CN104362846B - A kind of controllable multi-channel output DC-DC inverter of electrifying timing sequence - Google Patents

Abstract

In order to solve the problems, such as that the precision of voltage regulation existing for previous multiple-channel output DC/DC converters is low, electrifying timing sequence is difficult to control, the present invention carries the topological structure for giving a kind of controllable multiple-channel output DC/DC converter switches power supplys of electrifying timing sequence, multiple-channel output DC/DC converter switches power supplys using the present invention possess the independent accurate voltage stabilizing of every road output voltage, the controllable advantage of output voltage electrifying timing sequence.In addition, the multiple-channel output DC/DC converter switches power supply of the present invention also has many advantages, such as that circuit is simple and reliable, component number is few, can be applied in the electrical equipment having higher requirements to output voltage precision and electrifying timing sequence.

Description

A Multi-output DC-DC Converter with Controllable Power-on Sequence

technical field

The invention relates to the field of switching power supplies, in particular to a multi-output DC-DC converter capable of controlling the power-on sequence of output voltages.

Background technique

Current electronic equipment has increasingly stringent requirements on the power supply quality of switching power supplies. For example, for multi-output power supplies, the output voltage of each channel is often required to reach a stability of 1%. At the same time, there are also clear requirements for the power-on sequence of the output voltage. For example, for a +3.3V, 5V and ±12V four-way output power supply system, it is required that the +3.3V core power supply voltage should be started first, followed by the -12V power supply voltage. , and then +5V and +12V were started one after another.

Patent Document 1 (Chinese Patent Publication No.: CN101521460A, a multi-output DC-DC converter) is applied to high-power output occasions, and realizes soft switching through phase-shift adjustment, making the power supply high in efficiency and simple in structure. However, it does not involve multiple output power supplies with low and medium power, nor does it involve multiple output power-on sequence control circuits, and a system structure that achieves accurate voltage regulation for each output. Patent Document 2 (Chinese Patent Publication No.: CN101197540A, a DC converter) by adding soft switching technology and synchronous rectification technology, the power supply has high efficiency, fast dynamic response speed, small ripple, good EMC performance, and reduces the number of magnetic components The quantity increases the power density. However, this document is aimed at a single-output power supply, and the timing control circuit involved therein mainly performs phase-shift control of PWM signals. Patent document 3 (Chinese patent publication number: CN101345479A, digital DC/DC flyback converter without optocoupler isolation and control method) involves multiple outputs, but there is no power-on sequence control circuit, and it is impossible to control each of the multiple outputs. The timing of all the way to build.

It can be seen from the above analysis that the traditional single-chip control multi-output DC/DC converter has only one main PWM control switch in the system, so the multiple output voltages can only be established at the same time, and the power-on sequence control cannot be realized. If you want to realize the power-on control of multiple output voltages, you can only use multiple independent DC/DC converters to combine them together, and then control their start-up time separately. This will cause the entire power supply circuit to be too complicated, which is not suitable for application in small and medium power DC/DC converters whose size and weight are strictly limited. Combining multiple independent DC/DC converters also needs to consider issues such as synchronization and beat frequency interference, which increases the complexity of the design.

Contents of the invention

In order to solve the problems of low voltage stabilization accuracy and difficult control of power-on sequence in previous multi-output DC/DC converters, the present invention proposes a switching power supply suitable for multi-output DC/DC converters, with each output The voltages are independently and accurately regulated, and the output voltage power-on sequence can be controlled.

In order to achieve the above object, the present invention has taken the following technical solutions:

A multi-output DC-DC converter with controllable power-on sequence, including a front-stage DC/DC converter topology circuit, a sequence control circuit 2 to n, and a rear-stage voltage stabilizing circuit 2 to n. The above three parts of the circuit are divided into stages connected in the form of connection; the front-stage DC/DC converter topology circuit converts the input voltage into the front-stage voltage 1 to the front-stage voltage n of multiple outputs isolated therefrom; wherein the front-stage voltage 1 is the main output voltage, and the front-stage The DC/DC converter topology circuit samples the pre-stage voltage 1 and completes the closed-loop control, and the output voltage of this channel is established first; the timing control circuits 2 to n are respectively connected to the pre-stage voltage 2 to n, and through the The setting of the parameters of the sequence control circuit makes the output voltages of each channel after the sequence control circuit lag behind the previous stage voltage 1 for a certain period of time; the rear stage voltage stabilizing circuits 2 to n are respectively connected to the sequence control circuits 2 to n , to stabilize the previous stage voltage with lower stability to a predetermined stability, as the final output voltages 2 to n.

Further, the topology circuit of the pre-stage DC/DC converter is selected according to the requirements of input voltage, output power, volume, weight, and efficiency, and adopts a forward, flyback or push-pull topology circuit.

