Switching circuit of power converter having voltage-clipping device to improve efficiency
View Patent ↗A switching circuit for power converters is presented. It includes a voltage-clipping device, a resistive device, a first transistor and a second transistor. The voltage-clipping device is coupled to an input voltage. The first transistor is connected in series with the voltage-clipping device for switching the input voltage. The second transistor is coupled to control the first transistor and the voltage-clipping device in response to a control signal. The resistive device provides a bias voltage to turn on the voltage-clipping device and the first transistor when the second transistor is turned off. Once the second transistor is turned on, the first transistor is turned off and the voltage-clipping device is negatively biased. The voltage-clipping device is developed to clamp a maximum voltage for the first transistor.
1. A switching circuit for power converters, comprising:
a voltage-clipping device, having an input terminal directly coupled to an input voltage, and a control terminal directly coupled to a gate terminal of the voltage-clipping device;
a first transistor, having a drain terminal directly coupled to an output terminal of said voltage-clipping device, wherein a source terminal of said first transistor provides a supply voltage to a control circuit of the power converter;
a second transistor, having a drain terminal directly coupled to a gate terminal of said first transistor and a control terminal of said voltage-clipping device; a gate terminal of said second transistor receives a control signal; and
a resistive device, connected from said control terminal of said voltage-clipping device to an output terminal of said voltage-clipping device, wherein said resistive device provides a bias voltage to turn on said first transistor and said voltage-clipping device when said second transistor is turned off; said control signal turns on said second transistor for switching off said first transistor and providing a negative bias for said voltage-clipping device, wherein said voltage-clipping device clamps a maximum voltage for said first transistor.
2. The switching circuit as claimed in claim 1 , said voltage-clipping device comprising:
a P-type substrate;
a first diffusion region and a second diffusion region, having N-type ions to form an N-type well in said P-type substrate;
an input diffusion region, containing N+-type ions, forming an input region in said first diffusion region;
an output diffusion region, containing N+-type ions, forming an output region in said second diffusion region;
a P-type field block, formed in said N-type well; wherein said P-type field block is disposed adjacent to said input region for generating junction fields;
an isolated P-type well, formed in said N-type well, wherein said isolated P-type well is formed in said second diffusion region;
a control diffusion region, containing P+-type ions, forming a control region in said isolated P-type well; and
a channel, formed between said input region and said output region; wherein said control region controls a width of said channel to control a current flow in said channel.
3. The switching circuit as claimed in claim 1 , wherein said resistive device is a resistor.
4. The switching circuit as claimed in claim 1 , wherein said resistive device is formed with a plurality of transistors.
5. A switching circuit, comprising:
a voltage-clipping device, receiving an input voltage, wherein the voltage-clipping device has a control terminal directly coupled to a gate terminal of the voltage-clipping device;
a first transistor, directly connected in series with said voltage-clipping device for receiving and switching said input voltage outputted from the voltage-clipping device;
a resistive device, coupled to said voltage-clipping device and said first transistor for providing a bias voltage to turn on said voltage-clipping device and said first transistor; and
a second transistor, turning off said first transistor and providing a negative bias to said voltage-clipping device, wherein said voltage-clipping device clamps a maximum voltage for said first transistor, and said second transistor is controlled by a control signal.
6. The switching circuit as claimed in claim 5 , said voltage-clipping device comprising:
a P-type substrate;
a diffusion region, having N-type ions to form an N-type well in said P-type substrate;
an input diffusion region, containing N+-type ions, forming an input region in said N-type well;
an output diffusion region, having N+-type ions, forming an output region in said N-type well;
a P-type field block, formed in said N-type well, wherein said P-type field block is disposed adjacent to said input region for generating junction fields;
an isolated P-type well, formed in said N-type well; wherein said isolated P-type well is disposed adjacent to said output region;
a control diffusion region, containing P+-type ions, forming a control region in said isolated P-type well; and
a conduction channel, formed between said input region and said output region; wherein said control region controls a width of said conduction channel to control a current flow in said conduction channel.