Patent Application
20150130476
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-236038, filed on Nov. 14, 2013, the entire contents of which are incorporated herein by reference.
The present invention relates to a direct-current regulator and a DC-DC converter.
The direct-current regulator has a high-side switching element between one of input terminals (high potential side) and an output terminal and a low-side switching element between the other input terminal (low potential side) and the output terminal, and carries out voltage conversion. In the direct-current regulator, a measurement circuit configured to control the switching elements and to measure temperatures, voltages, etc., is incorporated. The measurement circuit generates an anomaly detection signal when detecting anomalies of the switching elements or input/output voltage and current and sends the anomaly detection signal to the control circuit. The control circuit having received this signal performs control so as to prevent the anomalous state from continuing by stopping the operation of the regulator itself.
When the switching element enters a closed state due to the occurrence of a short circuit caused by a failure of the switching element or due to a failure of the control circuit, a large current flows between the input voltage terminal and the ground. At this time, if the measurement circuit inside the element operates and the anomaly can be detected and the operation of the direct-current regulator can be stopped, the failure does not affect the external periphery, and therefore, there is no problem.
However, in cases where failures are as (1) to (3) below, it is not possible to stop the operation of the direct-current regulator in which a failure has occurred, and therefore, the failure will affect the peripheral circuits.
(1) In the case where the input voltage and the control circuit power source short-circuit within the gate driver and the voltage for the measurement circuit and the control circuit is lost.
(2) In the case where heat is produced rapidly at the time of the failure of the switching element and the failure of the control circuit is induced before the direct-current regulator starts the operation when an anomaly occurs and the operation is no longer possible.
(3) In the case where the control unit fails and the two switching elements enter the closed state at the same time during the operation of the direct-current regulator.
The change in the characteristics with the passage of time of the switching element is not monitored previously, and therefore, in many cases, an anomaly is detected after the switching element has entered the broken state.
According to a first aspect, a direct-current regulator includes: a fuse, a high-side switch, and a low-side switch connected in series between a high potential side input voltage terminal and a low potential side input voltage terminal; and a control unit configured to control the high-side switch and the low-side switch, wherein the fuse is formed on a silicon substrate on which the high-side switch is formed.
According to a second aspect, a DC-DC converter includes: a regulator including: a fuse, a high-side switch, and a low-side switch connected in series between a high potential side input voltage terminal and a low potential side input voltage terminal, the fuse being formed on a silicon substrate on which the high-side switch is formed; and a control unit configured to control the high-side switch and the low-side switch; and a low-pass filter connected between a connection node of a high-side switch and a low-side switch and a low potential side input voltage terminal.
According to a third aspect, an anomaly monitoring method of a direct-current regulator, the direct-current regulator including: a fuse, a high-side switch, and a low-side switch connected in series between a high potential side input voltage terminal and a low potential side input voltage terminal, the fuse being formed on a silicon substrate on which the high-side switch is formed; and a control unit configured to control the high-side switch and the low-side switch, the method includes: controlling the high-side switch and the low-side switch so that both the switches are not brought into conduction simultaneously but brought into conduction alternately; and detecting an input current by using the fuse when controlling the high-side switch and the low-side switch so as to be brought out of conduction, and determining that the high-side switch has deteriorated when the detected input current exceeds a normal value.
According to a fourth aspect, an anomaly monitoring method of a direct-current regulator, the direct-current regulator including: a fuse, a high-side switch, and a low-side switch connected in series between a high potential side input voltage terminal and a low potential side input voltage terminal, the fuse being formed on a silicon substrate on which the high-side switch is formed; and a control unit configured to control the high-side switch and the low-side switch, the method includes: controlling the high-side switch and the low-side switch so that both the switches are not brought into conduction simultaneously but brought into conduction alternately; and detecting an input current by using the fuse after bringing the high-side switch into conduction in the state where the low-side switch is brought out of conduction, and determining that the low-side switch has deteriorated when the detected input current exceeds a normal value.
The object and advantages of the embodiments will be realized and attained by means of the elements and combination particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention.
Before explaining an embodiment, a general direct-current regulator will be explained.
The electric circuit has a direct-current regulator 11, a low-pass filter 12, and a load 13. The direct-current regulator 11 converts the voltage of power from a direct-current power source having an input voltage Vin (e.g., 12 V) and outputs the voltage to the low-pass filter 12. As illustrated in
The direct-current regulator 11 has a high-side switch S1, a low-side switch S2, an oscillation circuit 31, a control circuit 32, a reference voltage source 33, a PWM comparator 34, a gate driver 35, a gate driver 36, and an error detection circuit 37. The direct-current regulator 11 further has an input voltage monitoring unit 21, an input current monitoring resistor 22, an input current monitoring unit 23, a temperature monitoring sensor 24, and an output voltage and current monitoring unit 25.
