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2.3.1 Control board
The SP3 control board consists of three parts, the power supply part, the main
control part and the monitoring part.
The power supply part includes an ACDC conversion module, an on/off control
circuit, a DC power conversion circuit, a standby sound and light alarm circuit, and a
battery charge and discharge management circuit.
The ACDC conversion module converts the input AC power supply of 100-240VAC
and 50/60Hz to an output of DC 15V.
The on/off control circuit can combine three power inputs of ACDC input, external
DC input, and internal battery into VBUS, and the priorities of ACDC input and
external DC input are higher than that of internal battery; the on/off signal can
convert VBUS into VPP output.
VBUS is not controlled by the on/off signal, but VPP is controlled by the on/off signal.
VBUS is stepped down to VCCB (5V) through the LDO circuit (U9 TLV70450).
VCCB is stepped down to VBB (3.3V) through the LDO circuit (U13 SPX5205). VPP
is stepped down to VCC (5V) through the Buck circuit (U11 TPS5420D). VCC is
stepped down to VDD (3.3V) through the LDO circuit (U12 SPX1117M3). VPP is
boosted to VMM (+18.9V) through the Boost circuit (U6 TPS61175PWP).
The main control CPU controls on/off and provides motor power failure protection
under single fault condition. The monitoring CPU monitors the battery charging
status, detects the power status of each module, controls the battery LED, and
communicates with the CPU of the main control module through the serial port. After
being triggered by the on/off key from the keypad, the main control CPU and the
monitoring CPU simultaneously output the power-on lock signal and the module
power enable signal, so that VCC, VDD, and VMM are sequentially output, and the
entire system is powered on. When the normal shutdown is required, after the main
control CPU detects the shutdown signal, it notifies the monitoring CPU to cancel
the power-on lock signal through the serial port, and finally the main control CPU
completes the shutdown.
Battery charging and discharging management circuit adopts BQ24103RHLR. The
on/off charging current is designed to both 650±50mA (The charging time of the
single battery does not exceed 6 h. The charging time of the dual battery does not
exceed 12 h). The battery is at a voltage of 8.1±0.2V when fully charged.
When the battery voltage is too low and the AC power and external DC power are off,
the backup sound and light alarm circuit triggers the buzzer to sound at a frequency
of 2.73Hz±0.5V, and drives the red alarm lamp to be continuously illuminated.
When the monitoring CPU detects that the VDD power supply is abnormal or the
communication with the CPU of the main control module is abnormal, the buzzer
sounds and the power of the stepper motor is turned off.
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