Highly efficient switching power converter using a charge pump to power the drive circuit
View Patent ↗A switching power converter having a first and a second transistor are connected in series with the transformer to provide higher switching efficiency. A charge pump circuit is coupled to a drive circuit to provide a power source for driving the first transistor. A third transistor is connected between the transformer and the ground to help the switching of the transformer and the charge of the charge pump circuit. A switching control circuit is coupled to the output of the switching power converter to generate a first switching signal and a second switching signal for regulating the switching power converter. The first switching signal is coupled to drive the first transistor and the second transistor. The second switching signal is coupled to drive the third transistor.
1. A switching power converter, comprising:
a transformer, comprising a primary winding having a first terminal and a second terminal, a secondary winding being coupled to an output of the switching power convener;
a first transistor, connected from an input voltage to the first terminal of the primary winding;
a second transistor, connected from the second terminal of the primary winding to a ground;
a drive circuit, coupled to the first terminal of the primary winding and the first transistor for driving the first transistor;
a charge pump circuit, connected to the drive circuit to provide a power source to the drive circuit, comprising a capacitor and a charge-pump diode, wherein the capacitor is connected to the drive circuit, and the charge-pump diode is connected from a supply voltage to the capacitor;
a diode, connected from the second terminal of the primary winding to the input voltage;
a third transistor, coupled from the first terminal of the primary winding to the ground; and
a switching control circuit, coupled to the output of the switching power converter to generate switching signals for regulating the switching power converter,
wherein the switching signals include a first switching signal and a second switching signal, the first switching signal is coupled to drive the first transistor and the second transistor, the second switching signal is coupled to drive the third transistor, and the supply voltage charges the capacitor through the charge-pump diode when the third transistor is turned on.
2. The switching power converter as claimed in claim 1 , wherein the switching control circuit generates a first delay time after the first switching signal is disabled and before the second switching signal is enabled, and wherein the switching control circuit generates a second delay time after the second switching signal is disabled and before the first switching signal is enabled.
3. The switching power converter as claimed in claim 1 , wherein the first transistor and the second transistor are driven with a first pulse width and the third transistor is driven with a second pulse width.
4. The switching power converter as claimed in claim 1 , further comprising a second diode coupled from the ground to the first terminal of the primary winding.
5. The switching power converter as claimed in claim 1 , further comprising a buffer circuit connected to the second transistor for driving the second transistor.
6. A switching power converter, comprising:
a transformer;
a first transistor, connected from an input voltage to the transformer;
a second transistor, connected from the transformer to a ground;
a drive circuit, coupled to the first transistor for driving the first transistor;
a buffer circuit, connected to the second transistor for driving the second transistor;
a charge pump circuit, connected to the drive circuit to provide a power source to the drive circuit, comprising a capacitor and a charge-pump diode, wherein the capacitor is connected to the drive circuit, and the charge-pump diode is connected from a supply voltage to the capacitor;
a first diode, connected from the transformer to the input voltage;
a second diode, coupled from the ground to the transformer; and
a switching control circuit, coupled to an output of the switching power converter to generate a switching signal for regulating the switching power converter;
wherein the switching signal is coupled to the drive circuit and the buffer circuit for driving the first transistor and the second transistor, in which the first transistor and the second transistor are driven with a pulse width, and the supply voltage charges the capacitor through the charge-pump diode when the first and second transistors are turned off.