Implementation of a programmable high-efficiency energy-saving power supply for intelligent access control

      As the name implies, the entrance access control system is a system for controlling the entrance and exit channels. It is developed on the basis of traditional door locks. Traditional mechanical door locks are just simple mechanical devices. No matter how reasonable the structural design is or how strong the material is, people can always open it by various means. In channels with many people in and out (such as offices and hotel rooms), key management is very troublesome. If the key is lost or the personnel are replaced, the lock and the key must be replaced together. In order to solve these problems, electronic magnetic card locks and electronic password locks have appeared. The emergence of these two locks has improved people's management of entrance and exit channels to a certain extent, and channel management has entered the electronic age. However, with the continuous application of these two electronic locks, their own defects have gradually been exposed. The problem with magnetic card locks is that information is easy to copy, there is a lot of wear between the card and the card reader, the failure rate is high, and the safety factor is low. The problem with password locks is that the password is easy to leak and there is no way to check it, so the safety factor is very low. At the same time, since most of the products of this period use the card reader part (password input) and the control part installed outside the door, it is easy for people to open the lock outdoors. The access control system during this period was still in its early and immature stage, so the access control system at that time was usually called an electronic lock and was not widely used.

　　This paper proposes a power circuit model that uses the host to participate in power supply management, so that the smart access control can automatically enter sleep mode and has high efficiency and energy saving. The model is characterized by the integration of "power supply and host", which enables the system power consumption to be fully controlled by software, and can achieve substantial high efficiency and energy saving effects in actual use. The research content of the model includes the power supply mechanism started by the user key, the host replaces the user key to maintain the system power supply and the host timed power off method, and the system partition power supply mechanism controlled by software. Practical results show that the smart access control powered by this model meets the daily access control power supply requirements of people, has significant energy saving effects, and is safe and reliable.

　　1 Logical Model

　　Figure 1 shows the logic model of the intelligent access control power supply that can automatically put the system into sleep mode and provide power supply in different time zones and regions. The power supply sequence is divided into three levels:

　　(I) is the grid voltage conversion stage, which consists of a dual-circuit transformer, main and auxiliary power supply rectification, filtering and other links;

　　(2) It is the power supply level for the host and power components, and is composed of a key-start power supply circuit, a power switch, a program-controlled circuit, and a voltage-stabilizing circuit;

　　(3) Time-sharing and zone-sharing power supply stage, which is composed of multiple power electronic switches, voltage stabilizing circuits and control circuits.

Figure 1 Power supply logic model

　　1.1 Key-start power supply mechanism

　　The switching power supply module is a new generation of switching power supply products developed in modern electronic technology. It is mainly used in many fields such as civil, industrial and military, including switching equipment, access equipment, mobile communications, microwave communications, optical transmission, routers and other communications fields, as well as automotive electronics, aerospace, etc. Since the use of modules to build power supply systems has the characteristics of short design cycle, high reliability, and easy system upgrade, the application of module power supplies is becoming more and more extensive. Especially in recent years, due to the rapid development of data services and the continuous promotion of distributed power supply systems, the growth rate of module power supplies has exceeded that of primary power supplies. With the extensive use of semiconductor processes, packaging technologies and high-frequency soft switches, the power density of module power supplies is getting larger and larger, the conversion efficiency is getting higher and higher, and the application is becoming simpler and simpler. With the continuous increase in industrial investment, market demand is gradually rising.

　　The "key" here is broad in meaning and can be any characteristic information carrier that can be used for intelligent access control unlocking. The key start power supply circuit is powered by the auxiliary power supply. Because the action time is short and the quality requirement is not high, it is directly taken from the filter output of the auxiliary power supply. When the key acts on the key start power supply circuit, its output turns on the high-power electronic switch through the diode D1, and the main power supply is filtered and output, and then the host is powered after being stabilized by the host power supply voltage stabilization circuit. Figure 1 Power supply logic diagram.

　　1.2 Power supply control vector

　　As shown in Figure 1, after the key starts the power supply, the power supply of the entire system is controlled by the power supply control vector (remember PowerCON). The power supply control vector occupies a 1-byte wide port of the host. POWERCON-D7 controls the anode voltage of diode D2; POWERCON·D6 controls the power supply electronic switch; the other 6 bits are used for time-sharing and partitioned power supply control.

　　1.3 Host power supply automatic control mechanism

　　When the key turns on the host power, the first instruction executed by the host is to add a positive voltage to the anode of D2 through the power port, thereby replacing the power supply control function of the key, that is, when the key leaves the power-on position or fails to keep the anode of D1 at a high level, the control signal of the host power is provided by the power port. When the user does not operate the system for a certain period of time, the system should automatically enter a dormant state. To achieve this function, the host must set a timer interrupt source. The timer It~lhl is set in the initial process after the host takes over the power control. The user does not operate the system refers to the two situations where the user does not use the key or does not operate the system through the keyboard. Let the host continuous operation time be T, KK is the flag whether the system is operated by the user within T, that is, KK=1 means that the user operates the system within T, otherwise KK=0. KK is assigned in the keyboard scanning subroutine of the system. Taking RT as the timing counter, the algorithm for realizing the host self-power-off is as follows:

