12v switching power supply schematic diagram download,scorpio horoscope career weekly,genuine free astrology reading aquarius,health horoscope capricorn 2012 - Test Out

14.01.2015
The schematic diagram below shows a simple trivial low-cost 12 volt DC 50W off-line SMPS switching power supply circuit. The unit has overcurrent, overtemperature and overvoltage protections, as well as passive inrush current limiting.
To safely test or troubleshoot this circuit it is recommended to power it via an isolation transformer or from an isolated AC source. This AC to DC power supply utilizes a flyback, which is the simplest SMPS converter topology. The initial start-up current for the PWM IC is provided by "bleeding" resistors R7, R8 that allow small current which charges the Vcc capacitor C7.
The secondary side feedback control loop uses a TL431 precision shunt regulator D1 as both the reference and an error amplifier. Thermal switch shuts down the power supply when temperature on the MOSFET heatsink exceeds 95-100 oC. The switching power supply, shown in the schematic, provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit.
A more modern circuit might use a single switching IC regulator, from National Semiconductor, Linear Technology, Maxim, or many other numerous vendors. A power supply circuit has a so-called composite resonance type switching converter equipped with a primary resonance circuit for forming a voltage resonance type converter at a primary side, and a secondary resonance circuit comprising a secondary winding and a secondary parallel resonance capacitor at a secondary side. I'll Show You All Switch Mode Power Supplies Repairing Secrets And How You Can Start Power Supply Repairing Work From The Comfort Of Your Home Using My Time-Tested Techniques That Works Throughout The Whole World!
That's why you need to know how to successfully repair any type of SMPS. What matters is that you must know how to repair, not just to understand the SMPS theories!
If you want to become a good SMPS repairer, you need this E-book that can help you get there. For The First Time Ever, I Am Revealing All My Switch Mode Power Supplies Repair Strategies To The Public! I developed this course to help shortcut your learning curve and save you the years of frustration and confusion that I went through while figuring out how to successfully repair more power supplies. You will know how to read the Schematic Diagram and the functions of each section in SMPS. You will understand the critical waveforms and voltages in many parts of the SMPS section thus helping you to easily diagnose the faults. Complete full colour photos (about 246 photos + diagrams) to go along with the instructions.
You will learn from my 11 important true case histories in SMPS repair that can practically help you in any SMPS repair. I've developed a bit of a reputation for explaining complex things in a way just about anybody can understand. The course can't do all the work for you, but if you're willing to follow my guidance and do what I suggest, you'll see your SMPS repairing skills start to grow very rapidly, and your income will grow right along with it. Do you know that we could have wasted lots of money simply by replacing the power IC without knowing it whether it has problem or not?
Now with the help of this simple UC3842 IC Tester, you can test whether the IC is good or bad.
Is a MUST HAVE report because this tester can be used to find out intermittent zener diode problem and also to locate the voltage of a zener diode if there is no marking on the zener diode.
Most other guide either charges hundreds of dollars for one-on-one email consultations or they simply don't include any support at all. If you have any questions, concerns or just plain need some words of motivation, you can contact me via email and will receive a personal response within about 24 hours.
I only respond to training questions from my paying members, so this truly is a valuable bonus as you'll never be left confused or wondering. Most people happily spend $5-$10 a day on expensive coffee drinks, and they have nothing to show for it at the end of the day. Click2sell.eu sells this product - they are a trusted online retailer specializing in digitally delivered products. What would you do if you have got a couple broken Switch Mode Power Supplies, a screw driver and some curiosity!? When I had a couple of them lying around, I cracked them open and after a few days, fixed some of them. I would like to ask you, as you seem to be much more experienced than me, what would it take to convert the +3.3v output to a +16v output? BIf you have a PC ATX power supply with a TL494 or similar IC’s it is very easy to change the values of a couple resistors and get a higher voltage. I am not completely sure if I can help you I do not have much experience rebuilding a power supply.
But I think for 40V output, you will need to rewind the transformers or even change the transformer altogether.. I do not know what part would be broken but I can point you in the right direction I guess. If you have the schematic diagram of 400wmercury ATX SMPS using the IC2003 similar to the one you have posted on this site ,please E-mail me! I have a Mercury 44W ATX SMPS and the schematic shown here and the circuit of that SMPS are actually the same. I trying to repair a PW Tecnoware FAL550FS , all outputs are dead except 5VDC which is working ok.There are no visible signs of damage and so far I have checked the caps,resistors,fuse which all seem to work right. I assume you tested the caps by checking them with your multimeter in resistance mode and you are shorting the GREEN wire with Ground (black).
