JPH04133631A - Backup circuit for power supply - Google Patents

Abstract

PURPOSE:To shorten the charging time of a capacitor by providing a constant- current charging means charging the capacitor for backing up a power supply by constant currents and a charging inhibiting means inhibiting the charging operation of the constant-current charging means when the capacitor is charged up to fixed voltage. CONSTITUTION:When a unit 200 is connected to a power unit 100 when a capacitor 240 is hardly charged by charges, the output voltage Vc of a comparator 271 reaches a low level, a transistor 273 for switching is brought to an OFF state, a transistor 264 for constant currents is brought to an ON state, and the capacitor 240 is charged by constant currents. When the charging voltage Vb of the capacitor 240 is made larger than the output voltage Vref2 of a constant voltage circuit 272, the output voltage Vc of the comparator 271 reaches a high level, and the transistor 273 is brought to the ON state. Accordingly, the transistor 264 for constant currents is brought to the OFF state, and the charging of the capacitor 240 is inhibited.

Description

[Detailed description of the invention]

[Summary] Regarding the power supply backup circuit that backs up the power supply using the charging voltage of the capacitor, it is possible to not only prevent malfunction of the circuit already connected to the power supply unit but also shorten the charging time of the capacitor. The power source C is intended to provide a Quambu circuit, and includes a power backup capacitor, a constant current charging means for charging this capacitor with a constant current, and a constant current charging means for charging the capacitor to a predetermined voltage. When,
and charging inhibiting means for inhibiting the charging operation of the constant current charging means. [Industrial Application Field] The present invention relates to a power supply backup circuit that banks up a power supply by using the charged N N voltage of a capacitor. In general, electronic devices often proceed with the next process while sequentially accumulating processing results. For example, in electronic devices that use computers, processing results are sequentially accumulated in the registers of the central processing unit (hereinafter referred to as CPU) or in memory that can be read and written at any time (hereinafter referred to as RAM) while proceeding with the next process. It looks like this. Therefore, in such electronic equipment, a power backup circuit is required to back up the electronic equipment when the power is cut off. [Prior Art] Conventionally, as a t-source bank-up circuit for a CPU or RAM, a circuit that utilizes a charging voltage of a capacitor is known. This is because the power consumption of the RAM in the CP is small. However, the t'a backup circuit, which uses voltage to charge the capacitor, has the following problems. This will be explained below with reference to FIGS. 7 to 11. FIG. 7 is a block diagram showing an example of the implementation configuration of a communication device that requires a source bank-up circuit. The illustrated communication equipment is designed to construct a target system by dividing the circuit into a plurality of units 100, 200, and 300 and inserting these into a backboard 400 as appropriate for maintenance and operation. Here, the unit 100 is an 1iifi unit having a direct current/direct current conversion (hereinafter referred to as DC/DC conversion) function for converting a primary power source to a secondary power source. Unit 200 is a unit incorporating a circuit 210 that requires a TX source hack amplifier. Therefore, this unit 200 also incorporates a source bank up circuit 220. The unit 300 is a unit incorporating a circuit 310 that does not require a power supply blow-up. In addition, the units 200 and 300 are the backboard 400.
When inserted into the 'W source unit 100, it is connected to the 'W source unit 100 through connectors 500, 600, and 700. FIG. 8 is a circuit diagram showing the configuration of an example of a conventional power hack amplifier circuit incorporated in the unit 200. The illustrated power backup device consists of a diode 230 and a large capacitor 240. Here, diode 2
30, for example, connects the unit 200 to the backboard 400.
This is inserted to prevent the capacitor 240 from discharging when the terminal on the unit 200 side of the connector 6 (11) becomes short-circuited when the capacitor 6 (11) is pulled out. In such a configuration, when the unit 200 is inserted into the backboard 400, the unit 200 is connected to the power supply unit 100 via the connector 500600. As a result, from the ii source unit 100 to the connector 5
00.600 and the diode 230, and the capacitor 240 is charged. Therefore, even if the power supply unit 100 breaks down or the unit 200 is pulled out from the backboard 400 after the capacitor 240 has been charged, the power supply to the circuit 210 will continue to flow through the capacitor 240.
It is backed up by a charging pressure of 40 N. However, in this power supply backup circuit, when the unit 30o is inserted into the hack board 40(), when the capacitor 240 is inserted into the hack board 400, the unit 3(11) is There is a problem in that the circuit 310 may malfunction. This will be explained with reference to FIG. FIG. 9 shows a state in which the unit 300 is inserted into the bank board 400 and the capacitor 240 is hardly charged.