Further, for low-power applications, the preceding stage DC/DC converter topology circuit adopts the preceding stage DC/DC converter topology circuit controlled by a single PWM.

Further, the timing control circuit is composed of switching tubes Q1, Q2 and their peripheral circuits; the switching tube Q1 is triggered to be turned on by the reference voltage control, and the parallel capacitor is used to make Q1 turn on slowly; after Q1 is turned on, Q2 is triggered to turn on, By connecting capacitors in parallel, Q2 is slowly turned on; after Q2 is fully turned on, the input voltage is gradually established. Wherein, the reference voltage is the input voltage connected to the front end of Q2, or an external control signal, or a reference level inside the power supply.

The beneficial effects of the present invention are: the present invention solves the problems of low voltage stabilization accuracy and difficult control of power-on sequence in previous multi-output DC/DC converters, and the multi-output DC/DC converter switching power supply of the present invention, It has the advantages that each output voltage is independently and accurately regulated, and the power-on sequence of the output voltage can be controlled. In addition, the multi-output DC/DC converter switching power supply of the present invention also has the advantages of simple and reliable circuit and few components, and can be applied to electrical equipment with higher requirements on output voltage accuracy and power-on sequence.

Description of drawings

Fig. 1 is the block diagram of the multi-channel output DC-DC converter with controllable power-on sequence of the present invention;

Fig. 2 is the circuit diagram of the first embodiment of the timing control circuit in the multi-channel output DC-DC converter of the present invention;

Fig. 3 is a waveform diagram of several key points of the timing control circuit of Fig. 2;

Fig. 4 is a circuit diagram of the second embodiment of the timing control circuit in the multi-output DC-DC converter of the present invention.

Detailed ways

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

As shown in Figure 1, the multi-output DC-DC converter with controllable power-on sequence of the present invention can be divided into three parts, and the circuits of the three parts are connected in cascaded form: the first part is a control chip controlled by a single PWM The front-stage DC/DC converter topology circuit, its function is to convert the input voltage into a multi-output pre-stage voltage 1 to pre-stage voltage n isolated from it. The front-stage voltage 1 is also the main output voltage. The front-stage DC/DC converter topology circuit samples the front-stage voltage 1 and completes the closed-loop control, so that the stability of the front-stage voltage 1 reaches 1%, and the output voltage of this channel is the most built first. The front-stage DC/DC converter topology circuit using a single PWM control chip can reduce design complexity and reduce the number of components, and is suitable for small and medium power switching power supplies. The pre-stage voltage 2 to n is controlled by coupling, so its stability cannot reach 1%, and the settling time is consistent with the pre-stage voltage 1.

The second part is timing control circuits 2 to n, through the setting of circuit parameters, each output voltage after passing through the timing control circuit lags behind the previous stage voltage 1 for a certain time. Through this part of the circuit, the control on the establishment timing of the previous stage voltage 2 to the previous stage voltage n is realized.

The third part is the post-stage voltage stabilizing circuit 2 to n, which can stabilize the low-stabilized pre-stage voltage to a stability of 1% as the final output voltage 2 to n.

Among them, the front-stage DC/DC converter topology circuit can be selected according to the requirements of input voltage, output power, volume, weight, efficiency, etc., such as forward, flyback, push-pull topology, etc. For low-power applications, a single PWM-controlled multiple output topology can be used.

Figure 2 shows a specific embodiment of the second part of the multi-output DC/DC converter of the present invention - a timing control circuit, which is mainly composed of switching tubes Q1, Q2 and their peripheral circuits. Q1 is triggered to be turned on by a reference voltage, which can be connected to the input voltage at the front end of Q2, an external control signal, or a reference level inside the power supply. Setting the reference voltage to the same value can ensure a more accurate power-on sequence for multiple outputs. The reference voltage is divided by resistors R1 and R2 to generate a level that can trigger Q1 to turn on. C1 and R2 are connected in parallel. Due to the existence of C1, the voltage across R2 is a slow building process, so Q1 will be turned on after a delay after the reference voltage is supplied. After Q1 is turned on, R4 will be grounded, thereby triggering Q2 to be turned on, and the resistance values of R5 and R4 are set so that it can reliably trigger Q2 to be turned on. C2 is connected in parallel with R5, and the voltage of R5 is also slowly established due to the existence of C2, so that Q2 is turned on slowly, achieving the purpose of soft start. After Q2 is fully turned on, the input voltage gradually builds up.

