CN102386780A - Push-pull circuit of DC/DC (Direct Current/Direct Current) part - Google Patents

Abstract

The present invention is applicable to the field of electronic circuits, and provides a DC/DC part push-pull circuit, including: a step-up transformer and a primary switch tube, a voltage doubler rectifier circuit connected to the output end of the step-up transformer and the primary switch tube, The output terminals of the voltage doubler rectifier circuit are respectively connected with the output filtering and energy storage circuit and the current detection unit, the output terminals of the filtering and energy storage circuit are connected with the voltage/detection unit, the current detection unit, the voltage/detection unit The output ends of the multi-signal feedback sampling unit are all connected to the multi-signal feedback sampling unit, and the multi-signal feedback sampling unit is connected to the controller. The controller has its own memory and communication interface, and the output end of the controller is connected to the driver. A voltage transformer and a primary switch tube, and the input terminal of the controller is also connected with the input voltage detection unit and the auxiliary power supply. In this way, the output performance index of the digital push-pull circuit, the conversion efficiency of the power supply, and the temperature rise performance index are improved.

Description

A kind of push-pull circuit of DC/DC part

technical field

The invention belongs to the field of electronic circuits, in particular to a push-pull circuit of a DC/DC part.

Background technique

The DC/DC part of the low-power UPS power supply generally adopts a push-pull topology, which converts the lower battery voltage into a bus voltage of about 400V as the input of the subsequent inverter. If only the voltage loop is used to control the output voltage of the push-pull converter, because the load is an inverter, the input current is a low-frequency current fluctuation with twice the inverter frequency. This fluctuation will cause the voltage and current stress of the primary switching tube to be too large, reduce the efficiency of the converter, and increase the temperature rise. In order to avoid these disadvantages, it is necessary to increase the current loop so that the input current is direct current.

Current loop sampling of existing push-pull converters is all on the primary side, and generally includes the following three types: resistive type, Hall current sensor type, and wire-wound type, as shown in Figures 1-3.

Referring to Figure 1, it is a resistive type, which is suitable for occasions with small currents, and the current of the primary switch tube of the push-pull circuit in UPS applications often reaches tens of amperes or even hundreds of amperes. If this method of sampling current is used, the resistance loss is large, and it is necessary to cooperate with a high-precision operational amplifier to amplify the millivolt-level voltage sampling signal, which is easily disturbed by switching noise; the overall cost of large current sampling resistors and high-precision operational amplifiers is relatively low. High; PCB wiring is also more difficult.

Referring to Figure 2, it is a Hall current sensor type. It only needs one sensor to complete the signal required for current sampling, and the loss is small, but the cost is too high, which is almost unacceptable for low-power UPS power supplies with strict cost requirements.

Referring to Figure 3, it is a wire-wound type, which requires magnetic reset and demagnetization time, and its cost is relatively low. The current signal sampling can be better realized under light load. However, when the battery is low voltage and the load is full, because the current signal is close to the full duty cycle, the sensor cannot be effectively demagnetized and reset, so the current loop control cannot be realized in a full range.

To sum up, the current sampling technology of the primary side of the push-pull circuit of the DC/DC part in the existing low-power UPS power supply has the following disadvantages:

1. Resistive sampling has a large loss, complex structure, difficult PCB wiring, and high cost, and is only suitable for occasions with small input currents;

2. The Hall current sensor type can meet the current sampling requirements, but the cost is too high. It is difficult to be practical based on cost considerations;

3. The winding type has the lowest cost. However, it requires a magnetic reset, and the circuit fails when the duty cycle is close to full, and current sampling cannot be realized in a full range.

Contents of the invention

In order to solve the above technical problems, the purpose of the embodiments of the present invention is to provide a push-pull circuit of the DC/DC part.

The embodiment of the present invention is implemented in this way, a push-pull circuit of the DC/DC part, the push-pull circuit includes:

A step-up transformer and a primary switch tube, a voltage doubler rectifier circuit connected to the output end of the step-up transformer and the primary switch tube, the output end of the voltage doubler rectifier circuit is respectively connected to an output filter, an energy storage circuit, and a current detection unit The output terminals of the filter and energy storage circuit are connected to the voltage/detection unit, the output terminals of the current detection unit and the voltage/detection unit are connected to the multi-signal feedback sampling unit, and the multi-signal feedback sampling unit is connected to A controller, the controller has its own memory and communication interface, and the output terminal of the controller is connected to the driver, the driver is connected to the step-up transformer and the primary switch tube, and the input terminal of the controller is also connected to the input voltage The detection unit and the auxiliary power supply are connected.

