In my previous article on Power Tips for the EE Era, I discussed how to use a two-switch flyback circuit to improve the efficiency of a low-power isolated converter. The main cost of a two-switch flyback circuit is that it requires a floating high-side drive compared to a single-switch flyback circuit. A gate drive transformer is typically used for the high side FET of a two-switch flyback circuit, and the use of a gate drive transformer requires some skill. If the core is not properly reset within each cycle, it may be saturated.

One of the most common drive technologies is the use of an AC coupling capacitor in series with the drive winding. This capacitor forces the average current to 0A, which ensures that the transformer will not saturate. However, it is still possible to saturate during transients, and the DC information of the drive signal will be lost on the secondary side of the drive transformer.

Figure 1 shows a simple method of driving a transformer when it is not necessary to use a coupling capacitor. When the drive signal goes high, the small signal FET, Q2 is turned on, and the drive voltage is applied to the winding of the transformer. When the drive signal goes low, it pulls the same end of the winding down to ground and turns off Q2. When Q2 is off, the magnetizing current in the transformer is forward biased to D1, and in the opposite direction, VDD is applied to the transformer windings. For less than 50% duty cycle, the transformer is guaranteed to be fully reset. By adding a Zener diode in series with D1, you can extend the duty cycle to more than 50%.

This driver circuit offers two additional advantages. First, all of the magnetizing energy is recovered to VDD, which increases efficiency. Second, during the magnetization reset, the driving of the FET is achieved by a negative drive. This negative drive reduces switching losses by speeding up the turn-off time.

Figure 1: Using a simple circuit like this to easily drive a transformer

This simple drive circuit ensures proper reset of the drive transformer and increases efficiency.

DITUO Home Humidifier Features as following:

• Aroma Humidifier OEM/ODM/OBM service is available.

• Premium Quality Materials: PP materials.

• Adjustable mist output: Strong or Weak.

• 7-color Led light or warm light.

• Waterless Auto-Off Function.

• 4 timer setting: 1 hour, 3 hours, 6 hours and continuous.

• Whisper-quiet design, Aromatherapy Humidifier ideals for bedroom, living room, office, spa, Yoga, hotel.

• Certification (ISO9001 CE ROHS FCC) & Warranty (12 months)

• Great Gifts: It is good choice to use this lovely Personal Humidifier as gifts to your friends and families, lovers.

• After-sale Guaranteed: Please contact with us if there is any problem.

Home Humidifier

Home Humidifier,Aroma Humidifier,Aromatherapy Humidifier,Personal Humidifier

Shenzhen Dituo Electronic Co.,Ltd. , https://www.sz-dituo.com