JP6971129B2 - Current sense amplifier circuit and switching power supply - Google Patents

Description

The present invention is a current mode control type using a current sense amplifier circuit that detects a current flowing through a first resistor having one end connected to a power supply terminal based on the voltage generated in the first resistor, and a current sense amplifier circuit thereof. Regarding switching power supply.

<First conventional example>
A current mode control type switching power supply device that steps down an input voltage and outputs a constant voltage is configured as shown in FIG. 5, for example (Patent Documents 1, 2, and 3 as similar techniques). This switching power supply device is connected between the first node LX and the first power supply terminal 1 and is controlled to be turned ON / OFF by the drive signal φ1. A second switching transistor MN1 for synchronous rectification of an MOSFET connected between two power supply terminals) 2 and whose ON / OFF is controlled by a drive signal φ2 having the same phase as the drive signal φ1 is provided. L1 is an inductor connected between the first node LX and the output terminal 3, and C1 is an output capacitor connected between the output terminal 3 and the ground terminal 2.

MP2 is a current detection transistor of FIGURE whose drain is connected to the first node LX and whose ON / OFF is controlled in synchronization with the first switching transistor MP1 by the drive signal φ1, and R1 is the source of the transistor MP2 and the first power supply terminal 1. The current detection resistor 4C connected between the transistors and 4C is a current sense amplifier circuit that amplifies the voltage Vd generated in the resistor R1 by dividing the current Isw flowing through the inductor L1 and outputs the current sense voltage Vo.

Reference numeral 5 denotes a control circuit for controlling ON / OFF of the transistors MP1, MP2, and MN1, and includes a drive circuit 51. The drive circuit 51 sets the drive signals φ1 and φ2 to the “L” level by inputting the rising edge of the fixed cycle signal oscillated by the oscillator 52 to the SET terminal, and sets the rising edge of the signal input to the SET terminal. The drive signals φ1 and φ2 are set to the “H” level. Reference numeral 53 denotes an operational amplifier that acts as an error amplifier. By comparing the feedback voltage Vfb obtained by dividing the output voltage Vout output to the output terminal 3 by the resistors Ra and Rb with the reference voltage Vref that sets the target voltage of the output voltage Vout. , Generates an error voltage Verr. Reference numeral 54 denotes a comparator, which compares the current sense voltage Vo output from the current sense circuit 4C with the error voltage Verr, and outputs the comparison result to the RESET terminal of the drive circuit 51 as a reset signal.

In the current sense amplifier circuit 4C, the inverting input terminal is connected to the first power supply terminal 1 via the resistor R2, the non-inverting input terminal is connected to the source of the transistor MP2, and the operational amplifier 41 has a gate at the output terminal of the operational amplifier 41. It includes a control transistor MP3 of the MIMO that is connected, the source is connected to the inverting input terminal of the operational amplifier 41, and the drain is connected to the ground terminal 2 via the resistor R3. The gain of this current sense amplifier circuit 4C is G = Vo / Vd = R3 / R2.

FIG. 6 shows the operation waveform of the switching power supply device of FIG. When the pulse output from the oscillator 52 rises to "H", the drive signal φ1 falls from "H" to "L" by the drive circuit 51, and the transistors MP1 and MP2 are turned on. The drive signal φ2 drops from “H” to “L” early by the dead time, and at this time, the transistor MN1 is turned off. Then, when the transistor MP1 is turned on, a current Isw flows from the first power supply terminal 1 to the inductor L1 via the first node LX, energy is stored there, the capacitor C1 is charged, and the output terminal 3 is also charged. Power is supplied to a load (not shown). Since this current Isw gradually increases according to the inductance of the inductor L1, the current sense voltage Vo output from the current sense amplifier circuit 4C gradually increases according to the current Isw.

On the other hand, the feedback voltage Vfb corresponding to the output voltage Vout is compared with the reference voltage Vref in the operational amplifier 53, and the error voltage Verr (= Vref-Vfb) which is the comparison result is input to the comparator 54. Then, in this comparator 54, the current sense voltage Vo output from the current sense amplifier circuit 4C and the error voltage Verr are compared, and when Vo> Verr, the voltage of the RESET terminal of the drive circuit 51 is changed from "L" to "H". Launch.

