JPH0318272A - Switching regulator circuit - Google Patents

Abstract

PURPOSE:To stabilize output voltage without causing power loss by detecting the current value of the output voltage when it is reduced to the predetermined value and below and at this moment by heightening the interrupted frequency of the primary current. CONSTITUTION:When the value of output current is reduced to less than the predetermined value, the current value induced to the secondary coil 15b of a current transformer 15 in a current detection section 11 is reduced, corresponding to which the voltage at a capacitor 18 is reduced to turn OFF a transistor 20. A transistor 21 pulled up by a resistance 22 is thereby turned ON, so that the resonance frequency of a resonance circuit composed of these resistances 23 and 24 and a capacitor 25 is doubled. The rise and variations of output voltage V0 can therefore be prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to switching regulator circuits.

(Prior Art) As one of the switching regulator circuits that generate a stabilized power supply voltage, a circuit shown in the fifth column is conventionally known.

The switching regulator circuit shown in this figure includes a power transformer L01, a DC voltage source 102 connected to the next call I01a of this power transformer lot, and a DC voltage source 102 that connects the current of this DC power IF source +02 intermittently to the power transformer. A transistor lO3 that supplies an intermittent current to the secondary coil lOla of +01, a die 104105 that rectifies the alternating current L1 induced in the negative secondary coil I0lb of the power transformer l01, and A choke coil +06 smoothes the pulsating voltage obtained by the pulsating current voltage, and a capacitor 107 that works in cooperation with this choke coil IO ('3) to smooth out the pulsating current voltage. There is.

In this configuration, if the transistor 103 is turned on and off repeatedly at a predetermined period as shown in the sixth factor, the secondary coil 10lb of the power transformer +01 will be
An induced voltage Vs is generated.

? 1 - The electric liver of the DC power source +02 is connected to the load (not shown) (connected to the output terminal +08) via the choke coil lQ6 in Figure 7 as shown in the following equation. 1■. An induced current 1gtl with 11:+ flows,,? ! 1, V(1:
: ] 'V=')'j l 0 7 terminal r 1 electric current I to 1, : Inductance of choke coil +06 1' o + i: On time of transistor 103 T o■
: OFF time of the transistor 103 And, at this time, the output voltage V of the output terminal +08 (+ is expressed by the following formula.

However, Ns:':. Number of turns of the next coil 10lb N. ．． :
Number of turns of secondary coil l 0 1 a As is clear from equation (4), in this switching regulator, the human power voltage ■? Even if the on-time of the transistor 103 changes, the on time of the transistor 103 ゛■゛. , the output voltage 1' {: v o
Since it is possible to adjust the output voltage V. The transistor 103 detects and keeps it constant.
If you control the ON time of
In addition, it is possible to provide a stabilized power source with low loss and extremely high efficiency in controlling the current and electric power I-E.

However, in such a switching regulator, the output from the output terminal 108 is f]ij:f
'l'u current (output 'l'li current io) flowing to
is the output? When the RfrL peak value 1■ becomes less than 10 minutes (below the critical current), the current flowing through the 1-coil 106 becomes discontinuous in the part below the average output current of the current, and the output during this period There is a drawback that the electric current fE Vo has an upper limit, resulting in an increase in the average output voltage.

Conventionally, means for controlling the ON time using a switching transistor has been used to stabilize the output 711 FI-: However, when the load current is extremely small, it may not be possible to compensate for one series of voltage +911. was there.

? In order to eliminate this inconvenience, a dummy resistor +09 is connected in series to the capacitor 107 as shown in FIG.
Although it is also possible to insert a dummy current I as shown in FIG. is constantly flowing, so the power loss F) at the resistance + 0 9 is expressed by the following formula:
S occurs.

PR = r o'- +< ・
(5) I11, R: Resistance value of dummy resistor 109,
Another method is to increase the impedance of the choke coil 106 so that the induced current 1, +
Slope of j* 1■1. , +, lt is made small.

However, since such a method requires a large choke coil 106, the choke coil +06
There was a problem in that the size of the circuit became too large, making it impossible to downsize the entire circuit.

