Inside the Honda CR-V's e:HEV Power Control Unit: A Teardown and Comparison with the Fit
イチケン / ICHIKEN
This teardown opens the power control unit (PCU) from a North American sixth-generation Honda CR-V. The presenter notes that the CR-V is expected to go on sale in Japan from February 2026, and that unless the powertrain specifications have changed significantly, the Japanese model will likely use this same PCU. The unit belongs to a newer generation than the Fit PCU the channel took apart previously. The aim is to see what technology it uses and what changed between the two generations. The presenter's overall view is that the new unit is optimized throughout. They also suspect that this style of power-module-based design is close to its limit.
A Quick Recap of Hybrid Architectures
Before disassembly, the presenter briefly reviews the major Japanese hybrid systems, which an earlier video covered in more detail.
- Toyota's THS II is a series-parallel hybrid. A power-split mechanism distributes power among the engine, generator, and motor to drive the wheels.
- Nissan's e-POWER is a series hybrid. The engine only turns a generator, and the resulting electricity drives the motor that turns the wheels. The presenter calls it the most EV-like of the three.
- Honda's e:HEV is also classed as series-parallel, but in practice it behaves much like a series system. Its distinctive feature is a mode that connects the engine directly to the drive wheels at higher speeds. For that reason, the presenter suggests it could be described as a "series-parallel switching" system.
Exterior, Terminals, and Size
The PCU is made by Keihin. The presenter describes it as ordinary-looking. According to the presenter, the North American CR-V's motor output is 133 kW and its generator output about 120 kW, so the unit is sized to convert that much power.
On the outside there are:
- the input terminal for the drive battery (262.8 V on the hybrid, 347.5 V on the plug-in hybrid);
- a 12 V output terminal for the car's electrical equipment, fed by an internal step-down circuit from roughly 260 V;
- coolant inlet and outlet ports;
- on the bottom, two sets of three-phase terminals for the drive motor and the generator;
- also on the bottom, a signal connector for controlling the PCU.
Next to the older Fit unit, the CR-V's PCU is wider but noticeably thinner. The presenter attributes this mainly to connector placement. The Fit has connectors rising from its top, which forces extra height. The CR-V routes its connectors out of the bottom, where the motor terminals already are. Grouping connections on the underside also frees the space above the PCU. In both the North American and Japanese CR-V, the presenter says, the air intake passes through that space. That layout is only possible because nothing sticks out of the top.
The Three-Layer Internal Structure
With the top panel removed, a two-story stack of printed circuit boards appears first. Under it are the power module and, beside it, a film capacitor. The presenter notes that the power modules are much smaller than in the previous generation. Removing the capacitor and module exposes a coolant channel.
From the underside, a laminated bus bar carries current in from the battery terminals. It distributes power to the film capacitor, the power module, an inductor, and the DC/DC converter. The inductor belongs to the bidirectional boost converter that raises the battery voltage. It has two windings per input, which leads the presenter to think the boost converter may use interleaved control. The DC/DC converter produces 12 V for vehicle electronics. The presenter remembers the previous generation's converter as rather messy and describes this one as neat. The inductor and the DC/DC section each have their own coolant path underneath.
In summary, the unit has three layers:
- Top: film capacitor, power module, and above them the gate drive and control boards.
- Middle: an aluminum block that carries the coolant.
- Bottom: the DC/DC converter and the inductor.
How the Sixth-Generation CR-V's e:HEV Works
While preparing the video, the presenter researched the CR-V's e:HEV layout. The electrical side has changed little from earlier systems: a battery, a DC/DC converter, a bidirectional converter, and three-phase inverters driving each motor-generator.
The big difference is mechanical. Earlier e:HEV systems had a single engine direct-drive ratio, so direct drive was limited to high speeds. The North American CR-V has two direct-drive ratios, high and low, and opening or closing clutches selects between them. At lower speeds, one clutch engages the direct connection; at higher speeds, the other does. The presenter says this lets the CR-V use engine direct drive over a wider speed range for better fuel economy.
The motor and generator still work during direct drive. In the presenter's understanding, the system runs coordinated control to keep the engine at its most efficient operating point. If the engine load is too heavy, the motor runs in power mode to assist. If the load is too light, the motor regenerates, recovering energy from the engine and the moving vehicle into the battery while giving the engine an appropriate load. The presenter tried to find out whether this load adjustment happens on the motor side or the generator side and could not. Their guess is the motor side, on the assumption that Honda would pick the most efficient approach.
