Quick wins for a faster PC:
Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Some links on this page are affiliate links: if you buy through them we may earn a commission, at no extra cost to you.
TOP224YN is a three-terminal, offline PWM switch from Power Integrations’ legacy TOPSwitch-II family. It combines a high-voltage MOSFET, PWM controller, startup circuitry, feedback control, current limiting, auto-restart, and thermal protection in a through-hole TO-220-3 package. The datasheet’s practical output figures are up to 75 W for 100/115/230 VAC ±15% input arrangements and 45 W for 85–265 VAC universal input, subject to transformer, thermal, clamp, and construction conditions. Power Integrations lists it as active but not recommended for new designs.
View the official TOP224YN product page and use the family datasheet before designing or replacing a mains-connected supply.
What is TOP224YN?
TOP224YN is an integrated offline AC/DC switching device, not a conventional low-voltage DC/DC regulator. It is designed for circuits that switch rectified mains voltage, most commonly an isolated flyback power supply.
Free tools Windows power users keep installed
One-click scans. No signup required.
The device integrates functions that would otherwise require several discrete components:
#1 Best Overall
- TOP225YN SWITCH POWER IC
- High-voltage power MOSFET
- Voltage-mode PWM controller
- High-voltage startup and bias circuitry
- Control-pin shunt regulation and error-amplifier functions
- Current-limit sensing using MOSFET on-resistance
- Leading-edge blanking
- Shutdown and auto-restart
- Overtemperature protection
Distributor classifications also list boost, buck, flyback, and forward applications. In practical legacy designs, however, TOP224YN is most strongly associated with isolated offline flyback converters for auxiliary supplies, appliances, monitors, audio equipment, and industrial controls.
The IC itself does not guarantee an isolated output. Isolation depends on the complete design: transformer construction, insulation system, PCB creepage and clearance, feedback method, enclosure, and safety components.
Power Integrations product information | TOPSwitch-II family datasheet
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
TOP224YN key specifications
| Parameter | TOP224YN |
|---|---|
| Family | TOPSwitch-II |
| Function | Three-terminal offline PWM switch |
| Package | TO-220-3, through-hole |
| Pins | CONTROL, DRAIN, SOURCE |
| Nominal switching frequency | 100 kHz |
| Drain breakdown rating | 700 V absolute maximum |
| Maximum practical output rating | 75 W at 100/115/230 VAC ±15%; 45 W at 85–265 VAC |
| Listed junction-temperature range | Approximately −40°C to +150°C; continuous design operation requires thermal analysis |
| Protection | Cycle-by-cycle current limit, leading-edge blanking, auto-restart, and thermal shutdown |
| Lifecycle guidance | Active listing, but not recommended for new designs |
These figures describe the device and the conditions used for the family’s power table. They are not a universal guarantee that any TOP224YN circuit will deliver the stated wattage continuously.
TOP224YN part-number meaning
The TOP224 number identifies the device’s power class within the TOPSwitch-II range. In the Y package, TOP224Y is rated above TOP221Y–TOP223Y and below TOP225Y–TOP227Y.
| Device | 100/115/230 VAC ±15% | 85–265 VAC universal input |
|---|---|---|
| TOP221Y | 12 W | 7 W |
| TOP222Y | 25 W | 15 W |
| TOP223Y | 50 W | 30 W |
| TOP224Y | 75 W | 45 W |
| TOP225Y | 100 W | 60 W |
| TOP226Y | 125 W | 75 W |
| TOP227Y | 150 W | 90 W |
The Y designation refers to the TO-220/3 package family. The N suffix is the ordering and production designation used for the specific TOP224YN version sold by distributors. Do not assume that every TOP224 suffix has the same footprint. TOP224GN, for example, is an eight-pin surface-mount variant with a different physical arrangement and pinout.
TOP224YN pinout and tab connection
| Pin | Function |
|---|---|
| 1 | CONTROL |
| 2 | DRAIN |
| 3 | SOURCE |
The package tab is internally connected to SOURCE. This is important when mounting the part to a heatsink: an uninsulated heatsink attached to the tab is electrically connected to the primary-side source node. Use an appropriately rated insulating mounting kit where required, and maintain the necessary creepage and clearance.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsThe P and G package variants expose duplicated source and high-voltage-return connections through eight pins. Their pinouts must not be mapped directly onto the three-pin Y/YN package.
Output-power ratings explained
The headline figures are:
- 75 W for 100/115/230 VAC ±15% single-voltage input arrangements.
- 45 W for 85–265 VAC universal input arrangements.
Therefore, a design described simply as a “75 W TOP224YN supply” may be misleading if it is expected to operate across the full universal-input range. Low-line operation, transformer flux, peak current, duty cycle, rectifier arrangement, clamp losses, ambient temperature, copper area, airflow, and enclosure temperature all affect the usable output.
