CN109586582B

CN109586582B - Power supply system

Info

Publication number: CN109586582B
Application number: CN201811441297.XA
Authority: CN
Inventors: 王保均
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2018-11-29
Filing date: 2018-11-29
Publication date: 2020-09-15
Anticipated expiration: 2038-11-29
Also published as: CN109586582A

Abstract

Compared with the existing power module applying a royer circuit, the power module removes an input filter capacitor, an output rectifying circuit and a filter circuit; the power system can meet the requirement of electromagnetic compatibility standard on the premise that the removed power system is externally connected by a client and the distance between the two capacitors and the power module is less than or equal to lambda/11, so that the system loss caused by capacitor failure can be solved; the removed output rectifying circuit is externally connected in a power supply system of the power supply system through a client, so that the expansion of the application of the client can be realized, namely, one-way, positive and negative two-way and double-voltage output can be realized through one module. The invention has great popularization value.

Description

Power supply system

Technical Field

The present invention relates to a power module, and more particularly, to a power module using a royer circuit.

Background

Existing self-excited push-pull converters are generally classified into two categories: royer circuits and weissen circuits.

Royer circuits were from the self-oscillating push-pull transistor single-transformer dc-to-dc converter invented by Royer (g.h.royer) in 1955, often referred to simply as Royer circuits, which are also the beginning of implementing high-frequency switching control circuits; in 1957, a self-excited push-pull double-transformer circuit is invented in the United states checkup (Jen Sen, most of documents are translated into 'Heilon'), and then the circuit is called as a self-oscillating Jensen circuit and a self-excited push-pull Jensen circuit, and most of documents are called as the Heilon circuit; both circuits, which will be referred to later as self-excited push-pull converters, are described on pages 67 to 70 of the "principle and design of switching power supplies" from the electronic industry publishers, ISBN number 7-121 and 00211-6. The main forms of the circuit are the royer circuit and the weisen circuit.

Fig. 1 shows a schematic diagram of a typical application of a royer circuit, fig. 2 shows another schematic diagram of a royer circuit, which corresponds to fig. 9 of another chinese application No. 201210174076.7 (abbreviated as background 1) of the present inventor, which is named as "a short-circuit protection method for a self-excited push-pull converter", fig. 2 differs from fig. 1 in that a capacitor in a starting circuit is connected differently, a capacitor C1 in fig. 1 is directly connected in parallel with a bias resistor R1, and such a connection capacitor C1 can be omitted in many cases; the capacitor C1 in FIG. 2 is connected between the center tap of the feedback winding and the input ground, such connection method can solve the problem of impact of short circuit on the push-pull triode during startup of the capacitor C1 in FIG. 1, so as to realize soft start, the improved applicant has applied for the utility model ZL03273278.3 in 2003, which is actually disclosed in FIGS. 2-18 on page 41 of Power conversion technology of the people's post and telecommunications Press, and also disclosed in FIGS. 2-27 on page 56, the ISBN number of the book is 7-115-04229-2/TN 353. And the inventor of the present application in paragraph 0029 to paragraph 0035 of the background 1 granted document, and fig. 3-1 to fig. 3-7 of the attached drawings, gives the evolution of the bias circuit of the existing royer or wellson circuit, and also gives the detailed working principle, which proves that the capacitor C1 in the starting circuit has no influence on the steady-state operation of the circuit after the successful start-up by adopting the connection of fig. 1 or fig. 2.

The self-excited push-pull converter works in an open loop mode, so that the frequency response is good, and the input impedance of the self-excited push-pull converter in a small-signal state is positive in a small-signal model. The small-signal input impedance of other various closed-loop operating switching power supplies is negative, that is, when the input voltage rises for some reason, the consumption current of other switching power supplies is reduced to maintain the output power unchanged. Just because the small signal input impedance of the self-excited push-pull converter is positive, the number of elements is small, the reliability is extremely high, and the parallel connection or cascade connection use is very simple, the self-excited push-pull converter is difficult to replace by other circuit topologies in a long time in the future and is manufactured into a power module to be directly sold as a device, two common methods for manufacturing the power module are adopted, one method is plastic package, the finished power module is similar to an integrated circuit, epoxy resin mixtures including filling particles and curing agents are adopted to be molded in a mold at high temperature, and the plastic package power module is convenient to use; the other method is encapsulation, a circuit board is placed in a shell, and polyurethane two-component mixture or silica gel is filled in the shell for molding, so that the circuit board is generally inconvenient to manufacture into a patch-type device and is slightly inconvenient to use in engineering.

At present, the power supply module produced by applying the self-excited push-pull converter has the global annual output of more than 1 hundred million, the output power of the power supply module is mostly 1W, the power supply module is commonly called as a micro-power supply module, and manufacturers comprise Japan village companies, American Dezhou instruments, German RECOM companies, Taiwan MINMAX companies and the like, and domestic dozens of companies, and the following technical bottlenecks exist.