The Control Board and Its Floating Connector
The control section consists of two boards. The upper board is the control board. The lower one is the gate drive board, which drives the power semiconductors and also carries sensors. A board-to-board connector joins them, and the presenter finds it unusual because it visibly moves. The fixed half sits on the control board. The movable half, on the gate drive side, shifts noticeably.
The connector turned out to be IRISO Electronics' Z-Move type, the video's sponsor. It moves in X and Y, which the presenter reads as a way to absorb misalignment during mating and to reduce prying stress on solder joints and contact points. It also moves in Z. The presenter believes the Z movement is less about assembly tolerance and more about coping with board vibration and resonance.
The presenter reasons as follows. If vibration from the body moved the whole board uniformly, a firmly fixed board would see little effect. But under some conditions the contacts inside a connector can keep sliding against each other, wear, and cause signal faults. Mechanical resonance can also make only part of a board vibrate strongly. The presenter compares this to the patterns of Chladni figures on a vibrating plate. A sudden resonance mode like that can wear sliding contacts quickly. Because the Z-Move body itself moves while the contacts stay fixed relative to each other, the presenter believes it preserves long-term reliability.
Microcontroller, Gate Drivers, and Current Sensing
The microcontroller is a Renesas R7F701275. The presenter describes it as a dual-core high-end automotive MCU with a built-in resolver-to-digital conversion circuit for detecting motor rotation angle.
The gate drive board carries fairly large transformers for the gate drive power supplies, and insulation distances are generous. The presenter explains why so many transformers are needed. Each upper-arm power semiconductor has an emitter reference that swings with the switching state, so each one needs its own isolated supply. The lower-arm devices share a common emitter reference, so in an inverter, one isolated supply can serve all three lower-arm IGBTs. That shared transformer is physically larger because it powers three devices.
The gate driver ICs on the reverse side are ROHM BM60059. The presenter says ROHM gate drivers show up often. According to the data sheet, this part isolates by magnetic coupling. It also includes circuitry to drive a transformer, so with external FETs it can generate its own gate drive supply. The presenter calls it a convenient IC.
The remaining ICs are Hall sensors. They slot into the power module and sit right next to its bus bars. Each one reads the magnetic flux from the current in a bus bar and converts it to a current value. Inside the power module, where it is hard to see from outside, a steel core surrounds the bus bar.
Comparison with the Fit's Control Board
Against the previous generation's Fit board, the presenter's overall impression is that the design has been considerably optimized:
- The Fit used a single board with two Renesas motor-control microcontrollers.
- The CR-V splits the electronics into a low-voltage control board and a high-voltage gate drive board. The presenter says this means isolation distances no longer need as much attention as on the Fit, and the layout is cleaner.
- The number of microcontrollers is halved from two to one, and the package changed from QFP to BGA.
- As a result of these changes, printed circuit board area is reduced by about 20%.
External communication connectors also changed. The Fit mounted them directly on the board. The CR-V uses small connectors at the side of the board and runs cables through the PCU to a connector at the bottom. The presenter suggests this may be what allowed the PCU's height to drop.
Power Module and Film Capacitor
In the CR-V, the power module sits right next to the film capacitor. Bus bars rise from the capacitor and reach the module over the shortest possible distance. The presenter expects this keeps loop inductance quite small.
Inside, the power semiconductors are arranged in 2-in-1 configurations, each in its own compartment. The two center compartments serve the bidirectional converter. The three on each side serve the two inverters. The semiconductors are soldered to the bus bars.
Chip sizes differ by application. The chips in one inverter are nearly 1.8 times larger than those in the other. The unit was not taken from a vehicle by the presenter, so they cannot confirm which inverter drives the motor and which serves the generator. Their guess is that the motor, with its higher power and torque, needs larger chips to handle more current.
On the back, the cooling fins are densely pitched and unevenly distributed, with some larger fins in places. The presenter does not know the reason for the arrangement. Their interpretation is that fins sit directly under the chips as a baseline, and larger fins are added in otherwise unused areas to shed more heat into the coolant.
What Changed from the Previous Power Module
Laying the new module beside the earlier Fit module, the presenter highlights several differences.
Arrangement. The new design places the power module and film capacitor side by side. The old one stacked the module on top of the capacitor. The presenter says this change contributes to the thinner product.
