JPS63501400A - flyback power supply - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] flyback power supply Background of the invention The present invention relates to the field of flyback power supplies. More specifically, the present invention provides an output sensing flap. A feedback control loop is provided to control the power of the primary winding of the flyback transformer in the power supply. Stable flyback power supply that is stable even when operating in continuous excitation mode with respect to current excitation Regarding.

In known flyback power supplies, a pulse is applied to the primary winding of the flyback transformer. An excitation current is applied and the secondary winding of the transformer is connected to the load, typically through a rectifier. is combined with The rectified output is sensed and the feedback path It is applied as an input to a drive circuit that generates a drive signal that determines the current excitation pulse.

The drive signal changes according to the detection output to keep the output at a predetermined level, and the output Adjust.

Typically these flyback power supplies operate in discontinuous mode for stability reasons. . In discontinuous mode, the magnetic flux increases in the transformer during the primary winding current pulse, During the pulse interval of the primary winding current pulses, the magnetic flux decreases to a substantially zero value.

In general, the decrease in magnetic flux to zero value is rapid, and the flywheel operating in discontinuous mode Backpack transformers typically generate substantial radio frequency interference (RFI). In addition, the following A large primary winding is typically required to store a significant amount of energy that is transferred to the secondary winding. Winding current pulses must be used, otherwise the period of the primary excitation pulse The wave number must be increased.

The flyback power supply is turned on before the drive circuit increases the magnetic flux to store additional energy. The lance should be operated in continuous mode so that the magnitude of the magnetic flux in the lance is virtually zero. For example, less primary current can be used and less radio frequency interference can be generated. Become. Furthermore, the excitation frequency can be lowered as needed. However, Operating in continuous mode introduces stability issues with the regular power supply, which makes it difficult to operate in continuous mode. The flyback power supply of the board becomes unavailable or Therefore, the system gain, input signal magnitude, and primary excitation current frequency must be carefully controlled. need to be controlled.

However, due to load fluctuations, it is generally not possible to maintain this stability. . Therefore, virtually all flyback power supplies operate in discontinuous mode. .

Summary of the invention It is an object of the present invention to provide an improved flyback power supply that overcomes the above-mentioned drawbacks of conventional flyback power supplies. It is to provide back power.

A more particular object of the invention is to provide a stable flyback capable of operating in continuous mode. It is to provide power.

A flyback power supply is provided in one embodiment of the invention. This flyback A DC power supply is an end that receives a DC power supply voltage input signal that varies over a range of magnitudes. a transformer comprising a terminal means and a primary winding and a secondary winding coupled to the terminal means; and at least one detection signal input, as an output to said primary winding. generating a control input signal to the control electrode of the coupled drive device to the power supply voltage input; drive circuit means for controlling the primary current of the primary winding supplied by a signal; Coupled to the winding, the signal induced in the secondary winding is rectified, and the output terminal is connected accordingly. rectifier means for generating a DC power supply output voltage at the output terminal; and controlling the drive circuit means to bring the power supply output signal to a desired level. and a feedback path means for maintaining the is between the output terminal and the holding capacitor connected to the detection input. Sample with a controllable gating device with a control terminal receiving a switch signal and a hold circuit, and the gate device is configured such that the control device is a primary A winding current is applied to increase the magnetic flux within the transformer means and to store energy therein. when the power supply output signal is effectively connected to the holding capacitor. The holding capacitor is alternately opened and closed so as to be sampled. The magnetic flux within the transformer means decreases and the stored energy is transferred to the secondary winding and the At all other times the rectifier means is supplied, it is effectively disconnected from said output terminal. , this increases the stability of the power supply by ensuring that energy is transferred from the primary winding to the secondary winding. as obtained by a discontinuous feedback path that samples at times other than when It has been improved.