The power module is applied to vibration occasions, such as automobiles, motor cars and high-speed rails, failure often occurs, particularly in plastic package type power modules, the power module is sealed and molded and can only be integrally replaced, the failure probability is not high, the failure rate of the installation in use for one year is about one thousandth, namely 1000ppm, which is unacceptable in the automobile industry, the expectation of the automobile industry is zero defect, the failure is higher in the first year according to a bathtub curve in the failure mechanism, the failure rate of the automobile industry in the first year is expected to be below 8ppm, namely eight parts per million, and meanwhile, the overall failure rate in 10 years also meets below 8 ppm.

The failure rate of products produced by the most advanced process at home and abroad can only reach about 300ppm, but only 8ppm can be accepted by customers, once defective products are delivered, the defective products can be widely applied to the fields of automobiles, rail transportation, mechanical equipment, industrial communication and the like, if the consequences caused by accidents are serious, a manufacturer can only carry out detection before online, and can only carry out plate installation after 100 percent of qualified products exist, but the defective products still exist, therefore, the automobile manufacturer and a micropower power module manufacturer want various methods, if the brand is replaced by the brand which is ranked in the front of the global ranking, the problems still occur in the use of users. The cost of after-sale payment is extremely high, and the resulting claims are also very high.

Because the micropower power supply module is used in the environment with severe temperature and humidity environments such as automobiles, the product is required to be sealed or encapsulated, the environmental adaptability is improved, and the power supply module is damaged during disassembly after the product fails, so that failure analysis is extremely difficult, final improvement cannot be further performed, and zero defect is realized.

In addition, the power module application occasion is the five-flower eight-door, also can have very much demand to its input voltage, output path number, isolation withstand voltage and encapsulation etc. and to power module manufacture factory, all integrate output rectifier circuit inside power module at present, this means that the product of single output and two way output needs design manufacturing separately, this can make power module manufacture factory's model double, leads to the increase of administrative cost and stock pressure.

Disclosure of Invention

In view of this, the technical problem to be solved by the present invention is to provide a power module, which can reduce failure rate, reduce social cost loss, and reduce management cost and inventory pressure of manufacturers when applying a royer circuit.

Compared with the existing power module applying the Royer circuit, the power module has the advantages that the input filter circuit, the output rectifying circuit and the output filter capacitor are eliminated; the basis for removing the input filter circuit and the output filter capacitor is that the client can still realize related functions through external connection, and under the premise that the distance between the two capacitors and the power module is less than or equal to lambda/11 (wherein lambda is the wavelength corresponding to the working frequency of the power module, namely the light speed is divided by the working frequency of the power module), the power system can break through the cognition of the prior art and realize the requirement of meeting the electromagnetic compatibility standard, thereby solving the problems of customer complaints, claim claims and life and property loss of users caused by the failure of the micropower power module; and the output rectifying circuit is removed, the expansion on the client application can be realized through the external output rectifying circuit, namely, the single-path, the positive and negative double-path and the double-voltage output can be realized through one module.

Based on the inventive concept, the technical scheme of the invention for solving the technical problems is as follows:

a power module, characterized by: the transformer does not comprise an input filter capacitor and an output filter capacitor, and the other at least comprises four terminals, namely an input positive terminal, an input ground and two output terminals, and comprises a starting circuit, a triode TR1, a triode TR2, a main transformer B1 and a primary winding N_P1And N_P2Feedback winding N_B1And N_B2And at least one secondary winding N_S1(ii) a The starting circuit at least comprises two terminals, a starting input end and a starting output end, the starting input end is connected with the input positive terminal of the power module, and the starting output end is connected with the feedback winding N_B1And N_B2The center tap of (1); the emitting electrodes of the transistors TR1 and TR2 are connected to the input ground of the power supply module, and the collecting electrodes are respectively connected with the primary winding N_P1And N_P2Two ends and bases of the transformer are respectively connected with a feedback winding N_B1And N_B2Two ends of (a); primary winding N_P1And N_P2The center tap of the power module is connected with the input positive terminal of the power module; secondary winding N_S1Are connected at both endsTwo output terminals of the power module.

As a specific embodiment of the starting circuit, the starting circuit includes a current supply device and a capacitor C1, the current supply device has one end as a starting input end and the other end as a starting output end, the capacitor C1 is connected in parallel with the current supply device, and the current supply device is a resistor or a constant current source device.

As another specific embodiment of the starting circuit, the starting circuit further includes a third terminal, and the starting circuit includes a current supply device and a capacitor C1, the current supply device has one terminal as a starting input terminal, the other terminal as a starting output terminal, the third terminal is connected to the input ground, one terminal of the capacitor C1 is connected to the starting output terminal, the other terminal of the capacitor C1 is a third terminal, and the current supply device is a resistor or a constant current source device.

For the condition that the client wants the power module to carry out output rectification, on the basis of the technical scheme: secondary winding N_S1And a diode D1 is connected between any one end of the diode and the output terminal of the power supply module to which it is connected.

As a first improvement of the above technical solution, the magnetic core of the main transformer B1 is composed of a main part and a local part, the main part and the local part are made of the same material, and have different sectional areas; or the main part and the local section area are the same, and the materials are different.

As a second improvement of the above technical solution, a capacitor C4 is connected between the collector of the transistor TR1 and the collector of the transistor TR 2.

As a preferable mode of the second improvement of the above technical solution, a capacitance value of the capacitor C4 is less than 1000 pf.

