New Industry Products

LAPIS Semi Announces Dual Power Supply Control LSI for Solar and Battery Driven Devices

March 05, 2012 by Jeff Shepard

LAPIS Semiconductor, a ROHM Group company, has developed the power controlling "ML9077/ML9078 series" LSIs for small sized electronics using dual power supplies like solar panel and batteries such as coin battery. These LSIs provide stable power supply to electronic components like microcontrollers by controlling the switching between the primary/secondary (rechargeable) batteries and solar panels as well as perform the charge control of power supplied from the solar panels to the secondary battery.

Energy generation by solar panels have been already adopted as power source in the area of small sized electronics such as clocks, calculators, weather stations, remote controls, cycle meters, compact games and others, for postponement of battery life or elimination of battery. However, adoption of these products to solar energy has proven to be difficult due to the increase of development cost and system components as it is required to configure a new electronic system combining both. Additionally, safety functions such as voltage control of the power supplied to the microcomputer, protection of abnormal current to the battery as well as control circuits have to be considered as well.

Based on the expertise in designing LSIs at ultra-low power consumption as well as solar panel and battery power source systems, LAPIS has now developed the ML9077/ML9078 . These LSIs, the first in the industry, have the relevant safety functions and features for the customers to use solar energy safely and easily on their applications.

It automatically controls the power supplied to the microcontroller and peripheral components from a rechargeable battery (VBAT) as well as from the solar panels to the rechargeable battery based on the remaining charge of the battery. Protection functions are built in, including charging stop with overcharge detection and malfunction prevention that prevents failures due to power supply stoppage caused by low voltage. The result is significantly less peripheral circuitry compared with conventional products. In addition, current consumption is less than 80nA (at 25°C).

ML9078 continuously monitors the voltage generated by the solar panel (VSC) and at the primary battery (VBAT) and selects the higher voltage for supply to the microcontroller and peripheral devices. It protects the primary battery by preventing the flow of generated current from the solar panel. High voltage supply to the microcontroller is prevented by converting the generated voltage by the solar panel to low voltage. In addition, protection functions are built in such as power supply selection monitoring, reducing peripheral circuitry significantly. Current consumption is less than 80nA (at 25°C). For some products the current consumption is less than 150nA (at 25°C).

As the common characteristics of these LSIs, they both control dual power sources of solar panel and battery on an entirely-independent basis; there is no need to control by any application or loading of another component, which facilitates system-costs reduction and easy build-in. Additionally, these LSIs contribute to miniaturization of customers’ products; the vent size of a chip product is 1.5mm or less and the size of a package is of 3mm x 3mm in case of a WQFN type.

ML9077 and ML9078 have been already put to volume production. Three versions of ML9078 are available so that various types of solar panel and microcontrollers can be suited.

More news and information regarding the latest developments in Smart Grid electronics can be found at Darnell’s SmartGridElectronics.Net.