JPS58204766A - Fixed frequency reset control type dc/dc converter - Google Patents

Abstract

PURPOSE:To stabilize the operation of a DC/DC converter by performing the reset in two stages when dissipating energy of a transformer during OFF period of a switching element, and controlling the ON duty ration of the switching element. CONSTITUTION:When a switching element 2 is switched ON or OFF with a signal from an oscillator 3 and electric power is obtained through a transformer 6, the OFF of the element 2 is detected by a coil n6 to conduct a transistor 12, the transformer 6 is reset by reset voltage control coils n4, n5, the transistor 12 is then interrupted by a signal from a control circuit 13 depending upon the output voltage, reset by the higher reset voltage, the end of the reset is detected by the coil n3, and the element 2 is conducted. Accordingly, the reset is performed in two stages, the reset period of the former is controlled, thereby stably operating even if the ON duty ratio is not raised more than 1/2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for controlling the output voltage in a safe manner.
This invention relates to a Dc-vc converter using an E-cycle factor set control method.

Generally, in this converter, only one direction of excitation current flows through the primary winding m of the main transformer constituting the converter. Because of this, the main transformer F
i I am always cultivating sweetfish in a state of single excitation. If the energy stored in the main transformer due to this excitation current is not released to the outside while the transistor is off, the maximum value of the magnetic flux change ΔB in the transformer core will gradually increase, causing magnetic saturation and causing excessive force in the primary winding. Since 11iMj flows, the transistor is destroyed. Therefore, a reset circuit is added,
Is there a need to release this stored energy? This stored energy is released by the product of the voltage and time applied to the transformer up to that point, so in order to reset it, it is necessary to apply the same voltage/time product with opposite polarity.

The present inventor is concerned with the above-mentioned 1) such a reset [g circuit in a C-DC converter.

An example of a conventional fixed frequency reset control DC-DC converter is shown in FIG. 1, and its operating waveforms are shown in FIG. 2.

In Figure 1, 1 is a DC power supply, 2 is a switching element, 3 is a fixed frequency amplifier, 4 is a drive circuit, 5 is a reset detection circuit, 6 is a transformer, 7 and 8 are diodes, and 9V is used for smoothing. A choke coil, 10 a smoothing capacitor, 11 a diode, 12 a transistor, 13 a control circuit that detects the output voltage and controls the transistor 12, 14 a capacitor, II+ the primary winding of the transformer 6, f12 Secondary winding, 113 beam cent detection winding, n4
is the reset voltage control stand.

In FIG. 2, a is the output waveform of the oscillator 3 in FIG. 1, and b is the voltage waveform at the winding nl of the transformer 6.

In the circuit of FIG. 1, the switching cable 2 is turned on by the drive circuit 4 at time to, and the primary winding of the transformer m
Power is supplied to the output side through the second best #n2.

At time tl, two switching elements are turned on from the signal IIC from the oscillator 3 via the drive circuit 4. Then, depending on the output voltage, the control circuit 13 or the transistor 1
Base l flowing into the base of 2! fi is increased or decreased, and depending on the vehicle pressure between the collector and emitter of the transistor 12, which is determined by this, the magnetic flux of the transformer 6 is increased or decreased.
At time t2, when the reset is completed, the reset detection circuit 5 detects the end of the reset from the voltage of the winding n3, and thereby turns on the switching element 2 again via the drive circuit 4. , repeat the above operations.

This circuit controls the mendutity ratio of the switching cable 2 by changing the collector-emitter voltage of the transistor 12, that is, the reset voltage of the winding number n4, to %++@+.

By the way, if the first on period of the previous self-switching element 2 is TON(i) and the first off period is Tp(i), then from the control method of the previous ad, ■ON' TON(i)-vRHTR( i)
..."--(1) However, plate-1, 2,...
・i'-TR(i) +ToN(i+1)
... Quadruple... (2) holds true.

Here, VoN+j is the absolute value of the voltage that stops at the winding (11) during the on-period [i5, VRtj, and off-period, respectively.

Now, because the stain pressure has changed due to some reason caused by disturbance, a displacement occurs in the n-th on period in an attempt to maintain the output voltage constant, and '17oN(n) = '1'ON+Δt 01J(n)
Then, Vow(Tom−'lto N(n) )”Vn(Tf
(+Δt R(n)) ---(3) Above (1)
* From formula (3), VOR'Δt on(n) = VR・ΔtR(n)・
・・・・・・・・・・・・(4) From the above equation (2), ΔtB(.juice ΔjON(n-1-1) -0...
(5) According to equations (4) and (5) above, this is the on-width TON+Δton after the occurrence of minute displacement, as is clear from the fact that the crest of equation (6) has one sign. (i
) (i≧n) oscillates.

(1) Δ10H(n+1) > l−Δtom(n)
When l =・・・・・・・・・(7), the vibration diverges,
The ON width cannot be determined by a single value. This is the time.

