The selection of the fast diode is given and the test results are given.
With the advancement of technology and the gradual improvement of the technological level, industrial field equipment needs to be equipped with various specifications of power supply, and PLCC, instruments, meters and other equipment have higher and higher requirements on power supply. The switching power supply gradually replaces the linear regulated power supply due to the stability of the output voltage, low ripple, small size, and light weight. This paper introduces a half-bridge switching power supply circuit and its design ideas.
1 Half-Bridge Switching Power Supply Working Principle The main circuit of the half-bridge switching power supply is shown in the figure. Two transistors Mi and M2, two capacitors Ci and C2 form a power loop.
Medium, V is provided by a single-phase ~220V power supply through the rectifier bridge rectification and filtering. The two transistors of Mi and M2 work complementarily. Ci and C2 form the other arm of the bridge, C2 and M2C1 are alternately turned on, and voltages of opposite polarities on the capacitors C1 and C2 are respectively applied to the primary winding of the switching transformer. The secondary winding of the switching transformer has a center tap, which forms a full-wave rectification through two fast rectifying diodes. After being filtered by the high-frequency inductor L() and the capacitor C0, the output is stable DC V0. The duty cycle of the pulse is changed S (Bu 7VT ) The output voltage can be changed. If and Uf are usually used as feedback signals to participate in PWM generation to control output voltage and current stability.
Chen Zhibin: The design of the single-phase switching power supply is the working waveform of the circuit. Where Gi and G2 are the gate pulse waveforms of the power tube, ui, which is the primary voltage and current waveform of the transformer. In the quiescent state, Ci and C2 are connected in series, and the initial voltage is 1/2 of V. After the tube is turned on, C2 starts to charge, and the current gradually increases. After the arrival of the Gi pulse trailing edge, Mi quickly shuts down. Due to the leakage inductance of the transformer, the primary current of the transformer continues to flow through the anti-coupling diode of M2 and rapidly drops to zero. At this point, the circuit is in the dead zone of the pulse, and neither Mi nor M2 is turned on. In the next stage, M2 is opened and the process is the same as Mi.
The working waveform of the factory gate half-bridge switching power supply Fig. 2 The selection of the main components 2.1 The selection of the main power devices Ml and M2 2.1. The selection of the collector voltage Uceo The maximum voltage that the Mi and M2 can withstand is V. Considering the input voltage is io % fluctuation, and the peak voltage at which the switching transistor is turned on and off is 20% Mi and the voltage that M2 is subjected to is actually i.iXi.2V 32V. When selecting a tube, a certain margin is usually left. The operating voltage is 80% of the rated voltage, there is a single-phase converter, V is usually supplied by the ~220V power supply after rectification and filtering, V is about 260 / = bearing 8 - 0.9) V is the primary voltage peak.
When selecting a pipe, it is usually necessary to consider factors such as current spikes and inrush currents generated when the switch is turned on and off, and a margin is generally left in the design. The operating current takes 80% of the rated current, so when actually selecting, select the standard current level.
2. i.3 Collector Dissipated Power Pc Selection The DC average loss Pn of the switch tube during turn-on is 2.2 Capacitance Ci and C2 are selected. In the half-bridge converter, the equivalent capacitance is Ceq=Cl+C2=2C. During the conduction of the switch, At=tn, the voltage of the voltage divider capacitor is Uc, and the voltage drop is Auc=U is the ripple voltage. Usually, the average voltage of U2=1%-10% is used. In the half bridge converter, Take ur=(1%-so where / is the operating frequency of the converter.
The voltage dividing capacitor is generally selected from a polypropylene capacitor.
2.3 Selection of fast diode Di and D2 2.3.1 Reverse peak voltage converter The output voltage is V, and the peak value of the secondary voltage of the transformer is the reverse voltage that the diode is subjected to. Considering the leakage inductance of the transformer and the voltage of the switch when it is turned off and on. The impact and spike, should leave a certain margin, generally take 2.3.2 forward conduction current converter output current / transformer secondary output peak current is /, considering current overshoot and spike, generally take When a single pipe cannot meet the needs, multiple parallel connections can be used, but the current sharing problem needs to be considered.
3 Test According to the principle of the above-mentioned half bridge converter, a switching power supply was designed. The input is ~220V single-phase power supply, the output is 48V maximum output current 12A. (25 °C); C1 and C2 are polypropylene 1呷, 1 shows the test waveform. As can be seen from the figure, in the voltage waveform, local oscillation occurs at the leading edge and the trailing edge, and the peak amplitude is 75% of the full scale, which is caused by the leakage inductance of the transformer. If the peak voltage is not limited, the IGBT will be damaged when the operating frequency is high or the load is large. Usually the RCD absorbing circuit is added between the source and the drain of the IGBT. The time constant t=RC can take 5% of the half cycle. Can play a better effect.
In order to reduce the overshoot during the turn-on and turn-off of the switch, the fast recovery diode MUR1100 (1A, 1000V) and the non-inductive capacitor PPB 0.047/630V (CEL) are connected in parallel between the source and the drain of the switch M1 and M2. The oscillation amplitude is reduced to about 25% of the full scale. For example, although the hard-switching PWM converter is used, the appropriate protection circuit and the surge absorption circuit can effectively reduce the hard turn-on and hard turn-off. Negative Effects. The design is simple, reliable, and low in cost, and has practical significance.
