JP2019170073A - Dcdc converter for vehicle - Google Patents

Abstract

To enable switching to an asynchronous rectification mode when load is light and to a synchronous rectification mode when load is heavy, and suppress reduction of an output voltage when a load state changes from a light load state to a heavy load state.SOLUTION: In a DCDC converter 1 for a vehicle, a driving unit 34 switches from asynchronous rectification control to synchronous rectification control when a current flowing in a second conductive path 22 has entered a prescribed current increased state or a voltage of the second conductive path 22 has entered a prescribed voltage deteriorated state. A duty determination unit performs a second operation for increasing a duty of an on/off signal to a duty higher than the duty determined by a first operation (an operation that determines the duty of the on/off signal with a prescribed control amount determination scheme) in response to the switching from the asynchronous rectification control to the synchronous rectification control by the driving unit 34, and performs the first operation after the second operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an in-vehicle DCDC converter.

  Two types of DCDC converters conventionally provided are known as a control method, a synchronous rectification method and an asynchronous rectification method. It is known that using synchronous rectification can reduce power loss compared to asynchronous rectification, but using synchronous rectification at light loads with small load currents turns on and off switching elements for synchronous rectification. However, the drive power for reducing the efficiency. Therefore, it can be said that it is desirable to use a synchronous rectification method at a heavy load and an asynchronous rectification method at a light load. Therefore, in the DCDC converter of Patent Document 1, the synchronous rectification method and the asynchronous rectification method are switched based on the absolute value of the off period of the switching element on the high side.

Japanese Patent No. 5428713

  When switching from the light load state to the heavy load state as in Patent Document 1, switching from the asynchronous rectification method to the synchronous rectification method enables efficient driving according to the load state. Simply detecting that the load has changed to the heavy load state and switching to the synchronous rectification method causes a problem that the follow-up to the load fluctuation is delayed and the output voltage tends to decrease.

  The present invention has been made to solve at least one of the above-described problems, and can be switched between an asynchronous rectification method at a light load and a synchronous rectification method at a heavy load, from a light load state to a heavy load. An object of the present invention is to realize an in-vehicle DCDC converter that can suppress a decrease in output voltage when the state changes.

The DCDC converter for in-vehicle use which is one of the present invention is
When a high-side first switching element, a low-side second switching element, and an inductor are provided, and one of the first switching element and the second switching element receives an on / off signal from the outside A voltage converting unit configured to convert an input voltage applied to the first conductive path and apply an output voltage to the second conductive path, wherein a diode is connected in parallel to at least the other element;
Based on the value of the voltage applied to the second conductive path or the value of the current flowing through the second conductive path, the value of the current flowing through the second conductive path or the value of the voltage applied to the second conductive path A duty determination unit capable of performing a first operation for determining a duty of the on / off signal by a predetermined control amount determination method so as to approach a target value;
The on / off signal having the duty determined by the duty determining unit is configured to be output to the one element, and the other element is alternately arranged with the one element when the on / off signal is applied to the one element. A drive unit configured to switch between synchronous rectification control for turning on and off and asynchronous rectification control for maintaining the other element in an off state when the on / off signal is applied to the one element;
Have
When the current flowing through the second conductive path is in a predetermined current increasing state or when the voltage of the second conductive path is in a predetermined voltage decreasing state, the driving unit performs the synchronous rectification from the asynchronous rectification control. Switch to control,
The duty determination unit is configured to increase a duty of the on / off signal to a higher duty than a duty determined in the first operation in response to the drive unit switching from the asynchronous rectification control to the synchronous rectification control. The first operation is performed after the second operation.

In the on-vehicle DCDC converter according to one aspect of the present invention, the drive unit is configured such that the current flowing through the second conductive path is in a predetermined current increasing state or the voltage of the second conductive path is in a predetermined voltage decreasing state. In this case, the asynchronous rectification control is switched to the synchronous rectification control. Because of such a configuration, asynchronous rectification control can be used in a light load state with a relatively small load current, and synchronous rectification control can be used in a heavy load state with a relatively large additional current. Therefore, efficient control can be employed in accordance with the state of the load current.
Then, the duty determining unit performs the duty of the on / off signal in the first operation (operation for determining the duty of the on / off signal by a predetermined control amount determination method) in response to the drive unit switching from asynchronous rectification control to synchronous rectification control. A second operation for increasing the duty to a higher duty than the determined duty is performed, and the first operation is performed after the second operation. Because of such a configuration, when the load changes from a light load state to a heavy load state, a higher duty than the duty determined by the first operation (operation for determining the duty of the on / off signal by a predetermined control amount determination method) The output immediately after changing to the heavy load state is forcibly increased, so that the response delay of the asynchronous rectification control and the follow-up delay when switching from the asynchronous rectification control to the synchronous rectification control can be covered. And after performing the operation | movement which suppresses the fall of an output voltage immediately after the fluctuation | variation of a load state in this way, the efficient synchronous rectification control according to the load current at the time of a heavy load state is performed by switching to a 1st operation | movement. It can be carried out.

1 is a circuit diagram schematically showing an in-vehicle power supply system including an in-vehicle DCDC converter according to Embodiment 1. FIG. It is a circuit diagram which shows the example which actualized the control part about the DCDC converter for vehicles of Example 1. FIG. It is a timing chart which illustrates the relationship between the output of a triangular wave generation circuit when the output is not made from a differentiation circuit, and the output of a comparison circuit. 4 is a timing chart illustrating the relationship between the output of a triangular wave generation circuit before and after switching from asynchronous rectification control to synchronous rectification control and the output of a comparison circuit; 6 is a timing chart illustrating the relationship among output voltage, output current, detection circuit output, comparison circuit input, high-side PWM signal, and low-side PWM signal before and after switching from asynchronous rectification control to synchronous rectification control. Output voltage, output current, detection circuit output, comparison circuit input, high-side PWM signal, low-side PWM signal before and after switching from asynchronous rectification control to synchronous rectification control in a configuration without a differentiation circuit It is a timing chart which illustrates a relationship.

Here, a desirable example of the invention will be shown.
The duty determination unit performs the second operation in response to the drive unit switching from asynchronous rectification control to synchronous rectification control, and then gradually decreases the duty of the on / off signal from the high duty increased in the second operation over time. The third operation may be performed, and the first operation may be performed after the third operation.