More specifically, in a preferred embodiment of the invention, the drive device is a flyback truck. The driver provides a continuous mode of excitation to the The magnetic flux of the transformer has a substantially non-zero magnitude before the current begins to flow. so that A preferred embodiment of the invention includes a pulse width modulation circuit as the drive circuit means. is applied as a control input signal to the drive which determines the primary winding excitation. The gate device is alternately opened and closed according to the output of the pulse width modulation circuit. This is it This ensures that the controllable gate device is properly synchronized with the excitation of the primary winding. In addition, preferred Alternatively, the gating device is connected in series between the output terminal and the pulse width modulation detection input. Fascinating the pass device. It is preferable that the drive device is equipped with an FE lower transistor. stomach.

By providing a discontinuous feedback path in accordance with the teachings of the present invention, power supply loads can be regardless of fluctuations or fluctuations in the magnitude of the DC power supply voltage input signal. A stable flyback power supply is provided. This is an inexpensive and loose tolerance process. This means that road parts can be used. When the power supply operates in continuous mode, the flybar The radio frequency interference generated by the primary winding power supply is reduced, and the small primary winding power supply is Current excitation pulses can be used. In addition, according to the present invention, the pulse width modulation circuit This provides greater design flexibility in determining the operating frequency of the circuit and the primary winding current excitation pulse. It is possible to select a higher or lower frequency with respect to the period of the signal that determines the can. By choosing a higher operating frequency, this now generates less radio frequency interference. However, it is possible to use circuit components that are cheaper and smaller in size than the power supply. can be used.

These and other advantages of the invention will be apparent from the more detailed description of the invention that follows. It is best understood if

Brief description of the drawing For a more complete understanding of the invention, reference may be made to the drawings, which include: FIG. 1 is a schematic diagram of a flyback power supply constructed in accordance with the teachings of the present invention.

Description of preferred embodiments of the invention Referring to the drawings, a flyback power supply 10 is shown. Power supply is DC power supply voltage It is provided with an input terminal 11 that receives an input signal ■io. The magnitude of this signal is varies over a wide range. Essentially, a flyback power supply receives a DC input signal ■i o and accordingly, a well-regulated DC output signal at the output terminal 12. ,t occurs. Various loads, schematically shown as load 13 in the figure, are connected to output terminal 1. It is now possible to connect to 2. In this way, the flyback power supply can be Regular signal V. , 1 and performs the adjustment and power transfer function to generate

Input terminal 11 is connected to terminal 14 via a filter network 15 shown in broken lines in the figure. It is. The filter network somewhat reduces ripple on the DC signal at terminal 14. The initial voltage smoothing function for the signal io is performed as follows. Flyback power supply 1 0 has one end connected directly to the terminal 14 and the other end connected to the drain of the FET transistor 20. A transformer 16 is provided with a primary winding 17 connected directly to the terminals.

The transformer 16 includes a transformer core 18 that generates transformer magnetic flux by exciting the primary winding 17. , a transformer core and a secondary winding 19 coupled to the primary winding. secondary One end of the winding 19 is connected to ground, and the other end is output via the rectifier diode 21. is connected to terminal 12, while capacitor 22 is connected between terminal 12 and ground. It is connected. Substantially, the diode 21 and the capacitor 22 are connected to the secondary winding 19. and rectifies the signal induced in the secondary winding, and accordingly outputs D to the output terminal The rectifying means for generating the C power supply output voltage is formed.

FET transistor 20 is periodically turned on and off, thereby effectively Controls the current excitation of the primary winding.

The source terminal of the FET transistor is connected directly to ground; The gate or control electrode terminal of the transistor is connected to the pulse width modulation (PWM) circuit 2 shown in the figure. 3 receives pulses with a duty cycle that changes periodically. Pulse width modulation times Path 23 is typically the output signal V. , a detection input terminal receiving a signal related to the magnitude of t. It is equipped with 24. The PWM circuit 23 has a reference terminal 25 that provides a predetermined external reference voltage. It also has Alternatively, circuit 23 generates the reference voltage at terminal 25 internally. be able to. Output related detection voltage at terminal 24 and reference voltage at terminal 25 The pulse width modulation circuit 23 outputs the control input signal as an output at the terminal 26. A signal is generated which is applied to the gate of FET transistor 20. FET 20 serves as a drive for the primary winding 17 of the transformer 16. In this way, pal The output of the width modulation circuit is determined by the voltage input signal Vio via the drive device 20. The primary winding current given by the voltage at terminal 14 is controlled.