In addition, the technical scheme of the power supply system applying the power supply module provided by the invention is as follows:

a power supply system using the power supply module is characterized in that: an input filter capacitor C2 is connected in parallel between an input positive terminal and an input ground of the power module, an output filter capacitor C3 is connected in parallel between two output terminals, and C3 is connected in parallel with the output terminals through a rectifier diode if necessary, the distance between the input filter capacitor C2 and the output filter capacitor C3 and the power module is less than or equal to lambda/11, and lambda is the wavelength corresponding to the working frequency of the power module.

The noun notes to which the invention relates are as follows:

an input filter capacitor: and a capacitor connected to the input end of the self-excited push-pull converter and used for filtering ripples in the input voltage, such as a capacitor C2 in figures 1 and 2. It can be the filter capacitor of the superior power supply or the battery itself, including the super capacitor.

An output filter capacitor: and a capacitor connected to the output end of the self-excited push-pull converter and used for filtering out ripples in the output voltage, such as a capacitor C3 in figures 1 and 2. It can be the input filter capacitor of the lower power supply or the battery itself, including the super capacitor.

Starting a capacitor: and a capacitor for realizing quick start or soft start of the self-excitation push-pull type converter, such as a capacitor C1 in figures 1 and 2.

Push-pull triode: the transistors for realizing self-excited push-pull type operation, such as the transistors TR1 and TR2 in fig. 1 and 2.

A main transformer: the main power transformer is a transformer for transmitting energy to a load, the voltage is converted into a required value, a center tap of a primary side of the main power transformer is connected with a power supply, namely, the working voltage of the self-excitation push-switch type converter, the other two terminals of the primary side of the main power transformer are respectively connected with two collectors of a push-pull triode, and a secondary side of the main power transformer is connected with one or more rectifying circuits in a winding way, such as a transformer B1 in figures 1 and 2;

a feedback winding center tap: the center tap of the winding connected between the bases of two push-pull triodes, such as the main transformer winding N in fig. 1 and 2_B1And N_B2Is tapped at the center.

The power module of the present invention solves the technical problem that related people have been eagerly solved for a long time but have not yet succeeded, and the discovery process, method, and working principle will be analyzed in specific embodiments, which are not described herein.

The self-excitation push-conversion type converter has the beneficial effects that:

(1) the failure rate is greatly reduced;

(2) the product models will decrease and the versatility of the customer's use will increase.

Drawings

FIG. 1 is a schematic diagram of a typical application of a Royer circuit;

FIG. 2 is a schematic diagram of another exemplary implementation of a Royer circuit;

FIG. 3 is a schematic diagram of a power module according to a first embodiment of the present invention;

FIG. 3-1 is a waveform diagram of the output voltage of the first embodiment of the present invention;

FIG. 3-2 is a schematic diagram of a first embodiment of a client external output rectifying and filtering circuit according to the present invention;

3-3 are graphs of voltage waveforms of FIGS. 3-2 assuming filter capacitor C3 is not present and a purely resistive load is used;

FIGS. 3-4 are schematic diagrams of a first embodiment of the present invention to achieve a common ground dual output;

FIGS. 3-5 are schematic diagrams of the first embodiment of the present invention to obtain a voltage-doubled output;

fig. 3 to 6 are schematic diagrams of a first embodiment of the present invention in which a secondary winding is added to obtain independent dual outputs, and are also schematic diagrams of a fifth embodiment of the present invention in which a power module is applied in a power system.

FIGS. 3-7 are schematic diagrams of the start-up circuit of the first embodiment of the present invention with capacitor C1 and resistor R1 connected in parallel;

FIG. 4 is an exemplary schematic diagram of a power module according to a second embodiment of the present invention;

FIG. 4-1 is a schematic diagram of a second embodiment of the present invention to achieve a common ground dual output;

FIG. 4-2 is a schematic diagram of a second embodiment of the present invention with an additional secondary winding to obtain independent dual outputs;

FIG. 5-1 is a schematic diagram of a main transformer magnetic core structure of a power module according to a third embodiment of the present invention;

FIG. 5-2 is a second schematic diagram of a main transformer magnetic core structure of a power module according to a third embodiment of the present invention;

FIG. 5-3 is a third schematic diagram of a magnetic core structure of a main transformer of a power module according to a third embodiment of the present invention;

fig. 6 is a schematic diagram of a power module according to a fourth embodiment of the present invention.

Detailed Description

The failure is a technical problem which is expected to be overcome in the industry for a long time, the product is subjected to plastic package or encapsulation to improve the environmental adaptability, and the power module is damaged during disassembly after the product fails, so that failure analysis is extremely difficult, and ultimate improvement cannot be further performed.

The applicant collects a plurality of failed samples, analyzes the samples according to a traditional method, and obtains the conclusion that the breakdown of the triode for push-pull is not the exception, and the power module is used as a device on a circuit board again and is subjected to reflow soldering again to cause the cracking of a capacitor, short circuit or the breakdown of a Schottky diode for rectification used inside.

