JP2000299631A - Device and method for controlling power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for controlling power supply with which a heat loss is suppressed, a load current is highly accurately detected and individual control for each load is enabled. SOLUTION: The temperature of a semiconductor switch (FET 102) is detected by a temperature detecting means (diodes D1-D4 and a differential amplifier 105), the load current is detected by a current detecting means (the ON resistance of the FET 102 and a differential amplifier 106) and on the basis of the temperature detected result, the level of the reference potential of a comparator for judging an over current is shifted by a driving control part 107. When this temperature corrected reference potential is exceeded, the FET 102 is controlled to OFF and an over current braking function in the control of power supply from a power source 101 to a load 103 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control device and a power supply control method, and more particularly to a power supply control device and a power supply control method. The present invention relates to a power supply control device and a power supply control method for controlling power supply to a power supply.

[0002]

2. Description of the Related Art As a conventional power supply control device (first conventional example) provided with a semiconductor switch, there is one as shown in FIG. 7, for example. The power supply control device of this conventional example is a device that selectively supplies power from a battery to each load such as a headlight used in an automobile and a drive motor of a power window, and controls power supply to each load. It is.

In FIG. 1, a power supply control device according to a first prior art includes a shunt resistor RS and a thermal FET in a path for supplying an output voltage VB of a power supply 101 to a load 103.
This is a configuration in which the drain-source of the transistor 102a is connected in series. Further, the power supply control device according to the conventional example includes a comparator 106a for detecting a current (load current) flowing through the shunt resistor RS, and a thermal FE in accordance with a drive control signal 151a and a detection current 153a detected by the comparator 106a.
And a driver 201a for driving the T102a.

Thermal FET 1 as a semiconductor switch
02a has a structure as shown in FIG. 9 in more detail. In FIG. 9, the thermal FET has a built-in resistor 12
5, a temperature sensor 121, a latch circuit 122, and an overheat cutoff FET 123. ZD1 is a Zener diode that bypasses an overvoltage applied to the gate (G) while maintaining the voltage between the gate (G) and the source (S) at 12 [V].

That is, the thermal FE used in the conventional example
In the case of T, when the temperature sensor 121 detects that the temperature of the FET 124 has risen to a specified temperature or more, the detection information to that effect is held in the latch circuit 122, and the overheat cutoff FET 123 as the gate cutoff circuit is turned on. Thus, an overheat cutoff function for forcibly turning off the FET 124 is provided.

The temperature sensor 121 is composed of four diodes connected in cascade.
It is arranged and formed near 124. Since the resistance value of each diode of the temperature sensor 121 decreases as the temperature of the thermal FET rises, when the gate potential of the FET Q51 falls to a potential that is set to the “L” level, the FET Q5
1 changes from the on state to the off state. Thereby, F
The gate potential of the ETQ 54 is pulled up to the potential of the gate control terminal (G) of the thermal FET, and the FET Q54 transitions from the off state to the on state, so that “1” is latched by the latch circuit 122. At this time, the output of the latch circuit 122 becomes “H” level, and the overheat shutoff FE
Since T123 transitions from the off state to the on state, the potential level of the true gate (TG) of the thermal FET becomes “L”.
Level, the thermal FET transitions from the on-state to the off-state, and overheating is interrupted.

[0007] The comparator 106a is an overcurrent detection circuit that detects a load current flowing through the shunt resistor RS and outputs a signal 153a indicating that the current is an overcurrent. That is, the drive circuit 201a outputs the drive control signal 151a and the signal 153 from the comparator 106a.
The driving of the thermal FET 102a is controlled by supplying a drive signal to the gate (G) of the thermal FET 102a via the resistor R5 and the internal resistor 125 on the basis of a.

In the comparator 106a, when the potential difference corresponding to the voltage drop due to the shunt resistor RS exceeds the judgment value (overcurrent cutoff value), an "H" level signal 153a is supplied to the drive circuit 201a. The drive circuit 201a supplies a drive signal for turning off the thermal FET 102a to the thermal FET 102a in accordance with the signal 153a. Thereafter, in the comparator 106a, when the load current decreases and the potential difference corresponding to the voltage drop due to the shunt resistor RS falls below the determination value (return current value), an "L" level signal 153a is supplied to the drive circuit 201a. At this time, in the drive circuit 201a, according to the drive control signal 151a,
For example, a drive signal for turning on the thermal FET 102a is continuously supplied to the thermal FET 102a.

As described above, the first conventional example has a thermal F
The configuration is such that the drive of the ET 102a is hard-controlled by the overcurrent detection of the comparator 106a.
Even if an overcurrent caused by a short-circuit failure or an incomplete short-circuit failure between the drain and source of the thermal FET 102a or the thermal FET 102a attempts to flow through the path, the drive circuit 201a controls the thermal FET 102a to be turned off to realize an overcurrent protection function. ing.

