JPS58151870A - Switching power supply circuit - Google Patents

Abstract

PURPOSE:To reduce switching noises by driving a switching transistor and a switching transformer by signals having small higher-harmonic component content. CONSTITUTION:When a transistor TR13 is turned ON, a capacitor C13 is discharged instantaneously, and transistors TR14, TR15 are turned OFF continuously, but a transistor TR7 is turned ON slowly and a transistor TR8 is done so because a capacitor C14 is charged slowly at that time. Consequently, the rise of voltage applied to the primary winding N1 of the switching transformer is made gentle. When the transistor TR13 is turned OFF, the capacitor C13 is charged slowly, the transistors TRs 14, 15 are turned ON slowly, the capacitor 14 is charged slowly, and the TR7 is turned ON slowly and the TR8 is done so. Accordingly, the switching transformer T1 is driven by voltage changing smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching power supply circuit with reduced noise.

The biggest drawback of conventional switching power supplies is the generation of switching noise. Switching noise is caused by dust between the positive and negative terminals of the output electrons) -? There are I-mode noise, common-mode noise that occurs in the same phase between input and output or case and output, and radiation noise that propagates in space, but it is difficult to eliminate them except for 7-dimensional real-mode noise. For this reason, when used as a power supply for an audio amplifier, these noises may be amplified and interfered with the output of the amplifier, or may be
Due to RFI (radio frequency interference), good and clear BIN reception was not possible, and switching power supplies were not put to practical use as power sources for audio equipment.

This idea was made in view of the above points.

Switching power supply circuit V with reduced switching noise
*It is something to be compensated for.

This invention reduces switching noise by driving a switching transistor and a switching transformer with a small switching signal of a high 1iIII level.

First, the present invention will be explained in detail using a modified half-bridge type switching weight circuit V shown in Fig. @1.

In Fig. 1, the AC voltage supplied from AC voltage ml is rectified by diode bridge D1 and capacitor C5.
Smoothed, switching transistors TR7, TR8
is applied to Primary voltage of switching transformer T1 @N
Is 1 the transistor TR? .

It is connected to the connection point of TR8 via a capacitor C7v.

Transistors TR7 and TR8 are switching control circuit 2
It is turned on and off alternately by a pulse signal from. When the transistor TR7 is turned on, the transformer is connected to the transistor R7 via the capacitor C1'.
@ This direction (arrow m) KL flow flows, transistor TR
When transistor TR7 is turned on, the electric charge photoelectrically transferred to capacitor C7 is transferred from transistor TR8 to the transformer. 5 directions towards NIK (arrow i) K
Due to the switching operation described above, a voltage is generated in the transformer secondary winding -N2ff. This voltage is converted into a DC voltage voK by the W direct circuit D4 and the smoothing circuit 3.
f is output and output K11il is output.

#A difference tI The device 4 converts the value of this output voltage v0 into the application rate voltage V
Detect the difference between r@f and drive the pulse smooth fi 41E path 5v according to the detection result.
#A difference amplification! Generates g1 signal whose amplitude is compared with the output of No. 4. In other words, when the output voltage becomes lower than the set value, the pulse width of the switching pulse is widened to lengthen the on time of transistors TR7 and TR8. In addition, when the output voltage v0 becomes higher than the set value, the output voltage for switching] (
transistors TR7 and TR8 by narrowing the loop width)
The on-time of V4/li is reduced, and the amount of power supplied to the secondary is reduced. This is intended to stabilize the output voltage v0 by KL.

By the way, the high-1 round am component included in the switching noise includes a high frequency component of the switching transistor! 11 (switching signal No. I). High 1 included in switching signal
The frequency f of the iiiIltlL component can be thought of as fs=-a, where the rise time of the
The frequency fs of the m component increases 0, for example -1■0. i
If p@, f1 area 101 &, if 11 companies 1 ps, f m = 1 seed i. In the past, the switching signal was @21V [rising as shown by the solid line].