Further, the power range of the UPS is 500W-3000W.

Further, the input of the digital push-pull circuit is below the battery voltage of 100V, and the output voltage is 400V, which is used as the input voltage of the subsequent inverter.

Further, the working frequency of the digital push-pull circuit is 30kHz-100kHz, and the primary and secondary sides of the transformer are a set of windings with a center tap.

Further, the controller implements digital control function and management function by DSP chip.

Further, the driving circuit is a driving circuit of a MOSFET switching tube, and a power amplification driving circuit is composed of an isolation transformer or a PNP and NPN transistor.

Further, the communication interface is a UART communication interface.

Further, the associated parameter memory is an EEPROM memory chip.

In the embodiment of the present invention, on the basis of low cost, the output performance index of the digital push-pull circuit, the conversion efficiency of the power supply, the temperature rise performance index, etc. are improved, and it is convenient to use and has high commercial practical value.

Description of drawings

Fig. 1 is the schematic diagram of the resistive primary side current sampling provided by the prior art;

Fig. 2 is the principle diagram of the Hall current sensor type primary side current sampling provided by the prior art;

Fig. 3 is a schematic diagram of the wire-wound primary current sampling provided by the prior art;

FIG. 4 is a schematic diagram of secondary current sampling provided by an embodiment of the present invention;

Fig. 5 is a structural block diagram of a digital push-pull circuit for secondary current sampling provided by an embodiment of the present invention;

Fig. 6 is a functional structural block diagram of a controller provided by an embodiment of the present invention;

Fig. 7 is a circuit diagram provided by another embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to Figures 4-7, wherein, Figure 4 shows the secondary current sampling principle provided by the present invention,

The output of the digital push-pull circuit adopts voltage doubler rectification, the current sampling CT1 corresponds to the current of the output inductor L1, and the current sampling CT2 corresponds to the current of the output inductor L2. Because the output is high voltage (about 400V), the sampling current is small (the current of 1KW UPS is only about 3A, and the current of 3KW UPS does not exceed 10A), and two extremely low-cost wire-wound CTs can meet the requirements. The maximum duty cycle of the current flowing in each CT is 50%, and there is sufficient magnetic reset time, which completely avoids the magnetic saturation problem existing in the sampling of the primary winding CT. Compared with the three methods of primary-side high-current sampling, the cost is greatly reduced.

In the present invention, the digital push-pull power supply adopts double-loop control of voltage and current. The voltage and current stress of the primary switch tube have no low-frequency fluctuations. MOSFETs with lower withstand voltages can be selected to further reduce costs. The reduction of voltage and current stress helps to reduce power loss and improve power efficiency. The temperature rise of the primary side MOSFET and transformer has been greatly improved. A fan with a lower rotating speed can be selected, which helps to reduce the cost of the power supply on the one hand, and on the other hand helps to reduce the noise of the power supply.

The output adopts the method of cycle-by-cycle control to achieve voltage stabilization, so the output voltage and current must be sampled at least once in a cycle, and the sampled signal is compared with the reference value inside the controller and then input into the PID control algorithm for calculation. The duty cycle of the next switching cycle. There is a certain dead time between the primary switching tubes, and the dead time can be modified according to the different characteristics of the actual device.

When the output voltage is overvoltage or the output current is overcurrent, the control signal is turned off, and restarts when the detected abnormality disappears during shutdown. The accurate value of output voltage, output overvoltage protection value and output overcurrent protection value can be set online within a certain range according to user needs.

The push-pull circuit of the DC/DC part includes: a step-up transformer and a primary switch tube, a voltage doubler rectifier circuit connected to the output terminals of the step-up transformer and the primary switch tube, and the output terminals of the voltage doubler rectifier circuit are respectively connected to The output filter is connected to the energy storage circuit and the current detection unit, the output end of the filter and energy storage circuit is connected to the voltage/detection unit, and the output ends of the current detection unit and the voltage/detection unit are connected to the multi-signal feedback sampling unit , the multi-signal feedback sampling unit is connected to the controller, the controller has its own memory and communication interface, and the output end of the controller is connected to the driver, and the driver is connected to the step-up transformer and the primary switch tube, so The input terminal of the controller is also connected with the input voltage detection unit and the auxiliary power supply.

