JPS62233068A - Switching regulator unit - Google Patents

Abstract

PURPOSE:To increase a stability input voltage fluctuation by providing a second PWM comparator circuit by means of a capacitor voltage on a DC input side in addition to a first PWM comparator circuit and driving this unit by means of an AND output of these two circuits. CONSTITUTION:A switching regulator unit converts a double-end commercial AC voltage of input terminals 1, 1' into a DC voltage at an inputsmoothing circuit 3, turns ON and OFF said voltage at a switching circuit portion 4 in answer to an output of a PWM converter circuit 12 and supplies the voltage from output terminals 2 ' 2 ' via a transformer 5, a choke transformer 8 and a capacitor 9 to a load. In this case, there are provided a second PWM comparator circuit 14, a series circuit of resistance 15 and capacitor 16, and a switch circuit 17 (generating a serrated-wave voltage) operating simultaneously with the oscillation frequency of an oscillating circuit 13. In this way, a time ratio of pulse output is varied to make an output voltage constant as against a fluctuation in supply voltage applied to the input terminals 1, 1'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a switching regulator device for supplying DC stabilized voltage to industrial and consumer equipment.

2. Description of the Related Art Conventionally, this type of switching regulator device has a third
The configuration was as shown in the figure. A switching regulator device as a conventional technique will be explained with reference to FIG. Reference numerals 1 and 1' are input terminals to which a commercial AC voltage is applied. 3 is an input smoothing circuit which rectifies and smoothes the commercial AC voltage applied to the input terminals 1 and 1' into a DC voltage. 4 is a switching circuit section that turns on and off the DC voltage supplied by the input smoothing circuit 3 in accordance with the output of the PWM comparator circuit 12, and applies a pulse voltage to the primary winding 5 (a) of the transformer 5. . 5 is a transformer, - next volume a 5
The pulse voltage applied to (a) is induced in the secondary winding 5 (b), and the induced positive pulse voltage is applied to the diode 6.
It is rectified by a choke transformer 8, smoothed by a capacitor 9, converted to a DC voltage, and output to an output terminal 2,
2' is supplied to many loads.

On the other hand, when the negative pulse voltage induced in the secondary winding 5(b) turns off the diode 6, the energy stored in the choke transformer 8 is applied to the output via the diode T. , smoothed by capacitor 9 and supplied to output terminal 2.2'.

The output voltage of the output terminal 2.2' is compared and amplified with the reference voltage 11 by the comparator circuit 10, and the PWM comparator circuit 12
is output to. A sawtooth wave voltage that oscillates at a constant frequency is applied to the PWM comparator circuit 12 from an oscillation circuit 13, and the on-off pulse waveform determined by this sawtooth wave voltage and the output of the comparison circuit 10 is the PWM comparator circuit. 12 and applied to the switching circuit 4.

Furthermore, the operation of the PWM comparator circuit 12 will be explained in detail with reference also to FIG. Figure 4(a) shows PWM
B3 shows the sawtooth wave type press-fit of the oscillation circuit 13 applied to the comparator circuit 12 and the output voltage B of the comparison circuit 1o.
indicates the limit value of the maximum output voltage. Figure 4Φ)
is a pulse waveform C of the PWM comparator circuit 12, which rises and falls at each level cross point between the sawtooth voltage A and the output voltage B of the comparison circuit 10. When the output voltage of the output terminal 2.2' fluctuates, the output voltage B of the comparator circuit 10 becomes B1.
Or move to B2 and change the duty cycle of the on period and off period E of the pulse output C.

The pulse waveform C is applied to the switching circuit 4, and the duty ratio of the pulse voltage supplied to the primary winding i 5 (a) of the transformer 5 changes, and the duty ratio of the pulse voltage induced in the secondary winding 5 (b) changes. is changed, and the output voltage is varied in proportion to the duty ratio. Through this series of operations, the output terminal 2.2'
The output voltage of is kept constant from all fluctuations. Incidentally, the Zener diode 2o in FIG.
This determines the maximum duty ratio.

