JP3714091B2 - Semiconductor integrated circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor integrated circuit such as a power supply control IC, to which an output short-circuit detection function and a power-off function are added.
[0002]
[Prior art]
The power supply circuit used for portable devices and the like is a main circuit composed of an active element such as a power switching element and a passive element such as a capacitor and a coil, and a power supply control IC (integrated) for controlling and protecting the power switching element. Circuit).
[0003]
FIG. 4 is a circuit diagram showing an example of this power supply circuit. The power supply circuit 50 includes a booster circuit that outputs a voltage obtained by boosting the input voltage Vin using an n-channel MOSFET 61 and a step-down circuit that steps down and outputs the input voltage Vin using a p-channel MOSFET 62. These MOSFETs 61 and 62 are driven by a power supply control IC 51. The boosted output voltage is output from the output terminal 68, and the stepped-down output voltage is output from the output terminal 69. Each of the terminals 68 and 69 is connected to a load (not shown). The output voltage output from the output terminals 68 and 69 is detected by a detection circuit (comprising resistors R1, R2, R3, and R4), and the detected voltage is input to the input terminals 53 and 54 of the power supply control IC 51. To do. The detection voltage for detecting the boosted output voltage is the first detection voltage, the detection voltage for detecting the stepped-down output voltage is the second detection voltage, and the first and second detection voltages are input to the input terminals 53 and 54 of the power supply control IC 51. The first and second feedback voltages are set. The pulse width of the gate signal for driving the n-channel MOSFET 61 and the p-channel MOSFET 62 is controlled by the magnitude of these detection voltages, and a stable DC output voltage is output from the power supply circuit 50.
[0004]
FIG. 5 is a circuit diagram of the power supply control IC. The power control IC 51 includes an oscillator 72, a first error amplifier 73, a second error amplifier 74, a first comparator 75, a second comparator 76, a first AND circuit 77, a second AND circuit 78, a first buffer 79, and a second buffer 80. , A constant voltage circuit 71, an output short circuit detection circuit 81, and the like. The constant voltage circuit 71 is a power supply inside the IC that supplies a voltage to the oscillator 72, the error amplifiers 73 and 74, the comparators 75 and 76, and the like, which are blocks.
[0005]
The first feedback voltage is input to the minus of the first error amplifier 73 via the input terminal 53, the reference voltage is applied to the plus of the first error amplifier 73, the output signal of the first error amplifier 73, and the oscillator 72 The output triangular wave voltage is input to the plus of the first comparator 75, the output signal of the first error amplifier 73 is input to the output short circuit detection circuit 81 via the input terminal 82, the output signal of the first comparator 73, The output signal output from the output terminal 84 of the output short circuit detection circuit 81 is input to the first AND circuit 77 and the second AND circuit, the output signal of the first AND circuit is input to the buffer circuit 79, and the output signal of the buffer circuit 79 is 4 is transmitted to the output terminal 55, and the gate signal of the n-channel MOSFET 61 of FIG.
[0006]
On the other hand, the second feedback voltage is input to the second error amplifier 74 via the input terminal 54, and the transmission path of each signal is the same as described above. However, the second buffer circuit 80 at the final stage is an inverting circuit.
FIG. 6 is a configuration diagram of the output short circuit detection circuit. The output short circuit detection circuit 81 includes a third comparator 85 connected to the first error amplifier 73 of FIG. 5 via the input terminal 82, a fourth comparator 86 connected to the second error amplifier 74 and the input terminal 83 of FIG. And an OR circuit 87 to which the output signals of the comparators 85 and 86 are input, and a delay circuit 88 to which the output signal of the OR circuit 87 is input. The delay circuit 88 is a circuit that sends a signal after a predetermined time has passed from the OR circuit 87 as a reference, and is a counter circuit, a capacitor rechargeable circuit, a shift register circuit, or the like. A latch signal is output from the delay circuit 88 via a buffer circuit 89 constituted by a NOT circuit and an output terminal 84, and this latch signal is transmitted to the first and second AND circuits 77 and 78 of FIG. Next, the circuit operation will be described with reference to FIGS. 4, 5, and 6.
