Products highlight lowest cost, low power switching solutions Lower cost than RCC, discrete PWM and other integrated/hybrid solutions Cost effective replacement of bulky linear adapters Lowest component count Simple on/off control – No Loop Compensation No Bias Winding – Simpler, Lower Cost Transformer Allows SIMs Up to 2 W from Universal Input or up to 4 W from 115 VAC Input PLE RC Type EMI Filter Very Energy Efficient at 115/230 VAC Consumes only 30/60 MW at no load at voltage Meets Blue Angel, Energy Star, Energy 2000 and 200 MW European cell phone standby needs Saves $1 to $4 per year in energy costs compared to bulky linear adapters ($0.12/year kWh) Ideal for cell phone chargers, backup power for PCs, TVs and VCRs, electricity meters and cordless phones.
High-Performance, Low-Cost High-Voltage Power Delivery – Ideal for Charger Applications Very High Loop Bandwidth Provides Excellent Transient Response and Fast Turn-On with Little Overshoot Limiting and Thermal Protection Section 44 kHz Operation ( TNY253 /4) with Clamp Clamp to Reduce EMI and Video Noise in TVs and VCRs Use Optocouplers or Bias Winding Feedback Operating Instructions

The Tinyswitch family features a breakthrough design to provide the lowest cost, high efficiency offline switching solution in the 0 to 10W range. These devices integrate 700V power MOSFETs, oscillators, high voltage switched current sources, current limit and thermal shutdown circuitry. They start and run with power derived from the drain voltage. e, eliminates the need for transformer bias windings and associated circuitry. However, they only consume about 80 mW from the 265 VAC input to no load. A simple on/off control scheme also eliminates the need for loop compensation.

The TNY253 and TNY254 switch at 44 kHz to minimize EMI and allow a simple snubber clamp to limit drain spikes.
Voltage. At the same time, they allow the use of low-cost EE16 core transformers to supply currents up to 5 W. The TNY253 is the same as the TNY254 except that its lower current limit reduces the output short-circuit current for applications below 2.5 W. Using switching rates up to 130 kHz, the TNY255 delivers up to 10 W to A from the same low-cost EE16 core. PC backup power and other applications. EE13 or EF13 cores with safety spaced spools can be used for applications up to 2.5 W. When using three-core insulated wire for the secondary winding, there is no bias winding and no tape/edge is required in most applications.
This simplifies the transformer structure and reduces the cost

Pin function description (D): The channel pin connection of the power MOSFET. Start-up and steady-state operation are provided with two internal operating currents.
BYPASS PIN (BP): Connect an external bypass capacitor to the internally generated 5.8 V power supply bypass pin. The ice tank is used to source two external circuits that supply current.
(a) ENABLE pin: The power MOSFET switch can be pulled low as the terminal pin, which urban the IV characteristic of the two (Ice equivalent pin voltage source (about 1.5 V with a source current clamp) Source(s): Power MOSFET source Pin connections. Main return.
II Functional Description
TinySwitch ice is used for low power offline applications. It combines a high voltage power MOSFET switching power supply controller and one in one device. Unlike a traditional PWM (Pulse Width Modulation) controller, TinySwitch discerns the output voltage of two tunes with a simple on/off control.
The TinySwitch controller consists of an oscillator, enabling (listening and logic) circuits, and a 5.8 V voltage regulator circuit;
hysteretic overtemperature protection, current limiting circuitry, blanking leading edge, and a 700 V power MOSFET. Figure 2 shows a functional block diagram with the most important features.
The oscillator oscillates on the ice at a frequency of 44 kHz internally (130 kHz for the tny255). "The two signals of interest are the periodic signal of the highest call of duty (DMAX), divided by typically 67% of the duty cycle and the clock signal, which indicates of each cycle that begins with a skipped cycle. (see below), "Frequency Oscillator dual card value I have been y255 130 kHz). This will increase the sample rate as the "ENABLE pin is the loop response.
The circuit that enables (listening and logic to the ENABLE pin has an input source follower polarized on an input current of 1.5 V A city clamped ice flow source on a 50µA with 10µA hysteresis. The meaning of the enable output