The pulse width modulation circuit 23 shown in the figure adjusts the magnitude of the detection signal according to the DC detection signal. The pulse of variable duty cycle is determined by the difference from the reference voltage held at terminal 25. Includes a Motorola MC34060 integrated circuit that generates a width modulated output signal. It should be noted that it is desirable to be able to The top of the pulse width modulation circuit 23 The terminal output device is an NPN transistor 27 whose collector is connected to the terminal 26. As shown in the figure. Because of this configuration, bias/load resistor 28 is connected to terminal 26. It is coupled between the terminal 14 and the terminal 14. In addition, the flyback power supply 10 shown in the figure is connected between the drain terminal of FET 20 and the ground, and a diode 30 and a resistor are connected between the drain terminal of FET 20 and the ground. The conventional "strip" shown by the broken line is equipped with a resistor 31 and a capacitor 32. It is equipped with a "Natsupa" circuit 29. The function of the snapper circuit is that the FET transistor is turned on. The high reverse buffer caused by abruptly interrupting the current in the primary winding 17 when The purpose of this is to substantially protect the FET device from bias voltages. Snatsupa circuit 29 is actually In order to limit the magnitude of the reverse bias voltage generated at the drain terminal of the FET, work. The operation of the snapper circuit is not particularly important with respect to the present invention.

FET transistors have high frequency characteristics and temperature characteristics. The flyback power supply is therefore capable of operating over a wide severity range. and, if desired, an FE which generates periodic current pulses to the primary winding 17. Choosing a relatively high frequency to periodically turn on and off the T transistor It can be used to control the switching of the primary winding current. Can be done.

The feedback path connects the output terminal 12 and the detection input terminal 24 of the pulse width modulation circuit 23. is established between. The design of this feedback path is such that the detection terminal 24 The purpose of the present invention is to provide a signal related to the magnitude of the output voltage Vout. Typically this The feedback path connects directly between the output terminal 12 and the detection terminal 24 or It can be configured by connecting the transformer coupling. However, this feedback path Conventional flyback transformer installations generally suffer from increased transformer flux, especially when the power supply when turning on the drive which subsequently produces the primary winding current so as to When operating in continuous mode, where the transformer flux does not go to virtually zero just before the A problem arose with the stability of the Iback power supply. In such situations, there are substantial stability issues. problems exist, requiring high primary current pulses in discontinuous mode and virtually wireless Despite the fact that frequency interference occurs, conventional flyback transformers are generally was running in discontinuous mode. These drawbacks have been overcome by the present invention.

In the flyback power supply 10, a selective disconnection is provided between the output terminal 12 and the input detection terminal 24. A continuous feedback path 40 is provided. This feedback path 40 is The emitter terminal is shown as a dashed line in the figure, and its emitter terminal is directly connected to the output terminal 12. The collector terminal is connected to a holding capacitor whose other electrode is connected to ground. A PNP series pass transistor 41 is connected directly to one electrode of the sensor 42. We are prepared. Transistor 41 forms a controllable gate arrangement. Tran The base of resistor 41 is connected to terminal 12 through bias resistor 43. N A PN control transistor 44 is provided in the feedback path 40 to The transmitter is connected to ground, and the collector is connected to the transistor 41 through a resistor 45. The base is connected to the ground via the capacitor 46, and the resistor is connected to the base of the It is connected to the terminal 26 through the resistor 47. The collector of transistor 41 is in series It is directly connected to the detection terminal 24 through the resistor 48, and the resistor 49 is connected to the terminal 24 and ground. It is connected between the land and performs a voltage dividing function in cooperation with the resistor 48. essence Generally, components 41 to 49 constitute the tactical feedback path 40 of the present invention. are doing. Path 40 connects the DC circuit between serial bus device 41 and terminals 12 and 24. It has a route.

