JPH02155459A - Booster type chopper power source - Google Patents

Abstract

PURPOSE:To suppress a rush current at the time of turning ON of a power source by turning OFF a chopping switching element by a control circuit before a charging/discharging inductor to be charged at the time of ON of the chopping switching element is magnetically saturated. CONSTITUTION:If the output voltage of a rectifier 1 is a rush current upper limit level or more when a power source switch 17 is closed, a Zener diode 21 is conducted, and an ON signal is input to the base of a chopping switching element 6 though a capacitor 23. Electromagnetic energy is stored in a charging/ discharging inductor 2. A control circuit 8 turns OFF the element 6 after a short period of time is elapsed. Thus, the electromagnetic energy stored in the inductor 2 is discharged, and a circuit current is lowered. Then, the element 6 is turned ON by the control circuit 8, and a current flows sequentially from the power source side to the inductor 2 (a blanking arrow) and the element 6. Thus, an excess rush current does not flow.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a step-up chopper power supply device used in various electronic devices.

Conventional technology Conventionally, boost choppers, which are used to obtain a DC output value by boosting the DC input value, generate an excessive inrush current when the power is turned on, causing problems such as tripping the power breaker and generating power supply noise due to the inrush current. There were various negative effects such as malfunctions on other electronic devices and welding and abrasion of power switch contacts.

For this reason, in order to reduce the inrush current value,
There are devices that employ an inrush current prevention circuit as shown in FIG. That is, the rectifier circuit 1 (as a DC input circuit)
RFC) is provided, and a charging/discharging inductor 2 (L) is connected to this rectifier circuit 1.
An output terminal 5 is connected to the output terminal 5 via a diode 3 (D) and a smoothing capacitor 4 (C,) serving as a smoothing circuit. A chopping switching element ¥3 (Q) is connected to the output side of the charging/discharging inductor 2. At the base of this chopping switching element 6, a control circuit 8 (C0C
) are connected.

Next, a rush current prevention circuit 9 is connected between the rectifier circuit 1 and the charging/discharging inductor 2. That is, 5CRIO is connected between the rectifier circuit 1 and the charging/discharging inductor 2, and a resistor 11 (R,) is connected in parallel to the 5CRIO. Then, voltage dividing resistors 12, 13 (R,,R,) are provided, and a capacitor 14 (
C, ) is connected to the SCR 10 through a Zener diode 15 (ZD) at the midpoint of the connection.
gate is connected.

In such a configuration, when the power is turned on, the rectifier circuit 1 converts the voltage into a full-wave rectified DC voltage. This full-wave rectified DC voltage is applied to the capacitor 4 through the charging/discharging inductor 2 and the diode 3, and the current charges the capacitor 4, and the resistor 5CRIO, which is not yet turned on, is connected in parallel. Pass through 11. The resistance value of this resistor 11 is set to a value that limits the rush current when the power is turned on so as to cause no practical problems.

In this way, the rush current immediately after the power is turned on is limited by the resistor 11, but at the same time, the full-wave rectified DC voltage is
The capacitor 14 is charged by the time constant of the resistors 12 and 13 and the capacitor 14, and this value is transferred to the Zener diode 15.
When the Zener operating voltage of 5CRIO is exceeded, the voltage becomes the gate signal voltage of 5CRIO, which turns 5CRIO ON. Therefore, the current flowing through the resistor 11 flows through 5CRIO, and heat loss due to the resistor 11 during normal operation is prevented.

That is, to summarize such an operation, immediately after the power is turned on, the inrush current is suppressed by the resistor 11, and during the subsequent normal operation, the 5CRIO is energized to suppress the heat generation of the resistor 11. A two-step operation is performed.

Problems to be Solved by the Invention In the case where the inrush current prevention circuit 9 as described above is provided, both the 5CRIO and the resistor 11 must have a current capacity that can withstand the circuit current during steady operation. In addition, both 5CRIO and resistor 11 have to take into consideration heat radiation against heat generation, and are expensive in terms of price.
However, the structure is also becoming larger.

Means for Solving the Problems A DC power source, a charging/discharging inductor connected between the DC power source and an output terminal, a smoothing circuit for smoothing the output voltage of the charging/discharging inductor, and a charging/discharging inductor connected between the DC power source and an output terminal. a chopping switching element that controls charging and discharging of the inductor; a starting circuit that instantly turns on the chopping switching element when the output voltage of the DC power source exceeds a predetermined value; and a control circuit that controls ON/OFF of the chopping switching element.

A control circuit turns off the chopping switching element before the charging/discharging inductor that is charged when the chopping switching element is turned on becomes magnetically saturated, and thereafter the control circuit controls the operation of the chopping switching element. As a result, the inrush current at power-on is effectively suppressed using inexpensive components with small current capacity, and this prevents malfunction of other electronic devices due to tripping of the power breaker, generation of power supply noise caused by the inrush current, and power switch. This prevents various negative effects such as welding and abrasion of the contacts.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. Components that are the same as those described with reference to FIG. 3 are designated by the same reference numerals, and description thereof will be omitted. In this embodiment, a rectifier circuit 1 is connected to an AC power source 16 via a power switch 17 to constitute a DC power source, and a chopping switching element 6
A starting circuit 18 is connected to the base of the .

That is, the starting circuit 18 has a voltage dividing resistor of 19°20(
R,,R,), a Zener diode 21 (D,) connected in parallel to the voltage dividing resistor 19, and the voltage dividing resistor 19.20.
A resistor 22 (R
, ) and a capacitor 23 (C1) in parallel.