Chip count and size. The new module is significantly smaller overall. The old module had one semiconductor chip per compartment; the new one has two.
Bus bar routing. In the old design, bus bars ran from the capacitor to both ends of the module and then continued through it to reach the chips, a long path that raises loop inductance. The presenter cites the rule of thumb that 1 cm of wiring has roughly 10 nH of self-inductance, so longer is worse. The new design still runs bus bars through the module, but the distance is far shorter. On this point, the presenter considers the new module much better.
Cooling. The old power module came with its own water jacket. The new one covers an aluminum block that has the cooling channels machined into it. The presenter sets aside the question of which is better thermally, but notes the new approach uses fewer parts and should be cheaper.
Motor connections. Previously, crimped copper-wire terminals were screwed to connectors coming from the motor. The new design uses pressure contacts: on disassembly, the presenter finds springs that press the motor-side conductors into place. Because this part must move, braided wire is used there instead of solid bus bar throughout. The presenter wonders whether it is ultrasonically bonded.
The Boost Inductor
From the underside, the laminated bus bar from the battery feeds both the DC/DC converter and the inductor. The inductor has two windings on one core. Both share a common battery-side terminal and split to two terminals on the power semiconductor side. Flat wire is wound densely to reduce volume. The two windings are wound so that their magnetic fluxes cancel. Given this construction and the connections to the power semiconductors, the presenter thinks the boost converter is likely interleaved under some driving conditions. The cooling side underneath uses cylindrical pin fins.
The CR-V's inductor is about twice the size of the Fit's. The presenter sees this as a clear reflection of the difference in PCU capacity between a compact car and an SUV.
As an aside, the presenter recalls the Fit's arrangement as odd. There, the DC/DC converter and inductor were built as one unit, with the inductor separately removable, and four rubber gaskets were used. The presenter felt it did not look efficient to assemble. In the CR-V, the DC/DC converter and inductor are separate components that can each be installed independently, and the gasket count drops to one each, two in total.
The 12 V DC/DC Converter
The DC/DC converter steps the drive battery's high voltage down to 12 V for other in-vehicle equipment. Most components sit on a removable printed circuit board. That board has many tall through-hole parts and is filled with silicone. The presenter believes the silicone guards against parts detaching under vibration and against solder cracks. Compared with the fifth-generation Toyota Prius's DC/DC converter, the CR-V's uses many more through-hole parts, especially film capacitors, and the circuit volume is correspondingly larger. The presenter notes that the Prius replaced most of those with MLCCs.
Below the board are the large magnetic and semiconductor components, which the presenter traces from input to output:
- Relay-like board: removed first, revealing the power semiconductors.
- Primary switching: a Shindengen MG051D, which the presenter believes is a MOSFET module. The converter topology itself has not changed much. However, the previous generation used discrete power semiconductors here, and moving to a module greatly reduces mounting area. The module's back is coated with thermal grease and dissipates heat into the aluminum.
- Transformer: the primary winding is flat wire and the secondary is a bus bar. Thermal conductive sheets sit between the windings, the ferrite core, and the housing to carry heat away.
- Rectification and filtering: an output choke coil connects to a rectifier module. Together with an array of film capacitors, the choke forms the output filter. The rectifier is a Shindengen diode module with two sets of three diodes in parallel, probably Schottky barrier diodes, and a snubber circuit in the same package. The previous generation used Sanken Electric Schottky diodes on an aluminum substrate. The presenter says modularization improves many things here.
Shindengen modules appear throughout the main power semiconductors. The presenter adds that Shindengen sells DC/DC converter modules under a TW series name, and this board is marked "TW109." Shindengen's largest shareholder is Honda. The presenter stresses this is only speculation, but thinks Shindengen may have designed this DC/DC converter. The cooling fins behind it are grooved more deeply only under the power semiconductors, apparently to draw out more heat there, though the presenter says the design rationale is not clear.
Where the Design Can Go Next
The presenter's verdict is that, compared with the previous-generation Fit, the CR-V's PCU is optimized throughout and contributes to smaller size and higher power density. Going further, they argue, would mean questioning the power module format itself. One option is to keep this kind of module. Another is to stack double-side-cooled power cards, as Toyota does. For a design built around a conventional power module like this one, the presenter felt while taking it apart that it has nearly reached its end point, and that making it significantly better from here would be quite difficult.
