JPS5843178A - Overcurrent detecting circuit - Google Patents

Abstract

PURPOSE:To simplify the circuit configuration of an overcurrent detecting circuit by connecting a plurality of primary coils of a current transformer to a plurality of output circuits of a DC/DC converter and obtaining an overcurrent detecting signal from the current of the secondary coil. CONSTITUTION:A switching transistor TR1 is controlled by a control circuit CONT3, and a plurality of output voltages V1, V2 are obtained from the secondary side of a transformer T1, thereby forming a power source of DC/DC converter type. A current transformer CT4 is provided, primary coils PW1, PW2 are respectively connected in series with the output coils S1, S2 of the transformer T1, the output of the secondary coil SW1 is compared with the prescribed value in the control circuit CONT3, thereby controlling the transistor TR1. Accordingly, the interference between a plurality of output circuits can be eliminated by suitably selecting the ratio of the coils of the transformer CT4, thereby detecting the overcurrent and simplifying the circuit configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overcurrent detection circuit, and more particularly to an overcurrent detection circuit in a multi-output power supply device having a plurality of power supply output circuits.

Conventionally, for example, the overcurrent detection method in the DC/DC converter type oi output power * device KsP is to output the λ power Rt- of the transformer a (computer tonne) and detect when the input voltage tIL exceeds a predetermined value. Detects the output current of the multi-mats output circuit and the one that operates the over-current waterfall protection circuit, and the output current of any one of the 0-power III output links is connected to the wrinkle-powered output link. When the current exceeds a predetermined current value, there is an overcurrent protection function and a percentage that allows the operator to perform fine stepping. .

1st ml Hiroshi, the above-mentioned K applied, using the former O direction, shows an example of the power device 01, 'Oka ■ O electric I1lli I position is DC power supply 11% ^ 1) 1
1cONTI, current totisis CTt, 7 meio 1'DI% for /tyl - pressure sound! Meio FD for 1%ll flow smoothing
I, Di eD4aDs,? w-kutuil L 1 e
In order to have the following:

11th IO **tec Hiro, control μs ONT
TRI is determined by l.
- around m beast on or d rus noble stream Ii transformer 'l' 101st order twill P I K11tl-ru, tkt
lPζ main diode DI#i) transistor T113i1
)I changes from conductive to non-conductive, and the voltage produced by the primary coil #PIKμ is set to a constant value at 9 o'clock, but since it is O, the secondary coils 81 and l1jK of the transformer -T1 are activated, and the nine alternating current coils are rectified, respectively. It is rectified by D4.
,-ri;il Ll, smooth:s)/Denna C1, Fra L!
, smooth;
A smoothing circuit consisting of B and 6 smoothes the residue and obtains an output.

1 In addition, in FIG. 1, the current Ix flowing in the secondary coil P1 of the transformer Tl0I is detected by the violet current transformer TIK, and the large II of the current 1nr is detected in the control circuit C0NTl.
When the current value exceeds a predetermined value, a λ overcurrent protection circuit is activated in the scissors control circuit C0NTl, and the primary current IIN is disconnected by keeping the d transistor TRI in a non-conducting state.

) In the method of detecting the input current lXM as described above,
For example, suppose there are 4 output circuits (nlt), and the output voltage R of each output circuit is l1eIIe-*I! If the lx output voltage is V*, Vse..., Vn, then the input current l
A stone expressed by the MF linear equation.

11) 1m (VsIs'+VsIm4""+VnIl)
K/V Bunka, ... (1) ζζ, K is transformer T
101@@@ It is determined by the ratio etc. t is a proportionality constant, and vxM is the input voltage. Therefore, the output power changes depending on the arbitrary O output and JIB6 load changes.
#5 The output circuit #l of the power circuit is expanded by the Ill detection method and any output fluctuation is caused by the output fluctuation.
Since the maximum current value that can be output from I to P varies, it has the disadvantage that the protection circuit does not operate until the output current becomes excessive.

The first ml shows a large power supply device which uses a system in which each output pipe is provided with a separate overcurrent detection circuit.

The 1ljso power supply has a current transformer σi or ° in each output circuit instead of the transformer 11T140 primary side.
It differs from the power supply device in the first example in that it is equipped with the same function as the one shown in Figure 1.

They are almost the same. .

Figure 8 shows the power supply device shown in Figure 1, and detects the overload fILt for each output circuit using the current transformers CTg and crsvc.
t%/-h is parts such as current transformer.

Many points 1kl + control circuit CON? ! There is an inconvenience when the dormitory becomes crowded. .

(1) The objective of the present invention is to solve the problems in the conventional example described above, and to overcome the problems with the overcurrent detection circuit of the multi-output power supply device.
・Based on the concept of detecting overcurrent i* in the output circuit using a current transformer with primary winding 1, it is simple and simple to increase the number of products by 1. I want to be able to do that.

In the overcurrent detection circuit of a multi-output power supply device having a plurality of power supply output circuits, each independent 0.1-order I It is characterized in that the current detected by #j- and flowing through the secondary 1111 of the current transformer is used as an overcurrent detection signal.