[0007]
When the voltage at the output terminal 68 decreases, the output voltage that is the output signal of the first error amplifier 73 increases. The pulse width of the output signal of the first comparator 75 to which this signal and the triangular wave voltage output from the oscillator 72 are input increases. The output signal having a wide pulse width is transmitted to the output terminal 55 via the first AND circuit 77 and the first buffer circuit 79, and is given to the gate of the n-channel MOSFET 61 in FIG. Since the conduction pulse width of the n-channel MOSFET 61 extends, the capacitor 63 is charged, the voltage at the output terminal 68 rises, the voltage drop at the output terminal 68 is compensated, and a constant voltage is supplied from the output terminal 68.
[0008]
For example, when the load connected to the output terminal 68 is short-circuited (in the case of an output short-circuit), the first detection voltage becomes zero voltage, and this first detection voltage is input to the first error amplifier 73, and the first error amplifier 73, an H level signal is input to the output short circuit detection circuit 81, an L level signal is output from the output short circuit detection circuit 81, and this signal is input to the first and second AND circuits 77 and 78. The first and second AND circuits 77 and 78 output L level signals. Therefore, the output voltage from the output terminal 55 becomes L level (0 V), the output voltage at the output terminal 56 becomes H level voltage, the n-channel MOSFET 61 and the p-channel MOSFET 64 in FIG. A load (not shown) to be connected is disconnected.
[0009]
FIG. 7 shows a circuit including a conventional power supply circuit, a power supply control auxiliary circuit, a power supply additional circuit, and a load. This circuit is different from the power supply circuit 50 shown in FIG. 4 in that a power supply additional circuit 90 including p-channel MOSFETs 91 and 92, n-channel MOSFETs 95 and 96, capacitors 93 and 94, a fifth comparator 97, and an OR circuit 98 is used. A circuit to which an auxiliary circuit 111 is added. The power supply circuit 90 has two systems corresponding to the output of the power supply circuit 50 being two outputs, and the loads connected to the input terminals 101 and 102 are also individual. Although one load 100 is shown in the figure, actually, individual loads are connected to the input terminals 101 and 102, respectively.
[0010]
As shown in FIG. 5, the output signal of the output short circuit detection circuit 81 of the power supply control IC 51 used here is not only the input signal of the first and second AND circuits 77 and 78 but also separated from the connection point 59. An output is also output from the output terminal 57 to the outside of the power supply control IC 51.
The power supply voltage is input to the negative of the power supply circuit 50 and the third comparator 97, and output signals output from the output terminal 68 and the output terminal 69 of the power supply circuit 50 are supplied to the sources of the p-channel MOSFETs 91 and 92 of the power supply additional circuit 90. The output from the drains of the p-channel MOSFETs 91 and 92 is input to the load 100. The output signal of the output short circuit detection circuit 81 of the power control IC 51 is input to the OR circuit 98 through the output terminal 70 together with the output signal of the third comparator 97. The output signal of the OR circuit 98 is an n-channel MOSFET 95, It is given to 96 gates.
[0011]
When the output is short-circuited, an H level signal is input from the output terminal 70. Therefore, even if the third comparator 97 outputs an H level signal or an L level signal, the output signal of the OR circuit 98 is at the H level. A high voltage is applied to the gates of the n-channel MOSFETs 95 and 96, and as a result, the input terminals 101 and 102 of the load 100 are grounded.
[0012]
On the other hand, when the power supply is cut off, the input voltage of the fifth comparator 97 falls below the reference voltage 99, so that the output signal of the fifth comparator 97 becomes H level. When this H level output signal is input to the OR circuit 98, the output signal from the output terminal 57 of the output short circuit detection circuit 81 (the output terminal 70 of the power supply circuit 50) does not depend on the H level or L level. The output becomes H level. Therefore, a high voltage is applied to the gates of the n-channel MOSFETs 95 and 96 to turn them on, an H level output signal of the fifth comparator 97 is applied to the gates of the p-channel MOSFETs 91 and 92, and the p-channel MOSFETs 91 and 92 are turned off. As a result, the charge of the capacitor is discharged, the input terminals 101 and 102 are grounded, and the voltage applied to the load becomes zero. Further, the load 100 is disconnected from the power supply circuit 50 regardless of the presence or absence of an output short circuit.
