Today's medical instrument technologyγ​‌ is developing rapidly. New medical devices are ✔γemerging all the time But≥ > no matter how advanced  ∞and complex the functionality of new deviα£ces is, there is one thing that iε≈s indispensable. That's the power supp₩αly. It is the power source of the energy×↔γ conversion of the entire instrum♠εent, although the principle of vari₹βous devices is different. But the pγ→rinciple of its powe↔÷∞r supply is much the same. And the failure rate o★£§f the power supply is relatively highπ ☆, because the power supply often w≈<orks under harsh envir‌↕λonments. Especially the swi '€↓tching power supply, it bears the impact of high>✔γβ current and high voltage of the whole ma§÷chine. Therefore, in₹$↑÷ the substantial fault of component damage. The €★failure of the power supply accounts for¶↑ a large proportion. Aγ✔ δccording to statistics, it accounts for mor∏α e than 50%. Therefore. As long as you☆≠  are proficient in power supply. In partic£∑'λular, the maintenance of switching power supply¶πφ can be carried out well in the maintenance of ₽♣☆σmedical equipment. The following>♥Ω< focuses on how to respond to c↓ ↔®hange without changin>σg – from the power✔↓ supply to manpower. As a breakthroug‌λ¥h in the face of faults, the switching po☆✘→wer supply to eliminate ​ε>®various complex faults is mainly ✘λcomposed of full-bridge rectifier circuit, start-₽← ‍up circuit, switch exciλ'← tation circuit, voltag φe stabilization control circuit, ou↑™tput rectifier filter circuit and variπ><ous protection circuits. 1 Full-bridge rectifie​♦☆₹r circuit The full-bridge rectifier circuit inp'↔ut is 220 V AC. The output is 300 V DC hiα≥gh voltage. The consum↑™πable part is a full-↓♦∞ bridge rectifier diode. As long as th∏δere is one damage. The en©₹∑tire bridge pile needs to be ✔λΩreplaced. Because the other diodes are de♣&←≤finitely overcurrent. The other is an elβ∞≥♣ectrolytic capacitor with a w<®ithstand voltage of 450 V. Tαλ€ his capacitance capacity is no✘¶→t enough. There will be a lot of special fa ↑ilures. Such as computer system crashes r‍©€♣epeatedly. 50Hz AC interference appear<≈εs on the screen, etc. 2 Starting   circuit self-excited swit¥÷ching power supply f ¶♦≤switch tube plays a switching role.±™± It is also the core element of the gap oscillα≈☆σator of the switching p★↕ower supply), which is c×↕‍omposed of a resistor current limiti$‌↔♥ng method: one end of the resistor i↔ <s connected to a 300 V DC high voltaδ∏♦≤ge. The other end is connected to t™∏'♥he base of the switch t®§•ube. Due to the large value of the star₹§ting resistance (more than 100 koh♣λ<§ms), the power is small. Therefor¥≤<e, it is a wearing part. Afte​ ‌€r the resistor is disconnected. The switc§≈∞hing power supply does not vibrate. Therδ ★e is no venting circuit, and the 300£δ£π V DC high-voltage voltage cannot be vented fo¶λr a long time. Therefore, it is necessary t₹"≈εo pay attention to the↔  discharge of the capaciφφ♣↔tor during maintenance. It ♠&÷excites the switching ★↑♦ power supply (the switch tube of the swit≈& 'ching power supply only plays a swiδ​'tching role. does no→×'♥t participate in the formation of the osci&≤λ↕llation pulse) There are two main wa™§ys: (1) the 300 V voltage is ™§¶Ωpowered to Vee of the integrated circuit af£¶ter resistor current limitλ$‌ ing and step-down: (2) the mains↓• is step-down by the resistor, ♣Ωand the power supply to Vcc after ↑÷the diode is rectified The consumable parts are t♣ε"♠he integrated blocks and →™☆§step-down resistors that participate in the oscil'★lation 3 Switching excitation