Capacitor charger system, power modulator and resonant power converter
A capacitor charger system has a resonant power converter to connect to a capacitor via a rectifier. The resonant power converter has a switch-based bridge network, an internal transformer, a resonant circuit, and an amplitude stabilization circuit. The switch-based bridge network comprises at least one pair of switches. The resonant circuit includes a series-resonant branch with capacitive and inductive components, and the resonant circuit is connected in the circuit path to a midpoint between a pair of switches of the switch-based bridge network. The amplitude stabilization circuit provides stabilization of the resonant amplitude of the resonant circuit, and the amplitude stabilization circuit includes one-way conducting circuitry connected between an unrestricted node defined by a junction and a connection point of the resonant power converter having a predefined voltage level at operation. The resonant power converter connects to the output rectifier via the secondary winding of the internal transformer.
1. A capacitor charger system for a capacitor to be charged and discharged in cycles, wherein the capacitor charger system comprises a resonant power converter for connection to said capacitor via an output rectifier,
said resonant power converter comprises a switch-based bridge network, an internal transformer, a resonant circuit, and an amplitude stabilization circuit,
said switch-based bridge network comprises at least one pair of controlled switches,
said resonant circuit includes a series-resonant branch comprising at least one capacitive component and at least one inductive component, and said resonant circuit is connected in the circuit path to a midpoint between a pair of controlled switches of the switch-based bridge network, and the capacitive part of said resonant circuit is connected in a series path with a primary winding of said internal transformer,
said amplitude stabilization circuit is configured to provide stabilization of a resonant amplitude of the resonant circuit, and said amplitude stabilization circuit includes one-way conducting circuitry connected between:
i) an unrestricted node defined by a junction anywhere in the circuit path from a capacitive component to an inductive component of the series-resonant branch, and
ii) at least one connection point of said resonant power converter having a predefined voltage level at operation,
to thereby stabilize the resonant amplitude to vary within predefined limits; and
said resonant power converter is configured for connection to said output rectifier via the secondary winding of said internal transformer.
2. The capacitor charger system of claim 1 , wherein said one-way conducting circuitry includes a diode connected from said junction to a connection point having a predefined voltage level at operation.
3. The capacitor charger system of claim 2 , wherein said diode is connected from said junction to a connection point being represented by a power rail of the resonant power converter.
4. The capacitor charger system of claim 3 , wherein said diode is connected from said junction to a DC power rail of the resonant power converter.
5. The capacitor charger system of claim 1 , wherein said one-way conducting circuitry includes a first diode connected from said junction to a first connection point having a first predefined voltage level at operation, and a second diode connected from said junction to a second connection point having a second predefined voltage level at operation.
6. The capacitor charger system of claim 5 , wherein each diode is connected from said junction to a respective connection point being represented by a respective one of the power rails of the power converter.
7. The capacitor charger system of claim 6 , wherein each diode is connected from said junction to a respective one of the DC power rails of the power converter.
8. The capacitor charger system of claim 5 , wherein the first connection point has a positive voltage level at operation and the second connection point has a negative voltage level at operation.
9. The capacitor charger system of claim 1 , wherein the inductive part of said resonant circuit is integrated with the primary winding of said internal transformer.
10. The capacitor charger system of claim 1 , wherein the capacitor to be charged is at least partially discharged and the capacitor charger system is called on to recharge the capacitor, and said amplitude stabilization circuit is configured to step in at the beginning of the recharge process to prevent a run-away condition.
11. The capacitor charger system of claim 1 , wherein said resonant power converter is configured to operate based on a switching frequency that lies within 5-10% of a resonant frequency of the resonant circuit.
12. The capacitor charger system of claim 11 , wherein said resonant power converter is configured to operate based on a switching frequency that lies within 3% of the resonant frequency of the resonant circuit.
13. The capacitor charger system of claim 12 , wherein said resonant power converter is configured to operate based on a switching frequency that lies within 1% of the resonant frequency of the resonant circuit.
14. The capacitor charger system of claim 11 , wherein said resonant power converter is configured to operate based on a switching frequency not closer to the resonant frequency than a given safety margin to avoid any overlap between the cycles of the power converter.
15. The capacitor charger system of claim 1 , wherein said resonant circuit includes a series-resonant branch composed of a series-connection of a capacitor and an inductor, and said unrestricted node is defined by a junction between the capacitor and the inductor, a so-called LC-junction of the series-resonant branch.
16. The capacitor charger system of claim 1 , wherein said resonant power converter is a resonant half-bridge converter or a resonant full-bridge converter.
17. The capacitor charger system of claim 1 , wherein said predefined voltage level is a fixed and stable voltage level.
18. The capacitor charger system of claim 1 , wherein a further capacitor is arranged in a series path with the primary winding of the internal transformer and configured to prevent saturation of the transformer due to a DC current build-up.
19. A power modulator comprising a capacitor charger system of claim 1 .
20. A resonant power converter comprising:
a switch-based bridge network, wherein said switch-based bridge network comprises at least one pair of controlled switches,
an internal transformer,
a resonant circuit, wherein said resonant circuit includes a series-resonant branch comprising at least one capacitive component and at least one inductive component, and said resonant circuit is connected in the circuit path to a midpoint between a pair of controlled switches of the switch-based bridge network, and the capacitive part of said resonant circuit is connected in a series path with a primary winding of said internal transformer,
an amplitude stabilization circuit, wherein said amplitude stabilization circuit is configured to provide stabilization of a resonant amplitude of the resonant circuit, and said amplitude stabilization circuit includes one-way conducting circuitry connected between:
i) an unrestricted node defined by a junction anywhere in the circuit path from a capacitive component to an inductive component of the series-resonant branch, and
ii) at least one connection point of said resonant power converter having a predefined voltage level at operation,
to thereby stabilize the resonant amplitude to vary within predefined limits.