FIG. 8 is a block diagram of another conventional power supply control device (second conventional example). In the figure, a power supply control device of a second conventional example includes a shunt resistor R in a path for supplying an output voltage VB of a power supply 101 to a load 103.
This is a configuration in which S and the drain-source of the thermal FET 102b are connected in series. Further, the power supply control device of this conventional example includes a differential amplifier 106b for detecting a current (load current) flowing through the shunt resistor RS, and a thermal FET 102
b, a driver 201b for controlling the driving of
The microcomputer 1 includes, for example, a microcomputer (CPU) 110b for supplying a PWM (pulse width modulation) control signal to control the driver 201b while the switch 1 is in the ON state.

First, a thermal F as a semiconductor switch
The ET 102b has a configuration shown in FIG. 9 similarly to the first conventional example, and has an overheat cutoff function of forcibly turning off the thermal FET when the thermal FET rises to a specified temperature due to overcurrent or the like. Have. The driver 201b includes a source transistor and a sink transistor, and has a control signal 151 from the microcomputer 110b.
b, on / off control of the source transistor and the sink transistor based on the thermal FET 1
02b. The voltage Vp applied to the collector of the sink transistor is a voltage boosted by a charge pump (not shown).

The differential amplifier 106b detects a load current flowing through the shunt resistor RS, and converts the detection result into an A / D signal.
This is a current detection circuit supplied to the microcomputer 110b via the converter 112b. Further, the microcomputer 110b supplies a control signal 151b to the driver 201b according to the setting of the switch 111. The microcomputer 110b constantly monitors the detection result of the load current detected by the shunt resistor RS and the differential amplifier 106b. When the load current flowing through the shunt resistor RS exceeds a predetermined value, the load current becomes an overcurrent. Then, the supply of the control signal 151b is stopped, and the thermal FET 102b is turned off. In the second conventional example, as an additional function,
By monitoring the load current flowing through the shunt resistor RS, it is also possible to realize a disconnection detection function and a short detection function for the load and the electric wire.

[0013]

As described above, in the power supply control device of the first conventional example, double protection is provided by the overheat protection function and the overcurrent protection function of the semiconductor switch. However, regarding the protection of the load and the electric wire connecting the load and the power supply control device, a device configuration capable of uniformly protecting the load due to various load conditions cannot be provided. There is a problem that a different power supply control device is required. In order to be able to control individually under such various load conditions, and from the requirements of load and wire disconnection detection and short-circuit detection functions, individual control is performed for each load by monitoring the load current flowing through the shunt resistor. The possible second power supply control device of the second conventional example has been proposed. However, in the first and second conventional power supply control devices, the load current caused by the reduction of the on-resistance of the semiconductor switch is reduced. As a result, the heat loss of the shunt resistor for detecting the load current cannot be ignored.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems. By using the on-resistance of a semiconductor switch as load current detecting means, it is possible to provide a heat-supply control device without providing a separate current detecting resistor. The loss is suppressed, and the problem of the temperature dependence of the on-resistance of the semiconductor switch is solved by performing the temperature correction at the time of detecting the load current.
An object of the present invention is to provide a power supply control device and a power supply control method capable of realizing highly accurate detection of load current and individually controlling each load.

[0015]

In order to solve the above-mentioned object, a power supply control device and a power supply control method according to the present invention perform switching control in accordance with a control signal supplied to a control signal input terminal, and perform switching control from a power supply. A semiconductor switch that controls power supply to a load, a temperature detection unit that detects a temperature of the semiconductor switch, and a current detection unit that detects a current flowing through the semiconductor switch based on a voltage generated at an on-resistance of the semiconductor switch. And control means for correcting the detection result of the current detection means based on the detection result of the temperature detection means, and controlling the supply of the control signal based on the corrected detection current.

A power supply control device according to a second aspect of the present invention is the power supply control device according to the first aspect, wherein the control means includes:
It controls the supply of the control signal.

A power supply control device according to a third aspect of the present invention is the power supply control device according to the first or second aspect, wherein the detection result of the current detection means is corrected based on the detection result of the temperature detection means. And determining means for determining a connection state of the signal line in the load based on the corrected detection current.

According to a fourth aspect of the present invention, in the power supply control device according to the first, second, or third aspect, the control means or the determination means includes a detection result of the current detection means, And a comparing means for comparing with a reference value which changes according to the detection result of the temperature detecting means.

According to a fifth aspect of the present invention, there is provided a power supply control method for controlling switching of a semiconductor switch by a control signal supplied to a control signal input terminal to control power supply from a power supply to a load. A temperature detecting step of detecting a temperature of the semiconductor switch;
A current detection step of detecting a current flowing through the semiconductor switch based on a voltage generated at an on-resistance of the semiconductor switch; and correcting a detection result of the current detection step based on a detection result of the temperature detection step. And controlling the supply of the control signal based on the detected current.

According to a sixth aspect of the present invention, in the power supply control method according to the fifth aspect, the control step includes supplying the control signal based on a detection result of the temperature detection step. To control.

According to a seventh aspect of the present invention, in the power supply control method according to the fifth or sixth aspect, the detection result of the current detection step is corrected based on the detection result of the temperature detection step. And determining a connection state of the signal line in the load based on the corrected detection current.

