JPS5819117A - Overload protecting system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention is an overload maintenance type, series control type constant tow pressure NmK.
Concerning the four-way load maintenance method.

1 is a diagram showing an example of a conventional overload protection method in a series control type constant voltage circuit. In Figure 11, the DC voltage V supplied from the voltage gIAB is constant voltage - control 11
After being stabilized through the series 111111m) Rangis-Qlt controlled by the cTL, the voltage vL
jIP and load current! Lt is supplied] The load current IL is connected to the series control transistor Ql and the overcurrent detection resistor R1.
1, the overcurrent detection resistor R
IK voltage drop V is embarrassing. Said load current! When L is within the standard value, the scissor voltage V1m is the standard voltage fEV
* and transistor Q2 remains in the blocking region.

The voltage drop Vll is input to the blind input terminal, and the reference voltage V is input to the inverting input terminal of the comparator.The output voltage VA+ is output? L na i. The load current is 1 in a tilted state.
．． When increases beyond the standard value, the voltage drop V
The set increases to bring the transistor Q2 into the linear region and control the pace current of the self-regulating series control transistor Ql, thereby causing the series control transistor Qlk to flow through the load tIL current! L is limited, and historically the voltage drop V set is the reference voltage v
When it exceeds 1, the output voltage VAs is output from the comparator 1, and is applied to the base of the transistor 920 through the diode DI and the resistor R4, and also to the base of the transistor 920 through the diode DI and the resistor R8.
1? t, is supplied to the base of transistor Q3 (supplied) and leads both transistors Q2 and Q3' into the mausoleum region. As a result, the series control transistor Ql becomes jIwr-shaped 9,
Because the load voltage tit I L is blocked. Note that the load current *Ig
The voltage drop V caused in the overcurrent detection resistor R1 by , is O and 1kh, and the positive phase input terminal voltage V+ of the comparator M1 remains in the saturation region until the capacitor tel is charged by the output voltage VA+. Since the inverting input terminal voltage V- is maintained at a sufficiently low voltage by 93, the output voltage V is maintained during that time, and the transistor Q2
and Qa are kept in the saturation region, maintaining the series control transistor Ql) 11 Rjll cutoff ii+'. When the capacitor CI finishes charging, the positive phase input terminal voltage V+ of the first comparator AI becomes lower than the inverting input terminal voltage V-, so the output voltage VAt stops and the transistors Q2 and Qa are set to the initial state 11Kj! I
I, series 1tlJl11) The transistor QIC also has a load current f
iIL begins to flow. The above process is like an overload.
KToru is repeated 5. Series control transistor JQl
lProtects from destruction due to large power losses.

The waveforms of each N1IcIEtIP and 11th stream in the above process are shown in FIG.

As is clear from the above explanation, in the conventional overload protection system, the load current IL increases by 4 m! due to overload. AI is activated and the load current IL\t311 is cut off during the charging period of the capacitor tel. Therefore, the current load t - the value in the operating state, and the new load t - in the case of parallel connection, the charging current momentarily flows into the smoothing capacitor normally installed in the new load. Current! L is temporarily cut off, which disturbs the operation of the current load Wt.

It is an object of the present invention to eliminate the drawbacks of the conventional overload protection methods as described above, and to eliminate the p precious charge tI! by the peak current generated when adding a new load. , tf! The aim is to realize an overload protection system that will not cause interruptions.

The purpose of this is to provide a means for detecting that the load current exceeds a specified value in a series control type constant voltage circuit and restricting the load current, and a means for detecting that the load current exceeds the specified value for a certain period of time. The means for detecting this and cutting off the load current for a predetermined period of time, and the setting of t, can be achieved.