As a result, the drive signal φ1 output from the drive circuit 51 rises to “H”, and the transistors MP1 and MP2 are switched from ON to OFF. Further, the drive signal φ2 rises from “L” to “H” with a delay of the dead time, and the transistor MN1 switches from OFF to ON. As a result, the energy stored in the inductor L1 causes the current Isw to flow in the direction of the output terminal 3 and returns to the first node LX via the load and the transistor MN1. After that, the same operation is repeated, and the output voltage Vout is converged to the voltage corresponding to the reference voltage Vref.

<Second conventional example>
Here, as an example for varying the gain G, the current sense amplifier circuit 4D shown in FIG. 7 can be considered. In the current sense amplifier circuit 4D of FIG. 7, four resistors R55 to R58 are inserted and connected between the resistors R3 and the ground terminal 2, and switches SW1 to SW4 for individually short-circuiting the resistors R55 to R58 are connected. doing. The switches SW1 to SW4 are ON / OFF controlled by the 4-bit trim signals D1 to D4 output from the trimming setting circuit 6. Therefore, if the resistance values of the resistors R55 to R58 are appropriately set, 16 kinds of resistance values can be realized by the trim signals D1 to D4, so that the gain G can be changed in 16 ways.

However, in the current sense amplifier circuit 4D of FIG. 7, the ON resistance and temperature characteristics when the switches SW1 to SW4 are composed of transistors affect the gain G. Therefore, in order to reduce this influence, it is conceivable to make the ON resistance of the transistors constituting the switches SW1 to SW4 smaller than the resistance values of the resistors R55 to R58. In this case, the transistors constituting the switches SW1 to SW4 may be made smaller. There is a problem that the size becomes large and the occupied area of the semiconductor integrated circuit becomes large.

<Third conventional example>
On the other hand, as in the current sense amplifier circuit 4E shown in FIG. 8, switches SW11 to SW15 for selecting the connection points of the resistors R3 and R55 to R58 connected in series to the drain of the negative feedback control transistor MP3 are provided, and any one of them is provided. It is also conceivable to take out the current sense voltage Vo from the switches SW11 to SW15 by selecting one by the trimming setting circuit 6. In this case, by configuring the input stage of the subsequent circuit (not shown) that captures the current sense voltage Vo with high impedance, it is possible to prevent current from flowing through the switches SW11 to SW15, and the ON resistance of the switches SW11 to SW15 and the like. The influence of temperature characteristics can be avoided. However, in order to increase the resolution, a large number of switches are required, and there is a problem that the occupied area of the semiconductor integrated circuit becomes large.

<Fourth conventional example>
Further, as in the current sense amplifier circuit 4F shown in FIG. 9, four resistors R59 are connected between the resistor R3 and the ground terminal 2 and controlled by the output of the operational amplifier 41 in the same manner as the negative feedback control transistor MP2. Resistors R45 to R48 are connected between the source of the control transistors MP45 to MP48 and the power supply terminal 1, and the trim transistor MP51 of the polyclonal is connected between the drain of the control transistors MP45 to MP48 and the common connection point of the resistors R3 and R59. It is also conceivable to connect ~ MP54.

In this current sense amplifier circuit 4F, weights are set to the currents IS0, IS5 to IS8 of each path by setting the resistance values of the resistors R2 and R45 to R48 and the sizes of the control transistors MP45 to MP48, and the trim transistors MP51 to MP54 are turned on. By controlling / OFF with the 4-bit trim signals D1 to D4, it is possible to avoid an increase in the number of trim transistors. However, in this example, it is difficult to obtain matching because it is necessary to set weights for the currents IS0 and IS5 to IS8. Further, as the number of bits increases, the current consumption increases.

Japanese Unexamined Patent Publication No. 2006-109689 Japanese Unexamined Patent Publication No. 2010-20355 Japanese Unexamined Patent Publication No. 2016-066113

An object of the present invention is to provide a current sense amplifier circuit capable of avoiding an increase in the size of a transistor, preventing an increase in current consumption, and making it possible to change the gain of a current sense voltage, and a switching power supply device using the same.

