JPH0230523B2 - DENGENSOCHINOSHUTSURYOKUIJOKENSHUTSUHOGOKAIRO - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to an output abnormality detection protection circuit for a power supply device, and in particular to a circuit that stably turns on and off the output voltage even when the input voltage is gradually increased or decreased. The present invention also relates to an output abnormality detection and protection circuit for a power supply device that can perform output abnormality detection and protection operations accurately.

(2) Background of the technology Generally, in DC-DC converters or constant voltage power supplies, output abnormalities are detected to prevent the internal circuits of the power supply from being destroyed due to short circuits in the load circuit to which output voltage is supplied. A detection protection circuit is provided. Such output abnormality detection protection circuits may malfunction due to differences in input voltage application conditions or other conditions such as when the power is turned on, and such malfunctions may cause the input circuit or output circuit to be erroneously shut down. In this case, the power cannot be turned on or off stably. Therefore,
It is necessary for the output abnormality detection protection circuit to operate properly and stably.

(3) Prior art and problems Conventionally, in the output abnormality detection protection circuit of the power supply device as described above, for example, an output voltage detection circuit is provided, and when the output voltage is detected to be below the minimum rated value, the protection circuit is activated. The input circuit or output circuit was cut off.

However, in the conventional type, if the input voltage supplied as the input power source rises rapidly as shown in FIG. However, if the input voltage does not rise in a short time as shown in Figure 1b, and therefore the rise time T is quite long and the rise time T is not specified to a constant value, the output There was an inconvenience that the abnormality detection protection circuit malfunctioned. That is,
When a so-called gradually increasing input voltage is applied as shown in Figure 1b, the output voltage does not rise rapidly after the input voltage application starts, so the output voltage detection circuit detects that the output voltage is lower than the minimum rated value. It is detected that the output voltage is low, and the output abnormality detection protection circuit operates to cut off the input circuit or the output circuit. Therefore, it becomes impossible to turn on the power supply device in response to a gradually increasing input voltage. Such a gradual increase occurs, for example, when the input voltage is supplied by a motor generator (MG) and the motor generator starts after the power outage is restored.

(4) Purpose of the Invention In view of the problems with the conventional circuits described above, the purpose of the present invention is to provide an output abnormality detection protection circuit for a power supply device in which the input voltage rises above the minimum rated value necessary for the normal operation of the power supply device. Based on the idea that even if the output voltage remains below the minimum rated value even after a predetermined period of time has elapsed, the output is considered to be abnormal and the protection circuit is activated. The purpose of the present invention is to stably turn on/off an output voltage without causing malfunction, and to properly perform an output abnormality detection and protection operation.

(5) Structure of the Invention According to the present invention, in an output abnormality detection protection circuit of a power supply device having a voltage conversion section that converts an input voltage to a desired stabilized output voltage, the output voltage is detected and the minimum rated value is determined. an output voltage detection circuit that detects the input voltage and sends out an input detection signal after a predetermined time delay when the input voltage exceeds the minimum rated value; an abnormality detection control circuit that sends an on/off control signal for the output voltage to the voltage converter based on a signal, and sends a drive control signal based on an AND of the input detection signal and the output detection signal;
an input cutoff circuit that cuts off the input voltage according to the drive control signal, and sends out the output voltage from the voltage converter only when the input voltage rises above a minimum rated value, and There is provided an output abnormality detection and protection circuit for a power supply device, characterized in that when the input voltage is below a minimum rated value, the input cutoff circuit is operated by a control signal of the abnormality detection control circuit to cut off the input voltage.