  In this way, after the output voltage drop immediately after the change from the light load state to the heavy load state is quickly suppressed by the second operation, the output voltage drop continues to be suppressed for a certain period of time by the third operation. Can do. In the third operation, the duty of the on / off signal is gradually decreased over time from a high duty (duty increased in the second operation), so that the forcedly increased duty is gradually decreased to suit the load state. It can be close to the value. As described above, after performing the second operation and the third operation (operation for suppressing the decrease of the output voltage) in the transition period immediately after the change of the load state, the load current in the heavy load state is obtained by switching to the first operation. It is possible to perform efficient synchronous rectification control according to the above.

  An in-vehicle DCDC converter which is one of the present invention generates a first voltage signal which is a voltage signal corresponding to a value of a voltage applied to a second conductive path or a value of a current flowing through the second conductive path. An output detection circuit may be included. The duty determination unit includes a differential amplifier circuit that generates a second voltage signal that is a voltage signal obtained by amplifying the difference between the first voltage signal generated by the output detection circuit and the reference voltage, and a predetermined triangular wave voltage. A triangular wave generating circuit that generates a signal and a non-current value when the value of the current flowing through the second conductive path is less than a predetermined current threshold or when the value of the voltage applied to the second conductive path is equal to or greater than a predetermined voltage threshold Outputs a detection signal, and differs from the non-detection signal when the value of the current flowing through the second conductive path is greater than or equal to the current threshold or when the value of the voltage applied to the second conductive path is less than the voltage threshold A detection circuit that outputs a detection signal, a differential circuit that gradually reduces the output voltage after the output voltage rises in response to the signal output from the detection circuit switching from the non-detection signal to the detection signal, and differential amplification Generated by the circuit The second voltage signal is used as a threshold voltage signal when the two voltage signal is equal to or higher than the third voltage signal that is a signal of the output voltage from the differentiating circuit, and the third voltage signal is determined when the third voltage signal is equal to or higher than the second voltage signal. As a threshold voltage signal, an off signal is output when the triangular wave voltage signal is larger than the threshold voltage signal, and an on signal is output when the triangular wave voltage signal is smaller than the threshold voltage signal. A comparison circuit that generates a PWM signal. In this case, the method in which the comparison circuit compares the second voltage signal and the triangular wave voltage signal to determine the duty of the PWM signal can be a “predetermined control amount determination method”. The operation of determining the duty of the PWM signal by comparing the “rising output voltage” and the “triangular wave voltage signal” that are output can be set as the “second operation”, and the comparison circuit is set to “rise from the differentiation circuit” The operation of determining the duty of the PWM signal by comparing the “gradually decreasing output voltage” output after the output voltage with the “triangular wave voltage signal” can be referred to as a “third operation”.

In this configuration, as the value of the voltage applied to the second conductive path or the value of the current flowing through the second conductive path increases, the difference between the first voltage signal generated by the output detection circuit and the reference voltage decreases. As a result, the second voltage signal generated by the differential amplifier circuit is also reduced.
The comparison circuit outputs the second voltage signal generated by the differential amplifier circuit and the third voltage signal that is the signal of the output voltage from the differentiating circuit if the second voltage signal is greater than or equal to the third voltage signal. The second voltage signal is a threshold voltage signal, and if the third voltage signal is greater than or equal to the second voltage signal, the third voltage signal is the threshold voltage signal, and an off signal is output when the triangular wave voltage signal is greater than the threshold voltage signal When the triangular wave voltage signal is smaller than the threshold voltage signal, the PWM signal is generated so as to output the ON signal.
With this configuration, if the second voltage signal (the signal generated by the differential amplifier circuit) is equal to or higher than the third voltage signal (the output voltage signal from the differentiating circuit), the comparison circuit outputs the second voltage signal. Operates so as to determine the duty based on the signal (signal generated by the differential amplifier circuit), and the duty is increased as the second voltage signal is increased, and the duty is decreased as the second voltage signal is decreased. In this way, a PWM signal is generated. Therefore, it is possible to perform feedback control in which the PWM signal is changed so as to approach the desired target output (target voltage value or target current value).
On the other hand, if the third voltage signal (the signal of the output voltage from the differentiation circuit) is equal to or higher than the second voltage signal (a signal generated by the differential amplifier circuit), the comparison circuit performs PWM based on the third voltage signal. Generate a signal. Specifically, when the value of the voltage applied to the second conductive path changes from a state that is equal to or greater than a predetermined voltage threshold to a state that is less than the voltage threshold, or the value of the current flowing through the second conductive path is the predetermined current threshold The signal output from the detection circuit switches from the non-detection signal to the detection signal when the state changes from a state less than the current threshold to a state equal to or higher than the current threshold, and the differentiation circuit raises the output voltage in response to the switch to the detection signal. After the operation, the output voltage is gradually decreased.
In this configuration, the operation in which the comparison circuit compares the “rising output voltage output from the differentiation circuit immediately after the detection signal is output” and the “triangular wave voltage signal” to determine the duty of the PWM signal is the “first operation”. The comparator circuit compares the “gradually decreasing output voltage” output after the “rising output voltage” from the differentiation circuit and the “triangular wave voltage signal” to determine the duty of the PWM signal. When the drive unit switches from asynchronous rectification control to synchronous rectification control, the detection circuit, differentiation circuit, and comparison circuit respond quickly and increase the duty of the PWM signal. After that, the duty of the PWM signal can be gradually reduced.
Then, the comparator circuit gradually decreases the duty of the PWM signal in this way, and then generates “the second voltage signal (generated by the differential amplifier circuit) rather than the third voltage signal (signal of the output voltage from the differentiating circuit)”. In response to switching to a state in which the signal) has a larger voltage value, the duty is again determined based on the second voltage signal (a signal generated by the differential amplifier circuit). Therefore, when the third operation is switched to the first operation again, a large variation in duty is less likely to occur. Therefore, after performing the operation in the transition period (second operation and third operation), it is possible to smoothly shift to the synchronous rectification control approaching the desired target output (target voltage value or target current value).

<Example 1>
Embodiment 1 of the present invention will be described below.
(Outline of in-vehicle power supply system)
An in-vehicle power supply system 100 shown in FIG. 1 includes a first power supply unit 91 and a second power supply unit 92 configured as an in-vehicle power supply unit, and an in-vehicle DCDC converter 1 (hereinafter also referred to as DCDC converter 1). It is comprised as a system which can supply electric power to the load 94 mounted in the vehicle. The load 94 is a vehicle-mounted electrical component, and the type and number thereof are not limited. Further, in the example of FIG. 1, an example in which the load 94 is electrically connected to the low-voltage side wiring part 82 is shown, but a load may be connected to the high-voltage side wiring part 81.