The circuit is sampled on the rising edge of the oscillator clock signal (at the beginning of each cycle). If it is high, turn on the power MOSFET (enable) for that cycle, otherwise the power MOSFET is still off (skip the cycle). Since only one sample is taken at the beginning of each cycle, enabling pins during the cycle will be ignored.
5.8 V regulator The 5.8 V regulator charges the bypass capacitor connected to the bypass pin to 5.8 V by drawing current from the voltage on the drain when the MOSFET is off. The bypass pin is the Tinyswitch's internal supply voltage node. When the MOSFET is turned on, the Tinyswitch will deplete the energy stored in the bypass capacitor. The extremely low power consumption of the internal circuitry allows the Tinyswitch to operate continuously from the current from the drain pin. A bypass capacitor value of 0.1 microF is sufficient for high frequency decoupling and energy storage.
Brown-out: The brown-out circuit disables the power MOSFET when the bypass pin voltage drops below 5.1 V. Once the bypass pin voltage drops below 5.1 V, it must rise back to 5.8 V to enable (turn on) the power MOSFET.
A hysteretic overtemperature protection thermal shutdown circuit senses the die connector temperature. The threshold is set to 135°C with a hysteresis of 70°C. When the junction temperature is above this threshold (135°C) the power MOSFET is disabled and remains disabled until the die junction temperature drops by 70°C, at which point it is re-enabled.
Current Limit The current limit circuit senses the current in the power MOSFET. When this current exceeds an internal threshold (ilimit), the power MOSFET will be turned off for the remainder of the cycle.
The leading edge blanking circuit suppresses the current limit comparator for a short time (TLeb) after the power MOSFET is turned on. This leading edge blanking time is set so that current spikes caused by the primary side capacitance and the secondary side rectifier reverse recovery time do not cause premature termination of the switching pulses.
tSwitch operation
Tinyswitch is used to work in current limit mode. When enabled, the oscillator turns on the power MOSFET at the beginning of each cycle. Turn off the MOSFET when the current rises to the current limit. The oscillator limits the maximum on-time of the MOSFET to DCmax. Because the current limit for a given Tin and the frequency of the Y switching device are constant, the output power is proportional to the primary inductance of the transformer and is relatively independent of the input voltage. Therefore, the design of the power supply includes calculating the primary inductance of the transformer to obtain the maximum power required. As long as the selected switching device is power rated. At the lowest input voltage, the calculated inductance will allow the current to rise to the current limit before reaching the DCmax limit. The enable function Tinyswitch senses the enable pin to determine whether to continue with the next switching cycle described earlier. Once a loop is started, Tinyswitch always completes the loop (even if the enable pin changes state halfway through the loop). This operation causes the output voltage ripple of the power supply to be det. Limited by the output capacitor, the energy per switching cycle and the delay in enabling feedback.
The enable signal is generated on the secondary circuit by comparing the power supply output voltage with the reference voltage. When the power supply output voltage is less than the reference voltage, the enable signal is high.
In a typical implementation, the enable pin is driven by an optocoupler. The collector of the optocoupler transistor is connected to the enable pin and the emitter is connected to the source pin. The optocoupler LED is connected in series with the Zener to pass the DC output voltage to be regulated. When the output voltage exceeds the target regulator. At the operating voltage level (the optocoupler diode voltage drop plus the zener voltage), the optocoupler diode will start conducting, pulling the enable pin low. The Zener can be replaced with a TL431 device for improved accuracy.
The enable pin pull-down current threshold is nominally
50 microamps, but set to 40 microamps the moment the threshold is exceeded. When the enable pull-down current falls below the current threshold of 40µA, it will reset to 50µA.
The on/off control Tinyswitch's internal clock is always running. At the beginning of each clock cycle, the Tinyswitch pair enables the pin to decide whether to perform a switching cycle. If the enable pin is high (<40µA), a switching cycle will occur. If the enable pin is low (greater than
50 microamps), no switching cycle occurs and the enable pin state is sampled again at the beginning of the subsequent clock cycle.
At full load, the Tinyswitch will do most of its clock cycles. At loads below full load, the Tinyswitch will "skip" more cycles to maintain voltage regulation on the secondary output. At light or no load, Almost all cycles will be skipped and a fraction of cycles will be related to the power consumption used to support the power supply.