Further, the power supply control method according to claim 8 is the power supply control method according to claim 5, 6 or 7, wherein the control step or the determination step includes:
A comparing step of comparing the detection result of the current detection step with a reference value that changes according to the detection result of the temperature detection step.

In the power supply control device according to the first aspect of the present invention and the power supply control method according to the fifth aspect, the temperature of the semiconductor switch is detected by the temperature detection means (temperature detection step), and the current detection means (current detection Step)
A current flowing through the semiconductor switch is detected based on a voltage generated at an on-resistance of the semiconductor switch, and a control unit (control step) detects the current based on a detection result of the temperature detection unit (temperature detection step). Is corrected, and based on the corrected detection current,
A control signal supplied to a semiconductor switch for controlling power supply from a power supply to a load is controlled.

As described above, since the on-resistance of the semiconductor switch is used as a means for detecting the load current, there is no need to provide a separate current detection resistor unlike the prior art, and the heat loss of the current supply control device is suppressed. can do. In addition, the on-resistance of the semiconductor switch has a high temperature dependency, so that a detection error due to a temperature drift poses a problem. However, since the current detection result is corrected based on the temperature detection result, the load current is detected with high accuracy. be able to. Furthermore, if the load current (corrected current detection result) is constantly monitored and the semiconductor switch is turned off in the event of overcurrent, an accurate overcurrent protection function can be realized, and the semiconductor switch due to overcurrent can be realized. Can be prevented, and the life of the semiconductor switch can be extended.

In the power supply control device according to the second aspect and the power supply control method according to the sixth aspect, the control means (control step) controls the control signal based on the detection result of the temperature detection means (temperature detection step). The supply is controlled. For example, if the temperature detection result exceeds a predetermined value, the semiconductor switch is turned off,
It is possible to realize an overheat interruption function, prevent the semiconductor switch from being thermally damaged due to overheating, and extend the thermal life.

In the power supply control device according to the third aspect and the power supply control method according to the seventh aspect, the judging means (judging step) uses the current detecting means based on the detection result of the temperature detecting means (temperature detecting step). The detection result of the (current detection step) is corrected, and the connection state of the signal line in the load is determined based on the corrected detection current.

This makes it possible to determine the connection state of the load and the signal line (electric wire) connecting the load and the power supply control device, for example, to detect a short circuit or a disconnection, and to determine the connection state according to the load condition. Thus, a power supply control device that can be individually controlled for each load can be realized.

Further, in the power supply control device according to the fourth aspect and the power supply control method according to the eighth aspect, in the control means (control step) or the determination means (judgment step), the current is controlled by the comparison means (comparison step). The detection result of the detection means (current detection step) is compared with a reference value which changes according to the detection result of the temperature detection means (temperature detection step) to control the supply of the control signal or the connection state of the signal line at the load. The judgment is made.

As described above, the reference value in the comparison means (comparison step) is changed (corrected) based on the temperature detection result in order to eliminate the detection error due to the temperature dependence of the on-resistance of the semiconductor switch. The load current can be detected with high accuracy. In particular, if the comparing means is configured by a comparator, the level of the reference voltage is shifted according to the result of the temperature detection. In this case, the load current can be detected at a higher speed, and the control or judgment can be performed at a high speed. it can. In addition, the temperature correction method for the current detection result includes a method of numerically converting the detected current value into a corrected current value using a memory or the like, or a method of calculating the corrected detected current value using a conversion formula. Various methods such as a method are conceivable.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a power supply control device and a power supply control method according to the present invention will be described.
The first embodiment and the second embodiment will be described in detail in this order with reference to FIGS. Here, FIG. 1 is a circuit configuration diagram of a power supply control device according to a first embodiment of the present invention,
FIG. 2 is a detailed circuit configuration diagram of the drive control unit in the first embodiment, FIG. 3 is a detailed circuit configuration diagram of a short-circuit detection unit, FIG. 4 is a detailed circuit configuration diagram of a disconnection detection unit, and FIG. FIG. 6 is a timing chart for explaining the operation of the power supply control device of FIG. 6, and FIG. 6 is a flowchart for explaining a power supply control method in the power supply control device of the second embodiment.

[First Embodiment] A power supply control device according to a first embodiment will be described with reference to FIG. 1. The power supply control device according to the present embodiment uses the output voltage VB of the power supply 101 to load 103 , A drain-source of the FET 102 (124) as a semiconductor switch is connected in series, and a block 104 for driving and controlling the FET 102, an A / D converter 112, a CPU 11
0, display unit 113, switch 111, and resistor R
1, R10. Although “R” and subsequent numbers are used for the resistors as reference symbols, the following description uses them as reference symbols and also indicates the resistance values of the resistors.

The power supply 101 is a battery or the like, and outputs an output voltage VB (for example, 12 [V]). The load 103 is
For example, it is a headlight, a drive motor for a power window, or the like, and functions when a user or the like turns on the switch 111.

The FET 10 as a semiconductor switch
2 has only the FET 124 and the temperature sensor, and the thermal FET 102a,
102b (see FIG. 9), a latch circuit and a gate cutoff circuit (an overheat cutoff FE) for realizing the overheat cutoff function.
T) is not provided.