  The first power supply unit 91 is constituted by power storage means such as a lithium ion battery or an electric double layer capacitor, for example, and generates a first predetermined voltage. For example, the terminal on the high potential side of the first power supply unit 91 is kept at a predetermined voltage (for example, 24 V or 48 V), and the terminal on the low potential side is kept at the ground potential (0 V). A terminal on the high potential side of the first power supply unit 91 is electrically connected to a wiring unit 81 provided in the vehicle, and the first power supply unit 91 applies a predetermined voltage to the wiring unit 81. The terminal on the low potential side of the first power supply unit 91 is electrically connected to a reference conductive path 83 configured as a ground part in the vehicle. The wiring portion 81 is connected to the input side terminal 51 of the DCDC converter 1 and is electrically connected to the first conductive path 21 via the input side terminal 51.

  The second power supply unit 92 is constituted by power storage means such as a lead storage battery, for example, and generates a second predetermined voltage lower than the first predetermined voltage generated by the first power supply unit 91. For example, the terminal on the high potential side of the second power supply unit 92 is maintained at 12V, and the terminal on the low potential side is maintained at the ground potential (0V). A terminal on the high potential side of the second power supply unit 92 is electrically connected to a wiring unit 82 provided in the vehicle, and the second power supply unit 92 applies a predetermined voltage to the wiring unit 82. A terminal on the low potential side of the second power supply unit 92 is electrically connected to the reference conductive path 83. The wiring part 82 is connected to the output side terminal 52 of the DCDC converter 1, and is electrically connected to the second conductive path 22 via the output side terminal 52.

  The reference conductive path 83 is configured as a vehicle ground, and is maintained at a constant ground potential (0 V). The reference conductive path 83 is electrically connected to the low-potential side terminal of the first power supply unit 91 and the low-potential side terminal of the second power supply unit 92, and further to the source of the second switch unit 12 described later. Are electrically connected through the third conductive path 23 and the ground terminal 53.

  The DCDC converter 1 is configured as an in-vehicle step-down DCDC converter that is mounted and used in a vehicle. In the following description, the DCDC converter 1 uses the first conductive path 21 as an input side conductive path, the second conductive path 22 as an output side conductive path, and steps down the DC voltage applied to the first conductive path 21. An example of operation to output to the second conductive path 22 will be described.

(Outline of DCDC converter for automotive use)
The DCDC converter 1 mainly includes a first conductive path 21, a second conductive path 22, a third conductive path 23, a voltage conversion unit 10, a control unit 30, a voltage detection circuit 42, a current detection unit 44, an input side terminal 51, and an output. A side terminal 52, a ground terminal 53, and the like are provided.

  The first conductive path 21 is configured as a primary side (high voltage side) power supply line to which a relatively high voltage is applied. The first conductive path 21 is electrically connected to a high potential side terminal of the first power supply unit 91 via the wiring unit 81 and is configured to be applied with a predetermined DC voltage from the first power supply unit 91. . In the configuration of FIG. 1, an input side terminal 51 is provided at an end of the first conductive path 21, and a wiring portion 81 is electrically connected to the input side terminal 51.

  The second conductive path 22 is configured as a secondary (low voltage side) power supply line to which a relatively low voltage is applied. The second conductive path 22 is electrically connected to the high potential side terminal of the second power supply unit 92 via the wiring unit 82 and is smaller than the output voltage of the first power supply unit 91 from the second power supply unit 92. It is configured to apply a DC voltage. In the configuration of FIG. 1, an output side terminal 52 is provided at the end of the second conductive path 22, and a wiring portion 82 is electrically connected to the output side terminal 52.

  The voltage conversion unit 10 is a main part of a switching step-down DCDC converter, and one of the first switching element 11A and the second switching element 12A connected in series receives an on / off signal from the outside. Sometimes, a step-down operation can be performed in which the input voltage applied to the first conductive path 21 is converted and the output voltage is applied to the second conductive path 22. In the representative example described below, a case where the first switching element 11A corresponds to an example of one element and the second switching element 12A corresponds to an example of the other element will be described as an example. .

  The voltage conversion unit 10 is provided between the first conductive path 21 and the second conductive path 22, and is configured as a high-side first switch unit configured as a semiconductor switch electrically connected to the first conductive path 21. 11, a semiconductor switch electrically connected between the first conductive path 21 and the reference conductive path 83 (conductive path maintained at a predetermined reference potential lower than the potential of the first conductive path 21). The second switch section 12 on the low side, and the first switch section 11 and the inductor 14 electrically connected between the second switch section 12 and the second conductive path 22. Although not shown in the figure, an input-side capacitor (not shown) is provided between the first conductive path 21 and the third conductive path 23, and is illustrated between the second conductive path 22 and the third conductive path 23. An output side capacitor is not provided.

  Both the first switch unit 11 and the second switch unit 12 are configured as N-channel MOSFETs. The first switch unit 11 is mainly configured by a first switching element 11A and a diode 11B, and the second switch unit 12 is mainly configured by a second switching element 12A and a diode 12B. The diode 11B is a body diode in the first switch unit 11 (MOSFET), and the first switching element 11A indicates a portion of the first switch unit 11 (MOSFET) excluding the diode 11B. Similarly, the diode 12B is a body diode in the second switch unit 12 (MOSFET), and the second switching element 12A indicates a portion of the second switch unit 12 (MOSFET) excluding the diode 12B.

  One end of the first conductive path 21 is connected to the drain of the first switching element 11A on the high side. The drain of the first switching element 11A is electrically connected to an electrode on one side of an input side capacitor (not shown) and connected to the high potential side terminal of the first power supply unit 91 via the first conductive path 21 and the wiring unit 81. Are also electrically connected and can conduct between them. Further, the drain of the second switching element 12A on the low side and one end of the inductor 14 are electrically connected to the source of the first switching element 11A and can be conducted between them. An ON signal (drive signal) and an OFF signal (non-drive signal) from the drive unit 34 provided in the control unit 30 are input to the gate of the first switching element 11A. The first switching element 11A is switched between an on state and an off state in response to the signal. The diode 11B is connected in parallel with the first switching element 11A, the anode is electrically connected to the source of the first switching element 11A, the drain of the second switching element 12A on the low side, and one end of the inductor 14, and the cathode is connected The drain of the first switching element 11 </ b> A and the first conductive path 21 are electrically connected.

