CN113659830B - Charge pump circuit with dynamically adjusted output voltage - Google Patents

Abstract

The invention discloses a charge pump circuit for dynamically adjusting output voltage, which relates to the field of power supply, wherein an input power supply end of a charge pump driving circuit in the charge pump circuit is connected with high-voltage input voltage and is also connected with an input ground end of the charge pump driving circuit through a capacitor, a feedback resistor is bridged between the input power supply end and the input ground end of the charge pump driving circuit, a current sampling circuit samples current of the high-voltage output voltage generated by the charge pump circuit to generate sampling current, the sampling current and reference current are used as the input end of a current amplifier, the output end of the current amplifier is connected with the feedback resistor, a negative feedback loop formed by the current sampling circuit and the feedback resistor carries out negative feedback adjustment on the voltage difference of the charge pump driving circuit according to the output high-voltage output voltage, the output voltage of a charge pump can be stabilized, the current output capability is improved, and the output voltage under light load is avoided to be overhigh.

Description

A Charge Pump Circuit with Dynamic Adjustment of Output Voltage

technical field

The invention relates to the field of power supplies, in particular to a charge pump circuit for dynamically adjusting output voltage.

Background technique

In the actual use of integrated circuits, there is a need for a boost circuit in many cases, that is, a circuit that can make the output voltage higher than the input voltage. Existing non-isolated boost circuits are generally divided into two categories, BOOST converters and charge pumps. The BOOST converter and its similar circuits use the magnetic energy storage capacity of the inductor to sequentially increase the output voltage to a level higher than the input voltage, but the disadvantage of this type of circuit is the need for an inductor, whether it is directly using a separate inductor or using a SIP to convert the inductor Together with integrated circuit packaging, additional processes are required, and the operation is complicated and has additional costs. The charge pump circuit uses capacitors to transport charges step by step to obtain an output voltage higher than the input voltage. In most processes, capacitors can be directly integrated on-chip, so no additional process is required. In light-load applications, charge pumps are a better choice.

The existing common charge pump circuits are shown in Figures 1 and 2. Figure 1 is a dickson charge pump, and Figure 2 is a double cross-couple charge pump. However, the output voltage of these conventional charge pumps is a fixed value and cannot be changed. If both Larger current output capability is required, and the maximum voltage of the charge pump is limited, so the only option is to increase the flying capacitor C _FLY (fly capacitor), which consumes a huge area on the chip.

Contents of the invention

Aiming at the above-mentioned problems and technical demands, the present inventor proposes a charge pump circuit for dynamically adjusting the output voltage. The technical solution of the present invention is as follows:

A charge pump circuit with output voltage dynamically adjusted, the charge pump circuit includes a charge pump drive circuit, the charge pump drive circuit includes a flying capacitor, the input power terminal HVDD of the charge pump drive circuit is connected to a high-voltage input voltage V _IN , and the charge pump drive circuit The input power terminal HVDD is also connected to the input ground terminal HGND of the charge pump drive circuit through the capacitor _C1 , and the output terminal of the charge pump drive circuit is used as the output terminal of the charge pump circuit to output the high voltage output voltage V _CP ;

The feedback resistor R _REG is connected between the input power supply terminal and the input ground terminal of the charge pump drive circuit. The current sampling circuit performs current sampling on the high-voltage output voltage V _CP to generate the sampling current I _SNS . The sampling current I _SNS and the reference current I _REF are used as The input end of the current amplifier, the output end of the current amplifier is connected to the feedback resistor R _REG ;

The magnitude of the output high-voltage output voltage V _CP is positively correlated with the voltage difference V _HVDD -V _HGND between the input power supply terminal and the input ground terminal of the charge pump drive circuit. The negative feedback loop formed by the current sampling circuit and the feedback resistor, according to the output high-voltage output voltage V _CP Negative feedback regulation is performed on the voltage difference V _HVDD -V _HGND .

Its further technical solution is that the current sampling circuit includes a sampling resistor R _SNS and a switch tube M1, one end of the sampling resistor R _SNS is connected to the output terminal of the charge pump circuit, the other end is connected to the source of the switch tube M1, and the gate of the switch tube M1 is Connected to the high-voltage input voltage V _IN , the drain of the switch tube M1 is connected to the input terminal of the current amplifier and outputs the sampling current I _SNS .