If the meter gets stuck at a fixed resistance or even after shorting the cap, the meter shows infinite resistance, then the cap is probably faulty. If you have done this and made sure all resistors are OK, then try the rectifiers, both primary side and secondary side and then the switcher transistors.
I have been searching in vain for a datasheet of the 2003 PWM controller chip, about 2 years now but zero found. Do you think its possible to modify the +3,3V voltage line to 3,65V on a psu based on the 2003 chip?
Hey , Very nice blog I need a high current DC-DC converter , I have a punch of used ATX power supplies , Can I convert one of those to step down 48 Vdc instead of the 220 Vac ? I have a Mercury ATX switching power supply – 450w based on WelTrend WT7520 IC and its not powering on.
Also note that an offline single-transistor flyback converter generates internal voltages which may reach 600 V. This current sense voltage is applied through a spike filter to the current sense terminal of U3, where it is compared against the scaled down error signal at compensation pin 1.
Note that a flyback transformer operates as an inductor: it accumulates energy in the magnetic field during ON period of Q1.
The supply was constructed in 1984 and is variable frequency, as opposed to the pulse width modulator (PWM) controllers used today. There is no adjustable current limiter in this unit, although R1, R2, R3, Q2, R8, R9, C5 and Q4 set the current limit to approximately 10 amps. As a minimum, the D4 voltage reference could be replaced with a high precision LM4040 voltage reference which has excellent stability over temperature. The secondary side is equipped with active clamp means for stabilizing a DC output low voltage taken out from an intermediate tap of the secondary winding to control the conduction angle of an auxiliary main switching element in accordance with the level of the DC output low voltage, whereby the power loss due to the cross-regulation of the DC output low voltage can be reduced, and the power conversion efficiency can be enhanced. The switching power supply circuit as claimed in claim 1, wherein there are provided a plurality of constructing portions each of which comprises said second secondary parallel resonance circuit, said second DC output voltage generating means, said active clamp means and said second voltage-stabilizing control means. Field of the InventionThe present invention relates to a switching power supply circuit equipped to various types of equipment as a power supply source.2. You're here because you want to learn how to repair switch mode power supplies and you're not sure how to do it.
In fact, most people who try to start to repair SMPS, end up quitting because they don't get fast results. This is because they're focusing on the wrong information which is on the study of too much SMPS theories. Here screenshot preview of the ebook "Troubleshooting & Repairing Switch Mode Power Supplies". You see, there's no way I can ethically promise you results, because I have no idea if you'll follow these steps to learn how to repair power supplies. In other words, the Switch Mode Power Supplies Repair Guide tells you what you need to do, and shows you exactly how, without leaving you to imagine what to do.
Many repair technicians will not use back the power IC whenever they found problem like a shorted power FET in the power primary side. With the aid of photos and full details explanation, it will not take you long to build this powerful zener diode tester. I've made this course inexpensive enough so that anyone who is serious about repairing SMPS can afford it. I'm confident that the wealth of information that you will receive and the number of times you'll refer back to this E-book year after year will prove its value.
Take up to eight weeks to examine and use the information, tips and techniques in "Troubleshooting and Repairing Switch Mode Power Supplies E-book". All you need to do is click on the link below, which will take you to the order page, and then you just enter your information in. Don't forget with the purchase of my eBook you get my email support to help you with any question you may have on SMPS.
I found some inductors to add to the output filter, but couldn't find any for the EMI filter at input. I am looking for this IC not able to find out any ware or equivalent the following letter mentioned on that IC.
You can find most of the modification needed to change the voltage of a standard power supply on the net.
Good work, I have a question regarding the output inductor, anyone knows his number to get it, or preferably buy?. Start by checking the two small blue(most of the time) capacitors connected across Line, Neutral and GND. The only difference is that the output filter coils are not present and the input EMI filter are also absent.


Check the voltage across the cap and discharge it by using a resistor or simply shorting it (if the voltage is really low). Most of the time you won’t have to desolder the caps as the secondary circuit mostly do not affect the caps.