  A third conductive path 23 is connected to the source of the second switching element 12A on the low side. The third conductive path 23 is a conductive path between the source of the second switching element 12 </ b> A and the ground terminal 53, and is electrically connected to the reference conductive path 83 via the ground terminal 53. It is kept at the same potential as (0V). The third conductive path 23 is electrically connected to electrodes on the other side of the input side capacitor and the output side capacitor (not shown). An ON signal (driving signal) and an OFF signal (non-driving signal) from the control unit 30 are also input to the gate of the second switching element 12A on the low side, and according to the signal from the control unit 30 Thus, the second switching element 12A is switched between an on state and an off state. The diode 12B is connected in parallel with the second switching element 12A, the anode is electrically connected to the third conductive path 23, the cathode is the drain of the second switching element 12A, the source of the first switching element 11A, and the inductor 14 Is electrically connected to one end.

  One end of the inductor 14 is connected to a connection portion between the first switch portion 11 and the second switch portion 12, and one end thereof is electrically connected to the source of the first switching element 11A and the drain of the second switching element 12A. Has been. The other end of the inductor 14 is connected to the second conductive path 22 (specifically, a portion of the second conductive path 22 closer to the voltage conversion unit 10 than the current detection unit 44).

  The current detection unit 44 includes a resistor 44A and a differential amplifier 44B and has a value indicating the current flowing through the second conductive path 22 (specifically, an analog voltage corresponding to the value of the current flowing through the second conductive path 22). ) Is output. The voltage drop generated in the resistor 44A due to the output current from the voltage conversion unit 10 is amplified by the differential amplifier 44B to become a detection voltage (analog voltage) corresponding to the output current, and is input to the duty determination unit 32.

  The voltage detection circuit 42 corresponds to an example of an output detection circuit, and is configured as a circuit that generates a “first voltage signal” that is a voltage signal corresponding to the value of the voltage applied to the second conductive path 22. . The voltage detection circuit 42 is connected to the second conductive path 22 and sets a value for specifying the voltage of the second conductive path 22 (potential difference between the potential of the second conductive path 22 and the potential of the reference conductive path 83) to the duty determining unit. 32 is configured to be input. The voltage detection circuit 42 may be a known voltage detection circuit that can input a value indicating the voltage of the second conductive path 22 to the duty determining unit. In the example of FIG. 2, the voltage detection circuit 42 is between the second conductive path 22 and the ground. The voltage Vout of the second conductive path 22 (potential difference between the second conductive path 22 and the ground) is divided by resistors 42A and 42B connected in series to each other, and a value proportional to the voltage of the second conductive path 22 (resistor When the resistance values of 42A and 42B are R1 and R2, respectively, and the voltage of the second conductive path 22 is Vout, R2 × Vout / (R1 + R2)) is set to the duty determination unit 32 (specifically, the differential amplifier circuit 64). The voltage dividing circuit is inputted to the negative terminal). The example of the voltage detection circuit 42 shown here is merely an example, and for example, a circuit that inputs the voltage Vout of the second conductive path 22 to the negative terminal of the differential amplifier circuit 64 may be used. .

  The control unit 30 includes a duty determination unit 32 and a drive unit 34. The duty determination unit 32 includes a detection signal (analog voltage signal proportional to the voltage Vout of the second conductive path 22) from the voltage detection circuit 42 and a detection signal (current flowing through the second conductive path 22) from the current detection unit 44. A proportional analog voltage signal) is provided, and the duty determination unit 32 determines the duty by feedback control so that the voltage Vout of the second conductive path 22 approaches the target value, and generates a PWM signal.

  The drive unit 34 is a PWM signal corresponding to the PWM signal output from the duty determination unit 32 (a PWM signal having the same cycle and the same duty as the PWM signal output from the duty determination unit, and the ON signal is the first switching element. 11A is output to the gate of the first switching element 11A, and a signal set to a voltage level that can turn on the first switching element 11A and a signal set to a voltage level that can turn off the first switching element 11A.

  The DCDC converter 1 configured as described above functions as a step-down DCDC converter capable of switching between a synchronous rectification method and an asynchronous rectification method. The drive unit 34 is configured to be able to switch between synchronous rectification control and asynchronous rectification control, and in the case of synchronous rectification control, the PWM signal (on / off signal) of the duty determined by the duty determination unit 32 is supplied to the first switching element 11A (one of the switching elements 11A). The second switching element 12A so that the second switching element 12A (the other element) is alternately turned on and off with the first switching element 11A when an on / off signal is applied to the first switching element 11A. By applying a PWM signal also to the gate, the DC voltage applied to the first conductive path 21 is stepped down and output to the second conductive path 22. On the other hand, during the asynchronous rectification control, the drive unit 34 continues to provide the OFF signal to the gate of the second switching element 12A when the PWM signal (ON / OFF signal) is applied to the gate of the first switching element 11A. The DC voltage applied to the first conductive path 21 is stepped down and output to the second conductive path 22 while maintaining the element 12A in the off state.

(Details of in-vehicle DCDC converter)
Based on the voltage value Vout applied to the second conductive path 22, the duty determining unit 32 performs an on / off signal with a predetermined control amount determination method so that the voltage value applied to the second conductive path 22 approaches the target value. It is a circuit which can perform the 1st operation which determines the duty of. Further, the duty determination unit 32 sets the duty of the PWM signal (on / off signal) to a high duty (duty greater than the duty determined in the first operation) in response to the drive unit 34 switching from asynchronous rectification control to synchronous rectification control. After the second operation is performed, the duty of the PWM signal (ON / OFF signal) is gradually decreased from the high duty increased in the second operation over time, and the third operation is performed. After the third operation, the first operation is performed.

  The duty determination unit 32 mainly includes a differential amplifier circuit 64, a triangular wave generation circuit 68, a detection circuit 70, a differentiation circuit 72, a comparison circuit 74, and the like.

  The differential amplifier circuit 64 is a second voltage signal V2 that is a voltage signal obtained by amplifying the difference between the first voltage signal V1 generated by the voltage detection circuit 42 (output detection circuit) and the reference voltage Vref1 with a predetermined amplification factor. Is a circuit that generates The differential amplifier circuit 64 is configured to output a larger voltage proportional to the voltage difference as the difference between the first voltage signal V1 and the reference voltage Vref1 is larger. An output terminal of the differential amplifier circuit 64 is electrically connected to a positive terminal of a comparator 74A described later.

  The triangular wave generation circuit 68 is configured by a known triangular wave generator that periodically generates a voltage signal of a predetermined triangular wave, and rises from the minimum voltage value to the maximum voltage value in a certain rising time in each period, and the maximum voltage value Is a circuit that generates a triangular wave voltage signal that drops from a minimum voltage value to a minimum voltage value at a constant falling time (including about 0). In the example of FIG. 3, the triangular wave generating circuit 68 linearly increases from the minimum voltage value to the maximum voltage value and linearly decreases from the maximum voltage value to the minimum voltage value (specifically, a sawtooth signal). A circuit that generates a wave). Note that the triangular wave output from the triangular wave generating circuit 68 is not limited to the sawtooth wave shown in FIG. 3, and may be a triangular wave having the same rise time and fall time in each cycle. It may be a triangular wave that rises non-linearly (non-linearly) to a value, or a triangular wave that falls non-linearly (non-linearly) from a maximum voltage value to a minimum voltage value.