The high-side switch S1 and the low-side switch S2 are formed by, for example, a switching element, such as a power MOSFET. The oscillation circuit (OSC) 31 outputs a sawtooth waveform signal. The PWM comparator 34 compares the sawtooth waveform signal and a reference voltage Vref output from the reference voltage source 33 and outputs a signal to turn on S1 to the gate driver 35 in the case where Vref is exceeded. The PWM comparator 34 outputs a signal to appropriately turn on S2 during the period of time during which S1 is off to the gate driver 36. This drive signal is called a PWM (Pulse Width Modulation) signal. The gate driver 35 and the gate driver 36 drive S1 and S2 so that they do not turn on at the same time in accordance with the PWM signal. Due to this, the output pulse string is supplied from the direct-current regulator 11 to the low-pass filter 12 and the capacitor C of the low-pass filter 12 is charged. As illustrated in
In the direct-current regulator in
The control circuit 32 is formed by, for example, the CMOS logic and connected to an external CPU via a command/status bus. The control circuit 32 receives the input voltage anomaly signal, the input current anomaly signal, the temperature anomaly signal, and the output anomaly signal and controls the reference voltage source 33 and the oscillation circuit 31 in accordance with the command from the outside. The control unit 32 outputs the control state to the command/status bus and at the same time, outputs an anomaly alarm signal to the outside at the time of occurrence of an anomaly. Although not illustrated schematically, it is possible for the control unit 32 to bring S1 and S2 into the off state by controlling the gate drivers 35 and 36 via the PWM comparator 34 or without interposing the PWM comparator 34. Upon receipt of the above-described anomaly detection signal, the control unit 32 performs control so as to prevent the anomalous state from continuing by stopping the operation of the direct-current regulator 11 itself by controlling the operation of S1 and S2 in accordance with the signal.
The input current monitoring unit 23 has an operational amplifier 41, a comparator 42, a current detection reference voltage source Vrefi, and two resistors forming an amplifier circuit. The two resistors and the operational amplifier 41 form an amplifier circuit that amplifies the voltage across both ends of the input current monitoring resistor 22 and outputs a voltage value IV1. The comparator 42 compares the voltage value IV1 output from the amplifier circuit with the current detection reference voltage Vrefi and in the case where Vrefi is exceeded, outputs an input current anomaly signal that turns the output on (logic value 1). The output form of the comparator 42 is an open-collector or open-drain configuration and the input current anomaly signal is input to the inverter of the control unit 32 and taken in by the control unit 32.
The control unit 32 performs processing to stop the direct-current regulator 11 when an anomaly occurs in accordance with the change in the logic value of the input current anomaly signal that is taken in and at the same time, outputs an anomaly alarm signal to the outside. The host circuit, such as an external CPU, recognizes the occurrence of an anomaly alarm by an interrupt etc. and determines the state of the direct-current regulator 11 from the status and issues a command to cut off the direct-current regulator 11 or to restart to the direct-current regulator 11. In a general direct-current regulator, the monitoring unit (measurement unit) and the circuits related to control and drive operate on the power source voltage, such as 5 V, 3 V, or 1 V, different from the input voltage and supplied to the normal logic circuit, etc.
Other monitoring units also have similar circuit configurations, but they do not relate to the embodiment directly, and therefore, explanation is omitted.
When a short circuit occurs due to the failure of the switching elements S1 and S2 or when the switching elements S1 and S2 enter the closed state due to the failure of the control circuit 32 in the direct-current regulator 11 illustrated in
However, in the case where a failure that leads to states (1) to (3) below has occurred, the operation to stop the direct-current regulator when an anomaly occurs is not performed, and therefore, the failure affects the peripheral circuits.
(1) In the case where the input voltage and the control circuit power source short-circuit within the gate driver 35 illustrated in
(2) In the case where heat is produced rapidly at the time of the failure of the switching elements S1 and S2 and the failure of the control unit 32 is induced before the direct-current regulator starts the operation when an anomaly occurs and the operation is no longer possible.
(3) In the case where a failure occurs in the control unit 32 during the operation of the direct-current regulator and a drive signal that simultaneously brings the switching elements S1, S2 into the closed state is generated.
