IC card intelligent gas meter for low-power design

IC card intelligent gas table structure is shown in Figure 1.

　　

　　

Figure 1 IC card intelligent structure of the gas meter

IC card intelligent gas meter is in General on the basis of gas meters and electronic controllers, valves and the sampling pulse generator (such as Reed pipe, Hall elements, etc.).

Counter each week issued a pulse signal, the signal will be fed into the CPU, pulse CPU according to the establishment of procedures for counting and operations, and then computes results compared with the set value, when comparing the results to a certain extent when the alarm and switch into the valve and other directives.

2 low-power design

① valve

Valve is IC card intelligent gas meter enforcement agency is realization of prepaid function key device, when the user tables in the margin to zero, you should be able to cut off the gas source, valve adopts micropower bistable design.

IC card intelligent gas meter using battery power, the valve opens and closes with bistable properties, i.e. the valve open and close requires a transient current, open and close the State remains the need to consume energy. To meet the needs for IC card intelligent gas meter overall appearance, use of Mechatronics design thought, the valve built-in.

② low power driver circuit

Valve opening closing moments need high voltage and high current.

To solve the power problem, design a step-up DC power converter, it is mainly composed of switching valve, energy storage inductors, continued flow diode, filter capacitors and comparer. Single-chip through a PIN-level change control switching-off of. Switch tube breakover, energy storage inductor voltage + 6V, continued flow diode is bias due status, battery by switch on energy storage, energy storage inductor inductance charging current linear increase in the energy stored in storage inductors. Switch tube cut-off time, through the reduction of energy storage inductor current, energy storage inductor voltage phase ends, continued flow diode conduction, thermal storage inductor of electric energy stored in the battery power of stacking together with continued flow diode capacitance charging for filtering. Through continued flow diode, capacitor charging the battery on the filter, and then through the comparator judgment voltage level to decide whether to stop.

③ low-power microcontroller

Design-time, try to use low-power microcontroller.

PIC16C62 series single-chip is a United States Microchip company production of 8-bit microcontroller, thanks to CMOS technology, therefore its power consumption is very low, you can easily use the battery to supply power directly. Its main features are: operating frequency of up to 20 MHz, oscillator RC oscillator can be adopted or

Crystal oscillator; operating voltage (DC) 3.5 ~ 6.0 V; low power consumption, operating modes of operating current < 2 mA; built-in WatchDog (watchdog) circuit, to protect against external interference or internal programming errors caused by the microcomputer operation breakdown; the use of single-byte instruction structure; one-time programmable (OTP) chip.

PIC16C62 series MCU most prominent features of sleep (SLEEP) mode.

In sleep mode, A typical current < 3, available through the software settings enter sleep mode, and can be used by any interrupt wakes up. When the user uses the gas, single-chip goes into run mode and stop using gas for a period of time, then goes to sleep mode, thus

IC card intelligent gas meter can successfully achieve low power consumption.

④ peripheral devices with low power consumption

Data and information displayed with low-voltage micropower LCD monitor, choose the Philip drive company PCF8576 chip.

Chip voltage (DC) in the range of 2 to 6 V, using the I2C bus protocol. Voltage detection IC choosing AN051, the chip in a voltage 1.5 V, A typical 1.5.

⑤ partition time-sharing power supply

To reduce power consumption, IC card intelligent gas tables for partitions time-sharing service mode.

Use the power switch to control added to the memory chip, IC card interface pull-up voltage, guaranteed without this part when you turn off the power circuit. Added to the LCD drive voltage PCF8576 chip enters sleep mode in the system through the switch control shutting down when show that reduce power consumption.

⑥ software design

Software design in close connection with IC card intelligent gas meter control mode, fully embodies the information on Ic card read-write, card type judgment, measurement signals and data processing, voltage monitoring and power protection function and signal security, software reliability and anti-jamming, etc are well designed.

The main process is shown in Figure 2.

　　

　　

Figure 2 main process

Microcontroller power consumption with the CPU work time increased, so try to use the software instead of hardware, using a scheduled outage to replace software cycle delay works and static display behavior, reduces CPU time.