JP5223396B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device, and more particularly to noise suppression of a power conversion device disposed in the vicinity of a radio receiver such as a radio.

  In a power converter, it is known that electromagnetic wave noise is generated when a switching element is opened and closed, which may be a problem when a radio receiver such as a radio exists in the vicinity. For this reason, in a hybrid vehicle or the like equipped with a radio receiver such as a radio, a technique for improving the reception state of the radio receiver has been proposed.

  For example, Patent Document 1 shown below discloses that the surge voltage during switching is suppressed by slowing down the switching speed of the switching element to reduce the noise level.

JP 2005-168171 A

  However, although the surge voltage can be suppressed by slowing the switching speed, there is a problem that the power loss at the time of switching corresponding to the product of the switching current and the switching voltage increases. 5 and 6 show power loss during switching. FIG. 5 shows power loss when the switching speed is normal, and FIG. 6 shows power loss when the switching speed is slow. In both figures, the horizontal axis represents time, and the vertical axis represents the gate control signal GS, switching current Isw, switching voltage Vsw, and power loss applied to the gate of the switching element. This is the case where the gate control signal GS is switched from Low to Hi at time t1 and the switching element is turned on, and at time t2 the gate control signal GS is switched from Hi to Low and the switching element is turned off. Comparing FIG. 5 and FIG. 6, it can be seen that the power loss increases when the speed of the switching element is low.

  The switching element has a limit on the upper limit temperature that can be used. In an in-vehicle power conversion device, for example, in a driving state where the voltage and current applied to the switching element are high, such as full-open acceleration, the loss inherent in the switching element is inherently large and is in a thermally severe state. If the switching speed is reduced in the state to increase the power loss, it may be assumed that the upper limit temperature of the switching element is reached.

  The objective of this invention is providing the power converter device which can reduce the noise given to a radio | wireless receiver, suppressing power loss.

The present invention is a power conversion device arranged in the vicinity of a wireless receiver, wherein a plurality of switching elements for performing power conversion, a driving means for driving the switching elements, and a reception state of the wireless receiver In response, the control means for controlling the switching frequency of the switching element by controlling the driving means, when the radio receiver is operating and the received radio wave intensity is smaller than a predetermined threshold intensity and weak The power loss at the time of switching is kept constant by controlling the switching frequency and switching speed of the switching element to be lower than in the other cases, and by making the degree of decrease when the switching frequency and the switching speed are reduced the same. And a control means for maintaining the above .

  ADVANTAGE OF THE INVENTION According to this invention, the noise given to a radio | wireless receiver can be reduced, suppressing a power loss.

  Hereinafter, an embodiment of the present invention will be described based on the drawings, taking as an example a power conversion device mounted on a vehicle having a radio receiver such as a radio.

  In FIG. 1, the block diagram of the power converter device in this embodiment is shown. The configuration is substantially the same as that of the power control unit PCU described in Japanese Patent Application Laid-Open No. 2005-168171.

  PCU 20 includes a smoothing capacitor 205, a boosting converter 210, and an inverter 220.

  Smoothing capacitor 205 is connected between power supply lines 201 and 202 from battery 10.

  Boost converter 210 includes a reactor 215, switching elements Q1, Q2, and antiparallel diodes D1, D2. Switching elements Q1 and Q2 are connected in series between power supply lines 203 and 202. Reactor 215 is connected between a connection node of switching elements Q 1 and Q 2 and power supply line 201. As the switching element in the present embodiment, an IGBT (Insulated Gate Bipolar Transistor) or a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor) can be applied.

  Inverter 220 includes an inverter unit 221 provided corresponding to motor MT, an inverter unit 222 provided corresponding to generator GT, and a smoothing capacitor 225.

  Smoothing capacitor 225 is connected between power supply lines 203 and 202 and smoothes the output voltage of boost converter 210, that is, the input voltage of inverter units 221 and 222.

  Inverter unit 221 has a general three-phase inverter configuration, switching elements Q3 and Q4 constituting a U-phase arm, switching elements Q5 and Q6 constituting a V-phase arm, and switching constituting a W-phase arm. Elements Q7 and Q8 are included. Corresponding to each of switching elements Q3 to Q8, antiparallel diodes D3 to D8 are respectively connected so that current flows from the emitter side to the collector side. Each phase arm of inverter unit 221 is connected to a corresponding phase of motor MT.

  The configuration of the inverter unit 222 is the same as that of the inverter unit 221. Each phase arm of inverter unit 222 is connected to a corresponding phase of generator GT.