The temperature sensor has four diodes D1 to D
4 are connected in cascade, and the temperature sensor is FET
It is arranged and formed near 124. For example, FET1
02 rises, the diode D1 of the temperature sensor
To D4 are reduced, the power supply potential VB is
The potential VT at the voltage dividing point where the voltage is divided by 1 and the resistance values of the diodes D1 to D4 decreases, and conversely, when the temperature of the FET 102 decreases, the potential VT increases, so that the potential VT functions as temperature information. .

The block 104 for controlling the driving of the FET 102 may be constituted by combining discrete components, or may be constituted by using an integrated ASIC. The drive control block 104 includes a differential amplifier 105 that amplifies a potential VT as temperature information,
4, a differential amplifier 106 for amplifying a voltage drop generated in the on-resistance between the drain and the source, a drive control unit 107 for driving the FET 102 based on a drive control signal 151 from the CPU, a load 103, and a connection to the load 103. A short-circuit detection unit 108 that detects whether a short-circuit failure has occurred in the power supply path, and a disconnection detection unit 109 that detects whether a disconnection failure has occurred in the load 103 and the power supply path to the load 103. This is a configuration including:

The temperature sensors (diodes D1 to D4) and the differential amplifier 105 correspond to the temperature detecting means described in the claims, and detect the internal temperature, the peripheral temperature, and the like as the temperature of the FET 124, and Outputs a temperature detection signal 152. The differential amplifier 105 is realized by an inverting differential amplifier, and converts the output signal after the inversion amplification into an absolute value so that the temperature detection signal 152
1 is a signal that changes in temperature opposite to the anode-side divided potential VT. That is, although the divided potential VT decreases in accordance with the temperature rise of the FET 102, the potential of the temperature detection signal 152 increases, and the divided potential VT increases in accordance with the temperature decrease of the FET 102, but the temperature detection signal 152 increases. Potential drops. Further, the on-resistance between the drain and the source of the FET 124 and the differential amplifier 106 correspond to current detection means,
A current flowing through a power supply path to the load 103, that is, a load current is detected, and a current detection signal 153 is output.

Next, the drive control unit 107 corresponding to the control means described in the claims will be described in detail with reference to FIG. In the figure, the drive control unit 107 includes a driver 201, comparators 202 and 203, an OR gate 204, a NOT gate 205, a transistor 206, and resistors R5, R6, R11 to R14.

The driver 201 includes a source transistor 2
11 and a sink transistor 212. The source transistor 211 and the sink transistor 212 are turned on / off based on a drive control signal 151 from the microcomputer 110.
The driving of the FET 102 is controlled by performing the off control. The voltage Vp applied to the collector of the sink transistor 211 is a voltage boosted by a charge pump (not shown).

The comparator 202 corresponds to comparison means in the control means, and compares the current detection signal 153 with a reference potential Iref obtained by dividing the divided potential VT on the anode side of the diode D1 by resistors R11 and R12. Outputs overcurrent status. That is, when the potential of the current detection signal 153 exceeds the reference potential Iref, the comparator 202 outputs the overcurrent status as valid (“H” level). Further, as described above, since the divided potential VT changes according to the temperature change of the FET 102, the reference potential Iref, which is determined to be an overcurrent, decreases when the temperature rises, and the reference potential Iref increases when the temperature falls. In the determination of the overcurrent, the detection error due to the temperature drift of the FET 102 is compensated. Here, the reference potential Iref determined to be an overcurrent is, for example, when the load 103 has a configuration of 5 W lamps × 3 lamps, the rated current of the 5 W lamp at 13.5 [V] is 0.37 [A]. If the overcurrent is 1.5 times or more of the rated load current, 0.37 ×
This is set as a potential corresponding to 3 × 1.5 = 1.67 [A].

The comparator 203 compares the temperature detection signal 152 and the power supply potential VB with the resistors R13 and R14.
The overheat status is output by comparing the reference potential Tref with the reference potential Tref. That is, when the potential of the temperature detection signal 152 exceeds the reference potential Tref, the comparator 203 outputs the overheat status as valid (“H” level).

In the OR gate 204, the comparator 20
The logical sum of the output (overcurrent status) of the comparator 2 and the output of the comparator 203 (overheat status) is obtained, and the inverted output of the logical sum output by the NOT gate 205 is supplied to the CPU 110 as a status signal 156. Also, OR
The output of the gate 204 is also supplied to the gate of the transistor 206, and it is determined that the load current is overcurrent (overcurrent status is valid) or that the load current is overheated (overheat status is valid). Is)
In order to forcibly turn off the FET 102 (off control), the transistor 206 is turned on and the drive control signal 151 to the driver 201 is lowered to “L” level. That is, the overcurrent cutoff function is provided by the comparator 202 and the transistor 206.
03 and the transistor 206 realize the overheat cutoff function.

Next, the short-circuit detecting section 108 corresponding to the determining means will be described in detail with reference to FIG. Referring to FIG.
Comprises a comparator 301 and resistors R15 and R16.

