JPH0521990Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a DC stabilized power supply device using a switching regulator. The invention relates to a soft start/stop circuit provided for the purpose of preventing an overshoot in the rising waveform of an output DC voltage.

(Prior Art) FIG. 6 is a block diagram showing an example of a DC stabilized power supply device equipped with a conventional start/stop circuit. In the figure, 1 is a rectifying and smoothing circuit that rectifies and smoothes AC input voltage to obtain DC voltage ei, and 2
is a transformer having a primary winding n ₁ and a secondary winding n ₂ , 3
4 is a switch element that turns on and off the DC voltage ei and applies it to the primary winding n ₁ of the transformer 2, and 4 rectifies and smoothes the AC voltage obtained at the secondary winding n ₂ of the transformer 2 to output the DC voltage eo. 5 is a deviation amplifier that compares the voltage corresponding to the output DC voltage eo with the reference voltage Vref and amplifies the deviation between both signals.
Reference numeral 6 denotes a control circuit that includes a deviation amplifier 5 and controls turning on and off of the switch element 3 according to this deviation signal, and uses, for example, a TL494 type IC.
Here, VIN is the terminal to which input voltage ei is applied,
Tref is a terminal to which the reference voltage Vref is output, and TD is a dead time control terminal. Terminal Tref
A capacitor CS is connected between and terminal TD, and a resistor RS is connected between terminal DB and common, and when the power is turned on, switch element 3
A soft start circuit is configured to control the on-time so that the on-time gradually increases from the minimum on-time.

(Problems to be solved by the invention) In the conventional device having such a configuration, the control circuit 6 monitors the magnitude of the input DC voltage ei,
When the input DC voltage ei reaches a certain value _ei1 , the operation starts, and when the input voltage ei drops to a certain value _ei2 , the operation stops.

Here, the aforementioned start/stop voltage ei ₁ ,
ei ₂ depends on the internal hysteresis of the IC that constitutes the control circuit 6, and therefore, the start/stop voltages ei ₁ and ei ₂ vary depending on the variations in the IC itself.
There was a problem that changed.

The present invention was developed in view of these problems, and its purpose is to easily set the start/stop voltages ei ₁ and ei ₂ of the power supply, and to eliminate the effects of variations in the ICs that make up the control circuit. The aim is to realize a DC stabilized power supply device that is free of

(Means for solving the problems) FIG. 1 is a basic configuration block diagram of the present invention. In the figure, 2 is a transformer having a primary winding n ₁ and a secondary winding n ₂ , 3 is an input DC voltage ei turned on,
Switch element that turns off and supplies to primary winding n ₁ , 4 is 2
A rectifying and smoothing circuit that rectifies and smoothes the output of the next winding n ₂ , 6
is a control circuit that inputs a voltage related to the output voltage eo of the rectifying and smoothing circuit 4 and controls the on/off of the switch element 3 so that the output voltage eo becomes a constant voltage corresponding to the reference voltage Vref, and performs dead time control. It has a function. 7 is a comparator which receives the reference voltage Vref and the input DC voltage ei and has a hysteresis characteristic created by the voltage eo ₁ related to the stabilized output DC voltage eo; is applied to the time control terminal TD.

(Function) The comparator 7 creates a hysteresis characteristic by inputting the stabilized output DC voltage _eo1 , and controls the dead time of the control circuit according to the magnitude of the input DC voltage ei and the reference voltage Vref. Controls the potential of terminal TD. This controls the width of the drive pulse applied from the control circuit to the switch element.
The start/stop voltage of the power supply device can be set arbitrarily by a comparator 7 having hysteresis characteristics.

(Embodiment) FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals.

The comparator 7 with hysteresis characteristics has its collector connected to the dead time control terminal TD, and its emitter connected to the terminal to which the reference voltage Vref is output.
It consists of a transistor _Q1 connected to Tref, and an input DC voltage ei and a stabilized output DC voltage eo are applied to the base via resistors R1 and R2, respectively. R3 is a resistor commonly connected to the base of transistor Q.

CS is between terminal Tref and terminal TD (transistor Q
RS is a resistor connected between terminal TD and common, and RS is a resistor connected between terminal TD and common.
These constitute a soft start circuit.

The operation of the apparatus constructed in this way will be described next with reference to the operational waveform diagram in FIG.

First, when the device is powered on, the input DC voltage ei is small as shown in Figure 3A, and the value ei is the base potential of the transistor _Q1 (potential at point a) Vref-
VBE (where VBE is the base of transistor _Q1
When the emitter voltage is smaller than (ei<Vref−
VBE), the transistor _Q1 is in the on state as shown in (b), and the collector potential of the transistor _Q1 , and therefore the potential VDT of the dead time control terminal TD of the control circuit 6, is in the on state as shown in (c). It becomes equal to the reference voltage Vref. Therefore, in this state, the control circuit 6 does not output a drive signal having a pulse width that turns on the switch element 3.

