JP2008236998A - Multi-output power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-output power supply capable of synchronizing oscillation frequencies between synchronous rectification circuits of a first output circuit and a second output circuit, without receiving a supply of drive signal to a switching element. <P>SOLUTION: In the multi-output power supply, an auxiliary winding 8D is wound on a transformer 8. The multi-output power supply comprises resistors 21 and 22 which act as a first driving means and supply a drive signal to a rectification switch element 13 by utilizing a voltage induced at a secondary winding 8B when a switching element 9 is turned on, a second driving means 81 which supplies a drive signal to a commutation switch element 14 by utilizing a voltage induced at the auxiliary winding 8D when the switching element 13 is turned off, and a third driving means 82 which alternately supplies a drive signal to a rectification switch element 31 and a commutation switch element 32 by utilizing occurrence timing of the voltage induced at the auxiliary winding 8D. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-output power supply apparatus suitable for power supply such as a PC (personal computer).

  As a conventional multi-output power supply device of this type, for example, Patent Document 1 discloses a device that supplies an output voltage to each load from a common single transformer via a plurality of output circuits. In this patent document 1, in order to rectify the induced voltage of the secondary winding of the transformer, a rectifying switching transistor that is turned on and off in synchronization with the switching element on the primary side of the transformer is provided in each output circuit. Yes.

  FIG. 3 is a circuit diagram showing an example of a multi-output power supply device incorporating such a synchronous rectifier circuit. In the figure, reference numeral 1 denotes a DC power supply for supplying a DC input voltage Vi between the input terminals 2A and 2B of the power supply apparatus 101, 3 denotes an input capacitor connected between the input terminals 2A and 2B. In response to the power supply from, a plurality of output voltages Vo1 to Vo3 described later are output.

  The power supply apparatus 101 includes first to third output circuits 5 to 7 that generate three output voltages Vo1 to Vo3 that are adapted to the operating voltage for a personal computer. The first output circuit 5 to the third output circuit 7 are configured such that the first output circuit 5 and the second output circuit 6 have a transformer 8 and a switching element 9 provided on the primary side of the transformer 8 as a common inverter. The secondary output 8B, which is magnetically coupled to the primary winding 8A of the transformer 8, is supplied with power, and the third output circuit 7 is another secondary that is also magnetically coupled to the primary winding 8A of the transformer 8. The power supply is received from the winding 8C. Here, on the primary side of the transformer 8, a series circuit of a primary winding 8A and a switching element 9 made of, for example, a MOSFET is connected between the input terminals 2A and 2B, but another well-known circuit configuration is adopted. May be.

  Reference numeral 11 denotes a PWMIC as a main control unit that supplies a pulse drive signal having a conduction width corresponding to the fluctuation of the output voltage Vo1 to the gate of the switching element 9. The switching element 9 is simultaneously turned on and off at a predetermined timing by the PWMIC 11 that monitors the output voltage Vo1 so that the output voltage Vo1 is stabilized. Thereby, the input voltage Vi is intermittently applied to the primary winding 8 of the transformer 8.

  The first output circuit 5 is connected to the secondary winding 8B of the transformer 8, and is connected to the synchronous rectifier circuit including the rectifier switch element 13 and the commutation switch element 14, and the synchronous rectifier circuit 15, and the choke coil 16 A smoothing circuit 19 for supplying a smoothed output voltage Vo1 of, for example, +5 V generated between both ends of the smoothing capacitor 17 to a load (not shown) connected between the output terminals 18A and 18B by the smoothing capacitor 17; Composed. Among them, the rectifying switch element 13 and the commutation switch element 14 are both configured by MOSFETs, the drain of the rectifying switch element 13 is connected to the non-dot side terminal of the secondary winding 8B, and the source of the rectifying switch element 13 is Connected to the negative output terminal 18B. The drain of the commutation switch element 14 is connected to a connection point between the dot side terminal of the secondary winding 8B and one end of the choke coil 16, and the source of the commutation switch element 14 is connected to the source of the rectification switch element 13. Connected to the negative voltage supply line between the output terminal 18B. The other end of the choke coil 16 constituting the smoothing circuit 19 is connected to the positive output terminal 18A, and the smoothing capacitor 17 is connected between both ends of the output terminals 18A and 18B.

