of the power conversion device 3 is shown. Figure 3A and Figure 3B . Figure 3A This indicates the waveform when the duty cycle is below 0.5, i.e., the boost ratio is below 2. Figure 3BThe waveforms represent the duty cycle of 0.5 or higher, i.e., the boost ratio of 2 or higher. The top waveform represents the drive carrier (carrier) set by the control unit 35 to control the drive frequency of the first switching element 32a and the second switching element 32b. The second waveform represents the gate drive signal Gate_SL of the first switching element 32a. The third waveform represents the gate drive signal Gate_SH of the second switching element 32b. The fourth waveform represents the current value IL flowing to the reactor 31. The fifth waveform represents the current value Ic2 flowing to the first smoothing capacitor 36 (C2). The sixth waveform represents the voltage V2 applied to the first smoothing capacitor 36 (C2).

[0038] As shown in the figure, the first switching element 32a and the second switching element 32b of the power conversion device 3 are controlled by the gate drive signals generated by the control unit 35. The gate drive signals (Gate_SL, Gate_SH) are generated to control the on / off (opening and closing) of the first switching element 32a and the second switching element 32b respectively, thereby controlling the voltage V2 applied to the load.

[0039] Here, the driving carrier is a triangular wave, and the period from the peak of the triangular wave to the next peak, or from the trough to the next trough, is one-tenth of the driving frequency of the switching element (Tsw = 1 / fsw, fsw: driving frequency). The switching mode is assumed to be such that the first switching element 32a and the second switching element 32b connected in series will not be turned on simultaneously. The duty cycle in the DC / DC converter of the power conversion device 3 is defined by the on-time ratio of Gate_SL within one cycle (Duty = Ton_L / Tsw), and the boost voltage is generally calculated using the following equation (1).

[0040] V2=1 / (1-Duty)×V1 (1)

[0041] like Figure 3A and Figure 3BAs shown, the reactor current increases when the gate drive signal Gate_SL of the first switching element 32a is turned on, and the reactor current charges the first smoothing capacitor 36 (C2) when the gate drive signal Gate_SL of the first switching element 32a is turned off, resulting in a voltage waveform of the pulsating voltage V2rip that is repeated in each cycle of the driving carrier. The voltage V2 applied to the first smoothing capacitor 36 (C2) passes near the average value V2ave of the voltage V2 at the midpoint between the midpoint of the period when the gate drive signal Gate_SL of the first switching element 32a is turned on and the midpoint of the period when the gate drive signal Gate_SL of the first switching element 32a is turned off. The midpoints of the turning on and off of the gate drive signal Gate_SL of the first switching element 32a are equivalent to the timing of the peaks and troughs of the driving carrier.

[0042] Here, if the control unit 35 has an AD converter, and the acquisition frequency of the AD converter is set to fad and the switching frequency is set to fsw, then the relationship between the acquisition frequency and the switching frequency is set as follows (2).

[0043] fad≧fsw (2)

[0044] By configuring it in this way, the hysteresis caused by using an AD converter to convert analog voltage information into digital signals can be suppressed to within the switching cycle.

[0045] Next, based on Figure 4 The structures of the first voltage sensor 39 and the second voltage sensor 38 will be described.

[0046] First, the first voltage sensor 39 includes a voltage divider circuit 391, an insulation circuit 392, and a filter circuit 393. The voltage divider circuit 391 is configured to divide the voltage V2 applied to the first smoothing capacitor 36 (C2) to output a lower voltage V2_Low. The insulation circuit 392 is configured to insulate the high voltage side (first reference potential 3a) from the low voltage side (second reference potential 3b) and output a PWM waveform V2_PWM with a duty cycle corresponding to the input value V2_Low. The filter circuit 393 is configured to input the digital signal, i.e., the PWM waveform V2_PWM, and convert it into an analog signal, i.e., V2_analog.

[0047] The analog signal V2_analog output from the filter circuit 393 is input to the control unit 35. The AD converter 394 in the control unit 35 uses the timing value obtained at the peak, trough or both of the driving carrier wave to obtain the value, and uses it as the V2 voltage detection signal in the control unit 35 for the output voltage control of the DC / DC converter. Here, the relationship between the frequency fpwm(V2) of the PWM waveform of the isolation circuit 392 and the frequency fsw of the driving carrier wave is given by the following equation (3).

