CN114614557A

CN114614557A - Multi-power supply switching circuit

Info

Publication number: CN114614557A
Application number: CN202210257951.1A
Authority: CN
Inventors: 李威; 王涛; 杜涛; 罗和平
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2022-03-16
Filing date: 2022-03-16
Publication date: 2022-06-10

Abstract

The invention belongs to the technical field of electronic circuits, and provides a multi-power supply switching circuit which is characterized by comprising the following steps: (1) from a power supply V_DDAnd a back-up power supply V_BAKPower supply V obtained by parallel connection of diodes_HSupplying power to the band-gap voltage reference, the hysteresis comparator and the gating control circuit; (2) designing a bandgap voltage reference to obtain a voltage V_REFProviding stable reference voltage for the rear-stage comparator and the LDO circuit; (3) designing a hysteresis comparator, and adjusting the voltage dividing resistor pair V according to a switching threshold value_DDPerforming partial pressure of_REFComparing to obtain a gating control signal; (4) designing a gating control circuit, and obtaining gating control signals sw1 and sw1 after level shift boosting by using a control signal sw obtained by a hysteresis comparator

Gating the power supply to obtain a supply voltage V_S(ii) a (5) The LDO circuit is designed according to the power supply voltage of the later stage circuit and is powered by a gated power supply V_SFor LDO to proceedSupply power to obtain stable output voltage V_CORE。

Description

Multi-power supply switching circuit

Technical Field

The invention belongs to the technical field of integrated circuits, and particularly relates to a multi-power supply switching circuit.

Background

With the progress of integrated circuit technology and the rapid development of wearable devices and internet of things technology, more and more chips with different types and different applications are provided, and accordingly, more and more level standards and power supply modes are provided. Most of the existing chips in the market only support power supplies or battery power supplies in a small level range, and the chip works abnormally due to accidental power failure of the power supplies or insufficient battery power, or even the whole system generates a risk which is difficult to predict.

The above problems are more demanding on chip design, and therefore, a circuit compatible with a power supply and a battery power supply, which is compatible with a wide range of operating voltages and can provide stable power supply for a subsequent chip, is required. Considering the demand of the integration of the circuit chips, the circuit is required to have higher universality and portability so as to meet the power supply requirements of various chips.

In view of the above requirements, a multi-power supply switching circuit is provided. On the basis of solving the problems, the invention is easy to transplant and integrate into a chip with specific requirements, has a clear circuit structure, and is convenient and practical.

Disclosure of Invention

The invention aims to provide a multi-power supply switching circuit aiming at the defects of the prior art. The circuit comprises two power supply schemes of wide-voltage power supply and backup battery power supply, can be automatically switched to the backup battery power supply after the power supply is abnormally powered down, and can be automatically switched back to the power supply after the power supply is recovered, so that the above and other potential problems in the prior art can be better solved.

A schematic block diagram of a multi-power supply switching circuit is shown in FIG. 1, and for convenience of description, V is shown below_DDPower supply designation, V_BAKReference back-up battery, V_HPower supply of reference control module, V_SDenotes gated supply, V_COREIndicating the power supply output to the subsequent stage circuit. A multi-power supply switching circuit comprising:

(1) power supply module, select V_DDAnd V_BAKThe higher of which supplies power to the control circuit, i.e. V_H；

(2) Bandgap voltage reference circuit of V_HSupplying power to provide accurate and stable V for logic control circuit_REFA reference voltage;

(3) hysteresis comparator circuitRoute, route V_HThe power supply is used for judging whether the power supply voltage is lower than a threshold value or not and outputting a gating control signal sw according to the result;

(4) a gating control circuit which controls the switching between the power supply and the backup battery power supply by using the sw signal obtained in the step (3) to obtain a gated power supply V_S；

(5) LDO circuit of V_sThe power supply provides stable power supply voltage V for the subsequent stage circuit_CORE。

The modules involved in the circuit are discussed in detail below, respectively.

And a power supply module. The power supply module is used for ensuring that the band gap reference circuit, the comparator circuit and the gating control circuit can continuously work under the condition of any power supply. The module is supplied with power by V_DDAnd V_BAKThe higher of which provides the circuit implementation shown in fig. 2. The higher voltage V of the two is obtained by using a diode_HBut due to the diode turn-on voltage drop, V in a typical silicon process_HBelow V_DDAnd V_BAKThe higher is about 0.6V.