A type with a steep fall was used. In this case, if you analyze the spectrum of switching noise, it will be 20&~ (fund)
It is distributed up to a fairly high frequency range of 1 kHz, which causes interference with AM reception.・Therefore, in this invention, the switching signal v is rounded to a high value like the chaste woman in Figure 2.
By reducing the 4-wave component V, the KL reswitching noise is reduced.

Embodiment 5 of the present invention will be described below with reference to attached page J. Each II below! In one example, the configuration of the entire power supply circuit is the same as that in the above-mentioned 1-, and each part is given the same reference numeral as in the 1-. Each of these actual IM examples starts up,
This section describes various configuration examples of circuits that create a switching circuit 4f1 with a blunted falling edge.

In the switching control (b) path 2 of Scheme 3 (2), the bases of the transistors TR1 and 'rR2 have a pulse width fli.
AC TLK pulse CI is applied from 1 circuit 5 (4th
– the base is connected. Further, the collector of the transistor 〒R2 is connected to the base of the transistor TR4.

The collector of transistor TR4 is connected to etranraster T16.
0 base kill! It is continued. The llff point of the transistor TR5°Ti16 is connected to the primary gate 11N3 of the drive transformer 〒2 via the capacitor C6v.

Note that the diodes D5% and D6 connected to the resistors R9 and R1]K respectively are the switching transistors T'BY,
This is to quickly turn off TRgV. In the above configuration, when a pulse is applied to the transistor TB1 and it turns on, this Kf turns off the transistor TR3, and the transistor TBS turns on and turns off the transformer. 1IN 3K Mark the voltage with the polarity shown in the diagram 7J1. In addition, along with this, the power supply C6 is photoelectrically charged.

When the pulse to the transistor TRIK falls, the transistor TRI is turned off, the transistor TR3 is turned on, and the transistor TRIK is turned off. Therefore, a voltage of 11 mN 3 K← is no longer applied to the drive transformer.

Subsequently, when the transistor TR2 is turned on, the transistor TR4 is turned off and the transistor TR6 is turned on. Therefore, the photoelectric charge in the capacitor C6 applies a voltage of opposite polarity to that shown in the figure to the drive transformer 4141N3.

When the transistor TR2 is turned off, the transistor R4 is turned on, and the transistor TR6 is turned off, so that no voltage is applied to the drive transformer N3.

The above operation is regarded as one cycle, and the transistors TR5 and T
By alternately turning R6 on and off.

Drive transformer T2 is driven.

The secondary 1llK of the drive transformer 〒2 has two windings N4
, N5 are cast with mutually opposite polarities. These output signals are applied as switching signals to the switching transistors TR7 and T18, respectively.

By the way, in the switching control circuit 2 shown in FIG. 1g3, the rise and fall of the switching signal are blunted by the capacitors C1 to C4. This house, capacitor C
1 is connected to the collector of the transistor TRI, and the capacitor C3 is connected to the collector of the transistor TRI.
are connected to the collector of transistor TR3, and when transistor 1'R1 is turned on, capacitor C
1 immediately discharges and turns off transistor TR3. At this time, the capacitor 7tC3 is C3・(R4 and the transistor T
Since it is photoelectronized with a time constant of R50 (combined value of input resistance),
Transistor TR5 turns on gradually to smooth the rise of the illustrated catastrophic voltage applied to the drive transformer 11N3. As a result, the rising edge of the switching transistor TR7K71 (I and switching 4fi) becomes gradual.

Mata, when transistor TRI turns off, capacitor C1
is photoelectronized with a time constant of C1.(combined value of R1, R2, R3 and the input 77 resistance of transistor TR3).

The transistor 83 is gradually turned on. The fall of the illustrated catastrophic voltage applied at this time is made gradual, and the fall of the switching transistor TR7fKMJ is made gradual.

, capacitor C2 is the collector of transistor TR2,
Capacitor C4 is connected to the collector of transistor TR4, respectively! Ribbed. When the transistor Tlt2 is turned on, the capacitor C2 is immediately discharged and the transistor TR4 is turned off. When transistor TR4 turns off, capacitor C4 connects C4・(R8 and transistor TR
The time constant of 6 input resistances) is photovoltaic and transistors! TR6 is gradually turned on to gently control the rise of the voltage of opposite polarity to the voltage applied to the transformer suboptimal 11N3. As a result, the rise of the switching signal applied to the switching transistor TR8 is made gentler.