[0048] fpwm(V2)>fsw (3)

[0049] Therefore, the frequency of the PWM waveform of the insulation circuit 392 of the first voltage sensor 39 is set to be higher than the driving frequency (e.g., more than 10 times), thereby enabling the... Figure 3A or Figure 3B During the transmission of voltage V2 information to control unit 35, when it is converted into a digital signal (discretized) in insulating circuit 392, the information of V2rip and the relationship between V2ave and the driving carrier remain unchanged during transmission. Therefore, the V2 voltage information acquired by AD converter 394 becomes a digital signal with high accuracy. Figure 2 The value of V2ave is equivalent to that in the equation. This V2 voltage information is used for feedback control, thereby enabling high-response control.

[0050] Next, the second voltage sensor 38 includes a voltage divider circuit 381 and an insulation circuit 382. The voltage divider circuit 381 divides the voltage V1 applied to the second smoothing capacitor 37 (C1) to output a lower voltage V1_Low. The insulation circuit 382 is configured to insulate the high voltage side (first reference potential 3a) from the low voltage side (second reference potential 3b) and output the PWM waveform V1_PWM with a duty cycle corresponding to the input value V1_Low.

[0051] The digital signal V1_PWM output from the insulation circuit 382 of the second voltage sensor 38 is input to the control unit 35. The edge detector 384 of the control unit 35 is used to detect the rising and falling edges, calculate the duty cycle of V1_PWM, and use it as the V1 voltage detection signal in the microcomputer for the control of the DC / DC converter. The edge detector 384 of the control unit 35 (microcomputer) has an edge detection resolution (Tedg). In order to ensure the accuracy of V1 voltage detection, the frequency of the PWM waveform of the insulation circuit 382 is set to the following equation (4).

[0052] fpwm(V1) << 1 / Tedg (4)

[0053] Next, an example of the input-output signal conversion diagram of the insulation circuit 392 of the first voltage sensor 39 is shown. Figure 5 The circuit conditions that presuppose this concept are shown below.

[0054] The high-voltage side input voltage range of the insulation circuit 392 is 0–5V.

[0055] V2 voltage detection range: 0~1000V

[0056] The normal duty cycle output range of the insulating circuit 392 is 10%–90%.

[0057] The input value V2 (0~1000V) is converted into the output value V2_Low (1~4V) using the voltage divider circuit 391.

[0058] The insulation circuit 392 of the first voltage sensor 39 is used to output V2_PWM with a duty cycle corresponding to V2_Low.

[0059] At this time, if an abnormality such as a power supply short circuit or a ground short circuit occurs in the voltage divider circuit 391 of the first voltage sensor 39, since V2_Low is input with 0V or 5V, the duty cycle of V2_PWM becomes 0% or 100%. Because the value obtained by acquiring V2_analog using the AD converter 394 is bound to the upper or lower limit, after acquiring the V2 voltage information using the AD converter 394, abnormalities in the high-voltage side circuit can be detected. Then, in the event of a fault in the voltage divider circuit 391 where the voltage value of a power supply short circuit or a ground short circuit cannot be detected, a predetermined duty cycle value is output.

[0060] The insulation circuit 382 of the second voltage sensor 38 also performs the same conversion. In the event of an abnormality on the high-voltage side, V1_PWM becomes 0% or 100% and no edge can be detected. Therefore, after obtaining the V1 voltage information using the edge detector 384, the abnormality of the high-voltage side circuit can be detected.

[0061] Here, the insulation circuit 392 of the first voltage sensor 39 has the function of isolating the high-voltage side (first reference potential 3a) and the low-voltage side (second reference potential 3b), requiring power supplies for each reference potential. By setting the power supply of the low-voltage side (second reference potential 3b) of the insulation circuit 392 to be the same as the reference power supply of the AD converter 394 of the control unit 35, the errors caused by the power supply when acquiring V2_analog using the AD converter 394 are mutually canceled, thus improving the voltage acquisition accuracy. As an example, when the potential difference between the reference power supply of the AD converter 394 and the low-voltage side voltage of the insulation circuit 392 is 1%, the error of the voltage acquisition value increases by about 1%. Therefore, it is necessary to set the potential difference to be below the required accuracy of the voltage acquisition value.

