JPH0460273B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a power supply circuit for a fire receiver, etc.
In particular, the present invention relates to a switching circuit that can switch to a standby power source without momentary power interruption.

``Prior Art'' Conventionally, fire alarm receivers are required to have a backup power supply, so that even in the event of a power outage, power is supplied for a predetermined period of time or longer to enable monitoring. In recent years, microcomputers have come to be used in fire receivers due to the complexity of signal processing.
The switching circuit of the power supply device uses a non-stop circuit that does not generate noise. The switching circuit generally uses semiconductor switching elements such as power transistors. For example, Utility Model Application No. 57-161090.

``Problems to be Solved by the Invention'' When a semiconductor such as a power transistor is used in a power supply switching circuit, a large current generally flows through the semiconductor, so a large heat sink is required for this semiconductor. Therefore, when designing a power supply device, it is necessary to fully consider the increase in size of the device and the heat dissipation effect. Furthermore, if a spare battery is provided with a charging circuit, the charging voltage may become high when the battery is removed, which may adversely affect other circuits.

"Means for Solving the Problems" The power supply circuit for a fire receiver, etc. of the present invention has a backup power source consisting of a power supply device that supplies a predetermined DC voltage to a load based on a commercial power source, a backup battery, and a charging circuit. When the device and the commercial power supply are normally supplied, the load is supplied with power from the power supply unit, and when the commercial power supply is out of service, the load is supplied with power from the standby power supply unit. a relay switching circuit that switches the contacts, a cutoff circuit that cuts off the output of the standby power supply when an increase in charging voltage is detected when the spare battery is not connected, and a cutoff circuit that cuts off the output of the standby power supply when a power outage occurs and when the power is restored. The present invention is characterized by comprising a transistor switch circuit that connects the standby power supply device and the load only during a time period that includes the switching operation time of the contacts of the relay when the relay contacts are detected.

``Operation'' A heat sink is not required for the power transistor for switching the power supply, and spare batteries can be replaced while the power is turned on.

"Embodiment" Hereinafter, an embodiment of the power supply circuit for a fire receiver, etc. of the present invention will be described based on the drawings.

The power supply circuit of this invention uses commercial power supply (AC100V)
A power supply device such as a switching regulator SWR that generates a specified DC power from the resistor R1, 2, 8,
Zener diode Z1, diode D1,7,
A relay switching circuit consisting of a transistor Q1 and a relay RP, a transistor switch circuit consisting of a resistor R3-7, 9, 10, a diode D2-6, 8, 9, a capacitor C1, 2, a transistor Q2, 4, and a transformer T. , diode D12~1
5. Charging circuit consisting of resistor R12 and spare battery
SB, resistors R11, 13, 14, diode D
10, 11, a Zener diode Z2, a transistor Q3, and a cutoff circuit consisting of a relay RC. Note that the relay RP has a switching contact rp, and the relay RC has a normally closed contact rc. Terminals DP and DC are for power output, and a load (not shown) is connected between them. Terminals drawn out from the relay switching circuit and transistor switch circuit via diodes D17 and D16, respectively.
TS is for battery testing.

To explain the operation of a power supply circuit configured in this way, the switching regulator SWR normally receives a commercial power supply and outputs a stable, predetermined DC voltage (generally 24V DC for fire alarm systems). The Zener voltage of the Zener diode Z1 used is several volts lower than this predetermined voltage. Therefore, current flows through the circuit between the resistor R1, the Zener diode Z1, and the base and emitter of the transistor Q1, making the transistor Q1 conductive. The relay RP is energized by the collector current of the transistor Q1.
A switching contact rp of the relay RP is connected to the diode D18 side. Therefore, the power from the switching regulator SWR is output to the terminals DP and DC and supplied to the load.

The effective voltage on the secondary side of the transformer T, whose primary side is connected to the commercial power supply, is set higher than the voltage of the spare battery SB (same as the output voltage of the switching regulator SWR), and this AC voltage is connected to the diode D1.
Full-wave rectification is performed by 2 to 15, and the charging resistor R1
2 to the spare battery SB for charging. If the backup battery SB is connected normally, the voltage output from this backup power supply will not exceed a predetermined value. The Zener voltage of the Zener diode Z2 is set slightly higher than the voltage of the spare battery SB. For this reason, Zener diode Z
Since no current flows through transistor Q3, transistor Q3 is in a cutoff state, and relay RC is deenergized. The normally closed contact rc of relay RC is in the closed state.