The comparator 301 corresponds to the comparing means in the judging means. The comparator 301 compares the current detection signal 153 with a reference potential obtained by dividing the divided voltage VT on the anode side of the diode D1 by the resistors R15 and R16. A short detection signal 157 indicating whether or not the short circuit 103 is in a short state (for example, the load current is 1.5 times or more of the rated current)
Output to PU110. That is, when the potential of the current detection signal 153 exceeds the reference potential, the comparator 301 outputs the short detection signal 157 as valid (“H” level). Also, as mentioned above,
Since the divided potential VT changes in accordance with the temperature change of the FET 102, the reference potential for determining a short-circuit state decreases when the temperature rises, and the reference potential increases when the temperature decreases. The detection error due to the drift will be compensated. Here, the reference potential for judging the short-circuit state is, for example, when the load 103 has a configuration of 5 W lamps × 3 lamps, the rated current of the 5 W lamp at 13.5 [V] is 0.37 [A]. Then, 0.37x
This is set as a potential corresponding to 3 × 1.5 = 1.67 [A].

Next, the disconnection detecting unit 109 corresponding to the determining means will be described in detail with reference to FIG. In the drawing, the disconnection detection unit 109 includes a comparator 401 and resistors R17 and R18.

The comparator 401 corresponds to the comparing means in the judging means, and the current detecting signal 153 and the temperature detecting signal 15
2 is compared with a reference potential obtained by dividing the potential of resistors R17 and R18, and a disconnection detection signal 158 indicating whether or not the load 103 is disconnected is output to the CPU 110. That is, when the potential of the current detection signal 153 falls below the reference potential, the comparator 401
Outputs the disconnection detection signal 158 as valid (“H” level). Further, as described above, since the potential of the temperature detection signal 152 changes according to the temperature change of the FET 102, the reference potential for determining that the wire is disconnected is increased when the temperature is increased, and the reference potential is decreased when the temperature is decreased. In the determination of the disconnection state, the detection error due to the temperature drift of the FET 102 is compensated.

Here, the reference potential for judging the disconnection state is, for example, the rated current of the 5 W lamp at 13.5 [V] of 0.37 [V] when the load 103 has a configuration of 5 W lamps × 3 lamps. A], the threshold may be set to 0.9 [A] in the case of one lamp disconnection. Assuming that the variation of the lamp and the detection accuracy are ± 10 [%], the minimum load current when the three lamps are turned on is 0.37 × 3 × 0.9 = 1.0.
[A], and the maximum load current when one lamp is disconnected is 0.
Since 37 × 2 × 1.1 = 0.81 [A], the threshold value 0.9 [A] has a margin of about ± 0.1 [A]. The threshold value is similarly calculated for each of the disconnection of two lamps and the disconnection of three lamps, and the disconnection detecting unit 109 for the reference potential corresponding to these threshold values is configured in parallel. It is also possible to discriminate what kind of disconnection state such as disconnection of one lamp, disconnection of two lamps or disconnection of three lamps.

Further, the CPU 110 includes a switch 111
Is a microcomputer that supplies, for example, a PWM (pulse width modulation) control signal 151 in order to control the drive control unit 107 when is in the ON state. Also, the CPU 110 includes temperature data obtained by digitally converting the temperature detection signal 152 from the differential amplifier 105, current data obtained by digitally converting the current detection signal 153 from the differential amplifier 106, a status signal 156 from the drive control unit 107, and a short circuit. Detector 1
08 and a disconnection detection signal 158 from the disconnection detection unit 109, respectively. The current data is temperature-corrected by the temperature data at that time. As the temperature correction method, a method of numerically converting the detected current value into a corrected current value using a correction table such as a memory, or using the temperature data as a parameter. Various methods are conceivable, such as a method of calculating a corrected detected current value using a conversion formula.

That is, the CPU 110 always performs A / D
While monitoring the temperature data from the converter 112 and the corrected current data, when the status signal 156 from the drive control unit 107 becomes valid, the display unit 113 displays “overcurrent cutoff” or “overheat cutoff”. And a short detection signal 15 from the short detection unit 108 is output.
When the disconnection detection signal 158 from the disconnection detection unit 109 becomes valid, the display unit 113 displays “Load short-circuit state” when the display unit 113 becomes valid. , 2 or 3 lights) disconnection condition
Is displayed.

Next, a power supply control method according to the present embodiment will be described with reference to FIG. 5 based on the circuit configuration of the power supply control device according to the present embodiment described above. In FIG. 5, (a) is a drive control signal 151, (b) is a current detection signal 153, (c) is a temperature detection signal 152, and (d) is FE.
It is a voltage waveform diagram of each T drive signal 154, (e)
Indicates status information of overcurrent, and (f) indicates status information of overheating.

First, as shown in FIG. 5A, when the drive control signal is at the "H" level and the FET 102 is controlled to be on, at time T1, the current detection signal 153 changes to the reference potential Iref for overcurrent determination. (Fig. 5 (b)
5), the output of the comparator 202 of the drive control unit 107 (overcurrent status: see FIG. 5 (e)) becomes valid, and the overcurrent cutoff function is activated.
02 is forcibly dropped to the “L” level (see FIG. 5D), and the FET 102 is turned off.