(Eleventh aspect of the invention) The present invention provides 1-. This was done in consideration of the circumstances mentioned above, and to prevent the road from becoming popular. However, it is an object of the present invention to provide a switching regulator circuit that can stabilize the output current without causing power loss even when the output current becomes small.

(Summary of the invention) - In order to achieve objective 1.1 of item L, the switching regulator M path according to the present invention has the following configuration, that is, the current on the negative side of the power transformer is intermittent. l! '
I+iL! After inducing heavy pressure on the next side of the l'li source transformer and rectifying this extra pressure, or directly intermittent DC current and rectifying its output, slipping it with a choke coil. In a switching regulator circuit that generates an output voltage and controls intermittent timing so that the voltage is constant, the output voltage 1
a current detection section that detects when the current value of the output voltage becomes less than a predetermined value; The secondary current frequency control section increases the intermittent frequency of the side current.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a block diagram, without showing an embodiment, of a switching regulator circuit according to the present invention. , the switching regulator circuit shown in this figure consists of a power transformer l, a DC voltage source 2 connected to the primary coil la of the power transformer 1, and a DC voltage source 2 connected to the primary coil la, and chopping the current of the DC voltage source 2. MoejL! A transistor 3 that supplies a disconnection current to the primary coil la of the power transformer 1, a diode 4 that rectifies the alternating current voltage induced in the secondary coil Ib of the power transformer 1, and a A choke coil 6 is provided for smoothing the pulsating current voltage.

Further, this switching regulator circuit includes a capacitor 7 which operates in coordination with the choke coil 6 to further smooth the pulsating voltage, a die capacitor 5 which serves as a back electromotive current route of the choke coil 6, and an output voltage F1-. ．． an output voltage detection unit 1O that detects the value of the output current and generates a voltage control signal; a current detection unit 1L that detects when the value of the output current becomes less than a predetermined value and generates a frequency switching signal; A pulse signal control unit 1 that controls the transistor 3 by perturbing each output of the voltage detection unit 10 and the current detection unit l1.
2.

1j'l +! As shown in FIG. 2, the current detecting section 11 has a secondary coil 15a of a current detecting transformer 15 inserted in series with the secondary coil 1b of the power transformer 1, and a secondary coil 5b of the current transformer 15. A resistor 16 for current-to-voltage LL conversion connected in parallel with the resistor 16, a diode 17 that rectifies the voltage generated across the resistor 16, and a capacitor 18 that averages the voltage rectified by the diode 17. , a current value limiting resistor 19, a transistor 20 that turns off when the voltage supplied via this resistor 19 becomes less than a predetermined value, and this transistor 20.
The transistor 21 is provided with a transistor 21 whose power/power is controlled by the transistor 21, and a resistor 22 which applies a bias voltage IF to the base of the transistor 21.

Further, the pulse width control section 12 includes a series circuit of two resistors 23 and 24 added to the oscillation path (not shown), and a capacitor 25 that operates in parallel with these resistors 23 and 24 to form a resonant path. It is equipped with

Note that the oscillation circuit, which is not shown, is constructed of, for example, an Asahi stable multi-vibrator.

In this case, the resistors 23 and 24 are set to have the same value, for example.

Next, the operation of this embodiment will be explained with reference to the waveform diagrams shown in FIGS. 3 and 4.

The output power currently being output from the output terminal 8}F. V[]
When the directivity of deviates from the setting {1+I, the output 'lli 7
-E detection unit 10 detects this, generates a voltage control command necessary to restore the value of the output voltage V(l), and supplies it to pulse signal control unit l2.

As a result, the pulse {No. 7: The control section 12 generates an on-time of 1' during one period of the transistor 3 as shown in FIGS. 3(a) and 3(b). The ratio of 8 is controlled 10 to return the value of the output voltage Vo to the set value.

Note that by controlling this pulse width, the output voltage V
. The function of keeping the pulse width at a constant value is the same as that of a conventional one. Therefore, a detailed explanation of the output voltage detection section 10 and the pulse width control circuit will be omitted.

