Power unit

Abstract

To raise responsiveness of a step-up operation to increase an output current amount.SOLUTION: A step-up switching power supply unit 2 comprises a series circuit between an inductor 9 and an FET 11 to be connected between an external power supply line and a ground and outputs voltage higher than voltage of the external power supply to an internal power supply line 8. A step-down switching power supply unit 5 comprises: a series circuit between FETs 18 and 19 to be connected between the internal power supply line 8 and the ground; and a series circuit between an inductor 20 and a capacitor 21 and outputs voltage lower than the voltage of the internal power supply line 8. A step-up control unit (3) performs feedforward control of the step-up switching power supply unit, and a step-down control unit (6) performs feedback control of the step-down switching power supply unit. A filter circuit (4) is arranged on an upstream side of the step-down switching power supply unit, comprises the inductor (9) connected in series between the external power supply line and the internal power supply line, and the inductor is also used as the inductor of the step-up switching power supply unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply device that controls the voltage of an external power supply to a predetermined voltage and outputs the controlled voltage. [Background technology]

[0002] For example, in a vehicle, a lower, constant power supply voltage is generated from the voltage of the vehicle battery and supplied to an electronic control unit (ECU) or the like. Circuits that generate this type of power supply voltage include, for example, a series power supply circuit and a step-down switching power supply circuit. In general, a series power supply circuit has a small output voltage ripple but a drawback of low efficiency, while a step-down switching power supply circuit has a high efficiency but a drawback of large output voltage ripple.

[0003] To address this issue, a power supply device has been proposed that reduces power loss in the series power supply circuit and suppresses output voltage ripple by providing a step-down switching power supply circuit upstream of the series power supply circuit. Furthermore, when a step-down switching power supply circuit is provided, switching noise occurs during operation of the power supply circuit. Therefore, a configuration has been proposed that suppresses the adverse effects of switching noise by providing a filter circuit with an inductor upstream of the step-down switching power supply circuit. Furthermore, in this type of power supply device, a configuration that adds a step-up switching power supply circuit to ensure the necessary power supply voltage even when the battery voltage supplied from outside becomes lower than the power supply voltage to be supplied to the power supply target within the electronic control device is proposed, for example, in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-249812 Summary of the Invention [Problem to be solved by the invention]

[0005] The power supply device disclosed in Patent Document 1 performs feedback control for both the step-down and step-up switching power supply circuits, which causes problems such as difficulty in increasing the amount of output current when step-up operation is performed when the input voltage is low, and difficulty in achieving high response in step-up operation.

[0006] The present invention has been made in view of the above circumstances, and its object is to provide a power supply device that has a configuration including a step-down and step-up switching power supply unit, and that can improve the response of the step-up operation and increase the amount of output current. [Means for solving the problem]

[0007] According to the power supply device of claim 1, the step-up switching power supply unit (2) has a series circuit of an inductor (9) and a step-up switching element (11) connected between an external power supply line (7) to which a DC voltage of an external power supply is supplied and ground, and outputs a voltage higher than the voltage of the external power supply to an internal power supply line (8). The step-down switching power supply unit (5) has a series circuit of two step-down switching elements (18, 19) connected between the internal power supply line and ground, and smoothing circuits (20, 21) that smooth and output a voltage output from a common connection point of the step-down switching elements, and outputs a voltage lower than the voltage of the internal power supply line from the smoothing circuit.

[0008] The boost control unit (3) performs feedforward control of the boost switching power supply unit, and the step-down control unit (6) performs feedback control of the step-down switching power supply unit. The filter circuit (4) is arranged upstream of the step-down switching power supply unit and has an inductor (9) connected in series between the external power supply line and the internal power supply line, and the inductor of the filter circuit also serves as the inductor of the step-up switching power supply unit.

[0009] That is, by using feedforward control on the step-up switching power supply unit, the responsiveness of the step-up operation can be improved and the amount of output current can be further increased. Then, by using feedback control on the step-down switching power supply unit located in the subsequent stage, the output voltage of the power supply device can be stably controlled.

