Charge pump electronic ballast for use with low input voltage
View Patent ↗A charge pump electronic ballast for use with low input voltage is described. The charge pump electronic ballast includes a DC/AC inverter circuit having two switching transistors, a resonant circuit having an inductor and a capacitor. The charge pump electronic ballast further includes a voltage multiplying rectifying circuit for transforming low input AC voltage into high output DC voltage, and a charge pump circuit having an inductor and a first pump capacitor.
1. A charge pump electronic ballast for use with low input voltage, the charge pump electronic ballast comprising:
a DC/AC inverter circuit comprising two switching transistors;
a resonant circuit composed of a resonant inductor and a resonant capacitor;
a voltage multiplying rectifying circuit for transforming low input AC voltage into a high output DC voltage; and
a charge pump circuit comprising an inductor and a first pump capacitor wherein a current does not charge the first pump capacitor prior to ignition of the lamp.
2. The charge pump electronic ballast according to claim 1 , wherein the one terminal of said first pump capacitor is coupled to a first input of the voltage multiplying rectifying circuit and is coupled to an output of an AC power supply via the inductor of said charge pump circuit, the other terminal of said first pump capacitor is coupled to said resonant capacitor via a lamp, and a second input of the voltage multiplying rectifying circuit is coupled to the other output of said AC power supply.
3. The charge pump electronic ballast according to claim 2 , wherein said voltage multiplying rectifying circuit comprises a voltage doubling rectifying circuit comprising two diodes and two capacitors.
4. The charge pump electronic ballast according to claim 3 , wherein the connection point of said two diodes is the first input of said voltage multiplying rectifying circuit, the connection point of said two capacitors is the second input of said voltage multiplying rectifying circuit, and two terminals of a parallel circuit comprising a first half-bridge including said two diodes and a second half-bridge including said two capacitors are outputs of said voltage multiplying rectifying circuit.
5. The charge pump electronic ballast according to claim 4 , wherein said charge pump electronic ballast further comprises a shutdown protection circuit comprising a thyristor.
6. The charge pump electronic ballast according to claim 5 , wherein said charge pump electronic ballast further comprises: a first resistor, wherein the one terminal of the first resistor is coupled to said other terminal of the first pump capacitor and the other terminal of the first resistor is coupled to the anode of the thyristor; and a second resistor, wherein the one terminal of the second resistor is coupled to said other terminal of the first pump capacitor and the other terminal of the second resistor is coupled to a output of the voltage multiplying rectifying circuit.
7. The charge pump electronic ballast according to claim 6 , wherein the charge pump electronic ballast further comprises: a third diode; a fourth diode, wherein said third diode and said fourth diode are coupled between the first half-bridge and the outputs of the voltage multiplying rectifying circuit respectively, and said third diode, said fourth diode, and the two diodes of the first half-bridge are in a series aiding connection; and a second pump capacitor wherein the one terminal of the second pump capacitor is coupled to said other terminal of the first pump capacitor and the other terminal of the second pump capacitor is coupled to the connection point of the first half-bridge and the fourth diode.