  Reference numerals 21 and 22 denote voltage-dividing resistors connected in series for supplying a driving signal for synchronizing with the switching element 9. The voltage dividing resistors 21 and 22 are connected between both ends of the secondary winding 8 </ b> A of the transformer 8, and the connection point of the voltage dividing resistors 21 and 22 is connected to the gate of the rectifying switch element 13. Accordingly, when a positive voltage is induced at the dot side terminal of the secondary winding 8B as the switching element 9 is turned on, a voltage sufficient to turn on the rectifying switch element 13 is generated. The energy supplied from the secondary winding 8B is supplied to the gate of the element 13 and supplied to the load between the smoothing capacitor 17 and the output terminals 18A and 18B through the choke coil 16.

  On the other hand, as a drive signal to the commutation switch element 14, a signal obtained by inverting the drive signal given from the PWMIC 11 to the switching element 9 is given to the gate of the commutation switch element 14 through the diode 23. In this case, the inverted signal generation circuit includes a drive transformer 26 that insulates and transmits a drive signal from the PWMIC 11 on the primary side of the transformer 8 to the secondary side of the transformer 8, and an output voltage Vo 3 (described later) via a diode 27. When applied as an operating voltage and the drive signal from the PWMIC 11 turns to L (low) level, the transistor 28 as an inverter that outputs an H (high) level inversion signal Vx sufficient to turn on the commutation switch element 14. , 29. Reference numeral 24 denotes a resistor for discharging the gate charge of the commutation switch element 14, and reference numeral 30 denotes a filter capacitor that allows only a signal component to pass through the primary winding of the drive transformer 26 at a high frequency.

  With the above configuration, while the drive signal of H level is applied from the PWMIC 11 to the switching element 9, the rectifying switch element 13 is turned on, while the voltage level of the inverted signal Vx and thus the gate of the commutation switch element 14 is “L”. The commutation switch element 14 is turned off. Thereafter, when the drive signal from the PWMIC 11 to the switching element 9 changes to L level, the voltage level of the inverted signal Vx becomes “H”, the diode 23 becomes conductive, and the gate of the commutation switch element 14 is driven to H level. A signal is supplied, and the commutation switch element 14 is turned on. At this time, the positive voltage is induced at the non-dot side terminal of the transformer 8, so that the rectifying switch element 13 is turned off, and the energy stored in the choke coil 16 through the commutation switch element 14 is converted to the smoothing capacitor 17. And supplied to a load between the output terminals 18A and 18B.

  Next, the configuration of the second output circuit 6 will be described. The second output circuit 6 receives, as an input, a voltage induced in the secondary winding 8B of the transformer 8, and supplies an output voltage Vo2 of 3.3V, for example, to a load (not shown) between the output terminals 38A and 38B. Operates as a post regulator. More specifically, the second output circuit 6 includes a synchronous rectifier circuit 33 including a series circuit of a rectifier switch element 31 and a commutation switch element 32 connected between both ends of the secondary winding 8B, and the synchronous rectifier circuit. 33 and a smoothing circuit 36 that supplies a smoothed output voltage Vo2 generated across the smoothing capacitor 35 to the load between the output terminals 38A and 38B by the choke coil 34 and the smoothing capacitor 35. Is done.

  The rectifying switch element 31 and the commutation switch element 32 are both constituted by MOSFETs, but are synchronized with the switching element 9 and thus the rectification switch element 13 and the commutation switch element 14 by each drive signal from a driving IC 41 described later. Thus, the operation is alternately turned on and off. When the switching element 9 and the rectifying switch element 13 are turned on, the rectifying switch element 31 is turned on after a certain delay time, the commutation switch element 32 is turned off, and the energy from the secondary winding 8B is converted into the choke coil 34. To the load between the smoothing capacitor 35 and the output terminals 38A and 38B. When the switching element 9 and the rectifying switch element 13 are turned off, the commutation switch element 32 is turned on, the rectifying switch element 31 is turned off, and the energy stored in the choke coil 34 is converted into the smoothing capacitor 35, It is sent out to a load connected between the output terminals 38A and 38B.