[0010] According to the power supply device of claim 2, the boost control unit switches the operation mode of the boost switching power supply unit between a boost-off mode in which the boost switching element is kept off to output the voltage of the external power supply, and a boost switching mode in which the boost switching element is turned on and off to output a voltage higher than the external power supply voltage, thereby enabling boost operation when necessary according to the voltage of the external power supply.

[0011] Specifically, as in the power supply device of claim 3, the boost control unit monitors the voltage of the external power supply, and when it determines that the voltage has dropped below a specified value, it switches the operation mode from the boost-off mode to the boost switching mode, and when it determines that the voltage drop state has been resolved, it switches the operation mode from the boost switching mode to the boost-off mode. This allows the boost operation to be performed when necessary depending on the voltage of the external power supply. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a power supply device according to an embodiment. [Figure 2] A diagram showing the configuration of the A / D converter and PWM generation unit in the boost control unit. [Figure 3] A diagram showing the relationship between the input voltage range and the duty ratio of the PWM signal [Figure 4] A diagram showing the truth table for the output signals of each comparator that makes up the A / D converter and the bubble error correction output. [Figure 5] Timing chart showing the operation of the PWM generation unit DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment will now be described. As shown in Fig. 1, a power supply device 1 of this embodiment includes a step-up switching power supply unit 2, a step-up control unit 3, a filter circuit 4, a step-down switching power supply unit 5, and a step-down control unit 6. The step-up switching power supply unit 2 includes a series circuit of an inductor 9 and a diode 10 connected between an external power supply line 7 and an internal power supply line 8, an N-channel MOSFET 11 connected between the anode of the diode 10 and ground, and a capacitor 12 connected between the cathode of the diode 10 and ground. A capacitor 13 that constitutes a filter circuit 4 is connected between the external power supply terminal and ground. The filter circuit 4 is a π-type, and the inductor 9 and capacitor 12 that constitute the step-up switching power supply unit 2 also serve as the filter circuit 4.

[0014] The power supply device 1 is mounted on, for example, a vehicle, and an external power supply terminal is connected to the vehicle's battery power supply VB. The external power supply terminal is connected to an input terminal of an A / D converter (ADC) 14 that constitutes the boost control unit 3. The output terminal of the A / D converter 14 is connected to an input terminal of a PWM generation unit 15. The PWM generation unit 15, which will be described in detail later, generates a PWM signal based on a signal related to a carrier cycle input from an oscillation circuit (OSC) 16 and a digital value input from the A / D converter 14, and outputs the PWM signal to a drive circuit 17 in the next stage. The drive circuit 17 outputs a signal that drives the gate of a boost switching element FET 11 in accordance with the input PWM signal.

[0015] A series circuit of N-channel MOSFETs 18 and 19 that constitute the step-down switching power supply unit 5 is connected between the internal power supply line 8 and ground. A series circuit of an inductor 20 and a capacitor 21 that serves as a smoothing circuit is connected between a common connection point between these and ground, and this common connection point serves as the output terminal of the power supply device 1.

[0016] A series circuit of resistor elements 22 and 23 constituting the step-down control unit 6 is connected between the output terminal and ground, and their common connection point is connected to the non-inverting input terminal of an error amplifier 24. A reference voltage 25 is applied to the inverting input terminal of the error amplifier 24. The output terminal of the error amplifier 24 is connected to the input terminal of a PWM generation unit 26.

[0017] PWM generation unit 26 compares the level of the triangular wave input from oscillator circuit 27 with the level of the error signal input from error amplifier 24 to generate a PWM signal, which is output to next-stage drive circuits 28U and 28D. Drive circuit 28D receives the PWM signal via a NOT gate 29. Drive circuits 28U and 28D output signals that drive the gates of FETs 18 and 19, which are step-down switching elements, in response to the input PWM signal.

