LYT4228 Current Regulation issue during flicker.

Posted by: manvi111 on 04/26/2017

Hello,

I am using LYT4228 IC for my 50 Watt (72V 620mA) Driver. Input Voltage is 220VAC 50Hz.

Many drivers already installed and all are working well with better efficiency. There is no issue with performance and stability except one issue.

When I try to flicker the input voltage (Quickly on/off power by switch), some time watt goes to 63Watt.

I have checked many drivers by giving them flicker. Many of them goes to 63Watt and stay on that power. Driver goes to normal wattage after off/on the power.

I have tested the driver in much worst conduction. But no other issue in driver.

Driver details are shown below.

Input Voltage: 220 VAC 50Hz
PF: 0.978
Output Voltage: 72V 620mA
Efficiency: 88.6%
IC: LYT4228 (Reduced Mode using 47uF X7R Bias Capacitor)
Transformer : PQ2620

Files

50W.jpg (190.02 KB)

50W_LL - 74V 610mA ISO LYT4228 -PQPQ.pixls (45 KB)

回應

I have found the issue.

IC dectect bypass capacitor (47uF) incorrectly during flicker. And IC Start with FULL POWER Mode. I have attached extra 10uF capacitor (Totap BP cap : 47+10 = 57uF). And Issue resolved.

Is it okay to use 68uF capacitor as BP capacitor ?

Do you happen to use ceramic cap as BP capacitor? 47uF is ok if you are using an e-cap. If you use ceramic, the capacitance especially with 5V bias drops significantly and might detect full-mode like what you observed. Higher capacitance is Ok. I would use 100 uF ceramic or 47 uF ecap.

I'm glad to read this information.
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