  Reference numeral 41 denotes a driving IC as driving means for supplying driving signals to the rectifying switch element 31 and the commutation switch element 32, respectively. When the voltage level of the ramp signal Vy output from the ramp waveform generation circuit 45, which will be described later, reaches the internally set threshold value, the driving IC 41 generates a driving voltage having an H level sufficient to drive the rectifying switch element 31. When the gate of the commutation switch element 32 is set to the “L” voltage level and the voltage level of the ramp signal Vy falls below the threshold value, the commutation switch element 32 is supplied to the gate of the rectifying switch element 31. An H level driving voltage sufficient for driving is supplied to the gate of the commutation switch element 32, while the gate of the rectifying switch element 31 is set to the “L” voltage level. That is, the rectifying switch element 31 and the commutation switch element 32 are alternately supplied with an H level drive voltage.

  On the other hand, the ramp waveform generation circuit 45 includes a voltage-current conversion circuit 46 that generates a current corresponding to the voltage level of the output voltage Vo2, a capacitor 47 that is charged with the current generated by the voltage-current conversion circuit 46, A charge / discharge control element 48 which is connected between both ends of the capacitor 47 and is turned on when the inverted signal Vx rises and discharges the capacitor 47, and turns off when the inverted signal Vx falls and makes the capacitor 47 chargeable. And composed of Among them, the voltage-current conversion circuit 46 receives the operating voltage from the diode 27 and generates a detection signal corresponding to the output voltage Vo2 by the resistors 51 to 53 and the shunt regulator 54, and this detection signal is amplified by the amplifier. While the reference voltage obtained by dividing the stabilized output voltage Vo3 by the resistors 56 and 57 is supplied to the non-inverting input terminal of the amplifier 55 while being supplied to the inverting input terminal 55, amplification is performed according to the voltage level of the detection signal. A signal is output from the output terminal of the amplifier 55, and a known first current mirror circuit formed by combining two transistors 58 and 59 and a known second current formed by combining another two transistors 60 and 61. A current corresponding to the amplified signal from the amplifier 55 is generated by the mirror circuit and supplied to the capacitor 47. Reference numeral 62 denotes a current limiting resistor interposed between the transistors 59 and 60.

  The third output circuit 7 is configured to stabilize the third output voltage Vo3 by the mag amplifier 71 and the mag amplifier control unit 72 that controls the current flowing through the mag amplifier 71. In addition, the third output circuit 7 includes a rectifier circuit including a rectifier diode 73 and a commutation diode 74, and a smoothing circuit including a choke coil 75 and a smoothing capacitor 76, respectively. In this case, as the switching element 9 is turned on, when a voltage that causes the rectifier diode 73 to be conducted to the tertiary winding 8C of the transformer 8 is induced, the tertiary winding 8C passes through the choke coil 75. Electric power is supplied to the smoothing capacitor 76 and a load (not shown) between the output terminals 78A and 78B connected to each end of the smoothing capacitor 76, and energy is stored in the choke coil 75. The energy stored in the choke coil 75 is sent to the load between the output terminals 78A and 78B when the switching element 9 is turned off and the commutation diode 74 is turned on in place of the rectifier diode 73. Three output voltage Vo3 is supplied. Further, the mag amplifier control unit 72 uniquely stabilizes the third output voltage Vo3 by controlling the current flowing through the mag amplifier 71 in accordance with the fluctuation of the third output voltage Vo3.

  Next, the operation of the driving IC 41 and the ramp waveform generating circuit 45 will be described with reference to the waveform diagram of FIG. FIG. 4 shows an operation waveform of each part in a steady state. The voltage waveform of the drive signal from the PWMIC 11 is at the top, and hereinafter, the voltage waveform of the inverted signal Vx, the voltage waveform of the ramp signal Vy, The gate-source voltage waveform of the current switch element 32 and the gate-source voltage waveform of the rectifier switch element 31 are shown.