　　1.4 Time-sharing and zone-based power supply mechanism

　　Some external circuits, components, and equipment do not have to use electricity synchronously with the host, nor do they need to maintain the same power consumption time as the host. For example, in a system that uses image recognition information as a key, the image sampling power consumption is relatively large, but it generally only appears at the sampling time. It is not necessary to let it be powered in the same way as the host. The method of when to enable and when to power should be used to control the use of power; similarly, on the host circuit board, power can also be divided into blocks according to circuit functions. For example, some uncommon interfaces are integrated into a circuit module. When necessary, the host first powers it by operating the power port, and then performs the corresponding port operation. The lower 6 bits of POWERCON are used to realize the time-sharing and partitioned power supply function. Each bit corresponds to a power electronic switch, and the 6NI" shares a voltage regulator. When practical, it should be noted whether the total power of the 6 channels is within the load of the voltage regulator. When the load is not a problem, the host can change the value of the lower 6 bits of POWERCON to realize the time-sharing and partitioned power supply of the relevant parts of the system. The life of a device is related to its power consumption time. Time-sharing and partitioned power supply can reduce the power consumption time of some devices, thus helping to extend the life of the device.

         2 Practical Circuit

　　FIG2 shows the main power supply and time-sharing and partitioning power supply of the actual circuit diagram of the system power supply. The power supply circuit is relatively simple and is not drawn. The key is an image, and the photoelectric sensor detects the operation of the image card. When the image card changes the state of the photoelectric coupling signal, the key start circuit outputs a high potential, and the transistor T2 (903 1) is turned on through two diodes, thereby turning on T1 (T1 P127). Here, T1 and T2 constitute the main power switch. The filtered voltage output by T1 is stepped down by four diodes (1N4001) to meet the input voltage requirements of the voltage regulator tubes W1 and W2 (LM323K). W1 provides the main power supply, and W2 provides the time-sharing and partitioning power supply. The main system uses 89C51 as the core device, and uses the inherent parallel interface PI of 89C51 to program and control the power supply. P1.o/11 is used to take over the key control. P1.1 controls the power supply of the power supply (not drawn). P1.2 controls the sampling power supply, power switch T3, 9013 is selected according to the current load during sampling. P1.3 controls the port power supply, power switch T4, 9013 is also selected according to the current load when the terminal VI circuit module is working. The first instruction executed by 89C5I is SETB PI.0; when the system works continuously for T, 89C51 executes CLR P1.0 instruction in the time interrupt service program, making P 1.0=0, and T2 is cut off through two diodes (IN4001), and then TI is cut off, and the system automatically powers off. K is a manual control switch. When K is closed during system debugging, T1 is not controlled by the key and P1.0, while P1.2 and P1.3 work normally.

Figure 2 Programmable power supply example

　　3 Substantial energy-saving measures

　　Energy saving of electrical equipment refers to reducing electricity consumption while meeting the same function. Common energy saving methods for electronic equipment include device energy saving method, that is, changing high-energy-consuming components to low-energy-consuming components, such as CMOS chips and HMOS chips for single-chip microcomputers; AC conduction angle control method, that is, reducing useless output by controlling the power supply share within a cycle. In addition to using common energy saving methods, the scheme in Figure 1 is more importantly combined with the characteristics of access control, and uses the host to achieve substantial energy saving from three aspects.

　　3.1 Hibernation Energy Saving

　　In daily life, the time of operating the access control is very short, and most of the time, the access control does not need to be paid attention to. During the long period of non-operation, the scheme in Figure 1 automatically stops powering the system and puts the system into a dormant state. The system powered by the circuit in Figure 2 has been tested by the Hunan Provincial Electronic Product Testing and Analysis Institute. The maximum power consumption in the unlocked state is less than 40W, and the power consumption in the dormant state is less than 30roW.

　　3.2 Targeted Action

　　Program-controlled time-sharing and zone-based power supply further improves the power efficiency of the system. The selection of power supply equipment can be made through the system keyboard, program logic decision, or other specific methods. Power consumption under program control is mainly for a special function, a specific time period, etc. When a circuit module or device with a special function is started, the power consumption time must be less than T. This is one of the substantial energy-saving methods brought about by the host participating in power control when the system is awake.

　　3.3 Power supply on demand

　　The power supply is generally higher in voltage than the host power supply, and is mainly used to drive the lock tongue drive components such as electromagnetic, micro stepper motors and micro DC motors. As shown in Figure 1, when the power supply is not needed, the host generates the power supply electronic switch control signal. When the system needs to drive the lock tongue, the host opens the corresponding power electronic switch according to the power port address instruction, and then the power supply is JlnN to the lock tongue drive component, and then the host runs the lock tongue driver. Different drive components have different drivers, which leads to different power consumption methods. The power supply under the control of the host software enters the power-consuming device only when the system needs to drive the lock tongue. When the lock tongue does not need to be driven, the lock tongue drive component has almost no power consumption.

　　4 Conclusion

　　According to the actual use of access control in daily life, establishing a practical power consumption mechanism for smart access control is an unavoidable reality problem in the study of smart access control. Starting from practicality, this paper establishes an integrated working mechanism of "power supply-host", which solves the following two problems: (I) all-round software control of power consumption of smart access control system; (2) substantial and efficient energy saving.

　　The "power supply-host" integrated working mechanism further improves the intelligence of the smart access control system, helps to extend the life of the system, and lays a solid foundation for achieving the ideal goal of 0 failures during the rated life. This model has been applied in the above system and achieved good results. The "power supply-host" integrated working mode can also be used for reference in other systems that require host self-controlled power supply and systems that require time-sharing and zone-sharing power supply.