Flyback power converters having a high side driving circuit
View Patent ↗A dual-switch flyback power converter includes a control circuit to generate a switching signal. A high-side driving circuit includes a pulse generation circuit. The pulse generation circuit generates a pulse-on signal and a pulse-off signal to control two transistors in response to the switching signal. The two transistors further respectively provide a level-shift-on signal and a level-shift-off signal to a comparison circuit to enable/disable a high-side driving signal. Without using a charge pump circuit to power the high-side driving circuit, a floating winding of a transformer is utilized to provide a floating voltage to power the high-side driving circuit, which reduces the cost of the dual-switch flyback power converter and ensures a sufficient high-side driving capability of the high-side driving circuit.
1. A flyback power converter, comprising:
a first transformer, for energy transfer;
a high-side transistor and a low-side transistor, coupled to switch said first transformer;
two diodes, coupled to said first transformer to circulate energy of a leakage inductance of said first transformer to an input power rail of said flyback power converter;
a first control circuit, generating a first switching signal to control said high-side transistor and said low-side transistor;
a high-side driving circuit, coupled to receive said first switching signal for driving said high-side transistor; and
a second control circuit and a second transformer, generating a floating voltage to power said high-side driving circuit,
wherein said second control circuit generates a second switching signal, and said second switching signal switches said second transformer for generating an auxiliary voltage to power said first control circuit, said second control circuit, and said high-side driving circuit.
2. The flyback power converter as claimed in claim 1 further comprising a low-side driving circuit coupled to receive said first switching signal for driving said low-side transistor, and said low-side driving circuit is powered by said auxiliary voltage.
3. The flyback power converter as claimed in claim 1 , wherein said high-side transistor and said low-side transistor are turned on/off simultaneously.
4. The flyback power converter as claimed in claim 1 , wherein said high-side driving circuit is a differential-mode level-shift circuit.
5. The flyback power converter as claimed in claim 1 , wherein said high-side driving circuit comprises:
a pulse generation circuit, generating a pulse-on signal and a pulse-off signal;
two transistors, coupled to respectively receive said pulse-on signal and said pulse-off signal for generating a level-shift-on signal and a level-shift-off signal by switching on said two transistors;
a comparison circuit, receiving said level-shift-on signal and said level-shift-off signal; and
a flip-flop, set and reset by said comparison circuit to generate a high-side driving signal for driving said high-side transistor;
wherein said comparison circuit and said flip-flop are powered by said floating voltage and a floating ground reference.
6. The flyback power converter as claimed in claim 5 , wherein the pulse widths of said pulse-on signal and said pulse-off signal are both shorter than 500 nsec.
7. The power converter as claimed in claim 5 , wherein said pulse-on signal and pulse-off signal are generated in response to said first switching signal.
8. A power converter comprising:
a transformer, for energy transfer;
a high-side transistor and a low-side transistor, coupled to switch said transformer;
two diodes, coupled to said transformer to circulate energy of a leakage inductance of said transformer to an input power rail of said power converter;
a control circuit, generating a switching signal to control said high-side transistor and said low-side transistor; and
a high-side driving circuit, coupled to receive said switching signal for driving said high-side transistor;
wherein said high-side driving circuit is powered by a floating voltage provided from a floating winding of said transformer.
9. The power converter as claimed in claim 8 further comprising a low-side driving circuit coupled to receive said switching signal for driving said low-side transistor.
10. The power converter as claimed in claim 9 , wherein an auxiliary winding of said transformer generates an auxiliary voltage to power said control circuit, said high-side driving circuit, and said low-side driving circuit.
11. The power converter as claimed in claim 8 , wherein said high-side transistor and said low-side transistor are turned on/off simultaneously.
12. The power converter as claimed in claim 8 , wherein said high-side driving circuit is a differential-mode level-shift circuit.
13. The power converter as claimed in claim 8 , wherein said high-side driving circuit comprises:
a pulse generation circuit, generating a pulse-on signal and a pulse-off signal;
two transistors, coupled to respectively receive said pulse-on signal and said pulse-off signal for generating a level-shift-on signal and a level-shift-off signal by switching on said two transistors;
a comparison circuit, receiving said level-shift-on signal and said level-shift-off signal; and
a flip-flop, set and reset by said comparison circuit to generate a high-side driving signal for driving said high-side transistor;
wherein said comparison circuit and said flip-flop are powered by said floating voltage and a floating ground reference.
14. The power converter as claimed in claim 13 , wherein the pulse width of said pulse-on signal and said pulse-off signal are both shorter than 500 nsec.
15. The power converter as claimed in claim 13 , wherein said pulse-on signal and the pulse-off signal are generated in response to said switching signal.