In order to achieve the above object, the current sense amplifier circuit of the invention according to claim 1 detects a current flowing through a first resistor having one end connected to a first power supply terminal based on a voltage generated in the first resistor. In the current sense amplifier circuit, the inverting input terminal is connected to the first power supply terminal via the second resistor, and the non-inverting input terminal is connected to the other end of the first resistor, and the output terminal of the transistor. A negative feedback control transistor in which the gate is connected, the source is connected to the inverting input terminal of the operational capacitor, and one end of the third resistor is connected to the drain, and the gate is connected to the output terminal of the operational capacitor, and the source is connected via the fourth resistor. A control transistor connected to the first power supply terminal, a trim transistor having one end connected to the drain of the control transistor and ON / OFF controlled by a trim signal, and a first end connected to the other end of the trim transistor. The fourth resistance is set to the same resistance value as the second resistance, the control transistor is set to the same size as the negative feedback control transistor, and one end of the fifth resistance is set to the third. It is characterized in that it is connected to the other end of the resistor, the other end of the fifth resistor is connected to the second power supply terminal, and the current sense voltage is taken out from the drain of the negative feedback control transistor.
The invention according to claim 2 is a current sense amplifier circuit that detects a current flowing through a first resistor having one end connected to the first power supply terminal based on a voltage generated in the first resistor, wherein the inverting input terminal is a second. An operational amplifier connected to the first power supply terminal via a resistor and having a non-inverting input terminal connected to the other end of the first resistor, and a gate connected to the output terminal of the transistor and the source being the inverting input terminal of the operational amplifier. The negative feedback control transistor connected and the drain is connected to the second power supply terminal via the third resistor, the gate is connected to the output terminal of the operational amplifier, and the source is connected to the first power supply terminal via the fourth resistor. The control transistor includes a trim transistor whose one end is connected to the drain of the control transistor and whose ON / OFF is controlled by a trim signal, and a fifth resistor whose one end is connected to the other end of the trim transistor. The 4 resistance is set to the same resistance value as the 2nd resistance, the control transistor is set to the same size as the negative feedback control transistor, the other end of the 5th resistance is connected to the 2nd power supply terminal, and the second power supply terminal is connected. It is characterized in that a current sense voltage is taken out from the one end of the five-resistor.
According to the third aspect of the present invention, in the current sense amplifier circuit according to the first aspect, N sets of the fourth resistor, the control transistor, the trim transistor, and the fifth resistor are set (N is two or more positives). (Integer) is provided, the other end of the fifth resistor of the first set is connected to the second power supply terminal, and the other end of the fifth resistor of the second set is the end of the fifth resistor of the first set. Connect to one end, ..., connect the other end of the fifth resistor of the Nth set to the one end of the fifth resistor of the N-1 set, and connect the other end of the fifth resistor of the N set. Is connected to the other end of the third resistor.
According to the fourth aspect of the present invention, in the current sense amplifier circuit according to the second aspect, N sets of the fourth resistor, the control transistor, the trim transistor, and the fifth resistor are set (N is two or more positives). integer) is provided, the other end of the first set of the fifth resistor connected to the second power supply terminal, a second set of said fifth resistor of the other end of said first set of said fifth said resistor Connect to one end, ..., connect the other end of the 5th resistor of the N group to the end of the 5th resistor of the N-1 set, and connect the end of the 5th resistor of the Nth set. It is characterized in that it is connected to the other end of the trim transistor of the Nth set and the current sense voltage is taken out from the one end of the fifth resistor of the Nth set.
The invention according to claim 5 is the current sense amplifier circuit according to any one of claims 1 to 4, the trim transistor, characterized in that replacing the fuse is cut by the trim signal ..
In the switching power supply device of the invention according to claim 6, the first switching transistor in which the drain is connected to the first node and the source is connected to the first power supply terminal, and the drain is connected to the first node and the source is the first resistor. A current detection transistor connected to the other end of the transistor and whose ON / OFF is controlled in synchronization with the first switching transistor, a drain connected to the first node, a source connected to a second power supply terminal, and the first switching A second switching transistor whose ON / OFF is controlled complementarily to the transistor, an inductor connected between the first node and the output terminal, and an output connected between the output terminal and the second power supply terminal. The first switching transistor, depending on the capacitor, the current sense amplifier circuit according to any one of claims 1 to 5, the current sense voltage obtained by the current sense amplifier circuit, and the output voltage of the output terminal. It is characterized by including a current detection transistor and a control circuit for controlling ON / OFF of the second switching transistor.

