introduction
With the development of power electronics technology and devices; especially the emergence of new devices such as power MOSFET, IGBT, MCT, IPM and monolithic integrated pulse width modulation power amplifier; the voltage SPWM inverter has been widely concerned, developed and applied. .
The traditional intermediate frequency power supply generally includes two parts: the pre-stage voltage regulation; the latter-stage intermediate frequency inverter; and the basic use of discrete components. Although there is no traditional rotating parts; but the volume is still large; the efficiency is low; the structure is complicated; the debugging is troublesome; the unreliable factors are more; directly affecting the reliability of the power supply and the equipment. Various new types of shipborne electronic equipment have imposed stricter requirements on the volumetric weight and performance indicators of the intermediate frequency power supply; while the traditional intermediate frequency power supply has been unable to meet the requirements; the solution can only be to seek more advanced frequency conversion technology.
Sine Pulse Width Modulation (SPWM) technology utilizes the turn-on and turn-off of power devices; the DC voltage is converted into a voltage pulse sequence of equal amplitude and sinusoidal width; and by controlling the width and pulse sequence of the pulse The cycle is to achieve the purpose of variable voltage conversion. The main advantages of the power supply using SPWM technology are: high efficiency, small size, low noise, low distortion and fast response.
working principle
Early SPWM IF power supplies are mostly composed of discrete components; the oscillators, comparators, dead-band generators, drivers, etc. in the system need to be carefully adjusted; and the reliability is not high; now this scheme has been rarely used; Monolithic integrated SPWM controller; such as HEF4752V; integrated oscillator, comparator, op amp, etc. inside a single IC; greatly simplifies system design; system reliability is also greatly improved; with high-speed microcontroller and low price The emergence of DSP controllers; digital IF power supplies have begun to be widely used; at the same time, programmable digital SPWM generators, such as SA838, have appeared; further simplifying system design; improving system reliability. But all of these control schemes require at least three isolated power supplies to form a complete power system; the power supply volume is difficult to further reduce.
APEX Corporation combines power electronics technology and power amplifier technology to design and manufacture pulse width modulation power amplifiers; this series of amplifiers will be oscillators, PWM generators, dead-band generators, bootstrap drivers, IGBTs and freewheeling diodes, overcurrent /Overheat protection and other functional components are all integrated; make it a complete PWM power amplifier; users only need to provide the required analog modulation signal as required; after the amplifier will output the fundamental wave as the modulation signal of the high-frequency high-voltage SPWM signal The sequence; after high-frequency filtering, a modulated signal with both amplitude and power amplification can be obtained. If the amplifier and filtering are treated as a whole; their function is equivalent to a traditional linear power amplifier; but its efficiency is much higher.
The PWM power amplifier represents the typical parameters of the model SA08:
Power input voltage 16 ~ 500VDC; single-phase full-bridge output; maximum output current 20A; maximum transmission power 10KW; internal oscillation and control circuit to achieve 22. 5kHz switching frequency; module efficiency up to 98%; with internal overcurrent and overheat protection; It also provides user external current limit setting and shutdown function; MO-127 package; operating temperature range - 55 ~ 125 °C.
The appearance and pinout of the SA08 are shown in Figure 1; the internal function diagram is shown in Figure 2.
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