Rank #2
- TOP257YN SWITCH POWER IC
The datasheet power table assumes suitable thermal management and a specified implementation. Treat the figures as design targets to validate, not as plug-and-play ratings. A practical design review should calculate conduction and switching losses, estimate junction temperature, and verify operation at low line, high line, maximum load, startup, shutdown, and abnormal load.
What the 700 V rating means
The DRAIN absolute-maximum range is listed as approximately −0.3 V to 700 V. This is a semiconductor stress limit, not a recommended continuous drain operating voltage.
Recommended Free Tools
In a flyback converter, transformer leakage inductance produces a voltage spike when the MOSFET turns off. The primary clamp—often an RCD or equivalent network—must control that spike and its ringing. The design must also account for line surges, switching transients, transformer tolerances, and safety requirements. A drain waveform that approaches the absolute maximum leaves little margin for production variation or abnormal conditions.
Drain measurements are hazardous. Use a suitably rated differential probe or an appropriately isolated measurement setup. A grounded oscilloscope probe can short a primary-side switching node or create a serious shock hazard.
How TOP224YN operates
Startup and bias
The integrated high-voltage startup circuit obtains initial operating power from the drain-side supply. Once the converter begins switching, the auxiliary bias winding normally supplies the control circuitry more efficiently. The exact startup and bias network must follow the family datasheet and the transformer design.
CONTROL-pin feedback
The CONTROL pin is both a control input and a supply node for the internal circuitry. It behaves as a shunt-regulated control node and acts as a current-to-duty-cycle converter: as CONTROL-pin current increases, switching duty cycle decreases.
In a typical isolated flyback:
- The secondary-side output is sensed with a reference and error amplifier.
- An optocoupler transfers the error signal across the isolation barrier.
- The optocoupler injects current into the primary CONTROL pin.
- TOP224YN adjusts duty cycle and peak current to regulate the output.
Current limiting and blanking
The device uses the MOSFET’s on-state drain-source voltage as a proxy for drain current. When the current-limit comparator detects excessive current, the MOSFET is turned off for that cycle. Leading-edge blanking prevents the short current spike at turn-on—including effects from rectifier recovery and circuit capacitance—from causing premature current limiting.
Auto-restart and thermal protection
Persistent loss of regulation or another fault can place the device into auto-restart. The datasheet describes this as a low-duty-cycle mode intended to limit dissipation during faults, with a typical auto-restart duty cycle of about 5%.
Thermal shutdown is typically described around 135°C. That is a typical protection threshold, not a substitute for the guaranteed electrical characteristics or a thermal design target. Distributor listings may show a junction-temperature range extending to approximately +150°C, but continuous operation near that limit should not be assumed to be acceptable.
Rank #3
- Controllers
- Programmable Controller With Built-in Power Supply For 24-point And 40-point Industrial Controllers
Typical applications
TOP224YN is suitable for evaluating or maintaining legacy offline supplies such as:
The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →- Isolated auxiliary power supplies
- Appliance control supplies
- Industrial control equipment
- Older monitors and audio equipment
- Low-to-moderate-power consumer electronics
These are application categories, not a guarantee that every design is appropriate. The transformer, input range, output requirements, thermal environment, EMI design, and safety construction must all be validated.
How to select a replacement
The safest replacement for a failed device is normally a verified, genuine TOP224YN with the same package and marking. A replacement part must be checked across four areas:
Electrical compatibility
- Drain-voltage rating and transient margin
- Peak current limit
- Switching frequency
- Duty-cycle range
- CONTROL-pin thresholds and current requirements
- Startup current and bias behavior
- Auto-restart and thermal-protection behavior
Mechanical compatibility
- Package and lead spacing
- Pin order
- Body dimensions
- Tab connection
- Heatsink and insulation arrangement
Magnetic compatibility
The transformer must be compatible with the replacement device’s peak current, switching behavior, duty-cycle limits, reset conditions, primary inductance, and flux-density limits. A similar part number does not prove that the existing transformer will remain suitable.
Safety and compliance
Recheck EMI, conducted emissions, surge performance, creepage, clearance, reinforced insulation, thermal behavior, and abnormal operating conditions. A substitute that starts and regulates on the bench may still fail compliance or reliability testing.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallIs TOP244YN a drop-in replacement?
No—not automatically. DigiKey lists TOP244YN as a similar part, but it is shown in a different TO-220-7C package. It therefore requires a separate pinout, footprint, transformer, control-loop, thermal, and safety review. “Similar substitute” on a distributor page does not mean drop-in compatible.
The same warning applies to TOP224GN and TOP224PN. They belong to related TOPSwitch families but use different packages and pin arrangements. Confirm the full ordering code before fitting a replacement.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshooting a failed TOP224YN
A failed TOP224YN is often a symptom of another fault. Before installing a new device, inspect the complete converter:
- Disconnect power and discharge capacitors safely. The primary bulk capacitor can retain hazardous voltage.