[0062] Next, the structure of filter circuit 393 will be explained. Figure 6 This is a circuit diagram of an example of filter circuit 393. A total of three stages of low-pass filter circuits are constructed, consisting of a first filter circuit composed of a first resistor 3931 and a first capacitor 3932, a second filter circuit composed of a second resistor 3933 and a second capacitor 3934, and a third filter circuit composed of a third resistor 3935 and a third capacitor 3936. The input is V2_PWM, which has a duty cycle corresponding to the output V2 from the isolation circuit 392 of the first voltage sensor 39, and the output is an analog value V2_analog after removing the PWM frequency component of the isolation circuit 392. At this time, the cutoff frequency flpf of the low-pass filter circuit is set higher than the frequency fsw of the driving carrier, as shown in equation (5) below.

[0063] fpwm(V2)>flpf>fsw (5)

[0064] The cutoff frequency flpf of the low-pass filter circuit is set as shown in the above formula, thereby maintaining... Figure 3A and Figure 3B The voltage information V2rip of the capacitor voltage V2 shown remains unchanged, as does the positional relationship between the driving carrier and V2ave. Only the fpwm frequency component is removed, and V2_analog is output. Additionally, as... Figure 6 This structure forms a high-order low-pass filter circuit (multiple filter circuits connected in series), so that even when the values ​​of fpwm(V2) and fsw are close, the necessary V2 voltage information will not be attenuated by the filter circuit 393.

[0065] In the description so far, the voltage divider circuit, the insulation circuit, and the filter circuit have been described as independent functional modules. However, for example, they can also be constructed using an integrated circuit (IC) that integrates any two or more functions into a single electronic component.

[0066] In the above description, the following was explained first: the voltage V2 of the first smoothing capacitor is the control object of the feedback control of the DC / DC converter. In addition, the voltage V2 applied to the first smoothing capacitor 36 (C2) has a pulsating component V2rip that depends on the driving frequency. Therefore, it is obtained synchronously with the driving frequency by the AD converter 394 via the voltage divider circuit 391 → insulation circuit 392 → filter circuit 393. However, the voltage V1 applied to the second smoothing capacitor 37 (C1) can also obtain voltage information with the same structure.

[0067] In addition, while the DC / DC converter was described in Embodiment 1, the power conversion device 3 may also be an inverter circuit that converts DC to AC to drive a motor, and the voltage applied to the smoothing capacitor may also be the DC input voltage of the inverter circuit.

[0068] Furthermore, while the timing for acquiring voltage information using the AD converter 394 has been described as being at the midpoint between the gate-on and gate-off periods, in cases where the load of load 2 is small or the capacitance of the first smoothing capacitor 36 is large and voltage ripple is small, the timing for acquiring voltage information using the AD converter 394 does not necessarily have to be at the midpoint of these periods. Moreover, even in cases of large ripple, by averaging the peak and trough values ​​of the drive carrier wave, the acquired voltage information can be made close to the average value of the voltage including ripple, achieving the same effect as being at the midpoint between the gate-on and gate-off periods.

[0069] The on-time (the period of transition from gate off to on) and off-time (the period of transition from gate on to off) of a switching element are susceptible to noise or voltage fluctuations caused by switching surges. Therefore, the timing for acquiring voltage information is set to at least avoid the on-time or off-time.

[0070] Assuming the power conversion device 3 is, for example, a DC / DC converter that controls the input voltage of an inverter, whereby the inverter controls the generator motor or drive motor mounted in an electric vehicle. An electric vehicle refers to a vehicle that can operate using electrical energy, such as a hybrid electric vehicle, an electric vehicle, or a plug-in hybrid electric vehicle. Considering that the motors in these electric vehicles may experience sudden changes in torque or speed due to slippage on icy roads, rapid acceleration / deceleration, motor lock-up, etc., the DC / DC converter is typically controlled to the desired voltage. However, due to the sudden change in load power, and given the slow response speed of the DC / DC converter, the voltage V2 of the second smoothing capacitor 37 may also change abruptly.

