Reverse battery protection for battery-powered devices
Reverse battery protection circuits for devices powered by batteries coupled in parallel can include both P-channel and N-channel MOSFETs. Each positive battery terminal connector of a battery-powered device can be coupled to a gate of an N-channel MOSFET or to both a gate of an N-channel MOSFET and a gate of a P-channel MOSFET. In some embodiments, each negative battery terminal connector of the device can be connected to a gate of a P-channel MOSFET. In the event of a reverse battery connection, one or more of the protection circuit's P-channel and N-channel MOSFETS can switch to a non-conductive state to isolate the device's load from an incorrectly installed battery and prevent the incorrectly installed battery and/or other parallel-coupled battery from prematurely discharging. Methods of protecting a load from a reverse battery connection are also provided, as are other aspects.
1. A reverse battery protection circuit comprising:
a first P-channel MOSFET having a gate, a drain, and a source;
a second P-channel MOSFET having a gate, a drain coupled to the gate of the first P-channel MOSFET, and a source coupled to the source of the first P-channel MOSFET;
a first N-channel MOSFET having a gate coupled to the gate of the second P-channel MOSFET, a drain coupled to the drain of the second P-channel MOSFET and to the gate of the first P-channel MOSFET, and a source;
a first load terminal coupled to the drain of the first P-channel MOSFET;
a first positive battery terminal connector coupled to the source of the first P-channel MOSFET and to the source of the second P-channel MOSFET, the first positive battery terminal connector configured to electrically connect to a first battery terminal;
a second positive battery terminal connector coupled to the gate of the first N-channel MOSFET and to the gate of the second P-channel MOSFET, the second positive battery terminal connector configured to electrically connect to a second battery terminal;
a first negative battery terminal connector configured to electrically connect to a third battery terminal;
a second negative battery terminal connector configured to electrically connect to a fourth battery terminal; and
a second load terminal; wherein:
the first negative battery terminal, the second negative battery terminal, the second load terminal, and the source of the first N-channel MOSFET are coupled to each other.
2. The reverse battery protection circuit of claim 1 further comprising:
a third P-channel MOSFET having a gate, a drain coupled to the first load terminal and to the drain of the first P-channel MOSFET, and a source coupled to the second positive battery terminal connector;
a fourth P-channel MOSFET having a gate coupled to the first positive battery terminal connector, a drain coupled to the gate of the third P-channel MOSFET, and a source coupled to the source of the third P-channel MOSFET and to the second positive battery terminal connector; and
a second N-channel MOSFET having a gate coupled to the gate of the fourth P-channel MOSFET and to the first positive battery terminal connector, a drain coupled to the drain of the fourth P-channel MOSFET and to the gate of the third P-channel MOSFET, and a source coupled to the first negative battery terminal, to the second negative battery terminal, to the second load terminal, and to the source of the first N-channel MOSFET.
3. The reverse battery protection circuit of claim 2 wherein:
the first positive battery terminal connector and the first negative battery terminal connector are configured to electrically connect to respective battery terminals of a first battery; and
the second positive battery terminal connector and the second negative battery terminal connector are configured to electrically connect to respective battery terminals of a second battery.
4. The reverse battery protection circuit of claim 2 wherein
the first positive battery terminal connector has a side contact configuration; and
the second positive battery terminal connector has a side contact configuration.
5. A battery-powered biosensor meter comprising:
a microcontroller configured to determine a property of an analyte in a fluid;
a memory coupled to the microcontroller to store measurement results;
a battery holder configured to receive a plurality of batteries;
the reverse battery protection circuit of claim 2 coupled to the battery holder, the microcontroller, and the memory; and
a housing configured to house the microcontroller, the memory, the battery holder, and the reverse battery protection circuit of claim 2 .
6. A method of protecting a load from a reverse battery connection, the method comprising:
coupling a gate of a first P-channel MOSFET to a drain of a second P-channel MOSFET and to a drain of a first N-channel MOSFET;
coupling a drain of the first P-channel MOSFET to a first load terminal;
coupling a source of the first P-channel MOSFET to a source of the second P-channel MOSFET and to a first positive battery terminal connector, the first positive battery terminal connector configured to electrically connect to a first battery terminal;
coupling a gate of the second P-channel MOSFET to a gate of the first N-channel MOSFET and to a second positive battery terminal connector, the second positive battery terminal connector configured to electrically connect to a second battery terminal; and
coupling a source of the first N-channel MOSFET to a first negative battery terminal connector, to a second negative battery terminal connector, and to a second load terminal; wherein:
the first negative battery terminal connector is configured to electrically connect to a third battery terminal; and
the second negative battery terminal connector is configured to electrically connect to a fourth battery terminal.
7. The method of claim 6 further comprising:
coupling a drain of a third P-channel MOSFET to the first load terminal and to the drain of the first P-channel MOSFET;
coupling a source of the third P-channel MOSFET to the second positive battery terminal connector and to a source of a fourth P-channel MOSFET;
coupling a gate of the third P-channel MOSFET to a drain of the fourth P-channel MOSFET and to a drain of a second N-channel MOSFET;
coupling a gate of the fourth P-channel MOSFET to the first positive battery terminal connector and to a gate of the second N-channel MOSFET; and
coupling a source of the second N-channel MOSFET to the first negative battery terminal, to the second negative battery terminal, to the second load terminal, and to the source of the first N-channel MOSFET.
8. The method of claim 6 further comprising providing a battery holder for receiving the first positive battery terminal connector and the first negative battery connector, wherein the first positive battery terminal connector has a side contact configuration.
9. The method of claim 6 further comprising coupling a microcontroller configured to determine a property of an analyte in a fluid to the first and second load terminals.