Hello,
I am having issues with getting the pass transistors to turn on when using the UC2906/UC3906. My input supply is set at 24V and I am attempting to charge a Sealed Lead Acid battery(12V batter with 105 Amp/hours). My shunt resistor is set to .025Ω so that the maximum current (Imax) is 10A. I used the datasheet for the bq24450(as specified in other topics for the UC3906) to select the external pass transistor. I have chosen the external Quasi-Darlington to supply the 10A needed for charging. For Q1, I have selected a PNP BJT transistor(TIP30). For Q2, I have selected a NPN BJT transistor(BUV26).
When I apply power from the supply, I am getting 24V across pins 5 and 6 on the UC2906. , +Vin and GND respectively. So the chip is definitely receiving power, but it is not turning on any of the transistors to provide current to the battery. I am measuring 0V across the shunt resistor, I should be reading .250V when the chip is in the bulk charge state. The battery is at 11.97V, which is well within the bulk charge range.
Could I have selected improper transistor components? Why is the pass element not turning on? The circuit is shown below:
Datasheets can be found here:
UC2906 Datasheet
bq24450 datasheet
UC3906 Application Note
BUV NPN Transistor Datasheet
TIP30 PNP Transistor Datasheet
Thanks!
I am having issues with getting the pass transistors to turn on when using the UC2906/UC3906. My input supply is set at 24V and I am attempting to charge a Sealed Lead Acid battery(12V batter with 105 Amp/hours). My shunt resistor is set to .025Ω so that the maximum current (Imax) is 10A. I used the datasheet for the bq24450(as specified in other topics for the UC3906) to select the external pass transistor. I have chosen the external Quasi-Darlington to supply the 10A needed for charging. For Q1, I have selected a PNP BJT transistor(TIP30). For Q2, I have selected a NPN BJT transistor(BUV26).
When I apply power from the supply, I am getting 24V across pins 5 and 6 on the UC2906. , +Vin and GND respectively. So the chip is definitely receiving power, but it is not turning on any of the transistors to provide current to the battery. I am measuring 0V across the shunt resistor, I should be reading .250V when the chip is in the bulk charge state. The battery is at 11.97V, which is well within the bulk charge range.
Could I have selected improper transistor components? Why is the pass element not turning on? The circuit is shown below:
Datasheets can be found here:
UC2906 Datasheet
bq24450 datasheet
UC3906 Application Note
BUV NPN Transistor Datasheet
TIP30 PNP Transistor Datasheet
Thanks!
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