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A shoot-through prevention circuit is used in a power conversion circuit that uses a passive level-shifter to drive a P-type transistor in a switching network. The shoot-through prevention circuit is coupled between a controller output that provides a driving signal to control the P-type transistor

A shoot-through prevention circuit is used in a power conversion circuit that uses a passive level-shifter to drive a P-type transistor in a switching network. The shoot-through prevention circuit is coupled between a controller output that provides a driving signal to control the P-type transistor and the passive level-shifter coupled to a control terminal of the P-type transistor. The shoot-through prevention circuit couples the controller output to the passive level-shifter when the driving signal has a first logic level associated with turning on the P-type transistor and isolates the controller output from the passive level-shifter when the driving signal has a second logic level associated with turning off the P-type transistor.

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What is claimed is: 1. A power conversion circuit comprising: a switching network comprising at least a high-side switch and a low-side switch configured to selectively couple a source voltage to an output node, wherein the high-side switch is a P-type transistor coupled between the source voltage

What is claimed is: 1. A power conversion circuit comprising: a switching network comprising at least a high-side switch and a low-side switch configured to selectively couple a source voltage to an output node, wherein the high-side switch is a P-type transistor coupled between the source voltage and the output node; a level-shifter coupled to a control terminal of the high-side switch, wherein the level-shifter is configured to change a voltage reference of a driving signal provided by a controller output to control the high-side switch; and an electronic circuit coupled between the controller output and the level-shifter, wherein the electronic circuit comprises a semiconductor switch and prevents shoot-through current by closing the semiconductor switch to couple the controller output to the level-shifter when the driving signal at the controller output has a first logic level and opening the semiconductor switch to isolate the controller output from the level-shifter when the driving signal at the controller output has a second logic level. 2. The power conversion circuit of claim 1, wherein the semiconductor switch comprises an N-channel field-effect-transistor with a source terminal coupled to the controller output, a drain terminal coupled to the level-shifter and a gate terminal coupled to a predetermined voltage. 3. The power conversion circuit of claim 1, wherein the semiconductor switch comprises an NPN bipolar junction transistor with an emitter coupled to the controller output, a collector coupled to the level-shifter and a based coupled to a predetermined voltage through a series base resistor. 4. The power conversion circuit of claim 1, wherein the electronic circuit further comprises a diode coupled in parallel with the semiconductor switch between the controller output and the level-shifter. 5. The power conversion circuit of claim 1, wherein the first logic level corresponds to a logic low associated with turning on the high-side switch and the second logic level corresponds to a logic high associated with turning off the high-side switch. 6. A power conversion circuit comprising: a switching network comprising at least a high-side switch and a low-side switch configured to selectively couple a source voltage to an output node, wherein the high-side switch is a P-type transistor coupled between the source voltage and the output node; a level-shifter coupled to a control terminal of the high-side switch, wherein the level-shifter is configured to change a voltage reference of a driving signal provided by a controller output to control the high-side switch; and an electronic circuit coupled between the controller output and the level-shifter, wherein the electronic circuit prevents shoot-through current by coupling the controller output to the level-shifter when the driving signal has a first logic level and isolating the controller output from the level-shifter when the driving signal has a second logic level, wherein the level-shifter comprises: a capacitor coupled between the electronic circuit and the control terminal of the high-side switch; a resistor coupled between the source voltage and the control terminal of the high-side switch; and a zener diode with a cathode coupled to the source voltage and an anode coupled to the control terminal of the high-side switch. 7. The power conversion circuit of claim 1, wherein the P-type transistor is a metal-oxide-semiconductor field-effect-transistor with a source terminal coupled to the source voltage, a drain terminal coupled to the output node and a gate terminal coupled to the control terminal. 8. The power conversion circuit of claim 1, wherein the switching network is a half-bridge or a full-bridge switching circuit. 9. The power conversion circuit of claim 1, wherein the high-side switch and the low-side switch alternately conduct to generate an alternating current waveform at the output node of the switching network. 10. The power conversion circuit of claim 9, further comprising a transformer with a primary winding coupled to the output node of the switching network and a secondary winding coupled to a lamp. 11. The power conversion circuit of claim 9, further comprising a low-pass filter coupled to the output node of the switching network to generate an output voltage with a voltage level that is proportional to a duty cycle of the alternating current waveform. 12. A method to prevent shoot-through in a switching network of a power conversion circuit, the method comprising: using a level-shifter to change a voltage reference of a driving signal provided by a controller output that controls a P-type transistor in the switching network; using a semiconductor switch to selectively couple the controller output to the level-shifter; closing the semiconductor switch to couple the controller output to the level-shifter when the driving signal has a first logic level; and opening the semiconductor switch to isolate the controller output from the level-shifter when the driving signal has a second logic level. 13. The method of claim 12, wherein the first logic level is associated with turning on the P-type transistor and the second logic level is associated with turning off the P-type transistor. 14. A method to prevent shoot-through in a switching network of a power conversion circuit, the method comprising: using a level-shifter to change a voltage reference of a driving signal provided by a controller output that controls a P-type transistor in the switching network, wherein the level-shifter comprises: a capacitor coupled between the controller output and the P-type transistor; and a resistor and a diode coupled in parallel between an input voltage and the P-type transistor; coupling the controller output to the level-shifter when the driving signal has a first logic level; and isolating the controller output from the level-shifter when the driving signal has a second logic level. 15. The method of claim 12, wherein the switching network is a half-bridge circuit with an additional N-type transistor that alternating conducts with the P-type transistor to generate an alternating current waveform at an output of the switching network. 16. The method of claim 12, wherein the switching network is a full-bridge circuit with two P-type transistors and each of the P-type transistors has a different level-shifter for coupling to separate controller outputs. 17. The method of claim 12, wherein the P-type transistor is a field-effect-transistor with a source terminal coupled to an input voltage, a drain terminal coupled to an output terminal of the switching network and a gate terminal coupled to the level-shifter. 18. A power conversion circuit comprising: means for level-shifting a driving signal to control a P-type transistor in a switching network; means for selectively coupling the driving signal to the means for level-shifting the driving signal when the driving signal has a first predetermined logic level corresponding to an on-state of the P-type transistor; and means for selectively isolating the driving signal from the means for level-shifting the driving signal when the driving signal has a second predetermined logic level corresponding to an off-state of the P-type transistor. 19. The power conversion circuit of claim 18, further comprising means for generating an alternating current waveform at an output of the switching network. 20. The power conversion circuit of claim 19, wherein the alternating current waveform is coupled through a transformer to drive one or more fluorescent lamps in a backlight system.