2.1 the power supply system
Power supply with dc and ac two road input, input dc to dc bus power system, ac input for the power frequency ac mains.Ac mains are in a normal state, the rectifier for dc rectifier filter, then through inverter transformation for the stabilized voltage stability of ac power supply to the load.When mains or failure occurs, the rectifier dc communicate directly by the inverter transformation for the stabilized voltage power supply to the load.After the input dc and ac mains rectifier dc current through the diode.Using this scheme not only make purified regulated ac mains, and in ac power failure, ac/dc power conversion without delay, which has greatly improve the quality of power supply.
2.2 the main circuit
The power supply adopts pay - direct - static inverter scheme, its main circuit includes rectifier, dc filter, inverter, ac filter, transformer, etc., as shown in figure 2.Among them, the cross - straight part USES the bridge rectifier, then through electrolytic capacitor filter, a smooth dc.Power switched on, the rectifier by the starting resistance of electrolytic capacitor charging, can reduce the starting current, realize the soft start.After starting, the resistance is contactor short answer.Dc input before starting circuit, also can realize the soft start.For the dc system and other electric circuits of the isolation, this power supply ac input after transformer power system with the development of the single phase inverter power supply.Than the choice of input transformer shall ensure that when the ac mains voltage rectifier output dc voltage is higher than dc system voltage, so as to ensure the normal order of the communication, the dc system to load discharge.
Straight - part adopts single phase full bridge inverter structure, is the core of this power supply.Inverter IGBT as the switch element.Use of the advantages of IGBT switch frequency, and adopts double polarity way sinusoidal pulse width modulation (SPWM) control for inverter pulse width modulation (PWM) output steady dc transform into communication, the communication base wave frequency for the required power output frequency.Inverter output PWM wave output by LC filter circuit, a transformer transformer isolation, required by the output sine wave alternating current.
To improving the performance of electromagnetic compatibility in both the input and output end of the power supply with the anti-jamming filter.
2.3 IGBT drive and protection circuit
IGBT drive and protection circuit of the power inverter bridge made from a piece of circuit board, together with the inverter bridge inverter unit module.
M57959 is a special IGBT driver circuit, the biggest can drive 400 a / 600 v components.The internal circuit has a fast optical coupling isolation, is suitable for the high frequency switch operation, about 20 KHZ and have over-current protection function.Driver circuit USES + 15 v / 10 v double power supply, in order to improve the anti-interference ability.
Before driving circuit for PWM signal processing circuit, it will transfer to the single way of PWM control circuit signal after voltage comparator plastic inverting into two way difference of 180 ° signal, as the upper and lower bridge arm of IGBT element control signals.The signal after a dead zone circuit, and its rising edge was delayed 3 ~ 4 mu s, in order to make sure the upper and lower bridge arm conduction is not less than 3 mu s dead zone, and then be sent to the driver circuit.
This power driver board with IGBT over-current, overheating power device, three kinds of dc bus voltage protection.IGBT over-current protection, by M57959 internal protection circuit, conduction saturation voltage drop across the test IGBT, over-current protection threshold by concatenated in detecting circuit regulator tube to adjust.Single phase bridge circuit of IGBT element only four protection signals, after a nand gate, into a high level fault signal, sent to the fault logic circuit.Power overheating protection device by installing temperature relay on the radiator, overheating when given break contact, temperature relay action value is 75 ℃.Dc bus voltage under-voltage protection circuit when normal, detection circuit regulator tube is punctured opening, so that the series of light coupling conduction, vice edge output low level;When voltage is too low, the detection circuit of voltage regulator tube blocking, so that the series switch off the light coupling, deputy high output fault edge level;Protect the threshold determined by the voltage regulator tube voltage value.
Drive board fault logic circuit to over current, under voltage signal through D flip-flop latch, then latch signal through the gate with overheating signal after comprehensive, blockade, to the driver module, PWM pulse complete protection.At the same time, after comprehensive fault signal and over-current, undervoltage, overheating signal is sent to the control circuit, to complete the power system monitor.

                                                                                           Dingfeng Capacitor---System Design and Implementation