[0018] As shown in FIG. 2, the A / D converter 14 includes a resistor ladder circuit 31 having (N+1) resistor elements R connected in series between an external power supply terminal Vin and ground, and N comparators 32 whose inverting input terminals are sequentially connected to the common connection point of two resistor elements R. In this embodiment, N=19. A common threshold voltage Vth is applied to the non-inverting input terminals of the comparators 32. The output signals of each comparator 32 having the threshold voltage Vth are input to a correction unit 33 that performs bubble error correction. The signal corrected for bubble errors in the correction unit 33 is input to an encoder 34.

[0019] The M-bit data encoded by the encoder 34 is input to the comparator 36 via the register 35 of the PWM generating unit 15. In this embodiment, M=5. That is, the number of bits of the A / D converter 14 is "5." The oscillator circuit 16 includes an oscillator circuit 16C that outputs a signal corresponding to the carrier frequency of PWM control, and an oscillator circuit 16H that outputs a clock signal that is (N+1) times the carrier frequency. The signals from both are synchronized. The signal output by the oscillator circuit 16C is input to the trigger signal output unit 37 and the negative logic reset terminal RST of the (N+1) cycle counter 38. The clock signal output by the oscillator circuit 16H is input to the counter 38 as a counter clock and to two registers 39 and 40 as a latch trigger.

[0020] The oscillator circuit 16C outputs a low-level one-shot pulse signal that resets the counter 38 at the beginning of the carrier cycle. When the trigger signal output unit 37 receives the one-shot pulse signal, it outputs a high-level one-shot pulse signal to the registers 35 and 40. This signal is input to the register 35 as a latch trigger. The M-bit count value of the counter 38 is input to the comparator 36. When the value of the register 35 matches the count value, the comparator 36 outputs a match signal to the register 39. The outputs of the registers 39 and 40 become signals that reset and set the RS latch 41, respectively. Then, a PWM signal is output from the output terminal Q of the RS latch 41.

[0021] Next, the operation of this embodiment will be described. As shown in Figure 3, when the voltage Vin at the external power supply terminal exceeds the specified value of 8V, the power supply device 1 determines that the voltage drop state has been resolved. Therefore, the duty ratio of the PWM signal is set to 0%, and the step-up switching power supply unit 2 does not perform step-up operation. At this time, the step-up switching power supply unit 2 enters step-up off mode, and the voltage Vin is output to the internal power supply line 8 as is.

[0022] The duty ratio is set to 35% when the voltage Vin is in the range of 8V to 7.10V, 40% when it is in the range of 7.10V to 6.75V, and 45% when it is in the range of 6.75V to 6.35V. When it is in the range of 3.55V or less, the duty ratio is set to 80%. In other words, when the voltage Vin falls to 8V or less, it is determined to be in a voltage drop state and the step-up switching power supply unit 2 enters step-up switching mode.

[0023] Here, we will explain the bubble error correction performed by the correction unit 33. The comparator 32 to which the output is directed is designated as 32M, the comparator one stage lower in voltage than comparator 32M is designated as 32L, and the comparator one stage higher in voltage than comparator 32M is designated as 32H. In this case, when the combination of output signals of each comparator is (32L, 32M, 32H) = (0, 0, 1), the corresponding bubble error correction output is set to "0", and for other combinations it is set to "1".

[0024] As shown in FIG. 4, there are conditions ranging from condition (cond) 1, in which all outputs of comparators 32(1) to 32(19) are "1", to condition 20, in which all outputs are "0". If the bubble error correction outputs are BEC1 to BEC19, the bubble error correction outputs corresponding to condition 1 are all "1" for BEC1 to BEC19. For conditions 2 to 19, BEC1, BEC2, ..., BEC19 are sequentially "0", respectively. Encoder 34 encodes each state of conditions 1 to 20 and outputs 5-bit data.

[0025] As shown in FIG. 5, oscillator circuit 16H outputs a clock signal with a frequency of 8 MHz. Oscillator circuit 16C outputs a low-level one-shot pulse signal that resets counter 38 at the beginning of a carrier cycle. The frequency is 400 kHz, and the carrier cycle is 2.5 μs. Trigger signal output unit 37 uses the one-shot pulse signal as a trigger to output a high-level set signal. The set signal sets RS latch 41 via register 40. This causes the PWM signal to rise and clears counter 38 to zero.