[0071] In cases where voltage V2 changes abruptly, a deterioration in inverter controllability or an overvoltage of voltage V2 may be detected, causing the DC / DC converter to stop. Therefore, countermeasures such as increasing the electrostatic capacitance of the capacitors are taken, but this results in a problem of increasing the size of the power conversion device.

[0072] This application can address even problems like these. That is, by assembling the power conversion device of this application as a power conversion system, the control speed of the DC voltage of the DC / DC converter is set to be faster than the change speed of the DC voltage caused by the load change of the inverter. As a result, the change of voltage V2 relative to the load change can be suppressed, and high-speed voltage control can be achieved.

[0073] Implementation method 2.

[0074] The power conversion device 3 according to Embodiment 2 will be described with reference to the accompanying drawings. Figure 7 This is a circuit diagram showing the power conversion device 3 and its peripheral circuits, namely battery 1 and load 2. Figure 8 Figure 9 is a circuit diagram showing the operation mode of the power conversion device 3 (multilevel boost converter circuit) in Embodiment 2. Figure 7 The waveforms of the driving carrier, gate driving signal, pulsating current, capacitor current, and capacitor voltage of the switching element. Figure 10 It means Figure 7 The circuit diagram (block diagram) shows the structure of the first voltage sensor 39, the second voltage sensor 38, and the third voltage sensor 352.

[0075] like Figure 7 As shown, the power conversion device 3 is a DC / DC converter with a battery 1 connected to its input terminal and a load 2 connected to its output terminal. The difference from Embodiment 1 is that the DC / DC converter is a multi-level converter equipped with a charge / discharge capacitor 351 (C0).

[0076] In Embodiment 2, the differences from Embodiment 1 will be explained.

[0077] The power conversion device 3 includes a reactor 31, a second voltage conversion circuit 33, a current sensor 34, a control unit 35 for controlling the second voltage conversion circuit 33, a first smoothing capacitor 36 (C2), a first voltage sensor 39 for detecting the voltage V2 applied to the first smoothing capacitor 36 (C2), a second smoothing capacitor 37 (C1), a second voltage sensor 38 for detecting the voltage V1 applied to the second smoothing capacitor 37 (C1), a charge / discharge capacitor 351 (C0), and a third voltage sensor 352 for detecting the voltage V0 applied to the charge / discharge capacitor 351 (C0).

[0078] The reactor 31 includes a first terminal and a second terminal, with the first terminal connected to the high-potential side terminal of the battery 1.

[0079] The second voltage conversion circuit 33 is connected in parallel with the load 2. The second voltage conversion circuit 33 has the following structure: the first switching element 33a (S1), the second switching element 33b (S2), the third switching element 33c (S3), and the fourth switching element 33d (S4) are connected in series. The connection point between the first switching element 33a and the second switching element 33b is set as the first connection part 33f, the connection point between the second switching element 33b and the third switching element 33c is set as the second connection part 33e, and the connection point between the third switching element 33c and the fourth switching element 33d is set as the third connection part 33g.

[0080] The terminal of the first switching element 33a is connected to the terminal on the low potential side of the battery 1, and the terminal of the fourth switching element 33d is connected to the terminal on the high potential side of the load 2.

[0081] The second connection part 33e is connected to the second terminal of the reactor 31. The first to fourth switching elements 33a, 33b, 33c, and 33d are each equipped with a diode connected in parallel.

[0082] The first smoothing capacitor 36 (C2) is connected in parallel with the load 2, the second smoothing capacitor 37 (C1) is connected in parallel with the battery 1, and the charging and discharging capacitor 351 is connected to the first connecting part 33f and the third connecting part 33g.

[0083] A current sensor 34 is disposed between the reactor 31 and the first connection portion 33f to detect the current value IL flowing to the reactor 31.

[0084] The voltage information V2_analog detected by the first voltage sensor 39, the voltage information V1_PWM detected by the second voltage sensor 38, the voltage information V0_analog detected by the third voltage sensor 352, and the current value IL_sen detected by the current sensor 34 are respectively input into the control unit 35.

[0085] Next, use Figure 8 (a)~(d), for Figure 7 The operating mode of the second voltage conversion circuit 33 shown will be explained.

