Direct current output port linear discharge circuit
By using a discharge resistor voltage divider and a negative voltage module in the linear discharge circuit at the DC output port, the problems of slow voltage drop and circuit loss in the DC output converter during power-off and standby are solved, achieving stable discharge speed and low loss.
Patent Information
- Application Number
- CN202511151168.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-18
- Publication Date
- 2025-11-21
AI Technical Summary
Existing DC-DC converters exhibit slow port voltage drops during power-off and standby, and common discharge circuits are prone to burnout at high output voltages and slow discharge speeds at low voltages, resulting in common-mode interference and losses.
A linear discharge circuit with a DC output port is adopted. The discharge resistor reduces the driving voltage of the switching transistor. Combined with a negative voltage module, the discharge capability under low voltage is enhanced. The current flows through the discharge resistor to achieve steady-state discharge by controlling the switching device IGBT, MOSFET or BJT.
It achieves a constant discharge rate under different voltage conditions, avoids switching losses and common-mode interference, ensures that the voltage drops rapidly to 0V, meets safety requirements, and reduces losses.
Smart Images
Figure CN121000031A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronics technology, and more specifically to a linear discharge circuit for a DC output port. Background Technology
[0002] DC-DC converters typically include a filter capacitor on the output side to reduce output ripple. However, the presence of this capacitor causes the port voltage to drop very slowly when the device is off or in standby mode, failing to meet relevant safety regulations and potentially causing inconvenience in use. The industry standard practice is to add a bleeder circuit to the module's output port. Common bleeder circuit types include... Figure 1 , 2 As shown.
[0003] Figure 1 A resistor is connected in parallel across the filter capacitor. When the module is powered off, resistor R1 can discharge the remaining energy in capacitor C1. Figure 2 To further reduce losses, when the module is powered off, control Q1 is turned on, connecting resistor R1 in parallel across capacitor C1 for discharge. When the module is powered on, control Q1 is turned off, disconnecting resistor R1 from the capacitor. Compared to... Figure 1 The solution can reduce wear and tear during operation.
[0004] Both of the above schemes have a fast discharge speed when the output voltage is high, but the discharge resistor has a large power rating and is prone to burnout and failure, requiring a high-power discharge resistor. As the output voltage decreases, the discharge speed decreases, especially in standby mode, when the switching transistor of the front-end module of the DC-DC converter operates, generating common-film interference, which is converted into differential-mode voltage at the output terminal, continuously charging the port capacitor, making it more difficult to discharge the voltage to 0V.
[0005] To address the above problems, a circuit scheme is proposed. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a linear discharge circuit for a DC output port.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a linear discharge circuit for a DC output port, comprising a DC power supply module, a filter capacitor C1, a switching transistor Q1, a discharge resistor R1, and a driving module. One end of the filter capacitor C1 is connected to the positive terminal of the DC power supply module, and the other end is connected to the negative terminal of the DC power supply module. The drain (D) pin of the switching transistor Q1 is connected to the positive terminal of the DC power supply module. The input terminal of the discharge resistor R1 is connected to the source (S) pin of the switching transistor Q1, and the output terminal is connected to the negative terminal of the DC power supply module. One end of the driving module is connected to the gate (G) pin of the switching transistor Q1, and the other end is connected to the output terminal of the discharge resistor R1.
[0008] In one specific implementation, when the discharge circuit is in the discharge state, the drive module outputs a drive voltage, the switch Q1 is turned on, and the discharge current flows through the discharge resistor R1, generating a voltage drop across the discharge resistor R1 to reduce the actual drive voltage acting on the switch Q1.
[0009] In one specific implementation, the discharge circuit further includes a negative voltage module, the negative terminal of which is connected to the output terminal of the discharge resistor R1, and the positive terminal is connected to the negative terminal of the DC power supply module.
[0010] In one specific implementation, the switching transistor Q1 is an IGBT switch, a MOSFET switch, or a BJT controllable switching device.