You can however salvage the parts like inductors, transformers and caps and build your own circuit based on guide from TI. If you need to get lower ripple, you may put an additional output capacitor or an LC filter outside of the feedback loop.
Don't try to play with this circuit unless you are of a legal age, understand power electronics and know how to deal safely with high voltage. The input section includes a fuse, EMI filter, inrush current limiting NTC resistor R1, a full bridge rectifier CR1, and a DC bus filter capacitor C2. When Q1 turns on, the DC bus voltage is applied across the transformer T1 primary winding, current through the transformer primary ramps up and energy is accumulated in the transformer's magnetic field. An optocoupler U1 feeds the current proportional to the error signal across the transformer galvanic isolation boundary back to the primary PWM. As you can see, the design is very similar to that of a linear power supply, except that L1, and D1 have been added, and U1 operates in a switching mode as a comparator with a small amount of hystersis. My personal preference for a modern design is to use a PWM controller IC with an external MOSFET transistor since discrete TO-220 style MOSFETs can be obtained with 400 volt ratings and 80 amperes of current capability, making the supply virtually indestructable when linked with the protection circuits built into the PWM chip. Description of the Related ArtThe applicant of this application previously proposed a technique of constructing a composite resonance type converter as a switching power supply circuit by combining a voltage resonance type converter of one stone at a primary side and a half-wave rectifying type voltage resonance circuit at a secondary side, providing an active clamp circuit at the secondary side and stabilizing the DC output voltage thereof by controlling the conduction angle of the switching element of the active clamp circuit.FIG.
Or you know the basics but are struggling after hearing all the claims as to how easy it was.
The title of the ebooks are LCD Monitor Repair, Testing Electronic Components and Find Burnt Resistor Value.
They read all these stories about electronic repairers being able to repair SMPS and making money, and thus they're inspired to give it a shot themselves. I've made it as easy as humanly possible for you by giving you a proven blueprint for success.
For the first 6 months of your training I will literally hold your hand and personally make sure that you are doing everything properly and efficiently. That's less than the cost of a few nice dinners in exchange for a lifetime of knowing how to successfully repair SMPS.
You'll be surprised how little work and effort is actually involved for you to start repairing SMPS and have lots of fun in the process!
That’s up to 60 day to put these valuable strategies to work on your SMPS in your own home.
If you want to increase your SMPS repair rate, you've got to do something different than what you've been doing all this time.
But one bad thing about SMPS repairs is that there aren’t any good resources out there on the web.
The EMI filter and output filters are usually left out, and the components heavily underrated. The pin of my probe on CH1 is connected to C1 while the pin of my second probe on CH2 is connected to C2. The portion of the board under that zener diode was in burnt condition by doing cold check itself.
This project is a modification of a 24V circuit that I've designed many years ago as a consultant for a small company. If accurate regulation of the output is not required, the feedback can be taken from the bias voltage at C9 and fed via a divider into feedback pin 2.
In order to store energy efficiently with minimal physical size, a non-magnetic gap is needed in series with a high permeability magnetic core material. 10 is a circuit diagram of a conventional switching power supply circuit which can be constructed on the basis of the invention previously proposed by the applicant of this application.In the power supply circuit shown in FIG.
They'd rather keep you in the dark by telling you to "replace this or that" but do not actually tell you the right way on how to locate the bad parts. That won't be the case here, because I'm including the best "how to" guide you've ever seen.
Click below to order, so you can get started on repairing Switch Mode Power Supplies right away! The repair techniques in this course are the reasons why I can repair so many types of SMPS, and they can help you do the same. Although the power supply seems to work (outputting the correct voltages) I’m not able to measure the PWM or display it on my scope. So, I want to replace that Zener Diode, but I don’t know what value diode we should replace with. That company wanted a plug-in replacement to a cheap off-the-shelf AC to DC power supply, which had a long lead time.
When Q1 turns off, the energy stored in the magnetic field causes the voltages across all winding to reverse polarity. Flyback transformer design usually uses ferrite cores with a physical gap, or powdered metal cores with an inherently present distributed gap.