[0026] In the figure, the output data of the A / D converter 14 is shown in 4 bits. Also, in this example, for ease of explanation, the data value output corresponding to an input voltage VB=8V is (b0001), and the data value output corresponding to VB=3V is (b1111), which differs from the correspondence table shown in FIG.

[0027] When VB=8V, the data value (b0001) is input to the comparator 36 via the register 35. When the count value of the counter 38 becomes "1", the comparator 36 outputs a match signal, and the RS latch 41 is reset via the register 39. Then, the PWM signal falls. Since the PWM signal is at a high level when the count value is between "0 and 1", the duty ratio is 2 / 20=0.1=10[%] This becomes:

[0028] When VB=3V, the data value (b1111) is input to the comparator 36 via the register 35. When the count value of the counter 38 becomes "1111", the comparator 36 outputs a match signal, and the RS latch 41 is reset via the register 39. The PWM signal is at a high level when the count value is between "0 and 15", so the duty ratio is 16 / 20=0.8=80[%] This becomes:

[0029] The allocation of the duty ratio of the PWM signal to the range of the input voltage Vin varies depending on the encoding logic of the encoder 34. In this embodiment, the clock frequency of the oscillator circuit 16H is set to 20 times the carrier frequency, resulting in a 5% resolution for setting the duty ratio. However, in actual voltage control, it may not be necessary to set the duty ratio in 5% increments, even to the vicinity of 0% or 100%. The correspondence table shown in FIG. 3 is an example of setting the duty ratio for each range of the input voltage Vin that is considered effective in actual voltage control. The duty ratio corresponding to each range is determined by subtracting "1" from the value of "cond" in the truth table shown in FIG. 4 and multiplying the result by 5%.

[0030] In this way, the boost control unit 3 performs feedforward control, generating a PWM signal to drive the gate of the FET 11, thereby performing boost control. In the step-down switching power supply unit 5, which is arranged in the subsequent stage of the step-up switching power supply unit 2, step-down control is performed by feedback control using the step-down control unit 6, and the generated voltage becomes the output voltage of the power supply device 1.

[0031] As described above, according to this embodiment, the step-up switching power supply unit 2 has a series circuit of inductor 9 and FET 11 connected between the external power supply line 7 to which the DC voltage of the external power supply VB is supplied and ground, and outputs a voltage higher than the voltage of the external power supply VB to the internal power supply line 8. The step-down switching power supply unit 5 has a series circuit of FETs 18 and 19 connected between the internal power supply line 8 and ground, and a series circuit of inductor 20 and capacitor 21 that smoothes and outputs the voltage output from their common connection point, and outputs a voltage lower than the voltage of the internal power supply line 8.

[0032] The boost control unit 3 performs feedforward control of the boost switching power supply unit 2, and the step-down control unit 6 performs feedback control of the step-down switching power supply unit 5. The filter circuit 4 is arranged upstream of the step-down switching power supply unit 5 and has an inductor 9 connected in series between the external power supply line 7 and the internal power supply line 8, and the inductor 9 also forms part of the filter circuit 7.

[0033] By performing feedforward control on the step-up switching power supply unit 2, it is possible to improve the responsiveness of the step-up operation and further increase the amount of output current. Then, by performing feedback control on the step-down switching power supply unit 5 located in the subsequent stage, it is possible to stably control the output voltage of the power supply device 1.

[0034] The boost control unit 3 switches the operation mode of the boost switching power supply unit 2 between a boost-off mode in which the voltage of the external power supply is output by keeping the FET 11 off, and a boost switching mode in which a voltage higher than the external power supply voltage is output by turning the FET 11 on and off. Specifically, when it determines that the voltage of the external power supply has dropped below a specified value, the operation mode is switched from the boost-off mode to the boost switching mode, and when it determines that the voltage drop state has been resolved, the operation mode is switched from the boost switching mode to the boost-off mode. This allows boost operation to be performed as needed depending on the voltage of the external power supply.

