The steam‑oven control board undertakes the closed‑loop control of heating tube, steam generator and fan. Abnormal conditions such as sensor failure, relay adhesion, water shortage and fan stalling may trigger dangerous operating conditions. Single‑level protection cannot cover all fault scenarios. Reasonable safety‑protection circuit matching for steam‑oven control boards builds hardware‑software coordinated multi‑level protection mechanism including over‑temperature, over‑current and dry‑burning, cuts off dangerous output in time under abnormal conditions, and improves the intrinsic safety of steam‑oven electrical control system. Common safety risks of steam‑oven control circuits include NTC sensor open‑circuit or short‑circuit leading to false temperature feedback; relay contact adhesion causing continuous heating output; sudden water shortage of steam generator resulting in dry‑burning risk; short‑circuit of heating load bringing over‑current impact; fan blockage leading to abnormal heat accumulation inside cavity. If only relying on firmware logic protection, failure will occur once MCU runs away or crashes. Therefore, hardware protection circuit must be used as the bottom‑line guarantee, and software protection serves as the front‑line interlock. The two work independently and verify each other to avoid single‑point failure of protection function. Over‑temperature multi‑level protection circuit design. The first level is software protection based on NTC temperature sampling circuit. The MCU collects real‑time cavity temperature, steam generator temperature, and triggers heating‑stop interlock when exceeding software threshold. Meanwhile, judge the open‑circuit and short‑circuit fault of NTC probe, and immediately lock heating output when sensor abnormality is detected. The second level is hardware independent thermal cutoff circuit. The thermal fuse and temperature limiter are physically arranged near the heating components. Once the temperature rises out of control due to MCU failure or relay adhesion, the hardware thermal protection element will act directly to cut off the main power loop, which does not depend on the operation status of single‑chip microcomputer. The layout of temperature‑sensitive components shall ensure effective thermal coupling with heating source, avoid false action or delayed response caused by thermal isolation. Over‑current and short‑circuit protection matching scheme. Set graded over‑current protection on power input and each load output loop. The main power input is equipped with fuse for total‑loop short‑circuit protection, which can blow rapidly in case of serious short‑circuit. Each high‑power load branch such as heating tube and steam generator is equipped with independent current sampling or PTC resettable fuse. When load current rises abnormally, hardware circuit completes current detection and interlock. The software reads current sampling data, realizes early warning and pre‑shut‑off before reaching hardware action threshold. It is necessary to distinguish instantaneous startup surge current and real fault over‑current, configure reasonable delay filtering to prevent mis‑protection caused by startup impulse. Dry‑burning protection circuit for steam generator. Dry‑burning risk is mainly caused by insufficient water supply, water‑level sensor failure or water‑pump abnormality. Adopt dual‑judgment of water‑level signal and temperature change trend. The water‑level detection circuit feeds back the water storage state of steam generator. When water shortage signal is detected, the system immediately prohibits the heating of steam generator. Meanwhile, assist in judging the temperature rising rate: under normal water‑holding condition, the temperature rise of steam generator is limited by water vaporization; under dry‑burning condition, the temperature rises sharply in a short time. Even if the water‑level circuit fails, the rapid temperature rise can be captured by temperature sampling circuit to trigger protection. Dry‑burning protection shall lock the corresponding heating output and generate fault code, and cannot automatically reset after power‑off and restart without manual troubleshooting. Anti‑adhesion detection of relay output loop. Relay adhesion is a high‑risk hidden danger for steam ovens. Add feedback detection circuit for relay output terminal. After the relay is instructed to turn off, the control board detects whether there is still voltage at the output end. If the output still exists after turn‑off command, it is judged as contact adhesion fault, the main power shall be cut off through hardware interlock, and fault alarm shall be reported. This prevents continuous heating caused by relay sticking when MCU gives turn‑off signal. Hardware‑software interlock and fault handling logic. Hardware protection acts as the final safety bottom‑line, which is irreversible for some critical faults such as thermal fuse blowing. Software protection completes real‑time monitoring, early warning and pre‑interlock. All protection actions shall record fault codes, which can be read for after‑sales troubleshooting. For safety‑related faults such as dry‑burning, serious over‑temperature and relay adhesion, automatic reset is forbidden; the equipment can only resume operation after eliminating hidden dangers. Reasonable anti‑interference design shall be carried out for sampling and detection circuits to avoid protection mis‑triggering caused by power‑supply noise and electromagnetic interference. PCB layout and component selection requirements. Safety‑related components including thermal limiter, fuse and current sampling element shall select kitchen‑appliance‑grade products with sufficient derating margin. Safety circuits shall keep away from noise sources such as high‑power relays to reduce interference. Protection signal traces shall be reasonably routed to avoid virtual soldering. The key safety circuits shall not share traces with ordinary signal loops to prevent mutual interference. After PCB revision or component replacement, re‑verify the whole protection function. Simulated fault verification test. Conduct targeted fault injection test for each protection item: simulate NTC open‑circuit/short‑circuit, relay adhesion, water shortage dry‑burning, load short‑circuit, fan stall and other conditions, verify whether each protection link can be triggered accurately, check the response time and fault locking logic. Eliminate missing protection and mis‑triggering risks. It is not allowed to rely only on software logic to cover safety‑related fault conditions. Through coordinated matching of over‑temperature dual‑protection, graded over‑current protection, dry‑burning dual‑judgment mechanism and relay adhesion detection, the steam‑oven control‑board forms multi‑level safety‑protection capability. The hardware bottom‑line protection and software monitoring complement each other, effectively cope with various abnormal working conditions, and satisfy the electrical safety requirements of household and commercial steam oven products.