(6) Embodiment of the invention An embodiment of the invention will be described below with reference to the drawings.
FIG. 2 shows a power supply device according to one embodiment of the present invention. In the same figure, 1 is a DC voltage converter.
- DC converter, 2 is an inrush current prevention circuit, 3 is an input cutoff circuit, 4 is an input voltage detection circuit, 5 is an output voltage detection circuit, and 6 is an abnormality detection control circuit. The inrush current prevention circuit 2 consists of a relay contact RL and an inrush current limiting resistor R1, and the input cutoff circuit 3 consists of a no-fuse breaker, including a trip coil TC and cutoff contacts CB1 and CB2.
Consisting of The input voltage detection circuit 4 includes a transistor T1 as a switch element, constant voltage diodes Z1 to Z3 for setting the minimum rated value of the input voltage connected to the base of the transistor T1, and a resistor R.
2, R3, a relay coil RL connected to the collector of the transistor T1 via a resistor R4, constant voltage diodes Z4 to Z6 for keeping the voltage applied to the relay coil RL constant, and a capacitor forming a delay circuit together with the resistor R4. C1 and a resistor R5 for discharging the capacitor C1. Note that this input voltage detection circuit 2 can be used in common with the drive control circuit for the relay contact RL of the inrush current prevention circuit 2 by simply adding a relay contact RL operated by the relay coil RL to the abnormality detection control circuit 6. be. The output voltage detection circuit 5 is a photocoupler as a switch element.
It includes a PC1, a constant voltage diode Z7 and a resistor R6 for setting the minimum rated value of the output voltage. Also,
The abnormality detection control circuit 6 includes a transistor T2 that drives the trip coil TC of the input cutoff circuit 3, a resistor R7 and a capacitor C3 that constitute a delay circuit, a smoothing capacitor C2, resistors R8 and R9 that constitute a base bias circuit of the transistor T2, and a constant voltage. It is composed of a diode Z8, a diode D1, and a relay contact rl. In addition, in Fig. 2, C4 is a power supply smoothing capacitor and D2
is a diode that connects the abnormality detection control circuit 6 and the input circuit of the power supply device. Further, one end of the relay contact rl of the abnormality detection control circuit 6 and the connection point Q on the cathode side of the diode D1 are connected to the DC-DC converter 1.
When the potential at the connection point Q becomes high level, the DC-DC converter 1 outputs an output, and when the potential at the connection point Q becomes low level, the output is stopped.

The operation of the circuit shown in FIG. 2 will be explained. Input voltage V _IN
is applied to the input voltage detection circuit 4 via the cutoff contacts CB1 and CB2 of the input cutoff circuit 3. For example, if the input voltage V _IN is gradually increased as shown in Figure 1b, then as long as the input voltage V _IN is lower than the minimum rated value, the transistor T1 is in the off state, and therefore the inrush current Relay contact of prevention circuit 2
rl is open, and the input current flows through resistor R1 to capacitor C4 and DC-DC converter 1.
This prevents inrush current. Also,
Since the relay contact RL in the abnormality detection control circuit 6 is closed, the connection point Q, the diode D1, and the resistor R
8 and the voltage regulator diode Z8 becomes a low level, the output voltage V _OUT from the DC-DC converter 1 remains in a state of not being sent out, and the transistor T2 is also cut off because it is not base biased. Therefore, the trip coil TC of the input cutoff circuit 3 is not driven and the cutoff contacts CB1 and CB2 are in a closed state.

Next, when the input voltage V _IN rises above the minimum rated value set by the voltage regulator diodes Z1 to Z3 of the input voltage detection circuit 4, the transistor T1
turns on and relay coil RL is driven, but
Since a delay circuit is provided using the time constant of resistor R4 and capacitor C1, relay coil RL
operates after a predetermined time delay. relay coil RL
As a result of the operation, each relay contact RL is switched, the resistor R1 of the inrush current prevention circuit 2 is short-circuited, the inrush current limit state is released, and the abnormality detection control circuit 6 is
Since the relay contact rl of is opened, the _potential of the connection point Q is as follows:
It becomes high level through R8 and diode D1, and output voltage V _OUT from DC-DC converter 1 is sent out. In this case, there is no abnormality such as a short circuit in the load circuit to which the output voltage V _OUT is supplied, and the output voltage
When V _OUT rises above the minimum rated value set by the constant voltage diode Z7 etc. of the output voltage detection circuit 5, the light emitting diode in the photocoupler PC1 emits light and the phototransistor is turned on. Therefore, the potential at the connection point P in the abnormality detection control circuit 6 is lowered to a low level via the phototransistor and the resistor R3 having a relatively small resistance value. Therefore, the transistor T2 in the abnormality detection control circuit 6 is always in the cut-off state,
The input cutoff circuit 3 does not cut off the input circuit.

Furthermore, since a delay circuit is added to the base bias circuit of the transistor T2 of the abnormality detection control circuit 6 using the time constant of the resistor R7 and the capacitor C3, the output voltage detection circuit is disabled for a predetermined period of time immediately after the relay contact RL is opened. 5 detection signal is not accepted. The delay time due to this time constant is determined by the output voltage V _OUT determined by the circuit component constants of DC-DC converter 1.
is set longer than the rise time of .