[0035] (Other embodiments) The oscillator circuit 16H may be divided by 20 to generate a signal corresponding to the carrier frequency. The correspondence relationship between the input voltage range and the duty ratio is not limited to that shown in Fig. 3 and may be changed as appropriate according to individual designs. The same applies to the carrier frequency, etc. The setting resolution of the duty ratio is not limited to 5%, i.e., N is not limited to 19. Bubble error correction may be performed as needed. The switching element is not limited to an N-channel MOSFET. It is not limited to those installed in vehicles.

[0036] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure. [Explanation of symbols]

[0037] In the drawings, 1 is a power supply device, 2 is a step-up switching power supply unit, 3 is a step-up control unit, 4 is a filter circuit, 5 is a step-down switching power supply unit, 6 is a step-down control unit, 7 is an external power supply line, 8 is an internal power supply line, 9 is an inductor, 11 is an N-channel MOSFET, 14 is an A / D converter, 15 is a PWM generation unit, 18 and 19 are N-channel MOSFETs, 20 is an inductor, 21 is a capacitor, 32 is a comparator, 33 is a correction unit, 34 is an encoder, 35 is a register, 36 is a comparator, and 37 is a trigger signal output unit.

Claims

1. a step-up switching power supply unit (2) having a series circuit of an inductor (9) and a step-up switching element (11) connected between an external power supply line (7) to which a DC voltage of an external power supply is supplied and a ground, and outputting a voltage higher than the voltage of the external power supply to an internal power supply line; a boost control unit (3) that performs feedforward control of the boost switching power supply unit; a step-down switching power supply unit (5) including a series circuit of two step-down switching elements (18, 19) connected between the internal power supply line and ground, and a smoothing circuit (20, 21) that smooths and outputs a voltage output from a common connection point of the step-down switching elements, and that outputs a voltage lower than the voltage of the internal power supply line from the smoothing circuit; a step-down control unit (6) that feedback-controls the step-down switching power supply unit; a filter circuit (4) arranged upstream of the step-down switching power supply unit and having an inductor (9) connected in series between the external power supply line and the internal power supply line, The power supply device wherein the inductor of the filter circuit also serves as the inductor of the step-up switching power supply unit.

2. The boost control unit controls the operation mode of the boost switching power supply unit as follows: a boost-off mode in which the boost switching element is kept turned off to output the voltage of the external power supply; 2. The power supply device according to claim 1, wherein the power supply device is switched to either a boost switching mode or a boost switching mode in which the boost switching element is turned on and off to output a voltage higher than the external power supply voltage.

3. the boost control unit monitors the voltage of the external power supply, and when it determines that the voltage has dropped below a specified value, switches the operation mode from the boost-off mode to the boost switching mode; 3. The power supply device according to claim 2, wherein when it is determined that the voltage drop state has been resolved, the operation mode is switched from the boost switching mode to the boost-off mode.

4. The boost control unit includes an A / D converter (14) that performs A / D conversion of the voltage of the external power supply; a PWM generating unit (15) that selects a preset duty ratio based on the A / D converted digital value and generates a PWM signal; 4. The power supply device according to claim 2, wherein the step-up switching element is turned on and off by the PWM signal.

5. The A / D converter a plurality of comparators (32) for comparing the voltage of the external power supply with different conversion thresholds; a correction unit (33) that performs bubble error correction on output signals from the plurality of comparators; 5. The power supply device according to claim 4, further comprising an encoder (34) for encoding the bubble error corrected correction signal and converting it into the digital value.

6. If the number of comparators is N, a clock frequency used for the counter is (N+1) times the frequency at which each of the switching elements is switched; 6. The power supply device according to claim 5, wherein the PWM generating section is capable of adjusting the duty ratio in steps of {100 / (N+1)}%.

7. The PWM generation unit a register (35) for holding the digital value; a trigger signal output unit (37) that outputs a trigger signal for each carrier period of the PWM signal; a counter (38) that starts counting when the trigger signal is output; a comparator (36) that compares the count value of the counter with the digital value and outputs a match signal when the two match, 5. The power supply device according to claim 4, wherein the PWM signal is kept at a high level from the time when the trigger signal is output until the time when the coincidence signal is output.

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