Thereafter, at time T2, after the load current decreases and the FET 102 returns to the ON control, at time T3, the temperature detection signal 152 changes to the reference potential Tre for judging overheating.
f (see FIG. 5C), the drive control unit 10
7 (overheating status: FIG. 5)
(F) becomes effective, the overheat cutoff function operates, and the drive signal 154 of the FET 102 is forcibly dropped to the “L” level (see FIG. 5D), and the FET 102 is turned off.
102 is off-controlled.

Further, after the temperature decreases at time T4 and the FET 102 returns to the on-state control, at time T5
When the current detection signal 153 exceeds the reference potential (Iref-ΔIref) for overcurrent determination (see FIG. 5B), the output of the comparator 202 of the drive control unit 107 (overcurrent status: FIG. e) becomes effective and the overcurrent cutoff function operates, and the FET 10
The second drive signal 154 is forcibly dropped to the "L" level (see FIG. 5D), and the FET 102 is turned off. That is, at time T5, the temperature of the FET 102 rises, and the reference potential for determining overcurrent becomes a potential lower by ΔIref than Iref at normal temperature.
The temperature is corrected and an accurate overcurrent cutoff function is realized.

As described above, in the power supply control device and the power supply control method of the present embodiment, the temperature of the semiconductor switch (FET 102) is detected by the temperature detecting means (diodes D1 to D4 and the differential amplifier 105). The load current is detected by current detection means (ON resistance of the FET 102 and the differential amplifier 106), and the drive control unit 107 shifts the level of the reference potential of the comparator 202 for judging the overcurrent based on the temperature detection result.
FET when the temperature-corrected reference potential is exceeded
The power supply 102 is turned off to control the power supply from the power supply 101 to the load 103.

As described above, since the on-resistance of the FET 102 is used as a means for detecting the load current, there is no need to provide a separate current detection resistor unlike the related art, and the heat loss of the current supply control device is suppressed. be able to. Further, the on-resistance of the FET 102 has a high temperature dependency, so that a detection error due to a temperature drift poses a problem. However, since the current detection result is corrected based on the temperature detection result, it is necessary to detect the load current with high accuracy. Can be.
Further, when an overcurrent is detected based on the temperature-corrected current detection result, the FET 102 is turned off, so that an accurate overcurrent protection function can be realized, and damage to the FET 102 due to the overcurrent can be prevented. , F
The life of the ET 102 can be extended. Further, in the present embodiment, when the temperature detection result exceeds the reference potential for judging overheating in the comparator 203 of the drive control unit 107, the FET 102 is controlled to be off, so that an overheating cutoff function can be realized, and the overheating cutoff function can be realized. FET1
02 can be prevented from being thermally damaged, and the thermal life can be extended.

In the present embodiment, the short detection unit 1
At 08, the comparator 3 for determining the short-circuit state
01 is shifted based on the temperature detection result, and when the reference potential exceeds the temperature-corrected reference potential, it is determined that the load is in a short circuit state. Further, in the disconnection detecting section 109, the reference potential of the comparator 401 for determining the disconnection state is level-shifted based on the temperature detection result, and when the temperature falls below the temperature-corrected reference potential, it is determined that the load is in the disconnection state. As described above, the connection state of the signal line in the load is determined by comparing with the temperature-corrected reference potential. Therefore, for the load and the signal line (electric wire) connecting the load and the power supply control device, Short detection and disconnection detection can be performed accurately.

[Second Embodiment] Next, a power supply control device and a power supply control method according to a second embodiment will be described. The configuration of the power supply control device of the present embodiment is the same as the configuration of the power supply control device of the first embodiment (see FIG. 1).
Has a configuration in which the drive control unit 107 includes only the driver 201 and the resistors R5 and R6, and the short detection unit 108 and the disconnection detection unit 109 are removed.

That is, in the power supply control device of the second embodiment, the CPU 110 supplies the temperature data obtained by digitally converting the temperature detection signal 152 from the differential amplifier 105 by the A / D converter 112 and the The current data obtained by digitally converting the current detection signal 153 by the A / D converter 112 are taken in, and the current data is temperature-corrected with the temperature data by software processing in the CPU 110 to obtain corrected current data. A drive control signal 151 is supplied to the driver 201 based on the current data to perform switching control of the FET 102, and the power supply 10
1 controls the power supply to the load 103.

In the CPU 110, the current data is temperature-corrected by the temperature data at that time. As a temperature correction method, there are a method of numerically converting the detected current value into a corrected current value using a correction table such as a memory, and the like. Various methods are conceivable, such as a method of calculating a corrected detected current value using a conversion equation using temperature data as a parameter.

Next, a power supply control method in the power supply control device of the present embodiment will be described with reference to a flowchart shown in FIG. First, in step S601, FE
It is determined whether or not the on-control is being performed in T102, and if the on-control is being performed, the following processing is performed. Note that the processing of step S601 may be omitted, and the following processing may be always performed.