Also, when the transistor TR2 is turned off, the capacitor C2
is photoelectronized with a time constant of C2 (combined value of R5, R6, R) and the input resistance of transistor TR4), and the transistor T
R4v gradually turns on. At this time, the capacitor C4 is gradually discharged as the transistor TR4 is turned on, and the transistor TR6 is gradually turned off.
The voltage KL, which is applied to I@N3 and has a polarity opposite to that shown in the figure, slowly falls, and the switching voltage applied to the switching transistor TR8 slowly falls.

FIG. 4 shows the waveforms of each part of 1I30. In FIG. 4, the dotted line is a waveform when the output pulse width of the pulse width modulation circuit 5 is widened (when the output voltage is decreased). From Figure 4, switching transistors TR7 and TR
Since the switching transformer T1 and the switching transformer T1 are driven by a signal with reduced high i11 wave components, switching noise is significantly reduced.

58i14F) The modification is based on the simplification of the switching control circuit 2. Here, the pulse width modulation circuit 5
A single output is emitted from the In the control circuit 2, the transistor R9 is driven by the output pulse from the pulse width modulation circuit 5.
The collector of R9 is connected to the base of transistor tWO, and the collector of transistor TRl0 is connected to the base of transistor TWO.
Common to the base of RII and TR12 is Wj! It is continued. Transistor THD.

The connection point of TR12 is the primary +1! of drive transformer T3 via capacitor C9! Connected to Iwao N6.

Therefore, when transistor TR9 is turned on, transistor TRl0 is turned off and transistor TRII is turned on.

The transistor TR12 is turned off, a voltage of the polarity shown in the figure is applied to the drive transformer-next winding N6, and the contact tc9 is photoelectronized. Furthermore, when the transistor TR9 is turned off, the transistor Temo is turned on, turning off the transistor TRII and turning on the transistor TR12, discharging the capacitor C9 and applying a voltage of opposite polarity to that shown in the diagram to the drive transformer second best@N6.

The above operation is considered as one cycle [transistor TR1]
, the drive transformer 3 is driven by alternately turning on and off TR12. Drive transformer secondary reference @N7. Ni has mutually opposite polarity EII! These outputs are output from the switching control circuit 2 as switching signals.

By the way, in the (b) path of circuit 5-, the capacitor C1O
, C11 causes the switching to start.

It makes the fall smooth. Contact? C10 is connected to the collector of the transistor TR9, and the capacitor C1l is connected to the collector of the transistor TR10. When transistor TR9 turns on, contact t
C10 is immediately discharged and transistor TRl0 is turned off. When transistor 〒R10 turns off, capacitor C1l becomes C11-(R16 and transistor?'R1).

The composite value of each input resistance of TR12) is charged, and the transistor TR12 is gradually turned off.
11 (as a result, the voltage applied to the drive transformer-next winding N6 with the polarity shown in the figure gradually rises.

As soon as the transistor TR9 turns off, the capacitor C10 is photoelectrically charged at a rate of CIO. The capacitor C1l is discharged as the transistor TRl0 is turned on, the transistor Tml is gradually turned off, and the transistor TRL2 is gradually turned on.As a result, the capacitor C9 is gradually discharged, and the transformer Good @N611C aI7 with opposite polarity as shown
The rise of the Jo voltage becomes gradual.

Figure 6 shows the waveform of the trough in the circuit of Figure 5. The dotted line is the waveform when the pulse width of the cutting pulse in the pulse width fiilli path 5 is widened.

Si! The common practice is to omit the drive transformer in order to reduce costs.

Note that here as well, the bass width and quality outputs are single, similar to 85-. In addition, the switching control circuit 2, the pulse m change l1
11 circuits 51 oscillators 6. The difference amplifier 4, etc. 11- uses the IE current voltage on the negative side by dividing it with the resistor R2] and the R path.