Among them, the main power topology includes the primary switching tube, step-up transformer, voltage doubler rectifier circuit and output filter energy storage circuit, which is the main body and hardware foundation of the power supply, and mainly completes the energy conversion and transmission of the power supply, and the voltage with a large transformation ratio Convert and isolate the input and output of the power supply; the functional schematic diagram of the controller is shown in Figure 6. This is the main controller of the module, which completes the output voltage and output current signal sampling to realize double-loop control and protection control, and controller parameter configuration and communication functions; the drive circuit completes the power amplification of the duty ratio signal of the switch tube; the voltage and current detection channel completes the sampling and amplification of the input voltage, output voltage and output current; the feedback and sampling channel receives the signal of the detection channel and analyzes it. Time-sampled and sent to the controller; the auxiliary sources are the primary and secondary controllers, drive circuits, and operational amplifiers of the detection circuit to supply power; the communication interface of the digital push-pull circuit adopts the standard RS232 communication protocol, which can realize the power supply parameters. Online modification; the parameter memory receives the data of the communication interface and updates and saves it, and reads in the parameters for configuration every time the power is turned on.

As an embodiment of the present invention, the push-pull circuit of the DC/DC part can also be shown in FIG. 7 , in this circuit, the current sampling is mainly placed at the ground. This method is only applicable to the case where the output is connected to the inverter. When the single voltage loop is controlled, the current here is a sine wave of the inverter frequency. When the voltage and current are double-loop controlled, the current waveform here is the square wave of the frequency of the inverter.

In an embodiment of the present invention, the input of the digital push-pull circuit is battery voltage (below 100V), and the output voltage is about 400V, which is used as the input voltage of the subsequent inverter. Belongs to low-voltage high-current input, high-voltage low-current output;

In an embodiment of the present invention, the working frequency of the digital push-pull circuit is 30 kHz to 100 kHz, and the primary and secondary sides of the transformer are a set of windings with a center tap.

In an embodiment of the present invention, the controller implements digital control functions and management functions by a DSP chip.

In an embodiment of the present invention, the driving circuit is a driving circuit of a MOSFET switching tube, and the power amplification driving circuit is composed of an isolation transformer or only PNP and NPN transistors.

In an embodiment of the present invention, the communication interface is a UART communication interface, and communication level conversion is not included in this circuit.

In the embodiment of the present invention, the associated parameter memory is an EEPROM memory chip.

The technical solution of the present invention improves the output performance index of the digital push-pull circuit, the conversion efficiency of the power supply, the temperature rise performance index, etc. on the basis of low cost, is convenient to use, and has high commercial practical value.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (6)

1. A kind of push-pull circuit of DC/DC part, it is characterized in that, described push-pull circuit comprises: A step-up transformer and a primary switch tube, a voltage doubler rectifier circuit connected to the output end of the step-up transformer and the primary switch tube, the output end of the voltage doubler rectifier circuit is respectively connected to an output filter, an energy storage circuit, and a current detection unit The output terminals of the filter and energy storage circuit are connected to the voltage/detection unit, the output terminals of the current detection unit and the voltage/detection unit are connected to the multi-signal feedback sampling unit, and the multi-signal feedback sampling unit is connected to A controller, the controller has its own memory and communication interface, and the output terminal of the controller is connected to the driver, the driver is connected to the step-up transformer and the primary switch tube, and the input terminal of the controller is also connected to the input voltage The detection unit and the auxiliary power supply are connected. 2. The push-pull circuit of the DC/DC part according to claim 1, characterized in that, the input of the digital push-pull circuit is below 100V of the battery voltage, and the output voltage is 400V, which is used as the input voltage of the subsequent inverter . 3. The push-pull circuit of the DC/DC part according to claim 1, wherein the operating frequency of the digital push-pull circuit is 30 kHz to 100 kHz, and the primary and secondary sides of the transformer are a group of windings with a center tap . 4. The push-pull circuit of the DC/DC part according to claim 1, characterized in that, the controller implements digital control and management functions by a DSP chip. 5. The push-pull circuit of the DC/DC part according to claim 1, wherein the driving circuit is a driving circuit of a MOSFET switching tube, and a power amplification driving circuit is composed of an isolation transformer or a PNP and NPN transistor. 6. The push-pull circuit of the DC/DC part according to claim 1, wherein the communication interface is a UART communication interface.

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