The inventor has noticed that the short circuit impedance of the short circuit presented by the power module to the outside is widely distributed, namely, the short circuit impedance is distributed from 0.1 omega to nearly 10 omega and is more distributed about 2 omega, which is different from the distribution presented by the semiconductor failure, the failure caused by other reasons is presumed, but many data are consulted, many experts in China are consulted, and no convincing explanation is provided. In the production of the power module, the used solder paste is alloy, also called solder paste, and mainly consists of soldering flux and solder powder, also called solder powder, mainly consists of tin-lead, tin-bismuth and tin-silver-copper alloy, like other manufacturers, the high-melting-point solder paste is selected, the melting point is above 280 ℃, in theory, when the device is reflowed again at the client, the temperature is strictly controlled below 260 ℃, the welding spot in the power module should not be melted again, tens of thousands of products are put into the power module, each batch of 5000 products, and different temperature tests show that the products can be actually failed and are mainly short-circuited within the temperature range of 235-265 ℃. The melting point of pure tin is 231.89 ℃, but from where the pure tin inside the power module comes.

The pins of the internal devices of the power module are mostly pins covered by pure tin plating, and the applicant reuses the common method in the technical field: alternative methods. The electrochemical process is used for deplating and detinning the pins of the participated device, and plating a silver layer with the melting point of more than 961 ℃, the problem is to be overcome, but the result still has short circuit, the analysis of expensive transparent crystal glue slices shows that the short circuit caused by pure tin still exists, and further conjectures that the diameter of tin particles in the solder paste is too large, the electric spark current is reduced when the solder paste supplier prepares the tin powder, and the tin particles with smaller diameter are obtained, the solder paste supplier directly adopts the raw material with the smallest particles on the earth imported from Japan and Germany, the problem is solved by matching with the industry, and the test shows that almost the same failure rate still exists.

At this time, the inventor has noticed that the capacitors in the power module are all chip capacitors, which are called chip multilayer ceramic capacitors in the industry, abbreviated as MLCC in english, and the capacitors are formed by overlapping ceramic dielectric films with printed electrodes (inner electrodes) in a staggered manner, forming a ceramic chip through one-time high-temperature sintering, and sealing metal layers (outer electrodes) at two ends of the chip to realize the required capacitance and other parameter characteristics. The capacitor is internally provided with a plurality of layers, an inner electrode is a silver layer, and the capacitor is also provided with a dielectric ceramic material, the thermal expansion coefficients of the layers are different, the layers are stacked together like a plurality of biscuits, the situation that the sheet surface of the capacitor is parallel to a circuit board and is vertical to 90 degrees is difficult to ensure during chip mounting, namely whether the capacitor is axially rotated by 90 degrees during chip mounting is noted: the shaft passes through the geometric center of the two terminals. After the analysis of crystal gel slices, 10 samples with short circuit are found, 8 samples are only pasted by rotating the capacitor by 90 degrees, and the inventor guesses that: after the capacitor is rotated by 90 degrees, the horizontal position of the circuit board is taken as a reference, a plurality of potential grooves are formed in the top parallel to the circuit board, pure tin is firstly melted at high temperature and is influenced by the sealed environment of plastic package or encapsulation, and the pure tin rushes forward in the grooves to short circuit two ends. The placement machine itself is not capable of doing this by asking the supplier of the capacitor, who acknowledges that the capacitor is randomly taped in a disc-like tray, i.e. when placing the chip, it is possible that nearly 50% of the time is 90 degrees of axial rotation.

This is only a conjecture, when the product is disassembled by the crystal glue slice, the short circuit disappears, and the conjecture cannot be verified, and the inventor proposes a new experimental method again: using a low-voltage and high-current power supply from the outside, whether the internal resistance formed by short circuit can generate heat to melt tin and the surface tension of liquid tin can be utilized to automatically retract into a spherical shape or have such a tendency that the short circuit point disappears? Through calculation, combined experiments, and finally, a 2A power supply is output at a constant current with a maximum output voltage of 5V, and a power supply module with a short circuit at an input end is subjected to experiments, so that a short circuit point really disappears; the power module with the short circuit at the output end of the power module is tested, the polarity needs to be noticed, otherwise, the internal rectifier diode can be burnt, the short circuit point is found to disappear, and the performance of the product is recovered.

After finding the root cause, the solution to this problem seems to be that no input and output filter capacitors are needed. But the client must not agree, the client will want to: this obviously degrades the performance of the power supply module and electromagnetic compatibility is certainly degraded.

Note: the circuit board includes a lead frame using a metal thin plate.

Even though the external capacitor is discovered as a root cause, which is easy to be thought by those skilled in the art, the external capacitor is not considered as a feasible solution due to the limitation of the electromagnetic compatibility standard requirement, so that the most advanced manufacturers at home and abroad are always dedicated to the improvement of the welding material and the welding process, and the japanese village corporation applies a plurality of patents of the welding material and the welding process for the power module of the royer circuit from 2011 to 2013. So that although the circuit was widely used since 1955, failure rate could not be further reduced over 60 years.

