Yuichi Mabuchi

Development of a Low EMI Micro-controller Package for Automobile Applications

For ECUs the common-mode current is the main cause of EMI problems. In this paper, the mechanism of common-mode current generation and an effective way to reduce it is considered theoretically. From the consideration it is obtained that the common-mode current caused by the differential-mode current can be suppressed by means of adjusting the impedance of a PCB to be balancing adequately. And a package in which the impedance adjusting circuit and oscillator circuit is implement is developed for a micro-controller. The measurement shows that the developed package can reduce the common-mode current generation compared to the conventional QFP package. And the developed package can minimize the value of the common-mode current by means of adjusting the inductance of the power bus line in the package.

Low phase-to-phase-impedance busbar for modular power converter system

A small modular unit for a power converter system with long lifetime DC-link capacitors is proposed. To reduce the ripple current stress of DC-link capacitors and to improve their lifetime by limiting temperature rises, low phase-to-phase-impedance busbars are selected. Consequently, in a power converter system whose size is 101 L, operating at a rated power of 100 kVA, DC-link capacitors achieve a lower temperature rise of 22 K, which means that the capacitor lifetime can be estimated to be over 15 years.

Development of modular concept uninterruptible power system

Based on a modular design concept, 100 kVA uninterruptible power system using double-sided air-cooled power module has been developed. An efficient air-cooling system suitable for the double-sided cooled power module is developed, and the volume of the converter adopted developed double-sided air-cooling system becomes less than half compared to the conventional converter based on single-sided cooling system. The width of the modular unit composing the rectifier, inverter, and chopper is only 50 mm so as to stack some units side by side in a smaller space and higher maintainability is achieved. The volume as well as the footprint of the developed UPS is smaller than the conventional one by 30 %.

Novel design technique for reducing common-mode current on wire harness connected to ECUs

A key parameter that controls common-mode cur- rent on the cable connected to electronic control units (ECUs) is investigated. Supply currents for the CPU on ECUs and parasitic inductance / capacitance of supply traces on printed circuit boards (PCBs) generate common-mode current on the cable. We found the amount of common-mode current can be reduced sensitively by adjusting the balance of parasitic inductance / capacitance. The new approach proposed in this paper allows minimizing the common-mode current and suppress the radiation less than the currently achievable level. This technique is proven experimentally with evaluation boards and the influence of these parameters on common-mode current is confirmed by our simulation technique. I. INTRODUCTION Nowadays, a driving speed of LSI is getting faster and it is equipped on electronic device denser than past one. According to these situations, electromagnetic radiation from electronic devices becomes larger and it gives harmful influence on electronic devices such as jamming of radio communication or miss action of its circuits. Especially in automobile, EMI/EMC becomes very serious problem because many electronic de- vices are equipped together with a radio in a car. The origin of electromagnetic radiation emitted from electronic device is voltage fluctuation and high frequency current that are exited when LIS is driving. These voltage fluctuation and high fre- quency current drive printed circuit boards (PCBs), their frame and cable attached to them as antennas and electromagnetic wave is radiated from them. At VHF (30∼300MHz) frequency

A very thin power conversion unit for equalizing currents through paralleled power modules

Among high power conversion systems, several power modules are often connected in parallel, and ideally should be operated synchronously during their switching. Actually, current imbalances occur due to an asymmetry of current paths on busbars connecting these power modules. This paper deals with the problem of current imbalances between paralleled power modules. First, the general occurrence of imbalanced currents is demonstrated. Next, an original design technique for current equalization in a very thin power conversion unit is presented. Finally, the validity of this proposed principle is shown in simulated results.

Simultaneous switching noise analysis on bus lines using coupled circuit and electromagnetic simulation

Simultaneous switching noise (SSN) on bus lines is calculated by accurately modeling printed circuit boards and LSI packages using coupled circuit and electromagnetic simulation. Contribution of crosstalk and ground bounce to SSN is qualitatively estimated. With relatively low inductance package such as BGA, the main cause of SSN is cross talk which results in increasing SSN voltage along the length of bus line. The results of simulation are compared with those of experiment, the both results agree within 10% difference at maximum peak of SSN.

Compact gate drive printed circuit board for uninterruptible power system

A gate drive printed circuit board (PCB) was developed for a 50-mm-wide modular-design thin power unit that uses two double-sided cooled power modules in an uninterruptible power system (UPS). A conventional gate drive PCB has a concentrated gate power supply circuit that uses a large transformer and has a conventional pulse open-phase detection circuit that occupies a large mounting area. Thus, the gate drive PCB had to be downsized to make it as narrow as the thin power unit. Consequently, two circuit configurations were proposed to reduce mounting area: one was to decentralizes a gate power supply circuit using a pre-driver with a built-in DC/DC controller and a small distributed transformer, and the other was to downsize the pulse open-phase detection circuit. As a result, the gate drive PCB was downsized to 50 mm × 220 mm, 56 % smaller than the conventional one. Thus, a very thin power unit using a 50-mm-wide PCB was accomplished, and a UPS was developed that is 30 % smaller in volume than the conventional one.

Reduction method of common-mode noise on power supply cable using floating conductor

A method to reduce common-mode current flowing on a wire harness attached to a printed circuit board is proposed in this paper. In this method, SMD inductors are placed on a power supply line and/or a ground line on a LSI package with floating conductor to control balance of impedance of the power distribution network, and the common-mode current can be reduced. The common-mode voltage is reduced about 20 dB with the package proposed in this paper.

Common-mode noise reduction using floating conductor in LSI package

The authors proposed a method to reduce the common-mode current flowing on a wire harness attached to a printed circuit board (PCB). In this method, SMD inductors are placed on a power supply line and/or a ground line on a PCB to control balance of impedance of the power distribution network, and the common-mode current can be reduced. In this paper, the authors apply this reduction method to an LSI package, and propose a new structure of the LSI package with floating conductor which is called cover metal. The common-mode voltage is reduced about 20 dB with the package proposed in this paper.

Common Mode Voltage Evaluation for choosing Quiet MCU and Optimizing PCB Design: Electromagnetic Emissions Measurement for Integrated Circuits

Similar to the fact that the differential signaling interfaces radiate less amount than the typical single ended interfaces, radiation from wire harness connected to electronic control units using single chip micro computers can be reduced by adjusting the common mode voltage fluctuation of supply lines. The radiation from wire harness can be minimized when the Vcc and the Vss fluctuate with same magnitude in opposite phase. As estimating these fluctuations of real products using lots of components on complex PCB layout by simulation technique is quite difficult at this moment, alternative solution to investigate the common mode voltage fluctuation has been investigated. By the Workbench Faraday cage method and advanced usage of it with 180 deg four ports hybrid balun, common mode voltage fluctuations of Vcc and Vss with phase information can be monitored. Examples of this measured data are discussed and a way of reducing common mode radiation from wire harness is explained.