Switching Power Source Discharge Circuit for Fast Latch Reset
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Solution Overview
Problem
The reactivation time during latch protection operations in switching power source devices is excessively long due to the large capacitance of the capacitor, which takes a long time to discharge via the low power consumption current of the IC control block, making it difficult to reset the latch circuit and reactivate the control circuit within a short time.
Innovation Solution
A discharge circuit is introduced that receives the latch signal to forcibly discharge the capacitor, allowing the control power voltage to decrease quickly to the operation stop voltage, thereby shortening the reactivation time by discharging the capacitor before it reaches the operation stop voltage, and a comparator resets the latch circuit when the voltage drops to a predetermined threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large-capacity capacitor is used to maintain control power voltage during protection operation, then the control power voltage can be maintained without decreasing to operation stop voltage, but the reactivation time becomes excessively long due to slow discharge
Solution Approach 1:
The discharge path is segmented into two modes: normal protection mode where the capacitor discharges through the IC control block's low power consumption current, and latch protection mode where a dedicated discharge circuit provides a separate, high-current discharge path. This segmentation allows the system to maintain reliability during normal protection while enabling rapid reactivation during latch protection.
Solution Approach 2:
The discharge circuit acts as an intermediary component that bridges the capacitor and ground, providing a controlled discharge path. The circuit includes a discharge switch that can be turned on to create a low-resistance discharge path, effectively mediating between the energy storage capacitor and the load to enable rapid voltage reduction when needed.
2Loss of energy
If the capacitor discharges through the IC control block's low power consumption current, then power consumption is minimized, but the discharge time becomes excessively long
Solution Approach 1:
The discharge circuit dynamically adjusts the discharge current based on operational requirements. During normal protection operation, the discharge switch remains off, utilizing only the IC control block's low power consumption current to minimize energy loss. During latch protection operation, the discharge switch turns on, dynamically increasing the discharge current to reduce discharge time while still maintaining reasonable power consumption through controlled resistance.
3Loss of time
If a discharge circuit is added to forcibly discharge the capacitor, then reactivation time is shortened, but device complexity increases
Solution Approach 1:
The discharge circuit is designed with multi-functionality to reduce overall system complexity. The discharge switch serves dual purposes: it controls the discharge path during protection operations and can also function as part of the latch reset mechanism. The discharge circuit shares components with existing protection circuitry, such as utilizing the same control signals and integration points, thereby minimizing the increase in device complexity while achieving the goal of shortened reactivation time.
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
This configuration significantly reduces the reactivation time from the latch protection operation to less than 2 seconds, while also minimizing power consumption during standby, enhancing the efficiency and reducing power usage in switching power source devices.
Implementation Method 1
a capacitor C connected to a control power terminal VCC of the control circuit 20... charges a capacitor C... the voltage Vcc of the control power terminal VCC decreases gradually
Implementation Method 2
a discharge circuit that receives the latch signal to be turned on and discharges charges accumulated in the capacitor C
Data Source
AI summary
A switching power source device includes a switching power supply main body switching an input voltage via a switching element to obtain a predetermined DC output voltage, a control circuit performing on/off-driving of the switching element; and a capacitor connected to the control circuit to be charged by an external power supply via an activation switch circuit during activation and charged by a voltage generated in the switching power supply main body after completion of activation to supply a control power voltage to the control circuit. The control circuit further includes a latch circuit set according to a latch signal emitted when an abnormality is detected, to stop the driving of the switching element, a discharge circuit receiving the latch signal to be turned on and discharging charges accumulated in the capacitor, and a comparator resetting the latch circuit when the control power voltage decreases to an operation stop voltage.