JP2014140269A5

JP2014140269A5 -

Info

Publication number: JP2014140269A5
Application number: JP2013008170A
Authority: JP
Filing date: 2013-01-21
Publication date: 2016-02-12
Anticipated expiration: 2033-01-21

Description

図１０は、ＰＷＭ制御モードとＶＦＭ制御モードとの制御切り換えが可能な電圧モード制御型のスイッチングレギュレータの回路図である。その図１０において、R1、R２は帰還抵抗、１１１は誤差増幅器（AMP）、１１２、１１３はコンパレータ（CMP）、１３０は発振回路、１３１は発振制御回路、１４０はRSフリップフロップ回路、１５０は制御回路、M１０１はスイッチングトランジスタ、M１０２は同期整流トランジスタ、L1はインダクタ、Coは出力コンデンサ、１２０は負荷、１８０は電圧生成回路、INは入力端子、OUTは出力端子、Vｒeｆは第１基準電圧（参照電圧）、Vｒeｆｍは第２基準電圧、LXは接続点である。なお、電圧生成回路１８０は三角波電圧を含むランプ電圧Vｃを生成する機能を有する。 FIG. 10 is a circuit diagram of a voltage mode control type switching regulator capable of switching between PWM control mode and VFM control mode. In FIG. 10, R1 and R2 are feedback resistors, 111 is an error amplifier (AMP), 112 and 113 are comparators (CMP), 130 is an oscillation circuit, 131 is an oscillation control circuit, 140 is an RS flip-flop circuit, and 150 is a control Circuit, M101 is a switching transistor, M102 is a synchronous rectification transistor, L1 is an inductor, Co is an output capacitor, 120 is a load, 180 is a voltage generation circuit, IN is an input terminal, OUT is an output terminal, Vref is a first reference voltage (see voltage), Vrefm the second reference voltage, LX is the connection point. The voltage generation circuit 180 has a function of generating a ramp voltage Vc including a triangular wave voltage.

本発明に係るスイッチングレギュレータは、制御電圧に応じてスイッチングを行うスイッチングトランジスタと、該スイッチングトランジスタのオフ時に整流を行う整流素子と、該スイッチングトランジスタのオン時に入力電圧による充電が行われるインダクタと、該インダクタの励起エネルギーを示す信号と該インダクタの励起エネルギーがゼロまたは小さくなったことを意味する基準電圧との電圧比較を行って該比較結果として状態検出信号を二値信号として出力する第１の電圧比較回路と、第１の定電圧を生成する第１の定電圧回路と、該第１の定電圧よりも高い第２の定電圧を生成する第２の定電圧回路と、前記出力端子の出力電圧を帰還電圧に変換する帰還抵抗部とからなる帰還回路部と、前記帰還電圧と前記参照電圧との電圧比較を行って該比較結果を示す二値の信号を生成して出力する第２の電圧比較回路と、前記帰還電圧と前記参照電圧とが一致するように前記スイッチングトランジスタを制御する制御回路部と、前記第１の電圧比較回路が前記インダクタの励起エネルギーがゼロまたは小さくなったことを意味する信号を検出すると前記第１の定電圧を前記帰還電圧の参照電圧として動作する第１状態からスイッチング動作を停止する第２状態に遷移させ、前記第２電圧比較回路が前記参照電圧よりも前記帰還電圧が低くなったことを検出すると前記第２状態から前記第２の定電圧を前記帰還電圧の参照電圧として動作する第３状態に遷移させ、前記第２の電圧比較回路が前記参照電圧よりも前記帰還電圧が高くなったことを検出すると前記第３状態から前記第１状態に遷移させる状態遷移制御回路と、を有することを特徴とする。 Switching regulator according to the present invention, a switching transistor for switching according to the control voltage, an inductor and a rectifying element for rectifying the off-state of the switching transistor, the charge according to the input voltage during on of the switching transistor takes place, the A first voltage that compares a signal indicating the excitation energy of the inductor with a reference voltage that means that the excitation energy of the inductor is zero or small and outputs a state detection signal as a binary signal as the comparison result A comparison circuit; a first constant voltage circuit that generates a first constant voltage; a second constant voltage circuit that generates a second constant voltage higher than the first constant voltage; and an output of the output terminal A feedback circuit unit comprising a feedback resistor unit for converting a voltage into a feedback voltage, and a voltage ratio between the feedback voltage and the reference voltage A second voltage comparison circuit that generates and outputs a binary signal indicating the comparison result, and a control circuit unit that controls the switching transistor so that the feedback voltage and the reference voltage match. When the first voltage comparison circuit detects a signal indicating that the excitation energy of the inductor is zero or small, the switching operation is performed from the first state in which the first constant voltage is used as a reference voltage of the feedback voltage. When the second voltage comparison circuit detects that the feedback voltage has become lower than the reference voltage, the second constant voltage is changed from the second state to the reference voltage of the feedback voltage. When the second voltage comparison circuit detects that the feedback voltage is higher than the reference voltage, the third state is operated from the third state. And having a state transition control circuit for shifting the state, the.