8 is a diagram showing signal waveforms of each part in FIG. 8 when inserted into 00. FIG. Here, FIG. 8(a) shows the output current 1 of the t'g unit 1 (11), and FIG. 8(b) shows the t source voltage Va of the circuit 310, that is, the voltage at point a in FIG. The same figure (c
) indicates the power supply voltage vb of the circuit 210, that is, the voltage at point b in FIG. t indicates the time when the unit 200 was inserted into the backboard 400. Before inserting the unit 200 into the backboard 400,
Current flows from the power supply unit 100 only to the second unit 300. On the other hand, when the unit 200 is inserted into the backboard 400, current flows from the power supply unit 100 to the unit 200 as well. At this time, capacitor 2
40 has almost no charge, so a large charging current flows. As a result, power supply unit 1 (11
) exceeds the rated current IL, as shown in FIG. 9(a). As a result, the output voltage of power supply unit 1 (11) decreases. As a result, the power supply voltage Va of the circuit 310 decreases as shown in FIG. 7(b). As a result, the circuit 310 malfunctions. FIG. 10 is a circuit diagram showing the configuration of a conventionally known power supply backup circuit that can solve this problem. The illustrated power bank amplifier circuit includes a capacitor 240 and a resistor 250 connected in series. According to such a configuration, when the unit 2 (11) is inserted, the charging current of the capacitor 240 is suppressed by the resistor 250, so as shown in FIG. The output current ■ will not exceed the rated current JL. As a result, as shown in FIG. 11(b),
Since the power supply voltage Va of the circuit 310 does not decrease,
Malfunction of this circuit 310 can be prevented. However, in such a configuration, since the capacitor 240 is charged based on the time constant defined by the resistor 250 and the capacitor 240, the charging time CT of the capacitor 240 is shortened as shown in FIG. 11(c). The problem is that it is long. [Problems to be Solved by the Invention] As described above, in a power backup circuit using a capacitor, conventionally, by connecting a resistor in series with the power backup capacitor, the circuit already connected to the TA unit can be Since it is designed to prevent malfunction, there was a problem in that the charging time of the capacitor became longer. Therefore, an object of the present invention is to provide a power supply back amplifier circuit that can not only prevent malfunction of the circuit already connected to the power supply unit but also shorten the charging time of the capacitor. Means for Solving the Problems] Fig. 1 is a diagram showing the basic configuration of the present invention. In the figure, 11 is a capacitor for power backup. 12 is a capacitor 12 connected with a constant current. 13. Charge inhibiting means for inhibiting the charging operation of the constant current charging means 13 when the capacitor 11 is charged to a predetermined voltage by the constant current charging means 12. (Function) According to the above configuration, the power supply huff 2 and 1 circuit are connected to the power supply unit
When the capacitor 11 is connected to the constant current charging means 1
2, it is charged with constant current. Therefore, even if the II source backup circuit in which the capacitor 11 is hardly charged is connected to the power supply unit, the output current of the power supply unit will not exceed the rated current. This can prevent circuits already connected to the power supply unit from malfunctioning due to a drop in the power supply voltage. Further, since the capacitor 11 is connected to the N source unit and simultaneously charged with a constant current, the charging time does not become long. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 is a circuit diagram showing the configuration of the first embodiment of the present invention. In FIG. 2, the same parts as in FIG. 8 are given the same reference numerals, and detailed explanations will be omitted. In the figure, 250 is a DC/DC conversion circuit that compensates for the voltage drop of the diode 230 by boosting the output voltage of the power supply unit 1oo by DC/DC conversion. 260 is a constant current charging circuit that charges the capacitor 240 with a constant current. 270 is a charging inhibiting circuit that prevents overcharging of the capacitor 240 by forcibly inhibiting the charging operation of the constant current charging circuit 260 when the charging voltage vb of the capacitor 240 reaches a predetermined voltage. The constant current charging circuit 260 includes a current detection resistor 261,
It consists of a constant voltage circuit 262, an operational amplifier 263, and a constant 1f diversion transistor 264. Here, one end of the current detection resistor 261 is connected to the diode 2
30, and the other end is connected to the collector of a constant current transistor 264. Further, the voltage at one end of the current detection resistor 261 is increased by a predetermined voltage 4,1 by a constant voltage circuit 262 and is supplied to an inverting input terminal of an operational amplifier 263. The non-inverting input terminal of this operational amplifier 263 is supplied with the voltage at the other end of the current detection resistor 261 . The output voltage of the operational amplifier 263 is supplied to the base of a constant current transistor 264. In such a configuration, the constant current charging circuit 260 detects the charging of the capacitor 240 by converting the current into a voltage component of the resistor 261, and based on this detection output, connects the collector and emitter to the charging path of the capacitor 240. By controlling the base potential of the inserted constant current transistor 264, the capacitor 240 is charged with a constant current. That is, as the current increases through the collector of the constant current transistor 264, the voltage drop across the current detection resistor 261 becomes
