Abstract: Introduced one kind uses the TOP249Y intelligent control integration chip design switching power supply’s method, simultaneously introduced the TOP249Y chip’s internal structure and the principle of work, gave have instead stirred up-like switching power supply’s designa circuit based on the TOP249Y single end, and has carried on the analysis explanation to peripheral circuit’s design.
Key word: Switching power supply; TOP249Y; Pulse-duration modulation; TOP Switch
1 introduction
Develops unceasingly along with the PWM technology and consummates, the switching power supply obtained the widespread application, the former switching power supply’s design usually uses the topology which the control circuit and the power tube separate, but this kind of plan existence cost high, system reliable low status question. American Power Integration Company 煟 school Greece wished TOP which cow Integration Inc pulled sends the Switch series new intelligence high frequency switching power supply integration chip to solve these problems, this series chip the self-starting electric circuit, the power switching valve, the PWM control circuit and the protection circuit and so on integrated in together, thus raised power source’s efficiency, simplified switching power supply’s design and the new product development, caused the switching power supply to develop to one new time. In the article introduced one kind uses the multi-channel power take-off valve power source’s design method with the TOP Switch third generation product TOP249Y development frequency changer.
2 TOP249Y pin function and internal structure
2.1 TOP249Y base pin functions
TOP249Y uses to-220-7C seal form, its contour as shown in Figure 1. It has six base pins, is in turn the control carries C, the line examination to carry L, the limit power source to suppose fixed end X, source S, the turn-on frequency choice to carry F and drain electrode D. The various base pins’ concrete function is as follows:
The control carries C: Error amplifying circuit and feedback electric current input end. When normal work, may adjust the dutyfactor using the controlling current IC size, and may provide the internal bias by the internal parallel adjuster. When system closure, uses this end to be possible to stimulate the input current, simultaneously this end is also the bypass, restarts automatically with the compensation electric capacity’s junction.
The line examination carries L: Input voltage’s undervoltage with has pressed the examination end, simultaneously has the long-distance remote control function. TOP249Y undervoltage electric current IUV is 50μA, has pressed electric current Iav is 225μA. If the L end and the input end turn on resistance R1 is 1MΩ, then the undervoltage protection value is 50VDC, the overvoltage protection value is 225VDC.
The limiting current supposes the fixed end X: External current hypothesis adjustment end. If turns on the different resistance between X end and the source, then the switch electric current may define that in the different value, along with turning on resistance resistance number’s enlargement, the electric current which the switch permission will wind through will change is small.
Source S: Connects internal MOSFET the source, is primary circuit’s common point and the power source backflow reference point.
The turn-on frequency choice carries F: When F termination to source, its turn-on frequency is 132kHz, but when the F termination to controls the end, its turn-on frequency becomes the original frequency half, namely 66kHz.
Drain electrode D: Connects internal MOSFET the drain electrode, when start may provide the internal bias electric current through the interior high-voltage switch electric current.
2.2 TOP249Y internal structures
TOP249Y interior work functional block diagram as shown in Figure 2, this electric circuit mainly by the control potential source, the band gap datum potential source, the oscillator, the parallel adjuster/error amplifier, the PDM keyer (PWM), the gate actuation level and the output stage, the overflow protection circuit, the overheated protection circuit, shutdown/automatic heavy parts and so on start-up circuit and high-pressured current supply is composed.
3 based on TOP249Y switching power supply design
The author has designed one kind of new multi-channel power take-off valve power source using TOP249Y, its three groups outputs respectively are 5V/10A, 12.5V/4A, 7V/10A, circuitry as shown in Figure 3. This power source design’s request is: The input voltage scope to exchange 110V~240V, the output total output is 180W. Thus it can be seen, chooses TOP249Y to be able to satisfy the request.
3.1 periphery control circuit design
This electric circuit X may establish with the S end pipe nipple the TOP249Y limiting current as the internal maximum value; But may suppose the F end and the S end pipe nipple TOP249Y for the entire frequency working, the turn-on frequency is 132kHz.
Figure 2
Carries L and the cocurrent in the line examination inputs Ui end connection 2MΩ resistance R1 to be possible to carry on the line examination, because TOP249Y undervoltage electric current IUV is 50μA, has pressed electric current Iav is 225μA, therefore its undervoltage protection working voltage is 100V, the overvoltage protection working voltage is 450V, namely TOP249Y in this electric circuit’s DC voltage scope is 100~450V, once has surpassed this voltage range, TOP249Y automatic shut-off.
