Multiple battery switchover circuits

• US 5,764,032 A
• Filed: 03/06/1997
• Issued: 06/09/1998
• Est. Priority Date: 03/06/1997
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Moore, Bruce Dudley
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Shin, K.
• Application Number:
  US08/810,828
• Time in Patent Office: 460 Days
• Field of Search: 320/5, 320/6, 320/15, 320/56, 320/126, 307/66
• US Class Current: 320/126
• CPC Class Codes: H02J 7/0024 Parallel/serial switching of connection of batteries to charge or load circuit

Abstract

Multiple battery switchover circuits for selective interconnecting any one of multiple batteries to a load or a charger while maintaining isolation with other batteries of the system. The present invention maintains the required isolation and interconnection capabilities using only three MOSFETs per battery instead of the four required by the prior art. The three MOSFETs for any one battery in the switchover circuit are connected with one current carrying connection in common, with the other current carrying connection of the MOSFETs being coupled to the charger, the load and a respective battery, respectively. Appropriate connection of the MOSFETs assures that as to any possible conduction path through two of the three MOSFETs, one of the MOSFETs has its parasitic diode back biased. Alternate embodiments are disclosed.

Claims

1. A multiple battery switchover circuit comprising:

a first source of power;

a second source of power;

a load;

and in plurality;

first, second and third field effect transistors, each having a substrate, a control gate, a source electrode and a drain electrode, the substrate of each field effect transistor being electrically coupled to one of the electrodes of the respective field effect transistor, the substrate and the other electrode of each field effect transistor forming a parasitic body diode electrically coupled between the two electrodes of the respective field effect transistor, the parasitic body diode being electrically conductive when a first of the two electrodes is at a higher voltage than a second of the two electrodes and being substantially nonconductive when the first of the two electrodes is at a lower voltage than the second of the two electrodes;

first electrode of the first, second and third field effect transistors being coupled together;

second electrode of the first field effect transistor being coupled to the load and to the first source of power;

second electrode of the second field effect transistor being coupled to the second source of power;

second electrode of the third field effect transistor being adapted for coupling to a respective battery.

2. The multiple battery switchover circuit of claim 1 wherein the field effect transistors are p-channel MOSFETs.

3. The multiple battery switchover circuit of claim 1 wherein the field effect transistors are n-channel MOSFETs.

4. The multiple battery switchover circuit of claim 1 wherein the second source of power is a buck-topology charger.

5. The multiple battery switchover circuit of claim 1 wherein the number of batteries the multiple battery switchover circuit may be coupled to are two.

6. A multiple battery switchover circuit comprising:

a first source of power;

a second source of power;

a load;

and in plurality;

first, second and third p-channel MOSFETs, each having a substrate, a control gate, a source electrode and a drain electrode, the substrate of each field effect transistor being electrically coupled to the source electrode of the respective field effect transistor, the substrate and the drain electrode of each field effect transistor forming a parasitic body diode electrically coupled between the two electrodes of the respective field effect transistor, the parasitic body diode being electrically conductive when the drain electrode is at a higher voltage than the source electrode and being substantially nonconductive when the drain electrode is at a lower voltage than the source electrode;

the drain electrode of the first, second and third field effect transistors being coupled together;

the source electrode of the first field effect transistor being coupled to the load and to the first source of power;

the source electrode of the second field effect transistor being coupled to the second source of power;

the source electrode of the third field effect transistor being adapted for coupling to a battery.

7. The multiple battery switchover circuit of claim 6 wherein the second source of sower is a buck-topology charger.

8. The multiple battery switchover circuit of claim 6 wherein the multiple battery switchover circuit is a two battery switchover circuit.

9. A multiple battery switchover circuit comprising:

a first source of power;

a second source of power;

a load;

and in plurality;

first, second and third n-channel MOSFETs, each having a substrate, a control gate, a source electrode and a drain electrode, the substrate of each field effect transistor being electrically coupled to the drain electrode of the respective field effect transistor, the substrate and the source electrode of each field effect transistor forming a parasitic body diode electrically coupled between the two electrodes of the respective field effect transistor, the parasitic body diode being electrically conductive when the source electrode is at a higher voltage than the drain electrode and being substantially nonconductive when the source electrode is at a lower voltage than the drain electrode;

the source electrode of the first, second and third field effect transistors being coupled together;

the drain electrode of the first field effect transistor being coupled to the load and to the first source of power;

the drain electrode of the second field effect transistor being coupled to the second source of power;

the drain electrode of the third field effect transistor being adapted for coupling to a battery.

10. The multiple battery switchover circuit of claim 9 wherein the second source of power is a buck-topology charger.

11. The multiple battery switchover circuit of claim 9 wherein the multiple battery switchover circuit is a two battery switchover circuit.