Essentially, selective feedback path 40 is connected to series pass device 41 and holding 2 and the detection terminal 24 due to selective conduction with the capacitor 42. The sample hold function is only effectively connected directly to the

In the present invention, this time increases the transformer flux to store energy in the transformer. This occurs during the period in which the primary winding current pulse is present. This is a switching signal. generated by a periodic pulse width modulated control input signal applied to terminal 26 which acts as a signal. Ru. This switching signal causes FET transistor 20 to conduct and at the same time The transistor 44 is made conductive, thereby making the transistor 41 conductive. therefore During the primary winding current pulse which increases the transformer flux, the series pass transistor 4 1 couples the voltage at terminal 12 to holding capacitor 42 . This results in Signal V. , t are effectively sampled. The pulse width modulation control signal at terminal 26 is F When the ET drive 20 is turned off, the current in the primary winding 17 is effectively stopped and the transformer The magnetic flux in the transformer 16 decreases and the energy stored in the transformer is transferred to the secondary winding 19. and a rectifier circuit having components 21 and 22. At this time, the transistor terminals 44 and 41 are turned off, and the transient signal at terminal 12 is turned off. This prevents it from reaching the capacitor 42 and the detection input terminal 24. For this reason, the flybar The stability of the stock power supply 10 is maintained. This is because instability is generally caused by energy transformation. Continuous feed between the output terminal and the detection terminal during the period when the signal is being transferred from the converter to the rectifier circuit. This is because this is caused by the provision of the back path.

Due to the configuration of the invention, the flyback power supply 10 is unconditionally stable and therefore The power supply can operate in continuous mode. On the other hand, conventionally, flyback power supply was used continuously. Operating in this mode can result in unstable power supplies and unnecessary signal oscillations. It was impossible because In continuous operation mode, the pulse width modulator circuit 23 The period of the control signal supplied to the terminal 26 is such that the transformer magnetic flux is While decreasing during the 0 off period, the current pulse is determined before the next primary winding current pulse occurs. Therefore, the size difference is virtually never zero. Therefore, hula Ivac transformer 10 increases the magnetic flux of the transformer.The FET transistor increases the magnetic flux of the transformer. The primary winding current does not become substantially zero at and just before the pulse starts flowing. It is preferable to operate in continuous mode. Therefore, the effective input of the primary winding 17 is The ductance allows a large amount of energy to be stored in the transformer 16, while this large amount so that less energy can be used to provide a greater amount of stored energy. To increase. Moreover, in continuous mode operation, the radio frequency interference is reduced.

The invention is described in terms of a flyback power supply designed to operate in continuous mode. However, the present invention applies to flyback power supplies designed to operate in discontinuous mode. is also applicable, but in this case, due to fluctuations in the load 13, it is sometimes difficult to operate in continuous mode. It should be noted that there are times when it works.

As such, it does not matter in what mode the invention is designed to operate. In the relationship, the flyback voltage f, 10 is made unconditionally stable. This stability is due to load 13 It will be achieved no matter how it changes. In addition, this stability depends on the magnitude of the input signal Vi, This is ensured even if the value fluctuates significantly.

While specific embodiments of the invention have been illustrated and described, further modifications and variations will occur to those skilled in the art. Improvements could be made. maintains the basic principles disclosed and claimed herein; All such modifications are included within the scope of the present invention.

