Switching Power Supply Startup Control via Feedback Path Switch
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Solution Overview
Problem
Existing switching power supply devices face challenges in starting a switching action from a stopped state due to inadequate initial voltage provision for the contrast voltage, leading to difficulties in initiating the switching action effectively.
Innovation Solution
A switching power supply device is configured with a main control circuit that includes a contrast voltage generation section, a PWM comparator, and a feedback path switch, which controls the feedback path switch to set an initial voltage within the variation range of the ramp voltage during a specific period, allowing the output stage circuit to perform a switching action. This configuration may also incorporate a phase compensation circuit and transition controlling circuit to optimize the initial voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the switching action is stopped to reduce power consumption, then energy efficiency is improved, but the ability to start switching action from stopped state is worsened
Solution Approach 1:
The feedback path switch is controlled to be in a specific state (off state during initial period) before the switching action is正式启动, thereby preliminarily setting up the appropriate initial voltage conditions for the contrast voltage. This preliminary action ensures that when switching from stopped state to active state, the contrast voltage has the correct initial value within the ramp voltage variation range, enabling reliable startup while maintaining energy efficiency during low load conditions.
2Reliability
If appropriate initial voltage is provided to contrast voltage, then switching action startup is improved, but circuit complexity is worsened
Solution Approach 1:
The feedback path switch utilizes the existing feedback path infrastructure to automatically provide the appropriate initial voltage to the contrast voltage during startup. By controlling the switch state (on/off) during specific periods, the system leverages its own feedback mechanism to self-establish the required initial voltage conditions without requiring external intervention or additional dedicated voltage source circuits, thus achieving reliable startup while minimizing circuit complexity.
Solution Approach 2:
The feedback path switch serves multiple functions: it controls the feedback signal path during normal operation and simultaneously provides initial voltage setting for the contrast voltage during startup from stopped state. This multi-functionality allows the same circuit element to address both operational control and startup initialization needs, avoiding the need for separate dedicated circuits and reducing overall system complexity.
Data Source
AI summary
A main control circuit includes a PWM comparator that compares a contrast voltage generated according to a feedback voltage with a ramp voltage having a periodically varying voltage value, and causes an output stage circuit to perform a switching action based on a result of the comparison in the PWM control. A feedback path switch is inserted in a feedback path for propagating a signal according to the feedback voltage to the PWM comparator. The main control circuit controls, upon switching from sleep control that stops the switching action to the PWM control, within a specific period equal to one or more periods of the PWM control, the feedback path switch off and sets a voltage within a variation range of the ramp voltage as an initial voltage for the contrast voltage to thereby start a switching action and controlling the feedback path switch on after the specific period.