比較器１１の非反転入力端子＋には帰還電圧FBが入力され、比較器１１の反転入力端子−にはリプル電圧の変動を制御するのに用いる参照電圧Vrefが入力される。その参照電圧Vrefには第１の定電圧Vref1と第２の定電圧Vref2とが用いられる。第１の定電圧Vref1は定電圧回路E1により生成され、その定電圧回路E1もＩＣ内部の定電圧源により構成される。 The feedback voltage FB is input to the non-inverting input terminal + of the comparator 11, and the reference voltage Vref used to control fluctuation of the ripple voltage is input to the inverting input terminal − of the comparator 11. As the reference voltage Vref, a first constant voltage Vref1 and a second constant voltage Vref2 are used. The first constant voltage Vref1 is generated by a constant voltage circuit E1, and the constant voltage circuit E1 is also composed of a constant voltage source inside the IC.

誤差増幅器１２の非反転入力端子＋には参照電圧Vrefが入力され、誤差増幅器１２の反転入力端子−には帰還電圧FBが入力される。参照電圧Vrefは、スイッチSW3によって第１の定電圧Vref1と第２の定電圧Vref2との間で切り替えられる。 The reference voltage Vref is input to the non-inverting input terminal + of the error amplifier 12, and the feedback voltage FB is input to the inverting input terminal − of the error amplifier 12. The reference voltage Vref is switched between the first constant voltage Vref1 and the second constant voltage Vref2 by the switch SW3.

そのスイッチSW3は後述する機能を有する状態遷移回路１４により切り替えられる。すなわち、そのスイッチSW3は、その状態１のときには比較器１１の反転入力端子−と誤差増幅器１２の非反転入力端子＋とに第１の定電圧Vref1が印加され、状態３のときには第２の定電圧Vref2が印加されるように、状態遷移回路１４から出力される状態３遷移信号によって切り替えられる。 The switch SW3 is switched by a state transition circuit 14 having a function described later. That is, when the switch SW3 is in the state 1, the first constant voltage Vref1 is applied to the inverting input terminal − of the comparator 11 and the non-inverting input terminal + of the error amplifier 12, and when the switch SW3 is in the state 3, the second constant voltage Vref1 is applied. Switching is performed by a state 3 transition signal output from the state transition circuit 14 so that the voltage Vref2 is applied.

（状態１）
状態１においては、スイッチSW２は閉成され、スイッチSW3は参照電圧Vrefとしての第１の定電圧Vref１を比較器１１の反転入力端子−に印加しかつ誤差増幅器１２の非反転入力端子＋に印加する側に接続されている。 (State 1)
In the state 1, the switch SW2 is closed, and the switch SW3 applies the first constant voltage Vref1 as the reference voltage Vref to the inverting input terminal − of the comparator 11 and to the non-inverting input terminal + of the error amplifier 12. Connected to the side.

これにより、スイッチSW3は、参照電圧Vrefとしての第２の定電圧Vref２を比較器１１の反転入力端子−に印加し、誤差増幅器１２の非反転入力端子＋に印加する側に接続される。また、スイッチSW2が閉成される。 Thereby, the switch SW3 is connected to the side of applying the second constant voltage Vref2 as the reference voltage Vref to the inverting input terminal − of the comparator 11 and applying it to the non-inverting input terminal + of the error amplifier 12. Further, the switch SW2 is closed.