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Claims (12)

[Claims] 1. terminal means for receiving a DC power supply voltage input signal whose magnitude varies over a range; Transformer means comprising a primary winding coupled to said terminal means and a secondary winding. and, comprising at least a detection signal input and as an output a control input signal coupled to said primary winding; The power supply voltage input signal is supplied to the control electrode of the drive unit which is connected to the drive unit. drive circuit means for controlling the primary current; coupled to the secondary winding to rectify the signal induced in the secondary winding and output the signal accordingly. rectifier means for generating a DC power output voltage at the power terminal; connected between said output terminal and said detection input for controlling said drive circuit means; feedback path means for maintaining the power supply output signal at a desired level; In a flyback power supply with The feedback path means has a hole connected to the output terminal and the detection input. sample and controllable gating device between the The control terminal of the gate device receives a switching signal. the gate device is configured to receive the power output signal when the drive device generating a primary winding current which increases the magnetic flux in the transformer means and imparting energy thereto; When storing, the holding device ensures that the sample is effectively sampled. The holding device is alternately opened and closed in such a way that the magnetic flux within the transformer means is The reduced and stored energy is supplied to said secondary winding and said rectifier means. At all other times, they are effectively disconnected from said output terminals, thereby dissipating energy. A discontinuous filter that performs sampling other than when being transferred from the primary winding to the secondary winding. be configured such that the stability of the power source is ensured by a feedback path; A flyback power supply featuring 2. The drive device excites the transformer in a continuous mode to reduce the magnetic flux within the transformer means. is substantially zero when the drive starts to flow the primary winding current that causes the magnetic flux increase. The flyback according to claim 1, wherein the flyback has a size that is not large. power supply. 3. The gating device is connected between the output terminal and a sensing input of the drive circuit means. 2. A flyover as claimed in claim 1, comprising a controllable series pass device. back power supply. 4. The feedback path means includes a D a DC circuit between a C circuit path and a sensing input of said series pass device and said drive circuit means; The flyback power supply according to claim 3, further comprising a path. 5. The flash drive according to claim 1, wherein the drive device includes a FET transistor. iback power supply. 6. The gate device includes a transistor, and the control terminal includes a transistor. A flyback power supply according to claim 1, comprising a base electrode of. 7. terminal means for receiving a DC power supply voltage input signal whose magnitude varies over a range; Transformer means comprising a primary winding coupled to said terminal means and a secondary winding. and, at least one detection signal input, for outputting a control input signal to said primary winding; The power supply voltage input signal supplies the control electrode of the drive device coupled to the line. A drive with a pulse width modulation (PWM) circuit that periodically controls the primary current provided. dynamic circuit means; It is coupled to the secondary winding to rectify the signal induced in the secondary winding, and outputs the signal accordingly. rectifying means for generating a DC power output voltage at the power terminal; connected between the output terminal and the PWM input to control the PWM circuit and feedback path means for maintaining the power supply output signal at a desired level; In the flyback power supply comprising: a holding device connected to the power terminal and the PWM detection input; It includes a sample and hold circuit with a controllable gate device. A control terminal of the gate device receives a switching signal determined by the PWM output. The gate device is configured such that the drive device controls the magnetic flux within the transformer means. When the primary winding current is made to flow, it increases and stores energy. so that the output signal of the recording power source is effectively sampled by the holding device. The holding device alternately opens and closes according to the PWM output, and the holding device The magnetic flux of the transformer means decreases and the stored energy is transferred to the secondary winding and the rectifier. is effectively disconnected from said output terminal except when being supplied to the Sampling is performed at times other than when energy is transferred from the primary winding to the secondary winding. The power source is configured to ensure stability of the power source by a discontinuous feedback path. A flyback power supply characterized by: 8. The drive device excites the transformer in a continuous mode to reduce the magnetic flux within the transformer means. However, when the drive device starts to periodically flow the primary winding current that causes the magnetic flux increase, The frame according to claim 7 is adapted to have a substantially non-zero size. Ryback power supply. 9. The gating device is connected between the output terminal and a sensing input of the drive circuit means. 8. A flyover as claimed in claim 7, comprising a controllable series pass device. back power supply. 10. The feedback path means is connected between the series path device and the output terminal. a DC circuit path and a DC between said series pass device and a sensing input of said drive circuit means; 10. The flyback power supply according to claim 9, further comprising a circuit path. 11. 8. The drive device according to claim 7, wherein the drive device includes a FET transistor. Ryback power supply. 12. The gate device has a transistor, and the control terminal has a transistor. The flyback power supply according to claim 7, having a base electrode of .