According to the present invention, since the fourth resistance is set to the same resistance value as the second resistance and the control transistor is set to the same size as the negative feedback control transistor, the current flowing through the negative feedback control transistor and the control transistor is the same. By simply selecting the current flowing from the control transistor to the 5th resistor with the trim transistor, the gain of the current sense amplifier circuit can be set to a predetermined value, avoiding the increase in transistor size and increasing the current consumption. Can be prevented.

It is a circuit diagram of the current sense amplifier circuit of 1st Embodiment of this invention of a switching power supply apparatus, and the vicinity thereof. It is a circuit diagram of the current sense amplifier circuit of 2nd Embodiment of this invention of a switching power supply device, and the vicinity thereof. It is a gain characteristic diagram of the current sense amplifier circuit of 1st Embodiment. It is a gain characteristic diagram of the current sense amplifier circuit of 2nd Example. It is a circuit diagram of the 1st conventional example of a switching power supply device. It is an operation waveform diagram of the switching power supply device of FIG. It is a circuit diagram of the current sense amplifier circuit of the 2nd conventional example and its vicinity. It is a circuit diagram of the current sense amplifier circuit of the 3rd conventional example and its vicinity. It is a circuit diagram of the current sense amplifier circuit of the 4th conventional example and its vicinity.

<First Example>
FIG. 1 shows a current sense amplifier circuit 4A of the first embodiment of the present invention of a switching power supply device and a portion in the vicinity thereof. In this current sense amplifier circuit 4A, in addition to the gate of the negative feedback control transistor MP3 of MIMO, the gate of the control transistors MP41 to MNP44 of MIMO having the same size as the negative feedback control transistor MP3 is used for the output terminal of the operational amplifier 41. The source of each transistor MP41 to MP44 is connected to the input terminal 1 via resistors R41 to R44 having the same resistance value as the resistor R2. Further, a series circuit of resistors R3 and R51 to R54 is connected between the drain of the negative feedback control transistor MP3 and the ground terminal 2. Further, to the drain of the control transistors MP41 to MP44, the source of the MIMO trim transistors MP51 to MP54 as a switch whose ON / OFF is set by the 4-bit trim signals D1 to D4 output from the trimming setting circuit 6 is connected. ing. The drain of the transistor MP51 is at the common connection point of the resistors R51 and R52, the drain of the transistor MP52 is at the common connection point of the resistors R52 and R53, and the drain of the transistor MP53 is at the common connection point of the resistors R53 and R54. The drain is connected to the common connection point of the resistors R54 and R3, respectively.

As described above, since the resistors R2 and R41 to R44 are set to the same resistance value and the transistors MP3 and M41 to MP44 are set to the same size, the drain currents IS0 to IS4 of the transistors MP3 and MP41 to MP44 are the same. It has become.

となる。トランジスタＭＰ２のソース電圧Ｖｄは、スイッチトランジスタＭＰ１の出力電流Ｉｓｗに比例する電流であり、その比例係数をαとすると、

で表される。 Therefore, for example, if the trim signals D1 to D4 are [0000], all the transistors MP51 to MP54 are OFF, so that only the current IS0 flows through the resistors R3 and R51 to R64, and the current sense amplifier circuit 4A at this time. Gain G of

Will be. The source voltage Vd of the transistor MP2 is a current proportional to the output current Isw of the switch transistor MP1, and the proportionality coefficient is α.

It is represented by.