  The detection circuit 70 outputs a non-detection signal when the value of the current flowing through the second conductive path 22 is less than a predetermined current threshold, and outputs a detection signal different from the non-detection signal when the value is equal to or greater than the predetermined current threshold. Configure the output. The detection circuit 70 compares the voltage signal output from the current detection unit 44 (an analog voltage proportional to the value of the current flowing through the second conductive path 22) with a constant reference voltage Vref2, and compares the voltage signal with the reference voltage Vref2. When the voltage output by 44 is smaller, a low level signal of the first voltage (for example, 0V) is output as a non-detection signal, and when the voltage output by the current detection unit 44 is larger than the reference voltage Vref2, the first voltage is output. A high-level signal of a second voltage (for example, several V) that is larger than that is output as a detection signal. In this example, the current value of the second conductive path 22 when the voltage output from the current detection unit 44 becomes the reference voltage Vref2 corresponds to an example of “predetermined current threshold”.

  The differentiating circuit 72 is a circuit that uses the output voltage from the detection circuit 70 as an input voltage and outputs a time derivative (gradient) of the input voltage, and is configured such that the output is a derivative of the input. This differentiation circuit 72 is a capacitor having one end electrically connected to the output terminal of the detection circuit 70 and the other end electrically connected to the output terminal of the differential amplifier circuit 64 and the positive terminal of the comparator 74A. 72A, and a resistor 72B having one end electrically connected to the other terminal of the capacitor 72A and the other end electrically connected to the ground. The differentiating circuit 72 is used when the output signal of the detection circuit 70 continues to be maintained as a non-detection signal (low level signal) or a detection signal (high level signal) after a predetermined time has elapsed since the output of the detection circuit 70 is switched. The output voltage of the differential amplifier circuit 64 is used as its own output voltage, and the output voltage of the detection circuit 70 is switched from the non-detection signal (low level signal) to the detection signal (high level signal). After rising, the circuit gradually reduces its own output voltage.

  The comparison circuit 74 includes a comparator 74A and a plurality of input-side signal lines connected to the comparator 74A. The signal line connected to the negative terminal of the comparator 74A is electrically connected to the triangular wave generating circuit 68, and the output voltage (triangular wave voltage signal) of the triangular wave generating circuit 68 is connected to the negative terminal of the comparator 74A. It is designed to be entered. The signal line connected to the positive terminal of the comparator 74A is electrically connected to the output side of each of the differential amplifier circuit 64 and the differentiating circuit 72, and the output voltage of the differential amplifier circuit 64 (second output). A large voltage of the voltage signal V2) and the output voltage (third voltage signal V3) of the differentiating circuit 72 is input to the positive terminal of the comparator 74A.

  The comparison circuit 74 configured as described above includes the second voltage signal V2 among the second voltage signal V2 generated by the differential amplifier circuit 64 and the output voltage signal (third voltage signal V3) from the differentiation circuit 72. Is the third voltage signal V3 or more, the second voltage signal V2 is the threshold voltage signal Vth, and if the third voltage signal V3 is the second voltage signal V2 or more, the third voltage signal V3 is the threshold voltage signal Vth. If the second voltage signal V2 and the third voltage signal V3 are equivalent, both voltage signals become threshold voltage signals. Then, the comparator 74 compares the threshold voltage signal Vth with the triangular wave voltage signal (the output voltage signal of the triangular wave generating circuit 68) by the comparator 74A, and when the triangular wave voltage signal is larger than the threshold voltage signal Vth. An OFF signal is output, and a PWM signal is generated so as to output an ON signal when the triangular wave voltage signal is smaller than the threshold voltage signal Vth, and is output to the signal line 78A.

  Since the second voltage signal V2 (the signal generated by the differential amplifier circuit 64) is equal to or higher than the third voltage signal V3 (the output voltage signal from the differentiation circuit 72), the comparison circuit 74 is configured. Operates so as to determine the duty based on the second voltage signal V2 (a signal generated by the differential amplifier circuit 64). For example, when the second voltage signal V2 is the threshold voltage signal Vth, when the threshold voltage signal Vth and the triangular voltage signal (output of the triangular wave generation circuit 68) show temporal changes as shown in the upper part of FIG. The PWM signal output from the comparator 74A is a signal indicating a change with time as shown in the lower part of FIG. As described above, when the second voltage signal V2 is the threshold voltage signal Vth, the threshold voltage signal Vth shown in FIG. 3 increases as the second voltage signal V2 increases, so that the duty is increased and the second voltage signal V2 is decreased. The PWM signal is generated while changing the duty to be small.

  On the other hand, the comparison circuit 74 determines that the third voltage signal V3 (the output voltage signal from the differentiation circuit 72) is equal to or higher than the second voltage signal V2 (the signal generated by the differential amplifier circuit 64). A PWM signal is generated based on the signal V3. In the example of FIG. 4, the value of the current flowing through the second conductive path 22 at the timing of time t <b> 1 changes from a state less than the above “current threshold” to a state equal to or higher than the “current threshold”, and is detected at the timing of time t <b> 1. An example in which the signal output from the circuit 70 is switched from the non-detection signal to the detection signal is shown. In this example, before the time t1, the second voltage signal V2 becomes the threshold voltage signal Vth, so that a PWM signal is generated as in the example of FIG. However, when the signal output from the detection circuit 70 is switched from the non-detection signal to the detection signal at time t1, the differentiation circuit 72 operates so as to raise the output voltage V3 in accordance with the switching to the detection signal. The output voltage (third voltage signal V3) operates so as to gradually decrease. During this period (period from when the output voltage of the differentiating circuit 72 (third voltage signal V3) rises to the value of the second voltage signal V2), the third voltage signal V3 becomes the threshold voltage signal Vth. The comparison circuit 74 compares the duty of the PWM signal (ON / OFF signal) output from the comparator 74A with the duty determined by the first operation (assuming the third voltage signal V3 at that time) in the period T1 immediately after the time t1. A second operation for increasing the duty to a higher duty than the duty of the PWM signal generated by the comparator 74A when the comparator 74A compares the second voltage signal V2 and the triangular wave voltage signal without input to the comparator 74A. After the second operation, the period T1, T3, T4, T5, and T6 until the value of the third voltage signal V3 decreases to the value of the second voltage signal V2 is the period T1 increased by the second operation. The third operation is performed so as to gradually decrease the duty from the high duty. Then, after the value of the third voltage signal V3 becomes the value of the second voltage signal V2, the first operation is performed again.