In addition, a resistor R4 and a capacitor C added to the relay coil RL of the input voltage detection circuit 4 mentioned above are also added.
The delay circuit with a time constant of 1 prevents the excessive inrush current flowing into the power supply smoothing capacitor C4 etc. immediately after the input voltage V _IN is applied by the current limiting resistor R1 of the inrush current prevention circuit 2 until charging is completed. , which determines the delay time for limiting the inrush current, and after a predetermined time delay, the relay coil RL operates and the inrush current limit is released. The same voltage as voltage V _IN is applied, and the DC-DC converter 1 is in a state where it can operate normally. Therefore, from this time the output voltage
Since the output abnormality detection state can be set by sending out V _OUT , the input voltage detection circuit 4 in the output abnormality detection and protection circuit can also be used as a rush current prevention circuit.

On the other hand, if the input voltage V _IN rises above the minimum rated value and each relay contact RL is switched, and the output voltage V _OUT is below the minimum rated value, the photocoupler of the output voltage detection circuit 5 Since the phototransistor of PC1 is not turned on, the connection point P in the abnormality detection control circuit 6 is not pulled down to a low level. Therefore resistor R7 and capacitor C3
The potential at the connection point P rises even after a predetermined time delay due to the time constant of
Current flows through the trip coil TC, and the breaking contact
CB1 and CB2 are opened, the input voltage V _IN is cut off, and the power supply device performs a protective operation.

Also, if the input voltage V _IN gradually decreases from a high level value above the minimum rated value, the input voltage V _IN
When the voltage decreases to a value below the minimum rated value, the transistor T1 of the input voltage detection circuit 4 is turned off, the current in the relay coil RL is cut off, and each relay contact RL is therefore switched. As a result, the relay contact rl in the abnormality detection control circuit 6 closes, the voltage at the connection point Q and the connection point P becomes a low level, the output is stopped, and the detection signal from the output voltage detection circuit 5 is not accepted.

(7) Effects of the Invention As described above, in the output abnormality detection circuit of the power supply device of the present invention, the detected value of the input voltage becomes equal to or higher than the minimum rated value, and the output voltage increases when the input conditions for the power supply device to operate normally are met. The protection condition is implemented by receiving the output abnormality detection signal only after a predetermined time delay that takes into account the rise time of the output voltage. In order to determine the output abnormality, the output abnormality detection protection circuit can perform extremely stable operations without malfunctioning, not only when the input power is normally turned on and off, but also when the input power is turned on and off gradually increasing and decreasing. Output abnormality detection protection operation can be performed accurately.

[Brief explanation of drawings]

FIGS. 1a and 1b are waveform diagrams showing conditions for applying input voltage in the power supply device according to the present invention,
FIG. 2 is an electrical circuit diagram showing a power supply device according to an embodiment of the present invention. 1...DC-DC converter, 2...Inrush current prevention circuit, 3...Input cutoff circuit, 4...Input voltage detection circuit, 5...Output voltage detection circuit, 6...Abnormality detection control circuit, R1, R2, R3, R4, R5, R
6, R7, R8, R9...Resistance, Z1, Z2, Z
3, Z4, Z5, Z6, Z7, Z8... Constant voltage diode, C1, C2, C3, C4... Capacitor, D1, D2... Diode, T1, T2...
Transistor, PC1...Photocoupler, RL...
Relay coil, RL...Relay contact, TC...Trip coil, CB1, CB2...Cut-off contact.

Claims (1)

[Scope of Claims] 1. In an output abnormality detection protection circuit for a power supply device having a voltage converter that converts an input voltage to a desired stabilized output voltage, when the output voltage is detected and exceeds a minimum rated value, an output voltage detection circuit that sends out an output detection signal; an input voltage detection circuit that detects the input voltage and sends out the input detection signal after a predetermined time delay when the input voltage exceeds a minimum rated value; and the voltage conversion according to the input detection signal. an abnormality detection control circuit that sends out an on/off control signal for the output voltage to the section, and sends out a drive control signal by ANDing the input detection signal and the output detection signal; an input cutoff circuit that cuts off the output voltage from the voltage conversion section only when the input voltage rises above the minimum rated value, and sends out the output voltage from the voltage conversion section when the output voltage is below the minimum rated value. An output abnormality detection and protection circuit for a power supply device, characterized in that the input cutoff circuit is operated by a control signal of an abnormality detection control circuit to cut off the input voltage.