JPH04364328A - Rash current suppressing circuit at turning on power source - Google Patents

Abstract

PURPOSE:To suppress rush current without increasing dissipation of power through a resistor by detecting the voltage between voltage detecting windings mounted on a power supply transformer through a Zener diode thereby regulating the time for turning the power supply ON. CONSTITUTION:Voltage between the windings 5, 6 of a power supply transformer T1 is rectified and applied on a Zener diode D20. Voltage across a resistor R20 is fed to a microcomputer IC2 which closes a relay 1 when the voltage applied on the terminal 4 is zero upon turn ON of a power switch SW1. On the other hand, an AC voltage for feeding a DC voltage to a main load L is rectified through diodes D10-D13 wherein the rush current to be produced upon closure of the relay 1 is low because the relay 1 is closed when the AC voltage is low. Consequently, rush current can be suppressed without requiring a resistor for suppressing the rush current.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention reduces the current when the power is turned on for equipment that directly rectifies commercial power, such as television receivers, and that the instantaneous voltage drop caused by the current does not affect other equipment. This invention relates to a power supply circuit that eliminates problems such as abnormal operation and reduces the burden on the power switch, thereby eliminating burn-out of contacts and ignition due to the generation of sparks.

0002

2. Description of the Related Art In recent years, television receivers have become more sophisticated and larger in size, and their power consumption has also increased accordingly. As power consumption increases, the current required when the power is turned on is also increasing, and the effects on other systems are becoming wider. A conventional method for reducing current when power is turned on will be described below. FIG. 3 shows a conventional power supply circuit. In FIG. 3, T1 is a power transformer for supplying a voltage suitable for the load. D1 to D4 are diodes that rectify the voltage taken out from the winding of T1. C1 is a filter capacitor, and IC2 is a microcomputer (hereinafter referred to as microcomputer) that detects that the power switch SE1 is pressed and outputs a signal to control switching on and off of the relay 1. SW1 is the power switch, relay 1
is an electromagnetic open/close switch (hereinafter referred to as a relay) that turns on and off a large power load. R10 is a resistor and is connected in series with relay 1. Q1 is a transistor that drives relay 1, and R2 is a resistor that applies bias to the base of Q1. D10 to D13 are rectifier diodes for supplying DC voltage to load L, C2 is a filter capacitor thereof, and load L is the main load of this power supply circuit. The operation of the power supply circuit configured as above will be described below. First, winding 3-4 of power transformer T1
The voltage between them is rectified by D1 to D4 and supplied to terminal 1 of the microcomputer and terminal 1 of the relay. Furthermore, a bias voltage is supplied to the base of Q1 through R2. Terminal 3 of microcomputer IC2 becomes ground potential at the same time as the positive voltage is supplied to terminal 1, turning off Q1. When a positive voltage is applied to terminal 2 of microcomputer IC2, the impedance of terminal 3 of IC2 increases, and bias voltage is applied to Q1 through R2, turning it ON.
state and closes relay 1. When relay 1 closes, voltage is applied to D10 to D13, and voltage is applied to load L through the filter capacitor. At this time D10~
D13 is one of 60 or 50 cycles of AC shown in Figure 4.
00V is applied, and the voltage changes every moment. When relay 1 closes at time t1 in FIG. 4, the voltage is 0V, so there is no current charging C2 or flowing through load L, and no inrush current flows when relay 1 closes. When the relay 1 closes at time t2 in FIG. 4, a voltage of aV is applied, and a current flows through the charging current of C2 and the load L in proportion to the voltage aV. Further, when the relay 1 closes at time t3 in FIG. 4, a voltage of bV is applied, and a larger charging current of C2 and current flow to the load L than when the relay closes at time t2. In this way, the time at which the relay 1 closes is not regulated at all, and the relay 1 closes at a completely arbitrary time depending on the time at which SW1 is closed. At this time, since there is a resistor R10 in series with relay 1, the inrush current flowing at the moment relay 1 closes is limited by the resistance value of R1, but even after relay 1 closes, it remains inserted and is consumed by R1. The power consumed is wasted power. To reduce inrush current,
Although it would be possible to increase the resistance value of R1, the wasted power consumed by the resistor increases and the resistance value cannot be set to a value sufficient to reduce the inrush current. Therefore, it is necessary for the contacts of the relay 1 to have a size and contact that can withstand a much larger inrush current than during normal operation.

0003

[Problems to be Solved by the Invention] However, in the above conventional configuration, the resistance value of R1 must be increased in order to reduce the inrush current, but this increases the wasted power consumed by the resistor. It is not possible to obtain a sufficient resistance value. For this reason, the inrush current can only be reduced to about 20 times that of normal operation, and there remains a possibility that this inrush current will affect other devices. For this reason, there is a problem in that the contacts of the relay 1 must be sized and made to withstand a much larger inrush current than during normal operation. The present invention solves the above conventional problems,
1. In addition to reducing the inrush current when the power is turned on to prevent it from adversely affecting other equipment, it also eliminates the need to use expensive precious metals for the contacts of Relay 1 to withstand large currents, preventing burn-out of the contacts. , to eliminate the risk of fire and reduce costs. 2. The purpose of this is to eliminate the resistor inserted to reduce the rush current when the power is turned on, and to eliminate wasted power consumption due to the resistor.