Problems to be Solved by the Invention In such a conventional configuration, the output voltage is stabilized due to fluctuations in the input voltage, that is, the commercial AC voltage or the DC voltage, by changing the output level of the comparator circuit 1o. The comparator circuit 10 is generally designed to have a low feedback loop gain in order to prevent abnormal oscillations, and the high frequency gain is particularly low.The response tends to be delayed due to phase correction, etc., so the output voltage can be adjusted with a sufficient response speed. cannot be stabilized, transient fluctuations in the output voltage are large, and a sufficiently large rejection ratio of the commercial frequency ripple voltage included in the DC voltage cannot be achieved. Similar response delays occur in load responses such as output voltage, but during these transient conditions, the duty ratio may expand to its maximum value (generally, the maximum duty ratio is limited to a constant value). In particular, it is necessary to have sufficient margin for the magnetic flux density so that the magnetic flux of the transformer 6 does not saturate even when the maximum duty ratio is reached, which is limited even when the input voltage is maximum. It also had the problem of being expensive.

The present invention is intended to solve these problems, and aims to provide a small and low-cost switching regulator device with improved stability due to input voltage fluctuations.

Means for Solving the Problems In order to solve the above problems, the present invention provides a switching circuit to which a DC input voltage is supplied, a transformer to which the output of the switching circuit is supplied to the primary winding, and a transformer for the transformer. A rectifying and smoothing circuit connected to the secondary winding, a comparator circuit that detects the output voltage of this rectifying and smoothing circuit, compares it with a reference voltage, and amplifies it, and compares the output voltage of this comparator circuit with the output voltage of the oscillation circuit. PWM that creates an on-off pulse waveform
A comparator circuit, and a switch circuit that operates the switching circuit with the output of the PWM comparator circuit and discharges the capacitor in synchronization with the oscillation cycle of the oscillation circuit in a series charging circuit of a resistor and a capacitor connected to the DC input voltage. and a second PWM comparator circuit that generates an on-off pulse waveform by comparing the charging/discharging voltage waveform of the capacitor with the output voltage of the comparison circuit, the pulse waveform of the PWM comparator and the second PWM
The pulse waveforms of the comparators are logically AND-connected to operate the switching circuit.

This configuration makes the response of the output voltage faster to fluctuations in the input voltage, and by changing the maximum duty ratio in inverse proportion to the input voltage, the level of the maximum magnetic flux density of the transformer in a transient response state can be reduced. It is possible to make it constant with respect to the input voltage.

Embodiment FIG. 1 is a block diagram of a switching regulator device according to an embodiment of the present invention. Components that operate in the same manner as in FIG. 14 in FIG. 1 is the second PWM comparator circuit, and the input is the comparison circuit 1o.
The other input is connected to the connection point of a series circuit of a resistor 16 and a capacitor 16 connected to both ends of the DC voltage of the input smoothing circuit 3, and the capacitor 16 is connected to the oscillation circuit. It is connected to a switch circuit 17 that operates in synchronization with the oscillation frequency of 13.

Further, the output of the second PWM comparator circuit 14 is P
It is connected to the output of the WM comparator circuit 12, and their pulse waveforms are logically AND-connected, and the connection point thereof is connected to the switching circuit 4.

The DC voltage of the input smoothing circuit 3 charges the capacitor 16 via the resistor 16, but since it operates in synchronization with the oscillation frequency of the oscillation circuit 13 and is discharged by the switch circuit 17, a so-called sawtooth wave voltage is generated as a second voltage. It will be applied to the input of the comparator circuit 14. Furthermore, the operations of the PWM comparator circuit 12 and the second comparator circuit 14 will be explained in detail with reference to FIG. 2. Figure 2 (C)
is the oscillation circuit 1 applied to the PWM comparator circuit 12
3 sawtooth wave voltage input and comparator circuit 1o output voltage B, (d
) indicates the output pulse waveform C1.

FIG. 2(e) shows the voltage F across the capacitor 16 applied to the second PWM comparator 14, the output voltage B of the comparison circuit 1o, and the phantom shows the output pulse waveform C2.