(11)Δtou(n+1)<l−ΔjON(n
) l When (9) occurs, the vibration converges, the ON width is determined to one value, and it becomes stable. This is the time.

(1), (2) t ('1゛ from equation 1 in 1)
・・・・・・・・・・・・It is stable when 0υTON > 2.

This means that in order to operate stably with this conventional control method, the on-duty ratio of the switching element 20 must always be kept at 1/2 or more. There was a drawback that the width was not determined by a single value, resulting in unstable operation.

On the other hand, if the on-duty ratio is made higher than Kl/2, the reset voltage of the transformer (necessary reset voltage) will also increase, which will be disadvantageous in terms of withstand voltage of the switching element 2 which receives this reset voltage via the primary winding mntt, and the output There were drawbacks such as a narrow controllable range of voltage.

The present invention has been made in order to eliminate the drawbacks of the prior art as described above, and an object of the present invention is to reduce the on-duty ratio of the switching element by lowering the reset voltage. An object of the present invention is to provide a fixed frequency reset control type DC-I)C converter which is advantageous in terms of withstand voltage and widens the controllable node H of the output voltage.

The main point of the configuration of the present invention is to identify the reset voltage in two stages in the DC-DCC converter, and to control the on-duty ratio of the switching element by controlling the reset period during which one of the reset voltages is adopted. The point is that stable operation is achieved even when the Eudy ratio is set to 1/2 or less. The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a circuit diagram showing one embodiment of the present invention, and FIG.

In Figure 43, 1 DC power supply, 2 a switching element, 3 a fixed frequency oscillator, 4 a drive circuit, 5 a reset detection circuit, 6 a transformer, 7 and 8 each a diode, 9 a smoothing choke coil, and lO is a smoothing capacitor, 12 is a transistor, 13 is a control circuit that detects the output voltage and controls the transistor 12, 15 and 16 are diodes, respectively, 17 is a constant voltage diode, fl1 is the transformer 60 primary winding, and n2 is the secondary winding, n3 is a reset detection winding, n4 and n5 are reset voltage control windings,
n6 is a winding for detecting timing when the switching element is turned off.

In FIG. 4, a is the output waveform of the oscillator 3, and b is the voltage waveform of the transformer winding &1n1.

To operate this, first the switching element 2 is activated at time t.
is turned on by the drive circuit 4 at O, and the winding Ii! of the transformer 6 is turned on by the drive circuit 4. Power is supplied to the output side through inl and n2.

At time 11, the drive circuit 4 is activated by a signal from the oscillator 3.
The switching element 2 is turned off via the . At this time, when the switching element off timing detection winding/1en6 detects the off state, the control circuit 13 is operated, thereby turning on the transistor 12.

Then, the diode 15 operates, and the transformer 60 winding (
n4+ns) is clamped by the voltage of the voltage diode 17 (assumed to be VZR), and the transformer 6 is reset. Next, at time t1 determined by the fj signal from the control 1gl path 13 which depends on the output voltage, the transistor 12
When turned off, diode 15 becomes inactive 9,
Due to the operation of the diode 16, the sitrans 6 is reset by the winding mns and the voltage VZH of the constant voltage diode 17.

At time t2, when the reset is completed to a predetermined magnetic flux energy value, the reset detection circuit 5 detects the end of the reset via the winding n3, sends a drive signal to the switching element 2 via the drive circuit 4, and turns on the switching element 2. shall be. Thereafter, the operation from time 1o is repeated.

In the circuit of the present invention, there are two levels of reset voltage ■R2■r
are kept constant, and the output voltage is stabilized by controlling the reset voltage vr stop period of one stage.The response when a fluctuation occurs in ON@ToN in the above circuit is calculated below. .

Then, from the condition that the voltage time product is constant and the control force method described above, the following equation is established.

VoN゛ToN(i)=Tr(i)0Vr+Ta(i)
4'n °---- θ dominant period 1゛ is T-Tr
(i)+Ta(i)+TotJ(i+1)−αQ
Also, Tc = Tr(i) (assumed constant) ・
. . . OQ This 'ro is a control period given by the control circuit 13. Now, if for some reason a displacement occurs in the n-th ON period and becomes TON(11) -TON+Δl0N(++), then VON('1"ON+ΔLON(n))
-T'r ・V, r +VR (TR+Δ1R(n))
・・・・・・・・・・・・αD Above u57. From the α equation, ΔIR(n) + ΔtON(n+1)=0 ・
・・・・・・・・・・・・ 081F α荀、αr+l
From equation (l)0, this is the same as equation (6) above.
4. n) indicates that it vibrates -CJ,; there is the following 2-knee state.

(1) Δ1oN(n+1) > l−Δton(n)
l -...-121 toto 111! M diverges, and the on-width is not determined by one value (・0 (11)Δ'0N(n+1)<l−Δtori(n)l
----(21), the amplitude of 11ft+ti converges, the on-width is determined by one value and is stable, which is 0, and the range of the on-width that operates stably is 04) above.

