JPS62141970A - Switching regulator - Google Patents

Abstract

PURPOSE:To eliminate a hunting at both low and high temperature sides by connecting a hunting suppressing resistor in series with a phase advancing capacitor of an error amplifier. CONSTITUTION:An error amplifier I connected between output terminals (a) and (b) is constructed to allow a light emitting diode PD to emit a light in response to an error amount of a DC output voltage from a reference voltage when a DC output voltage alters due to a variation in a load connected between the terminals (a) and (b). A hunting suppressing resistor R2 is connected in series with a phase advancing capacitor C1 of the amplifier I to suppress an increase in a gain (cathode current) in a high frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switch breaker, and more particularly to a switching regulator that suppresses the occurrence of hunting.

[Prior Art] FIG. 3 shows a typical circuit example of a switching regulator.

In the figure, DC power supply ■. , n is a power supply (not shown) that rectifies the AC input into DC.

This DC power supply■. A high-frequency alternating current is generated on the primary side of the pulse transformer T by a circuit consisting of a pulse transformer T and a main switching element Q connected to 1n.

Then, this alternating current is passed through a rectifier circuit S, a middle-sized circuit, and a DC output V with a predetermined constant voltage and constant current is applied between the output terminals a and b.
Get 0.

By the way, the above-mentioned main switching element (l) performs a high-speed switching operation, so a MOS-FET is generally used.

An oscillation circuit X, a PWM circuit Y, and a pulse width amplification circuit 'PJz are connected in series to the control electrode of the main switching element Q mentioned above.

Furthermore, an error amplifier circuit I is connected between the rectifier circuit S and the smoothing circuit 14.

This error amplification circuit I operates based on a value set within the error amplification circuit I when the DC output voltage changes due to fluctuations in the load connected between output terminals a and b. For example, when the voltage is higher than the reference voltage, a light emitting diode provided in the error amplification circuit i forming a photo coupler is configured to emit light in accordance with the amount of error.

Then, the phototransistor of the photocoupler, which is paired with the light emitting diode provided in the PWM circuit Y, receives the light signal from the light emitting diode and becomes conductive, thereby generating a pulse signal whose pulse width is changed from the oscillation circuit X. is supplied to the main switching element Q, and the on-time of this main switching element Q is adjusted, ultimately resulting in a constant voltage, constant current DC output.

is obtained between output terminals a and b.

Next, an example of the circuit configuration of the differential amplifier circuit I is shown in FIG.

In FIG. 4, an error amplifying circuit 1 connected between output terminals a and b includes a light emitting diode PD constituting a photocoupler, a shunt regulator SR, and a resistor R2 connected in series. A phase advance capacitor C1 and a resistor R3 are connected in parallel with R0 and the light emitting diode PD.

A resistor R4 is connected between the resistor R1 and the light emitting diode PD, and between the connection point between the phase advance capacitor and the resistor R3, and the shunt regulator SR, and between this resistor R4 and the output terminal A variable resistor R1 is connected as shown.

In the above circuit configuration, for example, output terminal a
, b fluctuates and the DC output voltage increases, the light emitting diode t making up the photocoupler
” The light emitting type of PD increases, and the optical signal at this time is sent to the PWM circuit
By changing the radiation and h time constants of the differentiator circuit of WM circuit Y,
It is controlled by sending a pulse with a short on time to the 'I il' electrode of the main switching element (), and ultimately works to maintain a constant DC output.

[Problems to be Solved by the Invention] The conventional switching regulator having the error amplifying circuit 1 having the configuration described in 1. ,? There is a problem in that hunting occurs on the low or high temperature side of the ambient humidity and that the stable operating temperature range has to be narrowed.

In other words, an electrostatic field (rik h) is applied to the phase advancing capacitor C7.
If a thick capacitor is used, hunting will occur on the 1[(4 side).On the other hand, if a phase advancing capacitor C8 with a smaller electrostatic field is used, hunting will occur on the high temperature side. There is.

[L of investigation] This 5' explanation was made in order to solve the problems in section L.
It is an object of the present invention to provide a switching regulator that does not cause hunting in any case and can secure a wide stable operation range.

[Means for Solving the Problems] The switching regulator according to the present invention has a hunting suppression resistor R2 connected in series with the phase advance capacitor C1 of the error amplification circuit 'tPtf.

[Function] In the switching regulator of this invention, the hunting till 171 paper resistance R:! By setting f/; I+1, the increase in gain (cathode current) in the high frequency region can be effectively suppressed and hunting does not occur from the low temperature region to the high temperature region.

[Example] First, in order to investigate the cause of hunting,
As a result of conducting experiments with species/, l, we found the following.

■The cause of hunting in the low temperature region 1...k is thought to be due to no-in in the high frequency region by the phase advance capacitor C1, that is, an extreme increase in cathode current.