The inventor breaks through the conventional thinking, proposes that the capacitor can be arranged externally, and the theoretical basis is as follows:

according to well-known electrical theory, there are: c ═ λ f

Wherein C is the propagation velocity of electromagnetic wave 3 × 10⁸m/s; λ: wavelength in m; f: frequency in Hz;

the invention requires that the distance between the external capacitor and the power supply module is less than or equal to lambda/11, the electromagnetic radiation generated by the external capacitor to the space is very little, the electromagnetic radiation generated by the external capacitor to the space can be considered not to be generated, the loss is small, and the effect is good. The relevant theoretical basis is not directly discussed, and reference is made to the twenty-first academic annual meeting paper of the Chinese society for power supply "application of minimum loop in EMC design", which is published in 11 months 2015, the authors of this paper are the inventors of the present application and indicate that "the 1/4 wavelength of the high frequency signal is the same as the length of the antenna, the antenna has good radiation and reception capabilities … … once the antenna is formed, and when there is a step signal in the loop, the antenna will automatically select the resonant frequency to transmit out, and the output of the transformer of the present invention is square wave, the rising edge or the falling edge of the capacitor is a step signal, and then, in order to reduce external radiation, the distance from the external capacitor to the power module is within 1/4 wavelengths, and more preferably, less than half of 1/4 wavelengths, that is, less than 1/8 wavelengths. To further ensure the effect, the distance between the external capacitor and the power module is within the golden section of 1/4 wavelengths, namely (1-0.618), which is 0.382 times 1/4 wavelengths, and is most closely λ/11.

Because the working frequency of the self-excitation push-pull converter is mainly 50kHz, 100kHz and 200kHz, the highest frequency can be 1MHz at present, and the breakthrough of 10MHz is expected to be realized in the future, the distance between the external capacitor and the power supply module is calculated as follows aiming at the self-excitation push-pull converters with different working frequencies:

frequency of operation	Wavelength lambda	λ/11
			50kHz	6000m	545.4m
100kHz	3000m	272.7m
			200kHz	1500m	136.3m
1MHz	300m	27.27m
			10MHz	30m	2.727m

When a step signal exists in a loop, the antenna can automatically select a frequency resonant with the antenna to be transmitted, according to engineering experience, 19 th harmonic of the harmonic still has considerable radiation capability, even if the working frequency of the self-excitation push-pull type converter is multiplied by 19, the distance between the external capacitor and the power supply module is within 19 times of 1/11 wavelength, namely within 1/209 wavelength, the requirement of electromagnetic compatibility standard can still be met, and the following is the calculation result of the distance between the external capacitor and the power supply module under the condition:

frequency of operation	λ	λ/209
			50kHz	6000m	28.71m
100kHz	3000m	14.35m
			200kHz	1500m	7.18m
1MHz	300m	1.44m
			10MHz	30m	0.14m

When the working frequency of the module is 1MHz, the distance is 1.44 meters, and the performance of electromagnetic compatibility can still be ensured.

First embodiment

Referring to fig. 3, fig. 3 is a schematic diagram of a power module according to a first embodiment of the present invention, which is drawn by a similar integrated circuit, and has pins outside, and a frame is a dashed thick line to indicate that internal devices are integrated and packaged together, the dashed thick line of the frame does not indicate an electrical connection, the power module includes an input positive terminal Vin, an input ground GND, and two output terminals Out1 and Out2, and the power module includes: resistor R1, capacitor C1, triode TR1, triode TR2, main transformer B1 and primary winding N_P1And N_P2Feedback winding N_B1And N_B2And a secondary winding N_S1(ii) a One end of the resistor R1 is connected with the positive input terminal, and the other end of the resistor R1 is connected with the input ground after passing through the capacitor C1; the emitters of the transistors TR1 and TR2 are connected to the input ground, and the collectors are respectively connected with the primary winding N_P1And N_P2Two terminal, base electrodeRespectively connected with a feedback winding N_B1And N_B2Two ends of (a); primary winding N_P1And N_P2The center tap of the power module is connected with the input positive terminal of the power module; secondary winding N_S1Are connected to the two output terminals of the power supply module.

In the above description, the input filter capacitor and the output filter capacitor are removed from the power module, and the power system of the client can still satisfy the design method and the theoretical basis of electromagnetic compatibility, which are not described herein again.

FIG. 3-1 is a waveform diagram of the output voltage of the present embodiment, which is a square wave alternately appearing in positive and negative voltages, as in the prior art; when a client is externally connected with the circuit shown in fig. 3-2, a single-path output voltage can be obtained, and only one diode D1 is used, so that when the output filter capacitor C3 does not exist and a pure resistive load is used, the waveform diagram of the output voltage is shown in fig. 3-3 and is half-wave output, the capacity of C3 should be increased to obtain a required ripple voltage, as discussed above, when the module operating frequency is 1MHz, the distance is 1.44 meters, and the electromagnetic compatibility performance can still be ensured. Namely, C3 is within 1.44 meters away from the power module, it is obvious that in the client system, the original decoupling capacitor in the client system can be fully utilized as C3 without increasing the cost, since the original decoupling capacitor may be formed by connecting an electrolytic capacitor in parallel with a ceramic capacitor of 1000pF to 0.1uF, the total capacity is larger because of the use of a solid electrolytic capacitor such as tantalum, and therefore, the filtering effect is good. The half-wave output does not cause any adverse effect on the triodes for push-pull, and only one triode is always in a light load state.