0004

[Means for Solving the Problems] In order to achieve this object, the power supply circuit of the present invention reduces the inrush current when the power is turned on by regulating the closing time of the relay 1, and is inserted in series with the relay 1. It has a configuration that can eliminate unnecessary power consumption by eliminating the conventional resistance.

[0005]

[Function] With this configuration, the closing time of relay 1 is regulated and the inrush current when the power is turned on is reduced.By reducing the inrush current when the power is turned on, the resistor inserted in series with the relay 1 is no longer required. It is possible to eliminate unnecessary power consumption.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, T1 is a power transformer for supplying a voltage suitable for the load. D1 to D4 are diodes that rectify the voltage taken out from the winding of T1. C1 is a filter capacitor, and IC2 is a microcomputer (hereinafter referred to as microcomputer) that detects when the power switch is pressed and outputs a signal to control the switching on and off of relay 1. SW1 is a power switch, and relay 1 is an electromagnetic switch (hereinafter referred to as relay) that turns on and off a large power load. Q1 is a transistor that drives relay 1, and R2 is a resistor that applies bias to the base of Q1. D10 to D13 are rectifier diodes for supplying DC voltage to load L, C2 is a filter capacitor thereof, and load L is the main load of this power supply circuit. The above is the same as the conventional one, but the windings 5-6 of the power transformer T1 are voltage detection windings added to the secondary side. D5~
D8 is a rectifier diode that rectifies the voltage between the windings 5 and 6. The diode D20 is a Zener diode, and R2 is a resistor that serves as a load for the Zener diode D20. The intersection is connected to the voltage detection terminal 4 of IC2. The operation of the power supply circuit configured as described above will be explained using FIG. 1. First, the voltage obtained by rectifying the voltage between the windings 5 and 6 of the power transformer T1 is a pulsating voltage obtained by double-wave rectification of the alternating current voltage, as shown in FIG. 2a. When this pulsating voltage is applied to the Zener diode D20, the voltage at both ends of R20 is as shown in Figure 2.
As shown in FIG. 2, it is possible to obtain a voltage that becomes zero potential during the period of time t1. This zero potential period t1 can be changed by selecting the Zener voltage of the Zener diode. The intersection of the Zener diode and the resistor R2 is connected to the voltage detection terminal 4 of the microcomputer IC2, and detects the zero potential period t1 of the applied voltage and other periods. After the power switch SW1 is closed, the relay drive output terminal 3 of the microcomputer IC2 detects the zero potential of the voltage applied to the terminal 4, and outputs a drive voltage so that the relay 1 closes during the period of the zero potential. . That is, the relay 1 can be closed during a period when the voltage of the AC power source is low. On the other hand, in order to supply DC voltage to the main load L, the AC voltage is supplied to the diode D1.
0 to D13, filtered by capacitor C2, and supplied to load L. At this time, the rush current that flows when relay 1 closes is proportional to the voltage applied at that time. Therefore, in order to reduce the inrush current that flows when relay 1 closes, it is necessary to
If it closes, the inrush current can be reduced. In other words, by closing relay 1 during the period t1 in b in Figure 2, which is detected from the winding of transformer T1 which is proportional to the input voltage, the inrush current when the power is turned on can be reduced by connecting a resistor in series with relay 1 as in the conventional example. It can be reduced without insertion.

[0007]

[Effects of the Invention] As described above, the present invention provides a voltage detection winding in a power transformer, detects the voltage with a Zener diode, and regulates the time when the power is turned on, thereby reducing wasted power consumption due to resistance. It is possible to realize an excellent power supply circuit that can reduce inrush current when turning on the power of equipment without having to do so.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the power supply circuit of the present invention.

[Fig. 2] Voltage waveform diagram showing voltage detection and power-on timing in the embodiment of the present invention

[Figure 3] Power supply circuit diagram in conventional example

[Figure 4] Waveform diagram of power supply voltage showing time when power is turned on in conventional example

[Explanation of symbols]

1 T1: Power transformer 2 D1-D8, D10-D13: Rectifier diode 3
D20: Zener diode 4 C1, C2: Capacitor 5 IC1: Microcomputer 6 Q1: Transistor 7 L: Load 8 Relay 1: Electromagnetic switch 9 SW1: Power switch

Claims (2)

[Claims] 1. A pulsating current voltage detecting means obtained by directly rectifying a commercial power supply, and a means for controlling power-on timing based on a detection signal from the pulsating current voltage detecting means,
A circuit for reducing inrush current when power is turned on, characterized in that the power is turned on in a low voltage region. 2. The inrush current reduction circuit when power is turned on according to claim 1, wherein the timing at which the power is turned on is determined based on a signal detected by a Zener diode.