In step S602, it is determined whether or not the FET 102 is overheated based on the temperature data.
If the temperature data is overheated beyond the specified value,
In step S611, the FET 102 is turned off, and in step S612, an overheat cutoff display is performed via the display unit 113. Here, the off control of the FET 102 is performed by stopping the output of the drive control signal 151. If it is determined in step S602 that the temperature data is equal to or less than the predetermined value and is not in an overheated state, the process proceeds to step S603, in which a threshold used in the comparison determination of current data performed below is corrected based on the temperature data.

In step S604, it is determined whether the current data has exceeded an overcurrent threshold. If the current data exceeds the overcurrent threshold and overcurrent flows,
In step S621, the FET 102 is turned off, and in step S622, an overcurrent cutoff display is performed via the display unit 113.

If it is determined in step S604 that the current data is equal to or less than the overcurrent threshold and is not in an overcurrent state, the flow advances to step S605 to determine whether the current data is equal to or less than the disconnection threshold. . If the current data is lower than the disconnection threshold value, it is determined that a disconnection state has occurred and step S
Proceeding to 631, a disconnection state display is performed via the display unit 113.

If it is determined in step S605 that the current data exceeds the disconnection threshold value and is not in a disconnected state, the flow advances to step S606 to perform a normal operation display via the display unit 113. In the overcurrent determination sequence, it may be determined whether or not the load 103 is in a short-circuit state. If the load 103 is in a short-circuit state, a short-circuit state display may be performed. Further, the sequence for determining a disconnection may be a sequence for determining a plurality of types of disconnection states, as in the disconnection detection unit 109 of the first embodiment.

As described above, in the power supply control device and the power supply control method according to the present embodiment, the corrected current data is constantly monitored by the CPU 110, and the FET 102 is turned off in the case of overcurrent, so that accurate An overcurrent protection function can be realized, and the FET 102
Can be prevented, and the life of the FET 102 can be extended. Further, when the temperature data exceeds a predetermined value, the FET 102 is turned off, so that an overheat cutoff function can be realized.
2 can be prevented from being thermally damaged, and the thermal life can be extended. Further, since the connection state of the signal line in the load 103 is determined based on the corrected current data, short-circuit detection, disconnection detection, and the like can be performed, and power supply that can be individually controlled for each load according to load conditions can be performed. A control device can be realized.

Note that, depending on the type of the load 103, high speed is required for the off control of the FET 102 at the time of overcurrent or overheating. In such a case, the drive control unit is replaced with the drive control unit of the first embodiment. As a configuration equivalent to (see FIG. 2), the overcurrent cutoff function and the overheat cutoff function may be performed by hardware control, and the short-circuit detection and the disconnection detection may be performed by software processing.

As a modification, the FET 102 as a semiconductor switch in the first and second embodiments is
Is the thermal FE with the overheat shut-off function used in the conventional example.
T (see FIG. 9) can be used instead. For example, the temperature sensor 121 and the resistor R5 in FIG.
If the potential of the second voltage dividing point N1 is used as the potential VT in the first embodiment, it is possible to realize the same circuit configuration.

In the first and second embodiments and the modifications, the FET 124 and the transistor 20
6, Overheat cutoff FET 123 and FETs Q51 to Q5
Although an n-channel type is used as 3, the circuit configuration of the power supply control device according to the present invention is not limited to this, and a p-channel type may be used. However, a circuit change due to the inversion of the gate potential for performing on / off control of each switching element to the “L” / “H” level is required. Further, instead of FET 124, I
It is also possible to use GBT (Insulated Gate Bipolar Transistor).

[0068]

As described above, according to the power supply control device and the power supply control method of the present invention, the temperature of the semiconductor switch is detected by the temperature detecting means (temperature detecting step), and the current detecting means (current detecting step) is detected. )
A current flowing through the semiconductor switch is detected based on a voltage generated at an on-resistance of the semiconductor switch, and a control unit (control step) detects the current based on a detection result of the temperature detection unit (temperature detection step). Is corrected, and based on the corrected detection current,
Since the control signal supplied to the semiconductor switch for controlling the power supply from the power supply to the load is controlled and the on-resistance of the semiconductor switch is used as a means for detecting the load current, the current supply control device Heat loss can be suppressed. Further, the problem of the detection error due to the temperature dependence of the on-resistance of the semiconductor switch is solved by correcting the current detection result based on the temperature detection result, and the load current can be detected with high accuracy. Further, if the load current is constantly monitored and the semiconductor switch is turned off in the event of an overcurrent, an accurate overcurrent protection function can be realized, and damage to the semiconductor switch due to the overcurrent can be prevented. At the same time, the life of the semiconductor switch can be extended.

Further, according to the present invention, in the control means (control step), the temperature detection means (temperature detection step)
The control signal supply is controlled based on the detection result.For example, if the semiconductor switch is turned off when the temperature detection result exceeds a predetermined value, the overheat cutoff function can be realized, and the overheating can be realized. Can prevent the semiconductor switch from being thermally damaged, and can prolong the thermal life.