[0086] exist Figure 8 In (a) to (d), the first switching element 33a is shown as S1, the second switching element 33b is shown as S2, the third switching element 33c is shown as S3, and the fourth switching element 33d is shown as S4.

[0087] like Figure 8As shown in (a) to (d), the first to fourth switching elements S1 to S4 have four opening and closing modes, i.e., four operating modes: mode 1 to mode 4. In the power operation when power is supplied from battery 1 to load 2, and in the regenerative operation when power is supplied from load 2 to battery 1, there is a difference between using the switching elements and using the parallel diodes. However, the current path, shown by the dashed line, is the same. Therefore, this explanation focuses on the power operation.

[0088] In mode 1, such as Figure 8 As shown in (a), the first switching element S1 and the third switching element S3 are turned on, while the second switching element S2 and the fourth switching element S4 are turned off. As shown by the dashed line in the figure, the current path is such that the current flows through the diode D3 connected in parallel with the first switching element S1 and the third switching element S3, and the energy is stored in the charge-discharge capacitor 351 (C0).

[0089] In mode 2, such as Figure 8 As shown in (b), the first switching element S1 and the third switching element S3 are disconnected, while the second switching element S2 and the fourth switching element S4 are connected. This operation results in a state where current flows through the second switching element S2 and the diode D4 connected in parallel with the fourth switching element, releasing the energy of the charging / discharging capacitor 351(C0).

[0090] In mode 3, such as Figure 8 As shown in (c), the first switching element S1 and the second switching element S2 are disconnected, while the third switching element S3 and the fourth switching element S4 are connected. This operation results in a state where current flows through the diode D3 connected in parallel with the third switching element and the diode D4 connected in parallel with the fourth switching element, releasing the energy of the reactor 31.

[0091] In mode 4, such as Figure 8 As shown in (d), the first switching element S1 and the second switching element S2 are turned on, while the third switching element S3 and the fourth switching element S4 are turned off. This operation results in the following state: current flows through the first switching element S1 and the second switching element S2, accumulating energy in the reactor 31.

[0092] By appropriately adjusting the time ratios of these operating modes, the voltage V2 applied to the load 2 can be controlled, and the voltage applied to the reactor 31 can be reduced by controlling the voltage V0 applied to the charging / discharging capacitor 351 (C0) to half of V2.

[0093] Next, the operating waveforms of the power conversion device 3 are shown in Figure 9. The first to fourth switching elements 33a, 33b, 33c, and 33d of the power conversion device 3 are controlled by the gate drive signals (Gate_S1, Gate_S2, Gate_S3, and Gate_S4) generated by the control unit 35 to control the voltage V2 applied to the load 2 and the voltage V0 applied to the charging and discharging capacitor 351.

[0094] Next, the operating waveform of the power conversion device 3 is shown. Figure 9A and Figure 9B .exist Figure 9A and Figure 9B The explanation begins from the top segment of the action waveform. The topmost waveform represents the drive carrier (carrier) set by the control unit 35. Gate_S1 represents the gate drive signal of the first switching element 33a, Gate_S2 represents the gate drive signal of the second switching element 33b, Gate_S3 represents the gate drive signal of the third switching element 33c, Gate_S4 represents the gate drive signal of the fourth switching element 33d, the current value IL represents the current flowing to the reactor 31, the current Ic0 represents the current flowing to the charging / discharging capacitor 351, the voltage V0 represents the voltage applied to the charging / discharging capacitor 351, the current Ic2 represents the current flowing to the first smoothing capacitor 36, and the voltage V2 represents the voltage applied to the first smoothing capacitor.

[0095] The gate drive signal is set so that the first switch element 33a (S1) and the fourth switch element 33d (S4), the second switch element 33b (S2) and the third switch element 33c (S3) will not be turned on at the same time. The first switch element 33a (S1) and the second switch element 33b (S2) are set to a switching mode in which the turn-on time is equivalent but the phase is staggered for half a cycle of the drive carrier.

[0096] Figure 9A This indicates a waveform where the duty cycle is below 0.5, i.e., the boost ratio is below 2, repeating pattern 1 → pattern 3 → pattern 2 → pattern 3. Figure 9B This indicates a waveform where the duty cycle is 0.5 or higher, i.e., the boost ratio is 2 or higher, repeating pattern 1 → pattern 4 → pattern 2 → pattern 4.

