IGBT Gate Voltage Control Circuit for Series Reliability
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Solution Overview
Problem
Existing gate voltage control circuits for IGBTs in high-voltage applications face issues with unbalanced voltages and voltage spikes, leading to inefficiencies and increased losses due to early activation of the active clamping circuit and uncontrollable gate voltage oscillations.
Innovation Solution
A gate voltage control circuit comprising an active clamping circuit, a power amplifier circuit, and a voltage control circuit that indirectly or directly controls the gate voltage of the IGBT, preventing early activation and reducing losses by managing the gate voltage within a controlled threshold, thereby improving the active clamping effect and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active clamping circuit is added to reduce voltage spikes and improve reliability of series-connected IGBTs, then the reliability is improved, but the circuit complexity and energy losses increase due to early activation and uncontrollable gate voltage oscillations
Solution Approach 1:
The patent implements a feedback control mechanism where the gate voltage is continuously monitored and regulated. The control circuit detects the gate voltage level and adjusts the driving signal to maintain it within the optimal range, preventing both early activation and over-activation. This feedback loop ensures the active clamping circuit activates only when needed (when Vce exceeds threshold) while maintaining stable operation, thus improving reliability without proportional increase in complexity
Solution Approach 2:
The patent dynamically adjusts the gate voltage parameter through controlled regulation. By changing the gate voltage from an uncontrolled state to a regulated state within specific thresholds, the system optimizes the activation timing of the active clamping circuit. This parameter control prevents premature activation and reduces unnecessary energy losses while maintaining the protective function
2Object-affected harmful factors
If the active clamping circuit is activated to reduce voltage spikes, then the voltage spike reduction is achieved, but energy losses increase due to charges being bypassed by the lower transistor
Solution Approach 1:
The patent employs dynamic control of the gate voltage rather than static activation. The control circuit continuously adjusts the gate voltage based on real-time conditions, enabling the active clamping circuit to activate precisely when voltage spikes occur and deactivate when not needed. This dynamic operation minimizes the duration of transistor conduction, reducing energy losses while maintaining effective voltage spike suppression
Solution Approach 2:
The patent implements periodic monitoring and control of the gate voltage through pulse-width modulation (PWM) technique. The control circuit applies periodic gating signals that activate the active clamping circuit only during necessary periods (when voltage exceeds threshold) and keeps it inactive during normal operation. This periodic action pattern reduces cumulative energy losses compared to continuous or early activation
3Reliability
If the gate voltage is allowed to rise uncontrollably to turn on the IGBT, then the active clamping effect is enhanced, but voltage oscillations occur between collector-emitter and gate voltages
Solution Approach 1:
The patent uses feedback control to maintain gate voltage within an optimal range rather than allowing it to rise uncontrollably. The control circuit monitors gate voltage and adjusts the driving signal to keep it between threshold values, ensuring the active clamping circuit activates reliably when needed while preventing over-activation that would cause oscillations. This feedback mechanism simultaneously achieves reliable clamping effect and voltage stability
Solution Approach 2:
The patent applies preliminary control measures by establishing predetermined gate voltage thresholds before oscillations can occur. The control circuit is configured with reference voltages that define the optimal operating range, and it takes preliminary action to prevent gate voltage from exceeding these thresholds. This preliminary control prevents the conditions that lead to voltage oscillations while maintaining sufficient gate voltage for reliable active clamping activation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution effectively controls the gate voltage with reduced losses, enhances the response speed of the active clamping circuit, and prevents oscillations of the collector-emitter and gate voltages, thereby increasing the reliability of IGBTs connected in series.
Implementation Method 1
After the collector-emitter voltage Vce exceeds the reverse breakdown voltage (clamping voltage) of all Zener diodes in the branch 1, the Zener diodes in this branch 1 are broken down, and charges are injected into the gate of IGBT
Implementation Method 2
the branch 2 responds to the slope of the collector-emitter voltage Vce of the IGBT When the collector-emitter voltage Vce rises with a certain slope, charges are injected into the gate of the IGBT through the capacitor
Data Source
AI summary
The present disclosure discloses a gate voltage control circuit of an IGBT and a control method thereof. The gate voltage control circuit of the IGBT comprises a voltage control circuit, an active clamping circuit and a power amplifier circuit. A control voltage outputted by the voltage control circuit indirectly controls a gate voltage of the IGBT, so as to achieve a better control of the gate voltage of the IGBT with a smaller loss. It may prevent the active clamping circuit from a too-early response and may increase the active clamping circuit response speed; and may avoid the voltage oscillation of the collector-emitter voltage Vce and the gate voltage Vge, and may improve the reliability of the IGBTs connected in series.