When the diode D1 in fig. 3-2 is reverse connected, a negative voltage output can be obtained, which is not separately listed in the embodiments. Of course, if the connection point of the cathode of the diode D1 and the upper lead of the C3 in fig. 3-2 is directly used as the dc output ground, the dc output terminal connected to the other lead of the C3 will output a negative voltage, and the dc output terminal can work normally. Before the diode D1, that is, the two output terminals of fig. 3 are directly connected in parallel with a small-capacity filter capacitor, the rising edge and the falling edge of the square wave can still be absorbed, which is beneficial to the improvement of electromagnetic compatibility.

Because the power module is not provided with a diode, as is known, because the operating frequency of the switching power supply is higher, the output rectifier diode of the switching power supply mostly adopts a Schottky diode as the power module, after being mounted or inserted on a circuit of the switching power supply, a customer can reflow or wave soldering again, most of devices are designed according to the equivalent resistance of 260 ℃ for 12 seconds and bear 2 times of high temperature, and the failure caused by the Schottky diode is increased rapidly. The European Union forbids the use of lead and other harmful substances in 2006, 7 and 1 by RoHS and WEEE instructions, and pulls the start of high-temperature welding of electronic products open, the melting point of the traditional tin-lead eutectic solder is 183 ℃, but the melting point of the commonly accepted and widely adopted tin-silver-copper (SAC) lead-free solder is about 217 ℃ at present, so that the thermally induced failure is greatly aggravated, and all related device manufacturers can support the 12-second welding at 260 ℃ after years of research to show the reliability of the devices. This does not mean that the device is reliable for 12 seconds soldering at 260 c, is non-destructive, and the device manufacturer can only guarantee that the failure rate is below a certain value at this high temperature. Meanwhile, as a high-quality electronic product manufacturer, the reflow soldering temperature is still controlled below 245 ℃; the fact that the products are civil products and have low requirements on the service life is to be noted, for example, MP3 can work continuously for 3000 hours, the satisfaction degree of consumers is high, after 3000 hours, the products are good when the repair rate is lower than 3%, and the requirement for switching power supplies causes great complaints. The paint is not acceptable when used on automobiles.

From a scientific standpoint, the continuous high temperatures have a negative impact on semiconductors. The centralized representation is as follows: the insulation performance is degraded; the components are directly damaged; thermal aging of the material. From the characteristics of semiconductors, the current semiconductor used in the electronic industry is generally referred to as a silicon semiconductor, silicon itself is very strong and has a melting point of 1410 ℃, which does not mean that the semiconductor is damaged until the temperature reaches 1410 ℃, and generally, at 165 ℃, the electrified silicon semiconductor basically directly damages the silicon semiconductor due to the occurrence of a large number of minority carriers and the directional movement of the minority carriers; in a schottky diode, generally, the higher the doping concentration, the better the conductivity of the semiconductor becomes and the lower the voltage drop, since the number of electrons that can enter the conduction band increases with increasing doping concentration. Semiconductors with very high dopant concentrations are widely used in schottky diodes because of their conductivity close to metals. In the next high temperature reflow soldering, etc., although the silicon semiconductor can survive without being energized, at high temperature, a large number of minority carriers appear, and the combination and regeneration of majority carriers still damage the PN junction of the semiconductor due to the non-directional movement. It is known that at a junction temperature of 165 ℃, the energized silicon semiconductor directly damages the silicon semiconductor due to the occurrence of a large number of minority carriers, the directional movement of the minority carriers.

The invention arranges the rectifier diode outside, so that the rectifier diode only bears once welding high temperature, thereby obviously reducing the failure rate of the whole system and improving the reliability of the whole system.

The external capacitor C3 is easy to increase the capacity by using a low-cost electrolytic capacitor, so that the secondary winding of the power module is simplified into one winding from two windings in figures 1 and 2, and the cost is saved.

The rectifier diode is external, still obtains another beneficial effect: the common-ground dual output can be easily obtained, referring to fig. 3-4, the dual output can be obtained, and the push-pull triodes are all in a loaded state.

Further, if the negative output in fig. 3-4 is taken as the ground, then a voltage-doubling output can be obtained, for example, to obtain a dc voltage of 18V, only the 9V power module of the present invention is needed, and the usage of fig. 3-5 is needed.

The rectifier diode is external, still obtains another beneficial effect: easily obtain the output of independent double-circuit more than, independent double-circuit means they are not common ground, and this kind of power module and its usage are given in fig. 3-6: one path of secondary winding N is added_S2Correspondingly, the external rectifier diode is added with D2, the filter capacitor is added with C5, and the other path of direct current output voltage, namely the path DCout2 in the figure, can be the same as or different from the path Dout 1 in voltage, the turn ratio can be changed, and the positive and negative polarities of the two paths of voltage can be set arbitrarily. The homonymous ends of the two secondary sides in the figures 3-6 are reserved, so as to ensure that the push-pull triodes are all positionedAnd (4) a loaded state. According to the traditional technical scheme of using the figures 1 and 2, a scheme of two paths of different grounds is obtained, 4 secondary windings are used for the secondary side, the cost is high, and the winding is difficult. 3-6, a diode is added to obtain three outputs, wherein two outputs are grounded and are not grounded with the third output; and further adding a diode, and obtaining four paths of output, wherein the first path and the second path are in common ground, the third path and the fourth path are in common ground, and the first path, the second path, the third path and the fourth path are not in common ground.