Accompanying drawing 3 has provided the waveform schematic diagram of each key point in the accompanying drawing 2 circuit. It can be seen that the timing relationship between the output voltage and the input voltage, by adjusting the values of R1, R2, C1 and R4, R5, C2, the delay time t1 and the establishment time t2 of the output voltage can be controlled. Q1 and Q2 can choose MOSFET switching tubes or triodes according to the actual needs of the circuit, and the corresponding driving circuits can be adjusted according to needs. For example, the diode D1 and the resistor R3 in Fig. 2 are used to increase the driving voltage and current of the switch tube of Q1, and to prevent false conduction of Q1 caused by noise or other interference signals. The light switch Q1 in the accompanying drawing 2 is an NPN triode and Q2 is a P channel MOSFET. In practical applications, N-channel, P-channel MOSFETs, NPN or PNP transistors, or other forms of electronic or mechanical control switches can be flexibly selected according to needs. Accompanying drawing 4 is another example of sequential circuit in the present invention.

In the accompanying drawing 2, the switching tube Q1 is an NPN triode, and the switching tube Q2 is a P-channel MOSFET tube; one end of R1 is connected to the reference voltage, the other end is connected to R2, one end of R2 is connected to R1, and the other end is grounded; the reference voltage passes through the resistors R1, The voltage divider of R2, one end of R2 is connected to the base of Q1, the other end is grounded, the capacitor C1 is connected in parallel with R2, and the emitter of Q1 is grounded; the source of Q2 is connected to the input voltage, the drain is connected to the output voltage, and the gate passes through the resistor R4 is connected to the collector of Q1; one end of resistor R5 is connected to the input voltage, the other end is connected to the gate of Q2, and capacitor C2 is connected in parallel with R5; the reference voltage is divided by resistors R1 and R2 to generate a voltage that can trigger Q1 to turn on level; due to the existence of C1, the voltage across R2 is a slow building process, so Q1 will be turned on after a delay after the reference voltage is input, and R4 will be grounded after Q1 is turned on, thus triggering Q2 to conduct Through, set the resistance of R5 and R4, so that it can reliably trigger Q2 to turn on; due to the existence of C2, the voltage of R5 is also slowly established, so that Q2 is turned on slowly, achieving the purpose of soft start.

In the accompanying drawing 4, the switching tube Q1 is a PNP transistor, and the switching tube Q2 is an N-channel MOSFET tube; one end of R1 is connected to the input voltage, the other end is connected to R2, one end of R2 is connected to R1, and the other end is grounded; the input voltage passes through the resistors R1, The voltage division of R2, one end of R2 is connected to the base of Q1, the other end is grounded, the capacitor C1 is connected in parallel with R1, the emitter of Q1 is connected to the output voltage end, the input voltage end is connected to the output voltage end; the collector of Q1 is connected to the The gate of Q2 is connected, the source of Q2 is grounded, the drain of Q2 is connected to the output ground of the output voltage; one end of the resistor R5 is connected to the ground, the other end is connected to the gate of Q2, and the capacitor C2 is connected in parallel with R5; the reference voltage passes through the resistor R1 and R2 divide the voltage to generate a level that can trigger Q1 to turn on; due to the existence of C1, the voltage across R1 is a slow building process, so Q1 will also delay for a period of time after the reference voltage is supplied. , after Q1 is turned on, R4 and the input voltage will be turned on, thereby triggering Q2 to turn on, setting the resistance values of R5 and R4 to make it reliably trigger Q2 to turn on; due to the existence of C2, the voltage of R5 is also slowly established, As a result, Q2 is turned on slowly, achieving the purpose of soft start

The third part of the topological structure of the multi-channel output DC/DC switching power supply given by the present invention—the post-stage voltage stabilizing circuit, the main purpose is to convert the unstable voltage of the pre-stage into an output voltage with a stability within 1%. The post-stage voltage regulator circuit usually chooses a linear power supply. If the output power is large, you can also choose a non-isolated switching power supply.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (8)