3.2 constant voltage feedback circuit design
Feedback loop’s form decided by output voltage’s precision that this power source use “light pair TL431″, it may the output voltage change control in ±1%, the feedback voltage take a sample by the 5V/12A out-port. Voltage feedback signal U0 after resistance voltage divider R9, R11 obtains the sampling voltage, with the TL431 in 2.5V voltage reference will carry on the comparison and the outlet error voltage, then the transmitted light pair changes TOP249Y control end electric current IC, adjusts output voltage U0 through the change dutyfactor to cause it maintains invariable again. Light pair’s another function is to coldly and carries on the isolation hotly. Feedback winding’s output voltage after D2, C2 rectification filter, may give in the light pair the receiving tube to provide the voltage. R4, C4 constitution peak voltage after the filter may cause the bias voltage, even if when the load is heavy, can also maintain stable, adjusting resistance R6 may change the output voltage the size.
3.3 high-frequency transformer designs
Because this power source’s output is big, therefore high-frequency transformer’s leakage inductance should be as far as possible small, generally with can satisfy the 132kHz turn-on frequency elected the manganese zinc ferrites, to be advantageous circles the system, the magnetic core shape may select EI or EE, transformer’s at the beginning, the secondary should the spaced winding system.
Because high-frequency transformer’s design needs to consider the massive incident cross-correlation variable, therefore calculates is more complex, to reduce designer’s work load, the American Power Company was TOP the Switch switching power supply’s high-frequency transformer design manufactures set of EXCEL electronic forms, the designer has been possible to apply the electronic forms design high-frequency transformer conveniently.
3.4 secondary output circuit design
The output rectification filter circuit constitutes by the rectification diode and the filter electric capacity. The rectification diode selects the Short base diode to be possible to reduce loses and eliminates the output voltage the ripple, but the Short base diode should add on the power big radiator; The capacitor should choose the low ESR 煹 edge generally т to unite the impedance 牭 male wrinkly gauze nettle N enhancement output voltage the filter effect, filters noise which the switch produces, usually should add the first-level LCC filter link again in rectification filter link’s behind.
3.5 protection circuit design
This power source the undervoltage which has besides power source control circuit TOP249Y itself, has pressed, overheated, protective measures and so on overflow, its periphery control circuit should also have certain protective measures. With D3, R12, Q1 may constitute 5.5V to press the examination protection circuit. Thus, when the 5V output voltage surpasses 5.5V, the D3 puncture causes the Q1 breakover, thus causes the light pair electric current to increase, then has increased control circuit TOP249Y control end electric current IC, finally then causes the output voltage through the internal adjustment to drop to the security value.
Figure 3
In order to prevent in the switching period, when TOP249Y shutdown the leakage inductance produces the peak voltage causes TOP249Y to damage, in the electric circuit designed has pressed the zener by the clip to manage VR1, to block the cushion protection network which diode D1, electric capacity C5, resistance R2, R3 were composed. This network when normal work, on the VR1 loss is very small, the leakage energy mainly undertakes by R2 and R3; But when start or overload, VR1 namely will limit internal MOSFET the drain electrode voltage, will cause it always to be in below 700V.
4 power source performance test and result analysis
According to the above design method, the author to used the TOP249Y design the multi-channel power take-off valve power source’s performance to carry on the test. The actual result indicated that this power source work when full-load conditions, the power source work’s biggest dutyfactor approximately is 0.4, power source’s efficiency approximately is 90%, the ripple voltage control, the voltage regulation precision and the power source working efficiency surpassed had formerly used the topology form switching power supply which the control circuit and the power switching valve established separately.
5 conclusions
Because the TOP249Y chip interior integration has the PWM controller, power switch MOSFET as well as many kinds of protection circuits, therefore uses the switching power supply which this chip designs to have the cost to be low, the periphery line is simple, the volume is small, efficiency and reliable higher characteristic, thus has the widespread application prospect in the power electronic installation. This article designs the switching power supply has applied in some frequency changer’s control circuit, and has made the good application progress.
