L6585DE PFC and Ballast Control Integrated Circuit 2

The reference voltage of the comparator can be set to a fixed voltage or to the center pin. When connecting the lamp, a fixed reference configuration (see Figure 12) can be used for grounding, requiring two Zener diodes to move the average voltage of the lamp to 2.5V. The two Zener values affect the symmetry protection of interference: choose two differences equal to twice the reference voltage: VUP and VDOWN are the maximum allowable values of VK. When the lamp is connected to the choke coil and blocking capacitor, a block capacitor to ground configuration is used. In this configuration, the voltage on the blocking capacitor is affected by voltage ripple and superimposed on the PFC output. Using references affected by the same ripple helps to reject it and avoid premature triggering of the comparator. Once the comparator is triggered, the Tch loop begins to improve noise immunity. overcurrent protection

The occurrence of overcurrent and hard switching events increases the ohmic resistance of two cathodes symmetrically. The overall effect will result in an increase in the equivalent resistance of the lamp, and an increase in the resonance peak of the resonance curve of the resonance network will cause the overcurrent managed by L6585DE to be the same as the ignition mode, but the limit threshold and inspection threshold are 1.05 volts and 0.82 volts, respectively. diode

Hard switch protection

When FRUN is equal to the peak of the resonance curve, the load seen by the half bridge is pure resistance. In this case, the zero voltage switch no longer exists, and high current spikes will occur when the MOSFET is turned on. The voltage display at the HBCS pin shows that these peak values can be greater than 3V, and the duration depends on the resonant frequency and operating frequency. The typical value is around 40 nanoseconds and 200 nanoseconds. These spikes may cause MOSFET overheating, but if detected correctly, they can prevent the risk of operating below resonance frequency (capacitive mode). L6585DE can detect these spikes through the 2.75V threshold on the HBCS pin. If a subsequent peak of 350 (typical) is detected, the IC's counter will be turned off. This protection is blank during preheating and ignition processes. diode