  The controller 250 controls the converter control signal CVS and the inverter unit 221 for controlling the operation of the boost converter 210 according to the output values from various sensors so that the motor MT generates torque, the number of rotations, etc. according to the motor command value. An inverter control signal IVS1 for controlling the operation is generated. Specifically, converter control signal CVS is an on / off control signal for switching elements Q1 and Q2, and inverter control signal IVS1 is an on / off control signal for switching elements Q3 to Q8 in inverter unit 221. Switching elements Q1-Q8 are opened and closed by gate drive circuits GD1-GD8 in response to these on / off control signals. The output values from the various sensors include, for example, output values from the position sensor / speed sensor of the motor generator, output values from the current sensor 227, and output from the holding voltage detection sensor of the smoothing capacitor 225.

  The controller 250 further generates an inverter control signal IVS2 that controls the operation of the inverter unit 222 in accordance with outputs from various sensors so that the AC voltage generated by the generator GT is converted into a DC voltage. Specifically, inverter control signal IVS2 is an on / off control signal for switching elements Q3 to Q8 in inverter unit 222.

  Boost converter 210 receives the DC voltage supplied from battery 10 between power supply lines 201 and 202, boosts the input voltage by switching operation of switching elements Q1 and Q2, and supplies the boosted voltage to capacitor 225. The step-up ratio in converter 210 is determined according to the ON period ratio (duty ratio) of switching elements Q1 and Q2.

  The inverter unit 221 drives the motor MT by converting the DC voltage from the boost converter 210 smoothed by the capacitor 225 into an AC voltage by a switching operation in response to the inverter control signal IVS1.

  The inverter unit 222 converts the AC voltage generated by the generator GT into a DC voltage and supplies it to the capacitor 225. Capacitor 225 smoothes the DC voltage from inverter unit 222 and supplies it to boost converter 210. Boost converter 210 steps down the DC voltage from capacitor 225 and supplies it to power supply line 201.

  In such a configuration, the controller 250 monitors the reception state of the wireless receiver, sets the inverter control signal IVS1 (and ISV2) according to the reception state of the wireless receiver, and switches the gate drive circuits GD3 to GD8. The switching frequency of G3 to Q8 is changed. Noise generated from the inverter occurs at an integral multiple of the switching frequency, and the noise level decreases as the multiple increases. Therefore, by reducing the switching carrier frequency, the multiple of the radio frequency can be increased, and the noise level at the radio frequency can be reduced. FIG. 2 shows noise levels when the switching frequency is relatively high (a in the figure) and relatively low (b in the figure). The lower the switching frequency, the lower the noise level at the radio frequency.

  FIG. 3 shows a processing flowchart of the present embodiment. This is processing for controlling the switching frequency in the controller 250. First, it is assumed that a vehicle user activates a tuner (radio receiver) and selects a receiving station (S101). The controller 250 detects the received radio wave intensity Pin at the channel selection frequency (S102). The received radio wave strength may be measured by mounting the electric field strength system on the vehicle, or may be detected based on the map data of the received strength set in advance corresponding to each point in the navigation system. Then, it is determined whether the received radio wave intensity Pin is weak because it is smaller than a predetermined threshold intensity, or whether it is an acceptable level because the noise level in the passenger compartment is below the threshold level (S103). When the received radio wave intensity Pin is weak, it is necessary to suppress electromagnetic wave noise, so the switching frequency is lowered (S104). The switching frequency is also lowered when the noise level in the passenger compartment is acceptable (S104). Since the power loss is reduced by reducing the switching frequency, the fuel efficiency is also improved in the hybrid vehicle. On the other hand, although the noise at the radio frequency is reduced by lowering the switching frequency, the noise due to the electromagnetic noise of the motor etc. will increase, but if the noise is at an acceptable level, the electromagnetic noise of the motor etc. will be added somewhat. There is no problem. Further, if the radio receiver is in operation, there is no problem even if the electromagnetic noise of the motor or the like increases somewhat.

  On the other hand, when the received radio wave intensity is as strong as the threshold level or higher, it is not necessary to suppress electromagnetic wave noise, and the switching frequency is maintained as it is. Even when the noise level is unacceptable, the switching frequency is maintained as it is in order to prevent an increase in the electromagnetic noise of the motor due to a decrease in the switching frequency.

  In FIG. 3, the switching frequency is lowered not when the received radio wave intensity Pin is weak, but when the received radio wave intensity is within a predetermined range (except when the received radio wave intensity Pin is extremely weak or very strong). Processing may be executed.

  In FIG. 3, it is determined whether the received radio wave intensity is weak or the noise level is acceptable in S103. In S103, it is simply determined whether the received radio wave intensity is weak, and the received radio wave intensity is determined. If the received signal strength is low and the received signal strength is weak and the noise level is acceptable, the switching frequency reduction process is executed and the received signal strength is determined. It is also preferable not to execute the switching frequency reduction process when the noise level is not an acceptable level even if the noise level is weak.