  In this configuration, the method in which the comparison circuit 74 compares the second voltage signal V2 with the triangular wave voltage signal to determine the duty of the PWM signal is the “predetermined control amount determination method”. The operation for determining the duty of the PWM signal by the “method” is the “first operation”. The operation in which the comparison circuit 74 compares the “rising output voltage” output from the differentiation circuit 72 with the “triangular wave voltage signal” to determine the duty of the PWM signal is the “second operation”. Furthermore, the operation in which the comparison circuit 74 determines the duty of the PWM signal by comparing the “gradually decreasing output voltage” output after the output voltage rising from the differentiation circuit 72 with the “triangular wave voltage signal”. Third operation ”.

  The driving unit 34 transmits the PWM signal output from the comparator 74A directly to the signal line 78A electrically connected to the gate of the first switching element 11A or by increasing the ON signal to a certain level. 34C, and a second signal transmission unit 34D that generates a signal to be supplied to the signal line 78B electrically connected to the gate of the second switching element 12A. The second signal transmission unit 34D includes an inverting circuit 34A that inverts the PWM signal output from the comparator 74A, and an AND circuit 34B. The AND circuit 34B is a circuit that outputs an AND operation result of the output from the inverting circuit 34A and the output of the detection circuit 70, and the output from the inverting circuit 34A and the output of the detection circuit 70 are both high level signals. A high level signal is output to, and a low level signal is output otherwise.

  The drive unit 34 thus configured performs asynchronous rectification control when the detection circuit 70 outputs a non-detection signal (low level signal), and the detection circuit 70 outputs a detection signal (high level signal). Synchronous rectification control is performed when In this example, the state in which the detection circuit 70 outputs a non-detection signal is “a state in which the current flowing through the second conductive path 22 is not in a predetermined current increase state”, and the state in which the detection circuit 70 outputs a detection signal is “ This is a state where the current flowing through the second conductive path 22 is in a predetermined current increasing state. The drive unit 34 performs synchronous rectification from asynchronous rectification control when the current flowing through the second conductive path 22 reaches a predetermined current increase state (that is, when the output of the detection circuit 70 is switched from the non-detection signal to the detection signal). Operates to switch to control.

Hereinafter, the effect of this configuration will be exemplified.
In the on-vehicle DCDC converter 1 described above, the drive unit 34 is configured such that the current flowing through the second conductive path 22 is in a predetermined current increasing state or the voltage of the second conductive path 22 is in a predetermined voltage decreasing state. When switching from asynchronous rectification control to synchronous rectification control. Because of such a configuration, asynchronous rectification control can be used in a light load state with a relatively small load current, and synchronous rectification control can be used in a heavy load state with a relatively large additional current. Therefore, efficient control can be employed in accordance with the state of the load current.

  Then, as shown in the example after time t1 in FIG. 5, the duty determination unit 32 changes the duty of the on / off signal to the first operation (predetermined in response to the switching of the drive unit 34 from the asynchronous rectification control to the synchronous rectification control). The second operation for increasing the duty to a higher duty than the duty determined by the control amount determination method (operation for determining the duty of the on / off signal) is performed, and the first operation is performed after the second operation. Because of such a configuration, the first operation (the operation for determining the duty of the on / off signal by a predetermined control amount determination method) when the light load state is changed to the heavy load state, such as before and after time t1 in FIG. ) When the duty is switched to the synchronous rectification control from the asynchronous rectification control by delaying the asynchronous rectification control, the output immediately after changing to the heavy load state is forcibly increased and the output is forcibly increased. Tracking delay can be covered. And after performing the operation | movement which suppresses the fall of an output voltage immediately after the fluctuation | variation of a load state in this way, the efficient synchronous rectification control according to the load current at the time of a heavy load state is performed by switching to a 1st operation | movement. It can be carried out.

  In the duty determination unit 32, the drive unit 34 is synchronized with the asynchronous rectification control from the asynchronous rectification control as in the operation of the period T shown in FIG. 5 (the period from when the output of the differentiation circuit 72 rises until the time corresponding to the time constant elapses). After performing the second operation in response to switching to the rectification control, the third operation is performed in which the duty of the on / off signal is gradually decreased from the high duty increased in the second operation with the passage of time. After that, the first operation is performed again. In this way, after the output voltage drop immediately after the change from the light load state to the heavy load state is quickly suppressed by the second operation, the output voltage drop continues to be suppressed for a certain period of time by the third operation. Can do. In the third operation, the duty of the on / off signal is gradually decreased over time from a high duty (duty increased in the second operation), so that the forcedly increased duty is gradually decreased to suit the load state. It can be close to the value. As described above, after performing the second operation and the third operation (operation for suppressing the decrease of the output voltage) in the transition period immediately after the change of the load state, the load current in the heavy load state is obtained by switching to the first operation. It is possible to perform efficient synchronous rectification control according to the above.

  FIG. 6 illustrates a case where the output current changes in the same manner as in FIG. 5 when the differentiation circuit 72 is omitted from the circuit of FIG. In this example, when the light load state changes to the heavy load state at time t1, the output voltage temporarily decreases, and recovery of such a decrease in output voltage is delayed. However, with the configuration as shown in FIG. 2, even if the output voltage drops near time t1 as shown in FIG. 5, the drop can be quickly recovered.

  Specifically, the DCDC converter 1 includes a voltage detection circuit 42 as an output detection circuit that generates a voltage signal (first voltage signal V1) corresponding to the value of the voltage applied to the second conductive path 22. Then, the duty determining unit 32 generates a second voltage signal V2 that is a voltage signal obtained by amplifying the difference between the first voltage signal V1 generated by the voltage detection circuit 42 (output detection circuit) and the reference voltage Vref1. The dynamic amplification circuit 64, the triangular wave generation circuit 68 for generating a voltage signal of a predetermined triangular wave, and the non-detection signal are output when the value of the current flowing through the second conductive path 22 is less than the threshold value, and the threshold value is exceeded. In this case, the detection circuit 70 outputs a detection signal different from the non-detection signal, and the output voltage V3 rises in response to the signal output from the detection circuit 70 switching from the non-detection signal to the detection signal. A voltage signal having a large voltage value among the differentiation circuit 72 that gradually decreases V3, the second voltage signal V2 generated by the differential amplifier circuit 64, and the third voltage signal V3 that is the output voltage signal from the differentiation circuit 72. When the threshold voltage signal Vth is the threshold voltage signal Vth, an off signal is output when the triangular wave voltage signal is larger than the threshold voltage signal Vth, and an on signal is output when the triangular wave voltage signal is smaller than the threshold voltage signal Vth And a comparison circuit 74 for generating a PWM signal. A method in which the comparison circuit 74 compares the second voltage signal V2 with the triangular wave voltage signal to determine the duty of the PWM signal is a “predetermined control amount determination method”. The operation of determining the duty of the PWM signal by comparing the “rising output voltage” and the “triangular wave voltage signal” is referred to as a “second operation”, and the comparison circuit 74 outputs the “output voltage rising from the differentiation circuit 72”. The operation of determining the duty of the PWM signal by comparing the “gradually decreasing output voltage” output after “and the triangular wave voltage signal” is referred to as a “third operation”.