Compared to conventional pulse width modulation (PWM) control, the Tinyswitch on/off control scheme has a very fast response time, high line ripple rejection and good transient response.
Powering up/down the Tinyswitch requires only a 0.1µF capacitor on the bypass pin. Due to the small size of this capacitor, the turn-on delay is kept to an absolute minimum, typically 0.3 ms. Due to the fast nature of the power up/down feedback, there is no overshoot of the power supply output. During power down, the power MOSFET will switch on and off until the rectified line voltage drops to approximately 12 V. The power MOSFET will remain off without any fault.
Tinyswitch, which eliminates the bias winding, does not require the bias winding to supply power to the chip. Instead, it draws power directly from the DRAIN pin (see functional description above). This has two main benefits. First for nominal applications, this eliminates the cost of additional bias windings and associated components. Second, in charge-R applications, the current-voltage characteristic typically allows the output voltage to drop to low values while still delivering power. This application typically requires a forward bias winding, which has more associated components, none of which are necessary for a Tinyswitch.
Current Limit Operation Each switching cycle is terminated when the drain current reaches the Tinyswitch's current limit. The duty cycle is constant for a given primary inductance and input voltage. However, the duty cycle is inversely proportional to the input voltage, providing "voltage feed-forward" advantages: good line ripple rejection and relatively constant power transfer independent of the input voltage.
44 kHz switching frequency (TNY253/254) The switching frequency (no cycle jumps) is set to 44 kHz. This provides several advantages. At higher switching frequencies, capacitive switching losses account for a large proportion of the power loss in the power supply. At higher frequencies, the preferred snubber solution is an RCD or diode zener. clip.
However, due to the low switching frequency of the Tinyswitch, a simple RC snubber can be used (or even just a capacitor in 115 Vac applications below 4 W).
Second, the low switching frequency also reduces EMI filtering requirements. At 44 kHz, the 1st, 2nd and 3rd harmonics are all below 150 kHz, where EMI limits are not very strict. For power stages below 4 W, global EMI requirements can be met using only resistive and capacitive filter components (no inductors or chokes). This greatly reduces the cost of EMI filters.
Finally, if the application requires stringent noise emissions (such as video applications), the TNY253/254 will allow for more efficient use of diode buffering (and other secondary buffering techniques). The lower switching frequency allows the use of RC snubber to reduce noise without significantly affecting the efficiency of the power supply.
130 kHz Switching Frequency (TNY255) The switching frequency (no cycle jumps) is set to 130 kHz. This allows the TNY255 to output 10 W while still using the same size, low cost transformer (EE16) as the TNY253/254 for low power applications.

Bypass Pin Capacitor The Bypass Pin uses a small 0.1 microF ceramic capacitor to isolate the tinyswitch's internal power supply.
Application example TV standby
Tinyswitch is an ideal solution for low-cost, high-efficiency backup power for consumer electronics such as TVs. Figure 9 shows a 7.5 V, 1.3 W flyback circuit using a TNY253 for TV backup power. The circuit operates using the DC high voltage already provided by the mains. This input voltage is based on the TV's rated input AC voltage range, which can range from 120 to 375 Vdc for the GE. Capacitor C1 filters the high voltage DC power supply and is only needed when there is a long trace length from the DC power supply to the input to the TV backup circuit. The HVDC bus is applied to the series combination of PRIs. The Mary winding of T1 and the integrated high voltage MOSFET inside the TNY253. The low operating frequency (44 kHz) of the TNY253 allows the use of low-cost snubber circuits C2 and R1 to replace the main clamp circuit. In addition to limiting the peak drain turn-off voltage to a safe value, the RC snubber circuit reduces radiated video noise by reducing the dv/dt of the drain waveform, which is critical for video applications such as TVs and VCRs. In fixed frequency PWM and RCC circuits, the use of snubbers will result in unwanted fixed AC switching losses, independent of the load. The on/off control on the Tinyswitch eliminates this problem by adjusting the effective switching frequency. therefore,
Switching losses scale linearly with load, so the efficiency of the power supply remains relatively constant up to a fraction of 1 watt of the output load.
The secondary winding is rectified and filtered by d1 and c4 to produce a 7.5 V output. l1 and c5 provide additional filtering. The output voltage is determined by the sum of the optocoupler u2 LED forward drop (~1 V) and the Zener diode VR1 voltage. Resistor r2 maintains the bias current through the Zener to improve its voltage tolerance.
10 W standby
The TNY255 is ideal for backup applications requiring up to 10 watts of power from 230 VAC or 100/115 VAC with a multiplier circuit. The TNY255 operates at 130 kHz instead of the 44 kHz TNY253/254. Higher frequency operation allows