A bandgap voltage reference circuit. The band-gap voltage reference circuit is used for providing stable and accurate reference voltage for a multi-power supply switching circuit. The accuracy of the switching threshold and the output voltage are closely related to the accuracy of the band-gap reference, so that higher requirements are put on the temperature drift coefficient of the band-gap reference circuit. The circuit is implemented as shown in FIG. 3, where M₁And M₂Current I flowing through the current mirror and having the same width-to-length ratio₁And I₂The same is true. Bipolar transistor Q₁Size Q₂N times, the difference in base-emitter voltages is proportional to absolute temperature for two bipolar transistors at different current densities, i.e.:

ΔV_BE＝V_Tln n

due to the characteristics of 'virtual short' and 'virtual break' of the operational amplifier, two input ends of the operational amplifier have approximately equal potential and voltage difference delta V_BEActing on R₁Can obtain M₁、M₂And M₃The drain current equation of (a):

the resulting current I₃Is a PTAT (proportional To Absolute temperature) current, i.e. I₃Through a resistance R₂Generating a PTAT voltage I₃R₂This voltage is then applied to the bipolar transistor Q₃On the base-emitter:

wherein V_be，Q3Is a negative temperature coefficient, V_TFor positive temperature coefficient, only the following requirements are met:

the reference voltage V with zero temperature coefficient can be obtained_REF. Based on the above analysis, V was designed based on 0.18um BCD process library in the present invention_REF1.2V bandgap voltage reference. Wherein the resistance R₂The method is realized by connecting a non-silicified n + diffusion region resistor and a non-silicified p + poly resistor in series, so that the PTAT voltage is closer to the temperature coefficient of a base electrode-an emitter electrode. FIG. 4 shows the output V of the bandgap reference circuit_REFThe temperature characteristic curve under FF, TT and SS process angles can be seen from the graph, and V under TT process angle is within the range of-65 ℃ to 125 DEG C_REFThe temperature drift coefficient is 22.78 ppm/DEG C, and the requirement of the circuit can be well met.

A hysteresis comparator circuit. The hysteresis comparator circuit is used for comparing the threshold value and outputting a logic control signal. The comparator circuit is realized by adopting an operational amplifier working in an open-loop state, adopts a classic two-stage operational amplifier structure,as shown in fig. 5. M₁And R₁Obtaining a bias current, M, by a simple bias circuit₂And M₇Mirroring the current. M₃And M₄As differential inputs, suppressing common-mode signal interference, M₅And M₆Constituting a current mirror load. M is a group of₈As a second stage amplifier tube, R₂And C₁And the RC Miller compensation is formed by connecting the input and the output of the second stage. To prevent V_DDThe repeated fluctuation around the threshold causes the comparator output to switch between high and low repeatedly, and the hysteresis effect is generated by introducing negative feedback, namely at V_DDThere are two thresholds for increasing or decreasing. Circuit implementation As shown in FIG. 6, first V_DDObtaining voltage V by dividing voltage with resistor_AAfter a first-stage voltage following enhancement of driving capability is introduced, the voltage is compared with V_REFThe reference voltages are compared. If the sw high level and the sw low level output by the comparator are respectively V_ohAnd V_olThe virtual short and virtual break characteristics of the operational amplifier are obtained as follows:

after simplification, two threshold expressions are obtained:

wherein V_th1Is a V_DDThreshold value of the process of descent, V_th1Is a V_DDThreshold of the ascending process with a threshold width of

If it is assumed that the operational amplifier output can reach rail-to-rail, there

So that it is possible to adjust the resistance R₃And R₄The threshold value is conveniently adjusted. By means of hysteresis comparators, comparing V_DDPartial pressure and V_REFAnd obtaining a gating control signal sw according to the reference voltage.

A gate control circuit. The gating control circuit has the function of controlling two PMOS (P-channel metal oxide semiconductor) gating by utilizing sw to obtain a power supply voltage V_SAnd supplying power to the subsequent LDO. The power supply module utilizes a diode to obtain a higher voltage V of the two_HV due to the diode conduction voltage drop_HBelow V_DDAnd V_BAKThe higher is about 0.6V. The hysteresis comparator is composed of_HThe high level of a gating control signal sw output by the power supply is also lower than V_DDAnd V_BAKThe higher is about 0.6V. If it is to be V_HThe level standard sw signal is directly applied to the PMOS gate to gate V_DDAnd V_BAKOne of which turns off the other. The switched-off PMOS gate-source voltage V_gsThe voltage of-0.6V makes PMOS unable to turn off completely and generate current reverse flow, and the continuous reverse flow current has a risk of damaging the circuit and also affects the service life of the battery.