By the way, since the resistors R2 and the resistors R41 to R44 have relative variations, and the proportional coefficient α varies depending on the current detecting means for detecting the current Isw, an error occurs in the gain G of the equation (1). Therefore, in this embodiment, the gain G error is eliminated by selecting the ON / OFF combination of the trim transistors MP51 to MP54 from 16 combinations by the trim signals D1 to D4 set by the trimming setting circuit 6. ..

のように最小変動量を設定する。そして、

のように設定しておけば、

によって、ゲインＧを微調整することができる。ＴＲＩＭ[４：１]はトリム信号Ｄ１〜Ｄ４で決まる倍率（＝０〜１５のいずれか）である。 At this time, the resistance values of the resistors R3 and R51 to R54 are determined in advance according to the adjustment amount and the adjustment range. For example, when performing linear trimming by the trimming signals D1 to D4,

Set the minimum fluctuation amount as in. and,

If you set it like

Allows the gain G to be fine-tuned. TRIM [4: 1] is a magnification (any of 0 to 15) determined by the trim signals D1 to D4.

FIG. 3 shows the characteristics of the current sense voltage Vo by finely adjusting the gain G. This current sense voltage Vo increases in proportion to the increase in the output current Isw, but the current sense voltage Vo with a gain corresponding to the setting of the trim signals D1 to D4 can be taken out. When the data D1 to D4 are [0000], only the current IS0 flows, so the gain G is the lowest (the gradient of the current sense voltage Vo is the minimum), and when the data D1 to D4 are [1111], all the currents IS0 to IS4 flow, so the gain G Is the highest (the slope of the current sense voltage Vo is the highest). The smaller the resistance value of the reference resistor R51, the finer the gain adjustment becomes possible.

<Second Example>
FIG. 2 shows the current sense amplifier circuit 4B of the second embodiment of the switching power supply device of the present invention and a portion in the vicinity thereof. In the current sense amplifier circuit 4B of this embodiment, only the resistor R3 is connected to the drain of the negative feedback control transistor MP3, and the resistors R51 to R54 are connected in series to the drain of the control transistor M54. The connection relationship of the drains of the transistors MP51 to MP54 with respect to the resistors R51 to R54 and the rest are the same as those in the first embodiment.

のように、式（５）における抵抗Ｒ３０がなくなった形となる。したがって、トリム信号Ｄ１〜Ｄ４が［００００］のときは、電流ＩＳ１〜ＩＳ４が流れないので、ゲインＧの最低値を０とすることができる。図４にこのゲインＧの微調整による電流センス電圧Ｖｏの特性を示した。 The gain G of the current sense amplifier circuit 4B in this embodiment is

As shown in the above, the resistance R30 in the equation (5) is eliminated. Therefore, when the trim signals D1 to D4 are [0000], the currents IS1 to IS4 do not flow, so that the minimum value of the gain G can be set to 0. FIG. 4 shows the characteristics of the current sense voltage Vo by finely adjusting the gain G.

<Other Examples>
In the current sense amplifier circuits of the first and second embodiments, the trim transistors MP51 to MP54 can be replaced with a fuse that cuts off when the 4-bit trim signals D1 to D4 become “0”. Further, although the above has been described with an example in which the gain can be finely adjusted by the 4-bit trim signals D1 to D4, the number of bits is arbitrary. Further, the current sense amplifier circuits of the first and second embodiments can be applied for current detection other than the switching power supply device.

1: Power supply terminal, 2: Ground terminal, 3: Output terminal, 4A-4F: Current sense amplifier circuit, 41: Operational amplifier, 5: Control circuit, 51: Drive circuit, 52: Oscillator, 53: Operational amplifier, 54: Comparator, 6: Trimming setting circuit

Claims (6)

