High Output Voltage Power Supply

Hi


Im doing a project based on half bridge converter of IR2153 which could produce a high output voltage using the LTspice simulation by means of half bridge topology. Well, im just wondering as the volatge across the two capacitors that is pointed in the image shown wasnt give half the volatge source as stated in the theory of half bridge voltage source inverter. Can someone point me out and explain why the volatge across these two capacitor was not Vs/2? Does it something to do with some interference produced by the transformer in the cicuit? Thanks in advance.

For the center of the half-bridge to remain centered the charge through each switch must be identical over time. Otherwise the center point will walk to one rail.

What do you mean by the charge through each switch must be identical? As far as i know, when Im changing the value of resistor R3, for the Rt pin in the driver IR2153, the voltage across the two capacitors would also change.

If the charge thru each switch differs one or the other capacitor will slowly charge as the other discharges. Any difference in switch ON time will do this.

This is the big problem with the half-bridge and some designs incorporate circuitry to slightly adjust the ON time of one switch to keep the capacitor junction at the midpoint.

You can experiment with this by removing the IC and driving the FETs with pulsed voltage sources. Slightly change the duty cycle of one switch (I.E. 20% for one and 21% for the other) and you will observe the capacitor midpoint walk toward one rail.

By saying that, the capacitor did resonating but did not obey the voltage source inverter. What factor that disobey this voltage source inverter again because i am still a bit confused.

Can you post a larger schematic? I cannot read the component values.

This is the schematic diagram of my half bridge power supply.

The IR2153 datasheet shows the driver driving a series LC against circuit common. You have it driving against the capacitive divider. Have you tried driving against circuit common? Or against a voltage source equal to one-half the supply?

As I know, i altered the swtiching frequency by changing the resistor connected to Rt pin in order to get higher freqeuncy in the circuit. Having said that, what should be the cause of the problem in my simulation? As i measured the frequency resonant, it differs from what i obtained when i plot a graph of output volatge against frequency. And yes, when the circuit is not connected to the transformer, the voltage source equal one half the supply.

Your circuit is resonant at 1.7 kHz with a Q of about 3. Are you operating the switcher at that frequency?

I would get the circuit working without the capacitive midpoint and proceed from there.

But note that unless the charge transferred by each switch is equal there will be a net DC charge injected into the capacitors and they will charge. The midpoint will "walk" toward one voltage rail.