When the voltage drop exceeds the voltage drop of the constant voltage circuit 262, the output voltage of the operational amplifier 263 decreases. As a result, the base potential of the constant current transistor 264 decreases, and its collector Na decreases. Conversely, constant current transistor 2
When the collector current of 64 decreases and the voltage drop across resistor 261 becomes smaller than the voltage drop across constant voltage circuit 262, the output voltage of operational amplifier 263 increases. As a result, the heath potential of the constant current transistor 264 increases, and its collector current decreases. As a result, the collector current of the transistor 264 is controlled so that the voltage drop across the resistor 261 is equal to the voltage drop across the constant voltage circuit 262, resulting in a constant current. The charge prohibition circuit 270 includes a comparator 271, a constant voltage generation circuit 272, and a switching transistor 273. Here, the charging voltage of the capacitor 240 is supplied to the inverting input terminal of the comparator 271, and the output voltage ■□, z (for example, 5
．． IV) is supplied. The output voltage of this comparator 271 is supplied to the base of a switching transistor 273. The collector of this switching transistor 273 is connected to the base of the constant current transistor 264, and the emitter is grounded. In such a configuration, when the charging voltage vb of the capacitor 240 exceeds the output voltage VIEFI of the constant voltage circuit 262, the charging prohibition circuit 270 turns off the constant current transistor 264, thereby shutting down the constant current charging circuit. 2
60 charging operation is prohibited. That is, until the charging voltage Vb of the capacitor 240 exceeds the output voltage VllEF2 of the constant voltage circuit 272, the output voltage L! of the comparator 271! It becomes a lore level. As a result, the switching transistor 273 is turned off, so the constant current transistor 264 performs a constant current charging operation. Conversely, when the charging voltage vb of the capacitor 240 exceeds the output voltage ■□8 of the constant voltage circuit 272, the output voltage of the comparator 271 becomes high level. As a result, the switching transistor 273 is turned on, so that the base potential of the constant 1 diverting transistor 264 becomes low level. As a result, the constant current transistor 264 is turned off, and the constant current charging operation is prohibited. Note that the comparator 271 has hysteresis characteristics. That is, the output voltage Vc of the comparator 271 is
As shown in FIG. 3, when charging the capacitor 240, when the charging voltage of the capacitor 240 exceeds the output voltage Vr*f2 of the constant voltage circuit 272, it becomes high level. Conversely, when the capacitor 240 is discharged, this capacitor 2
Even if the charging voltage Vc of 40 becomes smaller by ■1°, it does not immediately become a low level, and when it becomes Vr*fl (for example, 4.9V), which is a predetermined voltage lower than this, it becomes a low level. becomes. This prevents the charging state and charging stop state from frequently repeating around the voltage ■□F2. In the above configuration, the operation will be explained. First, the constant current charging operation of the capacitor 240 will be explained. It is now assumed that the capacitor 240 is not charged with any electric charge. In this state, when the unit 200 is inserted into the backboard 400, the unit 200 is connected to the power supply unit 100. As a result, the capacitor 240 is charged with a constant current. That is, since the capacitor 240 is hardly charged, the charging voltage vb of the capacitor 240 becomes smaller than the output voltage V tart of the constant voltage circuit 272. As a result, the output voltage Vc of the comparator 271 becomes low level, so that the switching transistor 273 is turned off. As a result, the constant current transistor 264 is turned on, and the capacitor 240
Charging current flows through. At this time, since the base potential of the constant current transistor 264 is controlled based on the amount of collector current of the constant current transistor 264, the capacitor 264
0 is charged with a constant current. The charging voltage vb of the capacitor 240 is determined by the constant voltage circuit 272.
When the output voltage VC of the comparator 271 becomes higher than the output voltage V rafM, the output voltage VC of the comparator 271 becomes high level. As a result, the switching transistor 273 is turned on. As a result, constant current transistor 264 is turned off, and charging of capacitor 240 is prohibited. After this, the charging voltage vb of the capacitor 240 becomes V r*
Unless the voltage becomes smaller than f3, the output voltage Vc of the comparator 271 does not go to low level, so no charging operation is performed. Next, referring to FIG.