[0013]
As described above, in order to provide a function corresponding to the case where the power is cut off, the power control IC 51 mounted in the power circuit 50 is provided with the power control auxiliary circuit 111 as described above for power control. Apart from the IC, it is necessary to add it outside the power supply circuit 50.
[0014]
[Problems to be solved by the invention]
However, when the power control auxiliary circuit described above is added to the power control IC that constitutes the power circuit, the entire circuit becomes larger and the cost increases.
An object of the present invention is to solve the above-mentioned problems, and while suppressing an increase in chip area, it has a power-off function and an output short-circuit detection function, and a power supply capable of reducing the size and cost of a power circuit The object is to provide a semiconductor integrated circuit which is a control IC.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a power supply circuit to which a power supply voltage is input, a power supply additional circuit connected between the power supply circuit and a load, and when the power supply voltage is lower than a reference voltage , or the power supply circuit outputs The power supply additional circuit is configured to include a power supply control auxiliary circuit that outputs a signal for grounding the input of the load when the power supply additional circuit is disconnected from the load when the short circuit occurs.
[0016]
The power control assistance circuit, said to supply voltage positive terminal, a comparator the reference voltage is input to the negative terminal, an output short-circuit detection circuit, the output signal of the output signal and the output detection circuit of the comparator is input And the switching element constituting the power supply circuit may be controlled by an output signal of the OR circuit.
[0017]
The power supply additional circuit includes a p-channel MOSFET connected to the output and source of the power supply circuit, a drain connected to the drain of the p-channel MOSFET, one end connected to the ground, and one end connected to the drain of the capacitor. An n-channel MOSFET whose source is connected to the ground, the source of the p-channel MOSFET is the input side of the power supply circuit, and the drain of the n-channel MOSFET is the output side of the power supply circuit. When the voltage is equal to or lower than the reference voltage , or when the output is short-circuited, the p-channel MOSFET is turned off from the OR circuit, the n-channel MOSFET is turned on, the power supply circuit and the load are disconnected, and the load It may be configured to output a signal for grounding the input.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a semiconductor integrated circuit diagram of one embodiment of the present invention. This power supply control IC 1 includes a circuit for detecting power cut and output short circuit, a drive circuit for driving a switching element of a power supply additional circuit (not shown), an overcurrent protection circuit, an overvoltage protection circuit, an overheat protection circuit, and the like. .
[0019]
In this circuit, the comparator 2 to which the power supply voltage (VDD) is inputted to minus and the reference voltage is inputted to plus, the output short circuit detection circuit 81, the output signal of the comparator 2, and the output signal of the output short circuit detection circuit 81 are inputted. OR circuit 4 to be configured. A buffer circuit is incorporated in the output stage of the output short circuit detection circuit. This comparator 2 serves as a power-off detection circuit. In the figure, 3 is a reference voltage, 6 is a power supply input terminal to which a power supply voltage is inputted, 7 is an output terminal for outputting an output signal of the OR circuit 4, 11 is a circuit corresponding to the conventional power control auxiliary circuit 111, 82 , 83 are input terminals of the output short circuit detection circuit, and 84 is an output terminal of the output short circuit detection circuit.
[0020]
When the power is cut off, the output of the comparator 2 is output at the H level, and the output of the OR circuit 4 is at the H level regardless of whether the output is short-circuited. This H level signal is applied to a power supply additional circuit (not shown), the power supply circuit and the load are disconnected, and the input terminal of the load is grounded.
When the power supply is at a normal voltage, the output of the comparator 2 is L level, and only when the output is short-circuited, the output signal of the H level is given from the output short circuit detection circuit 81 to the OR circuit 4, and the output of the OR circuit 4 is Becomes H level. Of course, when the output is normal, it becomes L level.
