Battery ChargerVoltage Regulators Circuit Diagrams

Battery Charging Regulator Schematic Circuit Diagram

Philips IC TEA1100: Fast and Efficient Battery Charging

The Philips IC Type TEA1100 employs the delta-peak principle to achieve rapid and effective charging of nickel-cadmium (NiCd) and nickel-metal-hydride (NiMH) batteries. The primary function of the delta-peak battery charging regulator is to monitor and assess changes in the battery voltage. Charging is halted if the voltage at pin 7 drops 1% or more below the average maximum. As per the manufacturers’ data sheet, the voltage at pin 7 should ideally be within the range of 0.385–3.85 V. The potential divider R4-R5 is instrumental in ensuring that the battery electromotive force aligns with this specified range.

The values of these resistors are given by:

  • R4/(R4+R5).n.-1.8 <3.85:
  • R4/(R4+R5) < 2.14n;
  • R4/(R4+R5).n.1.1 >0.385;
  • R4/(R4+R5) >0.35n.

The charging current 4 is given by:

  • IC = 1•25Rsense/Rshunt’Rref.

Battery charging regulator Schematic diagram

Where Rsense is R10; Rshunt is R8 parallel with R9; and Rref is R2. Timeout (TO) is a safety facility of the IC. If, for whatever reason, no maximum can be detected, the IC stops charging after the timeout. This time constant is given by:

TO = 226.0.93.RrefCosc,

where Cosc = C3. Note that both timeout and charging current are influenced by R2. When the charging current and timeout 0 are being determined, the value of R2 must, therefore, be fixed and that of C3 must be variable.

TEA1100’s ‘Maintain Charge’ Mode for Fully Charged Batteries

Upon reaching full charge, the TEA1100 transitions into the ‘maintain charge’ mode. In this state, during 1/10 of the regular charging time, only 1/2 of the standard charging current is active. Essentially, the battery undergoes a trickle charge at 1/20 of the normal charging current. The formula I_trickle = I * 2.5 * R_sense / (1 + R_shunt / R_N) determines the trickle-charge current, where the current is influenced by the shunt resistor’s voltage drop and controlled by transistors through pin 2 of the IC. The stability of the circuit is maintained through the presence of capacitor C2.

Battery Connection and LED Indicators

When K1 has no connected battery or when a battery is undergoing trickle charging, the LED DI flashes. If the voltage at pin 7 drops, the LED lights continuously. The supply voltage at pin 12 must fall within the range of 5.65–11.5 V. The quiescent current, when all outputs are off, is approximately 4 mA. The TEA1100 IC extends its utility to various applications, with additional details provided in Philips’ Data Sheets TEA1100 and TEA1100T.


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