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With the advancement of technology and the gradual improvement of the technological level, industrial field equipment needs to be equipped with various specifications of power supply, and PLCC, instruments, meters and other equipment have higher and higher requirements on power supply. The switching power supply gradually replaces the linear regulated power supply due to the stability of the output voltage, low ripple, small size, and light weight. This paper introduces a half-bridge switching power supply circuit and its design ideas.
1 Half-Bridge Switching Power Supply Working Principle The main circuit of the half-bridge switching power supply is shown in the figure. Two transistors Mi and M2, two capacitors Ci and C2 form a power loop.
Medium, V is provided by a single-phase ~220V power supply through the rectifier bridge rectification and filtering. The two transistors of Mi and M2 work complementarily. Ci and C2 form the other arm of the bridge, C2 and M2C1 are alternately turned on, and voltages of opposite polarities on the capacitors C1 and C2 are respectively applied to the primary winding of the switching transformer. The secondary winding of the switching transformer has a center tap, which forms a full-wave rectification through two fast rectifying diodes. After being filtered by the high-frequency inductor L() and the capacitor C0, the output is stable DC V0. The duty cycle of the pulse is changed S (Bu 7VT ) The output voltage can be changed. If and Uf are usually used as feedback signals to participate in PWM generation to control output voltage and current stability.
Chen Zhibin: The design of the single-phase switching power supply is the working waveform of the circuit. Where Gi and G2 are the gate pulse waveforms of the power tube, ui, which is the primary voltage and current waveform of the transformer. In the quiescent state, Ci and C2 are connected in series, and the initial voltage is 1/2 of V. After the tube is turned on, C2 starts to charge, and the current gradually increases. After the arrival of the Gi pulse trailing edge, Mi quickly shuts down. Due to the leakage inductance of the transformer, the primary current of the transformer continues to flow through the anti-coupling diode of M2 and rapidly drops to zero. At this point, the circuit is in the dead zone of the pulse, and neither Mi nor M2 is turned on. In the next stage, M2 is opened and the process is the same as Mi.
The working waveform of the factory gate half-bridge switching power supply Fig. 2 The selection of the main components 2.1 The selection of the main power devices Ml and M2 2.1. The selection of the collector voltage Uceo The maximum voltage that the Mi and M2 can withstand is V. Considering the input voltage is io % fluctuation, and the peak voltage at which the switching transistor is turned on and off is 20% Mi and the voltage that M2 is subjected to is actually i.iXi.2V 32V. When selecting a tube, a certain margin is usually left. The operating voltage is 80% of the rated voltage, there is a single-phase converter, V is usually supplied by the ~220V power supply after rectification and filtering, V is about 260 / = bearing 8 - 0.9) V is the primary voltage peak.
When selecting a pipe, it is usually necessary to consider factors such as current spikes and inrush currents generated when the switch is turned on and off, and a margin is generally left in the design. The operating current takes 80% of the rated current, so when actually selecting, select the standard current level.
2. i.3 Collector Dissipated Power Pc Selection The DC average loss Pn of the switch tube during turn-on is 2.2 Capacitance Ci and C2 are selected. In the half-bridge converter, the equivalent capacitance is Ceq=Cl+C2=2C. During the conduction of the switch, At=tn, the voltage of the voltage divider capacitor is Uc, and the voltage drop is Auc=U is the ripple voltage. Usually, the average voltage of U2=1%-10% is used. In the half bridge converter, Take ur=(1%-so where / is the operating frequency of the converter.
The voltage dividing capacitor is generally selected from a polypropylene capacitor.
2.3 Selection of fast diode Di and D2 2.3.1 Reverse peak voltage converter The output voltage is V, and the peak value of the secondary voltage of the transformer is the reverse voltage that the diode is subjected to. Considering the leakage inductance of the transformer and the voltage of the switch when it is turned off and on. The impact and spike, should leave a certain margin, generally take 2.3.2 forward conduction current converter output current / transformer secondary output peak current is /, considering current overshoot and spike, generally take When a single pipe cannot meet the needs, multiple parallel connections can be used, but the current sharing problem needs to be considered.
3 Test According to the principle of the above-mentioned half bridge converter, a switching power supply was designed. The input is ~220V single-phase power supply, the output is 48V maximum output current 12A. (25 °C); C1 and C2 are polypropylene 1呷, 1 shows the test waveform. As can be seen from the figure, in the voltage waveform, local oscillation occurs at the leading edge and the trailing edge, and the peak amplitude is 75% of the full scale, which is caused by the leakage inductance of the transformer. If the peak voltage is not limited, the IGBT will be damaged when the operating frequency is high or the load is large. Usually the RCD absorbing circuit is added between the source and the drain of the IGBT. The time constant t=RC can take 5% of the half cycle. Can play a better effect.
In order to reduce the overshoot during the turn-on and turn-off of the switch, the fast recovery diode MUR1100 (1A, 1000V) and the non-inductive capacitor PPB 0.047/630V (CEL) are connected in parallel between the source and the drain of the switch M1 and M2. The oscillation amplitude is reduced to about 25% of the full scale. For example, although the hard-switching PWM converter is used, the appropriate protection circuit and the surge absorption circuit can effectively reduce the hard turn-on and hard turn-off. Negative Effects. The design is simple, reliable, and low in cost, and has practical significance.
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