JPS62163570A - Dc converter - Google Patents

Abstract

PURPOSE:To prevent the magnetic saturation of a transformer by preventing its switching element from turning ON during the period when the feedback voltage is generating in response to this period. CONSTITUTION:A DC converter is composed of a transformer 3, a field effect transistor (hereinafter referred to as Tr) 5 as a switching element, an output rectification and smoothing circuit 11 made up of diodes 7-8 and a control circuit 14 to control the Tr 5 by turning ON/OFF and sends out the stabilized DC output voltage from output terminals 12-13. On this occasion, a transformer tertiary winding 24 to detect the flyback voltage and a Tr 25 for preventing turning-ON are provided and connected to the base of the Tr 5 through a diode 26. Thus the Tr 5 is prevented from turning-ON by the Tr 25 due to the flyback voltage. After the flyback voltage vanished (the resetting of the transformer 3 is finished), the Tr 5 is turned ON. As a result, the magnetic saturation of the transformer 3 is completely prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a device (DC-to-DC Humbater) that performs DC-DC conversion by controlling on/off switching elements connected in series to the primary winding of a transformer. This is related to K.

[Conventional technology]

Connect the top row circuit of the transformer primary winding and transistor to the DC electric mixer, connect the output rectifier flat steel circuit to the transformer secondary winding, and install a pulse width variable, % (PWM) circuit that responds to the output voltage. , this pulse lI @ modulation circuit output turns the transistor on and off! The II control method is well known.

[Problem that the invention seeks to solve]

If a transformer is connected to a DC circuit, will the transformer become magnetically saturated? Therefore, the residual magnetism of the transformer must be completely reset using a snubber circuit. If an ON control signal is sent to the switching transistor before resetting, magnetic saturation of the transformer will occur. Overcurrent flows through the switching transistor. Therefore, the off period is generally set to be long enough to send an on control signal to the switching transistor after the transformer is reset. With this configuration, the Although magnetic saturation of the transformer does not occur, the duty ratio becomes smaller and the power capacity decreases.

Therefore, an object of the present invention is to provide a DC converter that can eliminate the occurrence of magnetic saturation in the transformer and widen the on-pulse width.

[Means for resolving the gap]

The DC converter according to the present invention for solving the above problem At1 and achieving the above object has the primary winding of a transformer connected between -10,000 DC power supply terminals and the other DC 1!0 terminal. a series circuit of a wire and a switching element, a secondary winding of a transformer electromagnetically coupled to the primary winding, an output rectifying flat steel circuit connected to the secondary winding, and the switching element. Direct current consisting of a control circuit that turns on and off the
In the DC converter, flyback voltage detection (which detects a flyback voltage generated by the transformer during the off period of the switching element or a voltage corresponding to this)
b) an on-state detection circuit that responds to a signal indicating a flyback voltage generation period obtained from the flyback voltage detection circuit and prevents the switching element from being turned on during this generation period; The present invention relates to a DC converter characterized by the following.

[For production]

In the above invention, the switching element is turned on by control based on the flyback voltage or a voltage corresponding thereto after the flyback voltage disappears, that is, after the reset of the transformer is completed. As a result, the magnetic saturation of the transformer is fully exposed.

Also, the width of the On III monument signal has been expanded! Since the switching element does not turn on before the transformer is reset, the width of the ON III control signal can be widened, and the power capacity can be increased.

〔Example〕

Next, a DC converter according to an embodiment of the present invention shown in the first factor will be explained. +11f2+ in FIG. 1 are one and the other DC power supply terminals. This pair of power terminals +11+
A series circuit of the primary winding #(4) of the transformer (3) and a field effect transistor (5) as a switching element is connected between the transformer (31) and the secondary winding of the transformer (31).
61 has a diode (71181) and a reactor (9"
, and an output rectifying flat steel circuit consisting of a capacitor CI (I +
Ill is connected. Therefore, transistor (5)
By controlling on/off, a stabilized DC output voltage can be obtained between the output terminals 07131 based on the DC power supply voltage E8 between the power supply terminals 111121.