  FIG. 4 shows a processing flowchart in another embodiment. This is processing for controlling the switching frequency in the controller 250. First, it is assumed that a vehicle user activates a tuner (radio receiver) and selects a receiving station (S201). The controller 250 detects the received radio wave intensity Pin at the channel selection frequency (S202). The received radio wave strength may be measured by mounting the electric field strength system on the vehicle, or may be detected based on the map data of the received strength set in advance corresponding to each point in the navigation system. Then, it is determined whether the received radio wave intensity Pin exceeds the upper limit value Pmax or lower than the lower limit value Pmin (S203). The upper limit value Pmax and the lower limit value Pmin may be fixed values or may be set according to the traveling state of the vehicle. More specifically, it is set according to the element current, the element voltage, and the element temperature that change according to the running state of the vehicle. As an example, the upper limit value Pmax is set larger and the lower limit value Pmin is set smaller than when not fully accelerating when the vehicle is fully opened, thereby expanding the range between Pmax and Pmin. Frequency and switching speed reduction control is easily performed).

  If the received radio wave intensity Pin exceeds the upper limit value Pmax or falls below the lower limit value Pmin, the switching frequency and the switching speed are maintained as they are because the improvement effect is small even if the electromagnetic wave noise is suppressed. When the received radio wave intensity Pin exceeds Pmax, the received radio wave intensity is sufficiently large, so there is little need to suppress electromagnetic wave noise. When the received radio wave intensity is less than Pmin, the received radio wave intensity is too weak. This is because even if it is suppressed, the original signal level is small, so it is not very effective. On the other hand, when the received radio wave intensity Pin is between the upper limit value Pmax and the lower limit value Pmin, since the improvement effect can be expected by suppressing electromagnetic wave noise, the switching frequency and the switching speed are lowered (S204). The relationship between the switching frequency and the switching speed is defined such that the switching frequency is changed by the same ratio as the switching speed is changed. Thereby, switching loss can be maintained substantially constant. For example, when the switching speed is reduced to 1/2, the switching frequency is also reduced to 1/2. Although electromagnetic noise can be suppressed by reducing the switching speed, as in the prior art, in this embodiment, power loss can be suppressed by reducing the switching frequency together with the switching speed. The switching frequency may be lowered by reducing the frequency of the carrier signal for generating the switching signal (inverter control signal). To reduce the switching speed, the switching elements Q3 to Q3 are described as described in the above publication. The gate resistance of Q8 may be switched. The changing speed of the gate potential depends on the gate resistance value, and the switching speed decreases as the gate resistance increases.

  In FIG. 4, the noise level may be detected in the same manner as in FIG. 3, and execution / non-execution of the process of reducing the switching frequency and the switching speed may be determined according to the level of the noise level.

  3 and 4, it is needless to say that both the switching frequency and the switching speed are maintained as they are because it is not necessary to suppress electromagnetic wave noise when the tuner is not activated.

  3 and 4, the execution / non-execution of the process of lowering the switching frequency is switched according to the received radio wave intensity Pin. However, even when the switching frequency is lowered, the elements of the switching elements Q3 to Q8 are further switched. The degree of switching frequency reduction may be adjusted according to the temperature. Specifically, when the element temperature is high, the degree of decrease in the switching frequency may be increased in order to suppress further temperature increase. This is because the switching loss decreases as the switching frequency decreases.

  As described above, in the present embodiment, by executing the process of lowering the switching frequency or both the switching frequency and the switching speed according to the operation / non-operation of the wireless receiver and the magnitude of the received radio wave intensity at the time of operation. In addition, electromagnetic wave noise can be effectively suppressed while suppressing power loss, and the wireless reception state can be improved.

It is a block diagram of embodiment. It is a graph which shows the frequency dependence of a noise level. It is a processing flowchart of an embodiment. It is a processing flowchart of other embodiments. It is power loss explanatory drawing when switching speed is fast (normal time). It is power loss explanatory drawing in case switching speed is slow.

Explanation of symbols

  10 battery, 210 boost converter, 221, 222 inverter unit, 250 controller.

Claims (1)

A power converter arranged in the vicinity of a wireless receiver,
A plurality of switching elements for performing power conversion;
Driving means for driving the switching element;
Control means for controlling the switching frequency of the switching element by controlling the driving means according to the reception state of the radio receiver, wherein the radio receiver is in operation and the received radio wave intensity is predetermined. If less weaker than listening strength, reduce controls the switching frequency and switching speed of the switching element than otherwise, and to the degree of decrease in the case of lowering the switching frequency and the switching speed with the same Control means for maintaining constant power loss during switching ,
The power converter characterized by having.

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