  In this configuration, the difference between the first voltage signal V1 generated by the voltage detection circuit 42 (output detection circuit) and the reference voltage Vref1 decreases as the value of the voltage applied to the second conductive path 22 increases. As a result, the second voltage signal V2 generated by the differential amplifier circuit 64 is also reduced. The comparison circuit 74 includes the second voltage signal V2 generated by the differential amplifier circuit 64 and the output voltage signal (third voltage signal V3) from the differentiating circuit 72, the second voltage signal V2 being the third voltage. If the signal is V3 or higher, the second voltage signal V2 is the threshold voltage signal Vth, and if the third voltage signal V3 is the second voltage signal V2 or higher, the third voltage signal V3 is the threshold voltage signal Vth. The PWM signal is generated so that an off signal is output when the triangular wave voltage signal is larger, and an on signal is output when the triangular wave voltage signal is smaller than the threshold voltage signal Vth. Since the second voltage signal V2 (the signal generated by the differential amplifier circuit 64) is equal to or higher than the third voltage signal V3 (the output voltage signal from the differentiation circuit 72), the comparison circuit 74 is configured. Operates so as to determine the duty based on the second voltage signal V2 (a signal generated by the differential amplifier circuit 64), and the duty increases as the second voltage signal V2 increases. The PWM signal is generated while changing the duty to decrease as the value decreases. In other words, the PWM signal is generated while changing the duty to decrease as the value of the voltage applied to the second conductive path 22 increases, and the duty increases as the value of the voltage applied to the second conductive path 22 decreases. The PWM signal is generated while being changed. Therefore, it is possible to perform feedback control in which the PWM signal is changed so as to approach a desired target output (target voltage value).

  On the other hand, the comparison circuit 74 determines that the third voltage signal V3 (the output voltage signal from the differentiation circuit 72) is equal to or higher than the second voltage signal V2 (the signal generated by the differential amplifier circuit 64). A PWM signal is generated based on the signal V3. Specifically, the signal output from the detection circuit 70 when the value of the current flowing through the second conductive path 22 changes from a state less than a predetermined current threshold to a state greater than or equal to the current threshold is detected from the non-detection signal. The differential circuit 72 operates to increase the output voltage V3 in response to the switching to the detection signal, and then operates to gradually decrease the output voltage V3. In this configuration, the comparison circuit 74 compares the “rising output voltage” output from the differentiation circuit 72 immediately after the detection signal is output and the “triangular wave voltage signal” to determine the duty of the PWM signal. The “second operation”, the comparison circuit 74 compares the “gradually decreasing output voltage” output after the “rising output voltage” from the differentiating circuit 72 with the “triangular wave voltage signal”, and the PWM signal Since the operation for determining the duty of this is the “third operation”, when the drive unit 34 switches from the asynchronous rectification control to the synchronous rectification control, the detection circuit 70, the differentiation circuit 72, and the comparison circuit 74 respond quickly. The duty of the PWM signal can be quickly increased and then the duty of the PWM signal can be gradually decreased.

  Then, the comparator circuit 74 gradually decreases the duty of the PWM signal in this way, and then the second voltage signal V2 (differential amplifier circuit) rather than the "third voltage signal V3 (signal of the output voltage from the differentiation circuit 72)". (The signal generated at 64) is switched to the state where the voltage value is larger ", the duty is again determined based on the second voltage signal V2 (the signal generated at the differential amplifier circuit 64). To do. Therefore, when the third operation is switched to the first operation again, a large variation in duty is less likely to occur. Therefore, after performing the operation in the transition period (second operation and third operation), it is possible to smoothly shift to the synchronous rectification control approaching the desired target output (target voltage value). In this example, when the signal output from the detection circuit 70 is switched from the detection signal to the non-detection signal, the synchronous rectification control is switched to the asynchronous rectification control, and the voltage of the signal line 78 is maintained at the low level (off signal). Is done.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition, the embodiments described above and the embodiments described later can be combined within a consistent range.

  In the first embodiment, the voltage detection circuit 42 functions as an output detection circuit, but the current detection unit 44 may function as an output detection circuit. In this case, the voltage signal generated by the current detection unit 44 may be changed to the voltage signal generated by the voltage detection circuit 42 and input to the negative terminal of the differential amplifier circuit 64. In this case, the voltage signal generated by the current detection unit 44 (a voltage signal corresponding to the value of the current flowing through the second conductive path 22) corresponds to an example of the first voltage signal. In this example, based on the value of the current flowing through the second conductive path 22, the duty of the on / off signal is determined by a predetermined control amount determination method so that the value of the current flowing through the second conductive path 22 approaches the target value. The first operation is performed.

  In the first embodiment, the detection circuit 70 outputs a non-detection signal when the value of the current flowing through the second conductive path 22 is less than a predetermined current threshold, and outputs a detection signal when the value is equal to or greater than the current threshold. The detection circuit 70 outputs a non-detection signal when the value of the voltage applied to the second conductive path 22 is equal to or greater than a predetermined voltage threshold, and the detection circuit 70 when the voltage is less than the voltage threshold. May be configured to output. In this case, the state in which the detection circuit 70 outputs the non-detection signal is not a voltage drop state, the state in which the detection circuit 70 outputs the detection signal is the voltage drop state, and the drive unit 34 is connected to the second conductive path 22. When the voltage is in a predetermined voltage drop state (when the output of the detection circuit 70 is switched from the non-detection signal to the detection signal), the asynchronous rectification control is switched to the synchronous rectification control.

  In the first embodiment, the step-down DCDC converter 1 is illustrated as an in-vehicle DCDC converter. However, a step-up DCDC converter may be used.