Therefore, a level shift circuit is introduced to solve the current back-flow problem, and the level shift circuit is shown in FIG. 7 and is used for shifting the level of the gating control signal sw from V_HIs lifted to V_SEliminating the PMOS gate-source voltage difference V of one turn-off path_gsThereby solving the problem of current back-flow. Level shift circuit composed of V_SSupply power, in turn control V_SThus, it is necessary to analyze V with emphasis_SThe establishment procedure of (1). V_SSet up instant-due output control signals sw1 and

are pulled down by resistors, two PMOS circuits are conducted, V_SThe rise in potential causes sw1 and

changing from the same low level to opposite signal, thereby only gating one power supply to obtain stable V_S. The level shift circuit adopts a cross coupling structure to have positive feedback, so that the gating control signals sw1 and sw1 are accelerated

Is generated, quickening V_SThe establishment procedure of (1).

Since the PMOS for gating needs a larger width-to-length ratio, a larger gate capacitance is brought, and in order to guarantee the switching rate of the power supply, the gate control signals sw1 and sw1 are used

Before output, multi-stage buffers are needed to improve the driving capability step by step, and finally the control signals sw1 and sw1 are output

Gate to PMOS to get V_SAs shown in fig. 8. A schematic block diagram of a multi-power supply switching circuit with increased level shift is shown in fig. 9.

An LDO circuit. The LDO circuit is used for converting V_SConversion of supply voltage to stable V_COREThe voltage is used by the circuit of the later stage. The LDO of the present invention refers to classical LDO circuits, which comprise a bandgap voltage reference, which has been discussed in detail above, and a control loop, whose main function is to monitor the output and introduce negative feedback to maintain the output within a small range without changing with the environment and other conditions. The control loop mainly comprises:

(1) an error amplifier for detecting and generating an error correction signal;

(2) a feedback network to detect the output;

(3) the power switch tube is used for adjusting and conducting load current from the non-stabilized input end to the stabilized output end.

The basic block diagram of LDO of the present invention is shown in FIG. 10, in which a feedback resistor R is provided₁And R₂For output voltage V_CORESampling, inputting the sampling result to the non-inverting terminal of the error amplifier and V_REFComparing the reference voltages, outputting the comparison result by the error amplifier, and regulating the power switch tube M₁To obtain a stable output voltage. Regulating power switch tube M₁The size of the power supply can adjust the driving capability of the output power supply, and the power supply requirement of a circuit with higher requirement can be set at V_OUTThe end is added with a larger capacitor, so that the voltage V in the power supply switching process can be effectively reduced_OUTIs fluctuating.

The beneficial effects of the invention mainly comprise:

(1) the invention realizes a circuit with multi-power supply switching power supply, and provides a solution for the circuit design of related technical personnel;

(2) the invention has universality, the power supply voltage can be compatible with a wider level range, and for different processes, only the design of each module needs to be adjusted, and the circuit structure does not need to be changed;

(3) the invention has expandability, and can be flexibly modified and expanded according to different design requirements, including but not limited to adjusting R in figure 6₁And R₂Ratio changing switching threshold, adjusting R₃And R₄The ratio changes the comparator threshold; modification of the structure of fig. 8 introduces more power supplies.

Drawings

FIG. 1 is a schematic block diagram of a multi-power supply switching circuit

FIG. 2 is a circuit diagram of a power supply module

FIG. 3 is a circuit diagram of a bandgap reference module

FIG. 4 is a temperature characteristic curve of a bandgap voltage reference circuit

FIG. 5 is a circuit diagram of a comparator

FIG. 6 is a schematic block diagram of a hysteresis comparator

FIG. 7 is a level shift circuit of the gate control circuit

FIG. 8 is a switching circuit of the gate control circuit

FIG. 9 is a schematic block diagram of a multi-power supply switching circuit after increasing level shifting