circuit The ✘↕ ∑self-excited switching power∏♣δ supply is composed of a swit‍↔☆ ching tube, a switching trans₹ ×former, and a positive feedback loop, and the ™≈←‌wearing parts are the capac '♠itors and resistors o↓¥n the positive feedback loop It excitation switc₩αhing power supply is composed of an © oscillator, a logic processor, and an amplifie¥×&★r. This type of circuit is generally co↕↕$☆mposed of integratedβ♥♦ circuits. Even a singleδ↔ thick film manifold is realiz <∏‌ed, and the wearing pa↕↓‍λrt is the switch tube, which is general≤ ly composed of N-channel high-power FET. The →≥method of judging the q¥εuality should be mastered 4 The voltage r₹≤egulation control circuit is div₽®¥≤ided into two types: indirect error§± sampling and direct error sampl∑<&ing circuit according§£ to the error sampling method,β§ and indirect error sampling refers to setting  ∞®a sampling winding on the switch‌‍☆ing transformer. After rectifying th♣ •e filter, a voltage proportional α‌to the output is obtainσ&♣ed. This voltage is us‌γed to control the conduction of the s>$↕∑witch. So as to play a stabilizing ™♥₽effect when overhauling this switching power§™↕& supply. It is necessary to pay attπΩention to the false load to be repaired,↑★ and the wearing parts are filter capa©× ÷citors and potentiometers. The direct error sa↔αmpling circuit refers to the d σ₹γirect sampling of the output voltag¶‍e of the switching power supply, s​↕$o the primary and secondary isolation components•≈✔ of the switching power supply should be added.₽₩'φ Generally it is a photocoupler.✔≤ The wearing part is the optocoupler>×λσ when the component fails. Generally, the ↔'€£output voltage rises s± ÷ignificantly. 5 Voltage output c‌✘ircuit refers to the circuit of the switπλ↓ching transformer secondary filteδ∞$¥red by high-frequency diodes and γλ€capacitors. The wearing parts are various cu≈•✘≤rrent-limiting resistors and fil∞→"ter capacitors 6 Protection circuits Generally, £&>∑there are the following types: (1) spi' ↓§ke pulse absorption circuits, ☆™δ♦which are designed to prevent the breakdown of→↓★ the switch tube; (2) Overvoltage prote↑®♦ction circuit. Prevents t  he output voltage fr✘☆•om rising due to the extended✘< on-time of the switch. On the one hand, the l'¶δ§oad circuit is protected. On₩↓∞↓ the other hand, it also $☆βprotects the switch tube. It shuts×↓↕ off the switch through the base shunt of the ₽®switch. So as to cut off the voltage output of t&♠he switching power supply: (3) un&₽γ♠der-voltage protection circuit and over-curreδ≈Ωnt protection circui∞↕∏φt The fault of the protection circuit is less. H&÷σowever, this part of the circuit should be und₹ Ωerstood, and when some↑  ♣ faults are repaired, this part o✔↓f the circuit needs to be disconnected, oth₹' γerwise the real fault is not easy to be exposed↑★€. 7 Troubleshooting and Troub‍♦÷&leshooting Introducing 4 Troublesλ∞>hooting Examples Our maintenance priεδnciples are. There are →"some general-purpose power suσ♠pplies. In order to in•☆crease the speed of mainten♦Ωance. You can purchase high-quality and lo≤δw-cost power supply replacement on the market.  ε♣Except that the voltage should be consistent. Att'©γention should also be pa$÷id to the current of the load (e.g., f♥∑←ault 1, fault 2); An✔ δd some high-power power supp ≤lies, such as B-ultrasound power supply, bi‌​∑&ochemical instrument power supply, and some ©Ω©$power supply with feedback function. As wΩ¥'✔ell as special voltage power supplies,÷₹✔• which are not easy to buy on the market‍>¶. It needs to be repaired (e.g., ✔λ®fault 3, fault 4).