In the three cases above, the stop operation when an anomaly occurs is not performed and the state is brought about where the operation does not stop even if the stop operation is performed, and therefore, the failure affects the peripheral circuits, resulting in a serious failure.
Further, in a general direct-current regulator, as described above, the measurement circuit configured to measure the input/output voltage and current, the temperatures of the switching elements S1 and S2, etc., is incorporated, but the change in the characteristics of the switching element with the passage of time is not monitored. The switching element gradually deteriorates and breaks at a certain point of time, but the change in the characteristics with the passage of time is not monitored, and therefore, an anomaly is detected after the switching element enters the broken state as a result. If it is possible to detect the deterioration of the switching element in advance, it is possible to take measures against the occurrence of an anomaly before the switching element enters the broken state.
According to the embodiment, a direct-current regulator is implemented, which has the function to physically prevent a failure from affecting peripheral circuits when an anomaly occurs and at the same time, which detects the internal anomalous state and prevents the failure from affecting the peripheral circuits before an anomaly occurs by stopping the operation of the regulator in accordance with the detection of the anomaly.
Consequently, the direct-current regulator of the embodiment is of the synchronous rectification type and has the function to prevent a PCB and peripheral circuit elements from being broken (burned) when an overcurrent flows through the PCB and the peripheral circuit elements mounting the regulator due to the deterioration of an internal power conversion switching element.
The electric circuit has the direct-current regulator 11, the low-pass filter 12, and the load 13 as that illustrated in
The direct-current regulator 11 has the high-side switch S1, the low-side switch S2, the oscillation circuit 31, the control circuit 32, the reference voltage source 33, the PWM comparator 34, the gate driver 35, the gate driver 36, and the error detection circuit 37. The direct-current regulator 11 further has the input voltage monitoring unit 21, the input current monitoring unit 23, the temperature monitoring sensor 24, the output voltage and current monitoring unit 25, and a fuse F1. As above, the direct-current regulator 11 of the embodiment differs from the direct-current regulator in
First of all, the direct-current regulator 11 of the embodiment prevents the failure from affecting the peripheral circuits by detecting an anomalous state at an early stage and stopping the operation. However, as measures when an anomaly occurs in the control circuit, etc., but it is not possible to stop the operation of the direct-current regulator upon detection of the anomalous state, the electric fuse F1 is arranged inside the direct-current regulator to stop the operation and thus the failure is physically prevented from affecting the peripheral circuits. However, if the melting time of the fuse is long, the possibility that the failure affects the peripheral circuits before the fuse melts is raised, and therefore, it is desirable to reduce the melting time of the fuse. In the embodiment, the fuse F1 is used for input current monitoring.
As illustrated in
The switching element part 54A includes a plurality of transistor regions 54 and in each transistor region 54, a MOSFET is formed. In the plurality of formed MOSFETs, the drains are connected to the second terminal part 53, the sources are connected to the third terminal part 55, and the gates are connected in common and connected to the gate driver 35 through a path not illustrated schematically. The connection in this case is made by a via in accordance with necessity. Over the plurality of MOSFETs formed in the switching element part 54A and the wires, a protective film is formed and further, over the protective film, a sealing material is provided in common with the fuse element part.
The input current monitoring unit 23 detects an input current by detecting the voltage across the first terminal part 51 and the second terminal part 53.
The fuse F1 illustrated in
As illustrated in
It is possible to represent the fuse F1 in the modified example as described above as a form in which resistors are connected as illustrated in
As illustrated in
Further, depending on the use of the electric circuit that uses the direct-current regulator of the present embodiment, the magnitude of the load connected to the direct-current regulator differs and depending on the magnitude of the load, the input current of the regulator differs. Due to this, a direct-current regulator capable of accepting input currents in a wide range is demanded. Consequently, by making variable the current capacity dealt with by the fuse F1 of the direct-current regulator 11, it is possible to extend the application range of the direct-current regulator.
The fuse F1 and the switching element S1 in
It is possible to vary the current capacity of the fuse F1 in
Further, the fuse in the modified example illustrated in
This control portion has a command register 61, a fuse connection register 62, a default fuse connection register 63, a NOR gate 64, a setting value switch and hold circuit (FF) 65, a data switcher 66, a NOR gate 67, and a decoder 68.
The command register 61 receives a command of the fuse setting value from an external CPU, etc., via a command/status bus and outputs a setting reset signal while performing the setting operation as well as outputting a setting value to the fuse connection register 62. The fuse connection register 62 receives and holds the fuse setting value from the command register 61.