This video is brought to you courtesy of IRISO Electronics. Hello. Today, we're disassembling a Honda CR-V power control unit, or PCU. This PCU was removed from a North American version of a sixth-generation CR-V. There is information that the CR-V will finally go on sale in Japan in February 2026. Unless the powertrain specifications have changed significantly, the Japanese version is likely to have the same PCU as this one.
This is a newer generation of PCU than the one from the Fit we previously disassembled. Today, we'll take this apart and take a closer look at what technology is used and what has changed from the previous generation. But first, here is today's sponsor.
I wonder if you are familiar with IRISO Electronics. It's a company that makes connectors and is particularly strong in automotive connectors. In fact, IRISO Electronics connectors are used in an important part of the inverter we're taking apart today.
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Secondly, in terms of reliability, IRISO Electronics' proprietary Z-Move technology can absorb vibration and resonance specific to automotive use, increasing the long-term reliability of contacts. To ensure contact, connectors with a two-point contact structure can remove foreign objects and prevent contact defects.
In addition, future applications such as automated driving require high-speed signal transmission, so preparations are steadily underway for connectors supporting 25 Gbps and so on. If you are a designer who uses automotive connectors, consider IRISO Electronics connectors with these strengths.
Before we start disassembling, we'll take a brief look at the hybrid systems offered by automotive companies. We covered these in detail in a previous video, so please refer to that. There is a link in the description.
First, Toyota uses THS II, Toyota Hybrid System II. This is a series-parallel hybrid system. Through the power-split mechanism shown here, it appropriately distributes power from the engine, generator, and motor to turn the drive wheels.
Next is Nissan's e-POWER. This is a series hybrid. The engine turns a generator to generate electricity, and that power is used to turn the motor and drive the wheels. Basically, only the motor turns the drive wheels. Of these systems, this is the most like an electric car.
And here is Honda's e:HEV. Like Toyota's, this is a series-parallel hybrid, but its operation is similar to a series system. e:HEV has an interesting mode: at high speeds, it connects the engine directly to the drive wheels to turn them. In practice, you might call it a series-parallel switching system.
Now, let's look at the actual power control unit. Here is the PCU removed from the North American CR-V. It looks like an ordinary inverter. It's made by Keihin. The North American CR-V's electric motor output is 133 kW, and the generator output is approximately 120 kW, so it is sized to convert that much power.
First, let's look at the external terminals. Here is the input terminal for the drive battery. Battery voltage is 262.8 V for hybrids and 347.5 V for plug-in hybrids. Next is the 12 V output terminal for the vehicle's electrical equipment. This PCU contains a circuit to step down the drive battery's 260 V to 12 V. I'll disassemble this later to check. Right next to it is the coolant inlet and outlet.
Let's look at the bottom as well. Here are two sets of terminals connected to the three-phase motors for propulsion and power generation. If you look closely at the bottom here, there is also a connector. This exchanges signals to control the power control unit itself.
Let's compare its size with the Fit inverter we previously disassembled. The Fit inverter is an older generation. As you can see, the CR-V unit is wider, but it is thinner in the height direction. The Fit unit is taller. In particular, the Fit has connectors protruding from the top, which inevitably adds height. The CR-V's thinner shape may be due to its structure, with connectors coming out underneath.
Both units have terminals on the bottom to connect to the motors. Grouping the connectors on the bottom is a smarter arrangement and allows the space above the PCU to be used effectively. In fact, in the North American version and the CR-V to be sold in Japan, the intake passes through the space above the PCU. This arrangement is possible because no connectors protrude from the top.
From here, we'll check the internal structure. First, let's remove the top panel. You can see the printed circuit boards, arranged in two levels. When these boards are removed, there is a power module like this, with a film capacitor beside it. This power module is much smaller than the generation we previously disassembled. Remove the film capacitor and then the power module, and there is a coolant passage like this. We'll look at this in more detail later.
Next, we'll access it from the bottom. When the lid is removed, it looks like this. What you might call a laminated busbar comes in from the drive battery terminals. That laminated busbar leads to each component of the circuit. Of course, it also connects to the film capacitor and power module we just saw.
The inductor and DC/DC converter circuits are also visible here. This inductor is part of the boost converter that boosts battery voltage—in this case, a bidirectional converter circuit. Looking here, there are two windings for one input, so the boost converter may use interleaved control.
The DC/DC converter is a circuit that converts battery voltage to a 12 V output for the vehicle's electrical components. I had the impression that the previous generation's DC/DC converter was pretty messy. This one looks rather neat. I'll disassemble it later to check.
