Micro-power design method based on lithium battery power supply equipment based on single chip microcomputer

　　Author ：Iflowpower – Portable Power Station Supplier

About most single-chip microcomputer systems, due to the speed of the single-chip running speed, the single-chip microcomputer has a lot of free wait hours in the process of work. In some cases, the waiting time of the system can even achieve more than 95% of the total working time. During the waiting process, the single chip does not work, just waiting for a step, or is judged in a loop.

In this process, most of the circuits inside the microcontroller can work in sleep, which can greatly reduce the power consumption of the microcontroller. At the same time, the relevant external circuits can be operated in sleep, so that the power supply of the entire product is greatly reduced. This non-sustainable work is characterized by the basic ideas of micro-power design.

In addition, according to the characteristics of the product, more design details. Choosing a suitable CPU chip is a key to the key designer design. There are many types of single-chip microcomputer, and all of them are for a particular application, and the appropriate microcontroller can be selected according to the specific application.

In applications where you want to perform a micro-power design, you can choose from the following rules: 1. Select the microcontroller that minimizes external circuitry. With the rapid development of integrated circuit process technology, the real monolithic single-chip microcontroller system has gradually become mainstream products.

2. Watch the comparative operating current and quiescent current. Due to the difference in the process, the internal working current of the single-chip microcontroller, the static current is not the same, and some even differ.

When choosing a microcontroller, it is necessary to consider its operating current, but also carefully consider the static current in sleep. 3. By comparison, select a dedicated low-power microcontroller, can more flexibly control its power consumption, which makes it as possible to operate as much power-saving mode under the premise of meeting design requirements.

4. Select the right ROM, RAM. Generally speaking, the larger the memory is, the greater the power consumption.

With the design requirements, the ROM, RAM is used as much as possible. 5. Select the appropriate working clock frequency.

At lower clock frequencies, the single-chip power consumption is also low. Take MSP430F1121 as an example. When working in 1 MHz's frequency, the typical current consumption is 300ua; while working at 4096 Hz's frequency, there is only 3UA.

6. Select the number of suitable IO pin, and the appropriate IO driver capability and display driver capability. The more the number of single-chip drives driven, the greater the power consumption.

7. Select the appropriate single-chip microcomputer to achieve a single piece of hardware, save a large number of hardware development and debugging work, improve work efficiency, systematic reliability, anti-interference ability has been significantly improved, while the system cost is lowered , More suitable for miniaturization and portability, which has decisive uses to reduce system power consumption. Low-power design strategy a.

Make internal circuits to work selectively, and all microcontroller internal circuits are not used in the design, and those that are not used will have additional power consumption. In applications where you want to perform micro-power design, you can program the internal special function registers, select Different function modules, the function module that does not use is stopped, reducing system invalid power consumption. b.

Product low voltage design can reduce product power consumption, the higher the working voltage of the single-chip microcomputer, the longer the internal transistor in the magnification area, the greater the power consumption of the single-chip unit. Due to the advanced chip production process, the voltage range of the single chip microcontroller is generally wide, such as the normal operation within the 1.8V ~ 5V supply voltage range.

In order to reduce system power consumption, you can use low voltage design as much as possible. The single-chip supply voltage range can be further widened, in particular in portable or handheld devices, can be safely used as power supplies, without having to pay attention to whether the discharge process voltage curve is balanced, whether the microcontroller is affected under low voltage Normal work, it is not necessary to specifically add a regulated circuit due to battery power, thereby reducing a large amount of power consumption. c.

When I idle, the power consumption of the single-chip microcontroller using the low speed clock signal is proportional to its operating frequency, the higher the system running, and the power supply will increase accordingly. Figure 1 shows the relationship curve of the current and main clock frequency on the 80C31 single-chip microcomputer VCC of Philips, which can be seen that the current on the VCC has increased in line with the new, and its power consumption is added. Also add new increase with the new frequency of the main clock frequency.

In order to better reduce power, two separate clock systems are integrated in many microcontrollers, namely high-speed primary clocks, low-speed subclocks, and use low-speed sub-clocks without high-speed operation. Basic on-time requirements. The main clock of some single-chip microcomputer can also be reset by a function register.

When the function is met, the main clock frequency is reduced according to a certain scale to reduce power consumption. You can change the clock frequency to the special function register online by software, or perform the primary clock and the subclock switch by software, or the primary clock and the subclock switch are changed. d.

To reduce power consumption as much as possible, usually the microcontroller is supplied in a variety of working modes. When you are idle, you can enter the sleep mode. When there is an event, you can return to normal mode of operation, so Can guarantee the system power saving and does not affect normal work.

Different single-chip opportunities have different working modes, such as the 51 series of microcontrollers have idle mode and power-down mode. In different working modes, some of the function modules in the single-chip core will be set to sleep. If the MSP430 series single-chip microcomputer has 6 different working modes, except for normal operating mode, the remaining five are low power mode, and in these modes, the CPU, internal clock, internal bus, Until the internal crystal is all closed, making the power consumption of the microcontroller to the smallest.

Only when an interrupt request or reset occurs, the system is awakened to enter the normal mode of operation. The micro-power design of the external circuit's micro-power design single-chip peripheral circuit is very complicated, and it is also very important for the overall power consumption of the product. Complex, huge peripheral circuits will bring great power consumption, so we should use less external circuitry to use the resources inside the microcontroller as much as possible.

As a battery powered by a battery, its static power consumption is preferably a few micro-safety ~ dozens of microamines, because this part of the current is added in the device, it is a common supply current, in the system does not work In case, it will cause a lot of electric energy waste. Therefore, in the design, the external circuit should be minimized and reduce the portion of the external circuit in static power. At the same time, we must consider the following problems: 1.

Other devices other than the single-chip microcontroller in the system as much as possible, such as using CMOS chips, less bipolar transistor gate circuit, because the bipolar circuit must be one Constant maintenance current, new circuit static power consumption. 2. According to the requirements of the chip, the unused pins will be connected to the ground or high, and the floating input feet will increase the quiescent current of the chip.

3. Use less pull-up or pull-down resistors on the IO pin, these resistors will consume certain static currents. 4.

The design of the simulation portion of the data acquisition can use a BiCMOS operational amplifier of rail-to-rail, such as the LMV824 for replacing the LM324, the power supply can be as low as 2.5V, unit bandwidth to 5MHz, only 250A /aisle. 5.

Design the power control circuit of the external device, so that the external device or device turns off the power supply during the non-operating, reducing invalid power consumption. The price of low-power devices is typically slightly higher. If the price is allowed, it can usually find the corresponding low voltage, low power alternative products.