DC/DC converter with capacitor voltage balancing
A method for voltage balancing of series connected capacitors, wherein a voltage in an intermediate circuit of an electric circuit can be easily and safely balanced between a plurality of series connected capacitors and thus these components are operated safely in terms of their voltage strength. This problem is solved in that the voltage balancing is accomplished in that, in a first step of the method, an at least partial discharging of a first or a second capacitor occurs across a first or second winding of a transformer, while thanks to the action of the transformer a current is induced in a second step of the method in the second or first winding which charges the second or first capacitor as a charging current.
1. A method for a voltage balancing of series connected capacitors, the method comprising the steps of:
providing at least two series connected capacitors of a series circuit, each of the capacitors connected to a power supply voltage; and
applying a high voltage across the series circuit, wherein the voltage balancing is accomplished by the steps:
at least partial discharging a first one of the capacitors or a second one of the capacitors across a first winding or a second winding of a transformer, wherein each of the first winding and the second winding is a primary winding of the transformer disposed on a primary side of the transformer; and
inducing a current by action of the transformer in the second winding or the first winding to charge the second one of the capacitors or the first one of the capacitors as a charging current;
providing a rectifier diode, a storage capacitor, and a resistor electrically connected with a secondary winding disposed at a secondary side of the transformer; and
transforming energy from the primary side of the transformer to the secondary side of the transformer with switching of the first one of the capacitors or the second one of the capacitors.
2. The method according to claim 1 , wherein at least a partial discharging is started by closing a first semiconductor switch or a second semiconductor switch.
3. The method according to claim 1 , wherein the charging current is directed by the rectifier diode.
4. The method according to claim 1 , wherein the at least partial discharging step and the inducing a current step are repeated.
5. The method according to claim 4 , wherein the repeating of the steps is done until a voltage drop across each of the capacitors is equal in size.
6. The method according to claim 2 , wherein the first semiconductor switch and the second semiconductor switch are triggered by a central control unit which generates control signals for the first semiconductor switch and the second semiconductor switch so only one of the first semiconductor switch and the second semiconductor switch is activated.
7. The method according to claim 6 , further comprising the steps of:
determining a voltage value for each of a first voltage U C1 and a second voltage U C2 across the capacitors before generating the control signals for the first semiconductor switch and the second semiconductor switch; and
triggering and switching through one of the first semiconductor switch and the second semiconductor switch depending on a magnitude of the first voltage U C1 and the second voltage U C2 .
8. The method according to claim 1 , wherein a directional output current is created by the secondary winding of the transformer and the rectifier diode.
9. The method according to claim 1 , wherein the first one of the capacitors and the second one of the capacitors are formed by a plurality of parallel switched partial capacitances.