If we look underneath the inductor, there is a coolant passage like this. Looking farther down on the DC/DC side, there is another passage for water to flow through.
The PCU used in the CR-V that we've just looked at roughly has this structure. It has three layers. There is a film capacitor and a power module, with the gate drive circuit and control board on top of the power module. In the middle is an aluminum block through which coolant passes. Below that are the DC/DC converter and inductor.
While making this video, I looked into the e:HEV system used in the sixth-generation CR-V. It uses this configuration. The left side is mainly the electrical system, and the right side is mainly the mechanical system. The electrical system hasn't changed much from before. There is a battery, a DC/DC converter, a bidirectional converter, and three-phase inverters to turn each motor-generator.
Up to now, there has been a direct engine connection, but the North American CR-V can switch between two gear ratios for that direct connection. That's the big difference.
As you know, e:HEV basically uses battery power to turn the motor and drive the vehicle. When battery power isn't enough, the engine runs a generator, and the electricity it generates is used to turn the motor.
One of e:HEV's main features is a fuel-efficient driving mode that connects the engine directly to the drive wheels at high speeds. Until now, direct engine mode was limited to high speeds. In the CR-V, the direct connection can switch between high and low gears. This part is directly connected to the engine, and this part switches between high and low gears. Opening and closing these clutches allows two gear ratios to be selected.
For example, to connect the engine directly at low speeds, close the clutch in this part. For a direct engine connection at high speeds, you can choose to close the clutch here. This allows the CR-V to connect the engine directly over a wide speed range for fuel-efficient operation.
When the engine is directly connected, that doesn't mean the motor and generator do nothing. They are actively controlled. This coordinated control runs the engine at its most efficient operating point. For example, if the engine load is too heavy, the motor operates in motoring mode to assist the engine. Conversely, if the engine load is too light, the motor operates regeneratively, recovering energy from the engine and the moving vehicle's kinetic energy into the battery while placing an appropriate load on the engine.
I looked into whether this operation is performed on the motor side or the generator side, but I couldn't figure it out. I think it would be done in whichever way is most efficient. Maybe it's done on the motor side.
From here, we'll take a closer look at each component, starting with the control boards on top of the power module. Here they are. There are two boards. The upper board is the control board. The lower board is the gate drive board for driving the power semiconductors, and it also carries sensors.
The upper and lower boards are connected by connectors in this section. This connector is pretty interesting. It moves like this. Can you see? Connectors that move this much are rare. Let's take a closer look at the connector by removing the board.
The connector on the control board side doesn't move. It's the one on the gate drive board that moves like this. That's quite a lot of movement, isn't it? When I looked into it, I found that this connector is an IRISO Electronics product. It seems to use their proprietary technology called Z-Move.
If you move this connector, it moves in the X direction and the Y direction. I think this is to absorb mating misalignment when connecting the connector. When connecting the boards, it also reduces prying forces and stress on solder joints and terminal contact areas.
In addition to the X and Y directions, it can also move in the Z direction. I assume this is intended more to reduce the effects of board vibration and resonance than to absorb mating misalignment.
Vibration transmitted from the vehicle body can make the entire board move like this. The board itself is firmly secured, so the effect of vibration is small. Depending on the vibration conditions, however, the contacts in the connector can slide. If they keep sliding, they wear out, and signal transmission can go wrong. In this Z-Move connector, the connector itself moves like this while the contacts remain fixed, which seems to preserve long-term reliability.
Then there is mechanical resonance. This is a phenomenon where only part of the board vibrates. It's easy to understand if you picture Chladni patterns from plate vibration. This provides a way to avoid situations where a resonance mode suddenly appears, making the contacts slide and wear out quickly.
We'll also look at the other components on the board. The microcontroller is Renesas' R7F701275. This is a dual-core, high-end automotive microcontroller with built-in conversion circuitry for resolvers that detect the motor's rotation angle.
And this is the gate drive board. It's all on one board. Looking at it, fairly large components are lined up. These are transformers that supply power to the gate drive circuits. Adequate isolation distances are also maintained.
When driving power semiconductors, the emitter reference voltage of the upper-arm devices varies with the switching state, so each requires a separate isolated power supply. Therefore, a transformer is needed for each power semiconductor. For the lower arm, the emitter reference voltage is common. For example, an inverter only needs one isolated power supply for the three lower-arm IGBTs. However, because it supplies three IGBTs, the transformer itself is larger.
