Hi group,
Here are some measurements that I made.
The inductor used for all these tests is a TDK VLF50122R2M2R0 (Digikey 445-4232-6-nd)
This has a DCR of 83m Ohm.
No Load Input CurrentThe Iq increases with lower Vin. The no load input power is around 27 uW.
At 20uA this would discharge a 2Ahr AA battery in 100K Hours (11 years). The battery self-discharge is probably in the same order of magnitude.
Efficiency and Power Loss at Iout=50mAThis graph shows the efficiency and power loss at a moderate load of 50mA.
Efficiency at 250mAThis graph shows the measured efficiency at 250mA.
Battery ESR MeasurementI measured a Duracell Procell AA battery using a transient load. The load is configured to step the current from 100 to 200mA current. The battery voltage was measured with a scope directly across the battery terminals
The ESR = dv/di
= 0.0217/0.1 =
0.217 Ohms (This is a fresh battery)I repeated the test at 500 Hz to look for any high frequency effects. The scope shows the battery is very resistive.
Transient Load Testing of the Boost circuitI applied the transient load test to the boost circuit. At 100 to 200mA the output is dominated by the voltage ripple. The ripple is moderate, because the IC is operating in burst mode to reduce losses at light currents.
At higher currents, 400 to 500 mA, the IC operates in the continuous mode and the transient response is revealed:
The boost circuit does a good job of shielding the load from the ESR of the battery, but the load still has to deal with the transient response of the boost supply.
Switch Node WaveformThis picture shows the switch node. You can see the top MOSFET being turned on, this is typical of a synchronous boost supply.
Thermal ImageThe Lab is around 20
oC.
The boost converter was running for an hour with Vin=1.2 and Iout=250 mA.
The IC was at 27 and the 24.8C
Regards,
Jay_Diddy_B