Its further technical solution is that the charge pump circuit further includes a zener diode D ₁ , the cathode of the zener diode D ₁ is connected to the input power terminal of the charge pump drive circuit, and the anode is connected to the input ground terminal of the charge pump drive circuit.

Its further technical solution is that the input ground terminal of the charge pump drive circuit is connected to the source of the switch tube M2, the drain of the switch tube M2 is grounded, the output terminal of the current amplifier and the common terminal of the feedback resistor R _REG and the Zener diode _D1 The anodes are all connected and connected to the gate of the switching tube M2, and connected to the input ground terminal of the charge pump driving circuit through the switching tube M2.

Its further technical solution is that the charge pump drive circuit includes X-level cascaded pump group branches inside, each pump group branch includes a first flying capacitor and a second flying capacitor connected through a cross-coupling circuit, and each pump group branch The circuit is cascaded in sequence through the voltage input terminal and the voltage output terminal. The voltage input terminal of the first-stage pump group branch is connected to the input power supply terminal of the charge pump drive circuit, and the voltage output terminal of the last-stage pump group branch circuit is used as the charge pump drive circuit. the output terminal;

The clock signal is connected to the first flying capacitor in each pump group branch through the first floating inverter, and the clock signal is connected to the first flying capacitor in each pump group branch through the second floating inverter and the third floating inverter connected in series. Two flying capacitors, the clock signals obtained by the two flying capacitors in each pump group branch are opposite; the input power supply terminal of the charge pump drive circuit is connected to the power supply of the first floating inverter, and the input ground terminal of the charge pump drive circuit is connected to Ground for the three floating inverters.

Its further technical solution is that the charge pump circuit also includes a voltage switching circuit, the input end of the voltage switching circuit is connected to the high-voltage input voltage V _IN and the low-voltage power supply V _DD , and the output end of the voltage switching circuit is connected to the input power end of the charge pump driving circuit; When V _IN >V _DD , the voltage switching circuit outputs the high-voltage input voltage V _IN ; when V _IN ≤ V _DD , the voltage switching circuit outputs the low-voltage power supply V _DD .

The beneficial technical effect of the present invention is:

This application discloses a charge pump circuit with dynamically adjusted output voltage. In the charge pump circuit, the negative feedback loop formed by the current sampling circuit and the feedback resistor can stabilize the output voltage of the charge pump, improve the current output capability and avoid light The output voltage under load is too high. The output voltage of the charge pump can be changed by adjusting the supply rail voltage of the floating inverter, which is easy to control and high in efficiency. In addition, a voltage switching circuit is added, through which the input voltage provided to the charge pump driving circuit can be switched, ensuring that the output voltage of the charge pump is still normal when the high-voltage input voltage V _IN is low.

Description of drawings

Fig. 1 is the circuit structure of the existing conventional dickson charge pump.

Fig. 2 is the circuit structure of an existing conventional double cross-couple charge pump.

FIG. 3 is a schematic circuit structure diagram of an embodiment of the charge pump circuit of the present application.

FIG. 4 is a schematic diagram of the circuit structure of the charge pump driving circuit in FIG. 3 .

Detailed ways

The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

The present application discloses a charge pump circuit for dynamically adjusting the output voltage. Please refer to FIG. 3. The charge pump circuit includes a charge pump drive circuit. The charge pump drive circuit includes flying capacitors. The input voltage V _IN , the input power terminal HVDD of the charge pump drive circuit is also connected to the input ground terminal HGND of the charge pump drive circuit through the capacitor _C1 , and the output terminal of the charge pump drive circuit is used as the output terminal of the entire charge pump circuit to output a high-voltage output voltage V _CP .