[0021]
The area occupied by the comparator 2 and the OR circuit 4 in the semiconductor chip is several tenths of the area of the conventional power supply control IC 51 and is extremely small. Therefore, the chip area of the power control IC 1 of the present invention is almost the same as that of the conventional power control IC 51. In this way, an increase in the chip area of the power supply control IC is suppressed, power supply disconnection and output short circuit are detected, and a signal for disconnecting the power supply circuit from the load and grounding the load with the detection signal (H of the OR circuit 4) Level output signal) can be transmitted to the power supply additional circuit.
[0022]
FIG. 2 is a circuit diagram showing a power supply circuit, a power supply additional circuit, and a load on which the semiconductor integrated circuit of the present invention is mounted. The power supply circuit 21 is the same as that shown in FIG. 4 except for the power supply control IC 1. Further, the power control auxiliary circuit 111 provided outside the power circuit 50 in FIG. 7 is incorporated in the power control IC 1. This is the circuit 11 in the dotted line portion. The output short circuit detection circuit 81 of the power supply control IC 1 is the same as the conventional output short circuit detection circuit. This is a case where the power supply circuit 21 has two outputs, and different loads are connected to the load input terminals 34 and 35 connected to the output terminals 25 and 26.
[0023]
Next, circuit operation will be described. The power supply voltage VDD is input to the minus of the comparator 2 through the input terminal 24 of the power supply circuit 21 and the power supply input terminal 6 of the power supply control IC 1. When this voltage is higher than the reference voltage 3, it is a normal power supply voltage, and when it is low, it is determined as an abnormal power supply voltage. In the case of power off, this is an abnormal power supply voltage. In the case of a normal power supply voltage, the output signal of the comparator 2 is L level, and in the case of an abnormal power supply voltage such as power off, the output signal of the comparator 2 is H level. The output signal from the comparator 2 and the output signal from the output terminal 84 of the same output short circuit detection circuit 81 as in the conventional circuit are input to the OR circuit 4. In the case of power off or the like, since the H level output signal is input from the comparator 2 to the OR circuit 4, the output signal of the OR circuit 4 does not depend on the state of the output signal of the output short circuit detection circuit 82, that is, An H level signal is output from the output terminal 7 regardless of whether or not there is an output short circuit.
[0024]
On the other hand, when the output is short-circuited, the output signal of the output short-circuit detection circuit 82 is H level, and the output signal of the OR circuit 4 is H level even when the power supply voltage is normal.
When an H level signal is applied from the output terminal 7 of the OR circuit 4 to the gates of the p-channel MOSFETs 28 and 29 and the n-channel MOSFETs 32 and 33 via the output terminal 27 of the power supply circuit 21, the p-channel MOSFETs 28 and 29 are turned off. The n-channel MOSFETs 32 and 33 are turned on. Therefore, the power supply circuit 21 and the load 23 are disconnected by the power supply additional circuit 22 in the case of power supply disconnection and output short circuit. Further, by short-circuiting the n-channel MOSFETs 32 and 33, the input terminals 34 and 35 of the load 23 are short-circuited, and noise and floating potential are prevented from being applied to the load 23. Further, the electric charges of the capacitors 30 and 31 are discharged. Further, by turning on the n-channel MOSFETs 32 and 33, it is possible to prevent the power supply circuit 21 and the load 23 from being destroyed due to intrusion of a surge voltage or the like, and to operate the power supply circuit and the load safely.
[0025]
Note that the area occupied by the comparator 2 and the OR circuit 4 in the semiconductor chip is a few tenths of the area of the power control IC, and is extremely small. The chip area of the power control IC 1 is the same as that of the conventional power control IC 51. It is almost the same. The p-channel MOSFET may be replaced with a pnp transistor, and the n-channel MOSFET may be replaced with an npn transistor.
[0026]
Thus, by incorporating the power supply control auxiliary circuit 11 in the power supply control IC, the area of the power supply control IC can be suppressed, and a power supply control IC having a power-off detection and an output short-circuit detection can be obtained. Further, as described above, by incorporating the power supply control auxiliary circuit 11 in the power supply control IC 1, the number of components can be reduced as compared with the number of component parts combining the conventional power supply control auxiliary circuit 111 and the power supply circuit 50. The power supply circuit can be reduced in size and cost.