  In the first embodiment, the DCDC converter 1 having only one voltage converter is illustrated. However, a multiphase DCDC in which a plurality of voltage converters are connected in parallel between the first conductive path and the second conductive path. It is good also as a converter. In this case, the number of phases should just be two or more. Further, it may be a step-down type multi-phase converter, a step-up type multi-phase converter, or a step-up / step-down type multi-phase converter.

  In the first embodiment, the one-way type DCDC converter in which one conductive path is fixed as the first conductive path and the other conductive path is fixed as the second conductive path is illustrated. However, the first conductive path is input-side conductive. A bidirectional type control capable of switching between a control using the second conductive path as the output side conductive path and a control using the second conductive path as the input side conductive path and the first conductive path as the output side conductive path. It may be configured as a converter.

  In Example 1 or the like, the value of the voltage applied to the second conductive path or the value of the second conductive path 2 is determined based on the value of the voltage applied to the second conductive path 22 or the value of the current flowing through the second conductive path 22. Although an example in which the duty of the PWM signal (ON / OFF signal) to be given to the first switching element 11A is determined by a predetermined control amount determination method so that the value of the flowing current approaches the target value is shown, it is applied to the second conductive path 22 In other known control amount determination methods, the feedback control is repeated so that the value of the measured voltage or the current flowing through the second conductive path approaches the target value, and the duty update is repeated according to the feedback control. Good. In this case, in both the synchronous rectification control and the asynchronous rectification control, the duty is decreased so as to increase as the value of the voltage applied to the second conductive path 22 or the value of the current flowing through the second conductive path 22 increases. The duty is determined so that the PWM signal is generated and the PWM signal is generated while the duty is increased as the value of the voltage applied to the second conductive path 22 or the value of the current flowing through the second conductive path 22 decreases. Asynchronous rectification control immediately after the current flowing through the second conductive path 22 exceeds a predetermined current threshold or immediately after the voltage of the second conductive path 22 becomes less than the predetermined voltage threshold. To the synchronous rectification control, the cycle at the time of switching or the next cycle is set as the increase target cycle, and the first operation described above is performed in the increase target cycle. If the duty of the increase target cycle is determined to be larger than the duty determined when assumed (duty determined when it is assumed that the other control amount determination method is applied in the increase target cycle) Good. And what is necessary is just to make it reduce a duty gradually in the several period continuous after the increase object period.

DESCRIPTION OF SYMBOLS 1 ... DCDC converter for vehicle mounting 10 ... Voltage conversion part 11A ... 1st switching element 12A ... 2nd switching element 12B ... Diode 14 ... Inductor 21 ... 1st conductive path 22 ... 2nd conductive path 32 ... Duty determination part 34 ... Drive 42: Voltage detection circuit (output detection circuit)
44 ... Current detection unit 64 ... Differential amplifier circuit 68 ... Triangle wave generation circuit 70 ... Detection circuit 72 ... Differentiation circuit 74 ... Comparison circuit

Claims (3)

When a high-side first switching element, a low-side second switching element, and an inductor are provided, and one of the first switching element and the second switching element receives an on / off signal from the outside A voltage converting unit configured to convert an input voltage applied to the first conductive path and apply an output voltage to the second conductive path, wherein a diode is connected in parallel to at least the other element;
Based on the value of the voltage applied to the second conductive path or the value of the current flowing through the second conductive path, the value of the current flowing through the second conductive path or the value of the voltage applied to the second conductive path A duty determination unit capable of performing a first operation for determining a duty of the on / off signal by a predetermined control amount determination method so as to approach a target value;
The on / off signal having the duty determined by the duty determining unit is configured to be output to the one element, and the other element is alternately arranged with the one element when the on / off signal is applied to the one element. A drive unit configured to switch between synchronous rectification control for turning on and off and asynchronous rectification control for maintaining the other element in an off state when the on / off signal is applied to the one element;
Have
When the current flowing through the second conductive path is in a predetermined current increasing state or when the voltage of the second conductive path is in a predetermined voltage decreasing state, the driving unit performs the synchronous rectification from the asynchronous rectification control. Switch to control,
The duty determination unit is configured to increase a duty of the on / off signal to a higher duty than a duty determined in the first operation in response to the drive unit switching from the asynchronous rectification control to the synchronous rectification control. An in-vehicle DCDC converter that performs an operation and performs the first operation after the second operation.   The duty determination unit performs the second operation in response to the drive unit switching from the asynchronous rectification control to the synchronous rectification control, and then sets the duty of the on / off signal in the second operation according to the passage of time. The in-vehicle DCDC converter according to claim 1, wherein a third operation that gradually decreases from the increased high duty is performed, and the first operation is performed after the third operation. An output detection circuit that generates a first voltage signal that is a voltage signal corresponding to a value of a voltage applied to the second conductive path or a value of a current flowing through the second conductive path;
The duty determining unit
A differential amplifier circuit that generates a second voltage signal that is a voltage signal obtained by amplifying a difference between the first voltage signal generated by the output detection circuit and a reference voltage;
A triangular wave generating circuit for generating a voltage signal of a predetermined triangular wave;
A non-detection signal is output when the value of the current flowing through the second conductive path is less than a predetermined current threshold or when the value of the voltage applied to the second conductive path is greater than or equal to a predetermined voltage threshold; A detection signal different from the non-detection signal when the value of the current flowing through the second conductive path is equal to or greater than the current threshold or when the value of the voltage applied to the second conductive path is less than the voltage threshold. A detection circuit that outputs
A differential circuit for gradually decreasing the output voltage after raising the output voltage in response to the signal output from the detection circuit being switched from the non-detection signal to the detection signal;
When the second voltage signal generated by the differential amplifier circuit is equal to or higher than a third voltage signal that is an output voltage signal from the differentiation circuit, the second voltage signal is used as a threshold voltage signal, and the third voltage signal The third voltage signal is used as the threshold voltage signal when the threshold voltage signal is equal to or greater than the second voltage signal, and an off signal is output when the triangular wave voltage signal is larger than the threshold voltage signal. A comparison circuit that generates a PWM signal as the on / off signal so as to output an on signal when the voltage signal of the triangular wave is smaller;
Have
A method in which the comparison circuit determines the duty of the PWM signal by comparing the second voltage signal and the voltage signal of the triangular wave is the predetermined control amount determination method.
The operation in which the comparison circuit compares the rising output voltage output from the differentiation circuit with the triangular wave voltage signal to determine the duty of the PWM signal is the second operation,
The operation in which the comparison circuit determines the duty of the PWM signal by comparing the gradually decreasing output voltage output after the rising output voltage from the differentiation circuit with the triangular wave voltage signal is the third operation. The in-vehicle DCDC converter according to claim 2.

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