Over-voltage protection accounting for battery droop
An over-voltage detection and correction system for a transmitter of a mobile terminal that accounts for battery droop during a transmit burst is provided. In general, prior to ramp-up for a first transmit burst, a voltage of the battery of the mobile terminal at a no-load condition is measured. After ramp-up for the transmit burst, the voltage of the battery is measured at full-load, and a current provided to a power amplifier of the transmitter at full-load is detected. Based on the measured voltage of the battery at no-load, the measured voltage of the battery at full-load, and the detected current provided to the power amplifier at full-load, a resistance of the battery is determined. The resistance of the battery is thereafter used to compensate for battery droop during over-voltage detection and correction for one or more subsequent transmit bursts.
1. A mobile terminal comprising:
an over-voltage detection and correction system adapted to:
i) measure a battery voltage of a battery of the mobile terminal at a no-load condition to provide a no-load battery voltage;
ii) measure the battery voltage of the battery at a full-load condition during a first transmit burst to provide a full-load battery voltage;
iii) measure a current provided from the battery to power amplifier circuitry in a transmit chain of the mobile terminal at a full-load condition during the first transmit burst to provide a full-load current;
iv) determine a battery resistance based on the no-load battery voltage, the full-load battery voltage, and the full-load current; and
v) compensate for a voltage droop of the battery expected for a subsequent transmit burst based on the battery resistance during over-voltage detection and correction for the subsequent transmit burst.
2. The mobile terminal of claim 1 wherein in order to compensate for the voltage droop of the battery, the over-voltage detection and correction system is further adapted to:
determine a projected full-load current to be provided from the battery to the power amplifier circuitry during the subsequent transmit burst;
provide the voltage droop of the battery expected for the subsequent transmit burst based on the projected full-load current and the battery resistance;
generate an actual battery voltage for the subsequent transmit burst based on the voltage droop of the battery expected for the subsequent transmit burst; and
perform over-voltage detection and correction based on the actual battery voltage.
3. The mobile terminal of claim 2 wherein the over-voltage detection and correction system is further adapted to determine the projected full-load current based on detected current provided from the battery to the power amplifier circuitry during ramp-up for the subsequent transmit burst.
4. The mobile terminal of claim 2 wherein the over-voltage detection and correction system is further adapted to multiply the projected full-load current and the battery resistance to provide the voltage droop of the battery expected for the subsequent transmit burst.
5. The mobile terminal of claim 4 wherein the over-voltage detection and correction system is further adapted to subtract the voltage droop of the battery expected for the subsequent transmit burst from a no-load battery voltage measured prior to ramp-up for the subsequent transmit burst.
6. The mobile terminal of claim 2 wherein the over-voltage detection and correction system is further adapted to provide the voltage droop of the battery expected for the subsequent transmit burst and generate the actual battery voltage for the subsequent transmit burst based on the equation:
V ACTUAL =V BAT — NO — LOAD −R B ·I FULL — LOAD — PROJECTED ,
where V ACTUAL is the actual battery voltage, V BAT — NO — LOAD is a no-load voltage of the battery measured prior to ramp-up for the subsequent transmit burst, R B is the battery resistance determined for the first transmit burst, and I FULL — LOAD — PROJECTED is the projected full-load current for the subsequent transmit burst, wherein R B ·I FULL — LOAD — PROJECTED is the voltage droop of the battery expected for the subsequent transmit burst.
7. The mobile terminal of claim 1 wherein the over-voltage detection and correction system is further adapted to determine the battery resistance based on the equation:
R B =V BAT — NO — LOAD −V BAT — FULL — LOAD /I FULL — LOAD ,
wherein R B is the battery resistance, V BAT — NO — LOAD is the no-load battery voltage, V BAT — FULL — LOAD is the full-load battery voltage, and I FULL — LOAD is the full-load current.