Further, according to the present invention, the detection result of the current detecting means (current detecting step) is corrected by the determining means (determining step) based on the detection result of the temperature detecting means (temperature detecting step). Since the connection state of the signal line in the load was determined based on the later detected current,
With respect to the load and the signal line (electric wire) connecting the load and the power supply control device, it is possible to determine a connection state, for example, to detect a short circuit or a disconnection, and to individually determine each load according to the load condition. A controllable power supply control device can be realized.

Further, according to the present invention, in the control means (control step) or the judgment means (judgment step),
The comparison means (comparison step) compares the detection result of the current detection means (current detection step) with a reference value that changes according to the detection result of the temperature detection means (temperature detection step), and controls the supply of the control signal. Alternatively, in order to eliminate the detection error due to the temperature dependence of the on-resistance of the semiconductor switch, the reference value in the comparison means (comparison step) is changed based on the temperature detection result in order to determine the connection state of the signal line in the load. Correction), the load current can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply control device according to a first embodiment of the present invention.

FIG. 2 is a detailed circuit configuration diagram of a drive control unit according to the first embodiment.

FIG. 3 is a detailed circuit configuration diagram of a short detection unit according to the first embodiment.

FIG. 4 is a detailed circuit configuration diagram of a disconnection detection unit according to the first embodiment.

FIG. 5 is a timing chart illustrating an operation of the power supply control device according to the first embodiment.

FIG. 6 is a flowchart illustrating a power supply control method in the power supply control device according to the second embodiment.

FIG. 7 is a circuit configuration diagram of a power supply control device of a first conventional example.

FIG. 8 is a circuit configuration diagram of a power supply control device of a second conventional example.

FIG. 9 is a detailed circuit configuration diagram of a thermal FET.

[Explanation of symbols]

Reference Signs List 101 power supply 102, 102a, 102b FET (semiconductor switch) 103 load 104 drive control block 105 differential amplifier (temperature detection means) 106 differential amplifier (current detection means) 107 drive control section (control section) 108 short detection section (judgment) Means) 109 Disconnection detecting unit (determining unit) 110, 110b CPU 111 Switch 112, 112b A / D converter 113 Display unit 124 FET R1 to R55 Resistance D1 to D4, 121 Diode (temperature sensor; temperature detecting unit) 151 Drive control Signal 152 Temperature detection signal 153 Current detection signal 154 FET drive signal 156 Status signal 157 Short circuit detection signal 158 Disconnection detection signal VB Power supply potential VT Divided potential 201, 201a, 201b Drivers 202, 203, 301, 401 Regulator (comparison means) 204 OR gate 205 NOT gate 206 transistor 211 source transistor 212 sink transistor 106a comparator 106b differential amplifier resistance RS Q51~Q53,123 FET ZD1 Zener diode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H03K 17/687 H03K 17/687 A F-term (Reference) 5G004 AA04 AB02 BA04 DA04 DC03 DC04 DC12 DC14 EA01 5G053 AA01 AA14 BA01 BA04 BA06 CA01 DA01 DA03 EA01 EC03 FA05 5J055 AX12 AX15 AX32. FX13 FX18 FX21 FX22 FX32 FX33 FX38 GX01 GX02 GX03 GX04

Claims (8)

[Claims] A semiconductor switch that is switched and controlled in accordance with a control signal supplied to a control signal input terminal and controls power supply from a power supply to a load; a temperature detection unit that detects a temperature of the semiconductor switch; Current detection means for detecting a current flowing through the semiconductor switch based on a voltage generated in the on-resistance of the semiconductor switch; and correcting the detection result of the current detection means based on the detection result of the temperature detection means. Control means for controlling the supply of the control signal based on the detected current. 2. The power supply control device according to claim 1, wherein the control unit controls the supply of the control signal based on a detection result of the temperature detection unit. 3. A determination means for correcting a detection result of the current detection means based on a detection result of the temperature detection means and determining a connection state of a signal line in the load based on the corrected detection current. The power supply control device according to claim 1 or 2, wherein: 4. The control unit or the determination unit includes a comparison unit that compares a detection result of the current detection unit with a reference value that changes according to a detection result of the temperature detection unit. The power supply control device according to claim 1, 2 or 3. 5. A power supply control method for controlling switching of a semiconductor switch by a control signal supplied to a control signal input terminal to control power supply from a power supply to a load, wherein a temperature of the semiconductor switch is detected. Step, a current detection step of detecting a current flowing through the semiconductor switch based on a voltage generated at an on-resistance of the semiconductor switch, and correcting a detection result of the current detection step based on a detection result of the temperature detection step, Controlling a supply of the control signal based on the corrected detection current. 6. The power supply control method according to claim 5, wherein the control step controls the supply of the control signal based on a detection result of the temperature detection step. 7. A determination step of correcting a detection result of the current detection step based on a detection result of the temperature detection step and determining a connection state of a signal line in the load based on the corrected detection current. The power supply control method according to claim 5 or 6, wherein: 8. The control step or the determination step includes a comparison step of comparing a detection result of the current detection step with a reference value that changes according to a detection result of the temperature detection step. Claim 5,
8. The power supply control method according to 6 or 7.