Hereinafter, one embodiment of the present invention will be explained using Figures 3 and 4. FIG. 3 is a diagram showing an overload protection system according to an embodiment of the present invention, and FIG. 4 is a diagram showing various voltage and current waveforms shown in FIG. Note that the same reference numerals indicate the same objects throughout the figures. The difference from Fig. 111 in Fig. 3 is that the voltage drop Vll of the current detection resistor R1 is It consists of a capacitor C2 and is supplied via an integrating circuit.
In IEIIII, the series control transistor QITh
and the load LK is supplied via the overcurrent detection resistor Rut.
Load current! However, due to the addition of a new load, the specified value at is instantaneously exceeded (see Figure 4).

As a result, a voltage drop Vl occurs across the overcurrent detection resistor R1.
+ also increases instantaneously, leading to the transistor Q2t- which was previously in the blocking region, and by controlling the base current of the series transistor Q1, the series control transistor Qlt- Load current flows! Since the voltage drop VB, which is input to the positive phase input terminal 10 of the comparison iA2, exceeds the reference voltage Vstl'1 inputted to the inverting input terminal 9, the output voltage VAI is reduced from the ratio 11WA2. is output and integrated by the integration circuit. The output voltage of the integrating circuit is connected to the diode D3t-
The positive-phase input terminal voltage V0 is input to the positive-phase input terminal 0 of the comparison @A1 through the voltage V0, but since the time constant determined by the resistors R6 and R7 and the capacitor C2 is set to be sufficiently long, the positive-phase input Before the terminal voltage Y0 exceeds the reference voltage η input to the inverting input terminal - of the comparator M1, the load current! L returns to below the reference value p1, and the voltage drop VRt also falls below the reference voltage v), and the comparator A2 also completely stops the output voltage V. As a result, the comparator A1 does not output the utility voltage Vm.

Since transistors Q2 and Ql are not brought into the saturation region as shown in FIG. In this case, the series control transistor Ql is the load current! Comparator A2 continues to output the output voltage Vh* in the Lt-limited state. As a result, the positive-phase input terminal voltage V÷ of the comparator A1 increases beyond the reference voltage Vat, so the comparison IIAIFi outputs an output voltage vAlt- as in FIG. 1 and continues until the capacitor CI is charged. Wow.

Meanwhile, transistors Q2 and C3 are brought into the saturation region, and the series control transistor Ql#i is cut off and the load current RIL is blocked.

As is clear from the above lIi@, according to this example,
Load current! If L instantaneously exceeds the standard value, such as when a new load is added, the series control transistor Qltj
By simply limiting the load current R1t, t, the load current is cut off only when the overload condition continues for a certain period of time determined from the time constant of the integrating circuit. This is only one embodiment of the invention, and many modifications may be considered to realize the overload protection system, but the effects of the invention remain the same in any case.

As described above, according to the present invention, in response to a temporary overload, the series control type constant voltage circuit only limits the load tmt, and does not unnecessarily cut off the load current. It is possible to add new loads without damaging the operating status of the load.

[Brief explanation of the drawing]

Figure 112 is a diagram showing various voltage and current waveforms in Figure 1, and Figure 3 is an example of an embodiment of the present invention. FIG. 4 is a diagram showing various voltage and current waveforms in FIG. 3. In the figure, B is a power supply, L is a load, CTL is a constant voltage control unit, Q1 is a series control transistor, R1 is an overcurrent detection resistor, A1 and A2 are comparators, C2 and C3 are transistors, Dl, D2 . DB and D4 are diodes,
CI and C2 are capacitors, R2 to R7 are resistors, V
and vL are DC voltages, vl is voltage drop, ■+ is positive input terminal voltage, V- is inverting input terminal voltage, VAI and V are output voltages, vth and vlFi reference voltages, IL
indicates the load current. My representative, Hiroshi Matsuoka, 1st figure, 3rd figure, Wk Shitong Roubin, 1st arrest, 2nd figure, 4th figure.

Claims (1)

[Claims] In a series control type constant voltage circuit, a means for detecting that a load current is in danger of exceeding a specified value and limiting the load current;
An overload protection system in which a means is provided for detecting that the load current exceeds a specified value for a predetermined period of time and interrupting the load current for a predetermined period of time.