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Practical power supply of single end fly back type switching

2015-03-24 15:03  
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Practical power supply of single end fly back type switching regulated power supply
The following diagram is a practical power supply of single end fly back type switching regulated power supply. It adopts CW3840 pulse width modulation integrated circuit to control. At present, CW3840 is pulse width modulation with many functions. Its internal circuit including precise power supply, oscillator, error amplifier, over voltage and over current comparator, slop generator, pulse width modulation and slow starts and program control circuit, etc. AC main supply voltage 220V (or 110V) passes bridge rectifier VD1 to rectify and C1, C2 to filter. Then it will generate 300V DC voltage. The voltage pass resistor R3, R4 to reduce voltage. Then it will add to CW3840's 15 end and as working voltage. CW3840's working voltage slowly increased to 12V because of capacitor C3. This voltage passes R7, R8 to divide voltage and add it to 2 end of over voltage comparator. The threshold value of this comparator is 3V. When 2 end voltage is less than 3V, comparator outputs low level. It can make the drive transistor on integrated circuit cutting off and starts latch is locking. It indicated under voltage error. It also makes 8 end and capacitor C9 to be low level. Protective power supply is slow starting.