Datasheet TOP242, TOP243, TOP244, TOP245, TOP246, TOP247, TOP248, TOP249, TOP250 (Power Integrations) - 9

TOP242-250
transients. This feed-forward operation is illustrated in time to allow the CONTROL pin to discharge to the internal Figure 7 by the different values of I (Y, R or F package) or supply undervoltage threshold of 4.8 V (approximately 32 L I (P or G package). Note that for the same CONTROL ms for a 47 µF CONTROL pin capacitance), the CONTROL M pin current, higher line voltage results in smaller operating pin goes into the hysteretic mode of regulation. In this duty cycle. As an added feature, the maximum duty cycle mode, the CONTROL pin goes through alternate charge DC is also reduced from 78% (typical) at a voltage and discharge cycles between 4.8 V and 5.8 V (see MAX slightly higher than the UV threshold to 30% (typical) at CONTROL pin operation section above) and runs entirely the OV threshold (see Figure 11). Limiting DC at higher off the high voltage DC input, but with very low power MAX line voltages helps prevent transformer saturation due to consumption (160 mW typical at 230 VAC with M or X large load transients in TOP248, TOP249 and TOP250 pins open). When the TOPSwitch-GX is remotely turned forward converter applications. DC of 38% at high on after entering this mode, it will initiate a normal start-up MAX line was chosen to ensure that the power capability of sequence with soft-start the next time the CONTROL pin the TOPSwitch-GX is not restricted by this feature under reaches 5.8 V. In the worst case, the delay from remote normal operation. on to start-up can be equal to the full discharge/charge cycle time of the CONTROL pin, which is approximately
Remote ON/OFF and Synchronization
125 ms for a 47 µF CONTROL pin capacitor. This reduced TOPSwitch-GX can be turned on or off by controlling consumption remote off mode can eliminate expensive and the current into the LINE-SENSE pin or out from the unreliable in-line mechanical switches. It also allows for EXTERNAL CURRENT LIMIT pin (Y, R or F package) and microprocessor controlled turn-on and turn-off sequences into or out from the MULTI-FUNCTION pin (P or G package) that may be required in certain applications such as inkjet (see Figure 11). In addition, the LINE-SENSE pin has a 1 V and laser printers. threshold comparator connected at its input. This voltage threshold can also be used to perform remote ON/OFF
Soft-Start
control. This allows easy implementation of remote Two on-chip soft-start functions are activated at start-up with ON/OFF control of TOPSwitch-GX in several different ways. a duration of 10 ms (typical). Maximum duty cycle starts A transistor or an optocoupler output connected between from 0% and linearly increases to the default maximum the EXTERNAL CURRENT LIMIT or LINE-SENSE pins of 78% at the end of the 10 ms duration and the current (Y, R or F package) or the MULTI-FUNCTION pin (P or G limit starts from about 85% and linearly increases to 100% package) and the SOURCE pin implements this function at the end of the 10 ms duration. In addition to start-up, with “active-on” (Figures 22, 29 and 36) while a transistor soft-start is also activated at each restart attempt during or an optocoupler output connected between the LINE- auto-restart and when restarting after being in hysteretic SENSE pin (Y, R or F package) or the MULTI-FUNCTION regulation of CONTROL pin voltage (V ), due to remote OFF C (P or G package) pin and the CONTROL pin implements or thermal shutdown conditions. This effectively minimizes the function with “active-off” (Figures 23 and 37). current and voltage stresses on the output MOSFET, the clamp circuit and the output rectifier during start-up. This When a signal is received at the LINE-SENSE pin or the feature also helps minimize output overshoot and prevents EXTERNAL CURRENT LIMIT pin (Y, R or F package) or saturation of the transformer during start-up. the MULTI-FUNCTION pin (P or G package) to disable the output through any of the pin functions such as OV, UV
Shutdown/Auto-Restart
and remote ON/OFF, TOPSwitch-GX always completes its To minimize TOPSwitch-GX power dissipation under fault current switching cycle, as illustrated in Figure 10, before conditions, the shutdown/auto-restart circuit turns the the output is forced off. The internal oscillator is stopped power supply on and off at an auto-restart duty cycle slightly before the end of the current cycle and stays there of typically 4% if an out of regulation condition persists. as long as the disable signal exists. When the signal at Loss of regulation interrupts the external current into the the above pins changes state from disable to enable, CONTROL pin. V regulation changes from shunt mode to C the internal oscillator starts the next switching cycle. This the hysteretic auto-restart mode as described in CONTROL approach allows the use of these pins to synchronize pin operation section. When the fault condition is removed, TOPSwitch-GX to any external signal with a frequency the power supply output becomes regulated, V regulation C between its internal switching frequency and 20 kHz. returns to shunt mode, and normal operation of the power supply resumes. As seen above, the remote ON/OFF feature allows the TOPSwitch-GX to be turned on and off instantly, on a cycle-
Hysteretic Over-Temperature Protection
by-cycle basis, with very little delay. However, remote Temperature protection is provided by a precision analog ON/OFF can also be used as a standby or power switch to circuit that turns the output MOSFET off when the junction turn off the TOPSwitch-GX and keep it in a very low power temperature exceeds the thermal shutdown temperature consumption state for indefinitely long periods. If the (140 °C typical). When the junction temperature cools to TOPSwitch-GX is held in remote off state for long enough below the hysteretic temperature, normal operation
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Rev. R 10/20 www.power.com