[0011] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1) The discharge circuit proposed in this invention utilizes the voltage divider of the discharge resistor R1 to reduce the driving voltage of the switching transistor Q1, thereby enabling the discharge power to be borne by the switching transistor Q1 and maintaining a constant discharge current, which is novel. 2) This invention connects a negative voltage module in series with the DC port to enhance the discharge capability under low voltage, which is practical. Attached Figure Description
[0012] Figure 1 Electrical schematic diagram for the current scheme 1; Figure 2 Electrical schematic diagram for the current scheme 2; Figure 3 This is a schematic block diagram of the linear discharge circuit at the DC output port described in this invention. Figure 4 This is a voltage and current change diagram during voltage discharge of the linear discharge circuit at the DC output port described in this invention. Detailed Implementation
[0013] The following is in conjunction with the appendix Figure 3-4 The technical solution of the present invention will be further described in detail with reference to specific embodiments.
[0014] A linear discharge circuit for DC output port is used to discharge the voltage on the filter capacitor C1 at the DC output terminal of the power supply. Specifically, it includes a DC power supply module, filter capacitor C1, switching transistor Q1, discharge resistor R1, and drive module.
[0015] One end of the filter capacitor C1 is connected to the positive terminal of the DC power module, and the other end is connected to the negative terminal of the DC power module. The drain (D) pin of the switching transistor Q1 is connected to the positive terminal of the DC power module. The input terminal of the discharge resistor R1 is connected to the source (S) pin of the switching transistor Q1, and the output terminal is connected to the negative terminal of the DC power module. One end of the drive module is connected to the gate (G) pin of the switching transistor Q1, and the other end is connected to the output terminal of the discharge resistor R1.
[0016] When the discharge circuit is in discharge mode, the drive module outputs a drive voltage, turning on the switch Q1. The discharge current flows through the discharge resistor R1, creating a voltage drop across R1 to reduce the actual drive voltage on the switch Q1, thus achieving a steady state. The switch Q1 enters the amplification region, and the discharge current remains constant at (Vg-Vgsth) / R. The voltage across the discharge resistor R1 is Vg-Vgsth, which is very small, and the power consumption is (Vg-Vgsth)^2 / R, requiring minimal power. The voltage across the switch Q1, Vout-(Vg-Vgsth), withstands a relatively large power. When the controller detects that the output voltage of the DC power supply module is 0, the drive module stops transmitting waveforms.
[0017] Preferably, the discharge circuit further includes a negative voltage module, the negative terminal of which is connected to the output terminal of the discharge resistor R1, and the positive terminal is connected to the negative terminal of the DC power supply module. The negative voltage module increases the discharge capability. Specifically, when the output voltage of the DC power supply module is less than (Vg-Vgsth), the discharge current decreases, and the discharge speed slows down. Connecting a small voltage module in series with the negative terminal of the DC power supply module can raise the discharge voltage, ensuring that the discharge current remains constant and the discharge speed remains unchanged. Therefore, the discharge capability under low voltage is enhanced. Furthermore, when common-film interference causes continuous charging of the port, the output voltage is also discharged to 0V.
[0018] In this example, the switching transistor Q1 is an IGBT switch, a MOSFET switch, or a BJT controllable switching device. The discharge time and the stop discharge time can be adjusted according to the switching transistor's losses to ensure that the switching transistor does not thermally fail.
[0019] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A linear discharge circuit for a DC output port, characterized in that, The device includes a DC power supply module, a filter capacitor C1, a switching transistor Q1, a discharge resistor R1, and a drive module. One end of the filter capacitor C1 is connected to the positive terminal of the DC power supply module, and the other end is connected to the negative terminal of the DC power supply module. The drain (D) pin of the switching transistor Q1 is connected to the positive terminal of the DC power supply module. The input terminal of the discharge resistor R1 is connected to the source (S) pin of the switching transistor Q1, and the output terminal is connected to the negative terminal of the DC power supply module. One end of the drive module is connected to the gate (G) pin of the switching transistor Q1, and the other end is connected to the output terminal of the discharge resistor R1.
2. The linear discharge circuit for a DC output port according to claim 1, characterized in that, When the discharge circuit is in the discharge state, the drive module outputs the drive voltage, the switch Q1 is turned on, the discharge current flows through the discharge resistor R1, and a voltage drop is generated on the discharge resistor R1 to reduce the actual drive voltage acting on the switch Q1.
3. The linear discharge circuit for a DC output port according to claim 1, characterized in that, The discharge circuit also includes a negative voltage module, the negative terminal of which is connected to the output terminal of the discharge resistor R1, and the positive terminal is connected to the negative terminal of the DC power supply module.
4. The linear discharge circuit for a DC output port according to claim 1, characterized in that, The switching transistor Q1 is an IGBT switch, a MOSFET switch, or a BJT controllable switching device.