■The cause of hunting in the high temperature region is thought to be due to insufficient phase compensation (+ side) by the phase advance capacitor C8.

Therefore, it is thought that by eliminating the above two factors, the occurrence of hunting will be suppressed in both the low temperature region and the high temperature region.

Therefore, in the present invention, as shown in FIG. 1, a hunting suppression capacitor R2 is connected in series with the phase advance capacitor C1 of the error amplifying circuit I. ' Note that the other configurations in FIG. 1 are the same as the configuration of the error amplification circuit 1 provided in the conventional switching regulator shown in FIG. Explanation will be omitted.

Next, with reference to FIG. 2, the action of the hunting suppression resistor R5 described in item 1 will be described.

Figure 2 shows that the capacitance of phase advance capacitor C3 is 0.22.
IF, the resistance 11α of the resistor R1 connected in series with the excitation diode 1''I-' D is fixed to 3:□3Ω, and the resistance (1α of the hunting suppression resistor R7 is set to a = 0Ω, 1'
)=3. This is a club showing the frequency dependence of the leading phase angle and the peak cathode current when changed to 3Ω, c=6.8Ω, and d=15Ω, respectively.

Note that the AC voltage (■) is superimposed on the DC voltage between the output terminals.

) is set to 30 mV.

In addition, the solid line curves in Fig. 2 indicate the leading phase angle (0), and the dashed line curves indicate the peak force flow (m A ).
shows.

From FIG. 2 above, it can be seen that in the conventional error amplifier circuit I without the hunting suppression resistor R9, that is, when a=0Ω, the peak cathode current increases rapidly in the high frequency region.

For example, the value of the peak cathode current near the operating frequency, 360 KHz, is approximately 15 times greater than the value in the low frequency region.

On the other hand, the resistance values of the hunting suppression resistor R2 are b, c,
As d increases, the increase in peak cathode current in the high frequency region is suppressed.

Now, if we use a resistance of d=]5Ω as the hunting suppression resistor R0, the peak cathode current flow in the high frequency range is approximately 3% compared to the value of the peak current in the low frequency range. It is clear that it is possible to suppress this to a moderate level.

Further, the leading phase angle is 500 Hz to 2 K H:, c
/) In the vicinity of the same wave number, the above-mentioned hunting suppression resistance R.

Flf, bT: ill'! , or the high 191 wave area clearly depends on the resistance value of the hunting suppression resistor R2, and increases the resistance (1α) of the hunting suppression resistor R2 (J and the leading phase angle - Decrease
4-I understand.

In addition, in the above embodiment, "1 control for Huntink +
Resistance [<, 0 to 1.3 Ω and 15 Ω or more -L range ζ is not shown, and of course it is possible to select a value within or outside of this range.

[Effects of the Invention] As explained in L below, the switching regulator of the present invention has a cross-section configuration in which a hunting suppression resistor is connected in series to the phase advance capacitor of the error amplification circuit, so hunting in the low temperature region is suppressed. Suppress the extreme increase in gain in the high frequency range, that is, the cathode current, by using the phase advance capacitor, which is the cause of hunting, and compensate for the lack of phase compensation with the phase advance capacitor, which is the cause of hunting in the high temperature range. It has excellent effects such as being able to operate stably over a wide temperature range from low to high temperatures without causing hunting.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one error amplification circuit used in the switching regulator of the present invention, and Fig. 2 is a so-called difference amplification circuit '1! Figure B, i shows the peak cathode current when the resistance (1α) of the hunting suppression resistor connected to the phase advance capacitor No. 18 is changed to various diameters.
FIG. 4, which is a block circuit diagram showing the entire system, is a configuration diagram of a conventional error amplification circuit used in the switching regulator. In the figure, ■...error amplification circuit, PD...light emitting diode, SR...shunt regulator, R2...
・Hunting suppression resistor, C4... Phase advancing capacitor.

Claims (1)

[Claims] Direct current from a DC power source is supplied to a main switching element connected to the primary side of the pulse transformer, and the on/off operation of this main switching element generates alternating current on the primary side of the pulse transformer, and this alternating current is rectified. An oscillation circuit and a PWM circuit are connected to a conversion means for obtaining a DC output through the converter and a control electrode of the main switching element, and the conversion means compares the voltage of the DC output with a predetermined reference voltage;
An error amplification circuit amplifies and outputs the error with this reference voltage, and the output from this error amplification circuit is fed back to the PWM circuit, and the output pulse from this PWM circuit turns on and off the main switching element. A switching regulator having regulating means for controlling time and keeping the DC output constant, characterized in that a hunting suppression resistor is connected in series to a phase advance capacitor provided in the error amplification circuit. switching regulator.