In a current sense amplifier circuit that detects a current flowing through a first resistor having one end connected to the first power supply terminal based on the voltage generated in the first resistor.
An operational amplifier whose inverting input terminal is connected to the first power supply terminal via a second resistor and whose non-inverting input terminal is connected to the other end of the first resistance, and an operational amplifier whose gate is connected to the output terminal of the operational amplifier and whose source is the above. A negative feedback control transistor connected to the inverting input terminal of the operational amplifier and one end of the third resistor connected to the drain, and a gate connected to the output terminal of the operational amplifier and the source connected to the first power supply terminal via the fourth resistor. The control transistor is provided with a trim transistor having one end connected to the drain of the control transistor and ON / OFF controlled by a trim signal, and a fifth resistor having one end connected to the other end of the trim transistor.
The fourth resistance is set to the same resistance value as the second resistance, the control transistor is set to the same size as the negative feedback control transistor, and one end of the fifth resistance is connected to the other end of the third resistance. The current sense amplifier circuit is characterized in that the other end of the fifth resistor is connected to the second power supply terminal and the current sense voltage is taken out from the drain of the negative feedback control transistor. In a current sense amplifier circuit that detects a current flowing through a first resistor having one end connected to the first power supply terminal based on the voltage generated in the first resistor.
An operational amplifier in which an inverting input terminal is connected to the first power supply terminal via a second resistor and a non-inverting input terminal is connected to the other end of the first resistor, and a gate is connected to an output terminal of the operational amplifier to generate a source. A negative feedback control transistor connected to the inverting input terminal of the operational amplifier and the drain connected to the second power supply terminal via the third resistor, and the gate connected to the output terminal of the operational amplifier and the source connected to the second power supply terminal via the fourth resistor. 1 A control transistor connected to a power supply terminal, a trim transistor whose one end is connected to the drain of the control transistor and whose ON / OFF is controlled by a trim signal, and a fifth resistor whose one end is connected to the other end of the trim transistor. And with
The fourth resistance is set to the same resistance value as the second resistance, the control transistor is set to the same size as the negative feedback control transistor, and the other end of the fifth resistance is connected to the second power supply terminal. A current sense amplifier circuit, characterized in that a current sense voltage is taken out from the one end of the fifth resistor. In the current sense amplifier circuit according to claim 1,
N sets (N is a positive integer of 2 or more) of the fourth resistor, the control transistor, the trim transistor, and the fifth resistor are provided, and the other end of the fifth resistor of the first set is the second. Connect to the power supply terminal, connect the other end of the fifth resistor of the second set to the one end of the fifth resistor of the first set, ..., The other of the fifth resistor of the Nth set. A current sense amplifier characterized in that the end is connected to the one end of the fifth resistor of the N-1 set, and the end of the fifth resistor of the N set is connected to the other end of the third resistor. circuit. In the current sense amplifier circuit according to claim 2,
N sets (N is a positive integer of 2 or more) of the fourth resistor, the control transistor, the trim transistor, and the fifth resistor are provided, and the other end of the fifth resistor of the first set is the second. Connect to the power supply terminal, connect the other end of the fifth resistor of the second set to the one end of the fifth resistor of the first set , ..., The other of the fifth resistor of the Nth set. The end is connected to the one end of the fifth resistor of the N-1 set, the end of the fifth resistor of the Nth set is connected to the other end of the trim transistor of the Nth set, and the Nth A current sense amplifier circuit characterized in that the current sense voltage is taken out from the one end of the fifth resistor of the set. In the current sense amplifier circuit according to any one of claims 1 to 4.
Current sense amplifier circuit, characterized in that the trim transistors were replaced with fuse cut off by the trim signal. A first switching transistor whose drain is connected to the first node and whose source is connected to the first power supply terminal.
A current detection transistor in which the drain is connected to the first node, the source is connected to the other end of the first resistor, and ON / OFF is controlled in synchronization with the first switching transistor.
A second switching transistor in which the drain is connected to the first node, the source is connected to the second power supply terminal, and ON / OFF is controlled in a complementary manner to the first switching transistor.
An inductor connected between the first node and the output terminal,
An output capacitor connected between the output terminal and the second power supply terminal,
The current sense amplifier circuit according to any one of claims 1 to 5.
A control circuit that controls ON / OFF of the first switching transistor, the current detection transistor, and the second switching transistor according to the current sense voltage obtained by the current sense amplifier circuit and the output voltage of the output terminal.
A switching power supply that is characterized by being equipped with.

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