When the input DC voltage ei gradually increases and the base potential of the transistor Q ₁ becomes higher than Vref − VBE (ei > Vref − VBE), the transistor Q ₁ turns off as shown in b, and the capacitor CS reaches the reference voltage Vref. It is then charged. As a result, the reference voltage is applied to the dead time control terminal TD.
CS, RS from Vref to common line voltage VC
A voltage that changes with a time constant of is applied. The control circuit 6 receives this voltage and outputs a drive signal whose pulse width gradually increases as shown in d to the switch element 3, thereby soft-starting the operation of the power supply device.

When the switch element 3 is turned on and off by the drive signal and the operation of the power supply device starts, the output DC voltage eo rises as shown in E, and is eventually maintained at a constant value corresponding to the reference voltage Vref. This regulated output DC voltage eo is the transistor
It is applied to the base of _Q1 via resistor R2 and added to the reference voltage Vref. As a result, the base potential of the transistor Q ₁ becomes slightly different from that immediately before the operation starts, and the comparator made up of the transistor Q ₁ can have hysteresis characteristics. This hysteresis characteristic can be set to a desired characteristic by changing the resistance values of the resistors R1 to R3.

Next, when the power is turned off from such a state, the input DC voltage ei decreases as shown in A.
Vref−VBE+Vo becomes smaller than ₁ (ei<Vref−
VBE+Vo ₁ ), transistor Q ₁ is turned on as shown in (b). As a result, the capacitor CS is short-circuited, the reference voltage Vref is applied to the dead time control terminal TD, and the control circuit 6 turns off the switch element 3 to stop the operation of the power supply device.

In a power supply device that operates in this manner, the start/stop voltage for operation can be easily set by a comparator with hysteresis characteristics provided outside the control circuit 6.

FIGS. 4 and 5 are block diagrams showing other embodiments of the device of the present invention.

In the embodiment of FIG. 4, as the stabilized output DC voltage _{eo 1} in the embodiment of FIG. It was developed and used.

The embodiment of FIG. 5 uses a diode to convert the reset voltage generated in the primary winding n ₁ of the transformer 2 as the stabilized output DC voltage eo ₁ in the embodiment of FIG.
In addition to rectifying and smoothing with Do and capacitor Co,
It is clamped and stabilized using a Zener diode Dz.

According to the embodiments shown in FIGS. 4 and 5, it is possible to insulate the primary side and the secondary side of the transformer 2, compared to the embodiment shown in FIG. Also, even if the load to which the output DC voltage eo is supplied is short-circuited,
This has the advantage that the hysteresis characteristics of the comparator are not affected.

(Effects of the invention) As explained in detail above, according to the invention, the start/stop voltage of the power supply device can be easily set by a comparator provided outside the control circuit, and the control circuit is configured It is possible to realize a DC stabilized power supply device that is not affected by variations in the IC used.

In addition, if the stabilized DC voltage applied to the comparator to provide hysteresis characteristics is the stabilized output of the auxiliary winding or primary winding of the transformer, the primary This has the effect that it is easy to insulate the secondary side from the secondary side, and it is not affected by load short circuits.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration block diagram of the present invention, FIG. 2 is a configuration block diagram showing an embodiment of the present invention,
Figure 3 is an operation waveform diagram showing an example of the operation.
5 and 5 are block diagrams showing other embodiments of the device of the present invention, and FIG. 6 is a block diagram showing an example of the conventional device. 2...Transformer, 3...Switch element, 4...
Rectifier and smoothing circuit, 6... control circuit, 7... comparator.

Claims (1)

[Claims for Utility Model Registration] (1) A transformer having a primary winding and a secondary winding;
a switch element applied to the secondary winding; a rectifying and smoothing circuit that rectifies and smoothes the output of the secondary winding of the transformer;
Input the voltage related to the output DC voltage eo of this rectifier and smoothing circuit, and use the output DC voltage eo as the reference voltage.
In a DC stabilized power supply device comprising a control circuit having a dead time control function that controls ON/OFF of the switch element so as to maintain a constant voltage corresponding to Vref, the reference voltage Vref and the input DC voltage ei are a comparator configured to create a hysteresis characteristic by a voltage related to the output DC voltage eo, and apply the output voltage of the comparator to the dead time control terminal of the control circuit. A DC stabilized power supply device characterized by: (2) Utility model registration claim No. 1 in which the voltage related to the output DC voltage eo is used by rectifying and smoothing the output of an auxiliary winding installed in a transformer.
The DC stabilized power supply device described in Section 1. (3) The DC stabilized power supply device according to claim 1 of the utility model registration, which uses a voltage related to the output DC voltage eo by rectifying and smoothing the reset output generated in the primary winding of a transformer.