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IMPROVED SAFETY BATTERY FOR USE IN PORTABLE RADIO

IP.com Disclosure Number: IPCOM000005611D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-19
Document File: 2 page(s) / 71K

Publishing Venue

Motorola

Related People

Gordon Wayne James: AUTHOR

Abstract

Figure 1 shows a typical rechargeable battery used to power a portable radio. The battery has a set of contacts, Ji and J2, through which the battery is charged, and a set of contacts, J3 and J4, through which power is supplied to the radio. Diode CR1 is used to prevent accidental shorting of the battery across Jl and J2 while the battery is attached to the radio. When the battery is removed from the radio it can still be shorted across J3 and J4.

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cm MOTOROLA Technical Developments Volume 6 October 1986

IMPROVED SAFETY BATTERY FOR USE IN PORTABLE RADIO

by Gordon Wayne James

   Figure 1 shows a typical rechargeable battery used to power a portable radio. The battery has a set of contacts, Ji and J2, through which the battery is charged, and a set of contacts, J3 and J4, through which power is supplied to the radio. Diode CR1 is used to prevent accidental shorting of the battery across Jl and J2 while the battery is attached to the radio. When the battery is removed from the radio it can still be shorted across J3 and J4.

   Figure 2 shows a battery which is more difficult to short when it is removed from the radio and which has the added advantage that it facilitates an electronic ON - OFF control in the radio. The power MOSFET (Siemens BUZ-71) is added in series with the negative terminal of the battery. This device prevents current being drawn from the battery unless a positive voltage is applied to its gate. In the most elementary implementation this is done by means of a mechanical switch (Sl) which connects the gate to the positive terminal of the bat- tery. Closing this switch allows the radio circuits to draw power from the battery. The power MOSFET has a series resistance of approximately 1 ohm when it is turned on in this manner. Resistor Rl keeps the gate from floating when switch Sl is open and insures that the MOFSET will turn off. Since switch Sl is not required to carry much current it could be easi...