[0097] In both modes, only the charging and discharging capacitor 351 (C0) is charged in mode 1, the charging and discharging capacitor 351 (C0) is discharged and the first smoothing capacitor 36 (C2) is charged in mode 2, and the first smoothing capacitor 36 (C2) is charged in mode 3.

[0098] In this embodiment 2, as in embodiment 1, the voltage V0 applied to the charge / discharge capacitor 351 (C0) and the voltage V2 applied to the first smoothing capacitor 36 (C2) become voltage waveforms containing pulsating voltages that are repeated in each cycle of the driving carrier.

[0099] Voltages V0 and V2 both pass near their average values ​​V2ave and V0ave at the midpoints of the periods when Gate_S1 is on and off. Furthermore, the midpoints of Gate_S1's on and off states are equivalent to the timing of the peaks and troughs of the driving carrier wave.

[0100] Next, based on Figure 10 The structures of the first voltage sensor 39 and the second voltage sensor 38 in Embodiment 2 will be described.

[0101] First, the first voltage sensor 39 and the second voltage sensor 38 have the same structure as in Embodiment 1. The third voltage sensor 352 includes a voltage divider circuit 3521, an insulation circuit 3522, and a filter circuit 3523. The voltage V0 is the same as the voltage V2 and is the control object of the feedback control of the multilevel converter. In addition, it has a pulsating component V0rip that depends on the driving frequency. Therefore, it has the following structure: voltage information is acquired synchronously with the driving frequency via the AD converter 3524 through the voltage divider circuit 3521 → insulation circuit 3522 → filter circuit 3523.

[0102] Although this application describes various exemplary embodiments and examples, the various features, methods and functions described in one or more embodiments are not limited to the application of a particular embodiment and can be applied to the embodiment individually or in various combinations.

[0103] Therefore, numerous variations not illustrated are conceivable within the scope of the technology disclosed in this application. For example, this could include variations, additions, or omissions of at least one constituent element, or the extraction of at least one constituent element and its combination with constituent elements of other embodiments.

[0104] Label Explanation

[0105] 1 Battery

[0106] 2. Load

[0107] 3 Power conversion device

[0108] 30 Main Circuit Section

[0109] 31 Reactor

[0110] 32 First Voltage Conversion Circuit

[0111] 33 Second voltage conversion circuit

[0112] 34 Current Sensor

[0113] 35 Control Unit

[0114] 36 First smoothing capacitor

[0115] 37 Second smoothing capacitor

[0116] 38 Second voltage sensor

[0117] 39 First Voltage Sensor

[0118] 100 processors

[0119] 101 Storage device

[0120] 351 charging and discharging capacitor

[0121] 352 Third Voltage Sensor

[0122] 381 voltage divider circuit

[0123] 382 Insulated Circuit

[0124] 384 edge detector

[0125] 391 voltage divider circuit

[0126] 392 Insulated Circuit

[0127] 393 Filter Circuit

[0128] 394 AD converter

[0129] 3521 voltage divider circuit

[0130] 3522 Insulated Circuit

[0131] 3523 Filter Circuit

[0132] 3524 AD converter.

Claims

1. A power conversion device, the power conversion device comprising: The main circuit section includes a voltage conversion circuit and a capacitor, wherein the voltage conversion circuit has a switching element; A voltage sensor that detects the voltage of the capacitor; The power conversion device is characterized by a control unit that controls the operation of the switching element based on the voltage value detected by the voltage sensor. The voltage sensor includes: A voltage divider circuit that converts a high potential to a low potential; An insulating circuit, which isolates the output PWM signal with a duty cycle corresponding to the output of the voltage divider circuit; and A filter circuit that filters the PWM signal output from the insulation circuit and converts it into an analog value. The control unit includes a converter that converts the analog value output from the filter circuit into a digital value. The timing of the converter in the control unit acquiring the analog value is synchronized with the drive cycle of the switching element. The frequency of the PWM signal output by the insulating circuit is higher than the driving frequency of the switching element.

2. The power conversion device as described in claim 1, characterized in that, The main circuit section is a DC / DC converter having a reactor, the switching element, and the capacitor.