In the switching control circuit 2 shown in FIG. 1M7, a pulse signal from the pulse width modulation circuit 5 is applied to the transistor TR13. A transistor TR140 base is connected to the collector of the transistor TR13, and a transistor T
A transistor TRL5 is connected to R14. The lid of the transistor TR15 is commonly connected to the bases of the switching transistors TR7 and TR8, and the connection point between the transistors TR7 and TR8 is connected to the switching transformer 11N1 through a capacitor C7.

In the circuit of my■, as mentioned above, the voltage 111 of the error amplifier 64 is
Since the rectified voltage of the primary voltage is used in the
It consists of a photocoupler consisting of L+ and a phototransistor 'rR20.

When the output pulse of the pulse width rm circuit 5 rises, the transistor TR13 is turned on, and the transistor TR14*TR1
5 is turned off. As a result, the switching transistor TR7 is turned on, and the switching transistor TR8 is turned off, so that a voltage of the polarity shown in the figure is applied to the switching transformer MNIK, and the capacitor c7 is photoelectrically charged.

When the output of the pulse width gate g141gl path 5 falls, the transistor τR13 is turned off, and the transistors TR14 and TR1
5 turns on. As a result, the switching transistor TR7 is turned off and TR8 is turned on, so that the voltage stored in the capacitor c7 is discharged through the transistor TR8v, and a voltage having a polarity opposite to that shown in the figure is applied to the switching transformer HN1.

The above operation constitutes one cycle, and the switching transistors TR7 and TR8 are alternately turned on and off.

Switching transformer TI is driven.

What is the secondary output of switching transformer 〒1? I#I.

It is smoothed and output, and its voltage value V. is detected by a photocoupler consisting of a light emitting diode Dm and a phototransistor τ4 with the primary and secondary voltages electrically insulated. Then, the pulse width of the driving pulse of the transistor m3 is adjusted so that the output voltage 1 becomes a specified value.

By the way, in the 7th circuit, capacitors C13 and C
14 allows the switching signal to rise and fall slowly. '3 Capacitor C13 is transistor TR
13, and capacitor C14 is connected to the collector of transistor Tm4. It is connected to the collector of Tm. When transistor TR13 is turned on, capacitor CI3
is immediately discharged, and transistors TR14 and TR15 are subsequently turned off, but at this time, capacitor C14 is gradually photoelectrically charged at a rate of C14 (combined value of input resistance of R26 and transistors TR7 and TR8). Therefore, transistor TR7 is gradually turned on and transistor T118 is turned on.
is gradually becoming less busy. For this reason, the switching transformer
The rise of the 1 pressure applied with the polarity indicated by the suboptimal line NIKa is made gradual.

In other words, when the transistor TR13 is turned off, the capacitor C13 is charged with a time constant of C13. TRL5 is gradually turned on. At this time, the capacitor C14 is the transistor TR
14, τ is gradually discharged as the intestine turns on.

Transistor TR7 gradually turns off, transistor TR8
is gradually turned on. As a result, the switching transformer
The voltage of the shown polarity applied to the next winding N1 gradually attenuates, and the elastic voltage opposite to that shown in the drawing gradually increases KMI, and the switching transformer 1 is driven with a voltage that smoothly changes to Kf.

11F? Figure 8 shows the waveforms of each part in the circuit (2).
This is a waveform when the output pulse width of the l path 5 is widened.

As explained above, according to the present invention, switching transistors and switching transformers are driven with a voltage that gradually improves in quality by cutting off harmonic components, so that switching noise can be reduced.

