Datenblatt-Suchmaschine für elektronische Bauteile |
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FAN41501 Datenblatt(PDF) 5 Page - Fairchild Semiconductor |
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FAN41501 Datenblatt(HTML) 5 Page - Fairchild Semiconductor |
5 / 11 page © 2014 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN41501 • 1.0.1 5 Functional Description (Refer to Figure 1) Starting in June 2015, UL943 will require all permanently connected GFCI products to perform a self test function. The FAN41501, together with a GFI controller device – like the FAN4149 – provides GFI fault protection and periodic self testing of the key GFCI components: solenoid, SCR, GFI controller, sense coil, and other discrete components. The FAN41501 has an internal 5.35 V shunt regulator. With diodes D2-5 and resistor R2, the shunt regulator clamps the FAN41501 VDD supply voltage to 5.35 V. Capacitor C5 provides bias during the VAC zero phase crossing so the FAN41501 is continuously biased. When power is first applied, an internal Power-On-Reset (POR) circuit detects when VDD is greater than 2.5 V. The POR circuit generates an internal reset pulse and initializes a one-second timer. After one second, the first self-test cycle starts. During the positive half cycle when the “line-hot” voltage is positive with respect to the “line- neutral ” voltage, the SCR anode voltage is monitored by means of resistor R4 connected to pin 1 (SCR Test). The FAN41501 clamps this pin to VDD, mirrors the current through R4 to an internal low-pass filter circuit, and compares its value to an internal reference threshold. When the current level exceeds the reference threshold, an internal latch is set. This test determines the continuity of the solenoid and SCR. The threshold level is determined by: Vthrms = (65 A x R4) + 4 (1) where Vthrms is the rms VAC input voltage with a tolerance of ±10%. With the recommended application values, the SCR anode voltage must exceed a worst-case peak voltage of approximately 65 V (rms). Equation (1) can be used if a lower threshold voltage value is desired to allow this test to pass during a brownout or voltage sag condition. To test the functionality of the GFCI controller, sense coil, and SCR; a simulated ground fault condition is generated. Like the SCR Test pin; the Phase pin (pin 4) is clamped to VDD + 700 mV, mirrors the current through R3 to an internal low-pass filter circuit, and compares its value to an internal reference. This internal circuit detects when the phase signal is near the end of the positive half cycle. When this occurs, an internal current source is enabled to bias the SCR Test pin. This prevents the SCR anode voltage from discharging to zero during the negative half cycle since it is reverse- biased by diode D1. At the end of the positive half cycle, the FAN41501 generates a current pulse for the Fault Test pin (pin 6). This current pulse enables transistor Q2, which biases the collector voltage of Q2 to a low voltage. During the negative half cycle when the line- neutral voltage is positive with respect to the line-hot voltage, current flows through resistor RTEST2 when Q2 is enabled. This current creates a simulated ground fault from line-neutral to load hot. This current is detected by the GFI controller (i.e. FAN4149) and, when it exceeds the programmed trip threshold set by RSET (typically 5 mArms), the controller enables the SCR Q1 (see FAN4149 datasheet for IFAULT trip threshold equation). The SCR quickly discharges the anode voltage, which is pre-biased by the FAN41501 control logic. The discharge of the anode voltage also biases the voltage at the SCR Test pin to a low voltage by forward-biasing diode D6. The FAN41501 monitors the SCR Test pin during this test cycle and sets a latch if the SCR is triggered. The simulated ground fault tests for the functionality of the controller, R1, D1, D2-5 (5), sense coil, and SCR without opening the load contacts. The load contacts do not open during this test because D1 is reversed biased, which prevents current from energizing the solenoid. Once the FAN41501 detects the triggering of the SCR, the current pulse for Q2 is disabled and the bias current for pin SCR Test is removed. This disables the SCR so that during the next positive half cycle the solenoid is not energized. With the recommended application values, the simulated ground fault triggers the controller with a VAC input voltage greater than 50 Vrms. If a different voltage threshold is required, the RTEST2 resistor can be adjusted (per the FAN4149 datasheet). Figure 4, Figure 5 and Figure 6 show a passing self-test cycle. The waveform of channel 4 shows when the Q2 transistor is enabled and a ground fault is simulated by the current through resistor RTEST2. The channel 3 waveform shows the gate of the SCR Q1. Figure 6 shows the pre-bias for the SCR anode voltage, waveform of channel 1. Figure 6 illustrates that, when the gate of the SCR is enabled by the controller, the voltage of the SCR anode is quickly discharged. The FAN41501 detects this and a self-test cycle is completed with all of the required components passing. The Q2 bias is disabled, which causes the GFCI controller to disable the SCR gate bias. Note: 5. Redundant diodes may be required. If the first self-test cycle passes after power up, subsequent self-test cycles occur every 90 minutes. At no time does the FAN41501 disable the normal controller GFI protection circuitry. If any one of the above self tests fail, the FAN41501 repeats the self testing until a 66 ms timer expires. If this occurs, the EOL latch is enabled and the FAN41501 EOL Alarm pin 5 goes HIGH. This signal can be connected to a separate SCR or to the gate of Q1 with a series diode. When the EOL Alarm goes HIGH, the SCR is enabled and energizes the solenoid, which opens the load contacts. When the EOL Alarm pin goes HIGH, if it is connected to the gate of an SCR, VDD drops below 2.5 V. This generates a Power-On-Reset that resets the logic and repeats a self-test cycle in one second. Figure 7 to Figure 10 show a FAN41501 self-test cycle for a SCR, GFI controller, sense coil, and solenoid failure. |
Ähnliche Teilenummer - FAN41501 |
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Ähnliche Beschreibung - FAN41501 |
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