10, a full-wave rectifying circuit comprising a bridge rectifying circuit Di and a smoothing capacitor Ci is equipped as a rectifying and smoothing circuit to which commercial alternating power (alternating input voltage VAC) is input to achieve a DC input voltage, whereby the rectified and smoothed voltage Ei corresponding to the once level of the alternating input voltage VAC is achieved.At the primary side of the power supply circuit, a self-excited type is constructed as a voltage resonance type converter circuit which carries out a single-end operation on the basis of a one-stone switching element Q1. You'll be able to repair many SMPS after reading and following the step by step guide in this E-book. This course will literally shave years off your learning curve, and help you in repairing many SMPS that can make you lots of money. Once you have used these strategies on SMPS's, I’m confident that you’ll NEVER want to send it back! That is why I decided to make a series of posts with my repair notes, schematics and stuff I have learned through opening those bricks. By the time I've completed the design and built a proto, they found the off-the-shelf part elsewhere in stock. As a result, output rectifiers D4 and D7 conduct and the stored energy is transferred to the output and to the bias circuit. With a PWM regulator, the switching frequency is constant and will produce spurs only at known discrete frequencies rather than spurs at all frequencies. Once the converter is started, the bias for the control PWM comes from the bias winding of the transformer. The Darlington-connected pass transistor block in the schematic is there twice (in parallel) for robustness. For example, the switching frequency fs is set to 66 KHz by the series resonance circuit.A route for clamp current flowing when the switching element Q1 is turned off is formed by a clamp diode DD1 inserted between the base of the switching element Q1 and the cathode (the earth at the primary side) of the smoothing capacitor Ci.
That means you won't have to wait in order to begin using these strategies in your repair business. The collector of the switching element Q1 is connected to one end of the primary winding N1 of the insulating converter transformer PIT, and the emitter thereof is grounded.A parallel resonance capacitor Cr is connected between the collector and emitter of the switching element Q1 in parallel. But you are not allowed to republish the content of this page anywhere or use it for commercial purposes without my permission.
In this case, a primary series resonance circuit of the voltage resonance type converter is formed by the capacitance of the parallel resonance capacitor Cr itself and the leakage inductance L1 of the primary winding N1 side of the insulating converter transformer PIT.The insulating converter transformer PIT transmits the switching output of the switching element Q1 to the secondary side. The insulating converter transformer PIT is equipped with an EE-type core comprising two E-type cores of ferrite material or the like which are assembled such that both the magnetic legs thereof are confronted to each other, and the primary winding N1 and the secondary winding N2 are wound around the center magnetic leg of the EE-type core by using a divisional bobbin so as to be separated from each other.
All of the tips, techniques and secrets are revealed in a step-by-step, easy to understand format.
Further, the EE-type core is assembled so that a gap is formed in the center magnetic leg thereof, whereby loose coupling based on a required coupling coefficient is achieved.One end of the primary winding N1 of the insulating converter transformer PIT is connected to the switching element Q1, and the other end thereof is connected to the anode of the smoothing capacitor Ci (rectified and smoothed voltage Ei). All coils in this design have to be made of wire with two or more layers of Teflon insulation to assure reinforced insulation between primary and secondary.
Accordingly, an alternating voltage having the period corresponding to the switching frequency occurs at the primary winding N1 when the switching output of the switching element Q1 is supplied to the primary winding Ni.Further, at the secondary side of the insulating converter transformer PIT, an alternating voltage induced by the primary winding N1 is generated at the secondary winding N2. In this case, a secondary parallel resonance capacitor C2 is connected to the secondary winding N2 in parallel, so that a parallel resonance circuit is formed by the leakage inductance L2 of the secondary winding N2 and the capacitance of the secondary parallel resonance capacitor C2. The parallel resonance circuit sets the alternating voltage induced in the secondary winding N2 to a resonance voltage, so that a voltage resonance operation can be achieved at the secondary side. 10 to generate and output a low secondary DC output voltage E02.In the power supply circuit, an active clamp circuit is equipped to the secondary side. That is, an auxiliary switching element Q2 of MOS-FET, a clamp capacitor C3 and a clamp diode DD2 are equipped as the secondary active clamp circuit. Further, a drive winding Ng1, a capacitor Cg1 and a resistor Rg1 are equipped as a driving circuit system for driving the auxiliary switching element Q2.A clamp diode DD2 is connected between the drain and source of the auxiliary switching element Q2 in parallel. As a connection manner, the anode of the clamp diode DD2 is connected to the source, and the cathode is connected to the drain.The drain of the auxiliary switching element Q2 is connected to the connection point between the tap output line of the secondary winding N2 and the anode of the rectifying diode D02 through a clamp capacitor C3. Further, the source of the auxiliary switching element Q2 is connected to the earth at the secondary side.Accordingly, the secondary active clamp circuit is constructed by connecting the clamp capacitor C3 to the parallel connection circuit comprising the auxiliary switching element Q2 and the clamp diode DD2 in series. The circuit thus formed is further connected to the secondary winding N2 in parallel.As the driving circuit system of the auxiliary switching element Q2, a series connection circuit of a capacitor Cg1, a resistor Rg1 and a drive winding Ng1 is connected to the gate of the auxiliary switching element Q2 as shown in FIG. The series connection circuit forms the self-excited driving circuit for the auxiliary switching element Q2. That is, a signal voltage VGS from the self-excited type driving circuit is applied to the gate of the switching element Q2 to perform the switching operation.