The default fuse connection register 63 stores the default value of the fuse setting value determined in advance in the state where the fuse setting value is not specified yet, such as at the time of activation of the direct-current regulator. The default value is set by the value of the pin corresponding to two bits (0 or 1 of the logic value) of the direct-current regulator package for default value setting.
The NOR gate 64 receives the reset signal when the power of the direct-current regulator is turned on (Pon) and the reset signal from the command register 61. The NOR gate 64 resets the setting value switch and hold circuit (FF) 65 when one of the reset signals is active and brings the FF 65 into the set state when both reset signals are inactive.
The setting value switch and hold circuit (FF) 65 changes so as to output a selection signal “0” at the time of the reset and to output a selection signal “1” when fuse setting instructions, which are input from the outside, are input after the setting.
The data switcher 66 receives the fuse setting value from the command register 61 and the default fuse setting value from the default fuse connection register 63. The data switcher 66 selects and holds the default setting value when the selection signal is “0” and holds the fuse setting value received by the command register 61 when the selection signal is “1”.
Normally, the NOR gate 67 brings (enables) the decoder 68 into the operation state, but when the control unit, to be described later, generates an anomaly alarm signal or an anomalous current detection signal generated in the alarm detection processing, the NOR gate 67 outputs a signal to bring the decoder 68 into the non-operation state.
The decoder 67 decodes the setting value output from the data switcher 66 or the default setting value and controls the turning on/off of the fuse connection switches 58A to 58C.
When the power is turned on, a power source voltage Vcc of the whole including the regulator is input and the control circuit 2 enters the state capable of operation, the control portion in
After that, whether an anomaly has occurred is monitored during the operation and if an anomaly is recognized and the anomalous state is determined, the switches set in the connection state of the fuse connection switches 58A to 58C are turned off. In this case, the output voltage Vout of the direct-current regulator drops to the value in the off state (normally, 0 V). In the case where an anomaly is recognized, but it is observed that the anomalous state has disappeared after that, the fuse connection switches 58A to 58C are returned to the set connection state. In this case, Vout returns to the voltage in the on state.
The direct-current regulator of the embodiment further monitors the deterioration of the characteristics of the MOSFET used in the switching element. The characteristics of the MOSFET used in the switching element may sometimes deteriorate with the passage of time depending on the operation environment or due to the defect in the process of the MOSFET. If the change in the absolute resistance of the MOSFET is monitored inside the direct-current regulator, it is possible to detect and determine how the characteristics of the MOSFET have deteriorated, and therefore, it is possible to prevent a failure so serious that the fuse melts from occurring by stopping the operation of the direct-current regulator.
The control circuit 32 of the direct-current regulator of the embodiment has the configuration similar to that of the circuit in
As illustrated in
The F1 current determination unit 70 determines insulating properties of S1 and S2 and the penetrating current from the input current when a predetermined drive signal is applied to the gates of S1 and S2.
To the gates of S1 and S2, a gate signal illustrated schematically is applied. S1 and S2 alternately turn on and off so that both do not enter the on state (conduction state) at the same time. Consequently, after S2 enters the off state (insulated state), S1 enters the on state and remains in the on state for a predetermined period of time. Then, after S1 enters the off state, S2 enters the on state. Here, the time from when S2 enters the off state to when S1 enters the on state is referred to as a dead time.
The F1 current determination unit 70 takes the current flowing from the input terminal to S1 (plus current) to be a deterioration determination signal and the current in the opposite direction, i.e., flowing from S1 to the input terminal (minus current) to be a penetrating current determination signal and manages both currents.
A current waveform 1 indicates the change in the deterioration determination signal in accordance with the change in the gate signal in the case where S1 and S2 are normal. The current during the dead time during which S1 and S2 are off is zero and when S1 turns on, the current increases and when S1 turns off, the current becomes zero.
A current waveform 2 indicates the change in the deterioration determination signal in the case where S1 has deteriorated into the state where insulation is not achieved even if S1 turns off and S2 is normal. A current flows also during the dead time because S1 does not achieve perfect insulation. If this current becomes large, it is determined that S1 has deteriorated.
A current waveform 3 indicates the change in the deterioration determination signal in the case where S2 has deteriorated into the state where insulation is not achieved even if S2 turns off and S1 is normal. In the state where S2 is off and S1 is on, the current increases as in the current waveform 1 in the normal state, but in this case, the current is increased by the amount corresponding to the leaked current of S2, and therefore, the value of the current is large from the beginning as illustrated schematically. Consequently, in the case where the current when a short time elapses after S1 turns on is larger than the current in the current waveform 1 by a certain amount or more, it is determined that S1 has deteriorated.