The feature of the present invention is the following operation. That is, when the value of the output current becomes smaller than a predetermined value, the value of the current induced in the primary coil 15b of the IJ flow transformer 15 of the current detection section I1 decreases, and the As a result, the voltage IF of the capacitor 18 becomes low and the transistor 9 is turned off, which turns on the transistor 21 which is pulled up by the resistor 22, and a pulse {4 is generated. Connection point 1 of resistor 24
) is grounded, and as a result, the resonant frequency of the resonant circuit constituted by these resistors 23 and 24 and the capacitor 25 is doubled, the switching frequency of the transistor 3 becomes 2 {r', and the switching frequency of the power transformer 1 is -Secondary coil
This is the point at which the frequency of the current induced at 1 changes from the state shown in FIG. 4(a) to the state shown in FIG. 4(b).

? As a result, the peak current of the output current is approximately ゛I
The critical current value can be halved in 4 minutes. f'
Even if the load current becomes extremely small, it is possible to prevent the output voltage V(1's field and fluctuations.In this way, in this embodiment, the output '1'u current in is kept at a predetermined level. i1i
When this happens, this is detected and the switching of transistor 3 is activated. Since the number of 1.1m can be increased by +Y':i, the output current can be reduced by 1 without using a dummy resistor.
When o's i〆1 becomes small, output 1'IJ. FLVo
It is possible to prevent upper bounds and fluctuations by 11 and 2.

This prevents the same path from becoming larger, and also prevents power loss from occurring even when the output current io becomes small. The case using a 1′■source transformer is shown, but
Switching regulator aspect! The ii type saves this power transformer and rectifies the intermittent 1α current to the ii'j connection. There is also a method of supplying it to the Itliil route.
What the present invention can do in this case as well 12. Neverlasting (Effects of the Invention) As explained below, according to the present invention, it is possible to prevent the circuit from becoming too large and to reduce the power consumption even when the output current is small. The output voltage can be held constant without causing loss.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the switching regulator circuit according to the present invention, Fig. 2 is a detailed circuit diagram of the current detection section shown in Fig. 1, and Figs. 3 (a) and (b). are waveform diagrams for explaining operation examples of the same embodiment, and FIG. 4(a)
, (b) are waveform diagrams for explaining operation examples of the same embodiment, FIG. 5 is a block diagram showing an example of a conventionally known switching regulator circuit, and FIG. 7 is a waveform diagram for explaining an example of the operation of the switching regulator circuit shown in FIG. 5, and FIG. 8 is a waveform diagram for explaining an example of the operation of the switching regulator circuit shown in FIG. 5. Waveform 1 3 ? for explaining an example of 1-1 path operation. , FIG. 9 is a block diagram showing another example of a conventionally known switching regulator circuit, FIG. 10 is a waveform diagram for explaining an example of the operation of the switching regulator circuit shown in FIG. 9, and FIG. 11 is a block diagram showing another example of a conventionally known switching regulator circuit. is a waveform diagram for explaining another example of a conventionally known switching regulator circuit. l...power transformer, 2...DC voltage source, 3...
Transistor, 6...chi...1-ku coil, l1...
Current detection section 12...Primary current frequency control section (pulse signal control section).

Claims (2)

[Claims] (1) A switching means for intermittent the supplied DC current, a means for rectifying and smoothing the intermittent current and outputting it, and a means for detecting the voltage of the output and controlling the switching means to keep the voltage constant. In the switching regulator circuit, the switching regulator circuit includes a current detection section that detects when the current value of the output voltage becomes equal to or less than a predetermined value, and a current detection section that detects when the current value of the output voltage becomes equal to or less than the predetermined value. and a primary current frequency control section that increases the intermittent frequency of the primary current when it is detected that the switching regulator circuit has changed. (2) Intermittent the primary side current of the power transformer to induce a voltage on the secondary side of the power transformer, rectify this voltage, and smooth it with a choke coil to generate an output voltage, and the output voltage is A switching regulator circuit that controls the intermittent timing to be constant, includes a current detection section that detects when the current value of the output voltage becomes equal to or less than a predetermined value, and a current detection section that detects when the current value of the output voltage becomes equal to or less than a predetermined value. A switching regulator circuit comprising: a primary current frequency control section that increases the intermittent frequency of the primary current when it is detected that the primary current becomes less than a predetermined value.