FIG. 10 is a schematic block diagram of an LDO circuit

FIG. 11 is a simulation effect diagram of example 1

FIG. 12 is a simulation effect diagram of example 2

Detailed Description

The invention is described in further detail below with reference to specific figures and examples:

specific example 1: the power supply rising and falling switching thresholds designed in the embodiment 1 are 2.6V and 2.5V respectively, and the output voltage V is_COREIs 1.8V, and uses power supply V_DDSupply of electricity, V_BAKThe pin is grounded, and the application scene that the power is supplied by a single power supply and the power supply voltage of the chip is 1.8V is simulated. FIG. 11 is a diagram of simulation results of example 1, wherein the simulation is based on 0.18um BCD process library, and the simulation conditions are 25 ℃ and TT process angle. Wherein the power supply V_DDThe voltage is increased from 0V to 5V within 0-100 ms, the voltage is kept at 5V within 100-200 ms, the voltage is decreased from 5V to 0V within 200-300 ms, and the voltage is increased from 0V to 5V within 300-400 ms. As can be seen in FIG. 11, V_DDWhen the voltage rises to 2.6V, V_COREStarting to output a stable 1.8V power supply voltage; v_DDWhen the power is down to 2.5V, V_COREAnd power failure fails. The circuit can convert the voltage in an effective range into stable 1.8V for a subsequent circuit.

Specific example 2: embodiment 2 is based on the circuit of example 1, and is supplied with power by a power supply and a 3V battery simultaneously, and the application scene of dual-power supply is simulated. Simulation conditions and excitation were the same as in example 1, backup power supply V_BAKThe simulation effect graph of example 2 was obtained by increasing from 0V to 3V in 100 to 150ms, as shown in FIG. 12. As can be seen from fig. 12, the gate control signals sw1 and sw1 can be correctly outputted according to the supply voltage variation, when the supply voltage V is_DDAfter reaching the switching threshold of 2.6V, V_COREThe output of 1.8V begins to stabilize. After a 3V backup power supply is accessed, the power supply is automatically switched to V after the power supply is powered down to 2.5V_BAKSupply of electricity, V_COREThe output voltage is kept stable1.8V, after the power supply voltage is recovered to 2.6V, the power supply is automatically switched back to the power supply, and V is_COREThe output voltage can still be kept at 1.8V.

From the simulation results of example 1 and example 2, it can be verified that the present invention can apply the power supply voltage V in a wide range_DDConversion to stable V_COREThe power supply V is used by a post-stage circuit or a chip and can be supplied by double power supplies_DDAnd a back-up power supply V_BAKAutomatic switching, flexible configuration of switching threshold and output voltage, and strong universality and portability.

The foregoing embodiments fully illustrate the technical content essential to the present invention, and those skilled in the art can implement the embodiments according to the description, so that other technical details are not described in detail.

As noted above, only particular embodiments of the invention, any feature disclosed in this specification, unless stated otherwise, may be replaced by alternative features serving an equivalent or specifically similar purpose; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except combinations where mutually exclusive features or steps are present.

Claims

1. A multi-power supply switching circuit at least comprises a power supply module, a band gap voltage reference circuit, a hysteresis comparator circuit, a gating control circuit and an LDO circuit.

2. A multi-power supply switching circuit according to claim 1, comprising a power input port V_DDA backup power input port V_BAKA power supply output port V_COREOne ground port, said V_DDPort and V_BAKWith ports as two power supply inputs, V_COREThe power output port is used for supplying power for the post-stage circuit.

3. A multi-power-supply switching circuit according to claim 1,

the power supply module supplies V_DDAnd V_BAKBy passingThe diodes are connected in parallel to obtain V_HThe power supply supplies power for the band gap voltage reference circuit and the hysteresis comparator circuit;

the band gap voltage reference circuit and the hysteresis comparator circuit are used for monitoring and comparing a power supply V_DDTo obtain V_HControl signal sw in voltage domain.

4. A multi-power-supply switching circuit according to claims 1 and 3,

the gate control circuit drives the sw signal from V through the level shift circuit_HVoltage domain is raised to V_BAKOr V_DDThe voltage domain obtains a gating control signal sw1, the sw1 controls the PMOS gating power supply to obtain a gated power supply V_S。

5. Multiple power supply switching circuit according to one of the preceding claims, characterised in that said V is_DDAnd V_BAKRespectively connected with power supply and battery power supply, and the power supply output V_CORECan be at V_DDAnd the stability is kept under the condition of fluctuation.

6. A multi-power supply switching circuit according to any one of the preceding claims, wherein the circuit configuration is unchanged and can be modified and expanded according to specific circuits, including (1) modifying the gating control circuit to support more power inputs and more complex power management strategies; (2) the resistance ratio is adjusted to adjust the dual power switching threshold.