Smart Home Circuit Protection Solution Design Ideas
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First of all, we all know that power is used to convert electrical energy from one form to another so that the device can operate correctly. Common power supply examples include: AC-to-DC converters that convert AC voltages to stable DC voltages; DC-to-DC converters that convert battery power to a desired voltage level. Among them, the power supply of the smart home mainly supplies power for the main control circuit, the signal isolation, and the display circuit. The power scheme adds surge protection circuitry at the input port to ensure the reliability and stability of the power circuit operation.
The coordination between industries and the harmonization of standards are still not mature enough. This requires that only the home systems consider the security features of products more. In addition, the installation and wiring of smart homes may be one-time, so the system is ideally high-end. Reliability, timely protection against lightning surges, grid overvoltage, and static electricity that may occur during application. In practical applications, the power supply interface and signal interface of the smart home system are vulnerable to over-voltage and over-current faults such as lightning surges, grid voltage fluctuations, static and aging short circuits, and wiring errors, resulting in system failure or damage. In order to improve the security and reliability of the system, it is necessary to consider adequate protection of its corresponding interface during design.
After understanding the protection points, it is necessary to understand the circuit protection components used in the surge protection circuit. The circuit protection devices used for power protection include the lightning-restricting ceramic discharge tube and TVS diode of SOCAY. , varistors, and over-current protection devices PTC resettable fuses, including ceramic discharge tube, TVS diodes and varistors are overvoltage devices, the following is the selection of points:
Overvoltage protection device selection should pay attention to the following four points:
1) Selection of off voltage Vrwm. The general shutdown voltage must be at least 10% higher than the maximum operating voltage of the line;
2) Selection of clamping voltage VC. VC refers to the voltage across the TVS in the ESD strike state, which must be less than the maximum transient voltage that can be protected by the circuit being protected;
3) Selection of surge power Pppm. Different power, different protection time, such as 600w (10/1000μs); 300W (8/20μs);
4) Selection of inter-electrode capacitance. The higher the operating frequency of the protected components, the smaller the capacitance of the TVS.
Of particular concern is the selection of TVS diodes. Because TVS diodes are unidirectional and bidirectional, engineers must choose whether to use bidirectional or unidirectional TVS depending on the application interface. The DC power interface generally uses a unidirectional TVS; the AC power interface and the communication interface generally use bidirectional TVS.
PTC resettable fuse selection points:
1. Keep the current slightly larger than the user's normal operating current.
2. Vmax must be greater than or equal to the user's maximum operating voltage.
3. Imax must be greater than the maximum fault short-circuit current.
SOCAY Shukai circuit protection components provide protection against short circuit and overload conditions. They have a wide range of choices in form factors, current ratings, voltage ratings, current interruption capacity, and mounting options, giving design engineers flexibility in design.
Metal oxide varistors (MOVs) on the entire power input provide overvoltage clamping protection. They are cost-effective and minimize the transient energy that can be passed into downstream electronics. The selection of metal oxide varistors is based on a series of parameters including nominal voltage, peak pulse current, device size, and wire configuration.
MOVs and fuses need to form a coordinated solution so that the energy required to blow the fuse element (also called the "i2t" value) is high enough to allow the MOV to operate without the fuse under surge voltage conditions. Trip. In other words, the fuse should not be opened under the condition that the surge energy is clamped and dissipated. It should only trip in the event of an overload or short circuit condition.
Even with varistors in the AC input, there are instances where the circuit is not immune to surge events. In these cases, a TVS diode can be added to the input circuit of the inverter pole. This TVS diode provides secondary protection against transients. The power "passed" from the varistor will be further reduced by this TVS diode to a level that will not defeat the circuit.
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