In this case, the drive winding Ng1 is formed at the end portion side of the secondary winding N2, and the number of turns in this case is set to 1T (turn), for example.Accordingly, the voltage induced by the alternating voltage achieved at the primary winding N1 occurs at the drive winding Ng1. Further, in this case, voltages achieved at the secondary winding N2 and the drive winding Ng1 are opposite in polarity because of the relationship of the winding direction between the windings N2 and Ng1.In this embodiment, PWM control is carried out on the switching operation of the auxiliary switching element Q2 by a control circuit 1 equipped to the secondary side.
That is, the secondary DC output voltage E01, E02 is supplied to the control circuit of an error amplifier, and the control circuit 1 applies the DC control voltage corresponding to E01, E02 to the gate of the auxiliary switching element Q2 to control the conduction angle of the auxiliary switching element Q2, whereby the DC output voltage is stabilized with respect to variations of the alternating input voltage VAC and the load power Po. 11 shows the operation waveforms of the respective parts at the alternating input voltage VAC of 100V and the load power Po of 200 W. 12 shows the operation waveforms of the respective parts under no load and at the alternating input voltage VAC of 100V. 11 and 12 that the conduction angle (TON period) of the auxiliary switching element Q2 is controlled in accordance with the variation of the load power Po.FIG. On the basis of this construction, the active clamp means for stabilizing the DC output low voltage taken from the intermediate tap of the secondary winding is provided at the secondary side, and the conduction angle of the auxiliary main switching element is controlled in accordance with the level of the DC output low voltage, whereby the power loss due to the cross regulation of the DC output low voltage can be reduced and the power conversion efficiency can be enhanced.BRIEF DESCRIPTION OF THE DRAWINGSFIG.


1 is a circuit diagram showing the construction of a switching power supply circuit according to an embodiment of the present invention;FIG. 2 is a cross-sectional view showing the construction of an insulating converter transformer;FIGS. 4 is a waveform diagram showing the operation of the main part in the power supply circuit of the embodiment of the present invention;FIG. 5 is a waveform diagram showing the operation of the main part in the power supply circuit of the embodiment of the present invention;FIG. 6 is a diagram showing characteristics of the power supply circuit of the embodiment with respect to variation of load power;FIG.
7 is a diagram showing characteristics of the power supply circuit of the embodiment with respect to variation of load power;FIG. 8 is a circuit diagram showing the construction of a switching power supply circuit according to another embodiment of the present invention;FIG. 9 is a circuit diagram showing the construction of a switching power supply circuit according to another embodiment of the present invention;FIG. 10 is a circuit diagram showing the construction of a conventional switching power supply circuit;FIG. 11 is a waveform diagram showing the operation of the main part of the conventional switching power supply circuit;FIG.
12 is a waveform diagram showing the operation of the main part of the conventional switching power supply circuit;FIG. 13 is a diagram showing the characteristics of power conversion efficiency and conduction angle control with respect to variation of load power in the conventional power supply circuit; andFIG.