Let's look at the reverse side. The gate drive ICs are ROHM BM60059 devices. ROHM gate driver ICs are used quite often. According to the datasheet, isolation is provided by magnetic coupling. This IC actually includes circuitry to drive a transformer. External FETs are required, but it's a convenient IC that can also create a power supply for the gate drive.
The remaining components include Hall sensor ICs. These fit into the power module. The Hall sensors are positioned right next to the power module's busbars. They read the magnetic flux created by current flowing through the busbars and convert it to a current value. It's difficult to see from the outside, but a steel core surrounding the busbar is inside the power module.
Let's compare this with the control board from the Fit, which is the previous generation, so to speak. The overall impression is that the system has been optimized considerably. The Fit used a single board with two Renesas microcontrollers for motor control. The newer CR-V uses two boards: a low-voltage control board and a high-voltage gate drive board.
Separating the low-voltage and high-voltage circuits between boards means there is less need to worry about isolation distances than with the Fit. The CR-V has a cleaner overall layout. The number of microcontrollers has also been halved from two to one, and the package has changed from QFP to BGA. These optimizations allow the printed circuit board area to be reduced by about 20%.
Then there is the external communication connector. In the previous generation, it was mounted directly on the board. In the new generation, a small connector comes out of the side of the board, and a cable runs through the PCU to a connector on the bottom. Perhaps this allows the PCU's height to be reduced by the height of that connector.
Next, we'll look at the power module and the film capacitor beside it. The power module is installed quite close to the film capacitor. Busbars extend from the film capacitor and connect to the power module over the shortest distance. The distance from the film capacitor's busbars to the power semiconductors is short, so I imagine the loop inductance is also quite small.
The power semiconductors are arranged in a 2-in-1 configuration in separate compartments. The two in the center are used in the bidirectional converter, and the three on each side are used in the inverters. The connections between the power semiconductors and the busbars are soldered.
If you look closely, the power semiconductor chips differ in size depending on where they are used. Let's look at the inverter chip sizes, for example. Here is the chip size in one inverter, and the chips in the other inverter are nearly 1.8 times larger. Which inverter is on the motor side, and which is on the generator side?
It was not removed from the vehicle. I don't know. The motor has more power and torque. The current is so large that it may be using a larger chip to handle high currents.
Looking at the back of the power module, the cooling fins stand like this. The fin pitch is quite dense. The cooling fins are not evenly distributed. There are also large cooling fins in some places. I don't know the reason for this arrangement, but basically, the cooling fins are right under the chip. Therefore, maybe the slightly larger cooling fins are there to effectively utilize this large space as well. I think it's designed to spread the cooling fins over a large space here as well, releasing more heat into the coolant.
From here, let's compare the power modules and film capacitors with those of the previous generation. Below is what we disassembled this time. The one above was previously disassembled. Let's start with the overall arrangement. In the new one, the power module and film capacitor are side by side, whereas the previous generation had the power module on top and the film capacitor underneath it. This difference in structure contributes to a thinner product.
The power module has been significantly downsized this time. In the previous one, there was one power semiconductor chip in each compartment. In the newer one, there are two chips in each compartment. The placement of the copper bus bars connecting the film capacitor to the semiconductor chips has also changed significantly.
In the previous generation, the bus bar extends from the film capacitor and connects at both ends of this. From there, a bus bar runs further into the power module and connects to the power semiconductor chips. This is a long distance, so there will be more loop inductance. The self-inductance of 1 cm of wiring is said to be 10 nH. After all, the longer it is, the worse it is. In the newer one, the bus bar extends from the film capacitor and runs through the module, but compared to the old one, that distance is much shorter. In this respect, the new power module is much better.
We will also look at the cooling section. In the previous generation, the power module came with a water jacket. In the new generation, the power module is designed to cover an aluminum block with cooling channels. Let's leave aside which is better. The newer generation uses fewer parts, so the cost is likely to be lower.
The terminals connecting the power module to the motor have also changed. Previously, the terminals were crimped onto copper wire, and the connector coming from the motor was screwed onto them. In the new generation, the connection to the motor is made by pressure rather than screwing in terminals. I took it apart, and it has a spring in it like this. The structure is designed to be pressed. The motor-side wire makes contact somewhere in this area. This part is movable, so everything isn't made with bus bars. Braided wires are used to allow some movement. Is ultrasonic bonding used for this part?