In an open-loop charge pump circuit, the difference between the ideal high voltage output V _{CP_ideal} and the high voltage input voltage V _IN is the voltage increment ΔV generated by the charge pump drive circuit, V _{CP_ideal} =V _IN +ΔV. The output current capability of the charge pump circuit is I _OUT =(V _{CP_ideal} -V _CP )×C _FLY ×f _CP , where C _FLY is the capacitance of the flying capacitor inside the charge pump drive circuit, f _CP is the oscillation frequency, and the output current capability I _OUT is proportional to the voltage difference between the ideal high voltage output V _{CP_ideal} and the actual high voltage output voltage V _CP . Therefore, if a larger current needs to be output, it is necessary to increase the voltage increment ΔV generated by the charge pump driving circuit.

In this application, as shown in FIG. 4, the charge pump drive circuit includes X-level cascaded pumping branches, and each pumping branch includes a first flying capacitor C FLY1 and a second flying capacitor C _FLY1 connected through a cross-coupling circuit. Capacitor C _FLY2 , the capacitances of the two flying capacitors are equal. Each pump group branch is cascaded sequentially through the voltage input terminal and the voltage output terminal. The voltage input terminal of the first-stage pump group branch is connected to the input power supply terminal HVDD of the charge pump drive circuit to obtain V _HVDD . The last-stage pump group branch The voltage output terminal serves as the output terminal of the charge pump driving circuit to output the high voltage output voltage V _CP .

The clock signal CLK is connected to the first flying capacitor C _FLY1 in each pump group branch through the first floating inverter V1, and the clock signal CLK is connected to each pump group branch circuit through the second floating inverter V2 and the third floating inverter V3 in sequence. For the second flying capacitor C _FLY2 in the pump group branch, the clock signals obtained by the two flying capacitors in each pump group branch are opposite. The input power terminal HVDD of the charge pump driving circuit is connected to the power supply V _HVDD of the first floating inverter V1, and the input ground terminal HGND of the charge pump driving circuit is connected to the grounds of the three floating inverters V1, V2, V3. A level conversion circuit is usually connected between the clock signal CLK and the floating inverter.

Specifically, each cross-coupling circuit includes two NMOS transistors MN1 and MN2 and two PMOS transistors PN1 and PN2, the drains of MN1 and MN2 are connected and used as voltage input terminals, the source of MN1, the source of PN1, and the The gate is connected to the gate of PN2, the source of MN2 is connected to the source of PN2, the gate of MN1 is connected to the gate of PN1, and the drains of PN1 and PN2 are connected as voltage output terminals. The positive pole of the first flying capacitor C _FLY1 is connected to the gates of MN2 and PN2, the negative pole is connected to the first floating inverter V1, the positive pole of the second flying capacitor C _FLY2 is connected to the gates of MN1 and PN1, and the negative pole is connected to the third floating inverter V3.

Based on the charge pump drive circuit with the circuit structure shown in Figure 4, the voltage of the flying capacitor of each pump group branch is fully charged at V _HVDD -V _HGND , so the voltage increment ΔV _FLY generated by each pump group branch =V _HVDD -V _HGND , the entire charge pump drive circuit includes X-level pump group branches, so the voltage increment ΔV=X×ΔV _FLY generated by the entire charge pump drive circuit, so under the same capacitance area, by increasing the charge The number of stages X of the pump group branch in the pump drive circuit can output a relatively large current.

But this will bring another problem, that is, if the output load is empty, the output voltage will be very high, which will make it difficult to balance the power supply capacity of the charge pump and the target output voltage. In order to solve this problem, the charge pump circuit of the present application also includes a negative feedback loop formed by a current sampling circuit and a feedback resistor R _REG . The feedback resistor R _REG is connected between the input power terminal HVDD and the input ground terminal HGND of the charge pump driving circuit. The current sampling circuit performs current sampling on the high-voltage output voltage V _CP to generate the sampling current I _SNS , the sampling current I _SNS and the reference current I _REF are used as the input terminal of the current amplifier, _ISNS is connected to the negative input terminal of the current amplifier, and I _REF is connected to the terminal of the current amplifier The positive input terminal and the output terminal of the current amplifier are connected to the feedback resistor R _REG .