When the spare battery SB is removed in this state, the charging voltage between the connection terminals of the spare battery SB becomes high because there is no load. Current flows through the circuit between the resistors R12 and 13, the Zener diode Z2, and the base and emitter of the transistor Q3, and the transistor Q3 becomes conductive, energizing the relay RC.
The normally closed contact rc is open to prevent charging voltage from being applied to other circuits. This charging voltage is set to an average value higher than the normal circuit voltage (predetermined voltage),
Furthermore, since it is a pulsating flow, its peak value is more than twice the circuit voltage. Therefore, if this charging voltage is applied to an external circuit or load, malfunction or element destruction may occur, which is extremely dangerous.
This isolation circuit prevents this from happening.

Next, we will explain the uninterrupted operation during power outage and recovery when the spare battery SB is normally connected.

If the commercial power supply fails, the charging circuit and switching regulator SWR will lose power. The output voltage of the switching regulator SWR decreases according to the discharge curve due to the internal smoothing capacitor. When this output voltage falls below the voltage determined by the Zener diode Z1, the transistor Q1 is turned off. Relay RP is released from the energized state and switching contact rp is switched to the standby power source side. On the other hand, at the moment when transistor Q1 is cut off, the remaining voltage of switching regulator SWR causes the charged battery of capacitor C1 to flow through resistors R3 and 4, capacitor C1, diode D4, and the base and emitter of transistor Q2. Make it conductive temporarily. And between the emitter and base of transistor Q4, resistor R
10. Current flows through the circuit between the diode D8 and the collector and emitter of the transistor Q2, and the transistor Q4 also becomes conductive temporarily. At this time, spare battery
The power of SB is supplied to the load between the emitter and collector of transistor Q4 and through diode D9. That is, power is supplied from the standby power source via transistor Q4 only when relay RP is switched.

Switching regulator when power is restored
Power is normally output from SWR and energizes relay RP. A switching operation is performed by the switching contact rp, and power is supplied to the load from the normal power supply device. Restoration momentary resistance R6,7, capacitor C
2. A charging current of the capacitor C2 flows between the diode D5 and the base and emitter of the transistor Q2, temporarily turning on the transistors Q2 and Q4. That is, power is supplied from the standby power source via transistor Q4 even when relay RP is switched during recovery. The time constant of the time constant circuit consisting of resistors R3, 4, capacitors C1 and R6, 7, and capacitor C2 is appropriately determined, and transistor Q4 is made conductive for a time set to be equal to or slightly longer than the switching time of relay RP. state, forming an uninterrupted circuit. Since current flows through transistor Q4 only for a short time, that is, during the time period that includes the switching operation time of contact RP of relay RP, it is sufficient to use a power transistor Q4 that generates almost no heat and has a rating equal to or higher than the power supply capacity. A heat sink is not required.

By dropping the terminal TS to zero potential by operating a switch, the uninterrupted circuit is forcibly switched and the load is applied from the spare battery SB (in some cases, a pseudo load is used).
Test the spare battery by supplying power to the battery and checking the circuit voltage with a voltmeter (not shown).

"Effects of the Invention" As explained above, the power supply circuit of the present invention constitutes an uninterrupted circuit by a relay switching circuit such as relay RP, and a transistor switch circuit consisting of transistor Q4, etc., which operates only during this switching. Therefore, it is not necessary to attach a heat sink to the power transistor Q4, which flows a large current for switching the power supply, making the design of the entire power supply device easy and miniaturization. Further, when power is supplied from the backup battery SB, the uninterrupted circuit only consumes power during switching, which is convenient for the backup power supply device. It also has excellent features such as it is safe to replace the spare battery SB while the load (fire receiver, etc.) is operating because the charging circuit is cut off from other circuits when necessary based on the operation of the cutoff circuit. .

[Brief explanation of drawings]

The drawing shows an embodiment of the power supply circuit of the present invention. SWR……Switching regulator, T……
Transformer, SB...Spare battery, RP, RC...Relay, rp...Switching contact, rc...Normally closed contact, R1~1
4...Resistance, D1-17...Diode, Z1,
2... Zener diode, Q1~4... Transistor, C1, 2... Capacitor, DP, DC,
TS...terminal.

Claims (1)

[Claims] 1. A power supply device that supplies a predetermined DC voltage to the load based on the commercial power supply, a backup power supply device consisting of a spare battery and a charging circuit, and when the commercial power supply is normally supplied, the load is connected to the power supply device. a relay switching circuit that switches the contacts of the relay so that power is supplied from the standby power supply unit, and the load is supplied with power from the standby power supply unit in the event of a power outage of the commercial power supply;
A cutoff circuit that cuts off the output of the backup power supply when detecting an increase in charging voltage when the spare battery is not connected, and a contact of the relay when detecting the occurrence of a power outage or recovery from a power outage of the commercial power supply. A power supply circuit for a fire receiver, etc., comprising a transistor switch circuit that connects the standby power supply device and the load only during a time period that includes the switching operation time.