- Joined
- Nov 17, 2011
- Messages
- 13,700
First: I'm not an expert at switched mode supplies.
But: May I add some thoughts on your "test circuit"? To me it looks like a step-down (buck) regulator with some problems/deficiencies:
1) Yes, you will need some kind of voltage doubler or similar. The MOSFET needs a gate-source voltage > 0V, at least 5V if you use a logic gate MOSFET, 10 V - 20 V if you use a standard switching MOSFET (consult datasheet). Since the source of the MOSFET is at battery voltage (or higher during the conducting phase) it will need a gate voltage higher than the battery voltage by at least that amount.
2) Where does that control signal at point A come from? This signal should be generated from a stable regulating loop. If the MOSFET is turned on for too long a time, the inductor will saturate, being in effect a short circuit, and a large current will flow uncontrolled into the battery. Therefore you need some feedback from the output of the circuit to point A.
I suggest you use a specialized switch mode battery charger (Google or http://www.ti.com/lit/ds/symlink/uc3909.pdf as just one example)
3) For stable operation some storage capacitor at the input (after the bridge rectifier) of the circuit is required. This capacitor will smooth out fluctuations in the input voltage due to the rectification of the sinusoidal input voltage from the generator or short dips due to varying wind speeds.
4) I'd add some kind of undervoltage protection. If the voltage from the generator is less than the battery voltage, the step-down charger will not work because it is not able to force current into the battery. On the contrary, if the MOSFET is turned on with the battery voltage being higher than the generator voltage, current will flow from the battery into your circuit (how much current depends on the details of your circuit).
Regards,
Harald
But: May I add some thoughts on your "test circuit"? To me it looks like a step-down (buck) regulator with some problems/deficiencies:
1) Yes, you will need some kind of voltage doubler or similar. The MOSFET needs a gate-source voltage > 0V, at least 5V if you use a logic gate MOSFET, 10 V - 20 V if you use a standard switching MOSFET (consult datasheet). Since the source of the MOSFET is at battery voltage (or higher during the conducting phase) it will need a gate voltage higher than the battery voltage by at least that amount.
2) Where does that control signal at point A come from? This signal should be generated from a stable regulating loop. If the MOSFET is turned on for too long a time, the inductor will saturate, being in effect a short circuit, and a large current will flow uncontrolled into the battery. Therefore you need some feedback from the output of the circuit to point A.
I suggest you use a specialized switch mode battery charger (Google or http://www.ti.com/lit/ds/symlink/uc3909.pdf as just one example)
3) For stable operation some storage capacitor at the input (after the bridge rectifier) of the circuit is required. This capacitor will smooth out fluctuations in the input voltage due to the rectification of the sinusoidal input voltage from the generator or short dips due to varying wind speeds.
4) I'd add some kind of undervoltage protection. If the voltage from the generator is less than the battery voltage, the step-down charger will not work because it is not able to force current into the battery. On the contrary, if the MOSFET is turned on with the battery voltage being higher than the generator voltage, current will flow from the battery into your circuit (how much current depends on the details of your circuit).
Regards,
Harald