Use a low cost EE16 core transformer, up to 10 watt levels. A 10-watt circuit is used for this application. The circuit operates from high voltage DC power already provided by the mains. Capacitor C1 filters the HVDC power supply and is only necessary if there is a long trace length from the source of T. Provides DC power to the input of the backup circuit. The high-voltage DC bus is applied to the primary winding of T1 in series with the integrated high-voltage MOSFET in the TNY255. Diode D1, capacitor C2, and resistor R1 include a clamp circuit that limits the peak shutdown voltage on the Tinyswitch discharge pin to a safe value. SE secondary winding is rectified and filtered by d2 and c4 to provide 5 V output. Additional filtering is provided by l1 and c5. The output voltage is forward dropped by optocoupler U2 LED (~1 V) and Zener diode VR1 voltage. Resistor R2 maintains the bias current through the Zener to improve its voltage tolerance. For tighter tolerances, a TL431 precision reference IC feedback circuit can be used.
mobile phone charger
Tinyswitch is ideal for applications requiring constant voltage and constant current output. The Tinyswitch is always powered by the input high voltage, so it does not need a bias winding to be powered. Therefore, its operation does not depend on the level of the output voltage. This allows constant current charger designs to output GNSs down to zero volts.
PI

Shown is a 5.2 V, 3.6 W cellular phone charger circuit using the TNY254, providing constant voltage and constant current output over a universal input (85 to 265 Vac) range. The AC input is rectified and filtered through D1-D4, C1 and C2 to create a high voltage DC bus in series with T1, and a high voltage MOSFET inside the TNY254.T. Inductor l1 together with c1 and c2 constitute a pi filter. Resistor r1 suppresses resonance in inductor 11. The low frequency operation of the TNY254 (44 kHz) allows the use of the simple π filter described above in combination with a single y1 capacitor c8 to meet global conducted EMI standards. diode d6,
Capacitor C4 and resistor r2 include a clamp circuit that limits the turn-off voltage spike on the Tinyswitch discharge pin to a safe value. The secondary winding is rectified and filtered by d5 and c5 to provide a 5.2 V output. Additional filtering is provided by l2 and c6. The output voltage is determined by the sum of the optocouplers u2 le. D forward voltage drop (~1 V) and Zener diode VR1 voltage. Resistor R8 maintains the bias current through the Zener to improve its voltage tolerance.
A simple constant current circuit uses the vbe of the transistor q1 to sense the voltage on the current sense resistor r4, which can consist of one or more resistors.