FIG. 2(q) shows a pulse output C which is applied to the switching circuit 4 by logically ANDing the output pulse waveform C1 of the PWM comparator 12 and the output pulse waveform C2 of the second PWM comparator 14. capacitor 16
The charging current for the voltage F across the input smoothing circuit 3 is determined by the DC voltage of the input smoothing circuit 3 and the resistor 15, and is discharged by the switch circuit 17. The operation timing of the switch circuit 17 is synchronized to be similar to the output waveform of the oscillation circuit 13. and it is working.

When controlled by the second (7) PWM comparator 14, that is, the voltage F across the capacitor 16
is set to rise earlier than the sawtooth voltage of the oscillation circuit 13, the capacitor is The voltage F across 16 moves to 21 or F2 as the charging current changes, changing the time ratio between the on period and off period E of the pulse output C. Since the change in duty ratio operates to keep the output voltage of the output terminal 2.2' constant, the output voltage of the comparator circuit 1o can remain stable even if it hardly changes. Furthermore, since the maximum output voltage B3 of the comparison circuit 10 is set by the Zener diode 20, the maximum value of the duty ratio is limited, but the maximum value of the duty ratio is also the same as the commercial AC applied to the input terminals 1 and 1'. It will change in proportion to the voltage fluctuation. Furthermore, even if the commercial AC voltage drops and the voltage F across the capacitor 16 rises later than the sawtooth voltage of the oscillation circuit 13, the second PWM comparator 1
Since the maximum value of the duty ratio is controlled instead of 4, the maximum value of the duty ratio can be prevented from increasing indefinitely as the commercial AC voltage decreases, and its absolute value can be set freely.

Effects of the Invention As described above, according to the present invention, stabilization of the output voltage due to fluctuations in the input voltage, that is, the commercial AC voltage or the DC voltage,
Since it is controlled directly by changes in the input voltage without depending on changes in the output level of the comparator circuit, the response is quick and transient fluctuations in the output voltage are extremely small. In addition, sufficient output voltage stability with respect to input voltage can be obtained without directly detecting and controlling the output voltage, so it is also possible to eliminate output voltage feedback and control the output voltage only on the primary side. be. Moreover, the rejection ratio of the commercial frequency ripple voltage included in the DC voltage is also reduced without using a special circuit. In addition, even if the duty ratio expands to its maximum value in a transient state regarding the load response such as the output voltage, the maximum duty ratio changes inversely proportionally to the input voltage. Since the magnetic flux density is almost constant, there is no need to design a transformer for the worst case, and the utilization rate of the transformer is increased, making it possible to downsize the transformer, which is advantageous in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a switching regulator device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing operating waveforms of the circuit diagram of FIG. FIG. 4 is an explanatory diagram showing operating waveforms of the conventional circuit diagram of FIG. 3. 3... Input smoothing circuit, 4... Switching circuit, 6... Transformer, 6.7...
・Diode, 8...Choke transformer, 9,
16...Capacitor, 1o...Comparison circuit, 11...Reference voltage circuit, 12゜14...
...PWM comparator circuit, 13...Oscillation circuit, 15...Resistor, 17...Switch circuit, 2o...Zener diode. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
figure

Claims (1)

[Claims] A switching circuit to which DC input voltage is supplied, a transformer to which the output of this switching circuit is supplied to the primary winding, a rectifying and smoothing circuit connected to the secondary winding of this transformer, and an output of this rectifying and smoothing circuit. A comparator circuit that detects a voltage, compares it with a reference voltage, and amplifies it; a PWM comparator circuit that compares the output voltage of this comparator circuit with the output voltage of an oscillation circuit to generate an on-off pulse waveform; The output operates the switching circuit, and a series charging circuit of a resistor and a capacitor connected to the DC input voltage includes a switching circuit that discharges the capacitor in synchronization with the oscillation cycle of the oscillation circuit, and a charging/discharging voltage waveform of the capacitor. and the output voltage of the comparison circuit to generate an on-off pulse waveform, the pulse waveform of the PWM comparator and the pulse waveform of the second PWM comparator are logically combined. A switching regulator device characterized in that the switching circuit is operated by AND connection.