[0027]
FIGS. 3A and 3B show output forms of the OR circuit, FIG. 3A shows the direct method, FIG. 3B shows the n-channel MOSFET method, and FIG. 3C shows the p-channel MOSFET method. The output of the OR circuit 4 is obtained by connecting resistors 42 and 46, capacitors 43 and 47, and power supplies 44 and 48 to the drains of the n-channel MOSFET 42 and the p-channel MOSFET 45 as shown in FIGS. By delaying the signal for an arbitrary time, a signal for controlling the power supply additional circuit can be taken out from the output terminal 7 from the connection point between the resistors 42 and 46 and the capacitors 43 and 47. The area occupied by the chip of the n-channel MOSFET 41 and the p-channel MOSFET 45 is as small as one tenth of the short circuit detection circuit, and the area of the power supply control IC 1 is hardly increased.
[0028]
【The invention's effect】
According to the present invention, the power cut-off detection circuit is composed of one comparator, and the power control auxiliary circuit composed of this comparator and one OR circuit is incorporated in the power control IC, thereby increasing the chip area. It is possible to provide a power supply control IC that can detect power-off and output short-circuit while suppressing the above. Further, by mounting this power supply control IC on the power supply circuit, the number of parts of the power supply circuit including the power supply control auxiliary circuit can be reduced, and the power supply circuit can be reduced in size and cost.
[Brief description of the drawings]
FIG. 1 is a semiconductor integrated circuit diagram of an embodiment of the present invention. FIG. 2 is a circuit diagram showing a power supply circuit, a power supply additional circuit, and a load on which the semiconductor integrated circuit of the present invention is mounted. (A) is a direct method, (b) is an n-channel MOSFET method, and (c) is a p-channel MOSFET method. FIG. 4 is a circuit diagram showing an example of a conventional power supply circuit. 5 is a circuit diagram of a conventional power supply control IC. FIG. 6 is a block diagram of an output short circuit detection circuit. FIG. 7 is a circuit diagram including a conventional power supply circuit, a power supply control auxiliary circuit, a power supply additional circuit, and a load. Explanation of]
1 Power control IC
2 Comparator 3 Reference voltage 4 OR circuit 6, 24 Power input terminal 7, 25, 26, 27, 84 Output terminal 11 Power control auxiliary circuit 21 Power circuit 22 Power supply additional circuit 23 Load 28, 29, 45 p-channel MOSFET
30, 31, 43, 47 Capacitor 32, 33, 41 n-channel MOSFET
34, 35, 82, 83 Input terminals 42, 46 Resistors 44, 48 Power supply 81 Output short circuit detection circuit

Claims (1)

A power supply circuit to which a power supply voltage is input, a power supply additional circuit connected between the power supply circuit and the load, and when the power supply voltage is lower than a reference voltage or when the output of the power supply circuit is short-circuited, A power control auxiliary circuit that outputs a signal for separating the power supply circuit and the load and grounding the input of the load ;
The power supply control auxiliary circuit receives a comparator in which the power supply voltage is input to the negative terminal and the reference voltage is input to the positive terminal, an output short circuit detection circuit, an output signal of the comparator, and an output signal of the output detection circuit. An OR circuit, and controls a switching element constituting the power supply additional circuit by an output signal of the OR circuit,
The power supply circuit includes a p-channel MOSFET to which the output and source of the power supply circuit are connected, a drain and one end connected to the p-channel MOSFET, the other end connected to the ground, and one end and drain of the capacitor connected to each other. An n-channel MOSFET whose source is connected to the ground, the source of the p-channel MOSFET is the input side of the power supply circuit, and the drain of the n-channel MOSFET is the output side of the power supply circuit. When the voltage is equal to or lower than the reference voltage, or when the output is short-circuited, the p-channel MOSFET is turned off from the OR circuit, the n-channel MOSFET is turned on, the power supply circuit and the load are disconnected, and the load Outputs a signal for grounding the input of the semiconductor integrated circuit.

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