It should be noted that the start circuit of this embodiment is composed of a resistor R1 and a capacitor C1, the resistor R1 is a current supply device and supplies a start voltage to the power module, the resistor R1 may be replaced by a resistor parallel capacitor or a constant current source, and the purpose of the present invention can also be achieved, the capacitor C1 can absorb peak voltages on the transistor TR1 and the transistor TR2 when the power module is powered on, so as to prevent the transistors from being burned out, thereby achieving soft start of the power module. Fig. 3-7 show another implementation of the first embodiment, the start-up circuit includes a current supply device resistor R1 and a capacitor C1, one end of the resistor R1 is a start-up input end, the other end is a start-up output end, the capacitor C1 is connected in parallel with the resistor R1, and the resistor R1 can be replaced by a constant current source device, the usage of which is fully disclosed in chinese application No. 201110200894.5 and will not be described here.

Second embodiment

Referring to fig. 4, a schematic diagram of a power module according to a second embodiment of the present invention is different from fig. 3 of the first embodiment in that an output rectifying diode D1 shown in fig. 3-2 is integrated inside the power module, which is a design that can meet the requirements of customers who do not want to design an output rectifying circuit externally. In this embodiment, the input filter capacitor and the output filter capacitor are removed, and the design method and the theoretical basis that the power system of the client can still satisfy the electromagnetic compatibility are described above, which are not repeated herein.

The second embodiment has the advantages that the original system of the client does not need to be changed, the power supply module of the second embodiment can be directly used for replacing the original module such as the power supply module shown in fig. 1 and fig. 2, and the use is very convenient.

Similarly, a diode D2 is added to the diode integrated in the second embodiment, so that the embodiment of FIG. 4-1 is obtained, and a common-ground dual-path output can be obtained;

fig. 4-2 shows a second embodiment with the addition of a winding N_S2The diode D2 is connected in series to easily obtain more than two paths of outputs which are not in common with the ground, and similarly, in the technical scheme of fig. 4-2, one more diode is added to obtain three paths of outputs, wherein two paths of outputs are in common with the ground and are not in common with the third path; and further adding a diode, and obtaining four paths of output, wherein the first path and the second path are in common ground, the third path and the fourth path are in common ground, and the first path, the second path, the third path and the fourth path are not in common ground.

The starting circuit comprises a current supply device resistor R1 and a capacitor C1, one end of the resistor R1 is a starting input end, the other end of the resistor R1 is a starting output end, and the capacitor C1 is connected with the resistor R1 in parallel, so that the purpose of the invention is also achieved. The resistor R1, or a constant current source device, the use of which is fully disclosed in chinese application No. 201110200894.5 and will not be described here.

Third embodiment

Referring to fig. 5-1, 5-2 and 5-3, three schematic structural diagrams of the main transformer magnetic core of the power module according to the third embodiment of the present invention are shown, and the circuit diagram structure is the same as that of the first embodiment or the second embodiment, which is not repeated herein.

The inventive concept of the third embodiment is that the magnetic core of the main transformer B1 is composed of a main part and a local part, and the local part reaches magnetic saturation before the main part under the excitation of the same magnetic field from small to large, so that the magnetic core only momentarily approaches or reaches the local first quadrant saturation point or the local third quadrant saturation point when in operation, and the other time is between the inherent first quadrant saturation point and the third quadrant saturation point. Such cores are known in the industry as Ronling cores. The working principle of the part can be seen in the patent specification with Chinese application numbers 201110436359.X and 201110436259.7.

The main part A and the local part B of the magnetic core shown in the figure 5-1 are made of the same material, the sectional area of the main part is larger than that of the local part, and the local part reaches magnetic saturation before the main part under the excitation of the same magnetic field from small to large. When the magnetic core works locally, the magnetic core only approaches or reaches a local first quadrant saturation point or a local third quadrant saturation point instantly, and the smaller the local magnetic core length is, the better the effect is; the magnetic core of fig. 5-1 is derived from the solution of fig. 7 and 8 of chinese application No. 201220206952, where only two protrusions on the magnetic core have been removed.

The main part A and the local part B of the magnetic core shown in the figure 5-2 are made of different materials, the sectional area of the main part is smaller than that of the local part, and the local part is made of a material with high magnetic permeability, so that the local part is magnetically saturated before the main part under the excitation of the same magnetic field from small to large. When the magnetic core works locally, the magnetic core only approaches or reaches a local first quadrant saturation point or a local third quadrant saturation point instantly, and the smaller the local magnetic core length is, the better the effect is;

the main part a and the local part B of the magnetic core shown in fig. 5-3 have the same cross section and are made of different materials, and if the local magnetic permeability is greater than that of the main part, that is, if a material with higher magnetic permeability is locally used, the local part can also achieve magnetic saturation before the main part under the excitation of the same magnetic field from small to large. When the magnetic core works locally, the magnetic core only approaches or reaches a local first quadrant saturation point or a local third quadrant saturation point instantly, and the smaller the local magnetic core length is, the better the effect is. The magnetic core of fig. 5-3 is from the solution of fig. 12 in chinese application No. 201220206952.