Next is the part accessed from the underside of the PCU. Let's start with the inductors. In terms of electricity flow, this laminated bus bar comes in from the battery. That bus bar is designed to connect to the DC/DC converter here and to an inductor.
Take a closer look at this inductor. Two windings are wound on one core. This is winding 1, and this is winding 2. This terminal is the one coming in from the battery, and there are two terminals at the output. These connect to the power semiconductor side. The windings share a common connection on the battery side and are separate on the power semiconductor side. The windings are densely wound to reduce volume, using flat wire. Looking at windings 1 and 2, they are wound in a direction that cancels each other's magnetic flux. I talked a little about this earlier. Judging by the configuration of this inductor and its connections to the power semiconductors, the boost converter likely uses interleaved control under some driving conditions.
Looking at the back side, this is the channel through which the cooling water passes. As you can see, the cooling fins have a cylindrical shape. Comparing the size of the inductors in the Fit and CR-V, the CR-V's is about twice as big. Naturally, the power capacity of the CR-V's PCU is higher, and the inductors themselves appear to be larger. This is where the difference in PCU capacity between compact cars and SUVs comes out clearly.
I digress for a moment. The way the DC/DC converter and inductors are installed in the Fit is pretty weird. The DC/DC converter and inductors are somehow all in one piece, and this inductor can also be removed separately. From what I can see, it uses four rubber gaskets. When I took it apart, I thought it was a very strange arrangement. The efficiency of installing and assembling the parts doesn't look too good, does it? With the CR-V, that's much better. The DC/DC converter and inductors are separate, so you can work on each as a separate component. Naturally, the number of rubber gaskets was reduced to one for each, for a total of two.
Next, we will look at the DC/DC converter. This is a conversion circuit that converts the drive battery's high voltage to 12 V for other in-vehicle equipment. This board can be removed. Most of the components are on this printed circuit board. If you look at it, you'll see that it uses a lot of tall through-hole components. It's filled with silicone, which I think prevents parts from falling off due to vibration and prevents solder cracks.
Compared to the DC/DC converter in the fifth-generation Toyota Prius, there are quite a lot of through-hole components. In particular, it uses a lot of film capacitors, which increases the volume of the circuit. In the fifth-generation Prius's DC/DC converter, most of those have actually been replaced with MLCCs.
We will look beneath the board here. There are large components here that cannot be mounted on the printed circuit board. These are basically magnetic components and semiconductor components. We will look at them by following the circuit from the input side to the output side.
First, here is a printed circuit board that acts like an interconnection board. Remove it, and you can see the power semiconductors underneath. This is a Shindengen MG051D. Is this a MOSFET module? In fact, the DC/DC converter's configuration hasn't changed much. In the previous generation, this part used discrete power semiconductors. Here, using a power module greatly reduces the mounting area. The back side is coated with thermal grease, and the heat is dissipated into the aluminum.
Then it connects to the transformer here. The primary winding is flat wire, and the secondary winding is a bus bar. A thermally conductive sheet is sandwiched in to dissipate heat from the windings and ferrite core. Then it connects to the output choke coil and the power module for rectification. This choke coil and the film capacitor array combine to form a filter circuit.
The power module shown here is a Shindengen diode module. It contains two sets of three diodes in parallel. They're probably Schottky barrier diodes. The package also includes a snubber circuit. The previous generation used Sanken Electric Schottky barrier diodes mounted on an aluminum substrate. Modularizing this improves many things. As we have seen so far, many Shindengen power modules are used for the main power semiconductors.
I digress here. Shindengen has a line of DC/DC converter modules called the TW series. This board also says TW109. Also, Shindengen's largest shareholder is Honda. What I am about to say is only speculation, but it is possible that Shindengen designed this DC/DC converter.
Regarding the cooling fins on the back side here, it isn't clear how they were designed. The grooves are deeper only in the part with power semiconductors, designed to allow more heat to escape.
Today, we disassembled the power control unit installed in the North American version of the sixth-generation CR-V. Compared to previous-generation Fits and similar vehicles, the whole interior is optimized. I think this contributes to miniaturization and high power density.
If you want to make it even better than this, we need to think about whether to use this type of power module in the first place. Is it correct to use this form of power module? Or is it right to stack power cards that can be cooled on both sides, like Toyota? However, for a design that uses a power module like this one, it's pretty close to where it's going to end up. As I took it apart, I thought that improving it further from here might be quite difficult.
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