  In the figure, while the HIC drive signal is output from the PWMIC 11 and the switching element 9 and the rectifying switch element 13 of the first output circuit 5 are on, the inverted signal Vx is “L”, that is, a negative voltage level. The commutation switch element 14 of the first output circuit 5 is turned off, and the charge / discharge control element 48 of the ramp waveform generation circuit 45 is also turned off. Therefore, from the moment when the inverted signal Vx is switched to a negative voltage level, a current corresponding to the voltage level of the output voltage Vo2 flows into the capacitor 47, and the voltage of the ramp signal Vy that is the voltage across the capacitor 47 is It rises linearly as time passes. The ramp signal Vy rises faster as the output voltage Vo2 is lower at this time. However, until the threshold VTH set by the drive IC 41 is reached, an H level drive signal is sent from the drive IC 41 to the commutation switch element 32. On the other hand, the gate voltage level of the rectifying switch element 31 becomes “L”, the rectifying switch element 31 is turned off, and the commutation switch element 32 is turned on.

  Eventually, when the voltage level of the ramp signal Vy rises and reaches the threshold value VTH set by the driving IC 41, an H level driving signal is supplied from the driving IC 41 to the rectifying switch element 31. The gate voltage level of the switch element 32 becomes “L”, the rectifying switch element 31 is turned on, and the commutation switch element 32 is turned off. Therefore, the voltage induced in the secondary winding 8 </ b> B of the transformer 8 is applied to the choke coil 34 and the smoothing capacitor 35 through the rectifying switch element 31, and energy is stored in the choke coil 34. Note that the voltage level of the ramp signal Vy does not increase any more when the capacitor 47 is fully charged. Thus, the reason for turning on the rectifying switch element 31 of the second output circuit 6 behind the switching element 9 and the rectifying switch element 13 is to suppress the influence of the leakage of the transformer 8.

Thereafter, when the drive signal from the PWMIC 11 is switched to the L level and the switching element 9 and the rectifying switch element 13 of the first output circuit 5 are turned off, the voltage level of the inverted signal Vx is changed to “H”, that is, positive. As a result, the charge / discharge control element 48 of the ramp waveform generation circuit 45 is turned on, the both ends of the capacitor 47 are short-circuited, and the capacitor 47 is discharged. When the charge / discharge control element 48 is turned on, the voltage of the ramp signal Vy rapidly becomes 0 and falls below the threshold value VTH. Therefore, while the H level drive signal is supplied to the commutation switch element 32, the gate voltage level of the rectifying switch element 31 is switched to “L”, and then the H level drive signal is output from the PWMIC 11, Until the voltage of the signal Vy reaches the threshold value VTH, the rectifying switch element 31 is turned off, and the commutation switch element 32 remains on. During this period, the energy stored in the choke coil 34 until then is sent to the smoothing capacitor 35 and a load connected between the output terminals 38A and 38B.
Japanese Patent No. 3572525

  The conventional power supply device 101 shown in FIG. 2 synchronizes each oscillation frequency of the synchronous rectifier circuit 15 of the first output circuit 5 that is the main channel and the second output circuit 6 that is the post regulator by the ramp waveform generation circuit 45. In this case, the ramp waveform generation circuit 45 requires input of a drive signal from the PWMIC 11 on the primary side of the transformer 8. For this reason, the drive transformer 26 must be provided for the insulation between the primary side and the secondary side, the mounting space for other circuit components is reduced, and the control unit of the second output circuit 6 including the ramp waveform generation circuit 45 is provided. There was a concern that it could not be concentrated on the secondary side of the transformer 8.

  The present invention has been made paying attention to each of the above-mentioned problems, and the oscillation frequency is synchronized between the respective synchronous rectifier circuits of the first output circuit and the second output circuit without receiving a drive signal supplied to the switching element. It is an object of the present invention to provide a multi-output power supply device capable of taking off.

  In order to achieve the above object, the present invention supplies the first output voltage by rectifying and smoothing the voltage induced in the secondary winding of the transformer by switching the switching element connected to the primary winding of the transformer. In a multi-output power supply device comprising: a first output circuit; and a second output circuit that rectifies and smoothes the voltage induced in the secondary winding of the transformer and supplies a second output voltage. The first output circuit includes a first synchronous rectification circuit including a first rectification switch element and a first commutation switch element that are alternately turned on and off in synchronization with the switching element, and the second output circuit includes: A second synchronous rectifier circuit having a second rectifying switch element and a second commutation switch element that are alternately turned on and off in synchronization with the switching element, and an auxiliary winding wound around the transformer; First driving means for supplying a drive signal to the first rectifying switch element using a voltage induced in the secondary winding when the switching element is turned on, and the auxiliary winding when the switching element is turned off Second drive means for supplying a drive signal to the first commutation switch element using the induced voltage, and the second rectifier switch element and the second rectifying switch element using the generation timing of the voltage induced in the auxiliary winding. And third driving means for alternately supplying a driving signal to the second commutation switch element.