The operation shown in FIG. 2 will be described when the unit 200, in which the capacitor 240 has almost no charge while connected to the Unisoto 100, is connected to the source unit 100. Note that FIG. 4 shows the output til of the power supply unit 1 (11) and the capacitor 240, similar to the previous FIGS. 9 and 11.
3 is a signal waveform diagram showing the charging voltage vb of the circuit 310 and the t source voltage Va of the circuit 310. FIG. Before connecting the unit 200 to the TFL unit 100, the output current of the power supply unit 1 (11) is
Flows only to 00. This current I is a constant current, and the fourth
In figure (a), 1. It is shown as closed. When unit 200 is connected to Ha unit loO,
The output current ■ of the power supply unit 1 (11) is the unit 7) 2 (
This is the total current of the current flowing through the unit 10 and the current flowing through the unit 300. Here, the current flowing through unit 7 200 consists of the charging current of capacitor 240 and the current flowing through other parts of unit 200 than capacitor 240. The former is a constant current, and the latter is also a constant current, as described above. Therefore, in this case as well, the output current I of the NR unit 1 (11) is also a constant current. This current I is shown in Fig. 4(a).
In this case, it is shown as ■2. In this case, if the charging current of the capacitor 240 is set appropriately, as shown in FIG.
) output current I! can be prevented from exceeding the rated current 11-. As a result, as shown in FIG. 4(b), when the unit 200 is connected to the power supply unit 100, the NB voltage Va of the circuit 3]0 of the unit 3 (11) can be prevented from decreasing temporarily. Therefore, malfunction of the circuit 310 can be prevented. Furthermore, by charging the capacitor 240 with a constant current, the capacitor 240
The charging time CT can be significantly shortened compared to the conventional configuration shown in FIG. The charging of the capacitor 240 and the voltage vb are controlled by the constant voltage circuit 272.
The output voltage Vll! F! When this capacitor 2 reaches
40 charging operations are prohibited. Therefore, the output current I of the ii source unit 1 (11) is the total current of the current flowing through the unit 300 and the current flowing through the unit 200 excluding the charging current of the capacitor 240. In FIG. 4(a), this current is shown as I3. As detailed above, in this embodiment, the capacitor 240
Since I decided to charge it with a constant current, the
), it is possible to prevent the circuit 310 already connected to the power supply unit 100 from malfunctioning, and the charging time CT of the capacitor 240 can be shortened. Further, in this embodiment, the constant current transistor 2640 uses the comparator 271 having hysteresis characteristics.
Since on/off is controlled, the voltage V ref
It is possible to prevent charging and charging prohibition from being repeated frequently near t. Furthermore, in this embodiment, since the DC/DC converter 250 compensates for the voltage drop of the diode 230, the charging voltage vb of the capacitor 240 is set to a voltage within the rated voltage range of the integrated circuit (hereinafter referred to as IC). can be secured. That is, the output voltage of the power supply unit 1 (11) is normally 5V, but when it is supplied to the circuit 210, it is stepped down by about 0.7V by the diode -230, so the output voltage is about 4.3V. Become. On the other hand, when the circuit 210 is composed of an IC, its rated voltage range is 4.5 to 5.5. Therefore, if no precautions are taken, the voltage drop may cause the circuit 210 to malfunction. On the other hand, in this embodiment, the DC/DC converter 250
is provided to compensate for the voltage drop of the diode 230, so malfunctions of the circuit 210 can be prevented. FIG. 5 is a circuit diagram showing the configuration of a second embodiment of the invention. In FIG. 5, the same parts as in FIG. 2 are given the same reference numerals. In the previous embodiment, N is used as the constant current transistor 264.
The case where a PN transistor is used has been explained. In contrast, this embodiment uses a PNP transistor. In accordance with this, the collector of the switching transistor 273 is connected to the emitter of the constant current transistor 264, and the emitter is connected to the base. According to such a configuration, the charging voltage vb of the capacitor 240 is equal to the output voltage (■) of the constant voltage circuit 272. When the switching transistor 273 turns on after exceeding art, the potential difference between the emitter and the base of the constant current transistor 264 becomes approximately O■, so this transistor 264 turns off. This prohibits the charging operation of capacitor 240. Even in this configuration, since the capacitor 240 can be charged with a constant current, the same effect as in the first embodiment can be obtained. FIG. 6 is a circuit diagram showing the configuration of a third embodiment of the present invention. In FIG. 6, the same parts as in FIG. 2 are given the same reference numerals. First thing first. In the second embodiment, the constant current charging circuit 2
A case has been described in which the charging current of the capacitor 240 is made constant by detecting the current on the input side of the capacitor 60. , : In contrast, this embodiment detects the current on the output side of the constant current charging circuit 260 to
Full of! It is designed to keep the current constant. Note that the illustrated constant current charging circuit 260 is similar to that shown in FIGS.