In this application, the voltage increment ΔV generated by the charge pump drive circuit is positively correlated with the voltage difference V _HVDD -V _HGND between the input power supply terminal HVDD and the input ground terminal HGND of the charge pump drive circuit, so that the output high voltage output voltage V _CP is It is positively related to the voltage difference V _HVDD -V _HGND between the input power terminal and the input ground terminal of the charge pump driving circuit. The negative feedback loop formed by the current sampling circuit and the feedback resistor performs negative feedback on the voltage difference V _HVDD -V _HGND according to the output high voltage output voltage V _CP . When the high voltage output voltage V _CP is too high, the negative feedback loop makes the voltage difference V _HVDD -V _HGND decreases, thereby reducing the high-voltage output voltage V _CP , stabilizing the output voltage, and obtaining the expected output voltage at light loads.

V_GS是开关管M1的栅源电压，由此可以得到电压差V_HVDD-V_HGND＝(I_REF-I_SNS)×A_I×R_REG，A_I是电流放大器的放大倍数，当高压输出电压V_CP过高时，电压差V_HVDD-V_HGND降低继而使V_CP降低。As shown in Figure 3, the current sampling circuit includes a sampling resistor R _SNS and a switch tube M1, one end of the sampling resistor R _SNS is connected to the output terminal of the charge pump circuit, the other end is connected to the source of the switch tube M1, and the gate of the switch tube M1 is connected to The high voltage input voltage V _IN , the drain of the switch tube M1 is connected to the input terminal of the current amplifier and outputs the sampling current I _SNS . Sampling current

V _GS is the gate-source voltage of the switch tube M1, from which the voltage difference V _HVDD -V _HGND =(I _REF -I _SNS )×A _I ×R _REG can be obtained, and A _I is the amplification factor of the current amplifier. When the high-voltage output voltage When V _CP is too high, the voltage difference V _HVDD -V _HGND decreases and then V _CP decreases.

In order to protect the floating low-voltage tube from being broken down, the charge pump circuit also includes a zener diode D ₁ , the cathode of the zener diode D ₁ is connected to the input power supply terminal of the charge pump drive circuit, and the anode is connected to the input ground of the charge pump drive circuit Terminal HGND, to ensure that the voltage difference V _HVDD -V _HGND will not exceed the reverse breakdown voltage V _ZENOR of Zener diode D ₁ , so the voltage difference V _HVDD -V _HGND =MAX{(I _REF -I _SNS )×A _I × R _REG , V _ZENOR }. The reverse breakdown voltage V _ZENOR of the Zener diode D ₁ can be 6V, for example, so it can be guaranteed that the voltage difference V _HVDD −V _HGND will not exceed 6V.

Therefore, the final output voltage of the charge pump is V _CP =I _REF ×R _SNS +V _IN +V _GS , and the maximum output current capability is I _OUTMAX =(V _{CP_ideal} -V _CP )×C _FLY ×f _CP =X×V _ZENOR -I _REF ×R _SNS -V _GS ×C _FLY ×f _CP .

In the actual application circuit, as shown in Figure 3, the input ground terminal HGND of the charge pump drive circuit is connected to the source of the switch tube M2, the drain of the switch tube M2 is grounded to GND, the output terminal of the current amplifier is connected to the feedback resistor R _REG Both the common terminal and the anode of the zener diode _D1 are connected and connected to the gate of the switching transistor M2, and connected to the input ground terminal HGND of the charge pump driving circuit through the switching transistor M2.

In addition, in order to ensure that the V _CP voltage can still be established normally when the V _IN voltage is low under abnormal conditions, the charge pump circuit also includes a voltage switching circuit, and the input terminal of the voltage switching circuit is connected to the high-voltage input voltage V _IN and the low-voltage power supply V _DD , the output end of the voltage switching circuit is connected to the input power end of the charge pump drive circuit. The voltage switching circuit outputs the larger of V _IN and V _DD : in normal operation, V _IN >V _DD , the voltage switching circuit outputs high-voltage input voltage V _IN ; under abnormal conditions, V _IN ≤ V _DD , the voltage switching circuit outputs low-voltage power supply V _DD ensures that the output voltage of the charge pump is still normal when V _IN is low. The high voltage input voltage V _IN terminal usually also includes a diode D ₂ .

