Rev. 1.10
144
November 04, 2019
Rev. 1.10
145
November 04, 2019
HT45F5Q-3
Battery Charger Flash MCU
HT45F5Q-3
Battery Charger Flash MCU
Application Descriptions
Introduction
According to the battery current condition, the charger can use a Buck circuit to implement charger
management. The battery charging contains constant voltage Mode and Constant current Mode. The
HT45F5Q-3 device is specifically designed for battery charger applications. The above-mentioned
function control can be implemented by the integrated battery charger management, these are
described below.
Functional Description
Operating Principle
The device contains a battery charge module which consists of three operational amplifier
(OPA0~OPA2) functions, a 14-bit D/A converter (DAC0) and a 12-bit D/A converter (DAC1)
functions. The open drain OPA0~OPA1 and DAC0~DAC1 are used for constant current and constant
voltage signal control. The OPA output can directly drive the photo-coupler, which makes the PWM
IC on the primary side can implement output power adjustment, shown in the figure below. The
internal 20 times amplifier OPA2 is used to amplify the charge current signal, thus increasing the
current resolution and reducing the detecting resistance power consumption. The constant voltage
mode, constant current mode and constant current and constant voltage resolution increasing method
are described as follows.
U2
PC817
R9
D1
C2
Battery1
R1
Rectifier/
Filter/
Regulator
Q1
Current Mode
PWM IC
R3
R4
R6
AC
DC
5V LDO
C3
C4
5V
D2
B+
5V
R2
C6
5V
B+
AC_N
AC_L
C5
R5
C7
R7
C9
R8
C8
VDD
VSS
OPA2P
OPA0N
OPA1N
OPAE
C1
DAC1 12Bit
DAC0 14Bit
ADC
OPA0
OPA1
OPA2
19R
R
HT45F5Q-3
Battery Charge Module
Constant Current Mode Description
Constant current charging means that the charge current will remain at a constant value no matter
how the battery internal resistance changes. The principle is that the charge current flows through
the detecting resistor R1 and in turn generates a voltage, which will be input to the OPA0 negative
terminal through the OPA0N pin. The difference between the OPA0N voltage and the D/A converter
voltage is amplified and then output on the OPAE pin. This output will be sent to the PWM IC via a
photo-coupler. If the OPA0N voltage is lower than the DAC0 voltage, the PWM IC will increase the
PWM duty cycle and vice versa.
Note: The DA0H and DA0L registers are used to set the maximum current threshold.