1 shows the construction of a switching power supply circuit according to an embodiment of the present invention.In the power supply circuit shown in FIG. A starting resistor RS is inserted to achieve the base current at the starting time from a rectifying and smoothing line.A parallel resonance capacitor Cr is connected in parallel between the collector and emitter of the switching element Q1. A primary parallel resonance circuit of the voltage resonance type converter is formed by the capacitance of the parallel resonance capacitor Cr itself and the leakage inductance L1 of the primary winding N1 side of the insulating converter transformer PIT.An orthogonal control transformer PRT shown in FIG.
1 is a saturable reactor around which a resonance current detecting winding ND, a driving winding NB and a control winding NC are wound. The orthogonal control transformer PRT is used to drive the switching element Q1 and perform voltage-stabilizing control.
1, the resonance current detecting winding ND and the driving winding NB are wound around the orthogonal control transformer PRT, and also the control winding NC is wound around the orthogonal control transformer PRT in the direction orthogonal to the winding direction of the resonance current detecting winding ND and the driving winding NB.In the orthogonal control transformer PRT, the switching output achieved at the resonance current detecting winding ND is induced in the driving winding NB through trans-coupling, whereby drive current is output from the series resonance circuit (NB, CB) forming a self-excited oscillation circuit through the base current limiting resistor RB to the base of the switching element Q1, whereby the switching element Q1 carries out the switching operation at the switching frequency determined on the basis of the resonance frequency of the series resonance circuit. 2, the insulating converter transformer PIT is equipped with an EE-type core comprising two E-type cores CR1, CR2 of ferrite material which are assembled so that the magnetic legs thereof are confronted to each other, and the primary winding N1 and the secondary winding N2 are wound around the center magnetic leg of the EE-type core while they are separated from each other by using a dividing bobbin B. Further, the center magnetic leg is designed to have a gap G therein, thereby achieving loose coupling based on a required coupling coefficient.The gap G can be formed by making the center magnetic leg of each of the E-type cores CR1, CR2 shorter than the two outer magnetic legs thereof. 1, the winding-starting end portion of the primary winding N1 of the insulating converter transformer PIT is connected to the collector of the switching element Q1, and the winding-ending end portion is connected to the anode of the smoothing capacitor Ci (rectified and smoothed voltage Ei) through the detecting winding ND. Accordingly, the switching output of the switching element Q1 is supplied to the primary winding N1, thereby generating an alternating voltage having the period corresponding to the switching frequency.The alternating voltage induced by the primary winding N1 occurs in the secondary winding N2 at the secondary side of the insulating converter transformer PT. In this case, the secondary parallel resonance capacitor C2 is connected to the secondary winding N2 in parallel, so that a first parallel resonance circuit is formed by the leakage inductance L2 of the secondary winding N2 and the capacitance of the secondary parallel resonance capacitor C2. The parallel resonance circuit sets the alternating voltage induced in the secondary winding N2 to a resonance voltage, and thus the voltage resonance operation is performed at the secondary side. That is, the power supply circuit of this embodiment has the construction of a “composite resonance type switching converter” in which a parallel resonance circuit for setting the switching operation to a voltage resonance type is provided at the primary side, and also a parallel resonance circuit for achieving the voltage resonance operation is provided at the secondary side.At the secondary side of the power supply circuit thus formed, a rectifying diode D01 and a smoothing capacitor C01 is connected to the secondary parallel resonance circuit comprising the secondary winding N2 and the secondary parallel resonance capacitor C2 in a connection style shown in FIG. 1 to thereby form a half-wave rectifying circuit, and a secondary DC output main voltage E01 is mainly generated by the half-wave rectifying circuit (D01, C01). Accordingly, the inductance LB of the driving winding NB is variable, and the resonance frequency of the series resonance circuit in the self-excited oscillation driving circuit, that is, the switching frequency of the switching element Q1 is variably controlled, thereby stabilizing the DC output main voltage E01.Here, when the switching frequency is variably controlled, the period TOFF during which the switching element Q1 is off is set to a fixed value, and under this condition, the period TON during which the switching element Q1 is on is variably controlled. 3A, the mutual inductance M is equal to +M, and when it is equivalent to the circuit shown in FIG. 1, when the alternating voltage achieved at the secondary winding N2 has positive polarity, the rectified current flows in the secondary rectifying diode (D01) in the half-wave rectifying circuit of the secondary side, and thus this operation can be regarded as an operation mode of +M (forward operation).The polarities of the primary winding N1 and the secondary winding N2 of the insulating converter transformer PIT may be the additive polarity coupling or the subtractive polarity coupling.
