Development of a New CMOS Isolator Technology paving the way for Higher Speed and Integration Densities in Inverter Circuits
One of the key components in making energy-efficient products such as air conditioners, refrigerators, electric vehicles as well as hybrid electric vehicles is inverter circuits by providing fine-tuned control of motor speed. The inverter circuits is basically consists of a high-voltage circuit responsible for controlling the On/Off state of the voltage that is applied to the motor, where the control voltage ranges somewhere form a few hundred to a few thousand volts, an a microcontroller (MCU) which operates at a few volts. Now, in order to transfer data from high-voltage circuit to MCU and isolator is traditionally used to overcome this large voltage difference between MCU and high-voltage circuit, however, owing to this large size, up to now it has been difficult to integrate MCU with multiple high-voltage circuits and isolator all in a single package. One of the contributing factors in isolator’s large size is it on-chip transformer, and reducing the size of the isolator pretty much translates to reducing the size of the on-board transformer, however by reducing the transformer size, its operation frequency would exceeds the limit of the frequency that can be received through digital circuits. In order to succeed in miniaturization of the isolator, Renesas Electronics has successfully developed a new CMOS isolator technology, capable of transferring high-frequency signals through use of high frequency components generated from a low frequency digital input signals with sharp rise.
Furthermore, the new CMOS isolator technology enables the high-frequency signals that pass through a component transformer to be detected by a signal receiver circuit consisting of a junction diode and passive components, which in turn transforms the received signals into a low-frequency signals which can be handled by digital components. This will result with reduced size transformer operating at high frequency, making it possible for the isolators to operate at high speed. The newly developed technology will make it possible for integration of the discrete components of an inverter, including an MCU, multiple isolators and high voltage circuits in a single package, resulting in further miniaturization and reduction in cost of inverter circuits. The application of this new technology can be extended to high-speed communication interfaces that is used in medical and industrial equipment, or isolated interface inside display interfaces that needs both high-voltage and high-speed drive, just to name a few.