A current waveform 4 indicates the case where both S1 and S2 have deteriorated and the waveform is a combination of the waveforms 2 and 3.
A current waveform 5 indicates the penetrating current determination signal. In the normal state, a current never flows in the backward direction, i.e., from S1 to the input terminal and the penetrating current determination signal is zero. However, if an anomaly occurs, in which the voltage (output voltage) Vout at the output terminal of the direct-current regulator becomes larger than the voltage (input voltage) Vdd at the input terminal due to some causes, a backflow of the current occurs through a parasitic diode of S1 and the penetrating current determination signal is no longer zero. Consequently, if the penetrating current determination signal becomes equal to or more than a predetermined value during the dead time during which S1 is off, it is determined that the state is anomalous.
The above is the anomalous current monitoring processing that uses the fuse F1 in the control circuit.
At step S11, power is turned on (power on).
At step S12, the interior of the direct-current regulator is initialized as explained in
At step S13, the operation of the direct-current regulator is started as explained in
At step S14, deterioration of S1 is determined. In this determination, if the deterioration determination signal during the dead time is equal to or less than the normal value, S1 is determined to be normal and if it is larger than the normal value, S1 is determined to be anomalous. In the case where S1 is determined to be anomalous, a counter of the number of times of S1 anomaly is incremented by 1 and in the case where S1 determined to be normal, the counter of the number of times of S1 anomaly is cleared.
At step S15, deterioration of S2 is determined. In this determination, if the deterioration determination signal when a predetermined time elapses after S1 turns on in
At step S16, whether or not the penetrating current exists is determined. In this determination, if the penetrating current determination signal during the dead time is equal to or less than a permitted value (absolute value is equal to or less than a predetermined value), it is determined that the state is normal and if it is larger than the permitted value, it is determined that the state is anomalous. In the case where the state is determined to be anomalous, a counter of number of times of penetrating current anomaly is incremented by 1 and in the case where the state is determined to be normal, the counter of the number of times of penetrating current anomaly is cleared.
At step S17, whether the count value of one of the counter of the number of times of S1 anomaly, the counter of the number of times of S2 anomaly, and the counter of the number of times of penetrating current anomaly described above exceeds a number of times of stop. In the case where the number of times of stop is exceeded, the procedure proceeds to step S18 and in the case where the number of times of stop is not exceeded, the procedure returns to step S14.
At step S18, the anomalous current detection signal is turned on.
At step S19, the control unit 32 performs the regulator stop processing previously described.
According to the direct-current regulator of the embodiment explained above and the electric circuit that uses the regulator, the effects as follows are obtained.
(1) Because a fuse is provided, even if the control circuit within the direct-current regulator does not work, it is possible to shut off an unexpected large current and to prevent the failure from affecting the periphery.
(2) When an anomaly occurs in the regulator, it is possible to immediately stop the operation of the direct-current regulator by turning on the anomaly detection signal to turn off the fuse connection switch, and therefore, it is possible to prevent the failure from affecting the periphery.
(3) It is no longer necessary to separately provide the current shut-off function, such as a fuse, on the PCB for the direct-current regulator, and therefore, it is possible to reduce the number of parts to be mounted on the PCB and to make an attempt to reduce the failure rate. Further, in the case where an external fuse is provided on the PCB, the characteristics of the fuse material deteriorate with the passage of use time depending on the use environment (temperature, contents in the atmosphere), and therefore, a failure occurs, such as the power source of the PCB or the device cannot be turned off or turned on. In contrast to this, in the direct-current regulator of the embodiment, the fuse is provided within the direct-current regulator element, and therefore, it is possible to give the characteristics that are not readily affected by the use environment.
(4) The accuracy of the fail analysis (FA) of a power conversion element (switching element) is improved and it is made possible to analyze the state of deterioration of an element. By shutting off the overcurrent at the time of the occurrence of a failure, it is made possible to obtain a sample in the early stage of the failure, and therefore, it is possible to improve the analysis accuracy of a failed portion. Due to this, it is possible to determine whether the failure is caused by the insufficient performance of the direct-current regulator itself or by the error in the circuit conditions on the side on which the direct-current regulator is used, and therefore, it is possible to clearly select the method for addressing the failure.
As explained above, according to the embodiment, a direct-current regulator is implemented, which predicts the occurrence of an anomaly by detecting deterioration of the switching element as well as preventing a failure from affecting the peripheral circuits in the case where an anomaly occurs.
All examples and conditional language provided herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a illustrating of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-236038 | Nov 2013 | JP | national |