[Brief explanation of drawings]

Figure 1 is a schematic circuit diagram of a modified half-bridge switching circuit, and Figure 2 is a waveform diagram comparing an example of a conventional switching signal and an example of a switching signal according to the present invention. @3e ! ! J is a circuit diagram showing one embodiment of this invention, and FIG. 4 is #! Operation waveforms of each part in the circuit of 3 [Yes] I! 3. Third. 1 shows another embodiment of the present invention; FIG. 6 is a diagram showing the operation of the circuit shown in FIG. 5; and FIG. 7 is a circuit 1 of this invention. 8 is a circuit diagram showing another embodiment, and FIG.
). TR7, TR8...Switching transistor, TI
... Switching transformer, T2... Drive transformer, 2... Switching control circuit, 4... Switching transformer, C1, C2, C3, C4, CIo. ell, C13, C14...Switching signal high 1IIIf! A capacitor to attenuate the L component. HaO (response to Akira 2nd issue @ 5 to the output of OW scale + jC10's tμcontainer / block C11's voltage/voltage) J1] BU...'M 几] U O■ Procedures Amendment Book April 1980 611 1982 Patent Application No. 34289 2 Name of the invention Switch y da power supply circuit 3 Relationship with the case of the person making the amendment Patent application Person (407) Japan Prefecture lll1l Zokinsha Co., Ltd. 4, Agent Person (zip code 105) Nishi-Shinbashi-chome-1, Minato-ku, Tokyo
No. 8 No. 6 Contents of Doho Bill correction (1) Detect the error with r Vref on page 3, line 18 of the specification, compare " with r Vref to detect the error, and correct it to ". (2) On page 10, line 13, ``It was intended.'' is corrected to the following sentence. In addition, the storage time is shortened by switching the switching transistors TR7 and TR8 in a non-saturated state. (3) "Drive controller" on page 11, line 15. ” to “Taken out.” in line 18 of the same are corrected to the following sentence. Note: When the drive transformer T3 is driven, the secondary winding N7
, N8 have mutually opposite polarity voltages induced therein. The switching transistor T
Connected to the collector of R7. The forward voltage drop VD of the diode F'D7 and the forward voltage drop VD of the diode D8 are set in the following relationship: Vl), > VD, (7). These diodes D7 and D8 are the switching transistor TR8? Non-saturation switching reduces pace accumulation charge and shortens storage time. That is, when a voltage of the polarity shown in the figure is applied to the negative secondary winding N6, a current flows through the diode D8 to the switching transistor TR7 due to the voltage induced in the secondary winding N7, and the switching transistor TR7 turns on. At this time, the collector-emitter voltage VO of the switching transistor TR7
R(ON) is VOR(ON) + vD7 = vD, "VBKV
Bz: Pace-emitter voltage of switching transistor TR7 “VC!E(ON) =”BE + VD@-V
D7 (''). Since the forward voltage drop VD of diode F'D7 and the forward voltage drop VD of diode D8 are set in the relationship of % VD, , ) VD, as described above, From equation (1), the relationship Vex(oN)>VBK is maintained.As a result, the switching transistor TR7 is switched in a non-saturated manner.In addition, a diode-VD9 is connected in parallel to the diode D8. Connected in the opposite direction, when a voltage is induced in the secondary winding N7 in the direction of turning off the switching transistor TR7, it acts like a switching transformer to pull it out. The diodes D7 and D8 have the function of forcibly discharging the charge, and by switching the switching transistor TR7 in a non-saturated state, the diodes D7 and D8 have the function of reducing the 4-phase accumulated charge itself.As a result, when the switching transistor TR7 is turned off, The storage time is shortened. Similarly, a diode DIO1Dll is connected between the drive transformer secondary winding N8 and the switching transistor TR8.
, D12 are connected, and the diodes DIO, Dll
The switching transistor TR8 is switched in a non-saturated manner, and the switching transistor T is switched using the diode FD12.
The storage time of the switching transistor TI'L8 is shortened by attracting the pace accumulated charge of R8. (4) Add the following sentence between the first and second lines of page 17. By the way, in the embodiments described above in FIGS. 3 and 5, the waveforms of both the rising and falling edges of the switching signal are blunted in the portion before the drive stage (drive transformers T2, T3). (Capacitor 01-04
