3

This question is a continuation of my previous post about the resonant Royer (or Baxandall) circuit. I have built a prototype to verify the circuit.

The parameters are as follows:

enter image description here

The parameters of the transformer are as follows:

enter image description here

Except for the BJT I choose is ST13005, other parameters in the real prototype is very close to the parameters in the simulation pictures shown above.

The measured 30kHz resonant frequency is very close to theory and the simulation, but I have some problems with the BJT.

The input voltage is 37V~50V. When the input voltage is 37V, the voltage Uce is as follows, which looks perfect:

enter image description here

When the input voltage is 50V, the voltage Uce is abnormal. There is a large overlap between the C-E voltages of the two BJTs, which greatly decreases the efficiency (only about 32%). enter image description here

Does anyone have any idea why it happens?

JRE
  • 67,678
  • 8
  • 104
  • 179
T L
  • 475
  • 1
  • 8
  • 2
    Are those diodes backwards? Surely they are for breakdown protection, not reducing hFE. Is the half-wave load also connected? – Tim Williams Mar 30 '23 at 04:07
  • The load is connected. These diodes is for protection. But maybe using a normal diode like 4148 whose anode is connected to the base of BJT can also achieve the purpose. I will try it. – T L Mar 30 '23 at 06:11
  • The cathode of the diode goes to the base. These are used to steer the AC current by conducting when the base voltage goes negative, thus steering the current into the opposite transistor. – Kartman Mar 30 '23 at 12:09

1 Answers1

1

I have never loaded this circuit and its relatives with half wave. Try full wave and try choke filter and reduce feedback winding turns. See how low the supply volts can be whilst the circuit still works, you will be amazed at how low you can go. This little test gives you an idea of how much you can reduce the feedback.

JRE
  • 67,678
  • 8
  • 104
  • 179
Autistic
  • 14,235
  • 2
  • 27
  • 65