Pwm is a method of digital coding of analogue signal levels. Through the use of high-resolution counters, the space ratio of a square wave is designed to encode the level of a specific simulated signal. The pwm signal is still numerical, because at any given time, the full range of direct power supply is either complete (on) or non-existent (offf). The voltage or current source is added to the simulated load by a repeat pulse sequence either through (on) or off (offf). It is when the direct power supply is added to the load and when the power supply is cut off。
Any analogue value can be coded using pwm as long as the bandwidth is sufficient。
As shown in figure 1, a series of equal band-wide pulses is used to replace a half-wave, half-wave-n-sine, which is considered to be a series of n-connected pulses with equal widths but varying in widths; and a rectangular pulse is used to replace the same bands with varying widths, with a medium-point overlap, an equal area (fractions) and a change in width by the pattern of the sine。
Spwm waveform - a pwm waveform with the same effect as a sine wave, depending on the pattern of the pulse width。
PwmReverser
The standard three-phase power level (power level) is used to drive a three-phase straight currenter, as shown in figure 1. The power level produces an electric field, which, in order for the electric machine to work well, must maintain an angle close to 90° between the rotor magnetic field. The six-step sequence control produces six static magnetic field vectors that must be changed at a specified rotor position. Holl effect sensor scans the rotor position. In order to provide six step-in currents to rotors, the power level uses six power mosfets that can be converted to a different sequence. A common switching pattern is explained below, which provides six steps into the current。
Mosfet q1, q3 and q5 hf (hf) switch, q2, q4 and q6 low frequency (lf) switch. When a low frequency mosfet is open and a high frequency mosfet is switching, a power level is created。
Step 1) the power level provides power to both phases simultaneously, while the third phase is not. It is assumed that l1, l2, l3 is not supplied. In this case, mosfet q1 and q2 were in a conductivity state, with currents passing through q1, l1, l2 and q4。
Step 2) mosfet q1 off. Because it can't suddenly interrupt the current, it creates extra voltage until..Body diodeD2 is directly biased and is allowed to continue currents. The currents are maintained by d2, l1, l2 and q4。
Step 3) q1 is open and d2 is suddenly inverse. The total current on q1 is the sum of the restored current on the power supply (e. G. Step 1) and the diode d2。
Shows the body - leaking diodes. In step 2, currents flow to body-spill diode d2 (see figure 1), where the diodes are positively biased and a small number of fluxes are injected into diodes and p。
When mosfet q1 leads, the diode d2 is inversely biased, and a small number of streamers in section n enter p+ and vice versa. This rapid transfer has resulted in large currents passing through diodes, from the n-epi to the p+ zone, from leakage to source poles. The electrons l1 showed high resistance to the peak currents running through q2 and q1. Q1 showed additional current peaks and increased switch losses during the conductivity. Figure 4a describes the passage process of mosfet。
In order to improve the performance of diodes in these special applications, researchers have developed mosfet, which has the properties of rapid diode restoration. When the diode catheters are transposed, the reverse recovery peak current irrm is smaller。
Analysis of pwm reverse circuits in conjunction with a simple reverse circuit chart
Frequency of resistance r2 and capacitating c1 integrated circuit internal oscillators. Preset r1 to fine-tune the frequency of oscillators. 14 foot and 11 foot ic internal drive transistor launch polar terminals. The drive transistor terminals (foots 13 and 12) are connected to one another and to the 8v track (7808 output). The 50 hz pulverized train could be phased out at 180 degrees in ic at the quote 14 and 15。
These signals drive in the subsequent transistor phase. When the 14 foot signal is high level, transistor q2 is connected, which in turn causes transistor q4, q5, q6 point to flow from the current +12 v power source (cell) to a pass-through first half (labelled) transformer (t1), primary schools transfer to the ground via transistor q4, q5 and q6。
Thus, the second voltage of the mutilator (due to electromagnetic induction) is the first half of the wave shape of 220v. During this period, 11 feet are low and the stage of success will be inactive. Q8 and q9 will be opened when the third quarter q7 results of the ic draw 11 clouds high are obtained and exchanged. Q7, q8, q9, from the +12 v power source via the lower part of the primary transformer and by transfer to the ground via the transistor, and the resulting voltage, in the second half of the cycle (marked) of the current 220v output shape facilitated by the t2 sub-guide。
The reversible output (t2 output) excavation point is marked b, c and provided to the main transformer t2. At this high voltage step of the transformer t2, the bridge d5 currents it and this voltage (relative of the output voltage of the reverser) provide pin1 via odi r8, r9, r16 and (the internal error amplifier input of the ic) as compared to the internal reference voltage。
The values required for this differential output voltage to be proportional to the output voltage and the ic-regulated driving signals (foots 14 and 12) to allow the output voltage to change to the values required. R9 presets can be used to regulate the output voltage of the inverter because it directly controls the feedback of the output voltage error amplifier component of the variable。
Diode d3 and d4 relay diodes protect the peak of voltage generated by the primary selection of the switch transformer (t2) for the drive-level transistor. R14 and r15 restricted the fourth quarter of the base and q7. R12 and r13 were the fourth quarter and the q7 to prevent accidental switch-down of on to resist electrical resistance. C10 and c11 are the output noises from the varianter. C8 is a steady pressure of ic 7805 for filtering caps. R11 restrictions restrict currents passing through led light d2。
KeywordsPwmRetrovert