．． 010%011). Also, in the embodiment shown in FIG. 7, the waveform of the falling edge of the switching signal is blunted in the portion before the drive stage (transistors TR14, TR15) (by the capacitor 013). However, in this case, since there is a gain between the drive stage and the final stage (switching transistors TR7, TR8), it is difficult to set the capacitance of these capacitors. Next, FIG. 9 shows an embodiment in which both the rising and falling waveforms of the switching signal are blunted at the portion directly connected to the final stage. In FIG. 9, the AC voltage supplied from AC power supply 1 is rectified by diode bridge D1, and capacitor 058
．． Smoothed with 05b. The voltage of capacitor 05m is applied to switching transformer-secondary winding N1 via switching transistor TR7 and capacitor c7. Further, the voltage of the capacitor 05b is applied to the switching transformer-next winding 11N1 through the switching transistor TR8 and the capacitor 07 in the opposite direction to the above. In the switching control circuit 2, the control circuit 7 controls the transistor 'I based on the signal from the pulse width modulation circuit 5.
'Outputs a signal that turns R16 and TRI 7 on and off alternately. When transistor TRl6 is turned on, drive transformer T4 is driven, and the voltage induced in its secondary winding N9 is applied to the pace of switching transistor TR7 via resistor R26 and diode D13. At this point, the switching transistor TR7 is turned on and a voltage is applied to the switching transformer's next winding N1. Diodes D12 and D13 are diode-rD in FIG.
r and D8, respectively, and switch the switching transistor TR7 in a non-saturated manner. t+, diode-FD14 is diode D in Figure 5.
9, which corresponds to switching transistor TR7
When K turns off, it discharges its pace accumulated charge. Due to the function K of these diodes D12 to D14. The storage time of the switching transistor TR7 when turned off is shortened. On the other hand, when transistor TRl7 is turned on, P live transformer 5 is driven, and the voltage induced in its secondary winding INN10 is applied to switching transistor TR8 via resistor R27 and diode D16. The switching transistor TR8 is turned on by this K.
Switching transformer - Apply a voltage of opposite polarity to the next winding NIK and #. Diodes D15 and D16 correspond to the diodes D12 and D13, respectively, and switch the switching transistor TR8 in a non-saturated manner. Further, the diode D17 corresponds to the diode DI4, and discharges the accumulated charge when the switching transistor TR8 is turned off. As a result, the switching transistor TR8 has a shortened metrage time when it is off. A time constant circuit consisting of a capacitor 015 and a resistor R28 is connected to the fourth terminal of the switching transistor TR7. As a result, a switching signal with rounded rising and falling waveforms is obtained from the P live transformer secondary winding N9. Further, a time constant circuit consisting of a capacitor 016 and a resistor R29 is connected to the pace of the switching transistor TR8. This is K, drive transformer secondary winding 11
A switching signal whose rising and falling waveforms are blunted is obtained from N10. As described above, in the embodiment shown in FIG. 9, the rising edge and falling edge of the switching signal waveform are blunted in the portion directly connected to the switching transistors TR7 and TR8, so that Drive transformer T4. There is no influence of circuit gain, etc. existing between T5 and switching transistors TR7 and TR8, and the effect can be directly confirmed when setting the capacitance of the inserted capacitor 015.016, making the setting easy. Note that the waveforms of various parts in the circuit of FIG. 9 are shown by solid lines in FIG. The dotted line in Figure 10 is the capacitor 015,0
This is a waveform when there is no 16. Although the above embodiments have mainly been described with respect to the modified half-bridge system, as is clear from the operating principle of the present invention, the circuit system is not limited to this; , Inokic method, and Howard method can be similarly applied. (6) On page 17, line 17, ``This is an operating waveform diagram.'' is corrected to the following sentence. "Operating waveform diagram, FIG. 9 is a circuit diagram showing still another embodiment of the present invention, and FIG. 10 is an operating waveform diagram of the circuit shown in FIG. 9." (6) Page 18, line 1 of the same page. From this, "4... switching transformer" in the second line is corrected to "4... error amplifier". (7) Figure 5 of the drawings will be corrected in the attached sheet. (8) Figures 9 and 10 shown in the attached sheet will be added to the drawings.

Claims (1)

[Claims] A switching power supply circuit in which a switching transistor connected between a switching transformer and its power supply is driven by a small ('N) signal containing a high 1III wave component.