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Power management refers to how power is efficiently distributed to different components of the system. Power management is critical for mobile devices that rely on battery power. By reducing the energy consumption of components when they are idle, a superior power management system can extend battery life by two or three times. Power management technology is also called power control technology. It belongs to the category of power electronics technology. It is an edge-crossing technology that integrates multiple disciplines such as power conversion, modern electronics, network construction, and automatic control. It has been widely used in industry and energy. Transportation, information, aviation, defense, education, culture and many other fields.

Power management

Power management refers to how power is efficiently distributed to different components of the system. Power management is critical for mobile devices that rely on battery power. By reducing energy consumption when components are idle, excellent

The continuous increase in global energy-saving needs, the continuous advancement of digital technology, the increasing number of split-type power supply structures, and the need for electronic equipment to comply with mandatory energy efficiency regulations, together with the trend of miniaturization and multifunction of portable devices are the driving forces behind the development of power management technology ^[1]

Conventional general-purpose motors used in many kitchen and garage appliances, power tools, and other small appliances generally cannot accurately control speed. These motors are basically only related and on, which is indeed sufficient for some applications. But in other occasions, electric motors for precise variable speed control through digital power management systems have many huge advantages, including ^[3] :

-Lower power consumption

-Higher security

-Longer tool life

-Easier to use

-More advanced operation controls.

-Minimize the risk of electrical disconnection when the appliance is turned on

Cost was once a major obstacle to achieving intelligent motor control in various consumer appliances. This article will introduce a new high-efficiency, low-cost variable-speed universal motor control scheme designed and developed by ZiLOG, and how this scheme uses new on-chip integrated digital modules and advanced analog hardware modules to achieve speed control with minimal external components and firmware. And fail-stop function.

Power management addresses cost and complexity

The "traditional" view popular in the electronics industry is that the components needed for a system that can perform direct and accurate shift control are too expensive to be used in price-sensitive consumer appliances. This view is that instead of developing and implementing such a control system, the retail price of the final product rises and the product becomes unattractive to people. It is better to keep the cost of the electrical appliances and give up the advantages of intelligent motor control. In addition, due to problems such as fast overcurrent detection, fault control, system reliability and efficiency, there are still difficult engineering problems in motor control applications.

Due to the need for fast and accurate loop control and the number and cost of components required to perform intelligent motor control through digital power management, these controller applications set the standard for MCUs, requiring it to provide first-class performance and rich integration Advanced functions to simplify the closed-loop control design in the field of general motor control.

In recent years, a microcontroller (MCU) dedicated to motor control has come out, integrating 8-bit calculation engine, analog-to-digital converter (ADC), comparator, counter, timer and other circuits to control the speed of the motor to meet the load Power requirements. Due to the fast and precise closed-loop control and the small number and cost of supporting components required, this controller sets a new benchmark in MCU expectations. The problem facing MCU manufacturers is how to ensure that the appropriate external components and functions are integrated while maintaining product price appeal to consumers. Source: Big Bit Semiconductor Device Network

A best approach to power management

Figure 1 shows a low cost and efficient digital power management solution for advanced motor control, especially general motor control applications. The on-chip analog peripherals are developed by ZiLOG and integrated into one of its 8-bit MCUs.

ZiLOG 8-bit MCU frame diagram

Figure 1 ZiLOG 8-bit MCU framework

In this example, the MCU's 10-bit ADC can provide up to four single-ended / differential channels and an optional 1X differential input buffer. In addition, an on-chip low-power operational amplifier is integrated into the ADC module, which eliminates the need for additional external components for high-precision current measurements. Combined with this multi-channel ADC, the MCU's two enhanced 16-bit timer modules with pulse width modulation (PWM) and acquisition and comparison functions can simultaneously operate two loads (ie motors). At the same time, the direct LED drive output can be used in LEDs are triggered when a preset event occurs, no additional hardware is required. The solution also features other features, including an analog comparator, a "fail-safe" oscillator mechanism to ensure reliability, an on-chip integrated temperature sensor, and up to 128B of non-volatile data storage space (NVDS). Figure 2 is a block diagram of a general-purpose motor using ZiLOG MCUs.

General Motor Control System Frame Diagram

Figure 2 General Motor Control System Framework

Main functions of power management motor control

This special digital kilometer management solution provides the main control functions required for general-purpose motors: "soft start", overcurrent fault protection, and the ability to use an on-chip comparator to measure the zero-crossing point of the AC circuit to ensure MCU output signal synchronization. Let's analyze them one by one and see how the program meets these requirements:

(1) Soft start

The "soft start" function ensures that power is gradually output to the motor when the motor is turned on. Adjustable control is achieved by using the MCU's single I / O output to control the trigger / ignition angle of the TRIAC. This function minimizes the overshoot and uneven movement of the rotor during startup, thereby reducing motor wear, preventing sudden changes in demand, and avoiding situations where the electrical circuit has just opened or the running electrical appliances are turned off.

ZiLOG's soft-start implementation uses a timer and a lookup table used when reloading the high and low bytes of the timer. Twenty uniformly distributed trigger angles can be achieved in one half cycle of the AC signal. In this way, you can adjust the TRIAC trigger angle (see Figure 3) to adjust the power delivered to the motor. This soft-start scheme uses a 10 microsecond output pulse width to trigger the TRIAC, during which the trigger angle rises from 18 ° to 162 ° (10% to 90% of a half cycle), at which time the motor transitions to normal full speed operation.

(2) Overcurrent fault protection

Most motor controls require overcurrent fault protection. There are many reasons for overcurrent faults, such as motor winding short circuit, motor lead short circuit, mechanical drive and connection device failure, power device damage, wiring errors, etc. Severe over-current faults can cause damage to the appliance. When an over-current fault occurs, no matter what the reason is, the motor must be stopped immediately to prevent damage. Although the protection circuit must act quickly, it is best to turn off the PWM output on a cycle-by-cycle basis to resume normal operation when failure conditions can no longer be detected, rather than shutting down the entire system at once. If this method does not solve the problem, turn off the system.

This motor controller solution uses a sense resistor to measure the motor current (Figure 2) and transmits the signal to the on-chip integrated ADC. The overcurrent threshold can be set, and once the current reaches this threshold, the system will start an interrupt service routine, then terminate the trigger pulse sent to the TRIAC, and finally shut down the system.

(3) Zero crossing

To control the motor speed, the trigger angle of the TRIAC must be synchronized with the AC circuit voltage, so the zero-crossing moment of this signal must be determined. ZiLOG's motor control solution uses an integrated analog comparator on-chip, eliminating the need for external components, thereby helping to reduce cost and system complexity. Figure 3 shows the different TRIAC firing angles used to implement variable speed control. In the application shown in the figure, the trigger angle of the TRIAC is set to 9 °.

Figure 3 Motor voltage: 18 °, 90 °, and 162 ° TRAC trigger angle

Power management conclusions

Due to cost and system complexity, traditional universal motors used in various home appliances and portable tools generally lack precise motor control. To solve this problem, a digital power management can be used to implement variable speed control to obtain various obvious And prevent electrical surges that can occur when starting electrical appliances that can cause the circuit to open. This solution mentioned above uses ZiLOG's Z8 Encore! XP Flash MCU, which uses integrated digital modules and advanced analog hardware modules to provide a universal motor control solution, which can better overcome obstacles at various prices. Cost and complexity issues of performing intelligent control on sensitive appliances.