  In this case, the third driving means discharges the capacitive element when a voltage is induced in the auxiliary winding when the switching element is turned off and the capacitive element charged with a current corresponding to the second output voltage. When the voltage is no longer induced in the auxiliary winding, a charge / discharge control element that starts charging the capacitive element, and whether the voltage level of the capacitive element reaches a threshold value, the second rectifying switch element And drive signal output means for switching a drive signal supplied to the second commutation switch element.

  According to the first aspect of the present invention, the first rectifying switch element of the first output circuit is supplied with the drive signal based on the voltage induced in the secondary winding of the transformer, and is synchronized with the switching element being turned on / off. Then, the first rectifying switch element is also turned on / off. The first commutation switch element of the first output circuit is supplied with a drive signal from an auxiliary winding different from the secondary winding of the transformer using an induced voltage generated when the switching element is turned off. It turns on and off alternately with one rectifying switch element. Therefore, the first synchronous rectifier circuit can be turned on and off using the induced voltage of the secondary winding and auxiliary winding of the transformer without receiving a drive signal supplied to the switching element.

  Further, the present invention is characterized in that the on / off timing of the second rectifying switch element and the second commutation switch element of the second output circuit is determined by the generation timing of the voltage induced in the auxiliary winding. That's what it means. Therefore, the third driving means for supplying a driving signal to the second rectifying switching element and the second commutation switching element also receives the driving signal to the switching element, and the primary and secondary transformers as in the prior art. A drive transformer in between can be eliminated. In addition, the generation timing of the voltage induced in the auxiliary winding is synchronized with the on / off of the switching element, so that the oscillation frequency is synchronized between the synchronous rectifier circuits of the first output circuit and the second output circuit. Is possible.

  According to the invention of claim 2, the degree of increase of the voltage level of the capacitive element changes according to the second output voltage. Therefore, the second rectification switch element can be turned on after the first rectification switch element is turned on with a time difference corresponding to the second output voltage.

  Hereinafter, a preferred embodiment of a multi-output power supply device according to the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 3 shown in the prior art example, and the description of the common part is abbreviate | omitted as much as possible to avoid duplication.

  FIG. 1 shows a circuit configuration of a multi-output power supply apparatus 10 proposed in the present embodiment. Here, as a first driving means for supplying a driving signal to the rectifying switch element 13, a series circuit including resistors 21 and 22 in which the connection point is connected to the gate of the rectifying switch element 13 is a secondary winding as in the conventional example. Connected between both ends of the line 8B. In addition, in this embodiment, the drive signal from the PWMIC 11 is supplied only to the switching element 9 on the primary side of the transformer 8 and is not supplied to the secondary side of the transformer 8. Instead, an auxiliary winding 8D magnetically coupled to the primary winding 8A is wound around the transformer 8, and a drive signal for the commutation switch element 14 is utilized using a voltage induced in the auxiliary winding 8D. The second driving means 81 for generating the second driving means 81 and the third driving means 82 for determining the switching timing of the driving signal to the rectifying switch element 31 and the commutation switch element 32 are provided. Therefore, here, the first to third output circuits 5 to 7 are configured so that the three output voltages Vo1 to Vo3 are obtained from the secondary windings 8B and 8C and the auxiliary winding 8D by one transformer 8. ing. The configuration of each other part is the same as that shown in FIG.

  The second driving means 81 includes a switch element 83 formed of a MOSFET having a source and a gate connected between both ends of the auxiliary winding, a resistor 84 connected between the drain and source of the switch element 83, and a drain of the switch element 83. And the resistor 85 connected to the gate of the commutation switch element 14 and the resistor 24 also shown in FIG. As a result, when the switching element 9 is turned on, the input voltage Vi is applied to the primary winding 8A of the transformer 8, and a positive voltage is induced at the dot side terminal of the auxiliary winding 8D, the switching element 83 is turned off. Then, the gate of the commutation switch element 14 becomes “L” level, and the commutation switch element 14 is turned off. At this time, since the rectifying switch element 13 is on, energy from the secondary winding 8B is supplied to the load between the smoothing capacitor 17 and the output terminals 18A and 18B through the choke coil 16 in the first output circuit 5. Is done.