Ｎ−チャネルトランジスタＮ６は製造で許容される最小のゲート長で構成されており、閾値電圧でオン・オフするスイッチとみなすことができる。一般に、トランジスタの閾値電圧は製造誤差を持っているため、誤差増幅器１２の出力は差動オフセット電圧を持っている。その原因として最も大きいのは、差動対PチャンネルトランジスタＰ４，Ｐ５の閾値電圧のオフセットであり、閾値電圧のオフセット分、反転電圧端子−に差動オフセット電圧が発生する。 The N-channel transistor N6 has a minimum gate length allowed in manufacturing, and can be regarded as a switch that is turned on / off by a threshold voltage. In general, since the threshold voltage of a transistor has a manufacturing error, the output of the error amplifier 12 has a differential offset voltage. The largest cause is the offset of the threshold voltage of the differential pair P-channel transistors P4 and P5, and a differential offset voltage is generated at the inverted voltage terminal − by the offset of the threshold voltage.

状態遷移回路１４が状態３遷移信号を出力している状態にあるとき、差動オフセット電圧を最小にしても問題が発生する可能性があることを図６を参照しつつ説明する。図６は、比較器１１の比較出力電圧ｃｍpoutを反転させる反転入力端子−に印加される電圧が誤差増幅器１２の反転入力端子−の電圧より僅かに高い状態を想定して描かれている。 With reference to FIG. 6, it will be described that a problem may occur even when the differential offset voltage is minimized when the state transition circuit 14 is in a state of outputting a state 3 transition signal. 6, an inverting input terminal for inverting the comparison output voltage cmpout of the comparator 11 - the voltage applied to the inverting input terminal of the error amplifier 12 - are drawn assuming a slightly higher state than the voltage of the.

この図６においては、第１の定電圧Ｖｒｅｆ１に対して比較器１１の反転入力端子−に印加される電圧１が第１の定電圧Ｖｒｅｆ１よりも高く、かつ、第２の定電圧Ｖｒｅｆ２に対して比較器１１の反転入力端子−に印加される電圧２が第２の定電圧Ｖｒｅｆ２よりも高い。 In FIG. 6, the voltage 1 applied to the inverting input terminal − of the comparator 11 with respect to the first constant voltage Vref1 is higher than the first constant voltage Vref1, and with respect to the second constant voltage Vref2. Thus, the voltage 2 applied to the inverting input terminal − of the comparator 11 is higher than the second constant voltage Vref2.

状態１のときには、電圧１よりも帰還電圧FBが小さくなると、比較器１１の比較出力電圧ｃｍpoutが反転する。しかし、状態３のときには、誤差増幅器１２の誤差電圧opoutにより帰還電圧ＦＢが参照電圧Ｖｒｅｆとしての第２の定電圧Vref2に収束していくが、比較器１１の反転入力端子−の電圧２が第２の定電圧Vref2である参照電圧Ｖｒｅｆよりも高い。 In the state 1, when the feedback voltage FB becomes smaller than the voltage 1, the comparison output voltage cmpout of the comparator 11 is inverted. However, in the state 3, the feedback voltage FB converges to the second constant voltage Vref2 as the reference voltage Vref due to the error voltage opout of the error amplifier 12, but the voltage 2 at the inverting input terminal − of the comparator 11 is the second voltage. 2 is higher than the reference voltage Vref which is a constant voltage Vref2.

その結果、状態１、状態２のときには、第１の定電圧Ｖｒｅｆ１に対して比較器１１の反転入力端子−に印加される電圧１が第１の定電圧Ｖｒｅｆ１よりも高い。また、状態３のときには、図７に示すように、第２の定電圧Ｖｒｅｆ２に対して比較器１１の反転入力端子−に印加される電圧２が第２の定電圧Ｖｒｅｆ２よりも低くなる。 As a result, in the state 1 and the state 2, the voltage 1 applied to the inverting input terminal − of the comparator 11 with respect to the first constant voltage Vref1 is higher than the first constant voltage Vref1. In state 3, as shown in FIG. 7, the voltage 2 applied to the inverting input terminal − of the comparator 11 with respect to the second constant voltage Vref2 is lower than the second constant voltage Vref2.