Further, the winding directions of the primary winding N1 and the secondary winding N2 are set to be the same or opposite to each other. The number of turns of the winding portion between the tap of the secondary winding N2 and the earth at the secondary side is set to N3. Further, a secondary parallel resonance capacitor C4 is connected to the winding N3 between the tap output line and the earth at the secondary side in parallel, so that a second parallel resonance circuit is formed by the leakage inductance L3 of the winding portion having the winding number N3 and the capacitance of the secondary parallel resonance capacitor C4.Further, a rectifying diode D02 and a smoothing capacitor C02 are connected to the secondary parallel resonance circuit in the connection manner as shown in FIG.
An auxiliary DC output voltage, that is, a secondary DC output low voltage E02 is generated by the half-wave rectifying circuit (D02, C02).
The secondary DC output low voltage E02 is set to about 12V, for example.In the power supply circuit described above, an active clamp circuit is provided at the secondary side.
That is, an auxiliary switching element Q2 of MOS-FET, a clamp capacitor C3 and a clamp diode DD2 of a body diode are equipped as the secondary active clamp circuit.
Further, a drive winding Ng1, a capacitor Cg1 and a resistor Rg1 are equipped as a driving circuit system for driving the auxiliary switching element Q2.The clamp diode DD2 is connected between the drain and source of the auxiliary switching element Q2 in parallel. The connection style is set so that the anode of the clamp diode DD2 is connected to the source and the cathode thereof is connected to the drain.The drain of the auxiliary switching element Q2 is connected to the connection point between the tap output line of the secondary winding N2 and the anode of the rectifying diode D02 through the clamp capacitor C3.
The source of the auxiliary switching element Q2 is connected to the earth at the secondary side.Accordingly, the active clamp circuit is constructed by connecting the clamp capacitor C3 to the parallel connection circuit of the auxiliary switching element Q2 and the clamp diode DD2 in series.
The circuit thus formed is further connected to the winding portion (winding N3) extending from the intermediate tap of the secondary winding N2 to the earth at the secondary side in parallel.Further, as shown in FIG. 1, the series connection circuit of the resistor Rg1, the capacitor Cg1 and the drive winding Ng1 is connected to the gate of the auxiliary switching element Q2 as the driving circuit system for the auxiliary switching element Q2.
The series connection circuit forms a self-excited driving circuit for the auxiliary switching element Q2. That is, the signal voltage from the self-excited driving circuit is applied to the gate of the switching element Q2 to perform the switching operation.In this case, the drive winding Ng1 is formed at the winding-start end portion side of the secondary winding N2, and the number of turns thereof is set to 1T (turn). Accordingly, a voltage induced by the alternating voltage achieved in the primary winding N2 occurs in the drive winding Ng1. In this case, the voltages having the opposite polarities are achieved at the secondary winding N2 and the drive winding Ng1 in view of the winding-direction relationship therebetween.
The operation of the drive winding Ng1 is guaranteed if the number of turns thereof is equal to 1T, however, it is not limited to this value.In this embodiment, the switching operation of the auxiliary switching element Q2 is subjected to the PWM control by a control circuit 1B equipped at the secondary side. 7 shows the characteristics of the switching frequency fs and resonance voltage V1 of the switching element Q1 with respect to variation of the load power Po.As is apparent from FIGS. 4 and 5, with respect to the main switching element Q1, the switching frequency fs and the conduction angle TON are subjected to composite control, and with respect to the auxiliary switching element Q2, the conduction angle (TON?) is controlled.As is apparent from the comparison between FIGS. 8 shows a switching power supply circuit according to a second embodiment of the present invention.FIG. 8 shows a case where the switching element Q1 at the primary side is formed of MOS-FET and a separate excitation type oscillating circuit based on IC is provided in connection with the switching element Q1. The drain of the switching element Q1 of MOS-FET is connected to the anode of the smoothing capacitor Ci through the primary winding N1 of the insulating converter transformer PIT, and the source of the switching element Q1 of MOS-FET is connected to the earth at the primary side.A parallel resonance capacitor Cr is connected between the drain and source of the switching element Q1 in parallel. A primary parallel resonance circuit is formed by the capacitance of the parallel resonance capacitor Cr and the leakage inductance achieved at the primary winding N1 of the insulating converter transformer PIT. For example when a power source voltage is applied to the switching driving portion 10 through the starting resistor Rs at the power source turn-on time, the switching driving portion 10 is actuated.The oscillation circuit 2 of the switching driving portion 10 carries out the oscillation operation having the frequency based on a control signal from the control circuit 1A to output an oscillation signal.