  On the other hand, when the switching element 9 is turned on and the input voltage Vi to the primary winding 8A of the transformer 8 is cut off, a positive voltage is induced at the non-dot side terminal of the auxiliary winding 8D, and the switching element 83 is Turn on. Therefore, the voltage induced in the auxiliary winding 8D is supplied to the gate of the commutation switch element 14 through the switch element 83 and the resistor 85 as an H level drive voltage, and the commutation switch element 14 is turned on. At this time, since the rectifying switch element 13 is off, the energy stored in the choke coil 16 in the first output circuit 5 passes through the commutation switch element 14 to the load between the smoothing capacitor 17 and the output terminals 18A and 18B. Supplied.

  Next, the configuration of the third driving unit 82 will be described. In addition to the driving IC 41, the voltage-current conversion circuit 46, the capacitor 47, and the charge / discharge control element 48 having the same configuration as the conventional example, the third driving means 82 has a positive voltage at the non-dot side terminal of the auxiliary winding 8D. Is induced, the charge / discharge control element 48 is turned off to start charging the capacitor 47, and when a positive voltage is induced at the dot side terminal of the auxiliary winding 8D, the charge / discharge control element 48 is turned on to turn on the capacitor 47. A drive signal output circuit 91 for quickly discharging is provided. The drive signal output circuit 91 includes a switch element 92 composed of a MOSFET in which a source and a gate are connected between both ends of the auxiliary winding 8D, and a voltage dividing resistor 93 connected between the drain and the gate of the switch element 92, And a connection point of the voltage dividing resistors 93 and 94 is connected to the gate of the charge / discharge control element 48.

  Next, the operation of the driving IC 41 and the third driving means 82 will be described with reference to the waveform diagram of FIG. FIG. 2 shows the operation waveform of each part in a steady state. The voltage waveform of the drive signal from the PWMIC 11 is at the top, and hereinafter, the voltage waveform between the terminals of the auxiliary winding 8D (referenced to the dot side terminal). Voltage waveform of the non-dot side terminal) Vz, voltage waveform between the gate and source of the charge / discharge control element 48, voltage waveform of the ramp signal Vy, voltage waveform between the gate and source of the commutation switch element 32, The gate-source voltage waveforms are shown.

  In the figure, while the driving signal of H level is output from the PWMIC 11 and the switching element 9 and the rectifying switch element 13 of the first output circuit 5 are on, the inter-terminal voltage Vz of the auxiliary winding 8D is “L”. That is, the voltage level is negative, the commutation switch element 14 of the first output circuit 5 is turned off, and the gate-source voltage of the charge / discharge control element 48 is also negative voltage level. Turns off. Therefore, from the moment when the inter-terminal voltage Vz of the auxiliary winding 8D is switched to a negative voltage level, a current corresponding to the voltage level of the output voltage Vo2 flows into the capacitor 47, and a ramp signal that is a voltage across the capacitor 47 is obtained. The voltage Vy rises linearly with time. The voltage rise of the ramp signal Vy at this time becomes faster as the output voltage Vo2 is lower. However, until the threshold value VTH set by the driving IC 41 is reached, the driving signal from the driving IC 41 to the commutation switch element 32 has an H level driving signal. Is supplied, the gate voltage level of the rectifying switch element 31 becomes “L”, the rectifying switch element 31 is turned off, and the commutation switch element 32 is turned on.

  Eventually, when the voltage level of the ramp signal Vy rises and reaches the threshold value VTH set by the driving IC 41, an H level driving signal is supplied from the driving IC 41 to the rectifying switch element 31. The gate voltage level of the switch element 32 becomes “L”, the rectifying switch element 31 is turned on, and the commutation switch element 32 is turned off. Therefore, the voltage induced in the secondary winding 8 </ b> B of the transformer 8 is applied to the choke coil 34 and the smoothing capacitor 35 through the rectifying switch element 31, and energy is stored in the choke coil 34.