■ is a voltage control circuit, and one input terminal is connected to the voltage dividing point of the voltage detecting voltage dividing resistor a51ttb+ connected between the output terminals (121 (131), the basic voltage expansion αT, and the voltage dividing resistor u51ubl). A differential amplifier Q81 is connected, and the other input terminal is connected to the base at pressure source αη, and a triangular wave generation circuit a
A voltage comparator whose one input terminal is connected to the sickle and the triangular wave generating circuit a], the other input terminal of which is connected to the differential amplifier (I81), and a drive amplifier (which is connected to the comparator (4)).
21+, a transformer (221) and a resistor (p) provided between the drive amplifier αD and the gate of the transistor (5).

This control circuit (2) forms a pulse width modulated (1'WM) wave based on the comparison between the error output from the differential amplifier (a) and the triangular wave voltage obtained from the triangular wave generating circuit (191). on/off control.

The tertiary winding of the transformer is provided to detect the total flyback voltage according to the present invention.
) is an on-blocking transistor, the collector of which is connected to the gate of the transistor (51) and one end of the resistor via the diode (51), and the emitter of the transistor (51)
The pace is connected to one end of the tertiary winding (241) through the resistor suction 1.
The other end of Mc24J is connected to the emitter of transistor 4.

Diodes, resistors, and capacitors are snubbers.
The resistor is connected in parallel to the primary winding M (41) via a backflow closing diode, and the capacitor group as a voltage suppressing element is connected in parallel to the resistor.

(iIr7J) The operation of the circuit in Figure 1 will be explained with reference to the waveforms in Figure 2.As shown in Figure 2, the control circuit [141
from the on control gate voltage V. When applied to the gate of the transistor (5), the transistor +51 turns on and a drain current flows as shown in the second frame).

As a result, the power supply voltage is applied to the primary winding (4:
Corresponding voltages are obtained in the secondary winding (6) and the tertiary winding C241. The second (!\1 (81 is the primary winding (41
Although the voltage ■l of the secondary and tertiary windings (61
The voltage at C also has a value corresponding to j.

At time point 12, when the transistor (51) is controlled from on to off, a flyback voltage (return pulse voltage) is generated.
As shown in FIG. 2 fcl, the source voltage Ds becomes higher than the power supply voltage E8. The flyback voltage of the primary winding (41) is
It is added to the resistor Q9 through the diode (281t) and acts as a residual magnetic reset t8F on the primary winding M (41).

Note that the capacitor (1) suppresses the flyback voltage from increasing dramatically.At the 13th point, the residual magnetism of the transformer (3) disappears, and the transformer (3) is in a magnetically reset state. , the flyback voltage also disappears and the voltage of each winding (4) +61+24 of the transformer (31) becomes zero.Therefore, the drain-to-source voltage VD8 of the transistor +51 becomes the power supply voltage E8.t45#
If the ON control signal is generated again at this point, the same operation is repeated.

By the way, the on Ml Goharusu (P) shown in Figure 2 (1)
WMt&) changes depending on the output voltage. If the output voltage becomes low, the @ of the ON control pulse widens. In the method according to the present invention, the width of the on-control pulse is determined by the transformer (3
At the end of reset 1, t3, t is expanded to the corresponding ridge,
Even if the history is extended to t3', the transistor (5) will not turn on. To explain this completely, even if an on control signal is applied to the gate of transistor +51 at t3', the on-blocking transistor c !5; is turned on, the secondary winding of the drive transformer [221] and the gate and north of the transistor (5) are short-circuited by a circuit consisting of the diode Q6I and the transistor (5), and the transistor (5) is turned on. mth.The tertiary winding C!41 has s
Based on the flyback voltage during the reset period from t2 to t3, a voltage is generated to turn on the transistor I251, and the on control pulse turns on the diode (2), adding collector bias, and turning on the transistor Q5 in the period from 2 to 13. ) is turned on. After t, g, the voltage of the tertiary winding Q4 becomes zero, so the transistor G is turned off and the transistor (5) is turned on.

Therefore, it becomes possible to increase the on-period of the transistor (5), and the power capacity increases.

Also, when starting up or when voltage fluctuates, the capacitor
Because the charging voltage of During the period when flyback voltage is generated due to the movement, the transistor (5) is turned on, so the transformer (31) does not reach saturation.

(Another Embodiment) Next, the entire DC converter of another embodiment shown in the third case will be explained. However, parts common to those in FIG. 1 are given the same reference numerals and omitted for the sake of explanation. In this embodiment, a bipolar transistor (5a) is connected in place of the field effect transistor (51) shown in FIG.

