High Side Transistor Drivers
Hey Bits & nvisser,
still occupied understanding the schematic. My concern is the control of the power transistors.
Please have a look to the pspice simulations attached. The optos were replaced by bare wire in order to have a look to genuine currents and voltages.
If the simulation isn't wrong it is very obvious that the load and the voltage of the battery loaded will have an essential influence to the control of the power transistors. R7 = 1K should be definitely of lower value because it stops Q10 from switching to low voltage difference (CE). On the other hand a big load and a discharged battery J4/J6 can destroy the opto.
Independent of this the data sheet of the H11 opto (optos are current amplifiers/deminishers as transistors) shows that:
- 9mA of diode current can produce 5mA max of output current
- 60ma of diode current can produce 16mA of output current.
This might be a quite severe limitation for switching the transistors. They need more base current in order to switch high current like above 1A.
Additional you should take in account, that using a bulb as load introduces a highly variable load (cold curent approx. 10 times the hot current) having an major effect on driving the transistors (see simulations).
I remember reading somewhere, that the load should be a inductor or motor - is that true?
These effects mentioned above might overwrite and hide the expected true overunity effects.
Besides:
Designing a high side switch is a very demanding story if losses require to be low. Once again: JB knew why he introduced the transformers( Mueller Report). Mys guess is that these 8 Ohm / 1000 Ohm ratio refers to the AC impedance for audio frequencies. The DC impedandce will be much lower. My measurements at such transformers show about ca. 2 Ohm / 30 Ohm.
Please comment the simulations. I wonder if you measure similar voltages in your circuits.
Hey Bits & nvisser,
still occupied understanding the schematic. My concern is the control of the power transistors.
Please have a look to the pspice simulations attached. The optos were replaced by bare wire in order to have a look to genuine currents and voltages.
If the simulation isn't wrong it is very obvious that the load and the voltage of the battery loaded will have an essential influence to the control of the power transistors. R7 = 1K should be definitely of lower value because it stops Q10 from switching to low voltage difference (CE). On the other hand a big load and a discharged battery J4/J6 can destroy the opto.
Independent of this the data sheet of the H11 opto (optos are current amplifiers/deminishers as transistors) shows that:
- 9mA of diode current can produce 5mA max of output current
- 60ma of diode current can produce 16mA of output current.
This might be a quite severe limitation for switching the transistors. They need more base current in order to switch high current like above 1A.
Additional you should take in account, that using a bulb as load introduces a highly variable load (cold curent approx. 10 times the hot current) having an major effect on driving the transistors (see simulations).
I remember reading somewhere, that the load should be a inductor or motor - is that true?
These effects mentioned above might overwrite and hide the expected true overunity effects.
Besides:
Designing a high side switch is a very demanding story if losses require to be low. Once again: JB knew why he introduced the transformers( Mueller Report). Mys guess is that these 8 Ohm / 1000 Ohm ratio refers to the AC impedance for audio frequencies. The DC impedandce will be much lower. My measurements at such transformers show about ca. 2 Ohm / 30 Ohm.
Please comment the simulations. I wonder if you measure similar voltages in your circuits.
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