The oscillation signal is converted to a drive voltage in the drive circuit 3, and output to the gate of the switching element Q1, whereby the switching element Q1 is allowed to carry out the switching operation based on the oscillation signal generated in the oscillation circuit 2.
8 (the winding portion between the first tap of the secondary winding N2 and the earth at the secondary side is represented by N3 and the winding portion between the second tap of the secondary winding N2 and the earth at the secondary side is represented by N4).Like the case of FIG. 1, a parallel resonance capacitor C4 is connected to the winding N3 in parallel, and a parallel resonance circuit is formed by the leakage inductance of the winding N3 and the capacitance of the secondary parallel resonance capacitor C4, and further a rectifying diode D02 and a smoothing capacitor C02 are connected to each other in the connection manner shown in FIG.
The secondary DC output low voltage E02 is set to about 12V.PIT, Like the circuit construction for the winding N3, a parallel resonance capacitor C5 is connected to the winding N4 in parallel, and a parallel resonance circuit is formed by the leakage inductance of the winding N4 and the capacitance of the secondary parallel resonance capacitor C5.
Further, a rectifying diode D03 and a smoothing capacitor C03 are connected to each other in the connection manner shown in FIG. Further, a driving circuit system for driving the auxiliary switching element Q2 comprises a drive winding Ng1, a capacitor Cg1 and a resistor Rg1 The active clamp circuit is constructed by connecting the series connection circuit of the auxiliary switching element Q2 and the clamp capacitor C3 to the winding N3 in parallel.The switching operation of the auxiliary switching element Q2 is subjected to the PWM control by the control circuit 1B. That is, the secondary DC output low voltage E02 is supplied to the control circuit 1B of the error amplifier, and the controller 1B applies the corresponding DC control voltage to the gate of the auxiliary switching element Q2 to control the conduction angle of the auxiliary switching element Q2, whereby the DC output low voltage E02 is stabilized with respect to the variations of the alternating input voltage VAC and the load power Po.The active clamp circuit for the DC output low voltage E03 line is equipped with an auxiliary switching element Q3 of MOS-FET, a clamp capacitor C6 and a clamp diode DD3 of a body diode. A driving system for the auxiliary switching element Q3 comprises the drive winding Ng1 (commonly used with the driving system of the auxiliary switching element Q2), a capacitor Cg2 and a resistor Rg2.
The active clamp circuit is constructed by connecting the series connection circuit of the auxiliary switching element Q3 and the clamp capacitor C6 to the winding N4 in parallel.Further, the switching operation of the auxiliary switching element Q3 is subjected to the PWM control by a control circuit iC. That is, the secondary DC output low voltage E03 is supplied to the control circuit iC of the error amplifier, and the control circuit iC applies the corresponding DC control voltage to the gate of the auxiliary switching element Q3 to control the conduction angle of the auxiliary switching element Q3, whereby the DC output low voltage E03 is stabilized with respect to the variations of the alternating input voltage VAC and the load power Po.FIG.
9 shows a switching power supply circuit according to a third embodiment of the present invention. In this embodiment, the construction of the primary side of the insulating converter transformer PIT is the same as shown inFIG. With respect to the construction of the secondary side, the connection manner of each element is the same as the embodiment of FIG.
The drive winding Ng1 is formed at the winding-start end portion of the winding N3 by 1T, for example. This embodiment is suitably applied to a case where the output current of the DC output low voltage E02, E03 is equal to a large current value such as 2 A or more.The embodiments shown in FIGS. 8 and 9 are directed to a case where two or more pairs of DC output low voltages (E02, E03, . For example, the main switching element Q1 is not limited to the bipolar transistor, and it may be formed of MOS-FET, BJT, IGBT or the like.
Further, the voltage resistance of the auxiliary switching element can be reduced from 400V to 50V. From this effect, enhancement of the switching characteristics and reduction of the cost of the power supply circuit can be promoted.



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