- Check the fuse, input rectifier, surge limiter, and bulk capacitor. Look for shorts, open parts, cracking, and signs of surge damage.
- Inspect the primary clamp and snubber. A failed resistor, diode, or capacitor can cause destructive drain spikes.
- Test the transformer. Check winding continuity, insulation, primary inductance, and visible damage.
- Check the CONTROL-pin capacitor and surrounding components. A shorted, leaky, or dried-out capacitor can prevent startup or overstress the replacement.
- Inspect the auxiliary bias winding and startup path. An open bias component can cause repeated startup attempts.
- Check the optocoupler and secondary reference. Feedback failure can drive abnormal duty-cycle or protection behavior.
- Test secondary rectifiers, output capacitors, and the load. A shorted rectifier or output load can destroy a new switch immediately.
- Inspect solder joints and thermal mounting. Cracks around the TO-220 leads or tab can create intermittent or overheating faults.
- Power up with appropriate current limiting and measurement equipment. Verify drain voltage, startup behavior, output regulation, and fault response.
Do not repeatedly install replacement ICs without finding the original failure mechanism.
Rank #4
- Universal input voltage: 85-264V AC or 110-370V DC The product is easy to install, can be used directly on the motherboard board.
- High efficiency, high power density, low output ripple noise, high output voltage accuracy.
- Input and output are highly isolated.
- Four corners have a fixed mounting hole to prevent movement 1 vibration lead to productpower, fixed hole straight by 3.2mm.
Availability and buying guidance
TOP224YN may still be obtainable through authorized distribution, but availability does not change its lifecycle guidance. Power Integrations lists the part as active while also stating that it is not recommended for new designs. Separate current buyability from long-term product support and design suitability.
Distributor stock, prices, lead times, tariffs, and regional availability change. On the cited distributor pages, DigiKey showed stock and price breaks during an August 17, 2026 check, while Mouser showed no immediate stock but incoming quantities and a factory lead-time indication during an August 18, 2026 check. These are date-stamped signals, not permanent purchasing facts.
For repair or approved legacy production:
- Prefer authorized distribution and traceable packaging.
- Verify the complete TOP224YN marking and TO-220-3 package.
- Compare lot information and packaging against the distributor listing.
- Account for regional taxes, tariffs, shipping, and quantity breaks.
- Avoid unverified broker stock solely because it is cheaper.
DigiKey TOP224YN listing | Mouser TOP224YN listing
Should a new design use TOP224YN?
Generally, no. For a new product, evaluate a current offline-switcher family with present-day efficiency, standby-power, EMI, safety, lifecycle, and documentation requirements. Power Integrations families such as TinySwitch-5, InnoSwitch5-Pro, InnoSwitch4-Pro, InnoSwitch3-AQ, and InnoSwitch3-TN may be evaluation paths, but none should be treated as a pin-compatible TOP224YN replacement without a complete redesign.
A newer device may require a different transformer, feedback arrangement, PCB layout, thermal solution, EMI filter, and certification work. Conversely, TOP224YN can still be reasonable for an existing board, validated transformer, approved product, or short maintenance run where redesign costs and qualification risks outweigh the benefits.
Design-review checklist
- Confirm the exact TOP224YN package and marking.
- Determine whether the input is single-voltage or 85–265 VAC universal.
- Compare continuous and peak output power against the correct 75 W or 45 W design condition.
- Verify transformer turns ratio, inductance, peak current, reset, insulation, and construction.
- Measure or calculate drain-voltage margin under all relevant operating conditions.
- Validate the primary clamp and surge protection.
- Calculate losses and confirm case and junction temperatures.
- Verify CONTROL-pin capacitor, optocoupler, feedback, and bias components.
- Check creepage, clearance, fusing, discharge, Y capacitors, and insulation.
- Test short circuit, overload, open feedback, brownout, startup, shutdown, and overtemperature behavior.
- Only then approve a substitute or modern redesign.
Frequently Asked Questions
Can TOP224YN deliver 75 W from universal input?
Not according to the family power table. The listed practical figure is 75 W for 100/115/230 VAC ±15% arrangements and 45 W for 85–265 VAC universal input, subject to the datasheet’s thermal and construction conditions.
Does the TOP224YN tab connect to drain?
No. The TO-220-3 tab is internally connected to SOURCE. Heatsink insulation and primary-side clearance must be designed accordingly.
Is TOP224YN obsolete?
Power Integrations lists it as an active product but says it is not recommended for new designs. It remains relevant for repairs and validated legacy equipment, but current designs should evaluate newer families.
Can TOP224YN be used in a non-isolated supply?
The device can support more than one converter topology, but isolation is a property of the complete power supply. A non-isolated design still requires appropriate topology, safety, grounding, and enclosure analysis.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