Claims

In the switching regulator that converts the input voltage input to the input terminal into a predetermined output voltage and outputs the load current from the output terminal.
A switching transistor that performs switching according to a control voltage, a rectifying element that performs rectification when the switching transistor is turned off, an inductor that is charged by the input voltage when the switching transistor is turned on, and a signal that indicates excitation energy of the inductor A first voltage comparison circuit that compares a voltage with a reference voltage that means that the excitation energy of the inductor is zero or small and outputs a state detection signal as a binary signal as the comparison result; A first constant voltage circuit for generating a constant voltage; a second constant voltage circuit for generating a second constant voltage higher than the first constant voltage; and converting an output voltage of the output terminal into a feedback voltage. A voltage comparison between the feedback circuit unit composed of a feedback resistor and the feedback voltage and the reference voltage is performed to generate a binary signal indicating the comparison result. A second voltage comparison circuit that outputs the control signal, a control circuit unit that controls the switching transistor so that the feedback voltage and the reference voltage match, and the first voltage comparison circuit has an excitation energy of the inductor. When a signal indicating zero or low is detected, a transition is made from a first state in which the first constant voltage is used as a reference voltage of the feedback voltage to a second state in which a switching operation is stopped, and the second voltage When the comparison circuit detects that the feedback voltage is lower than the reference voltage, the second circuit shifts from the second state to the third state where the second constant voltage operates as a reference voltage of the feedback voltage. When the voltage comparison circuit detects that the feedback voltage has become higher than the reference voltage, the state transition control circuit causes the transition from the third state to the first state. Switching regulator and having a, the.

2. The feedback circuit unit according to claim 1, wherein the feedback circuit unit includes a feedback resistor that converts the output voltage into the feedback voltage, and a speed-up capacitor that passes a high frequency component of the output voltage as the feedback voltage. Switching regulator.

The second voltage comparison circuit includes an error amplifier that operates to converge a difference between the feedback voltage and the reference voltage, and maintains an error signal of the error amplifier constant in the second state. The switching regulator according to claim 1 or 2.

The output terminal of the error amplifier is connected to a phase compensation circuit, the phase compensation circuit including a capacitor, and in the state 2, the capacitor is disconnected from the error amplifier in order to keep the voltage of the capacitor constant. The switching regulator according to claim 3.

5. The switching regulator according to claim 1, wherein at least the control circuit unit is set in a sleep mode in the second state. 6.

The second voltage comparison circuit has an offset voltage, and detects that the feedback voltage is higher than the reference voltage in the third state with a voltage lower by the offset voltage. The switching regulator according to any one of claims 1 to 5.

The switching regulator according to claim 1, wherein the rectifying element is a MOSFET that performs control for preventing a backflow current.

The rectifying element is a diode, and the first voltage comparison circuit detects a signal indicating that the excitation energy is zero or light by detecting that the cathode voltage of the diode becomes a positive voltage. The switching regulator according to any one of claims 1 to 6, wherein the switching regulator is characterized in that

The switching regulator according to claim 1, wherein the switching regulator is controlled in a current mode.

The reference voltage to be compared with the feedback voltage of the output voltage is switched between the first constant voltage and the second constant voltage higher than the first constant voltage, and the feedback voltage is compared with the first constant voltage. A first step of setting the control circuit unit that performs switching control of the inductor current flowing through the inductor to the first state;
A second step of detecting that an inductor current flowing through the inductor is zero or small when the control circuit unit is in the first state and setting the control circuit unit to a second state which is a sleep state;
When the control circuit unit is in the second state, the feedback voltage is compared with the first constant voltage, and when the feedback voltage is lower than the first constant voltage, the reference voltage is set to the first constant voltage. The reference voltage is set when the control circuit unit for switching the inductor current by switching from the constant voltage to the second constant voltage is set to the third state and the feedback voltage becomes higher than the second constant voltage. And switching the second constant voltage to the first constant voltage to repeat the third step of setting the control circuit unit to the first state.