What is described above is only a preferred embodiment of the present application, and the present invention is not limited to the above examples. It can be understood that other improvements and changes directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims (5)

1. The charge pump circuit with the dynamically adjusted output voltage is characterized by comprising a charge pump driving circuit, wherein a flying capacitor is arranged in the charge pump driving circuit, and the charge pump driving circuitInput power source terminal HVDD of (high voltage direct current) is connected with high voltage input voltage V _IN The input power supply terminal HVDD of the charge pump driving circuit is connected with a capacitor C ₁ The input ground HGND of the charge pump driving circuit is connected, the input ground HGND of the charge pump driving circuit is connected with the source electrode of the switch tube M2, the drain electrode of the switch tube M2 is grounded, and the output end of the charge pump driving circuit is used as the output end of the charge pump circuit to output high-voltage output voltage V _CP ；

Feedback resistance R _REG The current sampling circuit is bridged between an input power supply end of the charge pump driving circuit and a grid electrode of the switching tube M2 and is connected to an input ground end HGND of the charge pump driving circuit through the switching tube M2, and the current sampling circuit outputs voltage V to the high voltage _CP Sampling current to generate sampled current I _SNS The sampling current I _SNS And a reference current I _REF As the input end of the current amplifier, the output end of the current amplifier is connected with the feedback resistor R _REG ；

The output high-voltage output voltage V _CP And the voltage difference V between the input power end and the input ground end of the charge pump driving circuit _HVDD -V _HGND Positive correlation, negative feedback loop formed by the current sampling circuit and the feedback resistor, and output voltage V according to the output high voltage _CP For voltage difference V _HVDD -V _HGND Negative feedback adjustment is performed.

2. The charge pump circuit of claim 1, wherein the current sampling circuit comprises a sampling resistor R _SNS And a switching tube M1, the sampling resistor R _SNS One end of the switching tube M1 is connected with the output end of the charge pump circuit, the other end of the switching tube M1 is connected with the source electrode of the switching tube M1, and the grid electrode of the switching tube M1 is connected with the high-voltage input voltage V _IN The drain electrode of the switching tube M1 is connected to the input end of the current amplifier and outputs the sampling current I _SNS 。

3. The charge pump circuit of claim 1, further comprisingZener diode D ₁ Said Zener diode D ₁ The cathode of the charge pump driving circuit is connected with an input power end of the charge pump driving circuit, the anode of the charge pump driving circuit is connected with the grid of the switch tube M2, and the cathode of the charge pump driving circuit is connected with an input ground end of the charge pump driving circuit through the switch tube M2.

4. The charge pump circuit according to any one of claims 1 to 3, wherein the charge pump driving circuit internally comprises X-stage cascaded pump group branches, each pump group branch comprises a first flying capacitor and a second flying capacitor connected by a cross-coupling circuit, each pump group branch is sequentially cascaded by a voltage input end and a voltage output end, the voltage input end of the first-stage pump group branch is connected with the input power end of the charge pump driving circuit, and the voltage output end of the last-stage pump group branch is used as the output end of the charge pump driving circuit;

the clock signal is connected with the first flying capacitors in each pump unit branch through a first floating phase inverter, the clock signal is connected with the second flying capacitors in each pump unit branch through a second floating phase inverter and a third floating phase inverter which are sequentially connected in series, and the clock signals obtained by the two flying capacitors in each pump unit branch are opposite; and the input power supply end of the charge pump driving circuit is connected with the power supply of the first floating phase inverter, and the input ground end of the charge pump driving circuit is connected with the grounds of the three floating phase inverters.

5. The charge pump circuit according to any of claims 1-3, further comprising a voltage switching circuit, wherein an input terminal of the voltage switching circuit is connected to the high voltage input voltage V _IN And a low voltage power supply V _DD The output end of the voltage switching circuit is connected with the input power end of the charge pump driving circuit; when V is _IN >V _DD While the voltage switching circuit outputs a high-voltage input voltage V _IN (ii) a When V is _IN ≤V _DD The voltage switching circuit outputs a low-voltage power supply V _DD 。

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