Semiconductor power devices, resistors, and capacitors usually have parasitic inductances and capacitances. When a rapid switching transition occurs in the switching devices, it creates a noise, an electromagnetic interference and ringing, on the waveforms.
These issues in power switching devices can be resolved by either replacing the switching device with another switch that has rated to exceed the stress or by using a series Resistor-Capacitor RC circuit to reduce the stresses to a safe level. The former solution increases the cost, while the snubber circuit, which is a simple RC circuit, is popular and is commonly used for any practical switching circuit, such as power converters, motor drivers, and power electronic devices.
Although some works have been addressed in designing the RC snubber circuit, those studies are either based on simple work, or they involve very complex method with results that are often difficult to interpret. In this paper, therefore, we establish how to design an RC snubber circuit experimentally for a buck converter.
The buck converter is modelled in PSpice software with and without the RC snubber circuit, where the comparison can be made. The model results show that the current across the switching device is reduced by the RC snubber circuit. The PWM drive unit 21 is connected to the gates of the first and second switches Q 1 , Q 2 , a drain of the first switch Q 1 , and a source of the second switch Q 2.
The drain of the first switch Q 1 is connected to the source of the switch Q 2. A source of the first switch Q 1 is grounded. A drain of the second switch Q 2 is connected to a power supply Vin. The inductor L and capacitor C are connected in series between the drain of the first switch Q 1 and ground. The three input terminals J 1 -J 3 are linearly arranged between the drain of the first switch Q 1 and ground. To decrease the voltage spikes of the buck converter , the detecting terminal A 5 is connected to the input terminal J 1 i.
The first terminals A 1 and A 2 are respectively connected to the input terminals J 1 and J 2. The second terminals A 3 and A 4 are respectively connected to the terminals J 2 and J 3. The switch S is turned on to start the control unit The control unit 11 adjusts resistance value of the resister unit 12 by changing states of the group of first switch contacts AB 0 -AB 3 and adjusts capacitance value of the capacitor unit 13 by changing states of the group of first switch contacts AB 4 -AB 7.
Therefore, multiple groups of resistance and capacitance can be selected and provided to the buck converter The detecting contact RA 0 detects voltage spikes of the buck converter corresponding to each group of resistance and capacitance.
Therefore, a suitable group of resistance and capacitance corresponding to a lowest voltage spike can be determined by the control unit 11 by comparing the detected voltage spikes. The snubber circuit can automatically determine a suitable group of resistance and capacitance for the buck converter to decrease the voltage spike, which is convenient and effective.
It is believed that the exemplary embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments. A snubber circuit for a buck converter, the snubber circuit comprising: a resistor unit that provides multiple groups of resistance values;.
The snubber circuit as claimed in claim 1 , wherein the control unit includes a group of first switch contacts connected to the resistor unit, a group of second switch contacts connected to the capacitor unit, a detecting contact connected to the detecting unit, the control unit changes states of the group of first switch contacts and the group of second switch contacts to select each group of resistance values and capacitance values, and obtains the detected voltage spike from the detecting unit.
The snubber circuit as claimed in claim 2 , wherein the detecting circuit includes a first and second resistors connected in series, one end of the first and second resistors is grounded, another end of the first and second resistors is connected to the buck converter to detect the voltage spikes, a node between the first and second resistors is connected to the detecting contact. The snubber circuit as claimed in claim 2 , further including a start unit connected to the control unit to start the control unit.
The snubber circuit as claimed in claim 4 , wherein the control unit further includes a start contact, the start unit includes a third resistor and a switch, the third resistor is connected between a power supply and the start contact, the switch is connected between the start contact and ground. The snubber circuit as claimed in claim 2 , further including a display unit connected to the control unit to display the resistances of the resistor unit, the capacitances of the capacitor unit, and the detected voltage spikes.
The snubber circuit as claimed in claim 6 , wherein the control unit further includes a group of display control contacts and a group of data transmitting contacts connected to the display unit. The snubber circuit as claimed in claim 1 , wherein the resistor unit is a resistance box. The snubber circuit as claimed in claim 1 , wherein the capacitor unit is a capacitance box.
A buck converter, comprising: a first switch;. The buck converter as claimed in claim 10 , wherein the control unit includes a group of first switch contacts connected to the resistor unit, a group of second switch contacts connected to the capacitor unit, a detecting contact connected to the detecting unit, the control unit changes states of the group of first switch contacts and the group of second switch contacts to select each group of resistance values and capacitance values, and obtains the detected voltage spikes from the detecting unit by the detecting contact.
The buck converter as claimed in claim 11 , wherein the detecting circuit includes a first and second resistors connected in series, one end of the first and second resistors is grounded, another end of the first and second resistors is connected to the buck converter to detect the voltage spikes, a node between the first and second resistors is connected to the detecting contact.
The buck converter as claimed in claim 11 , further including a start unit connected to the control unit to start the control unit. The buck converter as claimed in claim 13 , wherein the control unit further includes a start contact, the start unit includes a third resistor and a switch, the third resistor is connected between a power supply and the start contact, the switch is connected to between the start contact and ground.
The buck converter as claimed in claim 11 , further including a display unit connected to the control unit to display the resistances of the resistor unit, the capacitances of the capacitor unit, and the detected voltage spikes.
The buck converter as claimed in claim 15 , wherein the control unit further includes a group of display control contacts and a group of data transmitting contacts connected to the display unit.
The buck converter as claimed in claim 10 , wherein the resistor unit is a resistance box. The buck converter as claimed in claim 10 , wherein the capacitor unit is a capacitance box.
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