1. A multi-channel output DC-DC converter with controllable power-on sequence is characterized in that, the multi-channel output DC-DC converter includes a front-stage DC/DC converter topology circuit and a sequence control circuit 2 to n , post-stage voltage stabilizing circuits 2 to n, the above-mentioned three-part circuits are connected in cascaded form; the front-stage DC/DC converter topology circuit converts the input voltage into the pre-stage voltage 1 to the pre-stage of multiple outputs isolated therefrom Stage voltage n; where the previous stage voltage 1 is the main output voltage, the previous stage DC/DC converter topology circuit samples the previous stage voltage 1, and completes the closed-loop control, and the output voltage of this road is the first to be established; the timing control The circuits 2 to n are respectively connected to the previous stage voltages 2 to n, and by setting the parameters of the sequence control circuit, the output voltages of each channel after the sequence control circuit lag behind the previous stage voltage 1 for a certain time; the sequence control The circuit is composed of switching tubes Q1, Q2 and their peripheral circuits; the switching tube Q1 is triggered by the reference voltage control, and the first capacitor C1 is connected in parallel to make Q1 turn on slowly; after Q1 is turned on, Q2 is triggered to turn on, and the second Capacitor C2 makes Q2 turn on slowly; after Q2 is fully turned on, the input voltage gradually builds up; The stage voltage is stabilized to a predetermined degree of stability as the final output voltage 2 to n; the post-stage voltage stabilization circuit is a linear power supply or a non-isolated switching power supply. 2. The multi-channel output DC-DC converter according to claim 1, characterized in that: the topological circuit of the front-stage DC/DC converter is based on the requirements of the size of the input voltage, the size of the output power, volume weight, and efficiency Choose from forward, flyback, or push-pull topologies. 3. The multi-channel output DC-DC converter according to claim 1, characterized in that: for low-power applications, the front-stage DC/DC converter topology circuit adopts a front-stage DC/DC conversion controlled by a single PWM topology circuit. 4. The multi-output DC-DC converter according to claim 1, wherein the reference voltage is the input voltage connected to the front end of Q2, or an external control signal, or a reference level inside the power supply. 5. The multi-channel output DC-DC converter according to claim 4, characterized in that: the switching tube Q1 is an NPN triode, and the switching tube Q2 is a P-channel MOSFET tube; one end of the resistor R1 is connected to a reference voltage, and the other end is connected to Resistor R2, one end of R2 is connected to R1, and the other end is grounded; the reference voltage is divided by resistors R1 and R2, one end of R2 is connected to the base of Q1, and the other end is grounded, C1 and R2 are connected in parallel, and the emitter of Q1 is grounded; The source is connected to the input voltage, the drain is connected to the output voltage, the gate is connected to the collector of Q1 through the resistor R4; one end of the resistor R5 is connected to the input voltage, the other end is connected to the gate of Q2, and C2 is connected in parallel with R5; The voltage is divided by resistors R1 and R2 to generate a level that can trigger Q1 to turn on; due to the existence of C1, the voltage across R2 is a slow building process, so Q1 will also delay for a period of time after the reference voltage is supplied. It will be turned on, and R4 will be grounded after Q1 is turned on, thereby triggering Q2 to turn on, setting the resistance of R5 and R4 to make it reliably trigger Q2 to turn on; due to the existence of C2, the voltage of R5 is also slowly established, so that Make Q2 turn on slowly to achieve the purpose of soft start. 6. The multi-output DC-DC converter according to claim 5, characterized in that: a diode D1 and a resistor R3 are added between the resistor R2 and the base of Q1, the negative pole of D1 is connected to the base of Q1, and the positive pole Connected to R3; one end of R3 is connected to the positive pole of D1, and the other end is connected to R2; diode D1 and resistor R3 are used to increase the driving voltage and current of Q1 switch tube, and prevent noise or other interference signals from causing Q1 to be misconducted. 7. The multi-output DC-DC converter according to claim 4, characterized in that: the switch tube Q1 is a PNP transistor, the switch tube Q2 is an N-channel MOSFET tube; one end of R1 is connected to the input voltage, and the other end is connected to R2 , one end of R2 is connected to R1, and the other end is grounded; the input voltage is divided by resistors R1 and R2, one end of R2 is connected to the base of Q1, and the other end is grounded, capacitor C1 is connected in parallel with R1, and the emitter of Q1 is connected to the output voltage terminal , the input voltage terminal is connected to the output voltage terminal; the collector of Q1 is connected to the gate of Q2 through the resistor R4, the source of Q2 is connected to the ground, the drain of Q2 is connected to the output ground of the output voltage; one end of the resistor R5 is connected to the ground, and the other end Connected to the gate of Q2, capacitor C2 is connected in parallel with R5; the reference voltage is divided by resistors R1 and R2 to generate a level that can trigger Q1 to be turned on; due to the existence of C1, the voltage across R1 is a slow establishment process, Therefore, Q1 will be turned on after a delay after the reference voltage is input. After Q1 is turned on, R4 will be connected to the input voltage, thereby triggering Q2 to turn on. Set the resistance of R5 and R4 to make it trigger reliably. Q2 is turned on; due to the existence of C2, the voltage of R5 is also slowly established, so that Q2 is turned on slowly, achieving the purpose of soft start. 8. The multi-output DC-DC converter according to claim 7, characterized in that a diode D1 and a resistor R3 are added between the resistor R2 and the base of Q1, the negative pole of D1 is connected to R2, and the positive pole is connected to R3 , one end of R3 is connected to the anode of D1, and the other end is connected to the base of Q1; diode D1 and resistor R3 are used to increase the driving voltage and current of Q1 switch tube, and prevent noise or other interference signals from causing Q1 to be misconducted.