  Thereafter, when the drive signal from the PWMIC 11 is switched to the L level and the switching element 9 and the rectifying switch element 13 of the first output circuit 5 are turned off, the voltage level of the inter-terminal voltage Vz of the auxiliary winding 8D turns to plus. As a result, the charge / discharge control element 48 of the ramp waveform generation circuit 45 is turned on, the both ends of the capacitor 47 are short-circuited, and the capacitor 47 is discharged. When the charge / discharge control element 48 is turned on, the voltage of the ramp signal Vy rapidly becomes 0 and falls below the threshold value VTH. Therefore, while the H level drive signal is supplied to the commutation switch element 32, the gate voltage level of the rectifying switch element 31 is switched to “L”, and then the H level drive signal is output from the PWMIC 11, Until the voltage of the signal Vy reaches the threshold value VTH, the rectifying switch element 31 is turned off, and the commutation switch element 32 remains turned on. During this period, the energy stored in the choke coil 34 until then is sent to the smoothing capacitor 35 and a load connected between the output terminals 38A and 38B.

  As described above, in this embodiment, the voltage induced in the secondary winding 8B is rectified and smoothed by the switching of the switching element 9 connected to the primary winding 8A of the transformer 8, and the first output voltage Vo1 is supplied. A multi-output power supply device comprising: a first output circuit 5; and a second output circuit 6 that receives a voltage induced in the secondary winding 8B as an input, rectifies and smoothes the voltage, and supplies a second output voltage Vo2. 10, the first output circuit 5 includes a synchronous rectification circuit 15 including a rectification switch element 13 and a commutation switch element 14 that are alternately turned on and off in synchronization with the switching element 9, and the second output circuit 6 is also the same. In addition, a synchronous rectifier circuit 33 including a rectifier switch element 31 and a commutation switch element 32 that are alternately turned on and off in synchronization with the switching element 9 is provided. The auxiliary winding 8D is wound around the transformer 8, and first driving means for supplying a driving signal to the rectifying switch element 13 by using a voltage induced in the secondary winding 8B when the switching element 9 is turned on. And the second driving means 81 for supplying a drive signal to the commutation switch element 14 using the voltage induced in the auxiliary winding 8D when the switching element 13 is turned off, and the auxiliary winding 8D. And third driving means 82 for alternately supplying a drive signal to the rectifying switch element 31 and the commutation switch element 32 using the generation timing of the induced voltage.

  In this way, the rectifying switch element 13 of the first output circuit 5 is supplied with a drive signal based on the voltage induced in the secondary winding 8B of the transformer 8, and in synchronization with the switching element 9 being turned on and off, The rectifying switch element 13 is also turned on / off. Further, the commutation switch element 14 of the first output circuit 5 receives a drive signal from an auxiliary winding 8D different from the secondary winding 8B of the transformer 8 by using an induced voltage generated when the switching element 9 is turned off. It is supplied and turned on and off alternately with the rectifying switch element 13. Therefore, the synchronous rectification circuit 15 can be turned on and off by using the induced voltage of the secondary winding 8B and the auxiliary winding 8D of the transformer 8 without receiving a drive signal supplied to the switching element 9. it can.

  Furthermore, in this case, the on / off timing of the rectifying switch element 31 and the commutation switch element 32 of the second output circuit 5 is determined by the generation timing of the voltage induced in the auxiliary winding 8D. For this reason, the third driving means 82 for supplying drive signals to the rectifying switch element 31 and the second commutation switch element 32 does not receive the drive signal supplied to the switching element 9, so The drive transformer between the secondary can be eliminated. In addition, since the generation timing of the voltage induced in the auxiliary winding 8D is synchronized with the on / off of the switching element 9, between the synchronous rectifier circuits 15 and 33 of the first output circuit 5 and the second output circuit 6. It becomes possible to automatically synchronize the oscillation frequency.

  Then, by eliminating the need for the drive transformer, the control unit including the drive signal output circuit 91 can be concentrated on the secondary side of the transformer 8, so that the primary and secondary creepage distances of the transformer 8 can be easily secured. Further, when the power supply device 10 is mounted on a limited board (not shown), a large mounting space can be secured because the drive transformer is unnecessary.