Fourth embodiment

Referring to fig. 6, a typical schematic diagram of a power module according to a fourth embodiment of the present invention is different from the first embodiment in that a capacitor C4 is connected in parallel between collectors of two push-pull triodes, so as to eliminate high-frequency self-excitation generated by an excessively high characteristic frequency when the push-pull triodes are powered on, and after the capacitor C4 is added, the high-frequency self-excitation attenuates oscillation or the oscillation frequency shifts down, so that the two push-pull triodes can quickly enter push-pull oscillation performed by using a core saturation characteristic within a dozen of cycles, thereby realizing fast start of the circuit, and in addition, the high-frequency self-excitation is effectively controlled, and the push-pull triodes are not damaged. And can also obtain the output short-circuit protection function, and the working principle of the output short-circuit protection device is shown in Chinese application No. 201010604284.7 in detail.

Fifth embodiment

Referring to fig. 3-6, which are schematic diagrams of the power module of the present invention applied in a power system, the present embodiment applies the power module of the first embodiment, an input filter capacitor C2 and diodes D1 and D2, an output filter capacitor C3 is designed by a customer in the power system, and is soldered on a circuit board of the customer, and C2 may be an output filter capacitor of a previous stage of switching power supply, and does not need to be specially installed.

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-described preferred embodiment should not be construed as limiting the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention, such as changing the N-type transistor to P-type, and reversing the supply voltage; or the MOS tube is adopted to realize the constant current source circuit; and the idea of the present invention is applied to the power module and the power system using the non-self-excited push-pull converter, and these modifications and decorations should also be regarded as the protection scope of the present invention, which is not described herein again by embodiments and shall be subject to the scope defined by the claims.

Claims

1. A power supply system comprising a power supply module, characterized in that: the power module does not comprise an input filter capacitor and an output filter capacitor, the power module at least comprises four terminals, namely an input positive terminal, an input ground, two output terminals, a starting circuit, a triode TR1, a triode TR2 and a main transformer B1, and the main transformer B1 comprises a primary winding N_P1And N_P2Feedback winding N_B1And N_B2And at least one secondary winding N_S1(ii) a The starting circuit at least comprises two terminals, a starting input end and a starting output end, the starting input end is connected with the input positive terminal of the power module, and the starting output end is connected with the feedback winding N_B1And N_B2The center tap of (1); the emitters of transistors TR1 and TR2 are both connected to the input ground of the power supply module, the collectorThe electrodes are respectively connected with a primary winding N_P1And N_P2Two ends and bases of the transformer are respectively connected with a feedback winding N_B1And N_B2Two ends of (a); primary winding N_P1And N_P2The center tap of the power module is connected with the input positive terminal of the power module; secondary winding N_S1Both ends of the power module are connected with two output terminals of the power module;

in the power supply system, a capacitor C2 is connected in parallel between an input positive terminal and an input ground of the power supply module, a capacitor C3 is connected in parallel between two output terminals, the distance between each of the capacitor C2 and the capacitor C3 and the power supply module is less than or equal to lambda/11, and lambda is the wavelength corresponding to the working frequency of the power supply module.

2. The power supply system according to claim 1, wherein: the starting circuit comprises a current supply device and a capacitor C1, wherein one end of the current supply device is a starting input end, the other end of the current supply device is a starting output end, the capacitor C1 is connected with the current supply device in parallel, and the current supply device is a resistor or a constant current source device.

3. The power supply system according to claim 1, wherein: the starting circuit further comprises a third terminal, the starting circuit comprises a current supply device and a capacitor C1, one end of the current supply device is a starting input end, the other end of the current supply device is a starting output end, the third terminal is connected with an input ground, one end of a capacitor C1 is connected to the starting output end, the other end of the capacitor C1 is a third terminal, and the current supply device is a resistor or a constant current source device.

4. The power supply system according to claim 1, wherein: secondary winding N_S1And at least one diode D1 is connected between any one of the terminals and the output terminal of the power supply module to which it is connected.

5. The power supply system according to claim 1, wherein: the magnetic core of the main transformer B1 consists of a main part and a local part, the main part and the local part are made of the same material, and the cross sections are different; or the main part and the local section area are the same, and the materials are different.

6. The power supply system according to claim 1, wherein: a capacitor C4 is connected between the transistor TR1 and the collector of the transistor TR 2.

7. The power supply system according to claim 6, wherein: the capacitance value of the capacitor C4 is less than 1000 pf.

8. The power supply system according to any one of claims 1 to 7, wherein: a capacitor C2 is connected in parallel between an input positive terminal and an input ground of the power supply module, a capacitor C3 and a diode are connected in series between the two output terminals to form a circuit, the distance between the capacitor C2 and the capacitor C3 and the power supply module is less than or equal to lambda/11, and lambda is the wavelength corresponding to the working frequency of the power supply module.