PWM Frequency Setting Circuit for Power Supply Startup Stability
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Solution Overview
Problem
Conventional switching power supply devices experience prolonged startup times and potential startup failures due to insufficient power supply when stabilizing switching frequency parameters, leading to instability during overload conditions.
Innovation Solution
A power supply device with a frequency setting circuit that sets the pulse width modulation (PWM) frequency higher than the minimum frequency during startup, incorporating an overload detection circuit and a soft start control mechanism to manage startup and overload conditions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the capacitance of the capacitor that smooths the VF voltage is increased to stabilize the switching frequency, then the switching frequency stability is improved, but the startup time is prolonged
Solution Approach 1:
The frequency setting circuit pre-sets the PWM frequency to a higher value during the startup phase before the capacitor is fully charged. This preliminary action allows the system to bypass the slow frequency rise that would otherwise occur with a large capacitor, thereby reducing startup time while maintaining frequency stability once the capacitor is charged.
Solution Approach 2:
The system dynamically adjusts the PWM frequency based on the charging state of the capacitor. During startup, when the capacitor voltage is low, the frequency setting circuit maintains a higher frequency. As the capacitor charges and its voltage increases, the frequency naturally rises to the normal operating frequency. This dynamic adjustment resolves the contradiction between startup speed and frequency stability.
2Adaptability or versatility
If the switching frequency is reduced during overload to droop the output current, then the overload management is improved, but the startup power supply becomes insufficient
Solution Approach 1:
The frequency setting circuit pre-sets a higher PWM frequency during startup, which ensures sufficient power supply to the load during the critical startup phase. This preliminary action prevents startup failure by guaranteeing adequate power delivery before the system enters normal operation where frequency reduction can be applied for overload management.
Solution Approach 2:
The system implements dynamic frequency control that adapts to different operating conditions. During startup, the frequency is maintained at a higher level to ensure sufficient power supply. During normal operation, when the system detects overload conditions, the frequency is reduced to droop the output current. This dynamic behavior resolves the contradiction between startup power requirements and overload management needs.
3Productivity
If the PWM frequency is set higher during startup, then the startup time is reduced, but the frequency stability during normal operation may be affected
Solution Approach 1:
The system dynamically adjusts the PWM frequency based on the capacitor voltage. During startup, when the capacitor voltage is low, the frequency setting circuit maintains a higher frequency to speed up startup. As the capacitor charges and its voltage increases, the frequency naturally transitions to the normal operating frequency. This dynamic adjustment ensures both fast startup and frequency stability during normal operation.
Solution Approach 2:
The frequency setting circuit operates in periodic phases: initially maintaining a higher frequency during startup, then transitioning to normal frequency operation once the capacitor is charged. This periodic frequency adjustment pattern allows the system to optimize for startup speed initially, then for stable operation subsequently, resolving the contradiction between these two requirements.
Data Source
AI summary
Provided is a power supply device comprising a voltage conversion portion configured to convert input voltage to output voltage by pulse width modulation, a frequency reduction circuit configured to reduce a frequency of the pulse width modulation in response to detection of an overload during normal operation of the voltage conversion portion and startup of the voltage conversion portion, and a frequency setting circuit configured to set the frequency of the pulse width modulation used when starting up the voltage conversion portion to a frequency higher than a minimum frequency corresponding to the overload. In addition, provided is a power supply control device and a power supply control method relating to the power supply device.