This means that the stable operation range has been expanded compared to (le, see the αυ formula, which operated stably only in formulas (C) and (C)). Because of this effect, the present invention can stably operate a fixed frequency reset control type DC-DC converter.

9. Another embodiment: In the circuit shown in FIG.
++++m++++++H may be used, and in this case as well, substantially the same effects as in the first embodiment can be obtained as described below. Above Q! 19, c74), Δtl((nu) = Δ′0N(n)−Δ10ti(
n+1) −(21i)VON('L”ON+ΔtO
N(t+)) = (Tr-Δton(n)) ・Vr
-I-(TR+JtR(n+1>)・Vu...
...@hiij(14) HtMi) Htr+1 formula, l:
li) When 2VH, l1loXJ+ΔtoN(i) (i
:ff1n), the vibration diverges and the ON width is not determined by a single value.

(Vo1++Vr) When < 2VR, TON+Δt
When ou(i) (1≧n), the vibration converges to 1, and the ON width is determined to be one value and is stable.

Vr)'s peak i"0N(o) [JtON(i) ('≧
In case of n), the symptoms of nausea decreased and became stable.

As shown above, when the control period To is set like the L,8+J (1) formula, the VBo value is slightly lower than when it is set like the -F zero period formula. However, it has the same effect as the first embodiment.

System diagrams 5 and 6 are circuit diagrams showing other embodiments having almost the same effects and features as the above embodiment, and the primary side of the transformer 6 is the same as that in FIG. 3, so it is not shown. is omitted.

In both the embodiments shown in FIGS. 5 and 6, the reset voltage of the winding n7 is set in two stages by a switch 21 whose on/off timing is controlled by a control circuit 13.

In the embodiment shown in FIG. 7, in addition to the effects of the embodiments described below, the power efficiency is improved by recovering the reset power to the output, and when the switch 21 is on, the winding 11
By making the reset voltage of M (n4+n5) the same as the output voltage of the converter, and making the reset voltage of 5 the same as the output voltage of the converter when the switch 21 is off, a reset voltage of the 2R level is obtained.

The embodiment shown in FIG. When switch 21 is off, volume & ny reset)
[By making the voltage the same as the output voltage of the converter, a two-step reset voltage is obtained1.Furthermore, it can be easily implemented as a configuration in which the reset power is recovered to the input side, and the same effect as in the case of recovering the reset power to the output side. is looked down upon.

As explained above, according to the present invention, the identified frequency reset control system D C-I) C converter operates stably even when its on-duty ratio is 1/2 or less, so the output voltage control range can be widened, and There is an advantage that the breakdown voltage of the switching element can be lowered by lowering the reset voltage.

[Brief explanation of the drawing]

Figure 1 shows the conventional fixed frequency set control method 1)
CD C:r7/(-Circuit diagram without an example of evening, 2nd
3 is a circuit diagram showing one embodiment of the present invention, FIG. 4 is a waveform diagram showing its operating waveforms, and FIGS. FIG. 3 is a circuit diagram showing an example. Description of symbols 1...DC iI source, 2...Switching element, 3...Fixed frequency oscillator, 4...
...Drive circuit, 5...Reset detection circuit, 6.
...Transformer, 7,8...Relied diode, 9...Smoothing choke coil, 10...
...Smoothing capacitor, 11...Diode,
12...Transistor, 13...Control circuit, 14...Connector/su, 15.16...
...Diode, 17... Constant voltage diode, 18... Diode, 19°20...
- Constant voltage diode, 21...Switch controlled by control circuit, 22.23...Diode, a...Okiya frequency R1I big oscillator output, b...
...Trans volume 4+! n1I7J Voltage Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki

Claims (1)

[Claims] 1) A series circuit of a switching element and a DC power supply is connected to the primary winding of a transformer having a primary winding and a secondary winding, and a reset circuit for releasing excitation energy of the transformer; A reset detection circuit for detecting that the transformer is set and a fixed frequency oscillator are provided, and when the reset detection circuit detects that the transformer is set, the switching element is turned on, and then the fixed frequency oscillator (IIv) to output an output from the secondary winding by turning off, and during the off period of the switching element, the excitation energy of the citrans is released to the reset circuit to perform a reset. Reset gain” Goriki ceremony 1
) Ono II * Dedeyu, who checks whether the switching element has turned off in the C-DC converter;
- One phase +M from the seven-kilometre reset circuit activated by oats detection decision (hereinafter referred to as the 1st reset period)
-1 reset voltage is applied to the 1st transformer to reset it, and then the reset voltage applied to the transformer from the reset 1st part is applied to the transformer. I cut through and reset the rest - t = role, t - crotch is deleted; resettle of culvert 1! Similarly, by controlling the Tllil width, ll11
jaLS switching element on/in tuJ ratio Yt
+t+lI Mu is similar to 4Ii European reset system method 1) C-1) C converter