to the appropriate value. r3 is a base current limiting resistor. When the voltage drop across R4 exceeds Vbe of transistor Q1, it turns on and takes over control of the loop by driving the optocoupler LED. r6 reduces an additional voltage to bring the operating voltage of the control loop down to zero volts at the output. D's ROP (~1.5 V) through R4 and R6 is sufficient to keep Q1 and the LED circuit active when the output is shorted. Resistors R7 and R9 limit the forward current that may develop in Q1 through VR1 due to the voltage drop between R6 and R4 under output short conditions.
AC Adapters Many consumer electronics products use low-power 50/60Hz transformer-type AC adapters. Tinyswitch can cost-effectively replace these linear adapters with lighter, smaller and more energy-efficient solutions. Figure 12 shows a 9V, 0.5W AC adapter circuit using Tny253. The circuit works with 115 Vac input. To save cost, the circuit operates in discontinuous conduction mode to provide a constant power output that is relatively independent of the input voltage. The output voltage is determined by the voltage drop across Zener diode VR1. The primary inductance of the transformer is chosen to provide power in excess of the required output power. ER is at least 50% to allow for component tolerances and to maintain some current through Zener VR1 at full load. At no load, all power is delivered to the Zener, which should have the appropriate rating and heat sink. Despite the constant power consumption from the mains input, this solution is still much more efficient than Lin. The output power of the earbud adapter is about 1 W.
The AC input is rectified by diodes d1 and d2. d2 is used to reduce conducted EMI, allowing noise to enter the neutral only during diode conduction. The rectified AC is filtered by capacitors c1 and c2 to generate a high-voltage DC bus, which is applied to the series combination of the primary winding of T1 and the high-voltage MOSFET. Next to TNY253. Resistor R2 along with capacitors C1 and C2 form a pi filter sufficient for EMI conducted emissions for these power stages. C5 is a Y capacitor for common mode EMI reduction. Since the Tinyswitch MOSFET is rated at 700 V, a simple capacitive snubber (C4) is sufficient to limit the leakage inductance. In 115 VAC applications, at low power levels, CE spikes. The secondary winding is rectified and filtered by d3 and c6.
Design Output Power Range The power levels shown in the Tinyswitch Selection Guide (Table 1) are approximate, the recommended output power range will provide a cost-optimized design and is based on the following assumptions:
The minimum DC input voltage is 90 V or higher for 1.85 VAC input, 240 V or higher for 230 VAC input, and 115 VAC with voltage multiplier.
2.Tinyswitch is not thermally limited - the source pins are soldered to enough copper area to keep the die temperature at or below 100°C. This restriction generally does not apply to TNY253 and TNY254.
Tinyswitch's maximum power capability depends on thermal environment, transformer core size and design (continuous or discontinuous), desired efficiency, minimum specified input voltage, input storage capacitance, output voltage, output diode forward voltage drop, etc., and can vary from Choose the values shown in the guide.
At loads other than maximum load, the cycle-skipping mode operation used in Tinyswitch can generate audio components in the transformer. This can cause audible noise from the transformer. Transformer audible noise can be reduced by using proper transformer construction techniques and reducing peak magnetic flux. density. For more information on audio suppression techniques, please check the "Application Notes" section on our website. Ceramic capacitors using dielectric materials such as Z5U, when used in clamp circuits and snubber circuits, can also effect to produce audio noise. If so, replacing them with capacitors with a different type of dielectric material is the easiest solution. Mylar capacitors are a good alternative.
Short circuit current Tinyswitch does not have automatic restart function. Therefore, in an output short circuit condition, Tinyswitch will continue to supply power to the load. In the worst case, the peak short-circuit current is equal to the primary current limit (Ilimit) multiplied by the transformer turns ratio (np/ns). The average current designed for l is typically 25% to 50% lower than this peak value. At the power levels of the tinyswitch, the short-circuit current is handled by the rated output diode, which is easy to adapt. Short circuit current can be minimized by selecting the smallest (lowest current limit) switch for the required power.
Layout Single-Point Ground Use a single-point ground connection at the source pins of the bypass pin capacitors and input filter capacitors.
Primary Loop Area - The primary loop area connecting the input filter capacitor, transformer primary loop, and microswitches should be as small as possible.
Primary Clamp Circuit A clamp or snubber circuit is used to minimize peak voltage and ringing on the drain during turn-off. This can be achieved by using an RC snubber circuit of less than 3 W or an RCD clamp as shown in Figure 13 for higher power. Zener clamps and diode clamps that pass once or a single 550 V Zener clamp from drain to source can also be used. In all cases, care should be taken to minimize circuit paths from the snubber/clamp assembly to the transformer and switch.
The copper under the tin switch not only acts as a single point ground, but also as a heat sink. The shaded area shown in Figure 13 should be maximized for good heat dissipation from the tin switch and output diode.
Y capacitors Y capacitors should be placed directly from the primary single point ground to the common/return terminal on the secondary side. Such placement will maximize the EMI benefit of the Y capacitor.
It is important for the optocoupler to maintain a minimum circuit path and source from the optocoupler transistor to the microswitch enable to minimize noise coupling.
Output Diode For best performance, minimize the loop area connecting the secondary winding, output diode, and output filter capacitor. The optimized layout is shown in Figure 13. Additionally, sufficient copper area should be provided at the diode's anode and cathode terminals to adequately heat the diode under output S. short circuit condition.
Input and output filter capacitors have constrictions in the traces connected to the input and output filter capacitors. There are two reasons for these contractions. The first reason is to force all high frequency current to flow through the capacitor (if the trace is wide then it can flow around the capacitor). The second reason is that CTIONS minimizes heat transfer from the Tinyswitch to the input filter capacitor and from the secondary diode to the output filter capacitor. The common/return (negative output terminal) terminal of the output filter capacitor should be connected to a short, low resistance path to the secondary winding. Also, the common/return output connection should be made directly from the secondary winding pin, not from the Y capacitor connection point.