The 1J10 embodiment of the present invention will be described below using Eat i.

FIG. 3 shows a DC/DCW amplifier equipped with an overcurrent/current detection circuit according to an embodiment of the present invention. Method O power supply tawaraki meeting is shown.
There are multiple power supplies in the FJ diagram (2 Hiro in the diagram) 01
Next; PWI, PWI, O wire, Twist CT4t-circuit, detect the current of each power supply output open circuit. That is, the primary coils PWI and PN2 of the current transformer CT4 are connected in series with the secondary coils Bl and S2, respectively, and the current O*11 flowing through the secondary coil 8WIK of the current transformer CT4 is controlled by the control circuit CO'. NTS
Overcurrent can be detected by comparing it with a predetermined value at its own weight. In the FIG. 3 Oden III device, the 09th minute is the same as the 2nd rlA% except as described above, and the same reference symbols are used.

In an overcurrent detection circuit such as swJ, it is assumed that there are, for example, n power supply output paths, and each power output line is 1I It a Is e -1I.
n) Primary winding in current transformer JKO4 - 〇III number t n
lt g m@, m, mn.

If current transformer 02 secondary *so winding t m h+, t, current transformer JC0 secondary side current l11x is expressed by the following equation.

IAss(Itm+I*q+-+lmm-n/mB→l
Lt -m (2) (2) substitute), optional O
The output current of the power supply output wA path is jIN (however, N is the corresponding power supply output circuit KII and the required current %9Vfit) is the primary winding lll song), nJ, town (@mn). ) If the output current of other power supply output circuits changes, the output current of other power supply output circuits will be
The overcurrent protection circuit will start operating when there is a deviation of n+1 or more, but the number of turns ax(x■1, 2,
-, n) are set to appropriate values, it is possible to prevent the output current lx of each power output circuit from becoming excessively large.

As an example, in the power supply device of FIG. 3 having two power supply output circuits, the first primary of the current transformer CT4 @
P W and the second primary winding W20@several meters and ff1g are respectively 1 turn and 10 turns,
Also, the number of turns (second-best @5WIC) is 100 turns. In addition, the rated voltages of the first and second output circuits are Vtj5V and Vs = 10 V, respectively, and i1+wl is applied to the first and second output circuits, respectively.
()mu and! If it is assumed that the overcurrent protection circuit operates when a current of 5 mm flows, then the secondary detection current IA of the current transformer in this case is (formula) IA-(10X1+5X1o) /4oow'mo/lo
.

As an extreme example, in the case of an umbrella-shaped, small-sized bottle configuration, when the 10th output circuit OjL charge current is not flowing, that is, It=@011@eclipse, the current XsM is applied to the second output circuit.
When %O flows - the overcurrent protection circuit operates, the following relationship holds true.

(OXl×I*MX1G)/10G-110/10G,
', IsM=@(AJ) As a result, a current of 6 μm flows through the @go power connection, and the overcurrent protection system operates due to a large field eclipse.

Previous - 〇 No. 10v6 Kazuji KIOmu O current is flowing -
A value close to the operating current Is'' rim can be obtained.

Therefore, it is advantageous for Yangsha and others who want to strictly suppress the 20th output circuit IIO overcurrent tILt in 41.

Fin [against figure III O1! In the next form, considering the same example as above, I = ml OA, engineering sm 5AO
Input power 11 of the field (1) formula! Ii, , - as follows.

l±f (IIXll) + 111Xl) K/V engineering, -
100/V, Therefore, if the overcurrent protection circuit operates when I'MO current flows to the second output circuit when l1m1II6, then the following O relationship holds true. .

(5XO+ 10 xI'sM) K/'VXM Expansion Z0
0'/VXMe'e I'*M 10 (2) In other words, the overcurrent protection circuit operates only after a current of 1ffllllKIOm flows through the second output.6? Therefore, according to the present invention, it is necessary to select appropriate values for each turns ratio of the current transformer. ), the current of each output circuit of a power supply device with multiple output circuits can be accurately detected with a single current transformer, and the overcurrent detection circuit has a small number of parts *) * Simply become.

[Brief explanation of the drawing]

FIG. 1 and #I2 are electrical circuit diagrams showing a power supply device equipped with a conventional 0jIt flow detection as circuit, and #! FIG. 3 is an electrical circuit diagram showing a power supply device equipped with an overcurrent detection circuit according to an embodiment of the present invention. E l-...DC power 11, TRl-Mates tenda transition, T1-...Transformer, Dl, DIDS, D4゜D B-...Mayord %CT1. CT2. CT3゜C
T4-one current transformer, C0NTl, C0NT2°C
0NT3-control circuit, Ll, L2-Teyoi-ku coil, C
I, C2... Smoothing capacitor. Patent applicant Fujitsu Limited Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yukio Uchida Akira Yamaguchi

Claims (1)

[Claims] L In the overcurrent detection circuit of a multi-output power supply device having multiple power supply output circuits, the output current of each power supply output circuit is connected to one current transformer and each independent primary winding. An overcurrent detection circuit characterized in that the current flowing through the secondary winding 11 of the cough current is used as an overcurrent detection signal.