In addition, the tertiary winding r2 for detecting flyback voltage noise
Instead of providing 41, a flyback electronic detection circuit c31) is connected to the secondary winding M +61.
In place of providing the on-ejection transistor f251 in the figure, a triangular wave delay control circuit 6Z is provided for completely delaying triangular wave generation.

In this circuit, a triangular wave voltage vs is generated from t1 to t3 in Fig. 4, and is compared with the component voltage vR obtained from the differential amplifier 08; (21) to the base VCm4 of transistor (5a)
When the base 'ML current shown in mCDI is supplied and the transistor (5a) is turned on and turned off at t3, t3
At ~t4, a flyback voltage is generated as shown in Figure 4B).
live. This voltage is detected by the voltage detection circuit @C1υ and supplied to the delay control circuit 6z. The delay control circuit 6z flybacks the point at which the ramp voltage of the triangular wave voltage vS starts to be generated.
There is a delay at the time t41 when E disappears. That is, the triangular wave valve is built in the raw circuit of (-) so that the charging start point of the capacitor coincides with the point at which the entire flyback voltage disappears.This control is performed by connecting the delay control circuit 3Z to the hold-off circuit of the oscilloscope and the sweep control circuit. This is achieved by forming substantially the same as a gate circuit.

As shown in the period t5 to t16, as the error output voltage vR becomes lower and the on period becomes longer, the flyback voltage generation period t6 to t7 changes. However, the next triangular wave voltage does not occur before the flyback voltage disappears. Therefore, saturation of transformer +31 is prevented.

(Modifications) The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

[al The IM field effect transistor +51 in FIG. 1 may be replaced with a bipolar transistor. Also, transistor +51 (5a) tl" ili of multiple transistors
It may be replaced with a circuit connected in columns and/or in parallel (・
.

It can also be applied when all varistors are connected instead of the fbl capacitor.

(cl Instead of the tertiary volume IVjlc! lump in Figure 1, the chamber pressure detection circuit c311'!l- in Figure 3 may be provided (1
゜(dl) It is also possible to detect the voltage corresponding to the flyback voltage based on the voltage across the transistor +51 (5aJ) or the voltage across the resistor ■.

〔Effect of the invention〕

As is clear from the above, according to the present invention, even if the on-time width of the switching element is widened, the transformer is not saturated, so that the total power capacity can be increased.

[Brief explanation of drawings]

Figure 1 is a circuit (2) showing a DC converter according to an embodiment of the present invention, Figure 2 is a waveform diagram of each part of Figure 1, and Figure 3 is a DC converter according to another embodiment of the present invention. FIG. 4 is a waveform diagram showing the state of each part in FIG. 3. +II (21...power terminal, (31...transformer,
(41...Primary winding, (5)...Transistor, (
6)...Secondary winding, Uυ...Output rectification flat wave circuit, ■
...control circuit, 241...tertiary winding,...transistor for preventing turning on. Agent Nori Takano Figure 1 Figure 2 @ Figure 3

Claims (3)

[Claims] (1) A series circuit of a switching element and a primary winding of a transformer connected between one DC power terminal and the other DC power terminal, and a secondary winding of the transformer electromagnetically coupled to the primary winding. A DC-DC converter comprising a winding, an output rectifying and smoothing output circuit connected to the secondary winding, and a control circuit for controlling on/off of the switching element, wherein the transformer is turned off during the OFF period of the switching element. a flyback voltage detection circuit that detects a flyback voltage generated at or a voltage corresponding to the flyback voltage; and a flyback voltage detection circuit that detects a flyback voltage generated in the flyback voltage detection circuit; 1. A DC converter comprising an on-blocking circuit that prevents turning on. (2) The flyback voltage detection circuit is a tertiary winding electromagnetically coupled to the primary winding, and the blocking circuit detects flyback voltage based on the flyback voltage obtained from the tertiary winding. 2. The DC converter according to claim 1, wherein the DC converter is a circuit that blocks supply of an ON control signal to the switching element during a back voltage generation period. (3) The flyback voltage detection circuit is a circuit that detects a flyback voltage generation period based on the voltage of the secondary winding, and the blocking circuit detects the rise of the ON control signal sent from the control circuit. 2. The DC converter according to claim 1, wherein the circuit converts the point in time after the flyback voltage disappears.