3. The power conversion device as described in claim 2, characterized in that, The filter circuit is a low-pass filter circuit composed of resistors and capacitors. The frequency of the PWM signal output by the insulating circuit is higher than the cutoff frequency of the low-pass filter circuit, and the cutoff frequency is higher than the driving frequency of the switching element.

4. The power conversion device as described in claim 3, characterized in that, The low-pass filter circuit is a high-order low-pass filter circuit composed of multiple stages connected in series.

5. The power conversion device as described in claim 1, characterized in that, The filter circuit is a low-pass filter circuit composed of resistors and capacitors. The frequency of the PWM signal output by the insulating circuit is higher than the cutoff frequency of the low-pass filter circuit, and the cutoff frequency is higher than the driving frequency of the switching element.

6. The power conversion device as described in claim 5, characterized in that, The low-pass filter circuit is a high-order low-pass filter circuit composed of multiple stages connected in series.

7. The power conversion device according to any one of claims 1 to 6, characterized in that, The switching element is driven by PWM control, and the timing of the converter in the control unit to acquire the analog value is set to avoid the on or off period of the switching element.

8. The power conversion device as described in claim 7, characterized in that, The timing at which the converter acquires the analog value is the center of the period during which the gate of the switching element is turned on or the center of the period during which the gate of the switching element is turned off.

9. The power conversion device as described in claim 2, characterized in that, The switching element is a switching element composed of a first switching element, a second switching element, a third switching element, and a fourth switching element connected in series. The capacitor comprises: a first capacitor connected to the DC input section of the main circuit section; a second capacitor connected to the connection section between the first and second switching elements, and the connection section between the third and fourth switching elements; and a third capacitor connected to the DC input section and also connected to the low-voltage side of the first switching element and the high-voltage side of the fourth switching element. The reactor is a reactor whose one end is connected to the high-voltage side terminal of the first capacitor and whose other end is connected to the connection portion of the third and fourth switching elements. The first switching element and the fourth switching element switch alternately. The second and third switching elements switch alternately. The first switching element and the second switching element are driven in a state where the phase is shifted by half a cycle of the driving frequency of the switching element. The voltage sensor detects the voltage value of the first capacitor, the voltage value of the second capacitor, or the voltage value of the third capacitor.

10. The power conversion device according to any one of claims 1 to 6, 8, and 9, characterized in that, The insulation circuit outputs a duty cycle corresponding to the voltage value output from the voltage divider circuit. When the voltage value of a power supply short circuit or a ground short circuit cannot be detected in the voltage divider circuit, the predetermined duty cycle value is output.

11. The power conversion device as claimed in claim 7, characterized in that, The insulation circuit outputs a duty cycle corresponding to the voltage value output from the voltage divider circuit. When the voltage value of a power supply short circuit or a ground short circuit cannot be detected in the voltage divider circuit, the predetermined duty cycle value is output.

12. The power conversion device according to any one of claims 1 to 6, 8, 9, and 11, characterized in that, The insulating circuit has a power supply for a reference potential on the high-voltage side and a power supply for a reference potential on the low-voltage side, and the power supply for the reference potential on the low-voltage side is set to be the same as the reference potential of the converter of the control unit.

13. The power conversion device as claimed in claim 7, characterized in that, The insulating circuit has a power supply for a reference potential on the high-voltage side and a power supply for a reference potential on the low-voltage side, and the power supply for the reference potential on the low-voltage side is set to be the same as the reference potential of the converter of the control unit.

14. The power conversion device as claimed in claim 10, characterized in that, The insulating circuit has a power supply for a reference potential on the high-voltage side and a power supply for a reference potential on the low-voltage side, and the power supply for the reference potential on the low-voltage side is set to be the same as the reference potential of the converter of the control unit.

15. A power conversion system, characterized in that, The power conversion device as described in any one of claims 1 to 14 is mounted in an automobile as part of a power conversion system of a DC / DC converter, wherein the DC / DC converter controls the DC voltage applied to an inverter that controls a generator motor or a drive motor, and the power conversion system sets the control speed of the DC voltage of the DC / DC converter to be faster than the rate of change of the DC voltage caused by the load change of the inverter, and controls the output voltage of the DC / DC converter to be constant.

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