Unlike the constant current charging circuit 260 shown in the figure, the current detection resistor 2
65. Two operational amplifiers 266267, constant voltage circuit 26
Consists of 8. Here, one end of the current detection resistor 265 is connected to the emitter of the constant current transistor 264, and the other end is connected to one end of the capacitor 240. The inverting input terminal of the operational amplifier 266 is connected to the current detection resistor 2
The operational amplifier 26 is connected to one end of the current detection resistor 265, and the non-inverting input terminal is connected to the other end of the current detection resistor 265.
The output terminal of 6 is connected to the inverting input terminal of operational amplifier 267. An output terminal of a constant voltage circuit 268 is connected to a non-inverting input terminal of the operational amplifier 267. The output terminal of operational amplifier 267 is connected to the base of transistor 264. According to such a configuration, first, the current detection resistor 265
The operational amplifier 266 detects the voltage drop. Next, this detection output and constant current IF! 268 output voltage V
The operational amplifier 267 detects the voltage difference between the voltage and the raft. Finally, the base voltage of the constant current transistor 264 is controlled by this detection output. As a result, the transistor 26
4 emitter current is controlled. Therefore, capacitor 240 is charged with a constant current. Even in such a configuration, the same effects as in the previous embodiment can be obtained. In the above description, a case has been described in which the present invention is applied to a power back amplifier circuit of a communication device, but the present invention can also be applied to a power back amplifier circuit of an electronic device other than a communication device. Further, in the present invention, it goes without saying that the specific configurations of the constant current charging circuit 260 and the charging inhibiting circuit 270 can be modified in various ways without departing from the gist thereof. C Effects of the Invention] As detailed above, according to the invention, the power backup capacitor is charged with a constant current, so
When the power supply is connected, not only can malfunctions of circuits already connected to the power supply be prevented, but also the charging time of the capacitor can be shortened. 4,

[Brief explanation of Figure (12)] Figure 1 is a block diagram showing the basic configuration of this invention, Figure 2 is a circuit diagram showing the configuration of the first embodiment of this invention, and Figure 3. is a characteristic diagram for explaining the operation of FIG. 2, FIG. 4 is a diagram for explaining the operation of one embodiment of this invention, and FIG. 5 is a configuration of a second embodiment of this invention. FIG. 6 is a circuit diagram showing the configuration of the third embodiment of the present invention. FIG. 7 is a block diagram showing the implementation configuration of communication equipment. FIG. 8 is a conventional TX source backup 9 is a signal waveform diagram for explaining the operation of FIG. 8; FIG. 10 is a circuit diagram showing the configuration of another example of the conventional power backup circuit; FIG. 11 is a signal waveform diagram for explaining the operation of FIG. 10. In the figure, 11... Backup capacitor, 12... Constant current charging means, 13... Charging inhibiting means, 261.265... Current detection resistor, 262.268
... Constant voltage circuit, 263.266.267... Operational amplifier, 264...
- Constant current transistor. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (3)

[Claims] (1) A power backup capacitor (11), a constant current charging means (12) for charging this capacitor (11) with a constant current, and this constant current charging means (12)
11) is charged to a predetermined voltage, charging inhibiting means (13) for inhibiting the charging operation of the constant current charging means (12);
) A power backup circuit characterized by comprising: (2) The constant current charging means (12) is a constant current transistor (264) whose collector-emitter current path is inserted into the charging path of the capacitor (11).
and a current detecting means (261, 265) for detecting the current flowing through the constant current transistor (264), and a current detecting means (261, 265) for detecting the current flowing through the constant current transistor (264). base potential control means (262, 2) for controlling the base potential of the transistor (264) for
63, 266, 267, 268). 63, 266, 267, 268). The power backup circuit according to claim 1. (3) The charging inhibiting means (13) is configured to prevent the capacitor (11) from charging when the capacitor (11) is charged.
11) is charged to the first voltage (V_r_e_f_2), the charging operation of the constant current charging means (12) is prohibited, and when the capacitor (11) is discharged, this capacitor (11) is charged to the first voltage (V_r_e_f_2). voltage (V_r_e_f_2)
The power supply backup according to claim 1, characterized in that the power supply backup is configured to release the prohibition of the charging operation of the constant current charging means (12) when the power supply is discharged to a lower second voltage (V_r_e_f_1). circuit.