In addition, the smoothing capacitor 4 (C,) has a resistor 24
(R,) are connected in parallel.

In such a configuration, the charging/discharging inductor 2 has an inductance value designed to be the optimum value for various conditions given by the chopper oscillation frequency etc. in order to operate as a boost chopper. , this value is designed corresponding to the chopping oscillation frequency f. This chopping oscillation frequency r is set in a range of about 30 to 60 kHz.

However, when the chopping oscillation frequency f is set within the range described above, the following problem occurs in the conventional circuit. That is, if the full-wave rectified DC voltage of the AC power supply 16 is higher than the inrush current upper limit level as shown in FIG. 2(a) when the power switch 17 is ONL, the charging/discharging inductor 2 is magnetically It becomes saturated and an excessive rush current flows.

22. The waveform shown in Figure 2(b) is an enlarged horizontal time axis of the waveform shown in Figure 2(a), but it shows the waveform of the circuit current before improvement. It is. In this waveform diagram, time TN is a period in which the charging/discharging inductor 2 is not yet saturated, and time Ts is a period in which the charging/discharging inductor 2 is saturated and an excessive inrush current is flowing. Of course, an excessive inrush current does not flow at a voltage value below the inrush current upper limit level shown in FIG. 2(a).

The present embodiment focuses on the period in which the charging/discharging inductor 2 is not yet saturated, that is, the time TN. That is, when the power switch 17 is turned on, if the output voltage of the rectifier circuit 1 is equal to or higher than the inrush current upper limit level shown in FIG. An ON signal is applied to the base of the switching element 6, and the chopping switching element 6 is instantly turned on. and,
The circuit current after the improvement rises as shown at the first ON time in FIG. 2(C) in accordance with the fluctuation in the period of time TN in FIG. 2(b). During this time, electromagnetic energy is accumulated in the charging/discharging inductor 2.

Therefore, the control circuit 8 turns the chopping switching element 6 ON/OFF using the chopping oscillation frequency f.
Therefore, the chopping switching element 6 is turned off after a time shorter than the time TN has elapsed from the timing when the power switch 17 was turned on. By turning off this chopping switching element 6, the electromagnetic energy accumulated in the charging/discharging inductor 2 is released, and the circuit current (charging/discharging inductor 2
(current flowing through) decreases. At this time, the terminal voltage Vc of the capacitor 4 increases and is charged to a specified value.

Next, the control circuit 8 controls the chopping oscillation frequency f,
to turn on the chopping switching element 6. When the chopping switching element 6 is turned on, a current flows from the power source side to the charging/discharging inductor 2 -> the chopping switching element 6 in this order. Since this current value has already been charged with the voltage Vc of the capacitor 4, no excessive current flows even if the voltage of the rectifier circuit I is equal to or higher than the inrush current upper limit level.

That is, the voltage applied to the charging/discharging inductor 2 is
Since there is a difference between the voltage of the rectifier circuit 1 and the voltage Vc between the terminals of the capacitor 4, an excessive rush current does not flow.

In this way, after that, the chopping switching element 6 is repeatedly turned ON and OFF with the specified chopping oscillation frequency f by the control circuit 8, and the charge discharged to the output side load is charged, and a specified ripple voltage is output. Supplying voltage to the load occurs continuously.

Effects of the Invention As described above, the present invention includes a DC power source, a charging/discharging inductor connected between the DC power source and an output terminal, and a smoothing circuit that smoothes the output voltage of the charging/discharging inductor. A chopping switching element that controls charging and discharging of the charging and discharging inductor, a starting circuit that instantly turns on the chopping switching element when the output voltage of the DC power supply exceeds a predetermined value, and starting with this starting circuit. The chopping switching element is turned on and off by the control circuit before the charging/discharging inductor that is charged when the chopping switching element is turned on becomes magnetically saturated. Since the device is turned off and the operation of the chopping switching element is then controlled by the control circuit, the inrush current when the power is turned on is effectively suppressed using inexpensive components with small current capacity. It is possible to prevent various adverse effects such as malfunction of other electronic devices due to breaker tripping and generation of power supply noise due to inrush current, and welding and abrasion of power switch contacts.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2(a)
(b), (c), and (d) are waveform diagrams showing waveforms at various parts, and FIG. 3 is a circuit diagram showing an example of the conventional device. ■...DC power supply, 2...Charging/discharging inductor, 4...
... Smoothing circuit, 5... Output terminal, 6... Switching element for chopping, 8... Control circuit, 16...
AC power supply, 18...starting circuit" 0...disaster! 711! ! J藉5Z Figure Procedures 1u Official Book (Method) [, Indication of Case Patent Application No. 63-305291 2, Name of Invention Step-Up Chopper Power Supply Device 3, Person Making Amendment Relationship with Case

Claims (1)

[Claims] A DC power supply, a charging/discharging inductor connected between the DC power supply and an output terminal, a smoothing circuit for smoothing the output voltage of the charging/discharging inductor, and controlling charging/discharging of the charging/discharging inductor. a switching element for chopping; a starting circuit that instantly turns on the switching element for chopping when the output voltage of the DC power source exceeds a predetermined value; and turning on the switching element for chopping after being started by the starting circuit. - A control circuit that controls turning off the chopping switching element, and the chopping switching element is turned off by the control circuit before the charging/discharging inductor that is charged when the chopping switching element is turned on becomes magnetically saturated. Features a step-up chopper power supply.