  In the circuit shown in FIG. 1, when the operation of the power supply device 10 is interrupted, the third output voltage Vo3, which is the operating voltage of the drive signal output circuit 91, may continue to be output for a while, thereby causing self-excited oscillation. However, by adjusting the element constants around the commutation switch element 14 and the switch element 92, the sink current associated with such self-excited oscillation can be reduced.

  Further, in the third driving means 82 in this embodiment, a voltage is induced in the capacitor 47 as a capacitive element charged with a current corresponding to the second output voltage Vo2 and the auxiliary winding 8D when the switching element 9 is turned off. Depending on whether or not the voltage level of the capacitor 47 reaches the threshold value VTH and the charge / discharge control element 48 that starts charging the capacitor 47 at the timing when the capacitor 47 is discharged at the timing when the voltage is no longer induced in the auxiliary winding 8D. And a drive signal output circuit 91 as drive signal output means for switching drive signals supplied to the rectifying switch element 31 and the second commutation switch element 32.

  As a result, the degree of increase in the voltage level of the ramp signal Vy, which is the voltage across the capacitor 47, changes according to the second output voltage Vo2. Therefore, the rectifying switch element 31 can be turned on after the rectifying switch element 13 is turned on with a time difference corresponding to the second output voltage Vo2.

  In addition, this invention is not limited to the said Example, A various deformation | transformation implementation is possible in the range of the summary of this invention. The circuit configuration of the power supply apparatus 10 illustrated in FIG. 1 is merely an example, and it is needless to say that another circuit configuration that realizes an equivalent function may be adopted.

It is a circuit block diagram of the multiple output power supply device in one Embodiment of this invention. FIG. 2 is an operation waveform diagram of each part in the circuit configuration of FIG. 1. It is a circuit block diagram of the multiple output power supply device in a prior art example. FIG. 4 is an operation waveform diagram of each part in the circuit configuration of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 1st output circuit 6 2nd output circuit 8 Transformer 8A Primary winding 8B Secondary winding 8D Auxiliary winding 9 Switching element 13 Rectification switch element (1st rectification switch element)
14 Commutation switch element (first commutation switch element)
15 Synchronous rectifier circuit (first synchronous rectifier circuit)
21, 22 Resistance (first driving means)
31 Rectifier switch element (second rectifier switch element)
32 Commutation switch element (second commutation switch element)
33 Synchronous rectifier circuit (second synchronous rectifier circuit)
47 Capacitor (capacitive element)
48 charge / discharge control element 81 second driving means 82 third driving means 91 driving signal output circuit (driving signal output means)

Claims (2)

A first output circuit for rectifying and smoothing a voltage induced in the secondary winding of the transformer by switching of a switching element connected to the primary winding of the transformer and supplying a first output voltage;
In a multi-output power supply apparatus comprising: a second output circuit that rectifies and smoothes the voltage induced in the secondary winding of the transformer and supplies a second output voltage;
The first output circuit includes a first synchronous rectification circuit including a first rectification switch element and a first commutation switch element that are alternately turned on and off in synchronization with the switching element,
The second output circuit includes a second synchronous rectification circuit including a second rectification switch element and a second commutation switch element that are alternately turned on and off in synchronization with the switching element,
And auxiliary winding wound around the transformer,
First driving means for supplying a driving signal to the first rectifying switch element using a voltage induced in the secondary winding when the switching element is turned on;
Second driving means for supplying a driving signal to the first commutation switch element using a voltage induced in the auxiliary winding when the switching element is off;
And third driving means for alternately supplying drive signals to the second rectifying switch element and the second commutation switch element by using the generation timing of the voltage induced in the auxiliary winding. Multi-output power supply. The third driving means includes a capacitive element charged with a current corresponding to the second output voltage;
When a voltage is induced in the auxiliary winding when the switching element is turned off, the capacitive element is discharged, and when no voltage is induced in the auxiliary winding, a charge / discharge control element that starts charging the capacitive element;
Drive signal output means for switching drive signals supplied to the second rectifying switch element and the second commutation switch element depending on whether or not the voltage level of the capacitive element reaches a threshold value. The multi-output power supply device according to claim 1.

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